Effect of photoperiod and temperature on the growth,flowering and dormancy of several varieties of alfalfa

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Authors Brubaker, Henry Allen, 1936-

Publisher The University of Arizona.

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STATEMENT BY AUTHOR

thesis has been submitted in partial fulfillment of for an advanced degree at the University of Arizona and in the University Library to be made available to bor- rules of the Library. .

Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the D&an of the Graduate College when in their judgment the proposed use of the material is ."in the interests of scholarship. In all other instances, however, permission must be obtained from the author.

SIGNED:

APPROVAL BY THESIS DIRECTOR

This thesis has been approved on the date shown below:

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ACKNOWLEDGEMENTS

The author wishes to express his sincere thanks and gratitude to

Dr. Martin A. Massengale for his invaluable assistance in conducting this study and his constructive advice and suggestions during the preparation of the manuscript.

, The author also extends sincere thanks to Dr. D. F. McAlister, in whose mind this study was born, for his help and advice during the course of the author s educational program.

Grateful appreciation is extended to Dr.. M. H. Schonhorst for

his time spent in discussion with the author and for his critical review of the manuscript.

Graduate study at the University of Arizona was made possible by a teaching assistantship from the Department of Agronomy. For this assistance, the writer is indeed grateful. ■

The author further wishes to thank his wife, Ann, for her con­tinued understanding and encouragement and for typing the manuscript.

■To all others who helped in any way and are not mentioned here,

the author is sincerely grateful.

TABLE OF CONTENTS

' TageList of Tables............................................... vLi s t o ju F DLguLX1 es.. ............................. V H-jL

INTEOOUCTION...................,............................. 1REVIEW OF LITERATURE?... ............................ 3

Photoperiodism and A l f a l f a , 3 Photoperiodism and Other Legumes..................... 6Temperature and Photoperiod,,...,........ . = ..... 8Hardening and Dormancy of Alfalfa.................... 12Geographical Origin of Plants and theirPhotoperiodic Response........................... 13

Light Interruption of the Dark Period..............«. 14

METHODS AND H A T E R I A L & . o . o . . . . 17Description of Varieties............................. 22

RESULTS AND DISCUSSION,...............___.................. 28Dry Matter........................................... 28Flowering............................................ 33Summer Height................................. 41Winter Height. ........ 50Crown D i a m e t e r s 59 Dormancy and Growth Habit... ..... 62

S U M M A R Y 9 . . . . . . . . . 6 5

« tt e 6 # * * » o » d e » ® o » « 9 d » <» a 0 ® e e d o e e e » 9 e e e » 6 « 08

APPENDIX 73

iv

LIST OF TABLES

Table Page1 Total yield of dry matter per sub-plot for

twelve alfalfa varieties grown under twophotoperibds ♦ 31

2 DuncAn* s multiple range test (14) for the differences in total yield of. dry matter among twelve alfalfa varieties grown under'-each photbperiod..»................. »> ... . 32

3 Summaries of the results■of the analyses of variance for per cent of plants in f lower . for a four-week period of the initial growth and each week after cutting for each growth

. .period..... .... ....... v... w....... 344 Summaries of the differences in per cent of

plants in flower between photoperiods for each variety for a four-week period of the initial growth and each week after cutting for eachgrowth period. . a . . 35

5 Summaries of Duncan’s multiple range tests (14) ?-. at the .05 level of significance for flowering, percentages for a four-week period of the initial growth and at weekly intervals after each cuttingof alfalfa varieties grown under long days... ......., 37

6 Summaries of Duncan’s multiple range tests (14)at the .05 level for flowering percentages for a four-week period of the initial growth and at weekly intervals after each cutting of alfalfa varieties grown under short days,........., „ v .. . 38

7 Summaries of the results of the analyses ofvariance of plant height for a four-week period of the initial growth and each week after cut­ting for each growth period. ..... 42

v

LIST OF TABIiBS (eont'd)

Table Page8 Summaries of the difference in plant height

between photoperiods for each variety for a four-week period of the initial growth and eachweek after cutting for each growth period............ 43

9 Summaries of Duncan1s multiple range tests(14) at the «05 level for plant height for a four-week period of the initial growth and each week after each cutting of alfalfavarieties grown under long d a y s * . . a . . . . 45

10 Summaries of Duncan/s multiple range tests (14)at the .05 level for plant height for a four- week period of the initial growth and each week after each cutting of alfalfa varieties grownunder short d a y s 46

11 Summaries of the results of the analyses ofvariance of plant height after the last cuttingin the fall (November 17, 1 9 5 9 ) 5 1

12 Summaries of the differences in plant heightbetween photoperiods for each variety after the last cutting in the fall (November 17, 1959)...,.*.,..*.*..,..,.,......**,.,.........*..., 52

13 Summaries of Duncan’s multiple range tests (14)at the *05 level of significance for plant heightunder long days after the last cutting in thefall (November 17, 1959), *, * , * *. . . ,..,*,V..*,*,.. 55

14 Summaries of Duncan’s multiple range tests (14)at the *05 level of significance for plant heightunder short days after, the. last cutting in thefall (November 17, 1 9 5 9 ) 5 6

15 Regression and correlation coefficients of rate of growth during the winter and during thespring. *. *... . . . . . . . . ...... . . .. ...o.o.o 58

16 Mean crown diameters of alfalfa of twelvevarieties grown under two photoperiods0Measurements taken February 6, 1960.,.....o........ 60

; ' '' / .'IVl

LIST OF TABLES (conti’d)

Table. . ■ ; , ^ ■ " Bage: V17 Mean croxto diameters of alfalfa plants of twelve

, varieties grown under two photoperiods, and a' summary of Duncan8s multiple range test at the

,05 .level of significance for varieties within a photoperiod. Measurements taken February 6,

. i 9 6 0 . , . . . . . . . . . . . , . . . . . ' : 6118 Visual ratings of the dormancy and growth habit

of alfalfa plants of twelve varieties grown .under two photoperiods. Ratings were made Feb­ruary 6, I960.......,,........».................... 63

vii

list of Figures

Diagram of field planting plan for photoperibd and temperature study of alfalfa varieties at the Campbell Avenue Farm, Tucson, Arizona, 1959- -I960. . ... o . e . e - e . . . . . « . e . ... « « . . * . o * . e e . . . . » . . . * . .

Permanent aiuminum curtains used to separatelong-day and short-day plots in photoperiodand temperature study of alfalfa varieties.....»...General view of long-day plots, showing the effect of harvesting varieties at different times. (Photograph taken August 7, 1959)..........General view of short-day plots, “showing the effect of harvesting varieties at different times. (Photograph taken August 7, 1959)..........Medicago falcata plants grown under long days.Note abundance of flowers. (Photograph taken June 19, 1959)......................................Medicago falcata plants grown under short days. Note lack of flowers. (Photograph taken June 19, 1 9 5 9 ) . . . . . . . . . . . . . . . . . . .Medicago falcata plants grown under long days. Note elongation of stems. (Photograph taken June 8, 1959)........*.,.................*.@.Medicago falcata plants grown under short days. Note lack of stem elongation. (Photo­graph taken June 8, 1959) ..,................... ...Rambler alfalfa plants grown under long days.Note height of stems. (Photograph takenMay 21, 1959).........................,............

Rambler alfalfa plants grown under short days.Note height of stems. (Photograph taken May 21, 1959) .....

INTRODUCTION

Alfalfa is the most important forage crop grown under Irrigated

conditions of the southwestern United States, This, area is also impor­

tant in the production of seed of many alfalfa varieties* It has long

been known that alfalfa responds to length of day and that temperature

affects these responses«, However3 little work has been conducted to

determine the basic nature of the photoperibdic response of alfalfa.

The effect of photoperiod on the adaptation of a variety is of

primary interest to agronomists, Some experimental work has shown that

the genetic composition of a variety was altered when seed was produced

outside of its region of adaptation. This shift in genetic composition

was attributed to the fact that the length of day under which the seed

was produced differed;from that of the area.for which the variety had

been developed.

Several studies have been done; relative to the development of a

test whereby plants of different varieties of alfalfa can be identified

and tested for varietal purity by varying photoperiods. Most of these

experiments have been conducted under controlled conditions and on

seedling plants. Little work has been done in the field or on plants

after they have passed the seedling stage of growth. Investigations of

the aforementioned problems have met with limited success primarily

because of the lack of basic knowledge of the effect of photoperiod on

alfalfa. ' , : - \ ,: • ■,. / -v . i ■ ' ,■■■ ■; • - .■

2

The climate of Tucson^ Arizona^ offers an * excellent opportunity

for studying photoperiodic responses of alfalfa under natural temperature

in the field. Daylengths during most of the growing season are short

enough to initiate short^'day • responses, . eliminating ' the need for dark chamberso Temperatures during the winter are sufficiently low to induce

expression of dormancy of winter-hardy alfalfas, without winter-killing the nonhardy varietieso The summer temperatures approach the maximum

encountered in any area where alfalfa is grown*This study was conducted under field conditions to observe the

photoperiodic responses of alfalfa at the various seasons, of the year9

and to compare the response of plants that have been clipped several times with the response of seedling plants*

REVIEW OF LITERATURE

Literature pertaining to the photoperiodic response of alfalfa is limited. Therefore, this review will present that literature which is related to alfalfa and that which will give some indication of the various factors and responses associated with photoperiodism. No attempt will be made to review the basic nature of this phenomenon.

Photoperiodism and Alfalfa

Some of the first work relating to photoperiodism in alfalfa was reported in 1921 by Oakley and Westover (31). They observed strik­ing varietal differences when seedings were made in the field during the fall and in the greenhouse under seven hours of light. Hairy Peruvian and Kansas Common were erect, sparsely branched, taller and more uniform than Grimm, Canadian Variegated and Medicago falcata. Medicago falcata plants were very short and had a rosette-like habit of growth;

These varieties were also seeded in the field during May and

June and in the greenhouse under natural winter daylengths plus artifi­cial light from sundown till 11:00 P.M. Under these conditions different results were obtained than when seedings were made in the fall and in the greenhouse under seven hours of light. A reversal in the order of height

and to a lesser degree a reversal of growth habit were noted under long days. Grimm and M. falcata grew erectly, had little branching and attained practically as great a height as any of the other three varieties.

. . . ... " - 3 " , v : ' ;;r; ' -

4

Oakley and Westover (31) stated^ HThe relation between locality of origin of the various alfalfas and their reaction to the day-night

period is shown consistently.1*Massehgale and Medler (26) grew cuttings of alfalfa plants,

selected for high seed production* under daylengths of 12 and 14 hours

and found that plants grown under the long-day conditions were taller,

Plants under 14 hours of light grew at a more rapid rate during the early stages than those under 12 hours of light* but alfalfa under the

shorter daylengths continued to grow for a longer period of time. The

regrowth made under 12 hours of light was taller and had longer inter­

nodes than the original growth under 14 hours. Increase in height of

the regrowth was thought to be due to higher temperatures. Alfalfa

plants growing under the longer photoperiod flowered freely whereas

those growing under. 12 hours of light flowered sparingly if at all,Coffindaffer and Burger (13) grew ¥arr.agans ett 5 Vernal and

Williamsburg alfalfa varieties under daylengths of 10* 14 and 16 hours.

They reported that the highest and lowest total yield of dry matter

occurred under the longest and shortest daylengths * respectively. An

increase in dry weight of seedling plants was also reported by Bula (8)

when photoperiods were increased from 14 to 17 to 20 hours. These

workers attributed the differences obtained to the effect of photo-

periodism* however* it would seem that the extended time of photosyn­

thetic activity may also have influenced their results.

The greatest differences in height between winter-hardy and

nonwinter-hardy varieties have consistently occurred under shorter

5

photoperiods, with the winter-hardy varieties showing the greatest

response (8, 29, 44, 45),

Seth and Dexter (45) studied the response of ten alfalfa

varieties to daylength* They used eight hours of daylight for a short- '

day treatment and eight hours of daylight plus six hours of fluorescent

light for a long-day treatment*. These workers found highly significant

differences, in the production of top growth from seedling alfalfa plants,

between photoperiods and between winter-hardy and nonwinter-hardy vari­

eties* Under short days, seedlings of California Common had the longest

stems and the highest yield of dry matter of top growth while Ladak had

the shortest stems and the lowest yield. Under long days, all the vari­

eties produced stems pf about equal lengthy however, Ladak had the

highest yield, while Hardigan and Caliverde were the lowest* A recum­

bent top growth was also noted in the Mnter-hardy varieties grown under

short days. Other workers (29, 44) have also reported an increase in

stem length of seedling alfalfa plants and small differences between

winter-hardy and nonwinter-hardy alfalfa varieties, when grown under

long days*

Considerable research has been conducted to determine the effect

of the area of seed production on a variety. Smith (46), Smith and

Graber (48) and Ganode (11) studied the effect of area of seed production

on Hanger alfalfa. These workers concluded that plants grown from seed

produced in the Southwest produced more tall seedlings than plants grown

from seed produced in Montana and other northern areas. Similar results

have also been obtained with Vernal,, Harragansett (47) and Rhizome (46) .

The explanation given by Smith and Graber (48) for the differ­

ence in seedlings produced from different seed lots is that under short

Southwestern days some plants grew taller and produced more seed than

othersg while in Montana under longer days3 all the plants grew to about

the same height and produced an equal amount of seed. Canode (11) stated

ftTt is probable that most varieties and regional strains of alfalfa have

individual plants whose stem elongation is inhibited and individual

plants whose stem elongation is not inhibited by short day lengths.**

Canode further stated that, in general, those varieties which have the

greatest winter survival tend to develop a much higher percentage of

plants with short stems when grown under short daylengths.

Photoperiodism and Other Legumes

Keller and Peterson (20) established that red clover (Trifolium

pretense L») was a long-day plant» Their work showed that numerous

flowers were produced when plants were grown under 18-hour days, but no

flowers were formed under 10-hour days. These investigations also showed

that red clover attained a greater height under longer daylengths, and

the number of leaves and tillers was greatest under short days. Forage

yield, however was not affected by photoperiod. Later experiments con­

ducted by Bula (9) did show that the accumulation of dry weight was

increased as the daylength was increased. The greatest expression of

inherent variability in growth habit was reported by Ludwig et al«, (24)

when red clover plants were grown under short days.

Ladino clover has been classified as a long-day plant (23) «

Variability among clones was accentuated under shorter daylengths, but

■ ' ; 7 ■

there was little difference among lines in response to photoperiods of

15 hours or more (23),

Smith (50) reported that length of day had a pronounced effect

on the weight of top growth and storage of food reserves in the roots

of biennial white (Melilotus alba L,) and yellow (M. officinalis I*.)

sweet clovers. Plants grown under long days produced more top growth?

but there was less storage of food reserves when compared to plants

grown under short days. Plant height, internode elongation and total

plant weight were also greatest under long days. There was almost no

internode elongation^ however, under day§ of less than 12 hours of

light, Peiters (39) also noted an increase in elongation of internodes

of annual a,nd biennial white sweet clover when grown under long days.

Crimson clover (Trifolium incarnatum L,) was reported to flower earlier as the length of the photoperiod increased from 8 to 20 hours :

(21). Under long days, the plants produced smaller seed heads,, fewer

leaves, less branching and a greater height than under short days.

Two annual species of lespedeza. Common (Lespedeza striata Thuhb.) 1

and Korean (h. stipulacea Maxim) have been classified as short-day -..plants requiring less than 14 hours of light to flower (28). Bates (2) tested

several strains of a perennial species of lespedeza (L. cuneata Don)

Under photoperiods ranging- from 8 to 15 hours, and he noted considerable

variation among strains. There were no strains, however, that made ma#- ;

imum growth with less than 14 Hours of light. Strains * having the widest r

range of adaptation made satisfactory growth at several different photo-

periods: V;: -:;": - : ■ ;

8

Joffe (18) studied the effect of photoperiod on birdsfoot trefoil (Lotus cornlculatus L.) and reported that plants kept under short-day conditions exhibited a rosette type of vegetative growth. Similar plants under long days produced flowers and were erect in growth.

An extensive examination of the photoperiodic response of beans (Phaseolus spp.) was made by Allard and Zaumeyer (1).. They concluded that most species were either short-day plants or day-neutral; however, the species J?, coccineus L. was reported as being a long-day type.These workers also noted that length of day determined the growth habit in many species. Changing the daylength, in many cases,, would change the plant from a twining to bush type or vice versa.

Some work conducted on the response of Mandarin, Peking and

Biloxi soybeans (Soja max (L.) Piper) to photoperiods ranging from 3 to 17 hours indicated that final height of the plants increased with an increase in photoperiod (53). Borthwick and Parker (6) found some vari­eties of soybeans to flower only under short days, while others flowered at all photoperiods, including continuous light.

Temperature and Photoperiod When alfalfa plants were grown under a 12-hour day and at 60° F.

under controlled conditions, Schonhorst jet jal. (44) were able to separate

seedlings of ten varieties and a mixture of two varieties into three groups according to the magnitude of the variance in height among indi­vidual plants. The first group, which had the shortest stem length and the smallest variance, included Vernal, Ranger, Narragansett and Grimm.

The second group, which had slightly longer stems and significantly

larger variances, included Buffalo, Atlantic and Du Puits. The last

group, which had much longer stems and more than twice the variance of the second group, was composed of African and a mixture of 50 per cent ‘ African and 50 per cent Ranger. The differences among varieties were increased when the daylength remained 12 hours, but the temperature was shifted from 60° F. during the light period to 30° F. during the dark

period.Nittler and Gibbs (29) grew alfalfa seedlings of several vari­

eties under different photoperiods, colors of light and temperatures.A combination of red and green light for eight hours proved to be the most effective treatment in producing differences between northern and

southern varieties. When temperatures were lowered, these differences increased. Wittier and Gibbs concluded that color of light and photo­period were not the only factors controlling dormancy of northern alfalfa since the growth of these varieties was much more limited at relatively low temperatures than. at.high temperatures. Southern types, however, made relatively good growth at low temperatures.

In greenhouse experiments by Roberts and Struckmeyer (42), seed- setting in alfalfa was observed to respond differently to photoperiod at various temperatures. In later studies... (43), these same workers reported that at temperatures of 70° F„ ho flowering occurred under

either a long or a short photoperiod, at 65° F. flowering occurred only under long photoperiods and at 55° F. flowering occurred under both long

and short photoperiods. Long photoperiods consisted of natural winter light plus artificial light until midnight. The short photoperiod con­

sisted only of natural winter light ranging from nine and one-half to ten hours duration. These workers also reported that red clover flowered

only under the long photoperiod* and that flowering was suppressed by

a temperature of 70° P. Flowering of red clover was promoted* however* by starting the plants in a cool temperature and transferring them to an

intermediate temperature* rather than keeping the plants under the same

temperature continuously. High temperatures at night caused the flowers

to abscise, Roberts and Struckmeyer (43) concluded from their,work that

photoperiod was the primary factor for a certain range of temperatures* but with many plants it was only a contributing and not a controlling

factor in the formation of flowers,

Knight and HoHowell (21) obtained similar results with crimson

clover as reported for red clover by Roberts and Struckmeyer (43), The

earliest flowering occurred when plants were shifted from outside cold

frames into a greenhouse with relatively high temperatures. High,.tem­peratures at night from germination to the. time of maturity inhibited flower production. With biennial sweet clover* cool temperatures and long days (17 hours) caused a considerable delay in flowering when com­

pared with warm temperatures and long days (50),

Parker and Borthwick (34) grew Biloxi soybeans under a 16-hour photoperiod and observed that they remained vegetative regardless of the

combinations of temperatures applied during the light and dark periods.

However* with photoperiods less than the critical limit of 13 1/2 hours, great variations in the extent of floral initiation were induced by vari­

ations in temperature during the dark period. In further work with Biloxi soybeans (35), these workers reported that when a single leaf was held

at temperatures less than 50° F, or above 90° F,, during a photoperiodic

induction period of five days, floral initiation was greatly inhibited.

11

Their conclusion from this study was:ifThe inhibiting effect of low temperature on floral

initiation in Biloxi soybean plants appears to be the result of its effect on the photoperiodic reactions occurring in the leaf blade during the dark period, rather than through its effect on translocations of a flower-inducing stimulus from the leaf to the terminal meristems or its effect at the terminal meristerns upon the differentiation and development of flower buds/1

Roberts and Struckmeyer (42) were not successful in attempts to

induce bolting of celery (Apium graveolens) by four temperature and

photoperiodic environments (cool - short, cool - long, warm - short, and

warm - long). Plants in a cool greenhouse and under normal winter day-

lengths at Madison, Wisconsin, did bolt and became reproductive as the

days lengthened with the advent of spring» The celery plants that had

been under the short day and cool temperature treatment began to bolt in

the warm weather of June while still under short days* These workers

stated, nThis shows a reaction to a varying length of day at uniform

temperature as well as to varying temperature with a uniform length of

day.'"'' ' , . V . - /Knot (22) suggested that for spinach, the photoperiod may be

less important than temperature in determining the reproductive response*

In his studies, the photoperiod necessary to cause appearance of seed-

stalks was apparently determined by the temperature during early growth

complemented by the temperature during the later stages of development*

A combination of cool temperatures and short days was required

for flower initiation in Kentucky bluegrass (Foa pratensis L„), since no

flowers were formed under any combination with either warm temperatures

or long photoperiods (38), The subsequent development of flowers,

however, was reported to be favored by slightly warmer temperatures, and longer photoperiods than those required for flower induction.

Hardening and Dormancy of AlfalfaTysdal (55) studied the hardening processes of Turk is tan, Grimm

and Arizona Common alfalfas in the greenhouse, and reported that these processes responded more to short days in the hardy than the nonhardy varieties. He also noted that alternating temperatures between the light and dark periods, with the lowest temperature during darkness, favored the development of cold resistance particularly if accompanied

by shortening daylengths.

The development of cold resistance of.Medicago falcata. Ranger and Arizona Common alfalfas was studied under field conditions at Palmer, Alaska, and Madison, Wisconsin (10). At Palmer, Alaska, M. falcata and Ranger developed cold resistance when low temperatures occurred in late September and early October although the daylengths were near 12 hours. However, Arizona Common did not develop cold resistance until about mid- October when the daylengths were near ten hours. Ranger and M. falcata developed cold resistance more rapidly, and M. falcata developed cold resistance to a higher level at Palmer, Alaska, than at Madison, Wiscon­sin. These workers concluded that temperature and daylength appeared to

be major climatic factors influencing the development of cold resistance in alfalfa.

The metabolic changes occurring in alfalfa during and after cold

hardening and freezing for four hours at -20° C. were studied by Swanson

and Adams (54). They found that length of day did not play a significant part in influencing respiration during the hardening process. However,

■ ' ' ■ ; 13

when post-freezing respiration was considered, the daylength during the hardening period was found to be influential only in the case of hardy varieties. The highest and lowest respiratory activity after freezing

occurred when plants were hardened under short days and alternating tem­

peratures, and long days and high temperatures, respectively.Hoshkov (27) suggested that frost resistance of perennials was

dependent upon their photoperiodic response. He theorized that frogt resistance, frequently depends not on the critical winter temperatures, but on conditions, especially photoperiod, during the vegetative period of growth.

Geographical Origin of Plants and their Photoperiodic Response

Ramaley (40) analyzed the influence of supplemental light on the flowering of 100 species of plants. She noted that most plants which flowered earlier under long days were natives of the temperate zone while a large proportion of those that were not affected or were retarded in flowering were natives of the tropics. There were few, if any, tropical , species that flowered earlier under long days.

An extensive study of the photoperiodic responses of several geographical, strains of side-pats grama grass (Bouteloua curtipendula

(Michx.) Torr.) was made by Olmsted (32, 33). He reported that strains found in Borth Dakota were long-day plants with a critical photoperiod for flowering of about 14 hours. Strains obtained in Bebraska, Oklahoma,

Kansas and New Mexico included many long-day types. Within a strain, the

dories taken from Oklahoma and Bew Mexico were the most diverse in response to photoperiod. Strains from Oklahoma were found to be intermediate or

14

long-day types having a short critical photoperiod of from nine to thir­

teen: hours* Clones from southern Texas and southern Arizona were either

intermediate or short-day types and did not flower under photoperiods

with more than approximately 14 hours of light. This information would

indicate that it is possible to have, within the same species, strains

of plants that range from short-day to long-day types.

Light Interruption of the Dark Period

Borthwick (4) reported in 1947 that photpperiodic experiments

using light interruption of the dark period were the same in principle

as those in which natural daylengths were extended with artificial light

at either the beginning or end of the dark period. The light energy

required to promote flowering of Wintex barley (Hordeum vulgare L,) s a

long-day plant, if applied continuously throughout the dark period, was

determined.to be about 10 times greater than if applied within a two-hour

interval near the middle of the dark period (5),

Interruptions in the middle of a long dark period with 100 foot-

candle-minutes of light were effective in causing initiation of flower

primordia of the long-day plant Hyoscyamus niger (36), Oats in a vege­

tative stage of growth have been induced to flower by interrupting the

long dark period with one hour of light at midnight (58). Spring wheat

was grown under cycles of 16 hours of light and 8 hours of dark in the

experiments of Riddell et al. (41). These workers found that light of .

one-half hour duration applied in the middle of the dark period resulted

in an acceleration of plant development when compared with no inter­

ruption. Interruptions as brief as 30 seconds with 15 foot-candles of :

15

light have prevented the formation of flower primordia in short-day

Biloxi soybeans (37) »

Knight and HoHowell (21) studied seedling plants of crimson

clover at State College, Mississippis under natural winter daylight,

under natural daylight plus a light break of 30 minutes applied in the

middle of the dark period and under a 16-hour daylength produced by extending the natural daylight with incandescent light. Plants under all

photoperiods received temperatures of 50o-55O F„ at night and 70o-80° F.

, during the day. These workers concluded that the light interruption in

the middle of the dark period was not effective in inducing early flower­

ing in crimson clover since plants grown under this condition flowered

40 days later than plants grown under the 16-hour day, and only 20 days

earlier than plants grown under natural daylight. ’

The plants used by Knight and HoHowe 11 were seedlings, and it

would appear to this writer that the earlier flowering obtained under

the 16-hour day in their studies was at least partially a response to

. greater photosynthetic activity rather than to photoperiod. Under the

16-hour day, the plants may have developed faster than under the natural

day plus light interruption, because of greater amounts of photosynthate.

It is possible that.the true photoperiodic effect was exemplified by the earlier flowering of plants under the light interruption treatment when

compared with those plants growp under the natural daylength. \

The effect of light interruption during the middle of the dark

period on Ranger and Vernal alfalfa was studied under field conditions

at Tucson, Arizona (25). Light interruption of the dark period resulted

16

inla decrease in nutnber of days between cutting arid the appearance of the first flower in clones of both varieties, and a decrease in plant height and plant weight of Vernal.

. ' ' ■ ; : _ , miHODS A m MATERIALS / : " : ■

This study was conducted under field conditions at the Univer­sity of Arizona Campbell Avenue Farm, Tucson, Arizona. The experimental work was initiated March 18, 1959, when the alfalfa was seeded, and the work reported here was terminated April 1, 1960. Twelve varieties of alfalfa were compared under two photoperiods.

The experimental design was a split-plot randomized block With

photoperiods as whole-plots and varieties as sub-plots. Four replications were used. For practical' reasons, the daylength treatments were hot randomized over the four replications. The long-day treatments for rep­lications I and II and for replications III and IV were placed adjacent

to each other. This reduced the number of curtains which might have been needed if the daylength treatments were assigned at random. The . varieties were randomized within each whole-plot. Figure I shows a dia­

gram of the field planting plan.The whole-plots consisted of two photoperiods, long-day and

short-day. The long-day treatment was produced by interrupting the . middle of the dark period with approximately 30 minutes of light from

eight, Number 2 reflector base, photoflood lamps. The light bulbs were suspended five feet above the ground level in each long-day plot. Light intensities were measured by a Weston light meter. The.lowest inten­sity recorded at the ground level was ten foot-candles. Thus, the

17

18

Short Day"

Rep IVLong Day •"

Long Day

Rep III.-

Short Day

v. 'Short Day ■

Rep. II

Long Day

Long Day

Rep IShort Day

8 10 9 1 3 4 5 6 7 2 11 12Curtain

2 ' 9 5 3 4 7 10 6 1 12 8 11

5,- 3 6 8 4 12 2 11 10 1 9 7

Curtain' 7 9 -3 6 10 ..1 5 2 12 8 4 11

8;; ' 2 1 4 6 10 3 9 11 7 ■ 5 12

Curtain

L 5 11 ■9 2 12 10: 3 4 6 7 8

6 12 11 4 7 3 8 1 10 5 2 9

Curtain7 ■ ■ 6 8 1 5 11 9 2 12 10 3 4

A

3'

12'

36 12'

The following varieties were used;1. Medicago falcata 7. Buffalo2. .Rambler 8. Lahontan3. Vernal 9. Chilean4. Ladak 10. Caliverde5. Ranger 11. Moapa6. Atlantic 12. Hairy Peruvian

Figure 1. Diagram of field planting plan for photoperiod and tem­perature study of alfalfa varieties at the Campbell Avenue Farm, Tucson, Arizona, 1959-1960.

19

minimum amount of light received at any position in a long-day plot was 300 foot-candle-minutes.

The natural daylength constituted the short-day treatment. In this study, both the long-day and the short-day treatments received essentially the same amount of sunlight for photosynthesis. It was assumed for this study that the amount of photosynthate produced during the 30 minutes of light interruption was negligible; therefore, any responses obtained may be considered photoperiodic in nature. The short- day and long- day plots were separated by aluminum curtains that were five feet in height, figure 2 shows one of these curtains.

The following varieties were used: Medicago falcata. Rambler,Vernal, Ladak, Ranger, Atlantic, Buffalo, Lahontan, Chilean 21-5, Cali- verde, Hoapa and Hairy Peruvian. These 12 varieties were seeded with Certified or Breeder seed and by hand at one-half inch intervals and later thinned to 12 plants per row with spacings between plants of

approximately one foot. Each sub-plot contained 24 plants of the same variety and consisted of two rows of alfalfa 12 feet long and two feet

apart. Treble superphosphate was broadcast at the rate of 200 pounds of per acre previous to planting and was disked into the soil. The

seed was inoculated just prior to planting. Irrigations were frequent enough to provide maximum growth, and all weeds were controlled by hand

methods. Insects were controlled by spraying or dusting-with the recom­mended insecticides when they were present in sufficient numbers to ' cause damage.

Height measurements were taken on eight plants in each sub-plot at weekly intervals. All measurements were obtained by measuring the

20

Figure 2. Permanent aluminum curtains used to separate long-day and short-day plots in photoperiod and temperature study of alfalfa varieties.

extended length (to the nearest inch) from the ground level to the ter­

minal bud of the lohgest stem on the plant. The measurements were made

on every third plant in each row to eliminate any opportunity for bias to enter into the selection of plants.

The number of plants in flower was also counted for each sub­plot at weekly intervals. Because some plants were missing, these data were recorded as percentages.

Each variety under each daylength was harvested when the average : number of plants in flower, over the four replications, was 90 per cent. This harvesting procedure resulted in an unequal number of cuttings for the different varieties and in some cases for the same variety under different photoperiods,. Harvests were made by hand clipping the plants with Wiss hedge clippers at a height of two to three inches. At each

harvest,, all. the plants in a sub-plot were cut, placed in paper sacks and dried with forced air at 160-170° F. The weight of the dry matter

for each sub-plot was recorded.On November 17, 1959, all the sub-plots were harvested regardless

of per cent of plants in flower. This harvest was made to allow equal expression of winter growth and dormancy of each variety. After this cutting, height measurements were taken at intervals of two weeks. The

longer interval between measurements was used because of the slow rate of growth during the winter months. The last height measurement was made on April 1, 1960, after all the varieties had broken dormancy and begun spring growth. ,

On February 6, 1960, the diameter of the crowns of all plants was measured parallel with the row and at right angles to the row. The

diameter of the base of the plants, including the point where rhizomes emerged from the soil, was considered to be the crown. New plants originating from the roots of Ratiibler were not considered to be part of the crown. These two measurements were averaged, and the data were recorded as the average diameter of crowns. Also at this time, each plant was given a visual rating in relation to its dormancy. The rat­ings were dormant and nondormant. Two classes of dormant plants were observed: (1) plants that had no visible top growth, and (2) plants that

had top growth but no stem elongation. The nondormant plants were fur­ther rated according to growth habit as prostrate, semi-erect and erect.

Statistical analyses were conducted on all quantitative data.

Desctiption of Varieties It is known that hardy varieties respond differently than non­

hardy varieties to photpperiodi therefore, a wide range of hardiness is

necessary to give the complete response of alfalfa. The varieties used in this experiment were chosen to represent the complete range of winter hardiness. A brief summary of information pertaining to the history/ ancestry;: and place of origin of the alfalfa varieties used in this study is presented here.Medicago falcata

Medicago falcata was introduced into the United States in 1898 from Siberia (30). Oakley and Westover (30) described this perennial species as varying in its growth habit although the most common forms were procumbent and had a much branched -foot system. This species of alfalfa is extremely winter hardy. Crowns of the plants are generally

produced below the surface of the ground which helps the plants to with­stand extremely cold temperatures. The distinguishing characters of K. falcata are its yellow flowers and falcate seed pods (30).Rambler

Rambler is a synthetic variety released for sale in Canada in 1955 by the Canada Department of Agriculture (17). Heinrichs and Bolton (17) reported that during the breeding program, plants were selected for winter hardiness, drouth resistance, creeping root habit, seed yield and forage yield with some emphasis on resistance to bacterial wilt, and crown rot. The variety is composed of seven nonrelated clones. Six of these clones were selected from numerous crosses involving Ladak (H. media Pers.) and M. falcata, and one clone was selected from crosses involving Ladak, M. falcata and Rhizoma (M. media Pers.)(16). These workers reported that the creeping root character was possessed by about 65 per cent of the plants in Rambler.Vernal . v. ' ' . ■ 1 • -

Vernal alfalfa was developed at the Wisconsin AgriculturalExperiment Station with the United States Department of Agriculture

cooperating. This variety was released jointly by the Wisconsin and

Utah Agricultural Experiment Stations in 1953 (7) . Brink _et _al. (7)reported that 50 per cent of the germ plasm of this synthetic varietywas derived from six Cossack plants. The other 50 per cent was .derivedfrom five second-generation plants obtained from crosses of diploid M.falcata plants with one Ladak plant and one winter-hardy plant of Kansas Common. Vernal plants also were reported to have a broad crown with a freely branching tap root, a high degree of winter hardiness and resist-- ance to bacterial' wilt (7).

24

Ladak ' ' : : -The first seed of Ladak alfalfa was imported into the United;

States from the province of Ladakh in northern India in 1910 (56).According to Westover (56), this variety was first thought to be M. faleata, but it was later found to be a hybrid between M. falcata and M. sativa. When Ladak was first grown in this country, most of the charac­teristics common to M. falcata predominated. These characteristics included general habit of growth, shape of pods and color of flowers.In the years following introduction; the flower color changed from pre­dominantly yellow to predominantly purple as the result of natural cros­

sing of Ladak with other purple-flowered varieties. Ladak is characterized by a vigorous first growth, a high degree of resistance to cold and drouth, early dormancy in the fall and slow recovery after cutting (56).

Ranger ''' , ,'':: '; ... ) / ' : C \Ranger alfalfa was released for seed increase in 1940 by the

Nebraska Agricultural Experiment Station and the United States Depart­ment of Agriculture. Breeder seed of this synthetic variety was obtained by mechanically mixing seed fromjfive selected strains of Cossack,

Turkistan and Ladak (19). Forty-five per cent of this seed was from one strain of Cossack, 45 per cent from 3 strains of Turkistan and 10 per cent from one strain of Ladak. The wide use of this variety is due to

its winter hardiness and resistance to bacterial wilt (19). ‘Atlantic' ' ■ ■ ’

Atlantic alfalfa was developed at the New Jersey Agricultural Experiment Station and was released for seed increase in 1940 (16).This variety resulted from a program of maternal line selection in which

100 strains were selected and intercrossed from the following varieties and strains of alfalfa: Hairy Peruvian, Highland Utah, Grimm, Cossack,Hardigan, Le Beau, Canadian Variegated, Kansas Common, Montana Common, Ladak, several strains from China, Turkey and Iran, 12 miscellaneous strains of M. sativa and 7 strains of M. falcata from Turkistan. Three : synthetic varieties were developed from this material, and seed of these synthetics was mixed in equal quantities to produce Atlantic. Atlantic is a high yielding alfalfa in the northeastern United States where bac­terial wilt is not a problem. Hanson (16) reported that this variety was extremely variable in its morphological characteristics.Buffalo -

Buffalo alfalfa was obtained by close breeding and selection from ah old strain of Kansas Common (15). This variety was developedby personnel of the United States Department of Agriculture and the Kansas Agricultural Experiment Station. The principal advantage of Buffalo over Kansas Common is its resistance to bacterial wilt. Grand-

field (15) stated that the range of adaptation of Buffalo extends farther north than that of Kansas Common.Lahontan ■ ■

Lahontan alfalfa was developed by personnel of the United States Department of Agriculture and the Nevada: Agricultural. Experiment Station

and was released by the Nevada and California Agricultural Experiment

Stations in 1954 (49). It is a moderately winter-hardy, synthetic variety. Lahontan consists of five clones selected from Nemestan. The

breeding program that developed this variety was successful in combining resistance to both the stein nematode and bacterial wilt. Although

2.6;

resistance to the spotted alfalfa aphid was not a factor included in the

initial breeding work, Lahontan has proved to be highly resistant to this insect (49).Chilean 21-5-

Chilean alfalfa was introduced into California from Chile in the early 1850fs. From California, it gradually spread throughout the western

United States. There is no record of its first introduction into Arizona. Chilean 21-5 resulted from a single plant selection made at Yuma, Arizona. Seed was collected from 1000 plants at random in an old field of Chilean,

and planted in progeny rows of 10 plants per row. . Plant number five in row twenty-one was selected because of its superior seed yield, leafiness and fine stems. The variety Chilean 21-5 was first grown, commercially in 1934. It is a nonwinter-hardy variety that exhibits some dormancy during the winters in Arizona.Caliverde ' .. ■ .

Caliverde was developed at the California Agricultural Experi­ment Station, and seed was made available to farmers in the fall of 1952. This variety was developed through a backcross breeding program in which Turkistan was crossed with California Common, and the resulting genera­tions were backcrossed to California Common. The result of this program was an improved California Common which possessed resistance to bacterial wilt, leafspot and mildew. Caliverde is not winter hardy (52), but

exhibits some dormancy during the winters in Arizona.

If The information on Chilean 21-5 was obtained by personal communication with Dr, W. S. Bryan, Plant Breeder, Arizona Agricultural Experiment Station, Tucson, Arizona.

Moapa ■ . .

Moapa was developed at the Nevada Agricultural Experiment Station with the United States Department of Agriculture cooperating and released jointly by the Arizona, California and Nevada Agricultural Experiment Stations in 1958. This synthetic, nonwinter-hardy variety consists of nine clones of African. All clones were selected because of their high

resistance to the spotted alfalfa aphid. Moapa is much like African in its growth habits and region of adaptation. In resistance to the spotted

alfalfa aphid, Moapa is slightly higher than Lahontan. It is more resist- ant to' bacterial wilt than African, but; less than Ranger (51) ,Hairy Peruvian

Hairy Peruvian was introduced into the United States from Peru in 1899 by the United States Department of Agriculture (57). According to

Westover (57), the abundance of hairs on the stems and leaves was the characteristic from which Hairy Peruvian received its name. Hairy Peru­vian has been characterized by its ability to grow in cool weather and under short days. This variety has demonstrated its ability to grow later in the fall and begin growth earlier in the spting than most nonhardy varieties of alfalfa. It. is a nonwinfer-hardy variety and cannot be grown

where the temperature falls below 10 -F, (57), , _ : :v

RESULTS AND DISCUSSION

Data were taken on the following characteristics: total dryweight of top growth; per cent of plants in flower and plant height tiur- - ing the growing season; plant height during the winter; diameters of crowns; dormancy and growth habit during the winter. Statistical analyses were conducted on all the data except dormancy and growth habits. All standard errors were calculated by the formulas presented by Cochran and Cox .(12) . These data will be reported under their respective head­ings,, The mean figures for each variety9 under both photbperiods* which were included in the analyses of flowering percentages and plant height during the summer and winter9 are presented in the Appendix.

Dry Matter / 1 _The yield of dry matter produced at each cutting was recorded

for each sub-plot* The yield for each cutting appeared to be more

dependent upon the time between cuttings than on photoperiods or varieties. Since the per cent of plants in flower was used as a criteria for.har­vesting, the yield for each cutting was more a measure of the rate of flowering than a measure of production of top growth. For the above reasons, only the total yield will be presented here. Figures 3 and 4 show the effect of harvesting, varieties at different times.

An analysis of variance was conducted oh total yield of dry matter per sub-plot. This analysis showed that there was no difference

28

29

Figure

Figure

General view of long-day plots, showing the effect of harvesting varieties at different times. (Photograph taken August 7, 1959)

General view of short-day plots, showing the effect of harvesting varieties at different times. (Photograph taken August 7, 1959)

between photoperiods, highly significant differences among varieties and a highly significant interaction between photoperiods and varieties.The difference between photoperiods for each variety and the number of times that each variety was cut under each photoperiod are presented in Table 1. The differences among varieties for each photoperiod, as deter­mined by Duncan's multiple range test (14), are presented in Table 2.

The varieties Buffalo, Lahontan, Chilean 21-5, Moapa and Hairy Peruvian produced significantly greater amounts of dry matter under natural daylength than under long days (Table 1). These results are not in agreement with the findings of Bula (8), Coffindaffer and Burger (13) . and Seth and Dexter (45). These workers reported a greater production of dry matter by seedling alfalfa plants when grown under long days. The. lack of agreement in the result of this study and those of the afore­mentioned workers may indicate that the response of seedling plants to photoperiod differs from the response of mature plants that have been clipped several times. The total yield in this experiment was the sum of the yields of several individual harvests. Long days in all of the above studies (8, 13, 45) were produced by extending the natural light period with artificial light. The extended light period may have increased the amount of photosynthate produced under long days. It was assumed

that the light interruption of the dark period which was used in this study to produce long-day effects, produced very little, if any, photo­

synthate.There were more varieties included in the highest producing group

under short days than under long days (Table 2). It is interesting to

31

Table I, Total yield of dry matter per sub-plot for twelve alfalfa varieties grown under two photoperiods.

Long day Short dayVariety Mean per

sub-plotHo.. of

, cuttingsMean per

, sub-plotNo. of cuttings

Difference % long-short

(grams) (grams) (grams)M. falcata 1722 2 1854 2 -132Rambler 4462

. 4 3920 . ■ 2 +542Vernal 4535 . 5 4852 4 -317Ladak 5068 ■: . 5 4700 4 +368Ranger 5028 : : 5 5166 5 ' -138Atlantic 5130 5 5577 4 -447Buffalo 4126 5 5508 5 -1382**

Lahontan ,3602 • 5 5531 4 -1929 **

Chilean 21-5 4272. :v 5 , ; 5242 ... 5 -970 *

Caliverde 4206 ■ 6 4604 5 -398

Moapa 4061 7 4916 6 -855 *

Hairy itecuvian 4303 6 5588 5 -1285 **

* Significant at .05 level: LSD = 640** Significant at .01 level: LSD ~ 1014

32

Table 2„ Duncan8s multiple range;test (14) for the differences in total yield of dry matter among twelve.alfalfa varieties grown under each photoperiod.

Long day Short dayVariety Mean per sub-plot i Variety Mean per sub-plot

; : (grams) - , (grams) ' 'Atlantic 5130 1 Hairy Peruvian . 5588 a

Ladak 5068 a 1 Atlantic 5577 aRanger 5028 a ’ Lahontan 5531 aVernal 4535 ab * Buffalo 5508 aRambler 4462 ab ' Chilean 21-5 5242 ab

Hairy Peruvian 4303 be ' Ranger 5166 abChilean 21-5 4272 be " 1 Moapa : 4916 ab

Caliverde 4206 be 1 Vernal 4852 ab

Buffalo 4.126 be 1 Ladak 4700 b

Moapa 4061 be ’ Caliverde . 4604, b

Lahontan 3602 c ’ Rambler 3920 c

M. falcata 1722 d ’ M. falcata 1854 d

_!/ Mean values followed by the same letter are not significantly different at the .05 level.Standard error for comparing varieties within a photoperiod: Sj = 226.7.

note the relatively low production of dry matter of Medicago falcata under both light periods*

Flowering

The summaries of the results of the analyses of variance for per cent of plants in flower at weekly intervals after seeding and after cutting for different growth periods are presented in Table 3* For the

analyses of variance* the percentages were transformed to angles whose sine is the square root of the percentage: angle = arcsin\/percentage (3)These transformations were performed to satisfy the assumptions of the

analysis of variance.The number <>f varieties included in the analyses varied for each

growth period* because the number of cuttings was not the same for all

varieties (Table 1) » Chilean 21-5 was not included in the analyses for the September-October growth period, because there were more than 15

days between the respective dates of cutting of the plants under long days and short days. All varieties included in the analyses for each growth period met this requirement *

The interaction between photoperiods '.and varieties was significant: in most cases. This indicated that all varieties of alfalfa did not show the same flowering response to photoperiods.

The summaries of the differences between daylengths for each variety are presented in Table|4«. These differences were determined by the method of the least significant difference between two treatment

means. The five per cent level of significance was used. The first

growth period represents the seedling response to photoperiodi and the

Table 3. Summaries of the results of the analyses of variance for per cent of plants in flower for a four-week period of.the initial growth and each week after cutting for each growth period.

Growth Periods

Source of variation

May - June June - JulyWeeks after seeding '

.9 . 10 11 *12 - * i • 2 • 3July' Aug. - Sept.

Weeks after cuttingSept# - Oct.

2 1 2

Ehotoperiods 'k'k **.i..... — ... ..— ...' NS NS NS NS * ** MS. NS NS NS k k US * -kk

Varieties. ** ifk ieit ** * * ** icit ** ** ‘frfc NS * **.**■ US ** 'fek kk kkInteraction ' ** ** Ng * 1 ** US _ * irk kk NS NS NS MS US * k kk kk

Rambler!/ 5 Vernal Rambler Ranger VernalVernal ’ Ladak Vernal Chilean 21-5 LadakLadak * Ranger Ladak Caliverde RangerRanger ’ Atlantic Ranger Moapa . AtlanticAtlantic * Buffalo Atlantic Hairy Peruvian BuffaloBuffalo ’ Lahontan Buffalo - LahontanLahontan 1 Chilean 21-5 Lahontan CaliverdeChilean 21-5 * Caliverde Chilean 21-5 MoapaCaliverde 1 Moapa Caliverde Hairy PeruvianMoapa 1 Hairy Peruvian MoapaHairy Peruvian « Hairy Peruvian

* Significant at the .05 level.** Significant at the ,01 level.

: _!/ The varieties.included in the analyses for each growth period are listed under that growthperiod. .

Table 4, Sutiimaries of the differences in per cent of plants in flower between photoperiods for each variety for a four-week peribd of the initial growth and each week after cutting for each growth period.

; ■ . ’ '' ' . ■ - •____ Growth PeriodsMay - June June - July July - Aug. Aug.. - Sept. . Sept. - Oct.

Weeks after seeding' * ;. ' ~ ~ V ' • Week's after cutting ' 'Variety - ... 9 .10 11 12 - !

1 1 2 3 ... .1 2 3 . . 1 2 3 . 4 1 .2 3 4 . 5 - .

Rambler L , L - X •f

■ i NS .NS NS-

Vernal L L L X i"i.-. S NS - s ; X L X; . NS NS L L L

fadak L L L L i NS L X L X L NS NS L I LRanger L X X i NS NS NS NS L L NS L NS L NS NS X t LAtlantic t L X - x . i

i X X NS : NS L L NS NS X X y

Buffalo L X X NS X X X NS X L NS .S' s S NSLahontan L L X X i NS L NS: NS L L NS NS NS L XChilean 21-5 L L X X i

i NS NS NS S NS S NS L L L

Galiverde L ; L L -L * S ;s S S S s NS S NS I S' S NS NS NS •Moapa L L L L i s s NS , s NS S X NS NS NS s •s S NS NSHairy Peruvian X L X L i

ts s NS s X X NS NS NS NS X L L L NS

1/ NS represents no significant difference between photoperiods; L represents significantly higher flowering percentages under long days; S represents significantly higher flowering percentages under short days. -

36

first week listed for this period is the ninth week after seeding^ Dur­ing each growth period, no analyses were made after one variety under either daylength had been harvested.

All varieties flowered earlier under long days than under short days during the initial growth after seeding.

During the June-July growth period, the nonhardy varieties (Cali-

verde, Moapa and Hairy Peruvian) flowered earlier under short days, while the hardy varieties tended to flower earlier under long days. In general, this same response was noted for the July-August growth period except for

Hairy Peruvian.Near the end of the September-October growth period, it appeared

that the nonhardy varieties were beginning to show no response to day- length. However, these varieties, with the exception of Hairy Peruvian, flowered earlier under short days during the. first part of this growth period. Hairy Peruvian appeared to respond more to short days during.June and July when temperatures were high and natural daylengths were longest. However, this variety became more responsive to the long-day treatment as natural daylengths shortened and temperatures lowered dur­

ing September and October. 'No explanation is offered for the earlier flowering of Buffalo

under short days during September and October and of Vernal during June

and July. • , 'Summaries of the differences in flowering percentages among

varieties for long days and short days are presented in Tables 5 and 6, respectively. Throughout the growing season, Moapa was consistently in the highest group under both photoperiods. Under short days, Ladak was

Table 5. Summary of Duncan's multiple range tests (14) at the .05 level of significance for floweringpercentages , for a four-week period of the initial growth and at weekly intervals after eachcutting of alfalfa.varieties grown under long days.

Growth PeriodsMay - June e June - July - Aug. Aug. - Sept Sept. - Oct,

Variety 9- 10 11 12. , 1 - 2 -■ 3 1 2 : 3 • 1 2 3 4 1 2 3 4 5

Rambler c b bS - '

te8 ab c d

r8

89 / '

Vernal cde ab a . ab r-o\.t .

d e -8 ' 8

ab b a 88

$ a b be b b

Ladak abed ab a ab » ab a • be 8 ab be ab 9 6 a ab be cd cRanger ' abed a : a ab ' C bed be I ab be h f a - a-. c b r-a: ah be be bAtlantic abc ab a ab ' a "8 a ' be 8;

88ab bed c 9

8' 8 a ; b cd cd b

Buffalo ■ de b a. ab 8 'a' ,' ab':: be b bed be 8 - 8 a b be be h yLahontan a ab a ab • be abc be ' 8 ab bed ab V 8 a b d d cChilean 21-5 de b a ab ’■ e,- d be . f

flfab bed be ?

g a a c b 8

Galiverde abed ab a ab ■'-/‘.cV cd b 8 ab cd b 8 a a ab ab 1 a ab b b bMoapa ab ab a ab abc a 9 a a a 1 a a. a a 8 a a a a aHairy Peruvian bed ab a a 8 c?;;

t" .

d b 98ab b a i

'ta ■ a be b 8

8 a" ab b b b

1/ For each week, level.

varieties followed By; the same letter are not significantly different at the .05

Table 6. Summaries of Duncan’s multiple range tests (14) at the .05 level for flowering percentages fora four-week period of the initial growth and .at weekly intervals after each cutting of alfalfavarieties grown under short days.

Variety

Growth PeriodsMay June

Weeks after seeding» 9 10 11 12 i

» June - July. July - Aug. Aug. - Sept.Weeks after cutting

■ 1 3 1 2 3 1 2 3 • 4

Sept. - Oct.

1 2 - 3 4 5

RamblerVernalLadakRangerAtlantic

Buffalo

al/ea cdaa

cda

dbecab

a bed be

a abc

dbedcdababc

ab c cdeab be :e b bc: bede ab be bodeab be de

Lahontan a de be abc t b c bodChilean 21-5 a ab abc a i b c de

Caliverde a a - ab a a b abMoapa a a / ab a . ‘ a a aHairy Peruvian - a bed abc cd -1 ab be be

cc

ccc

de e de e

e ecd de de de

be cd cd be de de be be bbe b b a a a ab be be

ed

b bbbbbb

a b d c 8fl

a a b b ' aa a a a 1 aa ab be ab ' b

bbf-bbb

cc.ebc

b b a ■ a b c

ee

ee

de cbe

cad

bc

bab

1/ For each week, varieties followed by the same letter are not significantly different at the .05level.

39

consistently in the lowest group. In general, the varieties tended to be separated into more groups, with fewer varieties, in the highest group under short days. Nine weeks after seeding, Caliyerde was the only variety that had begun flowering under short days.

Medicago falcata was not included in the analyses of flowering percentages, because when the first data were taken on the other varie­ties, nine weeks after seeding, M. falcata had just begun emerging.Also, M. falcata plants growing under the two photoperiods were not cut within 15 days of each other at. any time during the growing season.

Plants of M. falcata were the most sensitive to photoperiod of all those tested. During the initial growth period, M. falcata began flowering 17 days earlier when grown under long days than short days. Figures 5 and 6 show this difference in flowering.

The earlier flowering of plants that have not been clipped when grown under long days is in agreement with the work of Massengale and Medler (26) on alfalfa, Keller and Peterson (20) on red clover, Knight and Hollowell (21) on crimson clover and Joffe (18) on birdsfoot trefoil. No literature was found to show that any variety of alfalfa flowered earlier under shorter photoperiods at any stage of growth.

The earlier flowering under short days of nonhardy varieties might partially be explained in relation to the locality of origin of these varieties. All of the varieties originated in regions which have natural phbtoperiods comparable to those of Tucson, Arizona. It may be that the interruption of the dark period produced an environment for which the plants were not adapted, and thus retarded reproductive develop­

ment of the plants.

Figure 5

Figure 6

40

Medicago falcata plants grown under long days. Note abundance of flowers. (Photograph taken June 19, 1959)

Medicago falcata plants grown under short days. Note lack of flowers. (Photograph taken June 19, 1959)

41

■ It is possible that southern alfalfa varieties may be inter- " :mediate plants in their, response to phptoperiod. That is, the optimum•. day length for flowering is within maximum and minimum limits. If thisis the case, the flowering of these varieties was favored by short daysduring June and July, because the long natural daylength plus lightinterruption of the dark period was equal to a photoperiod longer thanthe optimum, and the natural daylettgth was within the optimum limits.It is also possible that at low temperatures, nonhardy varieties react .as long-day plants and at high temperatures, they react as intermediate

plants. . ", ■ . 'The hardy varieties may be considered long-day plants. That is,

flowering of these varieties was favored by photoperiods in excess of a minimum length and was npt retarded'by daylengths in excess of a maximum length. Thus, the hardy varieties in this study flowered earlier under

long days throughout the entire flowering period. '

' ;v; ... . i.: / Summer Height, AV ''' /. , V:;;.Summaries of the results of the analyses of variance of the height

of plants for a four-week period of the initial growth and after cuttingfor each growth period are presented in Table 7. The same varieties that were used in the analyses of the flowering percentages were used in the

analyses of height, - : '. ' . ’ : v :In general, the analyses of variance of plant height showed that

different varieties did not respond similarly to length of day. This was Indicated by the significant interactions between photoperiods and varieties. . . .

Summaries of the differences in plant height between daylengths for each variety are presented in Table 8. - The differences were determined.

Table 7. Summaries of the results of the analyses of variance of plant height for a four-week periodof the initial growth and each week After cutting for each growth period.

Growth Periods ' - - - : •" - -- -■ , .■May - June 8 June ~ July July - Sugo Aug - Sept. Sept. - Oct.

RAvrrA nf Weeks' after seeding 8 Weeks after cutting ... - - .

variation : • "9 10 Tl 12 ■I* 1 2 3 1 2 3 . Y 2 3 /I T 2 3 ... 4. 5

Photoperiods ** ** ** NS 8 .** irk k ** * NS N3 NS NS NS ** * NS * NSVarieties ** - ** ** • 8 kk kk k k . kk kk kk kk kk kk kk kk kk kk kk kkInteraction NS ** NS # 8

N S # # k kk kk kk kk kk kk kk ■. kk * kk kk

Rambler ? Vernal Rambler Ranger ; Vernal - - -Vernal 9 Ladak Vernal Chilean 21-5 LadakLadak 8 Ranger Ladak Caliverde RangerRanger 1 Atlantic Ranger Moapa AtlanticAtlantic t Buffalo Atlantic Hairy Peruvian BuffaloBuffalo I Lahontan Buffalo LahontanChilean 21-5 r Caliverde Chilean 21-5 MoapaCaliverde 8 Moapa Caliverde Hairy PeruvianMoapa 8 Hairy Peruvian Moapa CaliverdeHairy Peruvian f Chilean 21-5 Hairy Peruvian

‘ ....Lahbntan......... 8 Lahontan* Significant at the .05 level.** Significant at the .01 level.

1/ The varieties included in the analyses for each growth period are listed under that growth-period.

Table 8. Summaries of the difference in plant height between photdperiods for each variety for a four- week period of the initial growth and each week after cutting for each growth period.

Wdwth PeriodsMay - June _ 8

Weekis after seeding*June - July :, SI)?v-:Sug._ ;

v WeeksAug. - Sept.

after cuttingSept. Oct.

Variety ^ ■ •9 ,-10- 11 12 .* ■

-r.9 .,-L:; 2 3 . - . 1 ., 2 • 3 - 1 2 - ■ 3 ■ 4 1 2 • 3 4 5

Rambler-' f L L L ■ %' ' : S . .Vernal■ V L L L ■ L - i s .S'' S - " ;■s:yNS? ; -'E NS L L '■ X L

Ladak L L X 1 fs S NS NS L L NS L L L L

Ranger L L NS NS f L S. S S S ' s NS NS NS NS S L NS NS LAtlantic L X L L i NS s NS' NS NS , ■s : s NS L L NSBuffalo L L NS NS t S NS NS S S s s S S NS NSLa'hontan L L L NS ] NS NS NS NS L s s NS L L NSChilean 21-5 L L NS L ? t s S S S S . NS NS NS NS

Caliverde L L L Lij S s s s S s L NS NS NS ■ s S NS L NS

Moapa L L NS NS i s s NS . s s NS NS NS NS NS - s S L NS NSHairy Peruvian NS L L L

. ;r NS s S s s s S S S S s s S ' NS NS

1/ L represents significantly greater plant height under long days; S represents significantly greater plant height under short days; NS represents no difference between photoperiods.

by the method of the least significant difference between two treat­ment means at the five per cent level of significance. The height of plants that have not been clipped of all varieties was favored by longi - ' . .

days, but the regrowth of most varieties during the hot summer months was favored by short days. As natural daylengths shortened and tempera­tures decreased during September and October, the plants began to respond more to long days. It is interesting to note that most of the varieties responded more to short days during the earlier weeks of the last growth period, and during the later weeks became more responsive to long days or showed no difference between daylengths. Ladak and Vernal appeared to be influenced more by long days as the natural daylengths began to shorten during July and August. .

This reduction in rate of growth with shortening natural daylengths and lowering temperatures indicated that growth under short days was retarded as the plants were becoming dormant. Plants growing under long

days apparently did not begin to show dormancy until the temperatures were considerably lower. It may be noted that the hardy varieties

responded more,in this respect than nonhardy varieties. This explana­tion agrees with the work of Tysdal (55).

Summaries of the differences in plant height among varieties for long and short photoperiods are presented in Tables 9 and 10, respec­tively. During the initial growth period in May and June, there were

greater differences among varieties grown under short days than among varieties grown under long days. During the regrowth throughout the summer, however, the differences among varieties were similar for thetwo photoperiods. During the September-October growth period, there were again greater differences among varieties grown under short days.

Table 9. Summaries of Duncan1s multiple range tests (14) at the ,05 level for plant height for a four-week period of the initial growth and each week after each cutting of alfalfa varieties grownunder long days» .

Growth PeriodsMay - June June July

Weeks after seeding 1 ' ^Variety ■. 9 ■ 10 11 12$ 1 ■ 2 • 3 , V;b"-

Rambler ' cl/ d b a$t

1i bc

Vernal b c ab a r abc d. f s c

Ladak b be ab a 8 be cd defI? c

Ranger ■ b abc ab a 1 ab d £ 8 abcAtlantic " ab beff'- a ; a 1 be be cd $ abc

Buffalo ab ab ab a ■t8 be ab be ?

i. beLahontan a ab ab a I a . a b J aChilean 21-5 ab a ab -a 8 ab d ef 8 abc

Caliverde b c ab a t8 c cd cd 8

1 dMoapa ab a ab a 1 a ab a 1 aHairy Peruvian ab ab a a I a cd cde ab

July -‘. Aug. , Aug. - Sept. Weeks.after cutting

Sept. - Oct.

2 3 3 4 -5

e • cdcdcd

fabc

abcde

abc cd6: bede abedde

acd

deabab

abcde

eaabc

be d cd cddabbe

ebcd

db;<

dbe

be bedcd bed ab be

bb

aab

bac

aba

be bed be a a a

be b 8. cd . bed b

cdcd

bedaab

babb

bb

baab

1/ For each week, varieties followed by the same letter are not significantly different at the .05level, • . w -

Table 10. Summaries of Duncan’s multiple range tests (14) at the ,05 level for plant height for afour-week period of the initial growth and each week after each cutting of alfalfa varietiesgrown under short days.

Growth Periods

VarietyMay - June

Weeks after seeding - 9 10 11 12

5 Junet ' ' ' "

July1 -8--- 3

July - Aug. Aug. r Sept. . Weeks after cutting

Sept, - Oct.1 2 3 4 3 4 5

Rambler V ernal

Ladak

fl^ ede d

dcdbed

dc be bed cd

be d

cdde

e.fdef

ed

Ranger. cd be abc ab i be d be i cd bed dAtlantic cde c abc b t c cd cd 8 de cde be

Buffalo. be ' ab a ab , t be bed be 1 cd be beLahontan abc abc abc b f ab ab be e bed ab abChilean 21-5 cd a ' ab a 8 be d be t abc a a

Caliverde be be abc ab f be bed be 8 cd bed cdMoapa ab a abc ab * a a a a a bHairy Peruvian a a abc b • 8 be abc b I- ab a a

b be

deebcd

£ede

a b be cd

dbb

ab

dbc

bc

f

£cdedefbee£

8 c c c c tf b b c c 8

8 be c b be bed8 a a b b a a a a aba a a a i be b a a a

1/ For each week, varieties followed by the same letter are not significantly different at the ,05level.

These responses in plant height indicated that the greatest dif­

ferences among varieties occurred when plants were grown under short photoperiods and low temperatureso This is in agreement with the work of Nittlet and Gibbs (29) and Schonhorst jet jal. (44) .

Medicago faleata was not included in any analyses of plant height3 for the same reasons that it was not included in the analyses of flower­

ing percentages*During the initial growth period, M* faleata began to elongate

much earlier under long days than under short days. Figures 7 and 8

show the difference in height of M. faleata at 12 weeks after seeding when grown under long days and short days., Figures 9 and 10 show the difference in height of Rambler at nine weeks after seeding when grown under the two daylengths. The increased height of plants that have not been clipped when grown under long days is in agreement with previous

work on alfalfa (26* 29* 44).No literature was found which showed that regrowth of alfalfa

was increased by short daylengths*..A possible explanation of the increased growth of hardy and non­

hardy alfalfas during the summer is that there may be an interaction

between temperatures and photoperiods* and that at high temperatures

growth is favored by short days.

Nonhardy varieties grew taller and flowered earlier under short

days, while hardy varieties grew taller under short days and flowered earlier under long days. This indicated that the vegetative response to photoperaod and temperature of hardy varieties may have differed from the flowering response. It is possible that these varieties may have

Figure 7. Medicago falcata plants grown under long days. Note elon gation of stems. (Photograph taken June 8, 1959)

Figure 8. Medicago falcata plants grown under short days. Note lack of stem elongation. (Photograph taken June 8, 1959)

49

Figure 9. Rambler alfalfa plants grown under long days. Note height of stems. (Photograph taken May 21, 1959)

Figure 10. Rambler alfalfa plants grown under short days. Note height of stems. (Photograph taken May 21, 1959)

50

been long-day plants, in their flowering response to photoperiod regard­less of temperature- However, in vegetative response, the hardy varieties may have reacted as long-day plants at low temperatures and intermediate plants at high temperatures.

Winter HeightSummaries of the results of the analyses of variance of plant

height at two-week intervals after the last cutting in the fall are pre­sented in Table 11. The first 15 weeks after cutting respresent growth during the winter, and the last two measurements represent growth made after the plants had broken dormancy and begun spring growth. The analysis for the fifteenth"-week after cutting was conducted twice, because’ the measurements taken at this time were considered to be the last measure­

ments of winter growth and the first measurements of spring growth,Medicago falcata was:completely dormant during the winter and was not

measured until it began growth. For the second analysis of the fifteenth week after cutting, M. falcata was given an arbitrary value of three inches, since it had not yet begun growth. Three inches was the approximate cut­

ting’ height. ' / ' 1• The interaction was highly significant for all analyses ofvariance, which indicated that all varietis did not respond similarly

to different photoperiods, ' ■Summaries of the differences between photoperiods for each variety

are presented in Table 12. Differences were determined by the method of. the least significant difference between two means, at the five per cent level of significance. Apparently low temperatures during winter masked the effect of length of day on most varieties. Buffalo, Chilean 21-5 .

Table 11, Summaries of the results of the analyses of variance ofipiant height after the last cutting in the fall (Hovember 17, 1959).

Source variation ' Weeks after fall cutting... X - T 5. 9 . 11 13 15 i is . m "ig—

Daylength N3 NS . NS NS NS NS NS NS ■ i - NS NS NSVarieties ** ** ** **, ** ** ** ** ** ieitInteraction ** ** :**. ** ** ft*

Rambler $ ; K falcata- ' " ,Vernal '•i' s' . RamblerLadak -t VernalRanger ■ i; : ladakAtlantic . 8 . RangerBuffalo 8 AtlanticLahontan $ BuffaloChilean 21-5 ■ s - LahontanCaliverde f Chilean 21-5Moapa 8 CaliverdeHairy Peruvian 8 Moapa5 . Hairy Peruvian

** Significant at the .01 level.

Table 12. Summaries o£ the differences in plant height between photoperiods for each variety afterthe last cutting in the fall (November 17, 1959), „ \

Weeks after fall cuttingVariety 1 3 5 ■- 7 - 9 11 -13 15 « 15 17 v 19

M, falcataNsl^

— i—i NS NS NS

Rambler NS NS .. NS NS NS NS NS i NS NS NSVernal' NS NS NS • NS NS NS NS NS . . i NS ■ NS LLadak NS ' NS NS ' NS . NS • NS NS NS 8 . NS NS LRanger L' NS NS. ' • NS I . NS NS NS NS NS LAtlantic NS : NS NS ; NS L NS NS NS 1 NS NS LBuffalo L L. L L. L L NS NS 1 ' NS NS LLahontan NS NS t NS NS / NS NS NS 1 NS NS LChilean 2.1-5 L L L L L NS NS NS 1 NS NS NSCaliverde ... . ns : S NS ■ NS . NS NS NS NS 1 NS NS NSMoapa NS NS , NS NS NS NS . NS NS NS NS NSHairy Peruvian S ■ ' S :. S S S NS NS NS 1 NS NS S

1/ NS represents no significant difference between photoperiods; L represents significantly greater height under long days; S represents significantly greater height under short days.

and Hairy Feruvian were the most responsive to photoperiod. Hairy Peruvian was taller under short days than long days, while Buffalo and Chilean 21-5 were-taller under long days than short days.

The greater height of Hairy Peruvian under short days during the winter may partially explain why it grows later in the fall and begins growth earlier in the spring than other varieties of alfalfa in southern areas of the United States. This response to short days has not been reported in the literature, but Oakley and Westover (31) realized the importance of daylength on Peruvian alfalfa when they stated, ^Although :

temperature bears an important relation to growth, it is its day-hight relation that causes Peruvian alfalfa to have a longer growing period than the other varieties in the South and to have the sane or even a shorter growing period in the North.^

Under field observations. Vernal,, Ladak, Ranger, Atlantic and

Lahontan definitely appeared to be taller under long days. However, the standard errors for testing differences between photoperiods for each variety were so large that statistical differences could not be detected. Rambler and Moapa did not appear to be affected by photo­period during the winter. : : d ■ :

The large standard errors may be explained in part by the shading

effect of the permanent aluminum curtains which separated long-day and

short-day plots. The curtains were placed in an east-west direction and during the winter the plants on the north side of the curtains were almost continuously fn shade for a distance of about five feet. The ground seldom warmed up during the day And the plants made little growth. Plants on the south side of the curtains, however, grew faster because sunlight

54

was reflected from the curtains and gave added heat to the plants nearest the curtains. These differences caused by shading and heat reflection increased the mean squares for the interactions between replications and treatments and thus increased the standard errors.

No variety showed a significant difference between photoperiods from the eleventh to the nineteenth week following cutting. During the eleventh to the fifteenth week, the tall plants received frost damage that killed the tops of the longest stems. The short plants received little frost damage and continued to increase in height. Thus the dif­ferences between long and short days decreased.

Cool temperatures persisted in the field until the sixteenth week after fall cutting. At this time, the weather immediately turned warm, and all varieties began growing. There appeared to be no difference in the time plants of different varieties began growth in the spring. This

indicated that temperature may have been more important than photoperiod in controlling the time that alfalfa broke winter dormancy. It must be pointed out, however, that the temperature increased at a very rapid rate. If the increase had occurred at a slower rate and over a longer period oftime, it might have resulted in differences in the time that varietiesinitiated spring growth. Slowly rising temperatures might also have caused the same variety under different photoperiods to initiate growth

at different times. — ' .Summaries of the differences among varieties when grown under long

arid short photoperiods are presented in Tables 13 and 14, respectively. Under long days, Chilean 21-5 was consistently in the highest group and Rambler was consistently in the lowest group. Under short days, Hairy

Table 13, Summaries of Duncan’s multiple range tests (14) at the .05 level of significance for plantheight under long days after the last cutting in the fall. (November 17, 1959)

Weeks after fall cuttingVariety . - ' ... 1 3 ■- • 5 7 9 11 13 15 j 15 , 17 19

M. falcata i

-tf f ... £ e :

Rambler : el/ . 8.. £ h ' h .<-v 8 f . f : '; 8'. £ e -. “ dVernal . ' cd /■; ef, ' a v £ e % d ' d 8 d : '■ c " b - yLadak ’ . - de fg e 8 g . £ e a ? ..

8 e d c -Ranger be cde bed de de cd be c 8 c ab - abAtlantic b bed b c be b . b ab 1 - ab ab aBuffalo b ;; b b c be be be be % be ab abLahontan be be b cd cd be be cd cd b b .;Chilean 21-5 ' a a a a a " a a a . r ' a a a .Caliverde be - cd - e£ ef de cd ..cd i - ; cd ; ■ ab abMoapa. a ' : a - 'a b b - b-" be be be ab abHairy Peruvian d ;de be cd cd bed be cd . i ;v cd ab " = ab . ; -

1/ For each week, varieties followed by the same letter are not significantly different at the .05level. .

Table 14. Summaries of Duncan1s multiple range tests (14) at the .05 level of significance for plantheight under short days after the last cutting in the fall (November 17, 1959).

Variety - • - • - - - —• - • " - ' Weeks after.fall cutting. -3 r• - -5 -. , , 7 - - 9 ---11, 13 . 15

....i .■V - 15 17 19 ■ •

M, falcafcai$ 8 ... h h

Rambler ef d h e f e f i. 8 8 8 ; .Vernal bed de c fg " d e d d • $ e e ef

Ladak e £ d gb e - £ e e :ir £ f f

Ranger de def'. e ef. d de cd c i d d dAtlantic be cd c d e c c c i ■ cd cd cdBuffalo cd cd c def cd cde cd c

s1 d d d

Lahontan cd cd c de " c cd c c f d cd deChilean 21-5 ed be b c b b b b 1 b ab ab

Caliverde b b b c b b b b 1 be ■ be beMoapa a a a b a a r b b 1 b ab beHairy Peruvian a a a a a a a a 1 - a a a

1/ For each week, varieties followed by the same letter are not significantly different at the ,05level.

57

Peruvian was consistently' in the tallest group and Rambler was again in the lowest group. Under both photoperiods, the varieties were ranked in about the same order throughout the winter. When the plants began.spring growth, there were few differences among varieties grown under long days, but there were considerable differences among varieties grown under short days. These results indicated that photpperiod did influence the rate

of spring growth. : , ; ■ •The rate of growth during winter and spring was calculated for

each variety under each photoperiod. The regression and correlation coefficients'are presented in Table 15. The test of homogeneity of

regression coefficients was performed on regression coefficients of varieties under each daylength for both growth periods. It was found

that,.the regression coefficients were not homogeneous under either photo­period for winter or spring growth. The regression coefficients were ranked, and adjacent values were compared by the standard error of the

difference between two regression coefficients. For winter growth, the regression coefficient of Rambler was less than fhe next highest, coef­ficient under both long and short days. For spring growth, the coefficient for, M. falcata ,w$s less than the next, highest value under both long and short days; Rambler was no different than other varieties , during the spring growth period. These differences were the only ones detected. The mean regression coefficient for varieties under each photo- period was calculated for winter and- spring;growth. No difference was found between the mean regression coefficients for plants grown under

long and short days during either the winter or the spring growth periods.

Table 15. Regression and correlation coefficients of rate of growth during the winter and during thespring.

Variety

..... Winter Growth Spring GrowthLong day 1: ’ — 7 .. Short day Long day Short day

Reg. • ■ Cor .A/ Reg . ; Cor. - Reg. Cor. Reg. Cor.

M. falcata^/ 3.875 .940 2.650 .892Rambler 0.168 .691 0.130 .466 7.312 .959 6.912 .950Vernal 1.334 .892 0.750 .809 9.462 .972 8.212 .965Ladak 0.960 .883 0,549 . «654 9.400 .989 8,588 . . 945Ranger 1.626 .871 1.121 .736 9.675 .962 8.900 . 920Atlantic 1,937 . 929 1.336 .867 9,538 .972 9.012 .968Buffalo 1.674 17 80 1.080 .838 ‘ 8.862 .891 9,038 .963Lahontan 1.575 .787 1.285 .920 8.625 .920 7.675 .975Chilean 21-5 1.895 .858 1,821 ,922 9,150 .972 9.562 . 967Caliverde 1.580 .959 1.597 .836 9.950 .983 9.250 . 966Moapa 1.440 .805 1.583 .790 9.300 .970 8.650 .957Hairy Peruvian 1.649 ,866 1.890 .840 10.088 .954 9.150 .9741/ Ail correlation coefficients were significanfrat the .ui level. Medicago falcata was dormant during the winter .

Ui00

Results of the tests made on the rate of growth of the varieties indicated that although there were differences among varieties in the analyses of variance at certain times during the winter, the rate of growth over the entire period showed few differences among varieties.

Crown DiametersAn analysis of variance was performed on the mean diameter of

crowns of each sub-plot* Highly significant differences were found

between daylengths, among varieties and for the interaction between day- lengths and varieties.

The difference in crown diameters between photoperiods for each : variety is presented in Table 16. All significant differences between photoperiods were greater under_short days. Differences in crown diam­eters between long and short days were greater for winter-hardy varieties than for nonwinter-hardy varieties.

The differences among varieties under each photoperiod, as deter­mined by DuncanVs multiple range test (14), are presented in Table 17. Under both daylengths, M. falcate and Rambler produced larger crowns than all other varieties. There were greater differences among varieties under short days than long days. It was interesting to note that under shortdays, varieties were ranked almost in the order of their winter-hardiness,

with the hardy varieties having the largest crowns.These data indicated that the crown diameters of plants of most *

alfalfa varieties were significantly influenced by photoperiod.

The results obtained for M. falcata were not considered to be a

true response of crown diameter to photoperiod, Medicagp falcata was

60

Table 16. Mean crow diameters of alfalfa plants of twelve varieties grow under two photoperiods. Measurements taken February .6, 1960.

VarietyMean under long days

Mean under short days

Difference long-short

(inches) (inches) (inches)M. falcata 6.35 6.50 -0.15

Rambler ■ 4.50 6.68 -2.18 **Vernal 3.68 5.25 -1.57 **Ladak 3.80 5.35 -1.55 **Ranger 3.42 4.75 -1.33**Atlantic . 3.80 4.75 -0.95 *

Buffalo 3.60 : 4,42 -0.82 *

Lahontan 3.28 4.42 -1.14**

Chilean 21-5 3.35 / 3.68 -0.33Caliverde 3.55 4.22 -0.67Moapa ■ ■ 3.38 4.25 -0.87 *

Hairy Peruvian 3.12 3.92 -0.80 *

* Significant at ** Significant at

.05 level: LSD 101 level: LSD

= 0.69. =1.05.

61

Table 17. Mean crown diameters of alfalfa plants of twelve varieties grown under two photoperiods, and a summary of Duncan’s multiple range test at the .05 level of significance for varieties within a photoperiod. Measurements taken February

, ' 6, I960:. - ' ■ , , ' •'

Long Day Short DayVariety Mean per sub-plot Variety Mean per sub-plot \

M. falcata(incbs6.35

#Rambler 6.68 a

Rambler 4.50 b M. falcata 6.50 a

Ladak 3.80 c Ladak . 5.35 b 'Atlantic 3.80 c Vernal 5.25 be

Vernal 3.68 cd Ranger 4.75 cd

Buffalo 3.60 ed Atlantic 4.75 cd

Caliverde 3.55 cd # • - Buffalo 4.42 de

Ranger 3.42 cd Lahontan 4.42

Moapa 3.38 cd Moapa • 4.25 de

Chilean 21-•5 . 3.35 ad Caliverde 4.22 def

Lahontan 3.28 cd Hairy Peruvian 3.92 ef : .

Hairy Peruvian 3.12 d Chilean 21-•5 3.68 ' f

If Mean values followed by the same letter are not significantly different at the .05 level,(14}.Standard error for comparing varieties within a photoperibd:

— 0.184.

62

completely dormant as far as top-growth was concerned, but considerable production of rhizomes occurred during the winter» Since the rhizomes had broken the surface of the ground and were included as part of the

crown, there was no difference because of length of day when the measure­ments were made in February* This does not give any information about the effect of photoperiod on the crowns of M* falcata before the pro­

duction of rhizomes which may have masked the differences induced by photoperiod.

'--/y.:''' 'V / Dormancy and^ Growth Habit ' ■].

Visual ratings on dormancy and growth habit of each plant were made in February when crown measurements were taken. Plants were rated as dormant and nondormant. Dormant plants were considered to be those which had no stem elongation, and nondormant plants were those which had

stem elongation. Two classes of dormant plants were observed:. (A) plants that had no visible top growth, and (B) plants that had top growth (pro­

liferation of stems and production of leaves) but no stem elongation. NOndormant plants were given three ratings as to their growth habit:(A) prostrate, plants with- stems growing parallel or nearly so to the ground; (B) semierect, plants that had some stems parallel to the ground and other stems that were erect, or plants that had reclining stems; and

(C) erect, plants that had all the stems growing upright,

% r : The fesults^of \these ratings are, given in Table 18. Under both photoperiods, nonhardy varieties grew more erectly than hardy varieties» ,

Hardy varieties had more dormant plants under short days than under long

days, Nondormant plants of the hardy varieties grew more erectly under

Table 18. Visual ratings of the dormancy and growth habit of alfalfa plants of. twelve varieties ' grown under two photoperiods. Ratings were made February 6, 1960.

: Long Day Short Day .. . , ' Dormanti/ Nondormaatl/ ' Dormahtg Nondormant

Variety . ■ , A . ■ B • A B ' : C ,/ - A B . -, ' A ' B C

M. falcata 1 Rambler

ioo3/29 18 o 0

10062 4 10 , 0

Vernal : 1 : .8 .. 23 54 14 - ; - . 11 24 58 6- 1Ladak - - 11 47 / 21: ■ 4 35 30 ■ - 32 3 0-Ranger 1 i 9 30 59 5 ■■ 17 > 52 21 5Atlantic 0 0 4 28 68. 0 11 42 40 7Buffalo 0 0 3 34 63 2 12 24 45 17Lahontan . 1 2 1 26 70 t 1 10 44 39 6Chilean 21-5 ' ' 0 0 0 ' 2 98 : ; 0 ,, 0 : V " . 5i r : 93Caliverde o 1 0 12 87 0 1 I 42 56Moapa ' 0 0 . 0 0 100 0 0 0 :: 5 95Hairy Peruvian -v 2 0 . 0 0 98 0 0 \ 0 2 98

Jl/ Dormant = No stem elongation (A = No visible top growth: B = Top growth but no stem elongation.)2/ Nondormant = Stem elohgation.XA = Trostratei -B — Semierect; G = Erect.) ._S/ ; Per cent of plants receiving ;each rating.:

64

long days than under short days» Caliverde was the only nonhardy variety that showed a response in growth habit to photoperiod.

It appeared from these observations that the dormancy of M, falcata was determined primarily by low temperatures. The dormancy and growth habit of most winter-hardy alfalfas were determined by both low temperatures and length of day. The growth habit of nonwinter-hardy alfalfas was not greatly affected by either low temperatures or photo- periods.

SUMMARY

The seasonal development:of 12 alfalfa varieties was studied under two photoperiods in a field test at Tucson, Arizona from March 18, 1959 through April 1, 1960. The long-day treatment consisted of the natural daylength plus an interruption of the middle of the dark period with approximately 30 minutes of light from eight Number 2, reflector base, photoflood lamps. Natural daylength constituted the short-day treatment.. The varieties that were used were chosen to represent a wide range of winter-hardiness. They were as follows: Medicago falcata, ■Rambler, Vernal, Ladak, Ranger, Atlantic, Buffalo, Lahontan, Chilean21-5, Caliverde, Moapa and Hairy Peruvian.

The response of alfalfa plants to photoperiod and seasonal tem­peratures was determined by the tqtal; yield of dry matter of top growth, per cent of plants in flower and plant height at weekly intervals after seeding and after each cutting, plant height at two-week intervals after .the last cutting in the fall (November 17, 1959), diameter of crowns,dormancy and growth habit during the winter.

The results may be summarized as follows:(1) The total yield of dry matter of Buffalo, Lahontan, Chilean

21-5, Moapa and Hairy Peruvian was significantly greater under short days(2) Plants of all varieties flowered earlier during the initial

growth under long days, but the regrowth of the nonwinter-hardy varieties flowered earlier under short days when the temperatures were high. The

65

66

* regrowth of the hardy varieties flowered earlier throughout the grow­ing season under long days.

(3) During the initial growth period, all varieties grew taller under long days; however, the regrowth of all varieties except Atlantic, Buffa3,p and Lahontan was taller under short days during June and July when temperatures were high. Near the end of the September-October growth period, all varieties were taller under long days or showed no difference, between daylengths. , • ''

(4) It was apparent from field observations that length of day affected the height of most varieties of alfalfa throughout the winter months. However, the standard errors for comparing the differences between daylengths for each variety #ere so large that a significant dif­ference in height between daylengths was obtained only for Buffalo, Chilean 21-5 and Hairy Peruvian., Buffalo and Chilean 21-5 were taller under long days than under short days, while Hairy Peruvian was taller under the shorter photpperiod. , ;

(5) When a comparison of all varieties was made, Chilean 21-5 was consistently the tallest variety throughout the winter under long days; whereas, Hairy Peruvian was consistently the tallest variety under

short days. . .(6). Crown diameters of all varieties except M. falcata, Chilean

21-5 and Galiverde were significantly greater under short days than under long days. Medicago falcata and Rambler had the widest crowns under both daylengths, and the nonhardy varieties (Chilean 21-5, Moapa and Hairy Peruvian) had the narrowest crowns under both daylengths.

(7) During the winter season, the.hardy varieties, except M. falcate and Rambler, grew more erectly under the long-day treatment than under short days. The growth habit of nonhardy varieties was affected very little if at all by length of day. Medicago falcata had no visible top growth under either daylength. Rambler, Vernal and Ladafc had more plants with no visible top growth under the short photoperiod than under the long photoperiod.

(8) This experiment indicated that the method of light inter­ruption of the dark period was an effective method of studying the photoperiodic responses of alfalfa.

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70

27. Moshkov, B. S. Photoperiodism and frost resistance of perennialplants. Bui. Appl. Bot. Genet, and Plant Breed. Ser. 3, 6:Russ. 235-261. English Summary 17-19, 1935. (Abs. in

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30. Oakley, R. A. and #estover,; H . L. Commercial varieties of alfalfa. - . ' ' I 'U.S,B.:A. Farmers* Bui,. 757 . 1920. ■ - V I . : : -31. Oakley, R. A. and Westover, H. L. Effect of the length of day on.

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34. Parker, M. 11. and Borthwick, H. A. Effect of variation in tempera­ture during photpperiodic induction upon initiation of flower

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36. Parker, M. W,, Hendricks, S. B and Borthwick, H. A. Action spectrum• for the;photoperiodic control of floral initiation of the

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Action spectrum for the photoperiodic control of floral ini­tiation in iBLloxi soybean. Science 102:152-155. 1945.

38. Peterson, M. I. and Loomis, ¥. E. Effects of photoperiod and tem­perature on growth and flowering of Kentucky bluegrass. •

1 Plant Physiol. 24:31-43, 1949. " " ■ : " : 1 4,' .

71

39. Pietersj A. J. Difference in internode lengths between, and effectof variations in light duration, upon, seedlings of annual . and biennial white sweet clover. Jour. Agr. Res. 31:585-596.

' ; 1925. . ; i .40. Ramaley, Erancis. Influence of supplemental light on bloomingi Bot.

: v Gaz. 96:165-174. 1934. : ;41. Riddell, J. A., Cries, G.A. and Stearns, F. W. Development of spring

wheat: • I. The effect of photoperiod. Agronv Jour.. 50:735-. ■ 738. - _ 1958. ; .. .

42. Roberts, R. H. and Struckmeyer, B. Ester.: The effects of tempera­ture. and other environmental factors upon the.photoperiodic responses of some of the higher plants. Jour. Agr. Res. 56:633-677. 1938. ' ■ ;

43. Roberts, R.H., and Struckmeyer, B. Ester. Further studies of theeffects of temperature and other environmental factors upon 1 the photoperiodic responses of plants, jour. Agr. Res. 59:

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varieties to temperatures and daylengths. Agron. Jour. 49: ; 142-143. 1957. '

45. . Seth, J. and Dexter, S, T. Root anatomy and growth, habit of somealfalfa varieties in relation to wilt resistance and winter-

■ hardiness. Agron, Jour. 50:141-144. 1958. .46. Smith, D. Influence of area of seed production on the performance.

Of Ranger, alfalfa. Agron. Jour. 47:201-205. 1955.

47. Smith, D. Performance of Narragansett.and Vernal alfalfa from seedproduced at. diverse latitudes. Agron. Jour. 50:226-229.

' : . A : V ./ • /48. Smith, D. and Graber, L. F . Performance, of regional strains of

Ranger alfalfa, Wisconsin Agr. Exp. Sta. Res, Bui. 171.' ■ 1950. ■ • ■ ./ . . ' ' . • ,49. Smith, 0. F. Lahontan alfalfa. Kfevada Agr. Exp. Sta. Circ. 14.

.■ 1958 - :: ' ■ \ v - ;50. Smith, T. J. Responses of biennial sweet clover to moisture, tem-

■ perature, and length of day. Jour.. Amef. Soc. Agron.. .34:865-876. 1942.: ■ . : -

51. Stanford, E. H. Moapa alfalfa. Report of committee for release ofnew varieties. Alfalfa Impr.. Conf. Rpt. 16:109-110. 1958.

72

52. Stanford,- E. H., Houston, B. K. and Osterli, V. P. Galiverde, anew alfalfa.' California-Agr. Ext. Ser. Leaflet. 1952.

53. Steinberg, R. A. and Garner, ¥. ¥. Response of certain plants tolength of day and temperature under controlled conditions.Jour. Agr. Res. 52:943-960. 1936. ■

54. Swanson, Gv R. and Adams, M. W, Metabolic changes induced in alfalfaduring cold hardening and freezing. Agron. Jour.'51:397-400.

■ 1 9 5 9. v /. y ' v . -

55. Tysdal, H. M. Influence of light, temperature, and soil moisture onthe hardening process in alfalfa. Jour. Agr. Res, 46:483-515.

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Effect of photoperiod and date of planting. Agron. Jour. . 49:215-217. 1957. ' - ; ■ ' '1'

APPENDIX

73.

Table A. Mean percentages of plants in flower during the May-June growth period of alfalfa varietiesgrown under two photoperiods.

. •. ■ ■ ' Weeks arter seeding■' f 10 . r. y -' :.II ..- i “'.. ii..

Variety : ' Long Short i'-. Long . Short Vt- Long Short, i TXong'' Short■ . f ' t . . j . . ' ■ » '______

Rambler J . 0 6 V 13 0 j 49 .13 .) 80 40Vernal , 8 0 , 58 5 , 76 38 , 91 58

Ladak ] 18 0 , 60 4 * 73 31 | 89 52Ranger .■ , 18 0 ,. 73 13 , 86 56 • 93 74Atlantic , 16 0 f . 65 6 ( 78 38 f 89 69Buffalo ■ 5 0 ' 55 11 { 76 59 j 85 84Lahontaii , 30 0 , 60 ' 3 , 74 39 , 84 66Chilean 21-5 ' , 5 0 . ' 55 ; 14 f . / 73 50 , 90 80

Caliverde , 18 3 , 65 18 , 85 54 , 95 80Moapa , 25 0 , 65 18 f 85 51 , 9 1 79Hairy Peruvian ? 13 0 f 60 6 f 84 40 ? 94 52

t

Table B., Mean percentages of plants in flower during the June^-July growth period of alfalfa varietiesgrown under two photoperiods. / : ■ .

Variety.. ... . .

I ' Weeks after cutting.1 'L .... , - V .- •• - - • ; • ^. .. . - , - - v- .- - 1 , ...... f ': • 1 Long;, // r/ . Short_ 8 .

ihong . .... Short r" 1 - -

;V . Long . . Short .

Vernal6s 0 ■

8s 29 29

. $ ' 1 . 1 :z7 ' 84

Ladek i' s■■ ; :r; 6 ■; 2

8$ 61 : 39 $

$ 88 . 77

Ranger o '. : i 8 : 36 36 I 87 90Atlantic - ■ 8

? 8 : : . : 2 ; .

. . t * 59 36 ; .1 " . > - - 91 88

Buffalo . ' - • f 6 ":/■■■ 3' ... $ ; 53 . ; 36 ■ 8::. 92 ■ 83Lahontan ■ I'- ' 1 i ; $

i - 47 : 32 I • S' 91 89

Chilean 21-5 /8 . 0 ■. ■' 1 , t;. , 20 27 8 83 83Caliverde . \ ' s' .

■ i. 0 ; v 4 • ■■ ? .

. 8 31 52 y 8I 91. 96

Moapa. v. * \ : 6 : .. . . t '■ :. 48 - : 83 .1 99 100Hairy Peruvian - ' ■ s 0 : 4; ' 8

T ' ‘ 25 38 f • '' I ' 89 95 - .

Table 6. Mean percentages of plants in flower during the July-August growth period of alfalfa varietiesgrown under two photoperiods.

i , , , ... ; - , .. - " ' Weeks after cutting ' "* i •,. . . . . . , - ^ . yyg- - ; - \ . ; y 1 -' ' - ' : 3

Variety - .. , y , Long - ; \ r Short y - Long - ' Shor t * ^ — ---;-----— —--— *— --------- • Long Short

Rambler ; i 1 0 1 8 5 t • 23 32Vernal r’

8 3 0 ’ i .36 2 ■ i i 94 ' 36

Ladak 8 3 0 ' 24 1 t 85 31Ranger t 1 ■ : o 24 14 i 80 50Atlantic _ • 8 •

• 1 1 0 e" ■ i 17 ... ■ 3 ii 55 .. 47

Buffalo - : $ o : .Vr:; ; 1 ' 19 : : 10 » 72 64Lahontan ■ r ■ 1 ; .r 1 ' 19 2 i 89 44Chilean 21-5 , 8

" $ ' 1 4 'i 16 20 . « , r - 74 89

Caliverde : 1 3 - 13 34 i 79 88Moapa f ■ 4 10 ' 65 67 » ' 95 100Hairy Peruvian t -2 \ 5 ■ ' 33 21 - i 93 • 76

Table B. Mean percentages of plants in flower during the August^September growth period of alfalfavarieties grown under two photoperiods.

Variety ,

s • • • - Weeks after cuttingr i " : ' 2 ; 4 ' ' ■"f’ \ t hong V Short • X1

1 Long . Short 8 Long , h Short S Long .5. Short- i' I- 8 •8

Ranger • r 0 0 ? 5 2 8, 25 • ■ .74- ? 56 / \ 36' i 8 $ - -8-Chilean 21-5 8 0 1 I ' 4 1 8 24 3 Vh 59 . 19f 8 8 ■. • .Caliverde 1 0 1 1 17 10 f 63 41 t 85 668 1 - 1 iMoapa 8 ; - 3 1 ■ 8 2% 26 8 64 83 ;■ $ 95 96

i ' ‘ $ - t“Hairy Peruvian i 1 1 .9 7 v' 5 9 34 27 f 66 79' T 8; f - 8

77

Table S.. Mean percentages of plants in flower during the September-October growth period of alfalfavarieties grown under two photoperiods,

Variety

. a ? •. - - - . r . : Weeks after cutting . ' ' " - ■ • ■ ■

$ 1 / v $ 2 i 3 • !•• 4 ' '' I - '3 ' "

i Long $ - Short 51 Long- ' Short i Long Short V Long Short r Long ' Shorti I i i a.

Vernal -■ ' V 0 0 ' j 0 1 0 i 8 • 0 : i : 48 "■ : '■ -3 ...■ f 68 13.

Ladak ■ 1 0 o :■ 1 1 i • 6 " 1 .» ' 20 1 8 30 7Ranger t 0 • o a ‘ 1 0 ' i 5 0 i 34 2 8 . 7 5 : . 3

1 . r i t ■$'Atlantic ' i - 0 0 - i -

. 0 0 t 3 - . 0 1 21 5 I 60 : 14Buffalo f 0 0 8 o 2 r 6 16 f 36 68 5. 76 78liahontan 1 0 : ' 0 6 ■ o 0 t 0 0 t ' 8 o 1 34 V:.h ,;;ii:'e ■ i t i ?Calivefde i 0 ' - 4 . a 1 r 4 i 20 14 l 49 40 1 75 . 67Moapa - i 0 3 T 6 / 25 i 42 56 t 82 87 f 97 98Hairy Peruvian ! 1 0 r 2 0 : j • 19 2 48 17 f 74 66

t ? f ?' 1

78.

Table F. . Mean plant height during the May-June growth period of alfalfa varieties grown under two ' photoperiods, , } - • -

? * - ■ Weeks after seedingV " fi 9 1 10 1 ' 11 t 12 : ' '

Variety . 1, Long Short ( :Long Short * Long Short i- Long Short

Rambler ■ i. - 8 8 .2 1/ 4.0

■ f-:'. 1 17.4 11.2 , 19.9 16,4

1i : 24.0 . 13.7

Vernal ' 9 11.0 7.2 1 19.7 15,6 , 2 2 . 3 18.7 8 24.4 21.8

Ladak$1 11.0 6.2

ft 20.3 15,2 6 ’ .

, 22.3 19.311 25.0 21.8

Ranger 1 11.9 8.5 : ' I - 21.2 18,0 , 21,1 20.1 't ‘ 25.0 25.8Atlantic V $' 12.3 8.2 - t.;: 20,3 17.4 , 23,4 20.6 8 26.3 V 24, 8

Buffalo\ $; ' 8 12.4 9.6

1 : I 21,8 19,6 ] 23.1 23.0

f- - 1 26.4 26.4

Lahontan 1 14.3 10.4 ' » 21.8 18.6 , 21.8 20.0 f 24.2 24.4Chilean 21-5 : t 12.6 8.6 I 22.3 20.3. , 23.2 22.2 f 26.4 27.7

Caliverde8■ t . 11.9 . 9.9 1

! 19.6 ■ 18,1$ • ' ’ , 23.1 21.7

?:t 26.4 25.0

M o d p a - :,, ' 6 r 12,7 11.3 1 2 2 . 1 20.1 ■ • 9 22,2 " 21.6 5 25.8 26.4Hairy-Peruvian v / 8

313,1 12.5 A.

121,9 20.0 .$ 24.0

9 '' . -21.5 s

$26.1 24.4

1/ Inches,

<4\o

Table G. Mean plant height during the June-July growth period of alfalfa varieties grown under twophotoperiods. . .

i - ■ • • ' - - - -■ - - Weeks after cutting1 • " ' ■ 1 .... 2 t 3Variety ■: 1 Long 1 Short ■ 1 1 Long 6 ■ Short » , Long Short

VernalLadak

8

e

s.'svil/4.4

6:0■ ^

1■ 1 ■

-11.1 12.4

15.313.9

i'

t, 1 11

18.620.4

21.820.2

RangerAtlantic

8

8

rt ' - 8

8

f

- 5.5 4.7

5.04.8

1t

10.9 . 14.1

14.415.0

18.821.6.

22.821.8

Buffalo " ; Lahontan

4.8 ; 6.5

" ,5.7 . 6.3 .

I . 1

14.916.7

' 15.3 17,0

'.I.- : 1 1

22.624,2

• 22.6 23.7 \

Chilean 21-5 Caliverde

5.63.9

4.95.4

111

11.312.5 : W - '15.6

ilI

19.621.8

23.123.5

Moapa;Hairy Peruvian

ff. i ; ‘ $

' 6.5 6.2

I-* - 1

15.012.5

18.416.7

I«l

27.320.8

26.624,6

_!/ Inches.

Table H. Mean plant height during the July-August growth period of alfalfa varieties grown under twophotoperiods. -

-- T — --— .—" '' ? '. - 1. • - - - ■ Weeks after cutting, f ...... . • i -..- ; i. xTv " 2 " '' « r "v : 3' \

Variety •• ’ • - * Long '.....------------ Short »\ Long ' ‘ Short »’■ Long •. ■ ----- -----—--......-; -------- T,----- - Short

Rambler 1 5.21/ 6.3 i 11.8 13.2 i 17.2 19.6Vernal 8 5.1 : 5.6 t

i • 14.4 14.0 ;i 23.3 21.6

Ladak 8 :t f *0 ' / ' 4.8 i 14.4 12.6 s .23.4.; 19.2Ranger • 8 . 5.5 6.1 t 13.8 15.6 * .., 21.3 22.3Atlantic ' 5.6$ 5.6 ' i

t14.2 15.0 5

« 22.4 . 24.0Buffalo 6 5.2 6.3 t 13.2 16.2 1 22.8 24.2Lahontan ' 6.5 6.6 s 18.2 17.0 • 1 24.0 25.4Chilean.21-5 1 5.6 « 6.8 s •'

1 14.8 18.2 I■’ I

21.9 26.8

Caliverde . 1 3.9 6.1 i 13.0 15.6 1 ' 20.9 23.1Moapa - * 6.5 7.7 1 15.5 18.3 1 24.1 24.7Hairy Peruvian ' 6.2 7.3 » 16.9 18.4 1 23.5 26.4

. ,f. » • ■ _ 1

1/ Inches

Table X* Mean plant height during the August*-September growth period of alfalfa varieties grown undertwo photoperiods.

t; - . v . ; ' y ' ' '• ■ ■ ■ ■' - ' -' I t cutting

t..." 2 " ..... . 3 ■-MVariety / ■ Long Short V Lon g Short ,■ Long Short l Long Short

Rangers$. : 3 , 0 3.8

i :i 11.3

; 1 12.2 t 17.7 -20.1

:t 23.9 25.6

Chilean 21-5 - 5 ' 3 . 7 ' :- 3.2 « 12.4 ? :10.8 8 18.4 18.5 ■r 25.6 24;3

Caliverde 1 4.2 T:i5.3f v* 18.2$ . ■ .

14.1 » 22.4 20.1 * 27.0 25.5' :Moapa - 1

. i' ri'

_- 5.9 : 5.5 17;2 i\ Vs

25,0 24.4 * < 31.5 29.4

Hairy Peruvian 378 ; 5.8 « 12i0■ i ' ■ :

18.1 > 19.4 27.9 iY

25.0 32.6

1/ Inches.

Table J. Mean, plant height during the Sepfcember-October growth period of alfalfa varieties grownunder two photoperiods, ■ -

' , . Weeks after cutting • . ; . '. . ' 1 ' - ' % ' % : ' / / ' ' ' ';3' '' " ' '' 4 " " '■■ ■5 '

Variety ,. Long Short f Long -Short r Long Short / Long Short f Long *• Short8 : , r ' ' - 1 ; ; . - s. 1

Vernal ; : 5.1 . 4.8 ' 10.8 10.2 i 16.4 14.4 i 22.9 16.8 ■ 27.9 22,0Ladak ■ ;• 3.8 4.1 1 8.3 7.2 « 15.5 11.9 i 21.1 15.7 .1 27.1 21.4Ranger . 5.4 -: \f-.. ■ ■ ; : 6.4 '12.5 40.9 ■. i

: l 18.4 17.5 i- i 24.3 23.4 ' 28.8i . . . . 24.9

Atlantic •' • 4.8. 5.4 ' 11.1 11.0 ! 18.0 ' 16.7 i 23.1 . 20.0 ’ 27.4 . 23.7Buffalo .4.4 - 7.6 ' 11.4 15.6 f 18.4 19.4 ? 22.4 23.0 ' 28.2 , 26.5Lahontan V ■ M " : ' 6.0 ' 12,2 12. Z i

l 18.5 - 16.4 $ 22,4 19.4 1 27.0i 23.3

Galiverde * 4.9 - 5.9 : ' 11.6 12.3 ! 17.8 17.2 '» 23.2 21.1 ' 27 . 3 26.3Moapa ‘ 6.1 7.6 ' 15.6 16.9 1 23.0 21,2 t 26.8 26.0 1 31.0 28.4Hairy Peruvian 4.3 6,2 ’,' 11.4 14.5 1 19.3 20.3. . i 25.5 25.9 ' 29.5 30.31 ^ — — * . ' ' " - .. . --------- r - r v » ' - :— - - r

. ■ • ■ . - - , - ■ . • ^ - ; * - " g - | • • f "

1/ Inches.

Table K, Mean plant height during the winter and spring recorded at two-week intervals after cutting• on November 17, 1959V of alfaXfa varieties grown under two photoperiods.

Weeks after cutting1— 1 3 7 9Variety ' " • $ Long Short’ •Long Short i Long Short Long .Short t Long Short

Rambler1

; ■ - $ : 2.61/ 2.7 1 3.0 3.7 2.8 '3*1■ii 3.0 3.4

88 3.0 3,3

Vernal • 8 ' 1 3,4 3.5 11 5,1 4.7 i

' i 6.8 5/2 tt

8.4 5.4 88 9.1 6.0

Ladak f . 2.9 2.6 * 4.2 ' 3.2 •r 5,0 3.2 t 6.0 4.2 i 6.3 3.8Ranger 3.7 3.1 ' 6.2 4.4 s' 8,5 5.1 i 10.6 6.4 $ 11.4 6.3Atlantic ' ■ $

3 ; 4.0 3.8 *' ■ V 6.8 , '5.4 if 9.5 6.8 f

i12.6 8.4 1

8. 13.6 8.8Buffalo ' ■ . t . 4.0 3.4 * 7,6 - .5,1; i 10,3 5.9: § 12.9 6.9 r 13,8 7,1Lahontan V.. 3*8 3.4 ! 7.4 • 5,7 9,9 : 6.2 i 12,1 8.2 13.0 8.3Chilean 21-5 ? . 4.9 ■ 3.3■ ,i 9.8 6.2 i-

i 14.1 9.0 3r 17.4 11.8 8

1 17.6 ; 12.5Caliverde 1 ' 3.6 4,0 1 5,2 7.2 ■ i 7,4 9,8 I 9.5 12.1 f 10.2 12.8Moapa 1’ 4,6 4.7 1 9,0 9.7 .I- 12.5 13.2 -f 14,7 15.0 S 15.2 16.1Hairy Peruvian X 3.4 5.2 1 5.7 10.4 i 8.7 14,5 t 11,6 17.4 i 12.6 17,8• ? i i 81/ Inches.

Table K (con.i'd).

Variety

i - ■ " -.... Weeks after "cutting ... ;11 .'' : is. ".... ' 15 ■ 17 19

$• ; Bong Short , Long Short t Long Short i Long Short 8 Long' - Short .

M..fa'cata• i?

i •r

ie

«i 4.7 3.9

810,8 8.3

Rambler ? 3,0^ 3.6 $ 3.7 3.8 t 4.0 - 4.0 i 9.7 9.4 $ 18.6 17.8Vernal r

t'10,4 7.0 811.9 .1

8.0 ii.12.9 9.3 ; i 21,3 17.4 I

f 31.8 25,7

Ladak t 7.9 4.8 > 9,0 . ::..5,3 t 9,7 ■ 7.1 i 18.1 14.7\ --- * / 8 28.5 24.2

Ranger i 13.2 8.0 •14.3 • 9.6 ■ « 15.2 11.6 1, 24.9 21.2 . r.34.6 29.4,Atlantic * 15,5 10.4 816.6‘ ? 11.8 i

t 17.5 13.6 lj 26.0 22.5 •i

%36.6 31.6

Buffalo s 15,2 8.5 •15.8 10.1 i 16.0 11.6 1 25.1 21.1 9 33.7 29.7Lahontan .? 15,0 9.9 •15.5 11.4 i 14.6 13.1 1 24.0 22.1 9 31.8 28.5.Chilean 21-5 • - i 19.0 13.8 •19.6 15.6 s. 18.6 - 16.3 »; 27.2 26.1 ; 9 36,8 ; 35.4

Caliverde 8 11.8 14.0 ‘13.5 15.0 i 14.6 15,6 1 24.8 24.5 8 34.5 34.1Moapa t 15.6 16.8 815i6 17.1 i 15.8 16,7 i 26.6 26,5 f 34,4 34.0Hairy Peruvian $ 13.4 18,7 •14.6 19.5 t 14.6 19,5 t 25.8 28.5 ,.;s_ 34,8 37.8

1 i I1/■ Inches,