gymnosperms 2013

8/10/2019 Gymnosperms 2013

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Seed Plants

Gymnosperm and Angiosperms


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EVOLUTION OF LAND PLANTS


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CLADOGRAM OF LAND PLANTS


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Gymnosperms

PhylumCommon

Name

Approx. # of

Species

Ginkgophyta Ginkgo 1

Cycadophyta Cycads 130

Gnetophyta Gnetae 75

Coniferophyta Conifers 600


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Characteristics of Gymnosperms

Vascular tissue present

Phloem and xylem

Naked seeds

No flowers

Dominant generation: Sporophyte


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Phylum Cycadophyta

The Cycads


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General features of Cycads sporophyte

Resemble a fern or a

young palm trees

Monopodial growth

Persistent leaf scars

Dioecious Crown of pinnate

leaves

Stem has little wood


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Cycads are dioecious

Female cycad with

megasporophylllsmale cycad with pollen cone


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Cycads exhibit leaf dimorphism

CataphyllFoliage leaves (crown)


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Cycas revo lutaOliba or sago palm


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Cy

c

a

da

c

e

a

e

Cycas revoluta

Cycas circinalis


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Cycas circ inal isPitogo


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Male Cycas circinalis


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Female Cycas circinalis

Megasporophyll with seeds

Megasporophyll with

ovules


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Zamia pumila


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Ginkgophyta

Ginkgoales

Ginkgo biloba Popular street tree

Highly branched woody

tree

Fan-shaped often 2-lobed

leaves w/ dichotomous

venation

Dioecious

Motile sperm


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Ginkgo bi loba produces long and short

shoot


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Leaves are fan -sh aped (bi lobed) w i thd ichotomous venat ion


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Ginkgo bi loba

Male inflorescence resembles a catkin - With cones but do not

bear structures that resemble sporophylls


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Ginkgo bi loba

Ovules occur in pairs, naked and without

ovuliferous scales


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Pharmaceutical importance of

Ginkgoes

Ginkgolides


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Coniferophyta- Conifers

Highly branched trees

or shrubs with simple

leaves

50 genera and 550species

Sperm non-motile

Evergreen leaves Needle-like, scale-

like, flat blades


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Leaves of conifers are simple

Abies bracteata with two

white bandsScale-like leaves of cedar

Needle-like leaves and scale

leaves of pine


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Leaves of conifers have transfusion tissues

Transfusion cells


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A closer look to a pine tree

Long shoot and short shoot (spur shoot)


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Sporophyte of pine tree

is dioecious.

Male cone (pollen cone) Produce microspores.

Microspores undergo meiosisand eventually produce pollen

grains.

Female cone (ovulate cone)

Produce megaspores.

Megaspores undergo meiosisand eventually produce thearchegonia.

Male plant (male cone)

Female plant (female cone)

Wood of pine trees contains tracheids only


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Wood of pine trees contains tracheids only.


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Germinating pine pollen consists of air bladder, generative

cell, tube cell and nucleus


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Seed cones (female) are compound cones

L-section of a female cone


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Ovuliferous scale has two ovules, each with

integuments and nucellus

L-section of an ovule


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Embryo of pine tree

Megagametophyte

Cotyledon

Epicotyl

Hypocotyl

Radicle


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ConiferDiversity

A. Araucariaceae

B-G. Cupressaceae

H. Podocarpaceae

I-J. Taxaceae

K-L. Pinaceae

A i


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Araucariaceae

Evergreen and scale-like

leaves

Commonly called Norkfolk

Island pine or Bunya-bunya


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Cuppressaceae- the sipres

P d P d


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Podocarpaceae- Podocarpus


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Taxaceae - Taxus

Arillate cone (fleshy ) of Taxusconifer with flat blades

source of anti-cancer drug taxol


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Taxolis an anti-cancer drug


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Pinaceae


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Pinaceae: PinusFasc icle of need le-l ike leaves, male o r s tamin ate

con es in shor t branch es


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Pharmaceutical importance of Pinaceae


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Pharmaceutical importance of Pinaceae


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Gnetophyta - Gnetales

3 extant families

Thought to be sister group

Striate pollen

The only Gymnosperms with vessels

with pore-like plates

Gnetaceae Gnetum 28 spp


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GnetalesGnetaceae Gnetum 28 spp.

+ m onotyp ic Vinkiella

Gym nosperm with dicotyl- like leaves

Ovules o f Gnetum are no t bo rne in cones


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Ovules o f Gnetum are no t bo rne in cones


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Mi i t l k l ik


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Microsporangiate cones look l ike

stam inate imperfect inf lorescence

Th k d l f E h d l th t


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The naked ovu les of Ephedra reveal that

they are gymnosperm

E h d i i lk l id t t d f


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Ephedr ine is an alkaloid extracted from

Ephedra

W l it h i i b i l i i i ti


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Welwitsch ia m irabi l is is an enigmatic

desert dweller

W l it h i i b i l i h t t


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Welwitsch ia m irabi l is has two strap-

shaped blades with basal meristem

Corm-like stem

Mi i t t b i l i f W l i t h i


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Microsporangiate strobi l i o f Welwi tschia

i t t b i l i f W l i t h i


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megaspo rang iate strob i l i of Welwitsch ia


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Welwitschia

mirabi l is

Native to Namibia, SW AfricaWith persistent basal meristem

for the elongation of two strap-

shaped blades, underground

gymnosperms 2013

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