on the sieve elements of macrocystis...
TRANSCRIPT
![Page 1: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/1.jpg)
STUDIES O N THE SIEVE ELEMENTS OF MACROCYSTIS INTEGRIFOLIA BORY
M a o - L i e n S h i h
B. S c . T u n g h a i U n i v e r s i t y 1 9 7 6
THESIS SUBMITTED I N PARTIAL FULFILLMENT OF
THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
i n t h e D e p a r t m e n t
o f
B i o l o g i c a l S c i e n c e s
@ M a o - L i e n S h i h 1 9 8 2
SIMON FRASER UNIVERSITY
A p r i l 1 9 8 2
A l l r i g h t s r e s e r v e d . T h i s t h e s i s may n o t b e r e p r o d u c e d i n w h o l e o r i n p a r t , by p h o t o c o p y
o r o t h e r m e a n s , w i t h o u t p e r m i s s i o n o f t h e a u t h o r .
![Page 2: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/2.jpg)
Approval
Name : Mao-Lien Shih
Degree : Master of Science
T i t l e of Thesis: S tudies on t h e s i e v e elements of Macrocystis
i n t e g r i f o l i a Bory
Examining Commit t e e
Chairman: D r . Robert C. Brooke
- D r . L. M. Sr ivas tava , Senior Supervisor
~r ,/L': D. Druehl i /
m. W. E. Vidaver
Dr'. JL-BisSlputi-a, Professor , Botany, Universi ty of B r i t i s h Columbia
publ ic Examiner
Date approved *I IS , I r a 2
![Page 3: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/3.jpg)
PARTIAL COPYRIGHT LICENSE
I hereby g r a n t t o Simon Fraser Un ivers iPy t h e r i g h t t o lend
my t h e s i s , p r o j e c t o r extended essay ( t h e t i t l e o f which i s shown below)
t o users o f t h e Simon Fraser U n i v e r s i t y L i b ra r y , and t o make p a r t i a l o r
s i n g l e cop ies o n l y f o r such users o r i n response t o a reques t f rom t h e
l i b r a r y o f any o t h e r u n i v e r s i t y , o r o t h e r educa t iona l i n s t i t u t i o n , on
i t s own beha l f o r f o r one o f i t s users. 1 f u r t h e r agree t h a t permiss ion
f o r m u l t i p l e copy ing o f t h i s work f o r s c h o l a r l y purposes may be granted
by me o r t h e Dean o f Graduate Stud ies. I t i s understood t h a t copy ing
o r p u b l i c a t i o n o f t h i s work f o r f i n a n c i a l g a i n s h a l l n o t be a l lowed
w i t h o u t my w r i t t e n permiss ion.
T it l e o f Thes i s /Pro ject /Extended Essay
Studies on t h e s i e v e elements of Macrocystis i n t e g r i f o l i a Bory
Author: - --
( s i g n a t u r e )
Mao-Lien Shih
( name
( d a t e )
![Page 4: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/4.jpg)
ABSTRACT
The s i e v e e l e m e n t s o f M a c r o c y s t i s i n t e g r i f o l i a o c c u r
c h a r a c t e r i s t i c a l l y i n r a d i a l r o w s a t t h e p e r i p h e r y o f t h e
m e d u l l a . T h e n u m b e r o f y o u n g d i f f e r e n t i a t i n g s i e v e e l e m e n t s
s h o w s a p e a k e a r l y i n t h e y e a r , i . e . , J a n u a r y - M a r c h , a n d
d e c l i n e s p r o g r e s s i v e l y t h r o u g h summer a n d f a l l . The
d i f f e r e n t i a t i o n o f s i e v e e l e m e n t s s e e m s t o p r o c e e d e x t r e m e l y
r a p i d l y i n t h e a p i c a l p a r t o f t h e s t i p e , b e c a u s e i n t h e y o u n g e s t
i n t e r n o d e s e x a m i n e d (0 .8 -4 cm l o n g ) t h e r e w e r e a l w a y s some
s t r e t c h e d - o u t , t r u m p e t - s h a p e d , a n d c a l l o s e d n o n f u n c t i o n a l s i e v e
e l e m e n t s . The y o u n g s i e v e e l e m e n t s , w h i c h o r i g i n a t e f r o m t h e
i n n e r m o s t c o r t i c a l c e l l s , a r e r i c h i n c y t o p l a s m a n d v a r i o u s
o r g a n e l l e s , s u c h a s d i c t y o s o m e s , E R , r i b o s o m e s , m i t o c h o n d r i a ,
p l a s t i d s , a n d n u m e r o u s s m a l l v a c u o l e s . M i c r o b o d i e s ,
e l e c t r o n - o p a q u e g l o b u l e s a n d l a m e l l a r b o d i e s a r e a l s o p r e s e n t .
D u r i n g s i e v e e l e m e n t d i f f e r e n t i a t i o n , t h e n u c l e u s i n c r e a s e s
a l m o s t 2 - f o l d i n v o l u m e a n d b e c o m e s h i g h l y l o b e d ; a l s o t h e
n u c l e o l u s i n c r e a s e s i n v o l u m e a n d s h o w s g r a n u l a r a n d v a c u o l a r
a r e a s t y p i c a l o f n u c l e o l i e n g a g e d i n r i b o s o m e p r o d u c t i o n . I n
c o r t i c a l c e l l s , p l a s m o d e s m a t a a r e c o n f i n e d t o t h e p e r i p h e r a l
p r i m a r y p i t f i e l d s o n t h e c r o s s w a l l s ; by c o n t r a s t , n u m e r o u s
p l a s m o d e s m a t a a r e e v e n l y d i s t r i b u t e d o n t h e e n d w a l l s o f y o u n g
s i e v e e l e m e n t s . A s d i f f e r e n t i a t i o n p r o g r e s s e s , t h e d e n s i t y o f
p l a s m o d e s m a t a p e r u n i t a r e a d r o p s ( f r o m 1 0 0 t o 16 /urn2) .
E v e n t u a l l y , t h e d e n s i t y o f t h e s i e v e - p l a t e p o r e s i n m a t u r e s i e v e
2 p l a t e s i s a b o u t 0 .08 -0 .16 /um . H i s t o a u t o r a d i o g r a p h y s h o w s t h a t
i i i
![Page 5: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/5.jpg)
14c-labeled photoassimilates a r e transported through the mature
sieve elements. Very young sieve elements are not capable of
transporting assimilates, while old, callosed sieve elements
have apparently lost this function. T h e hyphal cells do not
appear to be involved in long-distance transport of '
photoassimilates.
![Page 6: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/6.jpg)
A C K N O W L E D G E M E N T S
I am g r e a t l y i n d e b t e d t o my s e n i o r s u p e r v i s o r , D r . L. M.
S r i v a s t a v a f o r h i s p a t i e n t g u i d a n c e a n d c o n t i n u o u s s u p p o r t
t h r o u g h my g r a d u a t e s t u d y a t S i m o n F r a s e r U n i v e r s i t y .
I am a l s o g r a t e f u l t o D r s . L. D r u e h l a n d W . V i d a v e r , b o t h
members o f my s u p e r v i s o r y c o m m i t t e e , f o r t h e i r v e r y c o n s t r u c t i v e
commen t s o n t h e c o m p l e t i o n o f t h i s t h e s i s .
My s p e c i a l t h a n k s a r e f o r D r . 3.-Y. F l o c ' h , F a c u l t e d e s
S c i e n c e s , U n i v e r s i t e d e B r e t a g n e O c c i d e n t a l e . W i t h o u t h i s
u n f a i l i n g e n t h u s i a s m , t h e s t u d y on 1 4 c l o c a l i z a t i o n w o u l d n o t
h a v e b e e n p o s s i b l e .
I w o u l d a l s o l i k e t o t h a n k M. S h i v j i , D . T r o t t e r , R . S m i t h
a n d K. L l o y d f o r t h e i r h e l p i n c o l l e c t i n g t h e p l a n t s a n d t h e
s t a f f s o f B a m f i e l d M a r i n e S t a t i o n a n d S imon F r a s e r U n i v e r s i t y
f o r t h e i r a s s i s t a n c e a n d f a c i l i t i e s .
F i n a l l y , I mus t s a y t h e w h o l e t h i n g w o u l d b e i m p o s s i b l e
w i t h o u t e v e r - l a s t i n g e n c o u r a g e m e n t a n d l o v e f r o m my p a r e n t s a n d
my h u s b a n d .
![Page 7: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/7.jpg)
TABLE O F CONTENTS A p p r o v a l ...................................................... li A b s t r a c t .................................................... i i i A c k n o w l e d g e m e n t s .............................................. v
L i s t o f T a b l e s ............................................ v i i i
L i s t o f F i g u r e s .............................................. ix ....................... L i s t o f A b b r e v i a t i o n s u s e d i n F i g u r e s x i i
A . INTRODUCTION. ............................................... 1
B e MATERIALS AND METHODS ....................me................. 7
I . P l a n t m a t e r i a l f o r t h e s t u d y o f p r o d u c t i o n a n d d e v e l o p m e n t o f s i e v e e l e m e n t s ......................... 7
I1 . L i g h t a n d e l e c t r o n m i c r o s c o p y ......................... 9
111 . 14c f e e d i n g a n d h i s t o a u t o r a d i o g r a p h y ............... 11
C o RESULTS .................................................... 1 3
I . G e n e r a l m o r p h o l o g y a n d a n a t o m y o f M a c r o c y s t i s ......................................... i n t e g r i f o l i a 1 3
I1 . P a t t e r n o f p r o d u c t i o n o f s i e v e e l e m e n t s .............. 2 0
I11 . O r i g i n o f s i e v e e l e m e n t s a n d h y p h a e ................. 2 9
I V . D i f f e r e n t i a t i o n o f s i e v e e l e m e n t s .................... 3 1
IV.1 . C y t o p l a s m i c c h a n g e s ............................ 31
L i g h t m i c r o s c o p i c o b s e r v a t i o n s ....................... 31
O b s e r v a t i o n s w i t h e l e c t r o n m i c r o s c o p e ................ 36
N u c l e u s a n d N u c l e o l u s ............................... 3 9
D i c t y o s o m e s ......................................... 42
E n d o p l a s m i c r e t i c u l u m (ER) a n d r i b o s o m e s ............. 4 5
V a c u o l e s ............................................. 4 7
![Page 8: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/8.jpg)
Mitochondria ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 8
Plastids ............................................. 4 9
Other organelles ..................................... 51 IV.2 . Development of sieve plates .................... 5 2
Observations with light microscope ................... 5 2
Observations w i t h electron microscope ................ 5 4
V . L o c a l i z a t i o n of 14c-labeled assimilates i n s i e v e elements by histoautoradiography ..................... 5 7
D . D I S C U S S I O N ................................................. 6 5
E . REFERENCES ................................................ 7 9
vii
![Page 9: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/9.jpg)
LIST OF T A B L E S
.. T a b l e I . M a c r o c y s t i s i n t e g r i f o l i a C o l l e c t i o n da t a . . . . . . . . . . 8
T a b l e 11. D i a m e t e r s o f s t i p e a n d m e d u l l a o f A a n d B p o i n t s f r o m e a c h s a m p l e d M a c r o c y s t i s frond.......................... 21
T a b l e 111. Number o f r a d i a l r o w s o f s i e v e e l e m e n t s i n a g i v e n c r o s s s e c t i o n o f m e d u l l a a t A a n d B of r a n d o m l y s e l e c t e d collections.............................................. 2 3
T a b l e I V . Mean w i d t h s a t c r o s s w a l l s o f i n n e r c o r t i c a l c e l l s ( C ) and d i f f e r e n t s t a g e s o f s i e v e e l e m e n t s (S1 - S 4 ) c o m p a r e d a t two l e v e l s : A vs. B f r o m e a c h c o l l e c t i o n . . . . . . . . . . . . . . . . . 26
T a b l e V . Hean l e n g t h s o f d i f f e r e n t s t a g e s o f s i e v e e l e m e n t s (S1 - S4) and i n n e r c o r t i c a l c e l l s (c) f r o m e a c h c o l l e c t i o n i n A a n d B i n t e rnodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 7
T a b l e V I . D i a m e t e r s o f n u c l e i (N) a n d n u c l e o l i (Nu) i n d i f f e r e n t s t a g e s o f young s i e v e e l e m e n t s ( ~ 1 - S 3 ) a n d i n i n n e r c o r t i c a l c e l l s (C)..................... ............- 3 4
v i i i
![Page 10: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/10.jpg)
LIST OF F I G U R E S
F i g . 1 . M a c r o c y s t i s i n t e g r i f o l i a p l a n t s h o w i n g t h e g e n e r a l m o r p h o l o g y o f t h e f r o n d a n d t h e s a m p l i n g a r ea s . . . . . . . . . . . 1 4
F i g . 2 . A p i c a l i n t e r n o d e , c r o s s s e c t i o n , s h o w i n g m e r i s t o d e r m , o u t e r c o r t e x a n d i n n e r c o r t e x , a n d medu l l a . . . . . . . . . . . . . . . 1 5
F i g . 3 . A p i c a l i n t e r n o d e , n e a r l y r a d i a l l o n g i t u d i n a l s e c t i o n t h r o u g h A c o r r e s p o n d i n g t o F i g . 2........................ 1 5
F i g . 4 . P a r a d e r m a l t a n g e n t i a l s e c t i o n t h r o u g h t h e f r i n g e o f t h e medulla.................................................. 1 7
F i g . 5 . A c o m p o s i t e o f r a d i a l l o n g i t u d i n a l s e c t i o n s t h r o u g h A s h o w i n g t h e d i f f e r e n t s t a g e s o f s i e v e e l e m e n t differentiation.................................... 1 8
F i g . 6 . C r o s s s e c t i o n t h r o u g h t h e b a s a l p a r t o f t h e s t i p e ( B l . 1 9
F i g . 7 . R a d i a l l o n g i t u d i n a l s e c t i o n t h r o u g h B s h o w i n g m a t u r e s i e v e elements.......................................... 1 9
F i g . 8 . L o n g i t u d i n a l s e c t i o n t h r o u g h B s h o w i n g i m m a t u r e s i e v e elements................................................. 1 9
F i g . 9 . H i s t o g r a m s o f c e l l d e p t h o f s i e v e e l e m e n t s i n r a d i a l r ows a t t h e o u t e r r e g i o n o f t h e m e d u l l a a t A a n d B.. . . . . . 2 4
F i g . 10 . P a t t e r n o f p r o d u c t i o n o f y o u n g s i e v e e l e m e n t s a t A a n d B i n d i f f e r e n t months. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 5
F i g . 1 1 . C r o s s s e c t i o n o f a p o r t i o n o f a m e d u l l a t h r o u g h A. . . 3 2
F i g . 1 2 . S u r f a c e v i e w t h r o u g h a c r o s s w a l l o f a c o r t i c a l c e l l s h o w i n g c i r c u l a r p r i m a r y p i t f i e l d s i n a p e r i p h e r a l r i n g fashion.................................................. 3 2
F i g . 1 3 . C r o s s s e c t i o n o f a p o r t i o n o f a m e d u l l a t h r o u g h B s h o w i n g p a r t s o f t w o m a t u r e s i e v e p l a t e s . . . . . . . . . . . . . . . . . 3 2
F i g . 1 4 . H i g h e r m a g n i f i c a t i o n o f o n e o f t h e m a t u r e s i e v e p l a t e s shown i n F i g . 14......................................... 3 2
F i g . 15. M o n t a g e o f p a r t o f a n S 1 s i e v e e l emen t . . . . . . . . . . . . . . 3 7
F i g . 1 6 . A n u c l e u s o f a n i n n e r c o r t i c a l c e l l ................ 3 8
![Page 11: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/11.jpg)
F i g . 1 7 . A n u c l e u s o f a n S 1 s i e v e e lement . . . . . . . . . . . . . . . . . . . . 3 8
F i g . 1 8 . M o n t a g e o f p a r t o f a n S 2 s i e v e e l emen t . . . . . . . . . . . . . . 4 0
F i g . 1 9 . A s t a c k o f d i c t y o s o m e s h o w i n g a n i n t i m a t e r e l a t i o n s h i p w i t h a n S2 n u c l e u s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3
F i g . 20 . S u r f a c e p a r a l l e l s e c t i o n t h r o u g h p a r t o f a n S2 n u c l e u s . 4 3
F i g . 2 1 . A h i g h l y l o b e d n u c l e u s i n t h e l a t e S2 s t a g e . I n s e t s h o w i n g a n e n l a r g e d p o r t i o n o f t h e n u c l e o l u s . . . . . . . . . . . . . 4 3
F i g . 2 2 . P o r t i o n o f a l o b e d S 3 n u c l e u s . . . . . . . . . . . . . . . . . . . . . . . 44
F i g . 23 . L o n g i t u d i n a l s e c t i o n o f p a r t o f a n e l o n g a t e d d e g e n e r a t i n g n u c l e u s i n t h e l a t e S 3 s t a g e . . . . . . . . . . . . . . . . 44
F i g . 24 . H i g h m a g n i f i c a t i o n o f p o r t i o n o f t h e n u c l e a r e n v e l o p e i n F i g . 22................................;............ 44
F i g . 25 . P a r t o f a d e g e n e r a t i n g S 3 n u c l e u s s h o w i n g a f e w d i s o r g a n i z e d d i c t y o s o m e l a m e l l a e o u t s i d e t h e n u c l e a r e n v e l o p e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
F i g . 26 . S u r f a c e p a r a l l e l s e c t i o n t h r o u g h t h e i n t e r f a c e b e t w e e n t h e p l a s m a l e m m a a n d t h e i n n e r m o s t w a l l l a y e r o f a n S 3 s i e v e element.................................................. 46
F i g . 27 . L o n g i t u d i n a l s e c t i o n o f t w o S 3 s i e v e e l e m e n t s s h o w i n g a f u t u r e p o r e s i te . ' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
F i g . 28 . C r o s s s e c t i o n o f a n S 4 s i e v e e l e m e n t s h o w i n g p a r i e t a l c y t o p l a s m i c o r g a n e l l e s a n d s e c o n d a r y c e l l w a l l . . . . . . . . . . . 46
F i g . 29 . L o n g i t u d i n a l s e c t i o n o f t w o S 1 s i e v e e l e m e n t s ....... 5 0 I
F i g . 3 0 . M i t o c h o n d r i a i n a n S 2 s i e v e e l emen t . . . . . . . . . . . . . . . . . 5 0
F i g . 3 1 . A t y p i c a l l e n s - s h a p e d p l a s t i d i n a n S 1 s i e v e element.................................................. 5 0
F i g . 3 2 . An e l o n g a t e d p l a s t i d i n S3.......................... 5 0
F i g . 33. An e n l a r g e d l a m e l l a r body. . . . . . . . . . . . . . . . . . . . . . . . ... 5 0
F i g . 3 4 . C r o s s w a l l o f t w o n e i g h b o r i n g i n n e r c o r t i c a l c e l l s . . 5 6
F i g . 3 5 . C r o s s w a l l b e t w e e n t w o S 1 s i e v e e l e m e n t s ............ 56
X
![Page 12: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/12.jpg)
F i g . 3 6 . C r o s s w a l l b e t w e e n tw,o S 2 s i e v e e l e m e n t s . ,. . . . . . . . . . . 5 6
F i g . 3 7 . L o n g i t u d i n a l s e c t i o n o f c r o s s w a l l o f S 3 s h o w i n g t h r e e f u t u r e p o r e s i tes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 8
F i g . 3 8 . L o n g i t u d i n a l s e c t i o n o f a s i e v e p l a t e o f S4.. . . . . . . . 5 8
F i g . 3 9 . O b l i q u e s e c t i o n t h r o u g h a p i t f i e l d o f a n i n n e r c o r t i c a l c e l l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 9
F i g . 40 . O b l i q u e s u r f a c e s e c t i o n t h r o u g h a n e n d w a l l o f S2.. . 5 9
F i g . 4 1 . S u r f a c e p a r a l l e l s e c t i o n t h r o u g h a n e n d w a l l o f S3. . 5 9
F i g . 4 2 . S u r f a c e v i e w of a s i e v e p l a t e o f S4. . . . . . . . . . . . . . . . . 5 9
F i g . 43 . P r o f i l e o f 1 4 c r a d i o a c t i v i t y i n a s t i p e s e g m e n t 2 0 cm a b o v e a n d b e l o w t h e l a b e l e d b l a d e i n a f r o n d o f M a c r o c y s t i s i n t e g r i f o l i a . . . .......................................... 6 0
F i g . 4 4 . G e n e r a l v i e w of t h e s t i p e 3 cm b e l o w t h e 1 4 c - l a b e l e d b l a d e s h o w n i n F i g . 43................................... 6 1
F i g . 45 . H i s t o a u t o r a d i o g r a p h s h o w i n g a p o r t i o n o f a m e d u l l a i n c r o s s secti~n...........................~................ 6 2
F i g . 46 . H i s t o a u t o r a d i o g r a p h s h o w i n g t h e o u t e r r e g i o n o f t h e m e d u l l a i n l o n g i t u d i n a l section.......................... 6 4
F i g . 47 . L o n g i t u d i n a l s e c t i o n t h r o u g h t w o f i l e s o f s i e v e e l e m e n t s s h o w i n g a c r o s s connec t ion . . . . . . . . . . . . . . . . . . . . . . 6 4
![Page 13: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/13.jpg)
LIST OF ABBREVIATIONS USED IN FIGURES
C -- c a l l o s e Ch -- c h r o m a t i n m a s s e s CW -- c r o s s w a l l D -- d i c t y o s o m e s ER -- e n d o p l a s m i c r e t i c u l u m F r -- f i b r i l l a r r e g i o n G r -- g r a n u l a r r e g i o n Hy -- h y p h a l c e l l s I C -- i n n e r c o r t e x L b -- l a m e l l a r b o d y M -- m e r i s t o d e r m Mb -- m i c r o b o d y Md -- m e d u l l a M t -- m i t o c h o n d r i a Mu -- m u c i l a g e d u c t s N -- n u c l e u s NE -- n u c l e a r e n v e l o p e Nu -- n u c l e o l u s Ob -- e l e c t r o n - o p a q u e b o d y O C -- o u t e r c o r t e x OS -- o b l i t e r a t e d s i e v e e l e m e n t s P -- p l a s t i d s Pd -- p l a s m o d e s m a t a P 1 -- p la sma lemma PS -- f u t u r e p o r e s i t e s S, SE -- s i e v e e l e m e n t s S1-S3 -- y o u n g , d i f f e r e n t i a t i n g s i e v e e l e m e n t s S4 -- m a t u r e s i e v e e l e m e n t s S p -- s i e v e p l a t e SW -- s e c o n d a r y w a l l V -- v a c u o l e s W -- c e l l w a l l
x i i
![Page 14: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/14.jpg)
A. INTRODUCTION
A l t h o u g h i t was a l m o s t a c e n t u r y a g o t h a t ' s i e v e t u b e s '
r e s e m b l i n g t h o s e o f l a n d p l a n t s were f o u n d i n M a c r o c y s t i s o f
L a m i n a r i a l e s ( W i l l , 1 8 8 4 ) , i n f o r m a t i o n c o n c e r n i n g t h e i r
o c c u r r e n c e , i n t e r n a l s t r u c t u r e , a n d s e q u e n c e o f d i f f e r e n t i a t i o n
h a s b e e n e i t h e r i n c o m p l e t e o r t o t a l l y l a c k i n g . E a r l i e r
i n v e s t i g a t o r s who f o c u s e d on t h e g e n e r a l m o r p h o l o g y a n d a n a t o m y
o f t h e t h a l l u s o f t h i s g e n u s c o n f i r m e d W i l l ' s f i n d i n g s o f s i e v e
t u b e s o c c u r r i n g a t t h e p e r i p h e r y o f t h e c e n t r a l m e d u l l a a n d
a g r e e d t h a t t h e s e c e l l s a r o s e b y t r a n s f o r m a t i o n o f t h e i n n e r
c o r t i c a l c e l l s ( O l i v e r , 1 8 8 7 ; R o s e n t h a l , 1 8 9 0 ; S y k e s , 1 9 0 8 ;
S m i t h , 1 9 3 9 ) . H o w e v e r , d i f f e r e n t o p i n i o n s w e r e e x p r e s s e d o n
w h e t h e r s i e v e t u b e s c o u l d b e p r o d u c e d i n d e f i n i t e l y f r o m t h e
c o r t i c a l c e l l s o r i f o n l y a l i m i t e d number o f t h e c o r t i c a l c e l l s
w e r e d e s t i n e d t o become s i e v e e l e m e n t s ( W i l l , 1 8 8 4 ; R o s e n t h a l ,
1 8 9 0 ) . I n o t h e r w o r d s , i t i s n o t known f o r e x a m p l e , w h e t h e r
s i e v e t u b e s a r e r e p l e n i s h e d f r o m t i m e t o t i m e o r w h e t h e r t h e y
a r e r e t a i n e d f o r t h e l i f e o f t h e f r o n d o n c e t h e y h a v e b e e n
p r o d u c e d , a s i n some p a l m s ( P a r t h a s a r a t h y a n d T o m l i n s o n , 1 9 6 7 ) .
I n a d d i t i o n t o t h e p e r i m e d u l l a r y s i e v e t u b e s , l o n g s t r a n d s
o f c e l l s , t r u m p e t - s h a p e d a t t h e i r j u n c t i o n s , w e r e f o u n d i n t h e
c e n t e r o f t h e m e d u l l a a n d w e r e c a l l e d ' t r u m p e t h y p h a e ' by O l i v e r
( 1 8 8 7 ) . I n t h e m e a n t i m e , O l i v e r r e g a r d e d t h o s e p e r i m e d u l l a r y
s i e v e e l e m e n t s a s l t r u e s i e v e t u b e s ' a n d s u g g e s t e d t h a t t h e s e
![Page 15: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/15.jpg)
c e l l s a n d t r u m p e t h y p h a e w e r e o f d i f f e r e n t o r i g i n . S y k e s ( 1 9 0 8 )
l a t e r r e v i e w e d t h e o n t o g e n e t i c d e v e l o p m e n t o f t h e s e c e l l s i n t h e
same s p e c i e s a n d i n d i c a t e d t h a t t h e y w e r e h o m o l o g o u s b u t
d i f f e r e d i n d e g r e e o f d i f f e r e n t i a t i o n . S i e v e t u b e s w e r e a l s o
d e s c r i b e d i n N e r e o c y s t i s ( O l i v e r , 1 8 8 7 ; S m i t h , 1 9 3 9 ) . T r u m p e t
h y p h a e i n L a m i n a r i a s p e c i e s w e r e n o t r e g a r d e d t o b e t h e same a s
t h e s i e v e t u b e s o f M a c r o c y s t i s o r N e r e o c y s t i s ; d i f f e r e n t t e r m s
w e r e u s e d t o d e s c r i b e t h e m , e . g . , p i t h f i l a m e n t ( ~ y k e s , 1 9 0 8 1 ,
t r u m p e t f i l a m e n t ( S m i t h , 1 9 3 9 ) , and s i e v e h y p h a e ( ~ s a u e t a l , -- 1 9 5 3 ; s e e a l s o d i s c u s s i o n by E s a u , 1 9 6 9 ) . More r e c e n t l y , S c h m i t z
a n d S r i v a s t a v a ( 1 9 7 4 b ) showed t h a t L a m i n a r i a h a s s i e v e e l e m e n t s
a s e v i d e n c e d by t h e p r e s e n c e o f s i e v e a r e a s w i t h e v e n l y
d i s t r i b u t e d p o r e s . A s s i e v e h y p h a e , p i t h f i l a m e n t e t c . a r e
a c t u a l l y a l l t h e same t y p e o f c e l l s ( - - t h e s i e v e e l e m e n t s ) ,
S c h m i t z a n d S r i v a s t a v a ( 1 9 7 4 6 ) s u g g e s t e d t h a t t h e t e r m ' s i e v e
e l e m e n t ' b e u s e d , f o r n e i t h e r ' s i e v e c e l l ' n o r ' s i e v e - t u b e
member ' w a s a p p r o p r i a t e ( f o r d e f i n i t i o n s e e E s a u , 1 9 6 5 ) . F o r t h e
same r e a s o n , I s h a l l u s e t h e t e r m ' s i e v e e l e m e n t ' t h r o u g h o u t
t h i s t h e s i s .
The o c c u r r e n c e o f s i e v e e l e m e n t s i n M a c r o c v s t i s i n
c o n j u n c t i o n w i t h t h e h i g h l y d i f f e r e n t i a t e d p l a n t f o r m ( a g e n e r a l
d e s c r i p t i o n o f - M. i n t e g r i f o l i a i s g i v e n i n P a r t C - I ) l e d W i l l e
( 1 8 8 5 ) t o s u g g e s t t h a t t h e s e c e l l s w e r e i n v o l v e d i n c o n d u c t i o n .
A l t h o u g h a h i g h r a t e o f e x u d a t i o n f r o m t h e s t i p e o f - M. p y r i f e r a
was r e c o r d e d ( C r a f t , 1 9 3 9 ) , t h e f i r s t e v i d e n c e , t h o u g h i n d i r e c t ,
o f l o n g - d i s t a n c e t r a n s p o r t o f o r g a n i c s u b s t a n c e s i n t h i s p l a n t
![Page 16: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/16.jpg)
was p r o v i d e d by S a r g e n t a n d L a n t r i p ( 1 9 5 2 ) . T h e y f o u n d t h a t t h e
i n c r e a s e o f d r y m a t t e r i n y o u n g b l a d e s f a r e x c e e d e d t h e n e t
p r o d u c t i o n o f p h o t o a s s i m i l a t e s by t h e s e b l a d e s ; t h e m a t u r e
b l a d e s , by c o n t r a s t , showed a s u r p l u s o f p h o t o s y n t h a t e s w h i c h
m i g h t b e t r a n s p o r t e d t h r o u g h t h e s t i p e t o t h e y o u n g e r b l a d e s ,
t h u s p r o v i d i n g f o r t h e i r g r o w t h . T h i s i n f e r e n c e was l a t e r
s u b s t a n t i a t e d b y P a r k e r ( 1 9 6 3 , 1 9 6 5 ) w i t h u s e o f 1 4 c . P a r k e r
( 1 9 6 5 ) r e p o r t e d a r e l a t i v e l y h i g h v e l o c i t y o f t r a n s l o c a t i o n o f
1 4 c - l a b e l e d p h o t o a s s i m i l a t e s , u p t o 78 c m l h , f o r - M. p y r i f e r a a n d
f u r t h e r i d e n t i f i e d t h e m a i n t r a n s l o c a t e a s r n a n n i t o l ( P a r k e r ,
1 9 6 6 ) . W i t h t h i s p o w e r f u l t o o l o f r a d i o i s o t o p e s a t h a n d , more
i n v e s t i g a t o r s became i n t e r e s t e d i n t h e p h y s i o l o g i c a l a s p e c t s o f
t r a n s l o c a t i o n i n t h e L a m i n a r i a l e s . L o n g - d i s t a n c e t r a n s p o r t o f
p h o t o a s s i m i l a t e s w a s a l s o s h o w n t o o c c u r i n N e r e o c y s t i s ,
L a m i n a r i a , a n d A l a r i a ( N i c h o l s o n a n d B r i g g s , 1 9 7 2 ; L u n i n g -- e t a l ,
1 9 7 3 ; S c h m i t z a n d S r i v a s t a v a , 1 9 7 5 ) . More r e c e n t l y , a s u r v e y o f
1 3 g e n e r a , 1 4 s p e c i e s i n t o t a l , of L a m i n a r i a l e s s u g g e s t s t h a t
t h e phenomenon o f t r a n s l o c a t i o n i s a g e n e r a l f e a t u r e o f t h e
L a m i n a r i a l e s ( S c h m i t z a n d L o b b a n , 1 9 7 6 ) .
The d i r e c t e v i d e n c e o f s i e v e e l e m e n t s b e i n g i n v o l v e d i n t h e
t r a n s l o c a t i o n o f 1 4 c - l a b e l e d a s s i m i l a t e s was o b t a i n e d by means
o f h i s t o a u t o r a d i o g r a p h y i n - L . h y p e r b o r e a ( S t e i n b i s s a n d S c h m i t z , . *
1 9 7 3 ) . S o o n a f t e r , S c h m i t z a n d S r i v a s t a v a ( 1 9 7 4 b ) p u b l i s h e d a
l u c i d p a p e r o n t h e d i f f e r e n t i a t i o n a n d f i n e s t r u c t u r e o f s i e v e
e l e m e n t s i n - L. g r o e n l a n d i c a . The s i e v e e l e m e n t s i n - L.
g r o e n l a n d i c a p o s s e s s s i e v e a r e a s w i t h r a t h e r s m a l l p o r e s ( c a .
![Page 17: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/17.jpg)
0 .04 -0 .06 urn i n d i a m e t e r ) on t h e i r e n d w a l l s . H o w e v e r , u n l i k e
s i e v e e l e m e n t s o f h i g h e r p l a n t s ( ~ r i v a s t a v a , 1 9 7 5 ) i n w h i c h t h e
c o m p l e t i o n o f s i e v e e l e m e n t d i f f e r e n t i a t i o n i s a c c o m p a n i e d b y
s e l e c t i v e d e g r a d a t i o n o f t h e p r o t o p l a s t , m o s t o f t h e o r g a n e l l e s
s u c h a s n u c l e u s , e n d o p l a s m i c r e t i c u l u m (ER), r i b o s o m e s , and
d i c t y o s o m e s e t c . a r e r e t a i n e d , t h o u g h m o d i f i e d , and t h e r e a r e
n u m e r o u s s m a l l v a c u o l e s ( S c h m i t z a n d S r i v a s t a v a , 1 9 9 4 b ; S i d e m a n
a n d S c h e i r e r , 1 9 7 7 ) . The f i n e s t r u c t u r e o f s i e v e e l e m e n t s o f
A l a r i a a n d N e r e o c y s t i s h a s a l s o b e e n s t u d i e d by S c h m i t z a n d -
S r i v a s t a v a ( 1 9 7 5 , 1 9 7 6 ) . A h i g h l y v a c u o l a t e d s y s t e m s e e m s t o b e
c h a r a c t e r i s t i c o f t h e s i e v e e l e m e n t s o f a l l t h r e e g e n e r a o f
L a m i n a r i a l e s m e n t i o n e d a b o v e .
L a t e l y , a s e r i e s o f i n v e s t i g a t i o n s o n t h e p h y s i o l o g y of
t r a n s l o c a t i o n h a s b e e n c a r r i e d o u t o n M a c r o c y s t i s s p e c i e s
( ~ o b b a n , 1 9 7 8 a , b , c ; S c h m i t z a n d S r i v a s t a v a , 1 9 7 9 a , b ; 1 9 8 0 ) .
I n b r i e f , t h e p a t t e r n o f t r a n s l o c a t i o n o f p h o t o a s s i m i l a t e s i s
s i m i l a r i n M. p y - r i f e r a a n d - M. i n t e g r i f o l i a . Movement o f 1 4 c
l a b e l s h o w s a s o u r c e - t o - s i n k r e l a t i o n s h i p . T h e d i r e c t i o n o f
movement o f p h o t o a s s i m i l a t e s , a c r o p e t a l , b a s i p e t a l o r
b i d i r e c t i o n a l , i s g e n e r a l l y d e t e r m i n e d b y t h e d i s t a n c e a n d
r e l a t i v e o r i e n t a t i o n b e t w e e n t h e s o u r c e a n d s i n k . I f t h e m a t u r e
f e d b l a d e i s c l o s e r t o t h e f r o n d a p e x , t r a n s p o r t o f 1 4 c l a b e l i s
m o s t l y a c r o p e t a l ; c o n v e r s e l y , i f t h e m a t u r e b l a d e i s c l o s e r t o
t h e h o l d f a s t , t r a n s p o r t i s m o s t l y b a s i p e t a l . T h i s p a t t e r n o f
t r a n s l o c a t i o n c h a n g e s s e a s o n a l l y i n M. i n t e g r i f o l i a b u t s h o w s no - s e a s o n a l i t y i n - M. p y r i f e r a ( L o b b a n , 1 9 7 8 a , b ) . The v e l o c i t y of
![Page 18: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/18.jpg)
t r a n s l o c a t i o n o f o r g a n i c c a r b o n w a s i n t h e r a n g e o f 3 5 - 7 2 c m l h
f o r - M. i n t e g r i f o l i a ( S c h m i t z a n d S r i v a s t a v a , 1 9 7 9 a ) , w h i c h i s
c o m p a r a b l e t o t h a t f o r - M. p y r i f e r a ( P a r k e r , 1 9 6 5 ) . T h e m a i n
t r a n s l o c a t e s a r e m a n n i t o l a n d a m i n o a c i d s i n a r o u g h l y 1 : 1
r a t i o . T h e s e a u t h o r s a l s o p r o v i d e d a h i s t o a u t o r a d i o g r a p h o f a
c r o s s s e c t i o n o f t h e m e d u l l a o f - M . i n t e g r i f o l i a s h o w i n g t h a t 1 4 c
l a b e l w a s l o c a t e d e x c l u s i v e l y i n t h e m e d u l l a ( S c h m i t z a n d
S r i v a s t a v a , 1 9 7 9 b ) . N e v e r t h e l e s s , i t i s n o t c l e a r w h e t h e r s i e v e
e l e m e n t s a r e t h e p r i n c i p a l o r t h e o n l y c o n d u i t s o f t r a n s l o c a t i o n
o f a s s i m i l a t e s .
The u l t r a s t r u c t u r e o f s i e v e e l e m e n t s o f - M. p y r i f e r a h a s
b e e n s t u d i e d by s e v e r a l a u t h o r s ( P a r k e r a n d P h i l p o t t , 1 9 6 1 ;
Z i e g l e r , 1 9 6 3 ; P a r k e r a n d H u b e r , 1 9 6 5 ) . B e c a u s e o f p o o r f i x a t i o n
i n t h e s e e a r l y s t u d i e s , t h e r e s u l t s a r e h a r d t o i n t e r p r e t a n d
i n c o n c l u s i v e . P a r k e r a n d P h i l p o t t ( 1 9 6 1 ) d e s c r i b e d a s i e v e p l a t e
o f a s i e v e e l e m e n t t r a v e r s e d b y t h i n c y t o p l a s m i c t h r e a d s a b o u t
0 .03 -0 .05 um i n d i a m e t e r . Z i e g l e r ( 1 9 6 3 ) , h o w e v e r , m e a s u r e d
s i e v e - p l a t e p o r e s a b o u t 1 um i n d i a m e t e r , a n d t h o u g h t t h a t t h e
s i e v e p l a t e d e s c r i b e d by P a r k e r a n d P h i l p o t t ( 1 9 6 1 ) m i g h t h a v e
b e e n a p i t f i e l d . P a r k e r a n d H u b e r ( 1 9 6 5 ) s t u d i e d t h e m a t u r e
s i e v e e l e m e n t s i n t h e same s p e c i e s a n d r e c o g n i z e d m i t o c h o n d r i a ,
o c c a s i o n a l d i c t y o s o m e s , a n d p l a s t i d s . N u c l e i w e r e a b s e n t . They
a l s o d e s c r i b e d a v e r y d e n s e s u b s t a n c e o n t h e s i e v e p l a t e s a n d
i n t e r p r e t e d i t a s s l i m e , now r e f e r r e d t o a s P - p r o t e i n ( E s a u a n d
C r o n s h a w , 1 9 6 7 ) . D e s p i t e t h e p a p e r s r e v i e w e d a b o v e , t h e r e i s
s t i l l v e r y l i t t l e p u b l i s h e d i n f o r m a t i o n o n t h e d e v e l o p m e n t a n d
![Page 19: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/19.jpg)
f i n e s t r u c t u r e o f s i e v e e l e m e n t s i n M a c r o c y s t i s a n d ,
f u r t h e r m o r e , c h a n g e s i n s i e v e e l e m e n t n u c l e a r s t r u c t u r e a n d t h e
p e r f o r a t i o n o f s i e v e p l a t e s a r e t o p i c s o f w h i c h v i r t u a l l y
n o t h i n g i s known.
T h i s t h e s i s a t t e m p t s t o p r o v i d e some i n f o r m a t i o n o n t h e
g r o w t h p a t t e r n o f s i e v e e l e m e n t s , a n d o n t h e d i f f e r e n t i a t i o n a n d
i n t e r n a l s t r u c t u r e o f y o u n g a n d m a t u r e s i e v e e l e m e n t s i n M. - i n t e g r i f o l i a . D u r i n g t h e s t r u c t u r a l s p e c i a l i z a t i o n o f t h e s i e v e
e l e m e n t s , t h e n u c l e a r c h a n g e s a n d t h e p e r f o r a t i o n o f s i e v e
p l a t e s a r e e m p h a s i z e d . F i n a l l y , 14c h i s t o a u t o r a d i o g r a p h y was
u s e d t o d e t e r m i n e w h i c h s i e v e e l e m e n t s a r e i n d e e d i n v o l v e d i n
t r a n s l o c a t i o n a n d a t w h a t s t a g e i n t h e i r d i f f e r e n t i a t i o n t h e y
s t a r t f u n c t i o n i n g .
![Page 20: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/20.jpg)
B. MATERIALS AND METHODS
I. P l a n t m a t e r i a l f o r t h e s t u d y o f p r o d u c t i o n a n d d e v e l o p m e n t o f
s i e v e e l e m e n t s
P l a n t s o f - M . i n t e g r i f o l i a B o r y w e r e c o l l e c t e d f r o m t h e k e l p
b e d s n e a r B a m f i e l d i n B a r k l e y S o u n d , V a n c o u v e r I s l a n d , B r i t i s h
C o l u m b i a . Y e a r - r o u n d c o l l e c t i o n o n a m o n t h l y b a s i s s t a r t e d i n
May 1 9 7 8 a n d c o n t i n u e d t o M a r c h 1 9 7 9 . S a m p l e c o l l e c t i o n was
s k i p p e d i n O c t o b e r a n d D e c e m b e r o f 1 9 7 8 a n d i n A p r i l o f 1 9 7 9 .
S a m p l i n g s w e r e made a g a i n i n S e p t e m b e r 1 9 7 9 a n d i n J a n u a r y
t h r o u g h M a r c h , 1 9 8 0 . I n May 1 9 8 0 , m o r e M a c r o c y s t i s p l a n t s w e r e
c o l l e c t e d a n d u s e d f o r 1 4 c - f e e d i n g e x p e r i m e n t s .
M o s t l y f r o n d s 300 -400 cm l o n g w e r e s a m p l e d . H o w e v e r , when
t h e d e s i r e d l e n g t h s w e r e n o t a v a i l a b l e a s e . g . , i n w i n t e r m o n t h s
N o v e m b e r - J a n u a r y , f r o n d s u p t o 7 0 0 c m l o n g w e r e u s e d . S o m e t i m e s ,
y o u n g f r o n d s l e s s t h a n 1 0 0 cm l o n g w e r e a l s o c o l l e c t e d . The
d e t a i l s o f t h e m a t e r i a l s c o l l e c t e d a r e l i s t e d i n T a b l e I . I n
a d d i t i o n t o t h e l e n g t h o f a f r o n d , t h e l e n g t h s o f i n d i v i d u a l
i n t e r n o d e s w e r e a l s o r e c o r d e d . F o r t h e s t u d y o f t h e p r o d u c t i o n
of s i e v e e l e m e n t s , t w o e x t r e m e i n t e r n o d e s o f a g i v e n f r o n d ,
i . e . , t h e f i r s t i n t e r n o d e b e l o w t h e a p i c a l s c i m i t a r ( d e s i g n a t e d
a s ' a p i c a l i n t e r n o d e o r A p o i n t ) a n d t h e l o n g e s t i n t e r n o d e ,
u s u a l l y t h e t h i r d o r t h e f o u r t h i n t e r n o d e a b o v e t h e h o l d f a s t
![Page 21: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/21.jpg)
Tab le I. Macrocys t i s i n t e g r i f o l i a -- C o l l e c t i o n Data.
Fronds were c o l l e c t e d f rom k e l p beds near Bamfield,
Vancouver I s land , B. C . d u r i n g 1978-1980.
C o l l e c t i o n Frond Length In ternode Examined C o l l e c t i o n
Date ( c d Ap ica l (A) Basal (B) S i t e
( l eng th , cm)
1978
May 30
June 29
J u l y 31
Aug. 30
Sep. 29
Nov. 22
1979
Jan. 27
Mar. 3
Mar. 24
Sep. 28
1980
Jan. 13
Feb. 3
S c o t t ' s Bay I I
I I
I I
I I
I I
Grappler I n l e t
A g u i l a r P t .
Grappler I n .
Mar. 10 284 2.0 25.0 A g u i l a r P t .
![Page 22: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/22.jpg)
( d e s i g n a t e d a s b a s a l i n t e r n o d e o r B p o i n t ) , were t a k e n . T h e
a p i c a l i n t e r n o d e a s w e l l a s t h e y o u n g f r o n d s , a s i s s h o w n l a t e % ,
p r o v e d t o b e e x c e l l e n t m a t e r i a l f o r t h e s t u d y o f t h e d e v e l o p m e n t
o f s i e v e e l e m e n t s ( s e e R e s u l t s ) .
11. L i g h t a n d e l e c t r o n m i c r o s c o p y
S m a l l t i s s u e s a m p l e s o f t h e s t i p e , a t b o t h A a n d B p o i n t s ,
a n d a l s o o f t h e i n t e r m e d i a t e i n t e r n o d e s w e r e f i x e d i n 2%
g l u t a r a l d e h y d e i n a b u f f e r s o l u t i o n o f 1 p a r t 0 . 1 M s o d i u m
c a c o d y l a t e : 3 p a r t s s e a w a t e r ( v : v ) a n d 0 .01% CaC12 ( v : w ) ,
pH 7 . 2 , ( a d a p t e d f r o m S c h m i t z a n d S r i v a s t a v a , 1 9 7 4 b ) f o r t h e
f i r s t 4 h a t 1 1 " C t h e n t h e n e x t 2 0 h a t 4 O C . The m a t e r i a l was
w a s h e d i n t h e s e a w a t e r - b u f f e r , CaC12 m i x t u r e , a n d p o s t f i x e d i n
1% osmium t e t r o x i d e b u f f e r e d i n t h e same m i x t u r e f o r 2 h a t room
t e m p e r a t u r e . I t was t h e n t h o r o u g h l y w a s h e d w i t h 3-4 c h a n g e s o f
s e a w a t e r - b u f f e r , CaC12 m i x t u r e a n d d e h y d r a t e d i n a n a s c e n d i n g
s e r i e s o f e t h a n o l , w i t h 0 . 0 1 % CaC12 a d d e d u p t o t h e 70% e t h a n o l
s t a g e . F u r t h e r d e h y d r a t i o n w a s c a r r i e d o u t w i t h o u t CaC12 a n d
c o m p l e t e d w i t h s e v e r a l c h a n g e s i n p r o p y l e n e o x i d e . The s a m p l e s
w e r e embedded o v e r s e v e r a l d a y s i n S p u r r ' s l o w v i s c o s i t y r e s i n
( S p u r r , 1 9 6 9 ) .
F o r l i g h t m i c r o s c o p y 1 urn s e c t i o n s o f r e s i n - e m b e d d e d
m a t e r i a l , s t a i n e d w i t h t o l u i d i n e b l u e 0 ( ~ e d e r a n d O ' B r i e n ,
1 9 6 8 1 , w e r e u s e d . C a l l o s e w a s s t a i n e d w i t h a n i l i n e b l u e ( J e n s e n ,
![Page 23: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/23.jpg)
1 9 6 4 ) i n s e c t i o n s o f r e s i n - e m b e d d e d m a t e r i a l . C a l l o s e s t a i n i n g
was a l s o p e r f o r m e d o n t h i n h a n d - c u t s e c t i o n s o f f r e s h o r
g l u t a r a l d e h y d e - f i x e d m a t e r i a l .
To d e t e r m i n e t h e p r o d u c t i o n o f s i e v e e l e m e n t s a t a n y g i v e n
l e v e l , a n i n d i r e c t me thod was u s e d . Young , d i f f e r e n t i a t i n g s i e v e
e l e m e n t s w e r e i d e n t i f i e d b e t w e e n t h e i n n e r m o s t c o r t i c a l c e l l a n d
t h e f i r s t m a t u r e s i e v e e l e m e n t i n t h e m e d u l l a . S i n c e t h e s i e v e
e l e m e n t s g e n e r a l l y o c c u r i n r a d i a l r o w s i n t h e m e d u l l a , t h e
number o f s u c h d i f f e r e n t i a t i n g s i e v e e l e m e n t s i n e a c h r o w w a s
t a k e n a s a n i n d i c a t i o n o f p r o d u c t i o n o f new s i e v e e l e m e n t s . The
c r i t e r i o n f o r d i f f e r e n t i a t i n g s i e v e e l e m e n t s was c e l l s w h i c h
w e r e s t i l l e l o n g a t i n g , and w h i c h h a d a b u n d a n t c y t o p l a s m ,
p r o m i n e n t n u c l e i , a n d r e l a t i v e l y t h i n w a l l s , w i t h o u t t h e m a t u r e ,
p e r f o r a t e d s i e v e p l a t e s i n t h e e n d w a l l s . F i f t y r a d i a l r o w s w e r e
c o u n t e d f o r e a c h s a m p l e p o i n t . T h e r e s u l t s w e r e e x p r e s s e d a s
mean o f t h e 50 c o u n t s ( s e e P a r t C-IT).
F o r e l e c t r o n m i c r o s c o p y , u l t r a t h i n s e c t i o n s ( 6 0 - 9 0 nm) w e r e
c u t on a R e i c h a r t O M U 2 m i c r o t o m e w i t h a d i a m o n d k n i f e , p i c k e d u p
o n u n c o a t e d o r f o r m v a r - c o a t e d g r i d s , s t a i n e d w i t h u r a n y l a c e t a t e
a n d l e a d c i t r a t e a n d e x a m i n e d u n d e r a Z e i s s E M 9 A m i c r o s c o p e a t
60 k v o r a P h i l i p s E M 300G m i c r o s c o p e a t 8 0 kv .
![Page 24: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/24.jpg)
111. 14c f e e d i n g a n d h i s t o a u t o r a d i o g r a p h y
P l a n t s o f M. i n t e g r i f o l i a w e r e c o l l e c t e d i n May, 1 9 8 0 a s -
d e s c r i b e d p r e v i o u s l y . 1 4 c - f e e d i n g e x p e r i m e n t s were c ~ n d u c t e d
t h e same d a y i n l a r g e t a n k s a t t h e B a m f i e l d M a r i n e S t a t i o n ,
f o l l o w i n g t h e e x p e r i m e n t a l s e t u p d e s c r i b e d by S c h m i t z a n d
S r i v a s t a v a ( 1 9 7 9 a ) . A f u l l y e x p a n d e d b l a d e o f a f r o n d , 3 0 0 t o
4 0 0 cm l o n g , w a s e n c l o s e d i n a t r a n s p a r e n t p l a s t i c b a g w i t h 2 1
o f m i l l i p o r e - f i l t e r e d s e a w a t e r , a n d 2 . 2 m C i o f N ~ ~ ~ ~ c o ~ was
i n j e c t e d i n t o t h e b a g t h r o u g h a s e r u m c a p . The i l l u m i n a t i o n a t
t h e p l a n t s u r f a c e was 8 0 0 f t - c . T h e f e e d i n g p e r i o d was 3 h. A t
t h e e n d o f 1 4 c - f e e d i n g , a 40 cm s e g m e n t o f s t i p e , 20 cm a b o v e
a n d b e l o w t h e f e d b l a d e , w a s s a m p l e d . I t w a s q u i c k l y c u t i n t o 2
mm t h i c k s l i c e s a n d f r o z e n i n l i q u i d F r e o n p r e - c o o l e d w i t h
l i q u i d n i t r o g e n . F o r s u b s e q u e n t p r o c e s s i n g , t h e f r e e z e
s u b s t i t u t i o n m e t h o d o f S t e i n b i s s a n d S c h m i t z ( 1 9 7 3 ) was
f o l l o w e d . F r o z e n p i e c e s o f t i s s u e w e r e t r a n s f e r r e d t o a
p r e c h i l l e d m i x t u r e o f 1 0 0 % a c e t o n e a n d 1 % a c r o l e i n , a n d k e p t i n
t h a t m i x t u r e a t -60 O C f o r 2 d a y s . Two c h a n g e s o f f r e s h c o o l e d
1 0 0 % a c e t o n e were c o n d u c t e d o v e r t h e n e x t 5 d a y s . The
f r e e z e - s u b s t i t u t e d s a m p l e s w e r e b r o u g h t t o room t e m p e r a t u r e ,
embedded i n S p u r r ' s r e s i n a n d c u r e d i n a n o v e n a t 60 O C .
F o r h i s t o a u t o r a d i o g r a p h y , 8 u n s e c t i o n s w e r e o b t a i n e d u s i n g
d r y g l a s s k n i v e s a n d f l a t t e n e d w i t h 70% a c e t o n e o n t o
g e l a t i n - c o a t e d s l i d e s . T h e s e w e r e c o a t e d w i t h Kodak NTB-2
p h o t o e m u l s i o n . E x p o s u r e t i m e w a s d e t e r m i n e d e m p i r i c a l l y a n d 8
![Page 25: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/25.jpg)
d a y s was f o u n d t o be s u i t a b l e . Kodak D - 1 9 was u s e d f o r
d e v e l o p m e n t .
![Page 26: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/26.jpg)
C. RESULTS
I . G e n e r a l m o r p h o l o g y a n d a n a t o m y o f M a c r o c y s t i s i n t e g r i f o l i a
A p l a n t o f - M. i n t e g r i f o l i a h a s many f r o n d s o f v a r y i n g
s t a g e s o f g r o w t h w h i c h a r i s e f r o m a common h o l d f a s t ( ~ i g . 1 ) .
E a c h f r o n d i s composed o f a s t e m - l i k e s t i p e , many l e a f - l i k e
b l a d e s e a c h w i t h a s w o l l e n a i r b l a d d e r o r p n e u m a t o c y s t a t i t s
b a s e ( p r o x i m a l e n d ) , a n d a m e r i s t e m a t i c a p e x known a s t h e
s c i m i t a r . The s t i p e i s d i s t i n c t l y p a r t i t i o n e d i n t o n o d e s a n d
i n t e r n o d e s by t h e a t t a c h m e n t o f t h e b l a d e s w h i c h show a
u n i l a t e r a l d i s p o s i t i o n . New b l a d e s c o n t i n u e t o b e f o r m e d b y
s e p a r a t i o n o f new b l a d e t i s s u e s f r o m t h e a p i c a l s c i m i t a r . Among
t h e L a m i n a r i a l e s , p l a n t s o f M a c r o c y s t i s , t h u s , show a u n i q u e
f o r m o f a p i c a l g r o w t h , i n a d d i t i o n t o t h e more common
i n t e r c a l a r y g r o w t h t y p i c a l o f a l l L a m i n a r i a l e s .
The y o u n g e s t p a r t e x a m i n e d i n t h i s s t u d y w a s a l w a y s t h e
f i r s t i n t e r n o d e b e l o w t h e a p i c a l s c i m i t a r . I n t h i s a p i c a l
i n t e r n o d e , t h r e e d i s t i n c t t i s s u e s w e r e a l r e a d y d i f f e r e n t i a t e d ,
n a m e l y , m e r i s t o d e r m , c o r t e x , a n d m e d u l l a ( F i g s . 2 a n d 3 ) . The
b l a d e a n d h o l d f a s t were n o t e x a m i n e d i n t h i s s t u d y ; b u t i t i s
known f r o m t h e l i t e r a t u r e a n d s t u d i e s o n o t h e r L a m i n a r i a l e s t h a t
t h e b a s i c t i s s u e t o p o g r a p h y i s t h e s ame a s t h a t o f t h e s t i p e
e x c e p t t h a t t h e h o l d f a s t d o e s n o t h a v e a w e l l - d i f f e r e n t i a t e d
![Page 27: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/27.jpg)
F i g . 1 . M a c r o c y s t i s i n t e g r i f o l i a p l a n t showing t h e g e n e r a l morphology o f t h e f r o n d and t h e s a m p l i n g a r e a s : ( A ) , t h e a p i c a l i n t e r n o d e ; ( B ) , t h e l o n g e s t b a s a l i n t e r n o d e .
![Page 28: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/28.jpg)
spovophyl I
holdf ast
V haptera
![Page 29: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/29.jpg)
![Page 30: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/30.jpg)
![Page 31: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/31.jpg)
m e d u l l a ( S y k e s , 1 9 0 8 ; S m i t h , 1 9 3 9 ; P a r k e r a n d F u , 1 9 6 5 ) .
The m e r i s t o d e r m i s a r e g i o n o f s e v e r a l c e l l l a y e r s , w h i c h
u n d e r g o r a p i d c e l l d i v i s i o n s . F o r c o n v e n i e n c e o f d e s c r i p t i o n ,
t h e c o r t e x i s d i v i d e d i n t o a n o u t e r a n d a n i n n e r r e g i o n ,
a l t h o u g h t h e r e i s no s h a r p d e m a r c a t i o n b e t w e e n t h e t w o . M u c i l a g e
d u c t s , w i t h s m a l l s e c r e t o r y c e l l s a r r a n g e d i n a r i n g , a r e
l o c a t e d i n t h e p e r i p h e r a l p a r t s o f t h e o u t e r c o r t e x ( F i g s . 2 ,
3 ) . W h e r e a s , c e l l s o f t h e o u t e r c o r t e x s e e m t o d i v i d e i n a l l
p l a n e s , t h o s e o f t h e i n n e r c o r t e x s e e m t o d i v i d e p r e f e r e n t i a l l y
i n t a n g e n t i a l a n d t r a n s v e r s e p l a n e s a n d g i v e r i s e t o v e r t i c a l
f i l e s o f c e l l s w h i c h d i f f e r e n t i a t e a s s i e v e e l e m e n t s ( ~ i g s . 4 ,
5).
The m e d u l l a c o n s i s t s o f t w o t y p e s o f c e l l s , s i e v e e l e m e n t s
a n d h y p h a l c e l l s , embedded i n a n i n t e r c e l l u l a r m a t r i x . I n c r o s s
s e c t i o n s , t h e s i e v e e l e m e n t s o f t e n o c c u r i n r a d i a l r o w s i n t h e
o u t e r r e g i o n o f t h e m e d u l l a ( F i g s . 2 , 6 ) . I n l o n g i t u d i n a l
s e c t i o n s , t h e s e s i e v e e l e m e n t s f o r m v e r t i c a l f i l e s o f c e l l s
b r i d g e d o n l y a t c r o s s c o n n e c t i o n s ( F i g s . 3 , 4 ) . The much
e l o n g a t e d , o l d e r s i e v e e l e m e n t s , some m o r e t h a n 1 mm l o n g ,
t r u m p e t - s h a p e d a t t h e i r c r o s s w a l l s , a r e f o u n d i n t h e c e n t e r o f
t h e m e d u l l a . T h e i r e n d w a l l s , e v e n t h e l u m e n , a r e o f t e n p l u g g e d
w i t h c a l l o s e ( F i g s . 6 , 7 ; 0 s ) . The h y p h a l c e l l s , a n o t h e r
m e d u l l a r y e l e m e n t , f o r m s e r i e s o f c y l i n d r i c a l c e l l s c o n n e c t e d
e n d t o e n d w h i c h a n a s t o m o s e b e t w e e n f i l e s o f s i e v e e l e m e n t s i n
t h e c e n t r a l m e d u l l a .
![Page 32: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/32.jpg)
![Page 33: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/33.jpg)
![Page 34: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/34.jpg)
Fig. 5. A composite of radial longitudinal sections through A showing the different stages of sieve element differentiation. The sieve elements arise from the innermost cortical cells (Sl), and become progressively elongated (S2-S4). In earlier stages numerous small vacuoles fill the cell, but they seem to disintegrate later. Note particularly the changes in nuclear size and staining in different stages of sieve element differentiation (hollow arrows). Note also the electron-dense globules (arrowheads with white small arrows) in S3 and S4. For definition of S1-S4 see RESULTS C-II............................................. ~ 5 7 0 ; ~ 2 9 0
![Page 35: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/35.jpg)
![Page 36: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/36.jpg)
F i g . 6 . C r o s s s e c t i o n o f t h e b a s a l i n t e r n o d e ( B p o i n t l o f t h e same f r o n d a s t h a t u s e d f o r F i g . 2 . N o t e t h e e n l a r g e d m e d u l l a a n d s i e v e e l e m e n t s w i t h f a i r l y t h i c k w a l l s . N o t e a l s o c a l l o s e - p l u g g e d s i e v e e l e m e n t s ( e n c i r c l e d a r e a s ) a n d o b l i t e r a t e d s i e v e e l e m e n t s ( a r r o w s ) . . . . . . . . . . . . . . . . . . . . . ~ 9 0
F i g . 7 . R a d i a l l o n g i t u d i n a l s e c t i o n t h r o u g h B , c o r r e s p o n d i n g t o F i g . 6 , s h o w i n g m a t u r e S 4 s i e v e e l e m e n t s . N o t e t h e t h i c k l a t e r a l w a l l s w h i c h i n p l a c e s h a v e b e e n s e c t i o n e d p a r a l l e l t o t h e i r s u r f a c e . A t t h e s e p l a c e s , t h e p r e d o m i n a t i n g t r a n s v e r s e o r i e n t a t i o n o f w a l l f i b r i l s i s e v i d e n t . C a l l o s e i s p r e s e n t i n o l d e r s i e v e e l e m e n t s i n t h e c e n t r a l m e d u l l a . . . x 1 8 0
F i g . 8 . L o n g i t u d i n a l s e c t i o n t h r o u g h B s h o w i n g o n e o f i m m a t u r e s i e v e e l e m e n t s h a v i n g n u c l e i ( a n u c l e u s shown b y a h o l l o w a r r o w ) b u t r e l a t i v e l y t h i c k l a t e r a l w a l l s . . . . . . . . . . . . . . x360
![Page 37: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/37.jpg)
![Page 38: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/38.jpg)
11. P a t t e r n o f p r o d u c t i o n o f s i e v e e l e m e n t s
M a c r o c y s t i s i n t e g r i f o l i a p l a n t s a r e p e r e n n i a l ; h o w e v e r ,
o n l y t h e h o l d f a s t p e r s i s t s f o r many y e a r s , t h e i n d i v i d u a l f r o n d s
h a v e a l i f e s p a n r a n g i n g f r o m 6 t o 8 m o n t h s ( L o b b a n , 1 9 7 8 d ) .
T a b l e I l i s t s t h e c o l l e c t i o n d a t a f o r a l l s a m p l e s u s e d i n t h i s
s t u d y . T h e s m a l l e s t i n t e r n o d e u s e d m e a s u r e d l e s s t h a n 1 cm, t h e
l o n g e s t o n e , on t h e o t h e r h a n d , was a l m o s t 70 cm l o n g .
N e v e r t h e l e s s , no m a t t e r w h a t t h e l e n g t h s o f t h e i n t e r n o d e s a t A
o r B p o i n t t h e d i a m e t e r s o f t h e m e d u l l a a s w e l l a s t h e s t i p e o f
a l l m a t e r i a l s r e v e a l l i t t l e v a r i a t i o n . F o r i n s t a n c e , t h e mean
d i a m e t e r s o f m e d u l l a a n d s t i p e a r e 0 . 8 - + 0.2 mm a n d 3.1 - + 0.5 mm
a t A p o i n t a n d 1 .6 - + 0.4 mm a n d 5 .8 - + 0 . 8 mm a t B p o i n t ,
r e s p e c t i v e l y ( T a b l e 1 1 ) . M o r e o v e r , t h e i n c r e a s e i n d i a m e t e r o f
t h e m e d u l l a b e t w e e n A p o i n t a n d B p o i n t i s i n c l o s e p r o p o r t i o n
t o t h a t o f t h e s t i p e , t h a t i s , on a n a v e r a g e , b o t h i n c r e a s e
a b o u t 2 t i m e s .
F u r t h e r m o r e , a s t h e s i e v e e l e m e n t s o c c u r c h a r a c t e r i s t i c a l l y
i n r a d i a l r ows i n t h e o u t e r m e d u l l a , t h e q u e s t i o n s a r i s e w h e t h e r
t h e r e i s a n i n c r e a s e i n t h e number o f r a d i a l r o w s a n d / o r t h e
number o f s i e v e e l e m e n t s i n e a c h row i n g o i n g f r o m A t o B p o i n t .
The d a t a show t h a t t h e r e i s o n l y a s m a l l d i f f e r e n c e i n t h e t o t a l
number o f r a d i a l r o w s o f s i e v e e l e m e n t s o b t a i n e d f r o m t h e t w o
p o i n t s ; e g g . 7 3 f o r A p o i n t v s . 76 f o r B p o i n t ( T a b l e I I I ) ,
w h i c h i n d i c a t e s t h a t t h e i n c r e a s e i n t h e d i a m e t e r o f t h e m e d u l l a
![Page 39: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/39.jpg)
Tab le I I . Diameters o f s t i p e and medul la o f A and B
f rom each sampled Macrocyst is f rond .
C o l l e c t i o n A B d iameter i n mm
Month diameter i n mm
S t i p e Medul la S t i p e Medul la
1978
May
June
Ju 1 y
Aug . Sep.
Nov . 1979
Jan.
Feb.
Mar.
Sep.
1980
Jan.
Feb.
Mar.
Mean 3.1 0.8 5.8 1.6
S.D. 0.5 0.2 0.8 0.4
![Page 40: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/40.jpg)
i n t h e o l d e r s t i p e i s n o t d e p e n d e n t o n t h e a d d i t i o n o f new rows
o f s i e v e e l e m e n t s .
I n t h i s s t u d y , t h e number o f p e r i m e d u l l a r y s i e v e e l e m e n t s
i n r a d i a l r o w s i s r e f e r r e d t o a s c e l l d e p t h . The c e l l d e p t h o f
t h e s i e v e e l e m e n t s r e m a i n s a p p r o x i m a t e l y t h e same f r o m A t o B
p o i n t ( o r 1 - 2 f i l e s o f s i e v e e l e m e n t s d e e p e r a t A p o i n t ) ( F i g .
9A, B ) , w h i c h s u g g e s t s t h a t t h e r e i s n o i n c r e a s e i n t h e number
o f s i e v e e l e m e n t s i n a r a d i a l r ow; h o w e v e r , t h i s i n t e r p r e t a t i o n
i s s t i l l c o m p l i c a t e d by t h e c o n s i d e r a t i o n t h a t new s i e v e e l e -
m e n t s may c o n t i n u e t o a r i s e f r o m t h e i n n e r c o r t i c a l c e l l s w h i l e
t h e o l d e r o n e s , t o w a r d t h e c e n t e r o f t h e m e d u l l a , become
s t r e t c h e d o u t a n d o b l i t e r a t e d .
By c o m p a r i n g F i g u r e 2 w i t h F i g u r e 6 , i t i s f o u n d t h a t t h e
i n t e r c e l l u l a r s p a c e s b e t w e e n l o n g i t u d i a l f i l e s o f s i e v e e l e m e n t s
i n e a c h r a d i a l row a r e much r e d u c e d a t B p o i n t c o m p a r e d t o t h o s e
a t A p o i n t . I t i s c l e a r l y s e e n t h a t c o n s i d e r a b l e a m o u n t s o f w a l l
m a t e r i a l s h a v e b e e n d e p o s i t e d o n t h e l a t e r a l w a l l s o f s i e v e
e l e m e n t s a t B p o i n t ( F i g s . 6 , 7 ) . F u r t h e r m o r e , t h e a v e r a g e
d i a m e t e r o f t h e s i e v e e l e m e n t s a t B p o i n t i s a l m o s t t w o t i m e s
l a r g e r t h a n t h a t a t A p o i n t ( T a b l e I V ) . T h e s e o b s e r v a t i o n s
s u g g e s t t h a t t h e i n c r e a s e i n d i a m e t e r o f m e d u l l a i s d u e
p r i m a r i l y t o a n i n c r e a s e i n d i a m e t e r o f s i e v e e l e m e n t s a n d i s
n o t d e p e n d e n t o n e i t h e r t h e a d d i t i o n o f new r o w s o f s i e v e
e l e m e n t s o r t h e a d d i t i o n o f new s i e v e e l e m e n t s i n a n y r a d i a l
row.
Two m a i n t y p e s o f s i e v e e l e m e n t s c a n b e d i s t i n g u i s h e d among
2 2
![Page 41: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/41.jpg)
Table I l l . Number o f r a d i a l rows o f s i e v e elements i n a
g iven x.s. o f medul la a t A and B p o i n t s o f
randomly se lec ted c o l l e c t i o n s . The d iameters
o f s i eve -p la te pores were a l s o recorded.
C o l l e c t i o n No. o f r a d i a l rows s i e v e - p l a t e pores
Month of s i eve elements f rom B p o i n t
A B (d iameter i n um) n=30
Sep. , 1978 7 0 7 4
Nov., 1978 7 5 80
Sep. , 1979 70 70
Feb., 1980 76 8 0
Mar., 1980 73 7 8
Mean
S.D.
![Page 42: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/42.jpg)
F i g . 9 . His tograms of c e l l d e p t h o f s i e v e e l e m e n t s i n r a d i a l rows ( n = 3 0 ) a t t h e o u t e r r e g i o n o f t h e m e d u l l a a t A and B. V e r t i c a l bar r e p r e s e n t s t w i c e t h e S. D.
![Page 43: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/43.jpg)
A : Apical
B: Basal
![Page 44: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/44.jpg)
F i g . 10'. P a t t e r n o f p r o d u c t i o n o f young s i e v e e l e m e n t s a t A and B i n d i f f e r e n t months shown i n b a r h i s t o g r a m . ( n = 5 0 r a d i a l r o w s ) V e r t i c a l b a r r e p r e s e n t s t w i c e t h e S . D .
![Page 45: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/45.jpg)
A: Apical
- - 4- - I
t - -
i -
- J J A S N F M S F M
4 1 9 7 8 1 $ 4 7 9 -1 < 1 9 8 0 - I
25b
![Page 46: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/46.jpg)
Table I V . Mean widths at cross walls of inner cortical cells
( c ) and different stages of sieve elements (s1-s4) compared at two levels: A vs. B from each collection.
S1-S3: young, differentiating sieve elements.
S4: mature sieve elements. W20.
Cell Types (width in urn)
Collection C 1 S2 3 4 Month A B A B A B A B A B
1978
May
June
Ju 1 y
Aug . Sep.
Nov . 1979
Jan.
Feb . Mar.
Sep.
1980
Jan.
Feb .
Mean 13 16 10 19 14 26 17 -- 31 45
S . D . 6 6 2 6 5 4 6 -- 8 10
![Page 47: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/47.jpg)
Table V . Mean leng ths o f d i f f e r e n t stages o f s i e v e elements (sl-S4)
and i nne r c o r t i c a l c e l l s (c) f rom each c o l l e c t i o n a t A and
B in ternodes.
S 1 - S 3 : young, d i f f e r e n t i a t i n g s i eve elements. n=10.
S4: mature s i eve elements. n=5.
C e l l Types ( l e n g t h i n um)
C o l l e c t i o n - Month A B A B A B A B A B
1978
May
June
J u l y
Aug . Sep.
Nov . 1979
Jan.
Feb . Mar.
1980
Jan.
Feb .
Mean 30 64 61 92 114 190 180 295 248 629
S.D. 9 20 18 23 13 74 35 -- 80 221
![Page 48: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/48.jpg)
t h e p e r i m e d u l l a r y s i e v e e l e m e n t s , n a m e l y , t h e o u t e r l a y e r s o f
d i f f e r e n t i a t i n g e l e m e n t s a n d t h e i n n e r l a y e r s o f d i f f e r e n t i a t e d
e l e m e n t s . A l t h o u g h d i f f e r e n t i a t i o n i s a c o n t i n u o u s p r o c e s s , f o r
c o n v e n i e n c e o f d e s c r i p t i o n , i t i s u s e f u l t o g r o u p s i e v e e l e m e n t s
i n t o d i f f e r e n t s t a g e s . T h i s i s s h o w n i n F i g u r e 5. The o u t e r m o s t
l a y e r o f c e l l s i n t h e m e d u l l a , w h i c h a l r e a d y s h o w s some d i s t i n c t
c y t o p l a s m i c c h a n g e s o v e r t h e i n n e r c o r t i c a l c e l l s , i s t e r m e d t h e
S1 s t a g e . T h e e l o n g a t i n g c e l l s w i t h a b u n d a n t c y t o p l a s m a n d
m a x i m a l l y e x p a n d e d n u c l e i a n d n u c l e o l i a r e i n t h e S 2 s t a g e . When
t h e c y t o p l a s m i c c o n t e n t s o f t h e d e v e l o p i n g s i e v e e l e m e n t s e n t e r
t h e p r o c e s s o f d i s i n t e g r a t i o n , t h i s i s r e f e r r e d t o a s t h e S 3
s t a g e . I n t h e S4 s t a g e , s i e v e e l e m e n t s n o l o n g e r p o s s e s s n u c l e i
a n d h a v e p e r f o r a t e d s i e v e p l a t e s a t t h e i r e n d w a l l s . T h e s e S4
c e l l s , s o l a b e l e d i n F i g u r e s 5 , a n d 7 , a r e c o n s i d e r e d t o b e
d i f f e r e n t i a t e d o r m a t u r e s i e v e e l e m e n t s .
The n u m b e r o f l o n g i t u d i n a l f i l e s o f y o u n g d i f f e r e n t i a t i n g
s i e v e e l e m e n t s f o r d i f f e r e n t m o n t h s o v e r a o n e a n d h a l f y e a r
p e r i o d f o r A a n d B p o i n t s i s p r e s e n t e d i n F i g u r e 10 . A l t h o u g h
t h e d a t a a r e i n c o m p l e t e f o r a n y o n e y e a r , t a k e n t o g e t h e r d a t a
f r o m t h r e e y e a r s i n d i c a t e a g r a d u a l d e c r e a s e i n t h e f i l e s o f
d i f f e r e n t i a t i n g s i e v e e l e m e n t s f r o m s p r i n g t o w i n t e r m o n t h s a t A
p o i n t . T h i s may r e f l e c t t h e a c t i v e g r o w t h o f t h e p l a n t i t s e l f i n
t h e s p r i n g s e a s o n . A l t e r n a t i v e l y i t may i n d i c a t e t h a t a s t h e
y e a r a d v a n c e s m o r e a n d m o r e s i e v e e l e m e n t s become f u l l y
d i f f e r e n t i a t e d . A c o m p a r i s o n o f F i g u r e s 9 a n d 1 0 f u r t h e r
i n d i c a t e s t h a t w h e r e a s m o s t o f t h e p e r i m e d u l l a r y s i e v e e l e m e n t s
![Page 49: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/49.jpg)
a t A p o i n t a r e u n d e r g o i n g d i f f e r e n t i a t i o n , t h e m a j o r i t y a t B
p o i n t a r e f u l l y d i f f e r e n t i a t e d ( s e e a l s o F i g s . 3 , 7 ) . H o w e v e r , a
number o f d e a d , s t r e t c h e d - o u t s i e v e e l e m e n t s , w h i c h h a d l o s t t h e
c h a r a c t e r i s t i c a r r a n g e m e n t i n r a d i a l r o w s , w e r e f o u n d s c a t t e r e d
i n t h e c e n t r a l m e d u l l a e v e n a t A p o i n t ( F i g . 2 ) . T h i s i m p l i e s
t h a t t h e d e v e l o p m e n t o f s i e v e e l e m e n t s m u s t o c c u r v e r y c l o s e t o
t h e m e r i s t e m a t i c r e g i o n a n d e v e n b e f o r e t h e f i r s t f r e e b l a d e i s
d e t a c h e d f r o m t h e a p i c a l s c i m i t a r a n d t h e f i r s t i n t e r n o d e i s
f o r m e d . -
A l t h o u g h o n e o r t w o l a y e r s o f u n d i f f e r e n t i a t e d s i e v e
e l e m e n t s a r e u s u a l l y p r e s e n t a t B p o i n t , t h e s e s i e v e e l e m e n t s
a p p e a r much e l o n g a t e d a n d show t h i c k w a l l s ( F i g . 8 , S 2 ) . They
s e e m t o h a v e b e e n p r o d u c e d a t a n e a r l i e r t i m e , b u t p r e s u m a b l y
r e m a i n u n d i f f e r e n t i a t e d . S i n c e t h e r e was l i t t l e f l u c t u a t i o n i n
t h e number o f t h e s e u n d i f f e r e n t i a t e d s i e v e e l e m e n t s i n d i f f e r e n t
s e a s o n s ( F i g . ~ O B ) , t h i s may f u r t h e r i n d i c a t e t h a t s i e v e e l e m e n t
d i f f e r e n t i a t i o n i s n o l o n g e r o c c u r r i n g a t B a r e a s .
111. O r i g i n of s i e v e e l e m e n t s a n d h y p h a e
I t i s known t h a t m e r i s t o d e r m a n d c o r t e x u n d e r g o f r e q u e n t
c e l l d i v i s i o n s a n d c o n t r i b u t e t o t h e l o n g i t u d i n a l g r o w t h o f t h e
s t i p e . T h e s e d i v i s i o n s , a s s e e n i n t h e i n n e r c o r t e x , a r e n e a r l y
e x c l u s i v e l y t r a n s v e r s e t o t h e l o n g a x i s o f t h e s t i p e , b u t b e y o n d
a c e r t a i n p o i n t , t h e y s t o p c o m p l e t e l y ( F i g . 4 ) . When t h e s e
![Page 50: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/50.jpg)
i n n e r m o s t c o r t i c a l c e l l s c e a s e t h e i r t r a n s v e r s e d i v i s i o n s , t h e y
d i f f e r e n t i a t e i n t o m e d u l l a r y e l e m e n t s : s i e v e e l e m e n t s a n d h y p h a l
c e l l s .
The i n n e r m o s t c o r t i c a l c e l l s w h i c h u n d e r g o no f u r t h e r
t r a n s v e r s e d i v i s i o n s a n d w h i c h a p p e a r i n v e r t i c a l f i l e s a l r e a d y
b e g i n t o b e s e p a r a t e d f r o m t h e i n n e r c o r t e x by a m a t r i x o f
i n t e r c e l l u l a r s u b s t a n c e ( F i g s . If, 5 ) . T h e r e s u l t i n g s i e v e
e l e m e n t s , t h e r e f o r e , a l s o o c c u r ' i n v e r t i c a l f i l e s w h i c h a r e
s e p a r a t e d f r o m e a c h o t h e r b y t h e g r o u n d m a t r i x . The d e v e l o p m e n t
o f s i e v e e l e m e n t s p r o c e e d s c e n t r i p e t a l l y f r o m t h e o u t e r m o s t
l a y e r ( o r t h e i n n e r m o s t c o r t i c a l c e l l s ) t o w a r d t h e c e n t e r o f t h e
m e d u l l a . C o n s e q u e n t l y , o n e f i n d s t h e y o u n g e s t s i e v e e l e m e n t s a t
t h e f r i n g e o f t h e m e d u l l a a n d t h e o l d e r e l e m e n t s p r o g r e s s i v e l y
i n w a r d . The o l d e s t , o b l i t e r a t e d s i e v e e l e m e n t s a r e s i t u a t e d i n
t h e c e n t r a l m e d u l l a . The s e p a r a t i o n b e t w e e n v e r t i c a l f i l e s o f
s i e v e e l e m e n t s i s f a r m o r e p r o n o u n c e d a l o n g t h e r a d i a l w a l l s
t h a n t h e t a n g e n t i a l w a l l s . S m a l l o u t g r o w t h s , p a p i l l a e , a r i s e m o s t l y n e a r t h e c r o s s
w a l l s o f y o u n g s i e v e e l e m e n t s a n d f u s e w i t h s i m i l a r o u t g r o w t h s
f r o m t h e a d j a c e n t f i l e s t o f o r m c r o s s c o n n e c t i o n s ( F i g . 4 ) .
P r o t u b e r a n c e s o f t h e i n n e r c o r t i c a l c e l l s p e n e t r a t e
c e n t r i p e t a l l y t h r o u g h t h e i n t e r c e l l u l a r m a t e r i a l t o become t h e
h y p h a l c e l l s ( F i g . l l ) , s o c a l l e d f o r t h e i r r e s e m b l a n c e t o
f u n g a l h y p h a e . They b r a n c h a n d r u n i n a l l d i r e c t i o n s t h r o u g h o u t
t h e m e d u l l a . No c o n n e c t i o n s b e t w e e n s i e v e e l e m e n t s a n d h y p h a l
c e l l s h a v e b e e n s e e n i n t h i s s t u d y . A l t h o u g h s i e v e e l e m e n t s a n d
![Page 51: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/51.jpg)
h y p h a e s e e m t o b e d e r i v e d f r o m t h e s a m e o r i g i n , t h e y t u r n o u t t o
b e t w o d i s t i n c t a n d i n d e p e n d e n t e n t i t i e s . H y p h a l c e l l s a p p e a r t o
b e s t r u c t u r a l l y f a r l e s s s p e c i a l i z e d t h a n t h e s i e v e e l e m e n t s a n d
t h e i r f u n c t i o n r e m a i n s unknown.
A s i n d i c a t e d p r e v i o u s l y , t h e s u c c e s s i v e s t a g e s o r s e q u e n c e
o f d i f f e r e n t i a t i o n o f t h e s i e v e e l e m e n t s c a n b e f o l l o w e d f r o m
t h e p e r i p h e r a l r e g i o n t o t h e i n t e r i o r o f t h e m e d u l l a ,
p a r t i c u l a r l y , i n t h e a p i c a l p a r t o f t h e s t i p e . T h e r e f o r e , t h e
o b s e r v a t i o n s o n t h e d e v e l o p m e n t o f s i e v e e l e m e n t s r e p o r t e d h e r e
a r e b a s e d o n a s t u d y o f t h e y o u n g , a p i c a l p a r t o f t h e s t i p e .
I V . D i f f e r e n t i a t i o n of s i e v e e l e m e n t s
L i g h t m i c r o s c o p i c o b s e r v a t i o n s
P a r e n c h y m a c e l l s o f t h e c o r t e x h a v e a l a r g e c e n t r a l v a c u o l e
a n d o n l y a t h i n s h e a t h o f c y t o p l a s m a r o u n d t h e c e l l p e r i p h e r y . A
s m a l l n u c l e u s a n d a f e w p l a s t i d s c a n b e s e e n i n t h e p a r i e t a l
c y t o p l a s m . By c o n t r a s t , t h e y o u n g s i e v e e l e m e n t s ( e . g . , S 1 - ~ 2 )
h a v e v e r y d e n s e c y t o p l a s m , n u m e r o u s r e l a t i v e l y s m a l l v a c u o l e s , a
l a r g e number o f p l a s t i d s , a n d a m o r e - o r - l e s s c e n t r a l l y l o c a l i z e d
![Page 52: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/52.jpg)
F i g . 11 . C r o s s s e c t i o n o f a p o r t i o n o f a m e d u l l a t h r o u g h A . N o t e n u c l e i ( a r r o w h e a d s ) i n d i f f e r e n t i a t i n g s i e v e e l e m e n t s . O l d , o b l i t e r a t e d s i e v e e l e m e n t s a r e p r e s e n t i n t h e c e n t r a l m e d u l l a . P r o t u b e r a n c e s o f i n n e r c o r t i c a l c e l l s a r e t o f o r m h y p h a l c e l l s (Hy) ..................................... x 3 4 0
F i g . 1 2 . S u r f a c e ' v i e w t h r o u g h a c r o s s w a l l o f a c o r t i c a l c e l l s h o w i n g c i r c u l a r p r i m a r y p i t f i e l d s ( a r r o w s ) i n a p e r i p h e r a l r i n g - f a sh ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x 4 8 0
F i g . 1 3 . C r o s s s e c t i o n o f a p o r t i o n o f a m e d u l l a t h r o u g h B s h o w i n g p a r t s o f t w o m a t u r e s i e v e p l a t e s . . . . . . . . . . . . . . . x 3 4 0
F i g . 1 4 . E n l a r g e d s i e v e p l a t e o f o n e o f t h e t w o p l a t e s i n F i g . 1 3 . C y t o p l a s m i c s t r a n d s ( a r r o w s ) c a n b e s e e n i n t h e p o r e canals........................................... ~ 7 6 0
![Page 53: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/53.jpg)
![Page 54: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/54.jpg)
n u c l e u s w i t h a p r o m i n e n t n u c l e o l u s ( F i g . 5 ) . I n a d d i t i o n , t h e s e
c e l l s may r e a c h more t h a n t e n t i m e s t h e i r o r i g i n a l l e n g t h ( T a b l e
V). S u b s e q u e n t l y , t h e y o u n g s i e v e e l e m e n t s u n d e r g o m o d i f i c a t i o n s
i n t w o i m p o r t a n t r e s p e c t s b e f o r e b e c o m i n g t h e c h a n n e l s o f
t r a n s l o c a t i o n . One i s t h e d e g r a d a t i o n o f t h e c y t o p l a s m a n d some
o f i t s o r g a n e l l e s ; t h e o t h e r i s t h e p e r f o r a t i o n o f t h e s i e v e
p l a t e . The l a t t e r t o p i c w i l l b e d e a l t w i t h i n P a r t C-IV-2. T h e
s e q u e n t i a l d e v e l o p m e n t o f t h e s i e v e e l e m e n t s i s d i s p l a y e d
r e m a r k a b l y w e l l i n l o n g i t u d i n a l s e c t i o n s o f a y o u n g s t i p e ( F i g .
5).
A t t h e v e r y b e g i n n i n g , t h e p u t a t i v e s i e v e e l e m e n t n o l o n g e r
h a s a s i n g l e c e n t r a l v a c u o l e b u t s e v e r a l s m a l l e r v a c u o l e s
s e p a r a t e d by c y t o p l a s m i c s t r a n d s , a n d a n e x p a n d i n g n u c l e u s w i t h
a c o n s p i c u o u s n u c l e o l u s ( ~ i g s . 4 , 5 ) . A s t h e y o u n g s i e v e e l e m e n t
o f 5 2 c o n t i n u e s t o e l o n g a t e , t h e a m o u n t o f c y t o p l a s m i n c r e a s e s
a s d o t h e number o f p l a s t i d s a n d s m a l l v a c u o l e s . B o t h t h e
n u c l e u s a n d t h e n u l e o l u s i n c r e a s e i n v o l u m e a l m o s t t w o - f o l d o v e r
t h e p r e v i o u s s t a g e ( T a b l e V I ) . T h e n u c l e u s a n d t h e n u c l e o l u s
a l s o show v e r y s t r o n g a f f i n i t y t o t h e b a s i c d y e t o l u i d i n e b l u e .
The s y n t h e s i s o f t h e c e l l u l a r c o n t e n t s seems t o r e a c h a p e a k i n
s t a g e S2 f o l l o w e d by b r e a k d o w n o f t h e c y t o p l a s m . I n t h e
f o l l o w i n g s t a g e ( S 3 ) t h e d e n s e c y t o p l a s m i s r e p l a c e d by a
v a c u o l a r s y s t e m w i t h a p a r i e t a l c y t o p l a s m . The n u c l e u s now
a p p e a r s d i f f u s e a n d l o s e s i t s s t a i n a b i l i t y ; h o w e v e r , t h e
n u c l e o l u s s t i l l s t a n d s o u t a s a d i s c r e t e b o d y b u t s o m e w h a t
r e d u c e d i n s i z e . P l a s t i d s a l s o become o b s c u r e a n d c a n n o l o n g e r
![Page 55: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/55.jpg)
Table V I . Diameters o f n u c l e i (N) and n u c l e o l i (Nu) i n d i f -
f e r e n t stages o f young s i e v e elements ( S -S ) and 1 3
i n i nne r c o r t i c a l c e l l s ( c ) . These measurements
were made under the l i g h t microscope i n s e r i a l sec-
t i o n s . Care was taken t o ensure t h a t whole ( o r
n e a r l y whole) n u c l e i were measured. n=10.
C e l l Types (d iameter i n um)
C o l l e c t i o n C 1 S2
Month N Nu N Nu N Nu N s3
Nu
Sep. , 1978 4.4 1.0 5.9 2.0 6.2 2.5 7.0 2.0
Jan. , 1980 4.7 1.6 4.7 2.0 6.4 2.3 7.2 2.0
Jan., 1980 4.6 1.0 5.7 1.8 6.4 2.7 7.8 2.3
Feb., 1980 4.7 1.2 5.0 1.7 6.5 2.3 8.1 2.6
Mean 4.6 1.2 5.3 1.9 6.4 2.5 7.5 2.2
S.D. 0.1 0.3 0.6 0.2 0.1 0.2 0.5 0.3
![Page 56: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/56.jpg)
b e c l e a r l y i d e n t i f i e d . N o n e t h e l e s s , t h e l o n g i t u d i n a l e l o n g a t i o n
a n d l a t e r a l e x p a n s i o n o f t h e d i f f e r e n t i a t i n g s i e v e e l e m e n t s
c o n t i n u e s ( T a b l e s I V Y V). The c o n s i d e r a b l e i n c r e a s e i n t h e w a l l
t h i c k n e s s , e s p e c i a l l y , of t h e l a t e r a l w a l l s i s a l s o a c o n t i n u o u s
p r o c e s s . I t i s a t t h i s S 3 s t a g e t h a t c h a n g e s i n t h e e n d w a l l s
b e g i n ( s e e P a r t C-IV-2) .
A s t h e a b o v e phenomena p r o g r e s s , t h e c y t o p l a s m b e c o m e s v e r y
t h i n a n d s h o w s l i t t l e a f f i n i t y t o v a r i o u s s t a i n s , V a r i o u s s i z e s
o f d e n s e g l o b u l e s ( 1 - 2 um i n d i a m e t e r ) a r e p r e s e n t h e r e a n d
t h e r e , p a r t i c u l a r l y i n t h e p a r i e t a l c y t o p l a s m o f more
d i f f e r e n t i a t e d e l e m e n t s ( F i g . 5 , S 3 a n d S 4 ) . The n u c l e u s i s now
g r e a t l y d e f o r m e d a n d s e e m s t o l o s e i t s n u c l e o p l a s m c o m p l e t e l y '
( F i g s . 5 , 1 1 ) . A s m a l l c o m p a c t n u c l e o l u s s t i l l e x i s t s i n t h e
n u c l e u s . T h e f u t u r e p o r e s i t e s w i t h c y t o p l a s m i c s t r a n d s p a s s i n g
t h r o u g h t h e m c a n b e i d e n t i f i e d i n t h e c r o s s w a l l s u n d e r t h e
p h a s e - c o n t r a s t m i c r o s c o p e . The d y n a m i c c h a n g e s i n t h e y o u n g
s i e v e e l e m e n t s l e a d t o t h e f o r m a t i o n o f m a t u r e s i e v e e l e m e n t s
w h i c h a r e f u n c t i o n a l l y s p e c i a l i z e d f o r l o n g i t u d i n a l t r a n s p o r t o f
p h o t o a s s i m i l a t e s , a s i s d e m o n s t r a t e d l a t e r i n P a r t C-V.
The l o s s o f t h e n u c l e u s i s u s u a l l y a c c o m p a n i e d by t h e
p e r f o r a t i o n o f t h e s i e v e p l a t e . I t w a s n o t e d p r e v i o u s l y t h a t t h e
d i f f e r e n t i a t i o n o f s i e v e e l e m e n t s p r o c e e d s c e n t r i p e t a l l y . The
m a t u r a t i o n o f t h e s i e v e p l a t e s o c c u r s i n t h e same m a n n e r . My
o b s e r v a t i o n s i n d i c a t e t h a t m o s t m a t u r e s i e v e e l e m e n t s o f S4 o f
M e i n t e g r i f o l i a a r e e n u c l e a t e ; h o w e v e r , r e m n a n t s o f n u c l e i h a v e -.
b e e n s e e n i n some e a r l y f o r m e d b u t o b l i t e r a t i n g e l e m e n t s .
![Page 57: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/57.jpg)
I n r e l a t i v e l y young p a r t s o f t h e s t i p e , t h e m a t u r e s i e v e
e l e m e n t s r e t a i n t h e v a c u o l a r s y s t e m . B u t i n t h e o l d e r p a r t s of
t h e s t i p e ( e . g . B p o i n t ) t h e l u m e n o f a m a t u r e s i e v e e l e m e n t i s
d e v o i d o f d i s c e r n i b l e v a c u o l e s a n d t h e r e i s o n l y a t h i n s h e a t h
o f p a r i e t a l c y t o p l a s m ( F i g s . 7 , 8 ; S 4 ) .
C a l l o s e i s n o t d e t e c t e d i n S 1 t h r o u g h S4 b y a n i l i n e b l u e
s t a i n i n g . T h e o l d s i e v e e l e m e n t s ( F i g . 7 , l a b e l e d a s 0 s ) i n t h e
more c e n t r a l p a r t s o f t h e m e d u l l a , h o w e v e r , o f t e n h a v e m a s s i v e
c a l l o s e p l u g s a t t h e i r e n d w a l l s ; s o m e t i m e s t h e l u m i n a a l s o a r e
l i n e d w i t h c a l l o s e . S i n c e t h e s e o l d s i e v e e l e m e n t s i n t h e c e n t e r
o f t h e m e d u l l a c e a s e d g r o w i n g l o n g a g o , t h e y a r e s u b j e c t t o
p a s s i v e l o n g i t u d i n a l s t r e t c h i n g w i t h t h e a x i a l g r o w t h o f t h e
o r g a n a n d t h u s become much e l o n g a t e d . A l t h o u g h t h e s e o l d s i e v e
e l e m e n t s o f t e n show c l u m p s o f m a t e r i a l , t h e y h a v e n o
r e c o g n i z a b l e o r g a n e l l e s , e. g . , n u c l e u s o r p l a s t i d s .
O b s e r v a t i o n s w i t h e l e c t r o n m i c r o s c o p e
The p r o t o p l a s m o f t h e y o u n g s i e v e e l e m e n t ( S l ) i s r i c h i n
v a r i o u s o r g a n e l l e s , n a m e l y , r i b o s o m e s , e n d o p l a s m i c r e t i c u l u m
(ER), d i c t y o s o m e s , m i t o c h o n d r i a , p l a s t i d s a n d v a c u o l e s ( F i g s .
1 5 , 17). N u c l e i a n d n u c l e o l i a r e e s p e c i a l l y p r o m i n e n t i n t h e s e
y o u n g e l e m e n t s . D u r i n g d i f f e r e n t i a t i o n , c h a n g e s o c c u r i n n e a r l y
![Page 58: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/58.jpg)
![Page 59: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/59.jpg)
![Page 60: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/60.jpg)
F i g . 1 6 . A n u c l e u s o f a n i n n e r c o r t i c a l c e l l s h o w s a n a n g u l a r s h a p e p r o b a b l y b e c a u s e i t i s p r e s s e d b e t w e e n t h e l a r g e c e n t r a l v a c u o l e a n d t h e w a l l . N o t e t h e c h r o m a t i n m a s s e s ( C h ) i n t h e n u c l e o p l a s m a n d n u c l e a r p o r e s ( a r r o w s ) . ~ 2 4 , 0 0 0
F i g . 1 7 . A n u c l e u s o f a n S 1 s i e v e e l e m e n t s h o w s a h i g h l y h o m o g e n e o u s n u c l e o p l a s m w i t h a c o n s p i c u o u s n u c l e o l u s . N o t e t h e s p a t i a l r e l a t i o n s h i p b e t w e e n d i c t y o s o m e s ( a r r o w s ) a n d t h e n u c l e u s . N o t e a l s o many m i t o c h o n d r i a a l o n g t h e c r o s s w a l l . P l a s t i d s a n d m i c r o b o d i e s a r e common. E R m e m b r a n e s a r e s t u d d e d w i t h r i b o s o m e s . N u m e r o u s p l a s m o d e s m a t a a r e p r e s e n t i n t h e c r o s s wal l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ 1 0 , 2 0 0
![Page 61: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/61.jpg)
![Page 62: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/62.jpg)
- a l l t h e o r g a n e l l e s a n d membrane s y s t e m s . The v a c u o l a r membrane
o r t o n o p l a s t p e r s i s t s f o r a l o n g t i m e , b u t e v e n t u a l l y s e e m s t o
b r e a k down i n t h e m a t u r e , f u n c t i o n i n g s i e v e e l e m e n t . The l e a s t
c h a n g e d s t r u c t u r e s a r e m i t o c h o n d r i a , p l a s t i d s , a n d p l a s m a l e m m a .
A m o r e - d e t a i l e d d e s c r i p t i o n o f t h e c h a n g e s i n v a r i o u s o r g a n e l l e s
i n t h e c o u r s e o f s i e v e e l e m e n t d i f f e r e n t i a t i o n f o l l o w s .
N u c l e u s a n d N u c l e o l u s
The n u c l e i o f t h e y o u n g s i e v e e l e m e n t s h a v e a p r o m i n e n t
n u c l e o l u s a n d a d i s t i n c t d o u b l e n u c l e a r e n v e l o p e i n t e r r u p t e d b y
n u c l e a r p o r e s ( F i g s . 1 7 , 1 8 ) . A c o n s p i c u o u s f e a t u r e o f t h e s e
n u c l e i i s t h e h i g h l y h o m o g e n e o u s n u c l e o p l a s m w h i c h h a s a
f i b r i l l a r c o n s i s t e n c y a n d n u m e r o u s p a r t i c l e s , p r e s u m a b l y , of
r i b o n u c l e o p r o t e i n . The S2 n u c l e o l u s s h o w s t w o d i s t i n g u i s h a b l e
z o n e s : t h e f i b r i l l a r z o n e , t h e g r a n u l a r z o n e ( F i g . 2 1 ) . The
f i b r i l l a r z o n e s e e m s t o f o r m t h e c e n t r a l c o r e o f t h e n u c l e o l u s
a n d i s i n f i l t r a t e d by s m a l l e l e c t r o n - l i g h t a r e a s ( v a c u o l a r
a r e a s ) r e s e m b l i n g t h e l i g h t e r a r e a s o f t h e n u c l e o p l a s m . The
g r a n u l a r z o n e c o n s i s t i n g o f g r a n u l e s 2 2 nm i n d i a m e t e r , m a k e s u p
t h e p e r i p h e r a l r e g i o n o f t h e n u c l e o l u s ( F i g . 2 1 , ~ n s e t ) .
Compared w i t h t h o s e o f t h e y o u n g s i e v e e l e m e n t s , t h e n u c l e i o f
t h e c o r t i c a l c e l l s ( F i g . 1 6 ) r e v e a l s i g n i f i c a n t d i f f e r e n c e s
![Page 63: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/63.jpg)
![Page 64: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/64.jpg)
![Page 65: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/65.jpg)
s u g g e s t i n g t h e m e t a b o l i c d i f f e r e n c e s b e t w e e n t h e t w o c e l l t y p e s .
F i r s t , t h e r e i s a much h i g h e r l e v e l o f c h r o m a t i n c l u m p i n g i n t h e
n u c l e o p l a s m o f t h e c o r t i c a l n u c l e i . S e c o n d , t h e n u c l e i a n d
n u c l e o l i o f t h e c o r t i c a l c e l l s a r e much l e s s c o n s p i c u o u s t h a n
t h o s e o f S 1 ; a l s o t h e p r o p o r t i o n o f g r a n u l a r r e g i o n t o f i b r i l l a r
r e g i o n i n t h e n u c l e o l u s i s g r e a t e r i n S 1 t h a n . i n c o r t i c a l c e l l s .
B e c a u s e t h e r e i s a s i n g l e c e n t r a l v a c u o l e i n t h e c o r t i c a l c e l l s ,
t h e n u c l e u s a n d t h e o t h e r c e l l o r g a n e l l e s a p p e a r p u s h e d i n t o t h e
l i m i t e d s p a c e b e t w e e n t h e t o n o p l a s t a n d p l a s m a l e m m a a n d o f t e n
show a n a n g u l a r s h a p e r a t h e r t h a n t h e u s u a l c i r c u l a r s h a p e .
Howeve r , t h e n u c l e i o f S 1 a r e more o r l e s s r o u n d , c e n t r a l l y
l o c a t e d a n d a r e l a r g e r t h a n t h o s e o f c o r t i c a l c e l l s ( T a b l e V I ) .
I n S 2 s t a g e , w h i l e t h e c y t o p l a s m i c c o n t e n t s c o n t i n u e t o
p r o l i f e r a t e , b o t h t h e n u c l e u s a n d t h e n u c l e o l u s a p p e a r t o
a c h i e v e t h e i r p e a k d e v e l o p m e n t ( F i g . 2 1 ) . T h e s h a p e o f t h e
n u c l e u s i s more o r l e s s c i r c u l a r a t t h e b e g i n n i n g o f S2 s t a g e ,
b u t i t b e c o m e s h i g h l y l o b e d a n d e l o n g a t e d l a t e r ( F i g s . 1 8 , 2 1 ) .
I n a d d i t i o n , many a g g r e g a t e s , p r e s u m a b l y c o n d e n s e d c h r o m a t i n ,
a r , e f o u n d i n t h e n u c l e o p l a s m . T h e s e phenomena become m o r e
p r o n o u n c e d i n t h e n u c l e u s o f S 3 ( F i g . 2 2 ) . T h e m o s t s t r i k i n g
c h a n g e , h o w e v e r , o c c u r s i n t h e n u c l e o l u s w h i c h s e e m s t o l o s e i t s
s u b s t r u c t u r e c o m p l e t e l y a n d a p p e a r s a s a much r e d u c e d , c o m p a c t
body ( F i g . 2 2 ) . When some d i s c e r n i b l e c h a n g e s o c c u r o n t h e c r o s s
w a l l s o f S 3 ( s e e P a r t C - IV-2 ) , t h e n u c l e u s , i f p r e s e n t , s h o w s
e v e r y s i g n o f b e i n g n o n f u n c t i o n a l ( F i g . 2 3 ) . A l t h o u g h t h e s e
d e g e n e r a t i n g n u c l e i c a n s t i l l b e d i s t i n g u i s h e d u n e q u i v o c a l l y by
![Page 66: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/66.jpg)
t h e e n c l o s i n g n u c l e a r e n v e l o p e a n d a p p a r e n t l y n o r m a l s t r u c t u r e
o f n u c l e a r p o r e s ( F i g . 24), t h e n u c l e o p l a s m a p p e a r s d e v o i d o f
s t r u c t u r e e x c e p t f o r o c c a s i o n a l f l o c c u l e n t r e s i d u e s . The
n u c l e o l u s a s a d e n s e , a m o r p h o u s s p h e r i c a l body i s s t i l l r e t a i n e d
i n t h e n u c l e u s a t t h e e a r l y S 3 s t a g e , b u t i t - d i s a p p e a r s
e v e n t u a l l y .
D i c t y o s o m e s
T h e r e a r e o n l y a few d i c t y o s o m e s i n c o r t i c a l c e l l s , b u t a t
t h e i n c e p t i o n o f t h e s i e v e e l e m e n t s , t h e y a p p e a r i n i n c r e a s i n g
n u m b e r s a n d a r e s e e n p r e d o m i n a n t l y a r o u n d t h e n u c l e u s ( F i g s . 1 7 ,
1 9 ) . E a c h d i c t y o s o m e c o n s i s t s o f a s t a c k o f 3 t o 8 c i s t e r n a e
w i t h t h e f o r m i n g f a c e f a c i n g t h e n u c l e u s a n d t h e m a t u r e i n g f a c e
t o w a r d s t h e c y t o p l a s m . S m a l l t r a n s i t i o n v e s i c l e s a r e o f t e n s e e n
b e t w e e n t h e n u c l e u s a n d t h e d i c t y o s o m e s ( F i g . 1 9 ) ; t h e y may
c o n t r i b u t e t o t h e c i s t e r n a e o n t h e f o r m i n g f a c e o f t h e
d i c t y o s o m e by f u s i n g t o g e t h e r . The o u t e r m o s t c i s t e r n a e a t t h e
m a t u r e s i d e o f t h e d i c t y o s o m e s become i n f l a t e d a n d a r e
e v e n t u a l l y p i n c h e d o f f o r r e l e a s e d a s d i s c r e t e v e s i c l e s ( F i g -
20). Many l a r g e a n d s m a l l v e s i c l e s a r o u n d t h e d i c t y o s o m e a r e
b e l i e v e d t o b e d e r i v e d f r o m b l e b b i n g o f f t h e e d g e s o f d i c t y o s o m e
l a m e l l a e . A c c o m p a n y i n g t h e c y t o p l a s m i c c h a n g e s , t h e c e l l w a l l s ,
![Page 67: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/67.jpg)
F i g . 1 9 . S m a l l v e s i c l e s p r e s e n t b e t w e e n n u c l e a r e n v e l o p e ( s e e a r r o w s ) a n d t h e f o r m i n g f a c e o f t h e d i c t y o s o m e a r e n o t s e e n e l s e w h e r e o u t s i d e t h e n u c l e u s . T h e s e v e s i c l e s s e e m t o b e p r o d u c e d f r o m t h e o u t e r membrane o f t h e n u c l e a r e n v e l o p e . . . . ~ 4 0 , 0 0 0
F i g . 2 0 . . S u r f a c e p a r a l l e l s e c t i o n t h r o u g h a n S 2 n u c l e u s . A l a r g e number o f h y p e r t r o p h i c d i c t y o s o m e s i s l o c a t e d a r o u n d t h e n u c l e u s . N o t e a l s o many v e s i c l e s w h i c h a r e a p p a r e n t l y d e r i v e d f r o m t h e i n f l a t e d e d g e s o f t h e d i c t y o s o m e l a m e l l a e . . ~ 2 4 , 0 0 0
F i g . 2 1 . A h i g h l y l o b e d n u c l e u s i n t h e l a t e S2 s t a g e . The n u c l e = l u s e x p a n d s t c a l m c s t t w i c e t h e s i z e z s t h a t i n p r e v i o u s S1 s t a g e , h a v i n g s m a l l v a c u o l a r a r e a s . .... ~ 2 4 , 0 0 0 I n s e t i s a n e n l a r g e d p o r t i o n o f t h e n u c l e o l u s ( o u t l i n e d by a b l a c k l i n e ) s h o w i n g f i b r i l l a r p a t c h e s a n d g r a n u l e s ( c a . 22 nm i n d i ame te r ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ 4 0 , 0 0 0
![Page 68: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/68.jpg)
![Page 69: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/69.jpg)
![Page 70: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/70.jpg)
![Page 71: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/71.jpg)
p a r t i c u l a r l y t h e l a t e r a l w a l l s , of d e v e l o p i n g s i e v e e l e m e n t s
a c q u i r e c o n s i d e r a b l e t h i c k n e s s ( ~ i g . 1 8 ) . A l t h o u g h s t a c k s o f
d i c t y o s o m e l a m e l l a e a r e r a r e l y f o u n d a l o n g t h e p l a s m a l e m m a ,
t h e r e a r e n u m e r o u s s m o o t h - s u r f a c e d v e s i c l e s , w h i c h c o u l d b e
d e r i v e d f r o m t h e s m o o t h ER o r d i c t y o s o m e s , w h i c h show i n t i m a t e
r e l a t i o n s h i p w i t h t h e p l a s m a membrane ( F i g s . 2 6 , 2 7 ) .
S e q u e n t i a l l y , * w i t h t h e m a t u r a t i o n o f t h e s i e v e e l e m e n t s , t h e
d i c t y o s o m e s show f e w e r l a m e l l a e , a p p e a r t o b e d e g r a d e d ( F i g . 2 5 )
and d i s a p p e a r e n t i r e l y .
E n d o p l a s m i c r e t i c u l u m (ER) a n d r i b o s o m e s --
T h e r e i s a n i n c r e a s e i n b o t h ER a n d r i b o s o m e s i n t h e
c y t o p l a s m f r o m S1 t o S 2 . S e g m e n t s o f ER l a m e l l a e s t u d d e d w i t h
r i b o s o m e s , r o u g h o r g r a n u l a r E R , a r e common ( F i g . 1 7 ) . H o w e v e r ,
a l a r g e p r o p o r t i o n o f t h e r i b o s o m e s e x i s t f r e e l y i n t h e
c y t o p l a s m o f t h e y o u n g s i e v e e l e m e n t s .
S m o o t h E R i s a l s o a b u n d a n t i n t ' h e c y t o p l a s m , p a r t i c u l a r l y
n e a r t h e p l a sma lemma. E v e n i n t h e c o r t i c a l c e l l s , t h e s m o o t h ER
s h o w s t h i s r e l a t i o n s h i p , e s p e c i a l l y , a t t h e p r i m a r y p i t f i e l h s
( F i g . 3 4 ) . The same a s s o c i a t i o n i s u b i q u i t o u s f o r t h e y o u n g ,
d e v e l o p i n g s i e v e p l a t e s ( F i g s . 2 9 , 3 5 ) . A s t h e p h e n o m e n o n o f
p e r f o r a t i o n o f t h e s i e v e p l a t e commences i n t h e S 3 s t a g e ,
4 5
![Page 72: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/72.jpg)
F i g . 2 6 . S u r f a c e p a r a l l e l s e c t i o n t h r o u g h t h e i n t e r f a c e b e t w e e n t h e p l a s m a l e m m a a n d t h e i n n e r m o s t w a l l l a y e r o f S 3 , Numerous s m o o t h E R c i s t e r n a e l i e a l o n g t h e p l a sma lemma w h i c h a l s o a p p e a r s h i g h l y c o n v o l u t e d . N o t e s e v e r a l d e n s e p a t c h e s ( a r r o w s ) w h i c h s e e m t o b e made u p o f w a l l f i b r i l s i n c o r p o r a t i n g t o t h e e x i s t i n g c e l l w a l l . . . . . . . . . , . . . ~ 1 5 , 0 0 0
F i g . 2 7 , ' ~ o n ~ i t u d i n ' a l s e c t i o n o f t w o S 3 s i e v e e l e m e n t s s h o w i n g a f u t u r e p o r e s i t e (PS). S m o o t h E R a n d s m a l l v e s i c l e s a r e n o t o n l y a b u n d a n t a l o n g t h e c r o s s w a l l b u t a l s o a l o n g t h e s i d e w a l l s ( a r rows ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ 1 0 , 0 0 0
F i g . 2 8 . C r o s s s e c t i o n o f a m a t u r e S 4 s i e v e e l e m e n t s h o w i n g , p a r i e t a l c y t o p l a s m i c o r g a n e l l e s a n d s e c o n d a r y w a l l . . x15,OSlQ
![Page 73: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/73.jpg)
![Page 74: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/74.jpg)
E R - l i k e s t r u c t u r e s s eem t o a p p e a r i n t h e p o r e c a n a l s ( F i g . 3 6 ) .
When t h e s i e v e p l a t e s become p e r f o r a t e d ( a t t h e S4 s t a g e ) , t h e
s m o o t h ER c i s t e r n a e l i n i n g t h e c r o s s w a l l s a p p e a r d i s o r g a n i z e d
a n d d i s a p p e a r e v e n t u a l l y ; a t t h e s ame t i m e m o s t o f t h e c y t o p l a s m
o f t h e s e s i e v e e l e m e n t s , i n c l u d i n g r i b o s o m e s a n d r o u g h ER, i s
a l s o l o s t . N e v e r t h e l e s s , a l a r g e n u m b e r o f s m o o t h E R - l i k e
m e m b r a n e s a n d p r o b a b l y E R - d e r i v e d v e s i c l e s w h i c h o c c u r
c h a r a c t e r i s t i c a l l y a l o n g t h e s i d e w a l l s o f t h e d e v e l o p i n g s i e v e
e l e m e n t s p e r s i s t s i n t h e m a t u r e s i e v e e l e m e n t s ( S 4 ) ( F i g . 2 8 ) -
V a c u o l e s
One o f t h e m o s t e x c e p t i o n a l f e a t u r e s o f t h e d e v e l o p i n g
s i e v e e l e m e n t i s t h e h i g h l y v a c u o l a t e d p r o t o p l a s m . U n l i k e t h e
c o r t i c a l c e l l w h i c h h a s a s i n g l e , l a r g e , c e n t r a l v a c u o l e , t h e r e
a r e many r e l a t i v e l y s m a l l v a c u o l e s e v e n l y d i s t r i b u t e d i n t h e
y o u n g s i e v e e l e m e n t s ( F i g s . 1 5 , 18) . T h e o r i g i n o f t h e s e
v a c u o l e s i s n o t c l e a r . I t i s p o s s i b l e t h a t t h e o r i g i n a l s i n g l e
v a c u o l e b r e a k s down t o g i v e r i s e t o t h e s m a l l e r v a c u o l e s , b u t
t h a t d o e s n o t s e e m t o b e t h e o n l y s o u r c e , f o r t h e c e l l v o l u m e o f
t h e e l o n g a t i n g s i e v e e l e m e n t i n c r e a s e s more t h a n 150 t imes t h a t
o f t h e o r i g i n a l e l e m e n t .
E a c h v a c u o l e i s b o u n d e d by a s i n g l e u n i t membrane , o r
47
![Page 75: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/75.jpg)
t o n o p l a s t . G e n e r a l l y , t h e v a c u o l e s a p p e a r f r e e f r o m a n y
i n c l u s i o n s ( F i g s . 1 5 , 1 8 ) . I n t h e S 3 s t a g e , when m o s t o f t h e
c y t o p l a s m i s l o s t , t h e v a c u o l e s a p p e a r t i g h t l y p a c k e d i n t h e
c e l l l u m e n ( ~ i g . 2 3 ) . The t o n o p l a s t s e e m s t o b r e a k down
e v e n t u a l l y i n S 4 s i e v e e l e m e n t s ( F i g s . 2 8 , 3 8 ) .
M i t o c h o n d r i a
M i t o c h o n d r i a show v e r y f e w s t r u c t u r a l c h a n g e s d u r i n g t h e
d i f f e r e n t i a t i o n o f s i e v e e l e m e n t s a n d a r e p r e s e n t i n t h e m a t u r e ,
f u n c t i o n a l e l e m e n t s . They v a r y f r o m s p h e r i c a l t o c y l i n d r i c a l i n
f o r m , a n d a r e a b o u t 0 .4-1 .3 um i n d i a m e t e r . E l e c t r o n - l i g h t
a r e a s , w h i c h s e e m t o b e i n t e r c o n n e c t e d , w i t h i n t h e m i t o c h o n d r i a l
m a t r i x h a r b o r some r a d i a t i n g f i n e t h r e a d s p r e s u m a b l y D N A f i b e r s
( F i g . 3 0 ) . O t h e r c o m p o n e n t s o f m i t o c h o n d r i a , e . g . , m i t o c h o n d r i a l
r i b o s o m e s , a n d s m a l l o s m i o p h i l i c g l o b u l e s a r e a l s o common i n t h e
m a t r i x .
A s t h e d i f f e r e n t i a t i o n o f s i e v e e l e m e n t p r o g r e s s e s ,
m i t o c h o n d r i a r e t a i n t h e i r u s u a l s h a p e a n d b a s i c s t r u c t u r e s , b u t
s eem t o show l e s s g r o u n d m a t r i x a n d a s m a l l e r number o f c r i s t a e
( F i g . 2 8 ) . Most m i t o c h o n d r i a s e e m t o b e l o c a t e d a r o u n d t h e c e l l
p e r i p h e r y , t h o u g h some a r e a l s o p r e s e n t i n t h e more c e n t r a l p a r t
o f t h e c e l l . P a r t i c u l a r l y n o t i c e a b l e i s t h e a s s o c i a t i o n o f
![Page 76: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/76.jpg)
m i t o c h o n d r i a w i t h t h e y o u n g d e v e l o p i n g s i e v e p l a t e s ( ~ i g s . 3 5 ,
3 6 ) . When t h e s i e v e p l a t e s a r e m a t u r e d , m i t o c h o n d r i a a r e
o c c a s i o n a l l y s e e n i n t h e v i c i n i t y o f t h e p l a t e s , b u t t h e y a r e
o f t e n f o u n d a l o n g t h e s i d e w a l l s ( F i g . 2 8 ) .
P l a s t i d s
I n g e n e r a 1 , p l a s t i d s a r e l e n s - s h a p e d , o r e l l i p s o i d
s t r u c t u r e s ( F i g . 3 1 ) a b o u t 3 .4 X 1 .2 um, b u t may become
e l o n g a t e d a n d r o d - s h a p e d d u r i n g t h e i n t e r m e d i a t e s t a g e s ( e . g . ,
i n t h e S 3 s t a g e ; F i g . 3 2 ) . I n t h e m a t u r e s i e v e e l e m e n t , p l a s t i d s
become s m a l l e r i n s i z e a n d a p p e a r f e w e r i n number . P l a s t i d s a r e
a l s o e n c l o s e d by a d o u b l e membrane e n v e l o p e ; i n a d d i t i o n , t h e y
a r e s u r r o u n d e d by a n E R membrane ( F i g s . 3 1 , 3 2 ) . The t h y l a k o i d
l a m e l l a e a r e s t a c k e d i n g r o u p s o f 3 a n d f o r m u n i t s w h i c h r u n
p a r a l l e l t o e a c h o t h e r a l o n g t h e l o n g a x i s o f t h e o r g a n e l l e , b u t
t h e s e p a r a l l e l t h y l a k o i d u n i t s may b r a n c h a n d b e i n t e r c o n n e c t e d .
The p l a s t i d s t r o m a i s r a t h e r d e n s e i n t h e y o u n g s i e v e e l e m e n t
a n d c o n t a i n s many r i b o s o m e - l i k e p a r t i c l e s a n d some o s m i o p h i l i c
d r o p l e t s ( ~ i g s . 3 1 , 3 2 ) . Many e l e c t r o n d e n s e b o d i e s , somewha t
d e n s e r t h a n t h o s e i n t h e m a t r i x , s e e m t o e x u d e o u t a n d p r o b a b l y
a r e r e l e a s e d f r o m t h e o u t e r membrane o f t h e p l a s t i d s . W h e t h e r
t h e s e c o n t r i b u t e t o t h e e l e c t r o n - o p a q u e b o d i e s ( F i g . 3 0 , ~ b ) ,
![Page 77: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/77.jpg)
F i g . 29 . L o n g i t u d i n a l s e c t i o n o f t w o a d j a c e n t s i e v e e l e m e n t s i n t h e l a t e S 1 s t a g e s h o w i n g p l a s m o d e s m a t a i n the c r o s s w a l l . M i c r o b o d i e s a r e u s u a l l y f o u n d a l o n g t h e c r o s s w a l l o f y o u n g s i e v e e l e m e n t s . N o t e a l s o t h e s m o o t h ER ( a r r o w h e a d s ) a n d mitochondria.................................,,..... ~ 2 4 , 0 0 0
F i g . 3 0 . M i t o c h o n d r i a show e l e c t r o n - l i g h t a r e a s w h i c h h a r b o r f i n e t h r e a d s p r e s u m b a b l y D N A f i b r i l s ( a r r o w s ) , S m a l l o s m i o p h i l i c g l o b u l e s ( a r r o w h e a d s w i t h w h i t e sm:all a r r o w s ) a r e common i n t h e i r m a t r i x . An e l e c t r o n - o p a q u e b o d y (Ob) w i t h o u t a s u r r o u n d i n g membrane i s p r e s e n t . . . . , , . . . . . ~ 2 4 , 0 0 0
F i g . 3 1 . A t y p i c a l l e n s - s h a p e d p l a s t i d o f S 1 s i e v e e l e m e n t s h o w s a d e n s e s t r o m a , r i b o s o m a l p a r t i c l e s a n d e l e c t r o n - d e n s e d r o p l e t s , T h y l a k c i d b a i i 2 s a r e u s u a l l y i n s t a c k o f 3 l a m e l l a e . A t e a c h e n d of t h e l o n g a x i s o f t h e ? l a s t i d t h e r e a r e e l e c t r o n - l i g h t a r e a s p o s s e s s i n g DNA- thread.^. N o t e t h e s u r r o u n d i n g E R membrane a n d t h e o s m i o p h i l i c a g ; . g r e g a t e s a t t h e p e r i p h e r y of t h e p l a s t i d ........................ ~ 2 7 , 0 0 0
F i g . 3 2 . An e l o n g a t e d p l a s t i d i n S 3 . N o t e t h a t i n a d d i t i o n t o t h e p l a s t i d e n v e l o p e t h e p l a s t i d i s f u t h e r s u r - r o u n d e d by a ' E R membrane , s o c a l l e d p l a s t i d ER membrane . . . . - . . . . . ~ 1 6 , 0 0 0
F i g . 3 3 . An e n l a r g e d l a m e l l a r b o d y s h o w i n g c o n c e n t r i c membranes . ~ 1 6 , 0 0 0
![Page 78: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/78.jpg)
![Page 79: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/79.jpg)
s e e n i n o l d e r s t a g e s o f s i e v e e l e m e n t d e v e l o p m e n t , i s n o t c l e a r .
E l e c t r o n - l i g h t r e g i o n s a t o r a r o u n d t h e e d g e s o f t h e p l a s t i d
show f i n e f i b r i l l a r s t r u c t u r e s w h i c h a r e b e l i e v e d t o b e D N A
( ~ i g s . 3 1 , 3 2 ) .
O t h e r o r g a n e l l e s
M i c r o b o d i e s o c c u r i n t h e d i f f e r e n t i a t i n g s i e v e e l e m e n t s a n d
j u d g i n g f r o m i s o l a t e d s e c t i o n s t h e y a r e l e s s f r e q u e n t t h a n
m i t o c h o n d r i a a n d p l a s t i d s . T h e y a r e s m a l l e r t h a n m i t o c h o n d r i a
a n d a r e e n c l o s e d by a s i n g l e u n i t membrane . The i n t e r n a l m a t r i x
o f t h e m i c r o b o d y i s f a i r l y d e n s e a n d s h o w s a g r a n u l a r t e x t u r e
( F i g . 2 9 ) . M i c r o b o d i e s h a v e b e e n s e e n m o s t l y i n a s s o c i a t i o n w i t h
t h e y o u n g , d e v e l o p i n g s i e v e p l a t e s , s e l d o m i n o t h e r l o ' c a t i o n s .
They d i s a p p e a r i n t h e f u l l y m a t u r e s i e v e e l e m e n t s .
T h e r e a r e a l s o o t h e r s t r u c t u r e s o f unknown o r i g i n a n d
n a t u r e w h i c h s e e m t o o c c u r m o r e o f t e n i n t h e l a t e r t h a n e a r l i e r
s t a g e s o f s i e v e e l e m e n t d i f f e r e n t i a t i o n . T h e s e a r e
e l e c t r o n - o p a q u e b o d i e s a n d c o n c e n t r i c m y e l i n - l i k e l a m e l l a r
b o d i e s ( F i g . 3 0 , Ob a n d F i g . 3 3 , L b ) . T h e f o r m e r , w h i c h i s a i s o
r e p o r t e d i n t h e s i e v e e l e m e n t o f some o t h e r b r o w n a l g a e ( S c h m i t z
a n d S r i v a s t a v a , 1 9 7 4 b ) i s n o t d e l i m i t e d b y a membrane . The
l a m e l l a r body s h o w s v a r y i n g n u m b e r s o f c o n c e n t r i c r i n g s o f
![Page 80: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/80.jpg)
l a m e l l a e s u r r o u n d i n g a c e n t r a l c o r e . M o r e o v e r , s m a l l s p e c k l e s
s e e m t o b e d i s p e r s e d r a n d o m l y o n t h e l a m e l l a r membranes ( F i g -
33 ) .
IV-2. D e v e l o p m e n t o f s i e v e p l a t e s -
O b s e r v a t i o n s w i t h l i g h t m i c r o s c o p e
W h i l e t h e r e i s a n i n c r e a s e i n t h e a m o u n t o f c y t o p l a s m
a c c o m p a n y i n g t h e e n l a r g e m e n t o f y o u n g s i e v e e l e m e n t s i n S1 a n d
S 2 , t h e r e i s a l s o a n i n c r e a s e i n s y n t h e s i s o f w a l l m a t e r i a l .
T h i s i s r e f l e c t e d f i r s t by a n i n c r e a s e i n a r e a o f t h e e n d w a l l ,
n e c e s s a r y b e c a u s e o f a n i n c r e a s e i n c e l l w i d t h , a n d s e c o n d by a
g e n e r a l i n c r e a s e i n t h e t h i c k n e s s o f t h e e n d w a l l . A n o t h e r
n o t i c e a b l e phenomenon i s t h a t t h e c i r c u l a r p r i m a r y p i t f i e l d s
a r r a n g e d i n a r i n g a t t h e p h e r i p h e r y o f t h e c r o s s w a l l s o f t h e
c o r t i c a l c e l l s ( F i g . 12) a r e n o l o n g e r f o u n d f r o m S1 o n w a r d -
P o r e s i t e s o n t h e c r o s s w a l l s b e g i n t o become d e t e c t a b l e a t
S3 s t a g e , when n u c l e i i n t h e s e c e l l s h a v e a l r e a d y s t a r t e d t o
u n d e r g o t h e i r r e v e r s i b l e d i s o r g a n i z a t i o n ( s e e P a r t C-IV-1). T h i n
t h r e a d s of c y t o p l a s m t h a t c o n n e c t t h e t w o s u p e r i m p o s e d s i e v e
e l e m e n t s c a n b e s e e n r u n n i n g t h r o u g h t h e s e p r e s u m a b l e p o r e a r e a s
![Page 81: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/81.jpg)
( F i g . 5 , S 3 ) . T h e s e f u t u r e s i e v e - p l a t e p o r e s w h i c h c a n b e
m e a s u r e d a r e on t h e a v e r a g e 0 .05 urn i n d i a m e t e r . U n l i k e w h a t h a s
b e e n r e p o r t e d f o r some h i g h e r v a s c u l a r p l a n t s , c a l l o s e was n e v e r
d e t e c t e d a t t h e s e d e v e l o p i n g p o r e s i t e s by a n i l i n e b l u e
s t a i n i n g . I n t h e f o l l o w i n g S4 s t a g e , d i f f e r e n t d e g r e e s o f
p e r f o r a t i o n o f t h e s i e v e p l a t e s a r e f o u n d ( ~ i g s . 5 , 1 3 ) . I t h a s
b e e n m e n t i o n e d e a r l i e r t h a t d i f f e r e n t i a t i o n o f s i e v e e l e m e n t s
p r o c e e d s r a p i d l y i n t h e v e r y y o u n g p a r t o f a s t i p e , t h e e a r l y
f o r m e d s i e v e e l e m e n t s u s u a l l y h a v e s m a l l e r s i e v e p o r e s (Ave.
d i a m e t e r 0 . 4 5 um) w h i c h become p l u g g e d w i t h c a l l o s e . I n t h e
l a t e r f o r m e d s i e v e e l e m e n t s , h o w e v e r , p o r e s a r e i n t h e r a n g e o f
0 .6 - 4.5 um i n d i a m e t e r .
M a t u r e s i e v e e l e m e n t s o f - M . i n t e g r i f o l i a h a v e s i m p l e s i e v e
p l a t e s w i t h r e l a t i v e l y l a r g e p o r e s o n t h e i r e n d w a l l s ( F i g s . 1 3 ,
1 4 ) . A r e a s o f e n d w a l l b e t w e e n t h e p o r e s c o n t i n u e t o i n c r e a s e i n
t h i c k n e s s , b u t t h e y n e v e r r e a c h t h e s a m e d e g r e e o f t h i c k n e s s
t h a t t h e l a t e r a l w a l l s do. A l t h o u g h a p o s i t i v e c a l l o s e r e a c t i o n
was n e v e r o b t a i n e d i n y o u n g a n d m a t u r e s i e v e e l e m e n t s , h e a v y
d e p o s i t i o n o f c a l l o s e was r e a d i l y f o u n d a t s i e v e p l a t e s a n d
s o m e t i m e s i n c e l l l u m i n a o f o l d s i e v e e l e m e n t s i n t h e c e n t r a l
m e d u l l a , p a r t i c u l a r l y o f o l d s t i p e s ( F i g s . 6 , 7 ) .
![Page 82: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/82.jpg)
O b s e r v a t i o n s w i t h e l e c t r o n m i c r o s c o p e
Some c h a r a c t e r i s t i c f e a t u r e s o f t h e y o u n g s i e v e p l a t e s , o r
f u t u r e s i e v e p l a t e s , a r e r e c o g n i z a b l e a s e a r l y a s i n s t a g e S 1 .
F i g u r e 3 5 , a l o n g i t u d i n a l s e c t i o n o f t w o S 1 s i e v e e l e m e n t s ,
shows t h a t t h e c r o s s w a l l i s i n t e r r u p t e d by n u m e r o u s
p l a s m o d e s m a t a . The p l a s m o d e s m a t a a r e e v e n l y d i s p e r s e d t h r o u g h o u t
t h e c r o s s w a l l a n d a r e n o l o n g e r c o n f i n e d t o t h e p r i m a r y p i t
f i e l d s , t y p i c a l o f c o r t i c a l c e l l s ( F i g . 3 4 ) . C o n s e q u e n t l y , t h e s e
p l a s m o d e s m a t a m u s t b e f o r m e d d e n o v o a t t h e t i m e when i n n e r m o s t -- c o r t i c a l c e l l s a r e c o m m i t t e d t o d i f f e r e n t i a t e i n t o s i e v e
e l e m e n t s . A p l a s m o d e s m a o f S 1 h a s t h e same s t r u c t u r e a s t h a t o f
t h e c o r t i c a l c e l l : a c a n a l l i n e d w i t h p l a s m a l e m m a , w h i c h i s
c o n t i n u o u s b e t w e e n t w o n e i g h b o r i n g c e l l s , a n d a c e n t r a l t u b u l e
( c f . F i g . 39 a n d F i g . 4 0 ) . S e g m e n t s o f s m o o t h E R c i s t e r n a e a r e
s e e n l i n i n g a g a i n s t t h e p l a s m a l e m m a o n b o t h s i d e s o f t h e e n d
w a l l , b u t n o c l e a r c o n n e c t i o n s b e t w e e n E R c i s t e r n a e a n d
p l a s m o d e s m a t a w e r e s e e n i n S 1 .
A s d i f f e r e n t i a t i o n p r o c e e d s , a n d t h e r e i s a p r o l i f e r a t i o n
o f t h e c y t o p l a s m , t h e c e n t r a l t u b u l e s o f t h e p l a s m o d e s m a t a i n S2
s e e m t o show d e n s e r c o n t e n t s , b u t no s u b c e l l u l a r s t r u c t u r e c a n
b e i d e n t i f i e d i n them. The s i z e o f t h e p l a s m o d e s m a t a ( c a . 0.05
um i n d i a m e t e r ) a l s o r e m a i n s t h e same a s t h a t i n t h e p r e v i o u s
s t a g e ( F i g s . 3 5 , 3 6 ) . H o w e v e r , s e v e r a l f e a t u r e s o f t h e y o u n g
s i e v e p l a t e s a r e n o t e w o r t h y . F i r s t , t h e membrane s y s t e m s ,
e s p e c i a l l y , E R c i s t e r n a e a n d s m a l l v e s i c l e s a r e p r o f u s e a n d s h o w
![Page 83: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/83.jpg)
i n t i m a t e a s s o c i a t i o n w i t h p l a s m a l e m m a n o t o n l y o n e n d w a l l s b u t
a l s o a l o n g t h e l a t e r a l w a l l s ( ~ i g s . 2 6 , 2 7 ) . The p o s s i b l e
o r i g i n s a n d r o l e s o f t h e s e membrane s y s t e m s , c o n t r i b u t i n g t o t h e
g r o w t h o f c e l l w a l l s , o f t h e v e s i c l e s h a v e b e e n c o n s i d e r e d i n
P a r t C-IV-2. S e c o n d l y , i n a g i v e n s e c t i o n , i t i s a l w a y s f o u n d
t h a t a g o o d many o f m i t o c h o n d r i a a r r a y a l o n g b o t h s i d e s o f t h e
c r o s s w a l l ( F i g . 3 6 ) . C o m p a r i n g t h e s u r f a c e v i e w s o f t h e c r o s s
w a l l s o f S 2 ( F i g . 4 0 ) and . c o r t i c a l c e l l ( F i g . 3 9 ) , i t i s c l e a r
t h a t l o o s e n i n g , a n d p o s s i b l y some r e o r i e n t a t i o n o f p r i m a r y w a l l
m a t e r i a l m u s t h a v e o c c u r r e d a n d p r o b a b l y new w a l l m a t e r i a l was
c o n c o m i t a n t l y a d d e d o n . W a l l f i b r i l s a r o u n d t h e p l a s m o d e s m a t a
h a v e a c o n c e n t r i c o r i e n t a t i o n . F u r t h e r m o r e , t h e d e n s i t y o f t h e
p l a s m o d e s m a t a d r o p s s h a r p l y f r o m a b o u t 1 0 0 / u m 2 i n t h e p i t f i e l d s
o f c o r t i c a l c e l l s t o 16 /um2 i n t h e c r o s s w a l l ' o f S 2 . T h e
d e v e l o p i n g s i e v e p l a t e c o n t i n u e s t o i n c r e a s e i n w a l l t h i c k n e s s
i n t h e f o l l o w i n g s t a g e s ( f r o m 0 .2 um i n S 1 t o 0 .8 um i n S 3 ) .
S i m u l t a n e o u s l y w i t h t h e s e c h a n g e s i n t h e e n d w a l l , t h e l a t e r a l
w a l l s a l s o c o n t i n u e t o i n c r e a s e i n t h i c k n e s s . I n t h e s e l a t e r a l
w a l l s , m i c r o f i b r i l s o f t h e i n n e r m o s t r e g i o n , c l o s e s t t o t h e
p l a s m a l e m m a , show a p r e f e r r e d h o r i z o n t a l o r i e n t q t i o n ( F i g s . 18 ,
The a u t o p h a g i c d i s s o l u t i o n o f c y t o p l a s m ( P a r t C-IV-2) a n d
p e r f o r a t i o n o f f u t u r e s i e v e p l a t e s s e e m t o t a k e p l a c e
s i m u l t a n e o u s l y a n d f o l l o w t h e p e a k o f p r o t o p l a s m i c s y n t h e s i s .
The s i e v e - p l a t e p o r e c a n a l s i n S 3 a r e a p p r o x i m a t e l y 4 t i m e s
w i d e r t h a n t h o s e i n S2 a n d a r e t r a v e r s e d by t h i c k c y t o p l a s m i c
![Page 84: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/84.jpg)
F i g . 3 4 . C r o s s w a l l o f t w o n e i g h b o r i n g i n n e r c o r t i c a l c e l l s s h o w i n g t h r e e p r i m a r y p i t f i e l d s ( a r r o w s ) . N o t e a t h i n s h e a t h o f p a r i e t a l c y t o p l a s m a n d a l a r g e c e n t r a l v a c u o l e . . . . . x 1 0 , 2 0 0
F i g . 35. C r o s s w a l l % e t w e e n t w o S 1 s i e v e e l e m e n t s . P l a s m o d e s m a t a a r e n o l o n g e r c o n f i n e d t o t h e p r i m a r y p i t f i e l d . C y t o p l a s m o f t h e c o n t i g u o u s c e l l s i s c o n n e c t e d t h r o u g h the t u b u l e s o f t h e p l a s m o d e s m a t a . . . . . . . . . . . . . . . ..................... ~ 2 4 , 0 0 0
F i g . 36 . L o n g i t u d i n a l s e c t i o n o f t w o a d j a c e n t S2 s i e v e e l e m e n t s , w i t h many p l a s m o d e s m a t a t r a v e r s i n g t h e c r o s s w a l l . N o t e t h e a s s o c i a t i o n o f s m o o t h E R a n d m i t o c h o n d r i a w i t h t h e c r o s s wall................................................. ~ 1 0 ~ 2 0 0
![Page 85: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/85.jpg)
![Page 86: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/86.jpg)
s t r a n d s w h i c h s e e m t o c o n t a i n E R m e m b r a n e s ( F i g s . 3 7 , 4 1 ) . T h e r e
a r e a l s o v a r i o u s s i z e s o f e l e c t r o n - d e n s e g l o b u l e s i n a n d a t t h e
o r i f i c e o f t h e p o r e c a n a l s . T h e i r s i g n i f i c a n c e i n r e l a t i o n t o
t h e t h e p e r f o r a t i o n o f s i e v e p l a t e i s unknown.
I n t h e n e x t S4 s t a g e , p e r f o r a t e d s i e v e p l a t e s a r e f o u n d .
S e c t i o n s o f t h e m a t u r e s i e v e p l a t e s o f S4 o f t e n r e v e a l r u p t u r e d
v a c u o l e s a n d b r o k e n s e g m e n t s o f p l a s m a l e m m a a r o u n d t h e
s i e v e - p l a t e p o r e s ( F i g s . 3 8 , 4 2 ) . T h e s e a r e p r o b a b l y f i x a t i o n
a r t e f a c t s w h i c h a r i s e b e c a u s e t h e m e m b r a n e s a r e now more
f r a g i l e .
V. L o c a l i z a t i o n o f 1 4 c - l a b e l e d a s s i m i l a t e s i n s i e v e e l e m e n t s by
h i s t o a u t o r a d i o g r a p h y
I n t h e 1 4 c f e e d i n g e x p e r i m e n t , t h e s o u r c e b l a d e was 1 1 0 cm
b e l o w t h e a p i c a l s c i m i t a r . The p r o f i l e o f r a d i o a c t i v i t y r e v e a l e d
t h a t t h e t r a n s l o c a t i o n o f 1 4 c l a b e l w a s b o t h a c r o p e t a l a n d
b a s i p e t a l a n d t h a t t h e downward movement was p r e f e r r e d ( F i g .
4 3 ) . F o r h i s t o a u t o r a d i o g r a p h y , t h e f i r s t 3 cm s e g m e n t s o f t h e ,
s t i p e b e l o w t h e s o u r c e b l a d e , w h i c h s h o w e d t h e h i g h e s t
r a d i o a c t i v i t y , was s t u d i e d i n d e t a i l .
The h i s t o a u t o r a d i o g r a p h s show t h a t t h e l a b e l i s c o n f i n e d t o
c e r t a i n l o n g i t u d i n a l f i l e s o f s i e v e e l e m e n t s a t t h e p e r i p h e r y o f
![Page 87: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/87.jpg)
F i g . 3 7 . L o n g i t u d i n a l s e c t i o n o f c r o s s w a l l of S 3 showin-g t h r e e f u t u r e p o r e s i t e s . N o t e E R l i k e t u b u l e s ' ( a r r o w s ) t r a v e r s i n g t h e p o r e c a n a l s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ 3 0 , 0 0 0
F i g . 3 8 . L o n g i t u d i n a l s e c t i o n o f a s i e v e p l a t e of S 4 s h o w i n g l a r g e , open s i e v e p o r e s . Membrane f r a g m e n t s i n t h e p o r e c a n a l s may be a f i x a t i o n a r t i f a c t . . . . . . . . . . . . . . . . . . . . ~ 6 , 6 0 0
![Page 88: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/88.jpg)
![Page 89: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/89.jpg)
F i g . 3 9 . O b l i q u e s e c t i o n t h r o u g h a p i t f i e l d o f a n i n n e r c o r t i c a l c e l l . E a c h p l a s m o d e s m a i s l i n e d w i t h p l a s m a l e m m a . N o t e t h e ER t u b u l e s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ 7 1 , 5 0 0
F i g . 40 . O b l i q u e s u r f a c e - p a r a l l e l s e c t i o n t h r o u g h a n e n d w a l l o f S2 . T h e p l a s m o d e s m a t a a r e n o d i f f e r e n t f r o m t h o s e i n t h e p i t f i e l d o f c o r t i c a l c e l l s e x c e p t t h e d e n s i t y p e r u n i t a r e a d r o p s d r a s t i c a l l y i n t h e f o r m e r ( f r o m 1 0 0 t o 16 / u m 2 ) . N o t e t h e l o o s e n e d w a l l fibrils... . . . . . . . . . . . . . . . . . . . . . . . . ~ 7 0 , 0 0 0
F i g . 4 1 . S u r f a c e p a r a l l e l s e c t i o n t h r o u g h a n end w a l l o f S 3 . N o t e t h e r a g g e d o u t l i n e s o f t h e f u t u r e s i e v e p o r e s a n d h i g h l y c o n v o l u t e d p l a s m a l e m m a ; a l s o , t h e c i r c u l a r orientaticn o f wall f i b r i l s a r o u n d t h e f u t u r e p o r e s , ~ 2 0 , 0 0 0
F i g . 42 . S u r f a c e v i e w o f a s i e v e p l a t e o f S4 . N o t e t h e c i r c u l a r o r i e n t a t i o n o f w a l l f i b r i l s s u r r o u n d i n g t h e p o r e s . . . . ~ 5 , 0 0 0
![Page 90: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/90.jpg)
![Page 91: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/91.jpg)
F i g . 4 3 . , P r o f i l e o f 1 4 c r a d i o a c t i v i t y i n a s t i p e s e g m e n t 2 0 cm a b o v e a n d b e l o w t h e l a b e l e d b l a d e i n a f r o n d o f M. i n t e g r i f o l i a . 2 .2 m C i o f ~ a ~ ~ ~ ~ 0 ~ w a s s u p p l i e d t o d e s i g n a t e d b l a d e f o r 3 h. F o l l o w i n g t h a t , 2 mm t h i c k s l i c e s o f t h e s t i p e w e r e q u i c k l y c u t , f r o z e n i n d r y i c e , f r e e z e - d r i e d , w e i g h e d , a n d c o r n b u s t e d i n a P a c k a r d o x i d i z e r . The e v a p o r a t e d I 4 c o 2 w a s t r a p p e d by 2 - p h e n y l e t h y l a m i n e (Koch-Light-~aboratories L t d . , B u c k s . , E n g . ) . R a d i o a c t i v i t y was c o u n t e d i n a Beckman s c i n t i l l a t i o n c o u n t e r a n d c o n v e r t e d f o r dpm.
![Page 92: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/92.jpg)
![Page 93: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/93.jpg)
F i g . 4 4 . G e n e r a l v i e w o f t h e s t i p e 3 cm b e l o w t h e 14c l a b e l e d b l a d e shown i n F i g . 4 3 . The arrow i n d i c a t e s t h e p o s i t i o n o f t h e f e d b l a d e . R a d i o a c t i v i t y o n l y a p p e a r s i n t h o s e s i e v e e l e m e n t s t h a t w e r e b e n e a t h t h e f e d b l a d e . The a r e a o u t l i n e d by a b l a c k l i n e i s shown i n F i g . 45. . . . . . . . . . . . . . . . . . . . . x35
![Page 94: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/94.jpg)
![Page 95: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/95.jpg)
F i g . 4 5 . ist to auto radiograph s h o w s s i l v e r g r a i n s w h i c h c o n c e n t r a t e d a b o v e c e r t a i n p e r i p h e r a l s i e v e e l e m e n t s i n t h e m e d u l l a i n t h i s c r o s s s e c t i o n . The l i n e p a s s i n g t h r o u g h o n e r a d i a l row of s i e v e e l e m e n t s i n d i c a t e s t h e s e c t i o n p l a n e c o m p a r a b l e t o t h a t of F i g . 4 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . x 1 6 5
![Page 96: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/96.jpg)
![Page 97: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/97.jpg)
t h e m e d u l l a ( F i g s . 4 4 , 4 5 ) . T h e s e l o n g i t u d i n a l f i l e s c o r r e s p o n d
t o t h e s ame s i d e o f s t i p e o n w h i c h t h e f e d b l a d e w a s l o c a t e d
( ~ i g . 4 4 ) . T h i s p a t t e r n o f r a d i o a c t i v i t y i n t h e t r a n s l o c a t i n g
r e g i o n b e l o w t h e s o u r c e b l a d e i n d i c a t e s t h a t o n l y s p e c i f i c s i e v e
e l e m e n t s a r e i n v o l v e d i n t r a n s l o c a t i o n o f a s s i m i l a t e s f r o m
s p e c i f i c s o u r c e b l a d e s . T h e r e a r e n o a p p r e c i a b l e s i l v e r g r a i n s
a b o v e b a c k g r o u n d i n t h e c o r t e x , i n t h e c e l l l a y e r s o f t h e
m e d u l l a i n c l u d i n g t h e y o u n g e s t f i l e ( I i n F i g . 4 6 ) o f s i e v e
e l e m e n t s , i n t h e o l d e s t s i e v e e l e m e n t s i n t h e c e n t r a l p a r t o f
t h e m e d u l l a , o r i n t h e h y p h a l c e l l s .
The s i e v e e l e m e n t s t h a t show a p p r e c i a b l e a m o u n t s o f l a b e l
c o r r e s p o n d t o w h a t I h a v e e a r l i e r d e s c r i b e d a s s i e v e e l e m e n t s i n
s t a g e S4 ( F i g . 5 ) . A s a r u l e , s i e v e e l e m e n t s i n f i l e I1 show
l e s s e r l a b e l t h a n t h o s e i n f i l e 111, a n d t h e maximum l a b e l i s
s e e n i n t h e f i l e I V ( F i g . 4 6 ) . S u c h a d i s t r i b u t i o n o f l a b e l
s e e m s t o i n d i c a t e a c o r r e l a t i o n b e t w e e n t h e s t a g e s o f
d i f f e r e n t i a t i o n o f s i e v e e l e m e n t s , a n d t h e i r c a p a c i t y f o r
t r a n s p o r t o f p h o t o a s s i m i l a t e s . C r o s s c o n n e c t i o n s b e t w e e n m a t u r e
s i e v e e l e m e n t s a l s o show a p p r e c i a b l e 1 4 c l a b e l ( ~ i g . 4 7 ) w h i c h
s u g g e s t s t h a t a l a t e r a l movement o f a s s i m i l a t e s f r o m o n e s i e v e
e l e m e n t t o a n o t h e r i s a l s o o p e r a t i v e .
![Page 98: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/98.jpg)
![Page 99: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/99.jpg)
![Page 100: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/100.jpg)
D. DISCUSSION
I t i s g e n e r a l l y r e c o g n i z e d f r o m t h e e a r l i e s t s t u d i e s ( W i l l ,
1 8 8 4 ; R o s e n t h a l , 1 8 9 0 ; S y k e s , 1 9 0 8 ) t h a t i n L a m i n a r i a l e s , t h e
m e d u l l a r y e l e m e n t s , i n c l u d i n g s i e v e e l e m e n t s a n d h y p h a e , a r e
d e r i v e d f r o m t h e i n n e r c o r t e x . H o w e v e r , t h e d e t a i l s o n t h e mode
o f i n i t i a t i o n o f t h e s e e l e m e n t s a n d t h e i r f i n e s t r u c t u r e h a v e
become a v a i l a b l e i n t h e ' s p e c i e s o f - L . g r o e n l a n d i c a o n l y r e c e n t l y
( S c h m i t z a n d S r i v a s t a v a , 1 9 7 4 b ) . A c c o r d i n g t o S c h m i t z a n d
S r i v a s t a v a ( 1 ' 9 7 4 b ) t h e i n n e r m o s t c o r t i c a l c e l l s c e a s e t h e i r
t r a n s v e r s e d i v i s i o n s a n d t h e i r l o n g i t u d i n a l f i l e s become
s e p a r a t e d f r o m e a c h o t h e r b y a m a t r i x o f i n t e r c e l l u l a r s u b s t a n c e
a s a p r e l u d e t o t h e i r t r a n s f o r m a t i o n i n t o s i e v e e l e m e n t s . I t i s
c o n f i r m e d i n t h i s s t u d y t h a t t h e s a m e mode o f d e r i v a t i o n o f t h e
s i e v e e l e m e n t s a s w e l l a s t h e h y p h a l c e l l s i s f o l l o w e d i n - M.
i n t e g r i f o l i a ( P a r t C-111) .
P l a n t s o f M a c r o c y s t i s h a v e a l i f e s p a n r a n g i n g f r o m 4 t o 8
y e a r s ( ~ o r t h , 1 9 7 1 ; L o b b a n , 1 9 7 8 d ) , h o w e v e r , i n d i v i d u a l f r o n d s
a r e r e p l e n i s h e d a n n u a l l y . L o b b a n ( 1 9 7 8 ~ ) r e c o r d e d s t i p e
e l o n g a t i o n r a t e s f o r - M. i n t e g r i f o l i a f r o m 20 mm/day i n F e b r u a r y
t o a maximum o f a b o u t 4 0 mmlday i n May, t h e n f a l l i n g i n O c t o b e r
a n d November. A s shown i n t h e p r e s e n t s t u d y , t h e p r o d u c t i o n o f
s i e v e e l e m e n t s i n t h e a p i c a l p a r t o f t h e s t i p e , h o w e v e r , s h o w s a
p e a k i n the e a r l y g r o w i n g s e a s o n , i . e . , F e b r u a r y - M a r c h , t h e n
d e c l i n e s a s t h e y e a r a d v a n c e s , a n d b e c o m e s q u i e s c e n t i n November
![Page 101: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/101.jpg)
( s e e F i g . 1 0 ) . F i g u r e 1 0 B r e v e a l s t h a t t h e r e a r e c o n s i s t e n t l y
1-2 f i l e s o f u n d i f f e r e n t i a t e d s i e v e e l e m e n t s i n t h e b a s a l
i n t e r n o d e o f t h e s t i p e (B p o i n t ) i n d i f f e r e n t m o n t h s . A s n o t e d
i n P a r t C-11, t h e s e u n d i f f e r e n t i a t e d s i e v e e l e m e n t s d o n o t
a p p e a r t o h a v e b e e n n e w l y f o r m e d . R a t h e r t h e y s e e m t o h a v e b e e n
l a i d down p r e v i o u s l y a n d i t i s p o s s i b l e t h a t t h e y a r e h e l d i n
t h i s s t a t e p o s s i b l y a s a r e s e r v e a g a i n s t i n j u r y .
I n r e s p e c t t o w h e t h e r t h e new s i e v e e l e m e n t s w o u l d b e
p r o d u c e d t h r o u g h o u t t h e l i f e s p a n o f t h e M a c r o c y s t i s f r o n d o r
n o t , two p o i n t s o f v i e w h a v e b e e n r a i s e d . W i l l ( 1 8 8 4 ) e x p r e s s e d
t h e v i e w t h a t s i e v e e l e m e n t s o f M a c r o c y s t i s w e r e t r a n s f o r m e d
f r o m i n n e r c o r t i c a l c e l l s c o n t i n u a l l y , w h i c h c o n s t a n t l y r e p l a c e d
t h e e x i s t i n g s i e v e e l e m e n t s i n t h e m e d u l l a . By c o n t r a s t ,
R o s e n t h a l ( 1 8 9 0 ) p r o p o s e d t h a t t h e r e w a s o n l y a l i m i t e d number -
o f i n n e r c o r t i c a l c e l l s t h a t m i g h t d i f f e r e n t i a t e i n t o s i e v e
e l e m e n t s a n d t h a t t h e e n l a r g e m e n t o f t h e m e d u l l a i n t h e o l d e r
s t i p e w a s m a i n l y d u e t o t h e e x p a n s i o n o f t h e p e r i p h e r a l s i e v e
e l e m e n t s a n d t h e i n t e r t w i n i n g h y p h a l c e l l s . T h i s s t u d y i n d i c a t e s
t h a t ( 1 ) t h e t o t a l number o f r a d i a l r o w s o f s i e v e e l e m e n t s i n
t h e m e d u l l a a n d t h e p o s s i b l e t o t a l n u m b e r o f l o n g i t u d i n a l f i l e s
o f s i e v e e l e m e n t s i n r a d i a l r o w s show o n l y a s m a l l o r n e g l i g i b l e
d i f f e r e n c e b e t w e e n A p o i n t a n d B p o i n t ( P a r t C - 1 1 , T a b l e 1111,
a n d ( 2 ) t h e d i a m e t e r s o f s i e v e e l e m e n t s i n B p o i n t a r e a b o u t 2
t i m e s l a r g e r t h a n t h o s e i n A p o i n t ( T a b l e I V ) . T h e s e d a t a seem
t o . f a v o r R o s e n t h a l ' s p r o p o s a l t h a t t h e p r o d u c t i o n o f new s i e v e
e l e m e n t s i s n o t a c o n t i n u o u s p r o c e s s . H o w e v e r , i t i s p o s s i b l e
![Page 102: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/102.jpg)
t h a t n o t a l l t h e s i e v e e l e m e n t s p r o d u c e d i n t h e l i f e s p a n o f t h e
f r o n d may be t r a c e a b l e by c o u n t i n g t h e n u m b e r o f s i e v e e l e m e n t
i n r a d i a l r o w s a c r o s s t h e m e d u l l a . N o n e t h e l e s s , i t d o e s s e e m
t h a t e i t h e r t h e i n i t i a t i o n o f s i e v e e l e m e n t s f r o m t h e i n n e r
c o r t i c a l c e l l s i s w i t h h e l d c o m p l e t e l y f r o m A p o i n t o n w a r d s , o r
a t m o s t i t p r o c e e d s e x t r e m e l y s l o w l y . I t i s p o s s i b l e t h a t a l l
t h e i n n e r c o r t i c a l c e l l s may s t i l l h a k e t h e p o t e n t i a l t o become
s i e v e e l e m e n t s b u t t h a t p o t e n t i a l i s s u b j e c t t o c o n t r o l by
i n t e r n a l f a c t o r s , s u c h a s h o r m o n e s .
The i n n e r m o s t c o r t i c a l c e l l s w h i c h c a n a l r e a d y b e
d i s t i n g u i s h e d a s p u t a t i v e s i e v e e l e m e n t s i n s t a g e S 1 d i f f e r f r o m
t h e r e s t o f t h e c o r t e x i n s e v e r a l ways . F i r s t l y , t h e y o c c u r i n
l o n g i t u d i n a l f i l e s a n d t h e s e f i l e s a r e s e p a r a t e d f r o m e a c h o t h e r
a n d f r o m t h e i n n e r c o r t e x by i n t e r c e l l u l a r s u b s t a n c e s . S e c o n d l y ,
t h e y become c y l i n d r i c a l h a v i n g a l o n g a x i s p a r a l l e l t o t h e a x i s
o f t h e s t i p e , w h e r e a s t h e c o r t i c a l c e l l s a r e more o r l e s s
i s o d i a m e t r i c ( T a b l e s I V a n d V). T h i r d l y , s e v e r a l t o many
v a c u o l e s r a t h e r t h a n a s i n g l e v a c u o l e t y p i c a l o f t h e c o r t i c a l
c e l l s a r e p r e s e n t i n S 1 . F o u r t h l y , t h e d i a m e t e r o f t h e S 1
n u c l e u s i s a b o u t t h e same o r s l i g h t l y l a r g e r t h a n t h a t o f t h e
c o r t i c a l c e l l able V I ) , b u t t h e f o r m e r s t a i n s more d e e p l y w i t h
t o l u i d i n e b l u e 0 s u g g e s t i n g t h a t t h e D N A c o n t e n t may b e h i g h e r
i n t h e f o r m e r . U n d e r t h e e l e c t r o n m i c r o s c o p e , t h e n u c l e u s o f t h e
c o r t i c a l c e l l s h o w s a h i g h e r d e g r e e o f c h r o m a t i n c o n d e n s a t i o n
a n d a l e s s e l a b o r a t e d n u c l e o l u s t h a n t h e n u c l e u s o f a n S 1 s i e v e
e l e m e n t ( c f . F i g s . 1 6 a n d 1 7 ) . T h i s a l s o s u g g e s t s t h e l a t t e r i s
![Page 103: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/103.jpg)
i n a m o r e a c t i v e s t a g e o f s y n t h e s i s ( L a f o n t a i n e , 1 9 7 4 ; R o s e ,
1 9 7 4 ) w h i c h c o r r e l a t e s w i t h a n e n o r m o u s i n c r e a s e o f c e l l u l a r
c o n t e n t s i n t h e d e v e l o p i n g s i e v e e l e m e n t s .
The y o u n g s i e v e e l e m e n t s o f M. i n t e g r i f o l i a show b a s i c a l l y
t h e same c o m p l e m e n t o f c y t o p l a s m i c o r g a n e l l e s a n d membrane
s y s t e m s a s t h o s e o f o t h e r L a m i n a r i a l e s ( S c h m i t z a n d S r i v a s t a v a ,
i 9 7 4 b , 1 9 7 5 , 1 9 7 6 ; S i d e m a n a n d S c h e i r e r , 1 9 7 7 ) . T h e r e a r e
n u m e r o u s v a c u o l e s , r i b o s o m e s , E R m e m b r a n e s , d i c t y o s o m e s ,
m i t o c h o n d r i a , p l a s t i d s , a n d a c o n s p i c u o u s n u c l e u s a n d n u c l e o l u s .
Bu t a f t e r t h e s y n t h e s i s o f t h e p r o t o p l a s t r e a c h e s i t s p e a k i n S2
s i e v e e l e m e n t s , i n M. i n t e g r i f o l i a t h e r e i s a s e l e c t i v e - d e g e n e r a t i o n o f t h e c y t o p l a s m a n d i t s o r g a n e l l e s , a f e a t u r e n o t
s e e n i n t h e o t h e r L a m i n a r i a l e s i n v e s t i g a t e d s o f a r a n d s i m i l a r
t o t h e d e g e n e r a t i o n o f p r o t o p l a s m i c c o n s t i t u e n t s t y p i c a l o f t h e
s i e v e e l e m e n t s i n h i g h e r v a s c u l a r p l a n t s . I n t h e f o l l o w i n g , t h e
c h a n g e s i n i n d i v i d u a l o r g a n e l l e s a n d membrane s y s t e m s a r e
d i s c u s s e d s e p a r a t e l y .
I n M . i n t e g r i f o l i a , b o t h n u c l e i a n d n u c l e o l i i n c r e a s e - d r a m a t i c a l l y i n vo lume ( T a b l e V I ) a n d s t a i n a b i l i t y by t o l u i d i n e
b l u e 0 f r o m t h e S 1 t o S2 s t a g e . Q u a n t i t a t i v e m e a s u r e m e n t s o f D N A
a n d R N A w e r e n o t c a r r i e d o u t i n t h i s s t u d y . H o w e v e r , i t h a s b e e n
r e p o r t e d t h a t i n d i f f e r e n t i a t i n g t r a c h e a r y e l e m e n t s t h e r e may b e
a 2 - , 4 - , o r e v e n 8 - f o l d i n c r e a s e i n t h e c o n t e n t o f n u c l e a r D N A
a n d h i s t o n e s ( P h i l l i p s a n d T o r r e y , 1 9 7 3 ; L a i a n d S r i v a s t a v a ,
1 9 7 6 ; Dodds a n d P h i l i p s , 1 9 7 7 ; s e e a l s o T u r g e o n , 1 9 7 5 ) .
C o r r e l a t e d f i n e s t r u c t u r a l s t u d i e s h a v e r e v e a l e d t h a t DNA- leve l
![Page 104: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/104.jpg)
c h a n g e s a r e a c c o m p a n i e d by a s e v e r a l - f o l d i n c r e a s e i n t h e
n u c l e a r a n d n u c l e o l a r v o l u m e ( L a i a n d S r i v a s t a v a , 1 9 7 6 ) , w h i c h
i s c o m p a r a b l e t o t h e n u c l e a r c h a n g e s o b s e r v e d i n t h e d e v e l o p i n g
s i e v e e l e m e n t s o f M. i n t e g r i f o l i a . S i n c e i n t e r m e d i a t e s t a g e s o f
s i e v e e l e m e n t d i f f e r e n t i a t i o n c a n b e f o u n d i n t h e a p i c a l p a r t o f
t h e M a c r o c y s t i s s t i p e , t h i s w o u l d b e g o o d m a t e r i a l f o r s t u d y i n g
t h e n u c l e a r D N A a n d R N A c h a n g e s c o r r e s p o n d i n g t o t h e s t r u c t u r a l
s p e c i a l i z a t i o n d u r i n g s i e v e e l e m e n t d i f f e r e n t i a t i o n .
The n u c l e o l i o f 5 2 s i e v e e l e m e n t s show g r a n u l a r , f i b r i l l a r ,
a n d v a c u o l a r z o n e s u n d e r t h e e l e c t r o n m i c r o s c o p e , t y p i c a l o f
t h o s e e n g a g e d i n r i b o s o m a l R N A s y n t h e s i s . I n t h e l a t e r S2 s t a g e ,
c h r o m a t i n c l u m p i n g s a p p e a r i n t h e n u c l e o p l a s m o f a h i g h l y l o b e d
n u c l e u s a n d t h e n u c l e o l u s b e c o m e s a c o m p a c t b o d y w i t h o u t a n y
d i s c e r n i b l e f i n e s t r u c t u r e , i n d i c a t i n g a n i n a c t i v e s t a t e . A t t h e
s u b s e q u e n t S 3 s t a g e , t h e n u c l e a r e n v e l o p e i s s t i l l i n t a c t b u t
t h e n u c l e o p l a s m i s a l m o s t e m p t y l o o k i n g , e x c e p t f o r some
f l o c c u l e n t r e s i d u e s , w h i c h r e s e m b l e s t h e phenomenon o f
c h r o m a t o l y s i s known f r o m h i g h e r p l a n t s ( S r i v a s t a v a , 1 9 7 5 ; E v e r t ,
1 9 7 7 ) .
A n a u t o r a d i o g r a p h i c s t u d y o n t h e i n c o r p o r a t i o n o f t r i t i a t e d
t h y m i d i n e i n t h e n u c l e i o f d i f f e r e n t i a t i n g s i e v e e l e m e n t s o f
P i s u m s a t i v u m ( Z e e a n d C h a m b e r s , 1 9 6 9 ) h a s s h o w n t h a t a s t h e
n u c l e i d e g e n e r a t e d d u r i n g m a t u r a t i o n o f t h e s i e v e - t u b e member s ,
t h e n u m b e r o f t r a c e r g r a i n s p r e s e n t i n t h e n u c l e i d e c r e a s e d .
C o n c o m i t a n t l y , c y t o p l a s m i c l a b e l t e n d e d t o i n c r e a s e , i n d i c a t i n g
t h a t t h e c h r o m a t i n m a t e r i a l i n t h e n u c l e u s w a s u n d e r g o i n g
![Page 105: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/105.jpg)
d i s s o l u t i o n a n d t h a t t h e c h r o m a t i n b r e a k d o w n p r o d u c t s were
c o n t i n u a l l y m i g r a t i n g f r o m t h e n u c l e u s t o t h e c y t o p l a s m . T h e
i n c o r p o r a t i o n o f t r i t i a t e d u r i d i n e , a n R N A p r e c u r s o r , w a s a l s o
a f f e c t e d d u r i n g t h e s i e v e e l e m e n t d i f f e r e n t i a t i o n i n P. s a t i v u m . - L a b e l f i r s t d i s a p p e a r e d f r o m t h e n u c l e o l u s , t h e n d e c r e a s e d o r
d i s a p p e a r e d a l t o g e t h e r i n t h e n u c l e u s , i n d i c a t i n g t h a t RNA
s y n t h e s i s w i t h i n t h e n u c l e u s h a d c e a s e d when t h e s i e v e e l e m e n t
g r a d u a l l y m a t u r e d .
The a p p e a r a n c e o f a n a u t o l y s e d n u c l e u s a n d t h e s h r i n k a g e o f
t h e n u c l e o l u s i n M a c r o c y s t i s s i e v e e l e m e n t a t S 3 s t a g e t h u s
g i v e s e v e r y s i g n o f a n o n f u n c t i o n a l n u c l e u s . No n u c l e a r r e m n a n t s
a r e d i s c e r n i b l e i n t h e m a t u r e s i e v e e l e m e n t s ( ~ 4 ) . Among o t h e r
c y t o p l a s m i c o r g a n e l l e s , d i c t y o s o m e s , ER, p l a s t i d s a n d
m i t o c h o n d r i a show some u n u s u a l f e a t u r e s w h i c h w i l l b e d i s c u s s e d
b e l o w .
D i c t y o s o m e s show a p e r i n u c l e a t e r e l a t i o n s h i p w i t h t h e
n u c l e u s i n t h e y o u n g s i e v e e l e m e n t s o f M. i n t e g r i f o l i a , a s a l s o
i n o t h e r L a m i n a r i a l e s ( S c h m i t z a n d S r i v a s t a v a , 1 9 7 4 b ; 1 9 7 6 ) .
T h i s k i n d o f r e l a t i o n s h i p h a s a l s o b e e n n o t e d f o r o t h e r t y p e s o f
c e l l s i n v a r i o u s b r o w n a l g a e ( B o u c k , 1 9 6 5 ) . I t h a s b e e n
s u g g e s t e d t h a t i n some a l g a l c e l l s s m a l l v e s i c l e s p r o d u c e d by
b u d d i n g o f t h e n u c l e a r e n v e l o p e , o r o f E R c o u l d b e t h e s o u r c e o f
l a m e l l a t i o n of d i c t y o s o r n e s r rove et &, 1 9 6 8 ; M o r r e a n d
M o l l e n h a u e r , 1 9 7 4 ; F i g . 2 0 ) . I t h a s b e e n d e m o n s t r a t e d t h a t t h e
d i c t y o s o m e i s m a i n l y i n v o l v e d i n t h e s y n t h e s i s a n d d e p o s i t i o n o f
new w a l l m a t e r i a l s i n p l a n t c e l l s ( N o r t h c o t e a n d P i c k e t t - H e a p s ,
![Page 106: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/106.jpg)
1 9 6 6 ; E v a n s - e t - 9 a 1 1 9 7 3 ; K i e r m a y e r a n d D o b b e r s t e i n , 1 9 7 3 ) . One
o f t h e m o s t c h a r a c t e r i s t i c f e a t u r e s o f M a c r o c y s t i s s i e v e
e l e m e n t s i s t h a t t h e y a c q u i r e v e r y t h i c k w a l l s d u r i n g
d i f f e r e n t i a t i o n . P a r k e r a n d H u b e r ( 1 9 6 5 ) m e a s u r e d 5-10 urn t h i c k
l a t e r a l w a l l s i n t h e m a t u r e s i e v e e l e m e n t s o f & p y r i f e r a . The
c r o s s w a l l s o f t h e o l d e r s i e v e e l e m e n t s ( c a . 0 .4-0 .6 urn t h i c k )
a r e a p p r o x i m a t e l y 8 t i m e s t h i c k e r t h a n t h o s e o f t h e y o u n g e r o n e s
( c a . 0 .05 -0 .08 urn) i n - L. g r o e n l a n d i c a ( S c h m i t z a n d S r i v a s t a v a ,
1 9 7 4 b ) . I n my m a t e r i a l a l s o ; t h e s i e v e e l e m e n t w a l l s , e . g . , t h e
e n d w a l l s , i n c r e a s e f r o m 0.2 urn t h i c k i n S l t o a b o u t 3 urn i n 5 4 .
T h e s e f i g u r e s i n d i c a t e t h a t s y n t h e s i s a n d d e p o s i t i o n o f w a l l
m a t e r i a l s a r e a c t i v e p r o c e s s e s d u r i n g s i e v e e l e m e n t
d i f f e r e n t i a t i o n . D i c t y o s o m e s a r e a b u n d a n t a n d h i g h l y i n f l a t e d i n
d i f f e r e n t i a t i n g s i e v e e l e m e n t s o f - M. i n t e g r i f o l i a a n d i t i s
p o s s i b l e t h a t t h e y p l a y a n i m p o r t a n t r o l e i n s y n t h e s i s a n d / o r
d e p o s i t i o n o f w a l l m a t e r i a l s t o t h e w a l l s o f t h e d e v e l o p i n g
s i e v e e l e m e n t s .
S e g m e n t s o f s m o o t h E R a s s o c i a t e d c l o s e l y w i t h t h e
d e v e l o p i n g s i e v e p l a t e s a r e n o t e d u b i q u i t o u s l y i n y o u n g s i e v e
e l e m e n t s o f L a m i n a r i a l e s . The i n t i m a t e a s s o c i a t i o n o f ER w i t h
t h e d e v e l o p i n g s i e v e p l a t e s h a s a l s o b e e n r e p o r t e d i n h i g h e r
p l a n t s ( E s a u - e t e, 1 9 6 2 ; S i n g h a n d S r i v a s t a v a , 1 9 7 2 ) . T h e
i n i t i a t i o n o f s i e v e - a r e a p o r e s g e n e r a l l y s t a r t s w i t h t h e
d e p o s i t i o n o f t h e c a l l o s e p l a t e l e t s a t t h e f u t u r e p o r e s i t e s i n
h i g h e r v a s c u l a r p l a n t s ( E s a u - e t -9 a 1 1 9 6 2 ; N o r t h c o t e a n d W o o d i n g ,
1 9 6 6 ) . A p p a r e n t l y , t w o e v e n t s , i . e. t h e s y n t h e s i s o f c a l l o s e a n d
7 1
![Page 107: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/107.jpg)
l a t e r t h e d e g r a d a t i o n o f c a l l o s e a n d t h e w a l l m a t e r i a l s a r e
i n v o l v e d i n t h e f o r m a t i o n o f t h e s i e v e a r e a s i n h i g h e r p l a n t s .
N o n e t h e l e s s , c a l l o s e h a s n e v e r b e e n d e t e c t e d i n t h e d e v e l o p i n g
p o r e s i t e s o f y o u n g s i e v e e l e m e n t s i n L a m i n a r i a l e s . T h e r o l e o f
t h e c a l l o s e p l a t e l e t s e e m s l i k e l y t o p r e v e n t o r i n h i b i t t h e
d e p o s i t i o n o f w a l l f i b r i l s a t t h e f u t u r e p o r e s i t e s ( E v e r t et
a 1 1 9 6 6 ; P a r t h a s a r a t h y , 1 9 7 4 ) , w h i l e some w o r k e r s h a v e -9
s u g g e s t e d t h a t t h e E R c i s t e r n a e a p p l i e d t o t h e p o r e s i t e s may
p l a y a s i m i l a r r o l e ( E s a u , 1 9 6 9 ) . A s b o t h a c i d p h o s p h a t a s e a n d
ATPase a c t i v i t y h a v e b e e n l o c a l i z e d i n ER membranes i n t h e s i e v e
t u b e s ( B e n t w o o d a n d C r o n s h a w , 1 9 7 6 ; G i l d e r a n d C r o n s h a w , 1 9 7 3
a n d 1 9 7 4 ) , i t i s s u g g e s t e d t h a t ER may be a n i m p o r t a n t s o u r c e o f
e n z y m e s i n v o l v e d i n f o r m a t i o n o f c a l l o s e a n d p r o b a b l y i n
p e r f o r a t i o n o f t h e s i e v e p l a t e s . ER f r a g m e n t s a r e n o t s e e n a t
p e r f o r a t e d s i e v e p l a t e s , b u t n u m e r o u s h i g h l y f l a t t e n e d a n d
c o n v o l u t e d s m o o t h E R membranes l i n e t h e l a t e r a l w a l l s i n t h e
m a t u r e s i e v e e l e m e n t s o f M, i n t e g r i f o l i a , w h i c h s o m e w h a t
r e s e m b l e s t h e s o - c a l l e d s i e v e - e l e m e n t E R i n h i g h e r p l a n t s ( B o u c k
a n d C r o n s h a w , 1 9 6 5 ; S r i v a s t a v a a n d O ' B r i e n , 1 9 6 6 ; W a l s h a n d
E v e r t , 1 9 7 5 ) . Whether t h e r e i s a n y s i g n i f i c a n c e o f t h i s s p a t i a l
d i s t r i b u t i o n o f ER membranes t o t h e f u n c t i o n o f m a t u r e s i e v e
e l e m e n t s i s n o t known.
The s t r u c t u r e o f p l a s t i d s i s i n many w a y s s i m i l a r i n t h e
y o u n g s i e v e e l e m e n t s o f d i f f e r e n t a l g a l s p e c i e s , s o i s t h e
s t r u c t u r e o f m i t o c h o n d r i a . D N A f i b r i l s a r e b e l i e v e d t o b e
p r e s e n t i n b o t h o r g a n e l l e s ( B i s a l p u t r a a n d B i s a l p u t r a , 1 9 6 7 ) .
72
![Page 108: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/108.jpg)
S i n c e t h e r e a p p e a r s t o b e many m o r e p l a s t i d s a n d m i t o c h o n d r i a i n
t h e y o u n g s i e v e e l e m e n t t h a n i n t h e c o r t i c a l c e l l , t h e s e
o r g a n e l l e s p r e s u m a b l y u n d e r g o s e l f - m u l t i p l i c a t i o n . M i t o c h o n d r i a
a r e p a r t i c u l a r l y a b u n d a n t i n t h e y o u n g s i e v e e l e m e n t s o f M. - i n t e g r i f o l i a a n d a n u n u s u a l a s s o c i a t i o n w i t h t h e d e v e l o p i n g
s i e v e p l a t e s i s n o t e w o r t h y ( F i g s . 3 6 , 3 7 ) . T h i s may i n d i c a t e
t h a t t h e f o r m a t i o n o f t h e s i e v e - p l a t e p o r e s i s a n
e n e r g y - r e q u i r i n g p r o c e s s .
P l a s t i d s may u n d e r g o c e r t a i n m o d i f i c a t i o n s a n d become
r i n g - s h a p e d , o r c u p - s h a p e d , a n d t h e g r o u n d m a t r i x o f b o t h
p l a s t i d s a n d m i t o c h o n d r i a may l o s e i t s d e n s i t y a n d a p p e a r
v a c u o l a t e d i n t h e o l d e r s i e v e e l e m e n t s o f L a m i n a r i a ( S c h m i t z a n d
S r i v a s t a v a , 1 9 7 4 b ) . T h e i r o u t e r m e m b r a n e s a l s o may become h i g h l y
v e s i c u l a t e d . P l a s t i d s a n d m i t o c h o n d r i a i n S 4 s i e v e e l e m e n t s o f
M. i n t e g r i f o l i a r e t a i n t h e i r n o r m a l s h a p e , w h i l e t h e i r g r o u n d - m a t r i x become l e s s e l e c t r o n - d e n s e a n d t h e r e a r e f e w e r c r i s t a e i n
t h e l a t t e r . No p y r e n o i d s a r e a s s o c i a t e d w i t h s i e v e e l e m e n t
p l a s t i d s o f a l l L a m i n a r i a l e s s t u d i e d s o f a r .
S c h m i t z a n d S r i v a s t a v a ( 1 9 7 4 b ) o b s e r v e d t w o t y p e s o f
v a c u o l e s i n g r o e n l a n d i c a , i . e . , t y p e I v a c u o l e w h i c h i s
e n c l o s e d b y t h e t o n o p l a s t a n d i s f r e e o f a n y i n c l u s i o n s ; and
t y p e I1 v a c u o l e w h i c h h a s d e n s e s u b s t a n c e s d e p o s i t e d a l o n g t h e
i n n e r s u r f a c e o f t h e t o n o p l a s t . I n s i e v e e l e m e n t s o f - M.
i n t e g r i f o l i a , o n l y t y p e I v a c u o l e s were f o u n d . V a c u o l e s a r e
r e t a i n e d i n m a t u r e s i e v e e l e m e n t s o f L a m i n a r i a , A l a r i a , and
N e r e o c y s t i s , b u t s e e m t o d i s a p p e a r i n m a t u r e s i e v e e l e m e n t s o f
![Page 109: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/109.jpg)
M. i n t e g r i f o l i a . O r g a n e l l e s s u c h a s l a m e l l a r b o d i e s s e e m t o - o c c u r m o r e o f t e n i n m a t u r e t h a n i n y o u n g s i e v e e l e m e n t s o f M. - i n t e g r i f o l i a . T h e y h a v e b e e n o b s e r v e d i n v a r i o u s b r o w n a l g a l
c e l l s by d i f f e r e n t a u t h o r s ( B o u r n e a n d C o l e , 1 9 6 8 ; M c C u l l y ,
1 9 6 8 ) ; h o w e v e r , t h e i r n a t u r e a n d f u n c t i o n r e m a i n unknown.
P - p r o t e i n w h i c h o c c u r s i n t h e s i e v e - t u b e members o f many
d i c o t y l e d o n s ( s e e r e v i e w by C r o n s h a w , 1 9 7 4 ) i s n o t s e e n i n t h e
s i e v e e l e m e n t s o f M. i n t e g r i f o l i a , n o r i s i t r e p o r t e d i n o t h e r - L a m i n a r i a l e s ( S c h m i t z and S r i v a s t a v a , 1 9 7 4 b , 1 9 7 5 , 1 9 7 6 ; S i d e m a n
a n d S c h e i r e r , 1 9 7 7 ) . What P a r k e r a n d H u b e r ( 1 9 6 5 ) i n t e r p r e t e d a s
P - p r o t e i n l o o k s more l i k e a n a r t i f a c t c a u s e d by i n a d e q u a t e
f i x a t i o n t h a n t h e r e a l s t r u c t u r e .
B a s e d 'on t h e f a c t t h a t t h e n u m b e r o f p o r e s i n t h e m a t u r e
s i e v e p l a t e s w a s much l a r g e r t h a n t h e n u m b e r o f p o t e n t i a l p o r e
s i t e s i n t h e c r o s s w a l l s o f t h e y o u n g s i e v e e l e m e n t s o f
g r o e n l a n d i - c a , S c h m i t z a n d S r i v a s t a v a ( 1 9 7 4 b ) p o s t u l a t e d t h a t t h e
s i e v e p o r e s w e r e f o r m e d d e n o v o by e n z y m a t i c d i s s o l u t i o n o f -- s e l e c t e d r e g i o n s i n t h e c r o s s w a l l , r a t h e r t h a n by e n l a r g e m e n t
o f t h e p o r e s i t e s d e l i m i t e d by t h e p r i m a r y p i t f i e l d s . H o w e v e r ,
t h e c r o s s w a l l s o f S1 s i e v e e l e m e n t s o f M. i n t e g r i f o l i a w e r e - t r a v e r s e d by n u m e r o u s p l a s m o d e s m a t a w h i c h w e r e n o l o n g e r
c o n f i n e d t o t h e p r i m a r y p i t f i e l d s , t y p i c a l o f c o r t i c a l c e l l s
( ~ i g s . 1 2 , 3 4 ; B i s a l p u t r a , 1 9 6 6 ; M a r c h a n t , 1 9 7 6 ) . A c c o r d i n g l y ,
t h e r e d i s t r i b u t i o n o f t h e p l a s m o d e s m a t a o r t h e f o r m a t i o n o f t h e
new p l a s m o d e s m a t a m u s t h a v e o c c u r r e d a t t h e i n i t i a t i o n o f s i e v e
e l e m e n t d i f f e r e n t i a t i o n . The p l a s m o d e s m a t a o n t h e c r o s s w a l l s o f
![Page 110: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/110.jpg)
S I s eem t o b e t h e f u t u r e p o r e s i t e s ( ~ i g s . 3 5 , 4 0 ) . A s t h e
d i f f e r e n t i a t i o n p r o g r e s s e s , t h e s i e v e - e l e m e n t c e l l n o t o n l y
e l o n g a t e s b u t a l s o ' i n c r e a s e s i t s d i a m e t e r . A l t h o u g h i t i s
n a t u r a l t h a t t h e d e n s i t y o f t h e p l a s m o d e s m a t a p e r u n i t a r e a
d r o p s ( 1 0 0 - 1 6 /umL) a s t h e d i a m e t e r o f t h e c r o s s q a l l o f t h e
s i e v e e l e m e n t ( S l - S 3 ) i n c r e a s e s , t h e r e a r e f e w e r s i e v e p o r e s i n
t h e m a t u r e s i e v e p l a t e s o f S4 s i e v e e l e m e n t s ( c a . 0.08-0.,16 /um 2
1. I t s e e m s l i k e l y t h a t t h e f u s i o n o f s e v e r a l p l a s m o d e s m a t a
r e s u l t i n g f r o m t h e d i s s o l u t i o n o f t h e w a l l m a t e r i a l s may h a v e
t a k e n p l a c e d u r i n g t h e f o r m a t i o n o f t h e s i e v e p l a t e s .
The phenomenon o f p e r f o r a t i o n o f s i e v e p l a t e i s s e e n o n l y
when t h e a u t o p h a g i c p r o c e s s o f t h e c y t o p l a s m h a s b e g u n . I t i s
p l a u s i b l e t h a t t h e r e q u i r e d h y d r o l y t i c e n z y m e s f o r d i g e s t i n g t h e
c e l l w a l l a r e r e l e a s e d o r a r e a v a i l a b l e a t t h a t t i m e . The s i e v e
p o r e c a n a l s i n t h e m a t u r e s i e v e e l e m e n t s o f L a m i n a r i a a n d
N e r e o c y s t i s a r e s t i l l t r a v e r s e d by c y t o p l a s m i c s t r a n d s , b u t i n
t h e s i e v e e l e m e n t s o f M. i n t e g r i f o l i a t h e y a r e a p p a r e n t l y o p e n
a n d a l m o s t f r e e d f r o m a n y s u b s t a n c e s ( F i g . 3 7 ; S c h m i t z , 1 9 7 6 ,
h i s F i g . 1 3 b ) .
The s i z e o f t h e s i e v e p o r e s m e a s u r e d v a r i e s i n d i f f e r - e n t
s p e c i e s o f L a m i n a r i a l e s . The s m a l l e s t p o r e s i z e r e c o r d e d s o f a r
i s i n L a m i n a r i a , r a n g i n g b e t w e e n 0.04-0.09 urn i n d i a m e t e r
( S c h m i t z a n d S r i v a s t a v a , 1 9 7 4 b ; S i d e m a n a n d S c h e i r e r , 1 9 7 7 ) .
W h i l e M a c r o c y s t i s s p e c i e s h a v e t h e m o s t s p e c i a l i z e d s i e v e
e l e m e n t s w i t h s i e v e - p l a t e p o r e s , 0 .6-6 .0 um i n d i a m e t e r ( P a r k e r
a n d H u b e r , 1 9 6 5 ; S c h m i t z , 1 9 7 6 ; a n d p r e s e n t s t u d y ) ; A l a r i a a n d
![Page 111: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/111.jpg)
Nereocystis, with sieve pores 0.11-0.4 um in diameter (Schmitz
and Srivastava, 1975; 1976), are ranked between Laminaria and
Macrocystis. In conjunction with the differentiation of the
sieve element, the large sieve-plate pores and their efficient
system of translocation of assimilates, Macrocystis is probably
one of the most evolutionally advanced plants among all the
Laminariales.
It has been shown in this study that the mature sieve
elements are the pathway of 14c-labeled photoassimilates in M. - integrifolia. Very young sieve elements in stage S1 are not
capable of long-distance transport of photoassimilates as
evidenced by the absence of silver grains in them (Fig. 46).
However, sieve elements in file 11, 111, and IV (Fig. 46) which
correspond to the mature sieve elements in stage S4 (Fig. 5 ) are
conducting.14c label was not seen either in the very old sieve
elements often occluded by the callose in the central medulla or
in the anastomosing hyphal cells. The old sieve elements
apparently had lost their function. Hyphal cells, on the
contrary, have not seemed to be involved in translocation at all
(see also Steinbiss and Schmitz, 1973).
A very interesting point is that only specific sieve
elements beneath (and probably above) the source blade are
involved in transporting the assimilates from the blade (see
also Schmitz and Srivastava, 1979b; their Fig. 5 ) . Such a
relationship has also been demonstrated in sugar beet (Joy,
1964). Sieve elements of - M. integrifolia which occur in long
![Page 112: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/112.jpg)
f i l e s , h o w e v e r , may f o r m a t h r e e - d i m e n s i o n a l s y s t e m by means o f
c r o s s c o n n e c t i o n s . T h e r e i s c o n s i d e r a b l e l a b e l s e e n a t c r o s s
c o n n e c t i o n s ( F i g . 47), t h e r e f o r e , i t i s c o n j e c t u r e d t h a t g i v e n a
l o n g e r t i m e t r a c e r g r a i n s w i l l a p p e a r i n m o r e f i l e s o f s i e v e
e l e m e n t s a t i n c r e a s i n g d i s t a n c e s f r o m t h e s o u r c e b l a d e .
I t h a s b e e n shown t h a t t h e s i e v e e l e m e n t s o f M. - i n t e g r i f o l i a c o n t a i n a v e r y h i g h a m o u n t o f ATP ( u p t o 1200
u g / m l ) ( S c h m i t z a n d S r i v a s t a v a , 1 9 7 4 a ) w h i c h i n t h e p r e s e n t
s t u d y c a n b e c o r r e l a t e d t o t h e p r e s e n c e o f many m i t o c h o n d r i a i n
t h e m a t u r e s i e v e e l e m e n t s . M i t o c h o n d r i a a r e a l s o f o u n d i n m a t u r e
s i e v e e l e m e n t s o f o t h e r L a m i n a r i a l e s . T h i s may i n d i c a t e t h a t t h e
t r a n s l o c a t i o n o f a s s i m i l a t e s t h r o u g h t h e m a t u r e s i e v e e l e m e n t s
r e q u i r e s a c o n s i d e r a b l e a m o u n t o f ATP. U n l i k e s i e v e e l e m e n t s i n
h i g h e r v a s c u l a r p l a n t s , s i e v e e l e m e n t s o f L a m i n a r i a l e s a r e n o t
a s s o c i a t e d w i t h c o m p a n i o n c e l l s o r o t h e r s p e c i a l i z e d p a r e n c h y m a
c e l l s . The h i g h a m o u n t o f ATP f o u n d i n s i e v e e l e m e n t s o f
M a c r o c y s t i s ( S c h m i t z a n d S r i v a s t a v a , 1 9 7 4 a ) may r e f l e c t a
m e t a b o l i c a l l y i n d e p e n d e n t s y s t e m w i t h i n t h e s e c e l l s . R e c e n t l y ,
S c h m i t z a n d S r i v a s t a v a ( 1 9 8 0 ) h a v e s u g g e s t e d t h a t t h e
o s m o t i c a l l y - d r i v e n p r e s s u r e - f l o w m e c h a n i s m i s o p e r a t i v e i n
M a c r o c y s t i s . T h e y showed t h a t t r i t i a t e d w a t e r ( T H O ) moved w i t h
t h e o r g a n i c p h o t o a s s i m i l a t e s t h r o u g h t h e t r a n s l o c a t i o n p a t h w a y
f r o m s o u r c e ( m a t u r e b l a d e s ) t o s i n k ( g r o w i n g r e g i o n s ) . A l t h o u g h
s t r i c t l y s p e a k i n g , t h e p r e s s u r e f l o w m e c h a n i s m d o e s n o t r e q u i r e
m e t a b o l i c e n e r g y , l o a d i n g a n d u n l o a d i n g a g a i n s t t h e g r a d i e n t o f
t h e s o l u t i o n a l o n g t h e t r a n s l o c a t i o n p a t h w a y mus t b e
![Page 113: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/113.jpg)
energy-consuming processes. The present study shows that the
conducting sieve elements of M. integrifolia indeed have large - open pores at the sieve plates and empty-looking central lumina,
both important prerequisites for the bulk flow of solutions
(crafts and Crisp, 1 9 7 1 ) . However, while the sieve elements of
Macrocystis represent the most specialized translocation system
among Laminariales, the same mechanism of translocation of
assimilates may not be operative in the more primitive system,
e.g., of Laminaria.
![Page 114: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/114.jpg)
E. REFERENCES
B e n t w o o d , B . J . and J . C r o n s h a w . 1 9 7 6 . B i o c h e m i s t r y a n d c y t o c h e m i c a l l o c a l i z a t i o n o f a c i d p h o s p h a t a s e i n t h e p h l o e m o f N i c o t i a n a t a b a c u m . P l a n t a ( B e r l . ) 1 3 0 : 97-104 .
B i s a l p u t r a , T. 1966 . E l e c t r o n m i c r o s c o p i c s t u d y o f t h e p r o t o p l a s m i c c o n t i n u i t y i n c e r t a i n b r o w n a l g a e . Can . J . Bo t . 4 4 : 8 9 - 9 3 .
B i s a l p u t r a , T. and A . A . B i s a l p u t r a . 1 9 6 7 . C h l o r o p l a s t a n d m i t o c h o n d r i a D N A i n a b r o w n a l g a E g r e g i a m e n z i e s i i . J . C e l l B i o l . 3 3 : 511-520 .
Bouck , C .B . 1965 . F i n e s t r u c t u r e a n d o r g a n e l l e a s s o c i a t i o n i n b r o w n a l g a e . J . C e l l B i o l . 2 6 : 5 2 3 - 5 3 7 .
B o u r n e , V.L. a n d K . C o l e . 1 9 6 8 . Some o b s e r v a t i o n s o n t h e f i n e s t r u c t u r e o f t h e m a r i n e b r o w n a l g a P h a e o s t r o p h i o n i r r e g u l a r e . Can. J . B o t . 4 6 : 1 3 6 9 - 1 3 7 5 .
C r a f t s , A.S. 1939 . The r e l a t i o n b e t w e e n s t r u c t u r e a n d f u n c t i o n o f t h e ph loem. A m e r . J . B o t . 2 6 ( 3 ) : 172 -177 .
C r a f t s , A.S. a n d C . E . C r i s p . 1 9 7 1 . P h l o e m t r a n s p o r t i n p l a n t s . W.H. F r e e m a n a n d Company. S a n F r a n c i s c o . 4 8 1 p p .
C r o n s h a w , J . 1974 . P - p r o t e i n s . I n : P h l o e m T r a n s p o r t . A r o n o f f , A . , e t a l . ( e d s . ) 79-115pp.
D o d d s , J . H . a n d R. P h i l i p s . 1 9 7 7 . D N A a n d h i s t o n e c o n t e n t o f i m m a t u r e t r a c h e a r y e l e m e n t s f r o m c u l t u r e d a r t i c h o k e e x p l a n t s . P l a n t a 1 3 5 : 213 -216 .
E s a u , K . 1 9 6 9 . The ph loem. E n c y c l o p e d i a o f P l a n t Anatomy. V.2. B o r n t r a g e r , B e r l i n .
E s a u , K . , V . I . C h e a d l e a n d E.M. G i f f o r d , J r . 1 9 5 3 . C o m p a r a t i v e s t r u c t u r e a n d p o s s i b l e t r e n d s o f s p e c i a l i z a t i o n o f t h e p h l o e m . Amer. J . B o t . 4 0 : 9 -19 .
E s a u , K . , V . I . C h e a d l e a n d E.B. R i s l e y . 1 9 6 2 . D e v e l o p m e n t o f s i e v e - p l a t e p o r e s . B o t . Gaz. 1 2 3 : 2 3 3 - 2 4 3 .
E s a u , K. a n d J . Cronshaw. 1 9 6 7 . T u b u l a r c o m p o n e n t s i n c e l l s o f h e a l t h y a n d t o b a c c o m o s a i c v i r u s - i n f e c t e d N i c o t i a n a . V i r o l o g y 3 3 : 26 -35 .
![Page 115: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/115.jpg)
E v a n s , L.V., M. S i m p s o n a n d M.E. C a l l o w . 1 9 7 3 . S u l p h a t e d p o l y s a c c h a r i d e s y n t h e s i s i n b r o w n a l g a e . P l a n t a 1 1 0 : 237-252 .
E v e r t , R.F. 1 9 7 7 . P h l o e m s t r u c t u r e a n d h i s t o c h e m i s t r y . Ann. Rev. P l a n t P h y s i o l . 2 8 : 1 9 9 - 2 2 2 .
E v e r t , R.F., L Murman i s a n d I . B . S a c h s . 1 9 6 6 . A n o t h e r v i e w o f u l t r a s t r u c t u r e o f C u c u r b i t a p h l o e m . Ann. B o t . 3 0 : 563 -585 .
F e d e r , N . a n d T.P. O I B r i e n . 1 9 6 8 . P l a n t m i c r o t e c h n i q u e : Some p r i n c i p l e s a n d new m e t h o d s . Amer. J . B o t . 5 5 : 1 2 3 - 1 4 2 .
G i l d e r , J . a n d J . Cronshaw. 1 9 7 3 . The d i s t r i b u t i o n o f a d e n o s i n e t r i p h o s p h a t a s e a c t i v i t y i n d i f f e r e n t i a t i n g a n d m a t u r e p h l o e m c e l l s o f N i c o t i a n a t a b a c u m a n d i t s r e l a t i o n s h i p t o p h l o e m t r a n s p o r t . J . U l t r a s t r u c . R e s . 4 4 : 3 8 8 - 4 0 4 .
G i l d e r , J . a n d J . Cronshaw. 1 9 7 4 . A b i o c h e m i c a l a n d c y t o c h e m i c a l s t u d y o f a d e n o s i n e t r i p h o s p h a t a s e a c t i v i t y i n t h e p h l o e m o f N i c o t i a n a t a b a c u m . J . C e l l B i o l . 6 0 : 221 -235 .
G r o v e , S.N., C.E. B r a c k e r a n d D . J . M o r r e . 1 9 6 8 . C y t o m e m b r a n e d i f f e r e n t i a t i o n i n t h e e n d o p l a s m i c r e t i c u l u m - G o l g i a p p a r a t u s - v e s i c l e c o m p l e x . S c i e n c e , N . Y . 1 6 1 : 1 7 1 - 1 7 3 .
J e n s e n , W.A. 1 9 6 2 . B o t a n i c a l H i s t o c h e m i s t r y . W.H. F r e e m a n .andl Company. S a n F r a n s i s c o a n d London .
J o y , K.W. 1 9 6 4 . T r a n s l o c a t i o n i n s u g a r - b e e t . I . A s s i m i l a t i o n o f C02 a n d d i s t r i b u t i o n o f m a t e r i a l s f r o m l e a v e s . J . Exp. B o t . 1 5 : 4 8 5 - 4 9 4 .
K i e r m a y e r , 0. a n d B. D o b b e r s t e i n . 1 9 7 3 . D i c t y o s o m e d e r i v e d membrane c o m p l e x e s a s t e m p l a t e s f o r t h e e x t r a p l a s m i c s y n t h e s i s a n d o r i e n t a t i o n o f m i c r o f i b r i l s . P r o t o p l a s m a 7 7 : 437 -451 .
L a f o n t a i n e , I . G . 1 9 7 4 . U l t r a s t r u c t u r a l o r g a n i z a t i o n o f p l a n t c e l l n u c l e i . I n : The C e l l N u c l e u s . B u s c h , H . ( e d . ) N .Y . a n d L o n d o n A c a d e m i c P r e s s . 1 4 9 - 1 8 5 p p .
L a i , V . a n d L.M. S r i v a s t a v a . 1 9 7 6 . N u c l e a r c h a n g e s d u r i n g d i f f e r e n t i a t i o n o f x y l e m v e s s e l e l e m e n t s . C y t o b i o l o g i e 1 2 : 220-243 .
L o b b a n , C.S. 1 9 7 8 a . T r a n s l o c a t i o n o f 14c i n M a c r o c y s t i s p y r i f e r a . P l a n t p h y s i o l . 6 1 : 5 8 5 - 5 8 9 .
![Page 116: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/116.jpg)
L o b b a n , C.S. 1 9 7 8 b . T r a n s l o c a t i o n o f 1 4 c i n M a c r o c s t i s i n t e g r i f o l i a ( ~ h a e o p h y c e a e ) . J . P h y c o l . ~&8--182.
L o b b a n , C.S. 1 9 7 8 c . G r o w t h o f M a c r o c y s t i s i n t e g r i f o l i a i n B a r k l e y S o u n d , V a n c o u v e r I s l a n d , B. C. Can. J. Bot . 5 6 : 2707-2711 .
L o b b a n , C.S. 1 9 7 8 d . The g r o w t h a n d d e a t h o f t h e M a c r o c y s t i s s p o r o p h y t e ( P h a e o p h y c e a e , L a m i n a r i a l e s ) . P h y c o l o g i a 1 7 ( 2 ) : 1 9 6 - 2 1 2 .
L u n i n g , K . , K . S c h m i t z a n d J . W i l l e n b r i n k . 1 9 7 3 . C02 f i x a t i o n a n d t r a n s l o c a t i o n i n b e n t h i c m a r i n e a l g a e . 111. R a t e s a n d e c o l o g i c a l s i g n i f i c a n c e o f t r a n s l o c a t i o n i n L a m i n a r i a h y p e r b o r e a a n d - L. s a c c h a r i n a . M a r i n e B i o l . 2 3 : 275-28.1.
M a r c h a n t , H . J . 1 9 7 6 . P l a s m o d e s m a t a i n a l g a e a n d f u n g i . I n : I n t e r c e l l u l a r C o m m u n i c a t i o n i n P l a n t s : s t u d i e s o n p l a s m o d e s m a t a . G u n n i n g , B.E.S. a n d A.W. R o b a r d s ( e d s . ) . S p r i n g e r B e r l i n , H e i d e l b e r g . 5 9 - 8 0 p p
M c C u l l y , M.E. 1 9 6 8 . H i s t o l o g i c a l s t u d i e s o n t h e g e n u s F u c u s . 111. F i n e s t r u c t u r e a n d p o s s i b l e f u n c t i o n s o f t h e e p i d e r m a l c e l l s o f t h e v e g e t a t i v e t h a l l u s . J . C e l l S c i . 3 : 1 -16 .
M o r r e , D . J . a n d H . H . M o l l e n h a u e r . 1 9 7 4 . The e n d o m e m b r a n e c o n c e p t : A f u n c t i o n a l i n t e g r a t i o n o f e n d o p l a s m i c r e t i c u l u m a n d G o l g i a p p a r a t u s . I n : D y n a m i c A s p e c t s o f P l a n t U l t r a s t r u c t u r e . A.W. R o d a r d s ( e d . ) M c G r a w - R i l l . 8 4 - 1 3 1 p p .
N i c h o l s o n , N.L. a n d W.R. B r i g g s . 1 9 7 2 . T r a n s l o c a t i o n o f p h o t o s y n t h a t e i n t h e b r o w n a l g a N e r e o c y s t i s . Amer. J . B o t . 5 9 : 97 -106 .
N o r t h , W . J . 1 9 7 1 . I n t r o d u c t i o n a n d b a c k g r o u n d . I n : The B i o l o g y o f G i a n t K e l p B e d s ( ~ a c r o c y s t i s ) i n C a l i f o r n i a . N o r t h , W . J . ( e d . ). Nova H e d w i g i a B e i h . 3 2 : 1 -97 .
N o r t h c o t e , D.H. a n d J . D . P i c k e t t - H e a p s . 1 9 6 6 . A f u n c t i o n o f t h e G o l g i a p p a r a t u s i n p o l y s a c c h a r i d e s y n t h e s i s a n d t r a n s p o r t i n t h e r o o t - c a p c e l l s o f w h e a t . B i o c h e m . J . 9 8 : 1 5 9 - 1 6 7 .
N o r t h c o t e , D.H. a n d F.B.P. Wood ing . 1 9 6 6 . D e v e l o p m e n t o f s i e v e t u b e s i n Acer p s e u d o p l a t a n u s . P r o . Roy. S o c . B o t . 1 6 3 : 524 -537 .
O l k v e r , F.W. 1 8 8 7 . On t h e o b l i t e r a t i o n o f t h e s i e v e t u b e i n L a m i n a r i c a e . Ann. B o t . ( L o n d o n ) 1 : 9 5 - 1 1 7 .
![Page 117: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/117.jpg)
Parker, B.C. 1963. Translocation in the giant kelp Macrocystis. Science 140: 891-2.
Parker, B.C. 1965. Translocation in the giant kelp Macrocystis. I. Rates, direction, quantity of 14~-labeled products and fluorescein. J. Phycol. 1: 41-46.
Parker, B.C. 1966. Translocation in Macrocystis. 111. Composition of sieve tube exudate and identification of the major 14c-labeled products. J. Phycol. 2 : 38-41.
- Parker, B.C. and J. Huber. 1965. Translocation in Macrocystis.
11. Fine structure of the sieve tubes. J. Phvcol. 1:
Parker, B.C. and M. Fu. 1965. The internal structure of the elk kelp (Pelagophycus sp.). Can. J. Bot. 43: 1293-1305.
Parker, J. and D.E. Philpott. 1961. The ultrastructure of sieve plates of Macrocystis pyrifera. Bull. Torrey Bot. Club 88: 85-90.
Parthasarathy, M.V. 1974. Ultrastructure of phloem in palms. 11. Structural changes, and fate of the organelles in differentiating sieve elements. Protoplasma 79: 93-125.
Parthasarathy, M.V. and P.V. Tomlinson. 1967. Anatomical features of metaphloem in stems of Sabal, Cocos and two other palms. Amer. J. Bot. 54: 1143-1151.
Philips, R. and J.G. Torrey. 1974. DNA levels in differentiating tracheary elements. Develop. Biol. 39: 322-325,.
Rose, R.J. 1974. Changes in nucleolar activity during the growth and development of the wheat coleoptile. Protoplasma 79: 127-143.
Rosenthal, 0. 1890. Zur kenntnis von Macrocystis und Thalassiophyllum. Flora 73: 105-147.
Sargent, M.C. and L.W. Lantrip. 1952. Photosynthesis, growth and translocation in giant kelp. Amer. J. Bot. 39: 99-107. '
Schmitz, K. 1976. Zum assimilattransport in marinen algen, struktur und funktion der siebelemente bei den Laminariales. Habilitationsschrift der Mathematisch-Naturwissenschaftichen
' Fakultat der Universitat zu Koln.
Schmitz, K. and C.S. Lobban. 1976. A survey of translocation in
![Page 118: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/118.jpg)
L a m i n a r i a l e s ( P h a e o p h y c e a e ) . M a r i n e B i o l . 36 : 207-216 .
S c h m i t z , K . and L.M. S r i v a s t a v a . 1 9 7 4 a . T h e e n z y m a t i c - - i n c o r p o r a t i o n o f "P i n t o ATP a n d o t h e r o r g a n i c c o m p o n e n t s by s i e v e t u b e s a p o f M a c r o c y s t i s i n t e g r i f o l i a Bory . P l a n t a ( ~ e r 1 . ) 1 1 6 : 8 5 - 8 9 .
S c h m i t z , K . and L.M. S r i v a s t a v a . 1 9 7 4 b . F i n e s t r u c t u r e a n d d e v e l o p m e n t o f s i e v e t u b e s i n L a m i n a r i a g r o e n l a n d i c a R o s e n v . C y t o b i o l o g i e 1 0 : 66-87 .
S c h m i t z , K . and L.M. S r i v a s t a v a . 1 9 7 5 . On t h e f i n e s t r u c t u r e o f s i e v e t u b e s a n d t h e p h y s i o l o g y o f a s s i m i l a t e t r a n s p o r t i n A l a r i a m a r g i n a t a . Can. J . Bo t . 5 3 : 8 6 1 - 8 7 6 .
S c h m i t z , K . and L.M. S r i v a s t a v a . 1 9 7 6 . T h e f i n e s t r u c t u r e o f s i e v e e l e m e n t s o f N e r e o c y s t i s l u t k e a n a . Amer. J . Bo t . 6 3 : 6 7 9 - 6 9 3 .
S c h m i t z , K . a n d L.M. S r i v a s t a v a . 1 9 7 9 a . L o n g d i s t a n c e t r a n s p o r t i n M a c r o c y s t i s i n t e g r i f o l i a . I . T r a n s l o c a t i o n o f 1 4 c - l a b e l e d a s s i m i l a t e s . P l a n t P h y s i o l . 6 3 : 9 9 5 - 1 0 0 2 .
S c h m i t z , K . a n d L.M. S r i v a s t a v a . 1 9 7 9 b . L o n g d i s t a n c e t r a n s p o r t i n N $ c r o c y s t i s i n t e g r i f o l i a 11. T r a c e r e x p e r i m e n t s w i t h 14c a n d J L P . P l a n t P h y s i o l . 6 3 : 1 0 0 3 - 1 0 0 9 .
S c h m i t z , K . L.M. S r i v a s t a v a . 1 9 8 0 . L o n g d i s t a n c e t r a n s p o r t i n M a c r o c y s t i s i n t e g r i f o l i a 111. Movement o f THO. P l a n t P h y s i o l . 6 6 : 66 -69 .
S i d e m a n , E . J . a n d D . C . S c h e i r e r . 1 9 7 7 . Some f i n e s t r u c t u r a l o b s e r v a t i o n s o n d e v e l o p i n g a n d m a t u r e s i e v e e l e m e n t s i n t h e b r o w n a l g a L a m i n a r i a s a c c h a r i n a . A m e r . J . B o t . 6 4 : 649 -657 .
S i n g h , A.P. a n d L.M. S r i v a s t a v a . 1 9 7 2 . The f i n e s t r u c t u r e o f c o r n ph loem. Can. J . B o t . 5 0 : 8 3 9 - 8 4 6 .
S m i t h , A . I . 1 9 3 9 . The c o m p a r a t i v e h i s t o l o g y o f some o f t h e L a m i n a r i a l e s . Amer. J . B o t . 2 6 : 5 7 1 - 5 8 5 .
S p u r r , A.R. 1 9 6 9 . A l o w - v i s c o s i t y e p o x y r e s i n e m b e d d i n g medidm f o r e l e c t r o n m i c r o s c o p y . 3 . U l t r a s t r u c t . R e s . 2 6 : 31-43 .
S r i v a s t a v a , L.M. 1 9 7 5 . S t r u c t u r e a n d d i f f e r e n t i a t i o n o f s i e v e e l e m e n t s i n A n g i o s p e r m s a n d Gymnospe rms . I n : P h l o e m T r a n s p o r t . A r o n o f f , A . , e t a l . ( e d s . ) 33-62pp.
S r i v a s t a v a , L.M. a n d T.P. 0 ' B r i e n . 1 9 6 6 . On t h e u l t r a s t u r c t u r e
![Page 119: ON THE SIEVE ELEMENTS OF MACROCYSTIS ...summit.sfu.ca/system/files/iritems1/4010/b12743665.pdfABSTRACT The sieve elements of Macrocystis integrifolia occur characteristically in radial](https://reader031.vdocuments.us/reader031/viewer/2022013009/5ec14f8ce6bb3751b74bee12/html5/thumbnails/119.jpg)
of cambium and its vascular derivatives. 11. Secondary phloem of Pinus strobus L. Protoplasma 61: 277-2930
Steinbiss, H.H. and K. Schmitz. 1973. C02-fixierung und stofftransport in benthischen marinen algen. V. Zur autoradiographischen lokalisation der assimilat transportbahnen im thallus von Laminaria hyperborea. Planta 112: 253-2630
Sykes, M.G. 1908. Anatomy and histology of Macrocystis pyrifera and Laminaria saccharins. Ann. Bot. 22: 291-325.
Turgeon, R. 1975. Differentiation of wound vessel members without DNA synthesis, mitosis or cell division. Nature 257: 806-808.
Walsh, M.A. and R.F. Evert. 1975. Ultrastructure of metaphloem sieve elements in - Zea mays. Protoplasma 83: 365-388.
Will, H. 1884. Zur anatomie von Macrocystis luxurians Hook. Harv. Bot. Z. 42: 801-808, 825-830.
Wille, N. 1885. Bidrag ti1 algernes physiologiske anatomie K. Svenska Vetenskaps-Akademiens Hand. 21, no. 12.
Zee, S.-Y. and T.C. Chambers. 1969. Development of the secondary phloem of the primary root of Pisum. Aust. J. Bot. 17: 199-214.
Ziegler, H. 1963. 11. Die siebplatten bei der braun alge Macrocystis pyrifera(L.)AG. Protoplasma 57: 786-799.