71 12,726 COLE, Darrell Franklin, 1941- CHEMICAL EFFECTS ON WATER-USE EFFICIENCY OF

71 12,726 COLE, Darrell Franklin, 1941- CHEMICAL EFFECTS ON WATER-USE EFFICIENCY OF

71

T

12,726

COLE, Darrell Franklin, 1941-

CHEMICAL EFFECTS ON WATER-USE EFFICIENCY OF

ALFALFA (MEDICAGO SATIVA L.).

University of Arizona, Ph.D., 1971

Agronomy

University Microfilms, A XEROX Company, Ann Arbor, Michigan

THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED

CHEMICAL EFFECTS' ON WATER-USE EFFICIENCY OF by

Darrell Franklin Cole

A Dissertation Submitted to the Faculty of the

DEPARTMENT OF AGRONOMY

In Partial Fulfillment of the Requirements

For the Degree of

DOCTOR OF PHILOSOPHY

In the Graduate College

THE UNIVERSITY OF ARIZONA

THE UNIVERSITY OF ARIZONA

GRADUATE COLLEGE

I hereby recommend that this dissertation prepared under my direction by Parrel 1 Franklin Cole entitled Chemical Effects on Water-use Efficiency of Alfalfa be accepted as fulfilling the dissertation requirement of the degree of Doctor of Philosophy

^ J

Dissertation Director £T~

< * / / £ / 7 #

Date '

After inspection of the final copy of the dissertation, the following members of the Final Examination Committee concur in its approval and recommend its acceptance:*

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This approval and acceptance is contingent on the candidate's adequate performance and defense of this dissertation at the final oral examination. The inclusion of this sheet bound into the library copy of the dissertation is evidence of satisfactory performance at the final examination.

STATEMENT BY AUTHOR

This dissertation has been submitted in partial fulfillment of requirements for an advanced degree at The

University of Arizona and is deposited in the University

Library to be made available to borrowers under rules of the Library.

Brief quotations from this dissertation 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 Dean of the Graduate

College when in his 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:

ACKNOWLEDGMENTS

The author is deeply indebted to Dr. Albert K.

Dobrenz for his constructive advice, suggestions, and his untiring assistance throughout the course of graduate study.

Acknowledgnient is given to the graduate committee,

Dr. Martin A. Massengale, Dr. L. Nea.1 Wright, Dir. Waltei"

S. Phillips, and Dr. Robert S. Mellor, for their guidance and assistance in preparation of this dissertation.

The author also wants to thank Dr. L. Neal Wright and Dr. Gerald 1-1. Luper for providing greenhouse and growth chamber facilities.

Acknowledgment is given to the Department of

Agronomy for providing monetary funds to assist the author in his graduate program.

The author expresses his gi-atitude to his wife and children for their encouragement and patience during the graduate program.

iii

TADLE OF CONTENTS

LIST OF ILLUSTRATIONS

LIST OF TABLES

ABSTRACT

INTRODUCTION

REVIEW OF LITERATURE

Water Requirement of Alfalfa

Effect of Chemicals on Water-Use

Efficiency

Transpiration Rates of Alfalfa

Effect of Chemicals on Transpiration

Photosynthetic Rates of Alfalfa

Effect of Chemicals on Photosynthesis and Respiration ........

Effect of Chemicals on Alfalfa

MATERIALS AND METHODS

Lath and Greenhouse Experiments

Growth Chamber Experiments

Transpiration

Photosynthesis and Respiration

Field Experiment

RESULTS AND DISCUSSION

Lathhouse and Greenhouse Experiments

Growth Chamber Experiments

Effect of GA on Transpii-ation

Effect of GA on Photosynthesis and Respiration

Field Experiments

SUMMARY

REFERENCES

iv

Page v viii xi

1

3

3

4

5

6

8

9

11

12

13 l6

17

20

20

25

25

34

44

49

62

83

86

LIST OF ILLUSTRATIONS

Figure

1. Plexiglass chamber used to measure the photosynthetic rates of entire alfalfa plants. Note the air intake near the base and exit near the top. The temperature probe is shown in the middle of the chamber

2. Plexiglass chamber used to measure photosynthetic and respiration rates of plants grown in the field

3> Effect of GA on length of individual internodes of alfa.l.fa grown in a controlled environment. Internodes arc numbered consecutively from cutoff level (one) to stem tip (ten)

4. Effect of GA 011 height of alfalfa stems grown in a controlled environment

5- Effect of GA on the rate of stem elongation in alfalfa grown in a controlled environment

6. Transpiration rates for two clones of

Mesa-Sirsa alfalfa grown .in a controlled environment

7. Effect of GA on the transpiration rates of Mesa-Sirsa alfalfa grown in a contro1Ied environment

8. Effect of GA on the transpiration rates f M s S r a a grown in a controlled environment

9. Effect of GA 011 the percentage moisture and total forage of Mesa-Sirsa alfalfa

10. Effect of GA 011 the stem-petiole and leaflet, weights of Mesa-Sirsa alfalfa grown in a controlled environment

v

Page

19

23

40

4l

42

45

47

48

52

53

vi

LIST OF ILLUSTRATIONS--Continued

Figure Page

11. Effect of GA on transpired water and water requirement of Mesa-Sirsa alfalfa grown in a controlled environment

12. Effect of GA on leaflet to stem-petiole ratio and specific leaf weight of

Mesa-Sirsa alfalfa grown in a controlled environment

13• Effect of GA on respiration rates of

Mesa-Sirsa alfalfa grown in a controlled environment. Left) ing CO^

d m

~2 hr-1. Right) nig ^2

55 l4. Effect of GA on pliotosyntlietic rates of

Mesa-Sirsa alfalfa grown in a controlled environment. Left) mg CO2 dm~2 hr-1.

Right) mg COg g

-

-*- hr-1 57

15* Effect of GA on the yield of Mesa-Sirsa alfalfa grown under field conditions.

Data taken from an area of .19 rn^

6 3

l6. Effect of GA on stem length and secondary branching. l) Control. 2) Treated .... 66

17* Effect of GA on alfalfa leaf anatomy. Note the increased width find the arrangement of palisade and spongy mesophyll cells

(1250 X). Upper) Treated. Lower)

Control-

18. Effect of GA on raceme and sepal elonga­ tion. l) Control. 2) Treated

19. Effect of GA on photosynthesis

(mg CO2 dm~2 hr-1) of alfalfa grown under field conditions

20. Effect of GA on respiration

(mg CO2 dm

_

2 hr-1) of alfalfa grown under field conditions

21. Effect of GA on specific leaf weight

(SLW) of alfalfa grown under field conditions

6 9

71

72

73

7'j

vii

LIST OF ILLUSTRATIONS--Continued

Figure

22. Chlorosis and increased height of

Mesa-Sirsa alfalfa following GA application under field conditions

23. Effect of GA on per cent trarismittance of a chlorophyll extract of Mesa-

Sirsa alfalfa

2'i. Photograph showing the separation of free sugars by thin layer chroiiuitography.

Standards were prepared at a concentra­ with 10 and 25 |i.l , Mj_ and M2, respec­ tively. Sucrose (S) and fructose (F) were spotted with 25 jJ,l and the unknown was spotted with 5, 10, 25, and 50 jxl ,

Page

76

79

8l

LIST OF TABLES

Table

1. Chemicals, rates, and methods of application used on seeded plants greenhouse environment

2. Chemicals and rates used on seeded plants of Mesa-Sirsa alfalfa in a lathhouse environment

3- Effect of various chemicals on water-use efficiency of Mesa-Sirsa alfalfa grown in a greenhouse environment k. Effect of various chemicals on stempetiole and leaflet weight of Mesa-

Sirsa alfalfa grown in a greenhouse environment

5. Effect of various chemicals on total forage per plant and leaflet to stenipetiole ratio of Mesa-Sirsa alfalfa grown in a greenhouse environment

6. Means of water-use efficiency, total forage, and stem-petiole tissue as affected by various chemicals applied to Mesa-Sirsa alfalfa grown in a lathhouse environment at the Tucson

Plant Materials Center

7. Means of leaflet to stem-petiole ratios, affected by various chemicals applied lathhouse environment at the Tucson

Plant Materials Center

8. Effect of GA on water requirement values of alfalfa based on yield components and total forage for five harvests in a controlled environment

viii

Page l'l

15

26

27

29

31

32

35

ix

Table

9 . Effect of GA on dry weight of steinpetiole, leaflet, and total forcige production of alfalfa for five harvests in a controlled environment ....

Page

36

10. Effect of GA on transpired water, height of alfalfa for five harvests in a controlled environment

11. Effect of GA on the anatomy of alfalfa stems

12. Analyses of variance for the transpiration data, water per cm^ per hr, measured on Mesa-Sirsa alfalfa in a program controlled environment

13 Effect of GA on several, characteristics measured on two clones of Mesa-Sirsa alfalfa grown in a program controlled environment

1'i. Summary of the analyses of variance for testing the effect of GA on various characteristics measured on Clone 2 of

Mesa-Sirsa alfalfa in a controlled environment

15. Effect of GA on carbohydrate fractions and protein content of roots from

Clone 2 of Mesa-Sirsa alfalfa grown in a controlled environment

16. Effect of GA on yield of Mesa-Sirsa alfalfa grown under field conditions at Tucson, Arizona for two harvcst periods in .1970

17* Effect of GA on yield components and

37

4-3

50

51

58

6l

6'± conditions

Sirsa alfalfa leaves and stems

6 5

68

LIST OF TABLES--Continued

Table

19* Effect of GA on chlorophyll content of primary and secondary leaves of Mesa-

Sirsa alfalfa

20. Effect of GA on carbohydrate fractions and protein content of roots of field grown Mesa-Sirsa alfalfa

X

Page

77

80

ABSTRACT

Plants of Medic.ago sativa L. cultivar 'Mesa-Sirsa' were grown in lathhouse, greenhouse, growth chamber, and field environments and were used to evaluate the effect of various antitranspirant and growth regulator chemicals on water-use efficiency and on physiological, morphological, and anatomical characteristics. Growth regulators used transpirant chemicals were phenylinercuric acetate (PMA) and dodecenylsuccinic acid (DSA). Gibberellic. acid significantly lowered the water-use efficiency of alfalfa in all environments. Indoleacetic acid, CCC, PMA, and DSA did not reduce the amount of water required to produce a unit of dry forage. The antitranspirant chemicals did not reduce the amount of water transpired, and further, DSA caused plant damage when used as a foliar spray.

Gibberellic acid significantly increased the amount of stem tissue produced in all environments which resulted in more total dry-forage production. No effect weis found on the amount of leaflet tissue produced except in experi­ ments where GA stimulated secondary branching.

Flowering was promoted by GA apjilication and morphological changes were evident in the flowering raceme. x.i

Pith cell length, leaf thickncss, internode length, stem length, and rate of stem elongation were increased by GA.

The effect of GA on transpiration was influenced by soil moisture level. Transpiration rates were higher on plants treated with GA when 30 to 55% of the available soil moisture was depleted.

Photosynthesis, respiration, and specific leaf weight (SLW) were significantly decreased by GA treatment.

— 1 were always less on plants treated with GA. However, when the data were expressed on a unit of dry leaflet tissue, GA did not consistently reduce photosynthesis. The time of measure­ ment after treatment and the ago of the plants influenced photosynthesis aiad respiration rates. The SLW was lower on plants treated with GA.

Gibbcrellic acid caused a reduction in the chloro­ phyll 13 content of alfalfa leaves. Extreme chlorosis was noted under field conditions.

Roots from alfalfa plants sprayed with GA had lower percentages of free and acid-hydrolyzable ca.rbohydratcs when grown under growth chamber and field conditions.

Sucrose was the only sugar found in the 0

0%

ethanol extract. Percentage of crude protein was higher in the roots of plants treated with GA.

INTRODUCTION

Alfalfa (Medicuft'o satri.va L.) .is the most .important irrigated foi~age crop grown in Arizona. Alfalfa has the highest consumptive use of water of all the major crops grown in Arizona (19). Consumptive use of water by alfalfa is high because of a long growing season and high yields. Also, in the semiarid climate evaporation is high.

Alfalfa is a high quality feed for livestock con­ sumption. However, if water becomes limited alfalfa production may be shifted to an alternative forage which has a lower water consumption. Therefore, it would be efficient in water utilization. If water consumption by present high yielding cu.ltivars could be reduced without reducing yields, or yields could be increased without in­ creasing water consumption, then the production of alfalfa in areas with limited water would bo greatly enhanced. The above factors would also apply to other crops in either natural rainfall or irrigated areas. The terms water requirement and water-use efficiency are used inter­

This study was initiated with the following

1

To determine the effect of antitranspirant and.. growth regulator chemicals on water-use efficienc of alfalfa.

To determine the effect of antitranspirant and growth regulator chemicals on morphological, physiological., and anatomical characteristics of alfalfa.

REVIEW OF LITERATURE

Water Requirement of Alfalfa

There are approximately 80,000 hectares of alfalfa in Arizona. Alfalfa in the Salt River Project utilizes

'i. 3 inches) of water per year (19) Alfalfa production creates a large demand for water in an area where water is becoming limited for agricultural purposes.

The water requirement of alfalfa varies with different environmental conditions (9)* The literature on water requirement in both greenhouse and field conditions has been reviewed extensively (l, 11, 32). The water re­ quirement for alfalfa varied from 657 to l,068over a 7-year in the water-use efficiency of alfalfa grown with varying moisture regimes. Genotypes within a cultivar exhibited as much variation as differences among cultivars (ll).

Minimum water-use efficiency values were associated with maximum production of dry forage in most species.

Kelley (33) listed several factors which .influence the water requirement of plants such as soil moisture, soil type, fertility, and various climatic conditions.

Other factors such as disease, salinity, chemical agents, and stage of growth also influence water utilization. Thorn

3

cuid Iloltz (6:i.) concluded that any condition which disturbed the normal processes of the plant affected the water requirement.

Several chemicals applied to various species have affected water utilization (59)• Plants of sorghum

(Sorghum vulgare Pers treated with dalapon (2,2-dich.loropropionic acid) had a higlier water requirement in l6 days

(3376) compared to the nontreated (65^) plants (68). Coiner

(.12) found no effect of pyrazon (5-ami]io-'l-chloro-2-phenyl-

3(2H)-pyridazinone) on the water-use efficiency of sugarment. Olsen et al. (48) used hexodecanol and octodecanol on corn (Zea mays L.) and found no reduction in water utilization; however, production was lower at high rates of application.

Brcngle (8) found no effect of phenylmercuric but damage to the ears and a slightly lower yield were observed. Swoet orange (Citrus sinensIs Blanco) treated with latex or silicone coatings exhibited a lower water requirement (39)* These investigators reported leaf burn and morplio.log.ical changes in the treated plants.

Plant and llalevy (53) used two growth retarding chemicals on wheat and found no effect

011 the water-use

efficicncy. Other experiments with o. growth retardant have shown an interaction between chemical treatment and moisture regime of the soil (^k).

Ti'ansplratlori Rates of Alfalfa

Very little information is available in the literature on the transpiration rates of alfalfa expressed on a leaf area basis. Most of the literature on water use by alfalfa deals primarily with total consumptive use or

Ehrler (.17) reported differences in the amount of water absorbed by cultivars 'Lahontan utilized less water than 'Moapa' in two experiments; however, no values were reported for either cultivar. lie further reported as the saturation deficit varied from 0 to 50 nib, transpiration

_ 2 - 1 increased from 0 to 300 g m hr . He reported a decrease in transpiration rates as root temperatures were lowered.

Al-Kawaz (.1) found rates among genotypes of 'Mesa-

— —1 to vary from 1.00 to 'l.l4 g H^O dm hr However, these results should be viewed with caution as they are single plant observations in an unreplicated experiment.

Al-Kawaz showed a decrease in transpiration rates as the plants .reached maturity when averaged over all genotypes within a growth stage.

6

Effect of Chemicals on Transpiration

No data are available on the transpiration rates of alfalfa per unit of leaf tissue as affected by chemical treatment. Hales (26) showed a significant reduction .in the total amount of water used by alfalfa when treated with various antitranspirants; however, these data gave no indication of the amount transpired per unit area of leaf.

Some chemical treatments caused foliar damage and reduced growth which may have reduced the total amount of water utilized.

Zelitch and Waggoner (7'0 studied the effect of various chemicals on the transpiration rate of various species. They found PMA and other compounds reduced transpiration in some species. For example, PMA reduced i (. :i. an leaf disks and intact leaves (73, 7^). Photosynthetic and the relative growth rates varied with different environ­ ments. Shimshi (5$) confirmed the data of Zelitch and

Waggoner where he noted a reduction in transpiration of tobacco and Helianthus animus L. when grown in an open environment. Turner and Waggoner

(Gh)

reported a 10% reduction in water use by Plnns resinosa Ait. when sprayed with PMA under field conditions.

Friesen and Dew (ii2) observed a reduction in transpiration of a weed species when treated with two

transpiration as rapidly as the other herbicide. Todd and

Propst (62) noted a reduction in transpiration of leaves

As r hich were subjected to treatment with o'/->one and ozonated o-4- ethyl -6 is amino)-S-trianine] caused a reduction in transpiration of respectively (59)-

Livne and Vaadia (35) found a differential response in barley (Hordeum vulgare L.) depending upon the type of chemical used. An increase in transpiration occurred with kinetin and gibberellic acid (GA), no response was noted when adenine and indoleacetic acid (1AA) were used, and a reduction in the rate occurred when actinomyc.in D and puromycin were applied to the .leaves. Luke and Freeman

(37) observed no effect on transpiration of excised oat

(Avena satlva L.) leaves when treated with GA; however, a stimulation was noted when cytokinins were applied. Later, these researchers were unable to show an effect of cytokinin on dicotyledonous species (38). Nieinan and

Bernstein (46) reported tin increase in transpiration of bean leaves treated with GA.

The use of long ch;iin alcohols

011 corn and barley reduced yield more than transpiration ('l7, 48). Gale,

Roberts, and llagctn (24) reviewed the literature on the use of alcohols as ;intitraiispirajits and concluded, on the basis of 17 repoi'ts in which all but one found a reduction in

growth, that these materials were unsuitable as effective

8

antitranspirants. These alcohols offer more resistance to

CO^ exchange than to water movement.

Photosynthetic Rates of Alfalfa

The photosynthetic rate of alfalfa varies with the age of leaves, environment, and the leaf area index (LAI)

(23, 6 9 ) • El-Tabbakh ( l 8 ) reported no differences between field and greenhouse plants in rate of assimilation.

— —1 mg COr> dm hr ' , and Mesa-Sirsa had an average of 43 mg

- 1

COg dm hr when measured at 32 C.

Potassium nutrition has been shown to be important in the photosynthetic process (13)• As potassium increased from 0 to 5%, an increase in photosynthetic rate was found

— 2 — 1

(8 to 20 mg dm hr "). Stomatal closure may have been responsible for the low rates at low potassium levels.

Fuess and Tesar ( 2 3 ) found 3

-wee k

old leaves were less than one-seventh as active as 5-day-old leaves in oxygen evolution. These investigators also found an increase in LAI as the plant reached the bud stage of development. Wilfong, Disown, and Blaser (69) reported that photosynthesis .increased as the LAI increased to about

4 and then the rates leveled off. Maximum rates occurred when 915% of the incident light was intercepted.

Pearce, Brown, and Blaser (5l) found a difference

9

in pliotosyntlietic rates between plants grown in the field and in growth chambers. Young leaves in the field had a

- 1 rate of 52 compared to 35 mg C0^ dm hr for the same age leaves in growth chamber environments. However, when the rates were expressed on a dry weight basis no difference existed. This difference in results can be accounted for

2 by the specific leaf weight (SLW, mg/cm ). The SLW was larger in the field than in the growth chamber. Specific leaf weight increased as the leaves matured (5l)« Pearce et al. (52) showed a positive correlation between SLW and pliotosyntlietic rates. Their data showed that the photo-

- 2 - 1 synthetic .rate varied from 20 to 50 mg CO dm hr ' as the

dt

SLW changed from 1.9 to 5»3*

Al-Kawaz (l) reported differences among genotypes of Mesa-Sirsa in both photosynthesis and respiration. The rates of both physiological processes decreased with maturity.

Effect of Chemicals on Photosyivthes:i.s

G.ibberel lie acid has increased the respiration of hypocotyls and cotyledons in Cucunils sat.i.vus L. and decreased the rate in the radicle. Also, an increase in catalase activity was fouvicl ( 2 7 ) . Troltarne and Stoddart

( 6 3 )

found an inci-oa.se in the activity of ribulose-1

10

contributed the increase to an overall effect in promoting protein synthesis rather than a specific action on the enzyme. These researchers suggested GA may be part of a system mediating the pbytocliromc system.

Other investigators (25, 'l-2) found no effect on

'i manometric measurements of leaf disk and ' CO^ uptake on leaves treated with GA. However, Coulombe and Paquin (15) noted an .increase in respiration and photosynthesis 1 to 2 hours after GA application and maximum effect was noted

5 to 6 hr after treatment. Alvim (2) reported an increase

L.) when treated with GA. Ousheva, Popov, and Manolova when GA was applied to the media.

Photosynthesis was inhibited when two herbicides were applied to Scenedesnns sp. The rates were mediated by light intensity (65) Todd and Pr*opst (62) found a reduction in photosynthesis when ozone was applied to leaf tissues.

Humphries, Weibank, and Witts ( 2 9 ) found a reduc­ tion in NAR of wheat when treated with CCC [(2-chloroethyl) r m 1 mm n u chloride.]. Plienylmercuric acetate has been shown to cause ci reduction in photosynthetic rates of different plant species (57, 59)•

Effect of Chemicals on Alfalfa

Massengale and Medlar (4o) found that TIBA (2,3,5triiodobenzoic acid) and 2,4-,5-T ( k acetic acid) increased stem elongation and IAA caused a reduction in stem length. No effect on the number of nodes per stem was found; however, leaf morphology showed some variation from the nontreated plants. Yeh and Bingham (70) showed that IAA reduced stem elongation of two genotypes.

These researchers found a clonal interaction in the number

GA and TIBA. Other investigators (.10, 21, 71) showed an increase in stem height in response to GA application.

Corns (I'l) found no response of 'Gi-'imni

1 alfalfa to

GA treatment. However, Finn and Nielsen (2l) reported a

.reduction in root growth and an increase in total protein even though a decrease in percentage protein on a dry weight basis was found. Carlson, Sprague, and Washko (10) found a reduction in total carbohydrates when alfalfa was treated with GA. Yeh (7-1) reported that carbohydrate levels varied in response to GA application. lie found an increase in plants grown in the field and a decrease in greenhouse grown plants.

MATERIALS AND METHODS

Plants of Mesa-Sirsa were used to investigate the effects of growth regulator and antitranspirant chemicals on water-use efficiency, transpiration rates, photo­ synthesis, and anatomical features of alfalfa. Studies were conducted in greenhouse, latlihouse, and gi-owth chamber environments.

The method of plant cvi.lture was basically the same in all experiments. Plants were grown in plastic pots with a hole 1.2 cm in diameter at the base of each pot to alloAf for drainage during plant establishment. Pea gravel was added to cover the bottom and a known weight of a mixture and organic fertilizer was added to each pot. The ratio of peatmoss, with .100 g of organic fertilizer (milorganite) and 3 g of sulfur per 20 kg.

In all experiments there was one plant per pot which was cut 7 cm above the soil surface at the beginning of each trial. During plant establishment forage above the 7 cm level was removed at the 1/10 bloom stage.

Styrofoam was added to the surPace of each pot to reduce e v a p o r a t i o n (.13.) a n d t h e p o t s w e r e w a t e r e d t o b r i n g t h e soil to field capacity (27%) at the start of each trial.

13

The experimental design wcis a randomized complete block in all experiments. Each pot was weighed daily and rewatered when 55/° of the available: soil moisture had been utilized. The plants wore harvested at 1/10 bloom and in each experiment the amoimt of dry forage (80 C for 2k hr) was divided by the amount of water utilized to detex-mine the water requirement. Leaflet to stem-petiole ratios were calculated in all experiments. Height of steins and number of nodes per stem were determined prior to harvest. Per­ centage N was measured by the micro-lcjeldahl method (3) and multiplied by 6.25 to estimate crude protein percentage.

Lath and Greenhouse Experiments

Rates and methods of application of chemicals used in a greenhouse environment are shown in Table 1. The abbreviation following cach chemical name will be used in future discussion. All plants received the first chemical application when regrowth

Wcis

k

cm tall. The second application was applied k days later. Plants used in this study were 6 months old and the experiment was conducted in

January, 1969- Average maximum and minimum temperatures were 3-1 and .1.8 C, respectively. Average relative humidity was 50/n. Six treatments represented once in each of eight and chemicals used in a lathhouse environment at the Tucson

Table 1. Chemicals, rates, and methods of application used on seeded plants of

Mesa-Sirsa alfalfa in a controlled greenhouse environment.

Chemical*

Gibberellic acid (GA)

Indoleacetic acid (IAA)

Methods of application f i foliar spray

Phenylmercuric acetate (PMA) foliar spray

Dodecenylsuccinic acid (DSA) foliar spray

Concentration

100 mg/liter

1 X H O

5

X

10

5

M

Application rates per plant

Low High

1 ml

1 ml

1

1

ml ml

2 ml

2 ml

2 ml

2 ml trimetliylammonium chloride

(CCC)

Water soil drench foliar spray

223 mg/100 ml

0

*A11 chemicals were used in an aqueous solution.

100 ml 200 ml

1 ml 2 ml

Table 2. Chemicals and rates used on seeded plants of Mesa-Sirsa alfalfa in a lathhouse environment.

Rates

+

Chemical

1

2

3

GA*

P>1A* ccc*

Water plus Tween 20

100 mg/liter

1 x 10~

3

M

2 M

0 2%

0 i

200 mg/liter

-4

1 x 3.0 M

1 M

300 mg/liter

1 x 10"

5

M

1 x 10~

2

M

k

z i00 mg/liter

1 X

10~

6

M

1 X

H O

*0.2% Tween 20 added to each aqueous solution of chemicals.

+

1 ml of each solution was applied as a foliar spray.

H

16

ant Materials Center in June, 19 9 The numb chemicals was reduced since there was either no effect or plant damage noted from the chemicals described in Table 1.

23, 19^9 and the PiMA was applied on June 30, 19^9 The plants in this study were 3 months old. Average maximum and minimum temperatures were 'll and 19 C, respectively.

Average relative humidity was 52%. Fourteen treatments represented once in each of I'l blocks were used.

Growth Chamber Experiments

Several growth chamber experiments were conducted to elucidate the significant effect of GA on water utiliza­ tion of alfalfa. One of the first objectives was to determine if a carryover .response could be measured on grown for five consecutive harvests. Two groups, each with

12 plants, were grown in a controlled environmental chamber.

The day and night temperatures were 26 + 1 and l6 +_ 1 C, respectively, during the 16 hr photoperiod. Light intensity was 185•8 lux at plant height. The first growth period was to adjust the piants to the different conditions of the growth chamber-. During the second growth period,

Group 1 was sprayed with L ml of GA (150 nig/liter) when regrowth was approximately 3 cm in height. A second application was applied 'i days later. Group 2 was treated

in the same manner during the fourth growth period. Marvests 3 and 5 were used to evaluate carryover effects.

Height measurements were made at 2-day intervals during each treated harvest. Stem tissue was collected from the second harvest to measure the effect of CIA on the anatomy of alfalfa stems. The samples (0.5 cm) were collected from an area 1 cm above four consecutive nodes located on the basal portion of the tallest stem of each plant. Cross sectional and longitudinal sections were stained with safranine and fast green according to techniques described by Johansen (31)* Cells were measured using a calibrated ocular micrometer.

Transpiration

To measure the effect of GA on transpiration, propagules of two Mesa-Sirsa clones were established.

These clones were selected for vigorous growth when spaced planted in the field. Ten propagules of each clone were grown in the same environmental conditions previously described. Three con.secut.ive harvests were taken.

The first harvest was used for plant adjustment to the environment and help in establishing uniformity among propagules. Two days prior to the second harvest, half of the propagules of each clone were sprayed with 3 nil of GA

(.150 mg/liter) to wet all leaC foliage. The light period

18

hr and a3.1 plants were watered to field capacity. The plants were weighed at periodic intervals to determine the amount of water loss during the next light period and rewatered when

5 5 %

of the available moisture had been utilized. Rewatering was at 1700 hr. This procedure was repeated for 2 consecutive days.

On the third day after the initial spraying, photosynthetic measurements were made in an open system using a

Beckman 215 Infrared Gas Analyzer. Measurement of the entire plant was accomplished by using the plexiglass chamber shown in Fig. 1. Two air intake-holes were located near the base and the air was drawn out through a hole near the center

-

. Leaf eirea and specific leaf weight (SLW) were measured by Xeroxing all the leaves on two randomly selected steins from each plant and determining cm area to weight ratio. Photosynthesis was expressed as the mg of

2

C0 o per dm per hr and also on a dry leaf weight basis

C*t

(80 C for 24 hr). Transpiration rates were expressed as

Photosynthesis and transpiration of the I.eaves below the

7 cm cutoff level were accounted for in the data.

Treatment of the propagules during the third reg.rowth period was the same .as in the second period.

Propagules wore 5 months old at the beginning of this experiment.

Fig. 1. Plexiglass chcimber used to measure the photosynthetic rates of entire alfalfa plants. Note the air intake near the base and exit near the top. The temperature probe is shown in the middle of the chamber.

20

Photosynthesis and Respiration

In the previous experiments, clones reacted differ­ ently to GA treatment. To obtain additional information on photosynthesis and respiration of GA treated plants, a study was conducted in

Avhich

2

h

propagules of Clone 2 were used. The environmental conditions of tb" growth chamber were the same as those described. The plants were grown for two consecutive harvests.

The first harvest was used for the plants to adjust to the environment. During the second growth period half the plants were sprayed with 1 ml of GA (150 mg/liter) five days after cutoff when regrowth had begun. The plants were sprayed at 2300 lir. The treated plants were sprayed again h. and 8 days later with the same concentration but with a volume of 1 and 3 nil, respectively, to wet the leaves.

Photosynthesis and respiration data were collected on four plants of the sprayed and control plants three times at 4-day intervals beginning the day following the

All plants were watered to field capacity at 2300 hr of the day preceding measurement. i 1

The field research for this study was conducted at the University of Arizona Campbell Avenue Farm, Tucson,

Arizona. In October of

.1

969

Av.it

h

21

irrigated to insure sufficient moisture for germination and

The border was 7-92 x 30

; l8 m and it was divided into six plots (3.66 x 8.53 m)• The plants were allowed to establish during the winter and the first forage was removed on April 10, 1970. During the establishment period, irrigation was managed to prevent water stress.

The border was irrigated during the period of study at the applied to fill the entire root zone to field capacity.

No treatments were applied to the regrowth which developed during the period between April 10 and 25 when the forage was again removed.

The treatments on the first harvest for data collection were made on May 15, l6, and 23• Gibberellic acid was applied with a pressure sprayer at the rate of and three served as the control plots. Forage from a

2

.19 '» and soil moisture samples to a depth of 1.22 m were taken at 'i-day intervals beginning on May .1.6 and lasting through May 28.

Ten stems were selected at random from each plot on May 28 and were used to determine height and internode length. Stem and Jeaf samples were collected from the fourth and seventh node and internode from the base to

22

measure the effect of GA on anatomical characteristics.

Also, a leaf was collected fi'om the stem apex. The center leaflet of each leaf was used in all measurements.

During the second harvest the control plots were divided in half in order to evaluate the regrowth on the treated plots of the first harvest. Gibberellic acid application was the same as that previously described except the volume was reduced to 1 liter per plot.

Gibberellic acid was applied at k-day intervals beginning on June 8 and lasting until June l6.

Forage and moisture samples were taken only on

June 21. Beginning on June 9, and at two intervals there­ after until June 21, one stem was selected at random from each plot, placed in a 125 ml polyethylene bottle filled with water, and used to determine photosynthetic and respiration rates. The stems were cut .in the field at 2000, held in a dark room at 25 C, and measurements were made the following day between 0800 and 1000 hi'. A plexiglass chamber shown in fig- 2 was used in the system previously described for the growth chamber studies.

On June 21, ten stems were selected at random from each plot for height and internode length measurements.

Additional forage was collected for chlorophyll determina­ tions as described by Seitz (5^0 Chlorophyll determina­ tions were made on main and secondary leaves separately.

23

Fig. 2. Plexiglass chamber used to measure photosynthetic and respiration rates of plants grown in the field.

2'l

2

Roots from a .19 in ai~ea in all plots were dug at the end of each regrowth period. The roots were immedi­ ately washed, placed on dry ice, and stored at 0 C until they were dried in a freeze-dryer. The samples were ground to pass through a

l l0

mesh screen and carbohydrate determina­ tions were made using extraction techniques described by

Dobrenz (l6) and color.imetric determinations described by

Yemon and Willis (72). Qualitative determinations on the free sugar extract were made by thin layer chromotography methods described by Stahl

(6o).

The samples were spotted on plates coated with silica gel G and impregnated with

0.02 M sodium acetate. The plates were developed with solvent No. 6 described by Stahl (60). The sugars were detected with aniline-diphenylamine spray reagent (60).

RESULTS AND DISCUSSION

I

J athhouse and Grcnnliouse Experiments

Gibbe.roI.lic acid significantly affected the wate.re efficiency of alfalfa (Table 3) Tlie lowest water requireinent va.Iue was found with the high rate of CIA application. Plants treated with GA were lower (P - .05) in water requirement than all other plants treated with antitranspirnnt and growth regulator chemicals when averaged over both rates. No effect on water requirement was found when the plants treated with PMA, IAA, CCC, and

DSA were compared to the control plants,

Plants treated with GA produced the most steinweights were found with the high rate of chemical, applica­ tion. A significant chemical by rate interaction showed that GA treated plants produced more stem-petiole tissue at the high rate of application.

None of the chemicals influenced the amount of leaflet tissue produced when averaged over both rates evident. Maximum and minimum leaflet production was noted

OJI

plants treated with CCC at the low and high .rates,

Table 3* Effect of various chemicals on water-use effi­ ciency of Mesa-Sirsa alfalfa grown in a green­ house environment.

26

Water-use efficiency

Rate CCC GA IAA DSA PMA Control Mean

Low 912* ab

893 ab

939 a

915 ab

9'I8 a

104-5 a

9

Z

12

High 1072 a

764 b •

1071 a

1043 a

986 a

1010 a

992 a 829 b 1005 a

979 a 967 a 1027 a

991

*Values within rates and means followed by the same letter are not significantly different at the .05 level according to Duncan's Multiple Range Test.

27

Tabic k. Effect of various chemicals on. stoni-petio.le and leaflet weight of Mesa-Sirsa alfalfa grown in a greenhouse environment.

CCC GA IAA

Chemical

PMA Control Mean

Low

High ab b

.66

b

.75 ab

1.00

a

.87

a

.80

ab

.52

b

.66

b b

•51 b b

.60

b

.62

b

.60

b

.62

b b b b

Low • 7'i a

Leaflet weight, g

•52 ab

.73 a

. 6 ab ab

.60

ab

.64 a

.'19 b

•71 a

.51 ab ab ab

.56 ab

.62 a

.62

a .62 a .58 a .56 a

.58

a

.56

a

^Values within rates and means followed by the same letter are not significantly different at the .05 level according to Duncan's Multiple Range Test.

Total forage production was lower (P = .05) when

28

high rates of these chemicals were applied (Table 5)•

Maximum forage production occurred on GA treated plants at the high rate of chemical application.

Leaflet to stem-petiole ratios were significantly affected (P = .05) by chemical application (Table 5).

Alfalfa plants treated with GA had a lower leaflet to stem-petiole ratio than any of the other chemical treat­ ments or the control. The lowest ratio was found with plants treated at the high rate of GA.

All chcmicals tested did not influence the number of nodes per stem, number of stems per plant, or transpired compared to untreated plants (23*3 cm).

Water-use efficiency was negatively correlated

(P = .01) with total forage, leaflet weight, and stempetiole weights. The r values were -0.5$, -0.'l2, and

-0.68, respectively.

The results of this study indicated that GA an increased plant height and total forage. Increased forage production was due primarily to an increase in the amount of stem-petiole tissue produced. Transpired water was not affected by chemical treatments; therefore, water requirement was influenced by the significant effect of these chcmicals on dry forage production.

Table 5- Effect of various chemicals on total forage per plant and leaflet to stem-petiole ratio of Mesa-Sirsa alfalfa grown in a greenhouse environment.

Low

High

Low-

High

CCC

1.55* ab

. -99 c

1.27 a

•95 abc ab

GA

1.27 abc

1.72 a

1.49 a cd d

.72 b

IAA DSA

PMA

1.53 ab

1.03 c

1.28 a

Total forage.

1.35 abc

1.02 c

1.19 a

1.29 abc

1.15 be

1.22 a

Leaflet to stem-petiole ratio

•9^ abc abc

.81 bed

1.01 ab

1.06 ab

1.00 a

.96

abc

.88 a

Control

1.21 be

1.16 be

1.19 a

•99 ab

•96 abc

Mean

1-37 a

1.18 b

.89

*Values -within rates and means followed by the same letter are not significantly different at the .05 level according to Duncan's Multiple Range

Test.

• a

30

Jndoleacetic acid had no significant effect on any of the characteristics measured except a slight increase was found in stein height. These results arc: not in agree­ antitranspirant (DSA) caused severe leaf burn when sprayed on alfalfa. Since these chemicals proved ineffectual in the improvement of water use, IAA, and DSA were not used in subsequent experiments.

Gibberellic acid, PMA, and CCC had significant effects on water requirement, total forage, and stempetiole weight when a1fa1fa plants were grown in an open environment (Table 6). The lowest water-use efficiency values were found with plants treated with GA and the highest values were found on plants treated with PMA and

CCC. The range in values varied from 173^ to 2^0k for GA and PMA treated plants, respectively. Water-use efficiency values in the experiment indicated a strong influence of the environment on this characteristic. Briggs and Shantz

(9) reported differences in water requirement because of different environmental conditions.

Maximum forage and stein-petiole tissue production occurred on GA-treated plants. Different rates of GA influenced the amount of stem-petio1e tissue. Minimum forage production occurred on plants treated with CCC.

Leaflet to stem-petiole ratios, stem height, and transpired water values are shown in Table 7* The lowest

31

Table 6. Means of water-use efficicucy, total forage, and stem-petiole tissue as affected by various chemicals applied to Mesa-Sirsa alfalfa grown in i 1

7

13

9

8

6

5

3

4

2

1 l4

11

12

10 efficiency

1738

+

e

1751 e

1915 de

2075 bede

2l6l abed

2198 abed

2227 abed abc

Total forage

r

1 47 a

1.23 ab

1.19 abc

1.17 abc

1.1k

abed

.89 cd

.83 d

•92 bed

; i bed

Stem-petiole weight, g

.67 be

.63 bed

•59 bed

•50 cd

.46 d

.47 d

.56 bed

.50 cd

.49 cd

.50 cd

.54 cd

.46 d 2504 a

.92 bed

*1, 2, 3, anc! 4, 100, 200, 300, 400 mg GA/liter, respectively; 5, 6, 7, and 8, 10-6

1

10-5, 10-4, 10-3 M

PMA

-

'

1

, 10~~, 1, 2 M

Twet'ji

20; 1 , Water.

Values within each column followed by the same according to Duncan's Multiple Range Test.

32

Table 7- Means of leaflet to stem-pet.i and transpired water as affected by various chemicals applied to Mesa-Sirsa alfalfa grown in a lathhouse onvironmcnt at the Tucson Plant

4

7

10

13

9

6

3

2

11

12

1

8 l4

5

Lc

af1et to stem-petiole

.65

+

c

19-8 a

17.7 ab water, g

2111 abc

2432 a

.81 abc

.82 abc

.88 ab

.92 cib

1.00 a

.1.02 a

.1 .04 a

16.6 abc

15-7 be

16

.

13.5 c

15-3 be

13.9 be

13-7 c

13.0 c

13.9 be

14.8 be

1799 cd

1644 d

2273 ab

2171 abc

2316 ab

2234 abc

1895 bed

2019 abed

2094 abc

2335 ab

2093 abc respectively; 5, h , 7, and 8,

10

, 10-5

/j

, 10 respectively; Q, 10, II, and .12, 10

-

'

1

, 3.0-2, i, 2 M CCC, respectively; 13, .2% Tween 20; 14, Water.

*f*

Values within each c.o.lunm followed by the same acconl.ing to Duncan's Mul.tip.l.e Range Test.

33

treated plants. The highest rate of GA increased p.lant height over the control plants. Plants treated with dif­ ferent rates of GA did differ in the amount of water transpired. The least amount of water was transpired by plants treated with CCC. However, this was because severe leaf burn was present on plants sprayed with CCC. In the previous experiment, CCC was applied as a soil drench and no visible effects were noted. Plants treated with PMA did vary from the controls in the amount of water transpired.

This may be due to the length of time in which PMA was applied to the foliage in the experiment. However, these results are in agrceinent with the greenhouse study.

Water requirement was associated (P - .01) with leaflet weight, stem-petiole weight, and total forage. The significant correlations of dry weight of the total forage and yie.Ld components with water-use efficiency .indicate that to select efficient genotypes dry weight production would be a major selection tool.

None of the chemicals had any effect on the number of nodes pea" stem, number of stems per plant, or leaflet

Tlio results of these experiments indicated that GA was the only chemical, which improved the water requirement

of alfalfa without any harmful effects. All other chemicals either had no effect or caused piant damage.

Growth Chamber Experiments

One of the first objectives of the growth chamber experiments was to evaluate the carryover effects of GA on harvest, showed GA lowered (P = .05) the water requirement values when calculated from stem-petiole and total forage weights (Table 0). No effect was found on water require­ ment of each group when averaged over five harvest periods when the values were computed on yield components or total forage production. The water requirement values based on leaflet weights were not significantly affected by GA treatment.

Gibberellic acid had significant effects on yield components and total forage of alfalfa (Table 9)• A significant interaction (P = .05) indicated a positive response in the amount of forage produced by each group of plants during the harvest in which they received GA application.

Transpired water, leaflet to stem-petiole ratios, and stem height were affected by GA application (Table 10).

More water was transpired by the group of" plants which was treated with GA. During the throe growth periods when

Table 8. Effect of GA on water requirement values of alfalfa based on yield components and total forage for five harvests in a controlled environment.

35

1 J. c:UJ. U

Group

2

1

2

3

4

5

1298

. b

1121 a

1193 a 1254 a 1409 b 1354 a 1302 a

1570

b 1248 a

1229

a i46o a 1325 a

1

2

Leaflet

1844 a

2188

a 2000 a

1676

a

2079 a 1685 a 1902 a

2099

a 1888 a

1

2

757 b

669

a

752 a 736 a

846 b

833 a 785 a

858

b

711 a

74O

ci

856

a

767 a

*Values between groups within each harvest followed by the same letter arc not significantly different at the

.05 level according to Duncan's Multiple Range Test.

Group 1 treated 2nd harvest

Group 2 treated 'id' harvest

Each value is a mean of 12 observations.

36

Table 9* Effect of GA on dry weight of stem-petiole, leaflet, and total forage production of alfalfa for five harvests in a controlled environment. i

+

2

1

2

Harvest

3

4

5

Mean

2

11

+ +

a

2.73 b

3.

3

2

a

1 a 3.72 a 4

26

b 2

2.83 a

1

2

.50

a 1.64 b 2.4l a 2 a 1

. 5 3 a

1 a

2.6L

b 2

75 b 1

1

2

3 forage, ,1

4 b 5-87 a 5

.29

a 4.57 a

.83

a

3-59 a 6.33 a 7

3

*Values between groups within each harvest followed by the same letter are not significantly different at the

.05 level according to Duncan's Multiple Range Test.

Ciroup 1 treated 2nd harvest

Group 2 treated 'it!) harvest

-J* "t* ^

Each value is a mean of .12 observations.

Table 10. Effect of GA on transpired water, leaflet to five harvests in a controlled environment.

37

Group

1

2

1

2663 a

25'±3 a

4

5 l'r nn | ed wa .

.0;

3225 b 4228 a 4-601 a 2701 a 3500 a

2852 a 4343 a

5.I.15

b

2936

a 3558 a

1

2

.72 b

Leaflet to stem-petiole ratio •

.60 a .71 a .66 a .62 a .66 a

.67

a

.76

b .74 a

.66

a .70 b .71 a

.1

2

'17.8 a

4-9.0 a

Height

.111

53.2 b 51.0 a 59-3 a 57.4 a

53.7 a

43.9 49.3 cl

62.3 a 55-4 a 52.0 a

*Valu.es between groups within each harvest followed by the same letter are not significantly different at the

.05 level according to Duncan's Multiple Range Test.

+

Group 1 treated 2nd harvest

Each value is a mean of 12 observations.

neither group was treated no difference in the amount of transpired water was found.

The effect of GA on the leaflet to stem-petiole ratios was not consistent. Differences were found for harvest 1, 2, and 5• Stem height was increased only on

38

the second harvest by GA.

Gibbcrellic acid did not appear to have any influence on any variable measured on the plants during the harvest following GA application except on leaflet weight in the third harvest and leaflet to stem-petiole ratio in the fifth harvest.

Gibbcrellic acid hiuJ no significant effect on protein percentage of either the leaflet

o3.~

stem-petiole tissue. However, total protein, was increased in the plants treated with GA and followed the same pattern as the dry weight changes in each harvest.

Tli e .results of th es-e experiments indicated that the response of alfalfa to GA treatments was similar to numerous other species. Increased stem and leaf]et dry weights have been reported with bean (2). Evtushenko (20) reported GA was not transferred from one stem to another o11. the same plant and response was limited to growing parts above the was found. Lovell and Booth (36) found no change in the

The length of individual internodes was affected by

GA (Fig. 3)» Most of the internodes increased in total length which result,ed in the increased plant height rather than more nodes per stem. The largest differences in internode length were found nearest the base of the stem.

1 u I. o s Delia. He reported differences in internode length depending on the location on the stem and time of

GA treatment. Moore (43) found similar results in the

'Alaska' pea.

Stem length was increased by GA treatment (Fig. k).

Larger differences in stem length were found between the treated and control, plants as the plants reached maturity.

Different rates of stem elongation were found when alfalfa plants were sprayed with GA (Fig. 5)- Plants treated with

GA showed a faster rate of elongation h- days eifter spray­ ing. Gibberellic acid was applied on the 7th and 1.1th day following cutoff. The increase .in stein length occurred at different rates depending on time of measurement and GA application. Moore (^3) reported there wore periods w r hen peas were more sensitive to GA application. The response

The data for cell lengths and the number of xylem cells per vascular bundle are shown in Table 11. in general, plants treated with GA had longer pith cells.

However, some genotypes did not respond to GA application.

CD o

'S3

CI

KEY: • A = TREATED

O o

A = CONTROL

o

c

1

2

3 4 S 5 7 S S 10

INTERNODE LOCATION

Fig.

3-

Effect of GA on length of individual internodes of alfalfa grown in a controlled environment. Internodes are numbered consecutively from cutoff level (one) to stein tip (ten).

«£-

6

KEY : © = TRERTED a= CONTROL

DAYS RFTER CUTOFF

i . Effect of GA oil height of alfalfa steins grown in a

KEY: Q= TREATED a= CONTROL

DAYS RFTER CUTOFF

alfalfa grown in a controlled environment.

'i3

Table 11. Effect of 01 A on the anatomy of alfalfa st

Treated

Control

. 3 8 a*

Internode

2

3 k

Pith cell length, 111111

.36 a

.29 a .30 a

•32 a .25 a

Mean

•33 a

Control

No. of xylem cells per vascular bundle

23.9 a

22.0 a 20.0 a 17-6 a

20.9 a

22.7 a 21.1 a 19-0 a 16.2 a

*Vc»Iues between groups within each internode followed by the same letter are not significantly different at the .05 level according to Duncan's Multiple Range Test.

Base of plant.

kh

The longest colls were located in the internodes (l and 2,

Tabic 11) nearest the basal end of the stem and decreased toward the stem apex. The results of cell length and

Struekmeyer (7) reported that GA application caused cell elongation and a smaller stem diameter in various plant species. Earlier, these investigators had reported similar results for soybeans (6). ff e number of xylein cells between the treated and control plants. Morey and Cronshaw (kh) found that GA had no effect on the amount of secondary xylem in Acer rubrum and

GA stimulated cambial activity in localized regions of the stem.

Effect of GA on Transpiration

Transpiration rates were not constant for two the first hour following the dark period. The rates declined during the day as soil moisture tensions increased. The plants were rewatered at ]. 700 hr. During the period between 1700 and 2000 hi

- transpiration rates increased because of the lower soil moisture tensions. A rapid decline occurred during the period between 2000 and

2300 hr. Differences (P - .05) between the clones occurred

controlled environment.

TIME (HOURS3

4-6 found during the dark period. Transpiration rates between clones were larger

1 when 30-55/" of the available soil moisture was utilized. Selection of alfalfa genotypes which have low transpiration rates should be done at low soil moisture levels. However, the difference found in these clones may not be sufficient to detect under field conditions.

The rates reported by Al-Kawaz (1) arc lower than those of the present study. Ehrler (.17) showed differences in the amount of water absorbed as the saturation deficit changed. Therefore, difference between the reported rates can probably be attributed to the different environments.

Gibberellic acid affected the transpiration rates of alfalfa (Fig. 7)- I", general, higher rates were found on plants treated with GA. Higher transpiration rates have been reported in tomato and beans when treated with GA

(15, '16). However, Luke and Freeman (3$) found no effect

Each clone responded differently to GA application

(Fig. 8). Clone 2 showed a larger increase in the trans­ piration rates with GA treatment than did Clone 1. These experiments were conducted over a 2-day period and Clone 2 responded similarly both days. However, Clone 1 showed a decrease the first flay and cin increase the second day, which caused a significant day by clone interaction.

O

C7

KEY: 0 =CONTROL

O c

A

= TREATED

c

CM

CTJ

o o o

2330

TIME (HOURS)

Fig. (. Effect of GA on the transpiration rates of Mesa-Sirsa alfalfa grown in a controlled environment.

CNTRL-CLN2

t

TIME (HOURS)

Fig. 8. Effect of GA on the transpiration rates of two clones of Mesa-Sirsa alfalfa grora in a controlled environment.

CO

i

L

9

(P = .05). A summary of the analyses of variance for each time period is shown in Table 12. The experiment was repeated with the same clones and similar results were found.

Data for several characteristics, measured on two clones used in the transpiration experiments, exhibited variable responses to GA treatment (Table 13)« No differ­ ences were found in several of the characteristics measured. This was expected because GA was applied only 2 days prior to harvest. However, differences were found in the photosynthetic rates. A significant clone by treatment interaction was found. This interaction was evident whether the data were expressed on a leaf area or leaf weight basis. The highest rate of photosynthesis was found in Clone 2 treated with GA. Clone 1 and Clone 2 showed a decrease and an increase in the photosynthetic rates, respectively, in response to GA application.

Differences were found in the SLW of the leaves.

The SLW was lower in the treated plants of Clone 1 and no differences were found in Clone 2.

Effect of GA on Photosynthesis and Respiration

Effects of GA on several parameters measured on

Clone 2 of Mesa-Sirsa alfalfa are shown in Figs. 9 to .1 l

L.

Significant differences for all characteristics except SLW

50

Tabl Analyses of variance for the transpiration data,

Components

Time

0 7 0 0 OFLOO 1 1 0 0 I'JOO 1 7 0 0 2 0 0 0 2 3 0 0

Clone

Treatment ns ns

Clone by treatment ns

Day lis

Day by clone ns ns Day by treatment

Day by clone by treatment lis

ns

ns ns

* ns ns

*

ns ns ns ns ns ns ns

** ns

* ns ns ns

:|;

* ns

ns

ns ns ns ns ns ns ns lis ns

** ns ns ns ns ns ns Not significant.

.1 f ant .05 level. gni :i c

Table 13 Effect of GA on several characteristics measured on two clones of

Mesa-Sirsa alfalfa grown in a program controlled environment.

Characteristics

Stem-petiole weight, g

Leaflet weight, g

Total forage, g

Transpired water, g

Water requirement

Leaflet to stem-petiole ratio

Per cent moisture

Apparent photosynthesis'

Apparent photosynthesis

Specific leaf weight, mg/cm

Leaf nrea. cm-

Clone 1

Control Treated

1279 s.

395 b

.56 a

80

1 a

8i 7 b

k

• 3 a

260 a

.90 a

.78

a

109'5 a

384 b

.48 b

81 8 a

n

6 b

253 a

Clone 2

Control Treated

.76

a

.88 a

1567 a 1312 a

539 a

496 a

. 'i ab

80

80 1 a

90

9

ab 100

29

3

3 b

309 a

250

a

*Values within characteristics followed by the same letter are not significantly different at the .05 level according to Duncan's Multiple Range

Test. Each value is a mean of five observations.

' mg C0 o g hr

Kb f o = i Rc.R i c.0 * = CONTROL

RESTED

CONiROL

rw

p

To

•—r

o

UJ y

UJ al

LU

O a: i cr

10

DRYS RFTER CUTOFF

K

DRYS RFTER CUTOFF

Fig. 9* Effect of GA on the percentage moisture and total forage of Mesa-Sirsa alfalfa grown in a controlled environment. cc

KEY: © = TRERTED

* = CONTROL

KEY: 0= TRERTED ^ = CQNTRO'

C)

LiJ

CE

LJ

!

1

14

DRYS RFTER CUTCF

DRYS RFTER CUTOFF

Effect cf G.A on the s'ceni-peticle and leaflet weights of Mesa-Sirsa

i

KEY: e

=

TRERTED a

=

CONTROL KEY : o =TREATED

A

=CONTROL

cr:

ZD

o

i;J

OC

L'J

! o:

~j I

DRY-S RFTER CUTOFF

GRYS RFTER CUTOFF

11. Effecl of GA on transpired vrater and water requirement of Mesa-Sirsa

\JI

KEY: o = IRERIED

^ = CONTROL

KEY: o=TREATED a = CONTROL

C3

00 cb

to

1^

10

DRYS fiFTER CUTOFF

1

14

DRYS RFTER CUTOFF

Effect of GA on leaflet to stem-petiole ratio and specific leaf weight of Wcsa-Sirsa alfalfa grown in a controlled environment.

KEY: o = TRERTED a = CONTROL

KEY: o=TRERTED a = CONTROL

o cn

ai

i—i

Q_

CO

UJ

O

CE

C£ i—i

Q-

CO

UJ

CC

DRYS RFTER CUTOFF DRYS RFTER CUTOFF

Fig. 13' Effect of GA on respiration rates of Mesa Sirsa alfalfa grown in a controlled environment. Left) mg CC>

2 dm~2 hr~l. Right) mg CC>

2 g-1 hr~l ui

C7\

o

CO

KEY: o= TREATED a

=

CONTROL

<s

CO

KEY: o = TRERTED ^ = CONTROL

o

CO

i—i

CO

UJ

31

I— o

CO

>-

CO o

I— o

O

LO

32

Q_

O d o

CJ

,

CO

LU

x:

o

I—

CM ~

CO

^—

CO o

I— o

32

Q_ o o

6

10

DAYS AFTER CUTOFF

14

DAYS AFTER CUTOFF

Fig. l4. Effect of GA on photosynthetic rates of Mesa-Sirsa alfalfa grown in a controlled environment. Left) mg CO dm

-

^ hr~l. Right) rag C0 o g~l hr~l.

u

Z

VJ1

Table 1 . Summary of the analyses of variance for testing the effect of GA on various characteristics measured on Clone 2 of Mesa-Sirsa alfalfa in a controlled environment.

Characteristic

Fresh weight, g

Transpired water, g

Stem-petiole weight, g

Leaflet weight, g

Total forage, g

V."ater-use efficiency

Leaflet to stem-petiole ratio

Specific leaf weight, mg/cm^

Per cent moisture

Respiration, mg CO2 dm

-

^ hr~l

Photosynthesis, mg CO2 dm~2 hr*"l

Respiration, mg CO2 g~hr-1

Photosynthesis, mg CO2 hr-1 ns Not significant.

*•05 level of significance.

**.01 level of significance.

Treatment

* ns ns ns ns lis ns ns ns ns

Harvest

*

*

* ns ns ns

Treatment by harvest ns

11 s

* ns

11s

* ns ns ns ns ns ns

59

The data for total forage, each component of yield, and transpired water show an approximate linear increase with maturity. The plants Avere in the bud stage of development at the final harvest. The plants treated with GA had a higher percentage moisture and the difference became larger with .increased plant age (Fig. 9)» Shchulcina (55) found a lower percentage moisture in the leaves of alfalfa when treated with GA.

Water requirement values for the treated plants remained constant over time compared to the increase in nontreated plants (Fig. 11). The reduction in water requirement was primarily due to increased stein-petiole production with no difference in the amount of water transpired or leaflet production. The leaflet to stempetiole ratio of the treated propagules was not signifi­ cantly lower than the control; however, the trend was a lower ratio in the treated plants.

Differences were found in the SLW between treated and control plants and the effect became larger with time

(Fig.

12).

The SLW was always lower for the treated plants. Pearce et al

A

^aried with leaf age and was influenced by light intensity. They reported SLW values varied from

1

.9 to 5«5« The SLW values of this experiment varied from 2.0 to 2.9.

Respiration differed among harvests whether the data were expressed on leaf area or leaf weight basis

6o

(Fig. 13). The same gcnural pattern was evident in both methods of data expression, with the control plants lower varied from 1.0 to 3*1

- 2

CO

0 din hi" " . These values

C-t

compare to those reported by Al-Kawaz (.!)•

Photosynthctic rates were always lower on plants treated with GA when the data were expressed on a unit of on leaf weight the control plants were lower in the second and third harvests. These results can be attributed to a decrease in the SLW of the treated plants. The same leaf area of the treated plants did not weigh the same as that of nontrcated plants. Therefore, on a weight basis there

Coulombe and Paquin (15) indicated that GA influ­ enced the rate of respiration and photosynthesis of tomato. They reported the maximum effect resulting from

GA application was 5 hr after treatment and then the rates began to decline to normal. The measurements on alfalfa maximum response may not have been found in this study.

The percentages of each carbohydrate fraction and

The .amount of free sugars and the ncid-hydi'olyzoble frac­

Table IfJ. Effect ol" GA on c e fractions and protein content of roots from Clone 2 of Mesa-

6 i

Plant

Treated

Control

% of control.

Carbohydrate fractions, %

80% ethanol

H

2

S0

4

12.0 b

:i

4. a

8.1

.4

17.6

b

28.4 a

62.2

Protein percentage

9.5 a

9-0 a

105-9

*Values between treatments for each parameter followed 'by the same letter are not significant at the .05 level according to Duncan's Multiple Range Test. o h (36) f soluble carbohydrates in potatoes when treated with GA.

The results of this study suggest the increase in stem-petiole tissue was because the root reserves were not

Arizona lias shown that starch was the major storage compound

. Other research ( , 36, >15) has shown GA influenced the amount of starch stored in various plant organs. The photosynthetic products were probably not trnjis.l ocatod to the roots and were used to increase the dry weight of the stem-petiole tissue in alfalfa.

6 2

times in. the f i.e 'l d at 4 day iiitcrva

I

s beginning who regrovth was approxiniately

G

cm. Gibbercllic acid significantly affccted

C

I

.VA

,' forage accumulation under .field condi­ tions (Fig. 15)• Plants which were sprayed with GA produced more forage (P = .05) than did the control plants.

A rapid increase was noted during the first three harvests.

Significant differences in forage yields at the bud and early bloom stage of plant development for each harvest were found for plants sprayed with GA (Table l6). The treated plants yielded more forage than the nontreated plants (P = .05)- However, regrowth was reduced by GA treatment.

The effect of GA on components of yield and leaflet to stem-petiole ratios was also evaluated under field conditions (Table 17)• In general, primary and secondary stem weights were greater on the alfalfa plants sprayed with GA. The total amount of leaf tissue was not influ­ enced in either harvest by GA treatment. The leaflet to stem-petiole ratios were lower on the treated plants in both harvests because of an increase in stem weight. The treated and nontreated plants in Pig. 16 illustrate the effects of GA on stem height and secondary branching of alfalfa plants grown under field conditions. The effect of

KEY s o= TRERTED a = CONTROL

6 3

DRYS RFTER CUTOFF

Fig.

15.

Effect of GA on the yield of Mes^-Sirsn alfalfa crown under field conditions. Data "taken from an

o

area ot .19 in".

6 4

Table .1.6. Effect of GA on yield of Mes a alfalfa grown under field conditions at Tucson, Arizona for two harvest periods in 1970.

Harvest

p c

r d

Treated g

Dry forage production (g/plot)

Control

S

Regrowth

May 28

June 22

67-5 a*

78.5 a

56.7 b

50-9 b

-

33.1 c harvest period ore not significantly different according to

Duncan's Multiple Range Test. Mean based on 3 samples

Table

1 7 -

Effect of GA on yield components and leaflet to stem-petiole ratios of

Mesa-Sirsa alfalfa grora under field conditions.

May 28

Treated

Primary PrimaryS Total Total t leaves s ems 1 a t eaves

Total forage

8.78

a*

2

Control 6.14 b

2 34 a

Components

2.05 a viol

rr

2 31 a

10.83

a 4.51 a 15-33 a

.83 a 1.71 a

6.97 a 4.05 a 11.01 a

June 22

Treated

7.07 a 1.

Control

5.08 b

.52 b

2 40 a

2.26 a

1-37 b

8.37 a 4.21 a 12.58 a

5

b

3.63

a 9.23 b

May 28

Treated

Control

Primaryaxis

.25 b

.38 a

•Secondaryaxis

2.15 a

Total

.41 b

.58

a

June 22

Treated

Control

.34 b

.44 b

1-39 b

2.26 a

.65

a are not significantly different at the

.05 level according to Duncan's Multiple

Range Test. for each parameter followed by the same letter

H

•u

HB

Em

66

•1

Fig. l6. Effect of GA on stem length and secondary branching. l) Control. 2) Treated.

67

GA on these parameters was also evident in the growth chamber studies.

The amount of water utilized by the treated and nontreated plants was not influenced by GA application.

Significant differences were found in the amount of water absorbed at different soil depths over the period of the study. However, no harvest by soil depth-level interaction was found. Therefore, the plants which were sprayed with

GA had a lower water requirement based on forage produc­

Anatomical measurements on stems and leaves of alfalfa indicated GA influenced these parameters (Table l8). Data from the field experiments agree with the growth-chamber experiments. Increases in the parenchyma cell length were evident in the central pith. Also, individual internodc lengths were comparable to the previ­ ous results shown in Fig. J. Leaflets were thicker

011 treated plants near the base of the stem. Spraying with

GA affected other anatomical features of alfalfa leaves

(Fig. 17)• Intercellular spaces were more abundant in the treated leaves. Also, the mesopliyll cells were elongated and less densely arranged. No effect was evident in the central midvein. Bostraclc and Struckmeyer (6) reported more intercellular spaces and a smaller palisade layer in treated soybean leaves.

68

Tabic l8. Effect of GA on the anatomy of Mesa-Sirsa alfalfa leaves and stems.

k

7

Pith c: ell length, mm

C011.tr

01

.32 a

.29 a

.18 a

Treated

.26 a

• l6 a

Control

.21 b

.19 a

.16 a

V I r a monts v h location followed by the same letter axe not significantly different at the .05 level according to Duncan's Multiple

Range Test.

69

Fig. 1 7 . Effect of GA on alfalfa leaf anatomy. Note the increased width and the arrangement of palisade and spongy mesophyll cells (1250 X). Upper)

Treated. Lower) Control.

70

Application of CVA definitely inriuenced raceme and flower development (Fig. -1.8) , No quantitative measurements were made, but it was evident by visual observation that GA promoted eaivl lor I:'Ioweriii.g and elongated the flower racemes. apex. iS'o differences were evident in flower color.

The effect of GA on photosynthesis, respiration, and SLW of alfalfa grown under field corulj Lions was investi­ exhibited lower va.'Laes in. all parameters over most of the were found in all characteristics. The results agree with those obtained in growth chamber studies. The photosynthetic and respiration, rates were very similar between environments except, for the first harvest in the field where higher rates were found. The high rates were probably the result of age of the leaves. Previous ed ( • is d i fficul t (0 explain upper 25 to 28 cm of the stem. At; the time of the sixth harvest, secondary Loaf development was prominent from the

Effect of GA on raceme and sepal elongation, l) Control. 2) Treated.

o

to

KEY: o = TREATED

o

* = CONTROL

to

i—i

to

UJ x

I— o

cn

CNJ

o

cn

t—

O

X

0o

LO

D

O

12

1 4 16

18

DAYS RFTER CUTOFF

22

24

_ n

Fig.

1 9 .

Effect of OA on photosynthesis (mg COo dm *" lir of alfalfa grown under field conditions.

Csl

-J-

P

? cn

K E Y : © = T R E A T E D * = C O N T R O L

_

D

O

12 i

14 i

IB

18

I

20

DRYS RFTER CUTOFF

T

22 24

- 2

Fig. 20. Effect of GA on respiration (mg COo dm hr fa]

Lions

KEY: o= TREfiTED a= CONTROL

7'J

DRYS RFTER CUTOFF

Fig.

21.

Effect of GA on .specific .Loaf weight (SLW) of alfalfa grown under fic.l d conditions.

75

The increased number of young leaves may have accounted for the increased rates.

Respiration and photosynthesis ineasuremouts compni'e favorably with values reported in the literature for alfalfa (.1.8, 51). Previous research lias shown that GA species response was noted with a decrea.se in wheat and an increase in beans. IlaJevy, Monsc.l ise, and I'.l.aut (28) showed a decrease in the di~y matter content of leaves and attributed the reduction, to increased translocation. The lower SLW may have resulted from an increased translocation in alfalfa.

Chlorosis on the treated plots was evident in the field (Fig-. 22). Chlorosis .in other species treated with

GA has been reported by several researchers (5, 6, ^J2, 66).

Reductions in chlorophyll content were found for monodifferences were evident in the chlorophyll 13 content of primary leaves with little variation in the secondary leaves (Table 19)• Ismail, Biggs, and Oberbacher (30)

[ ens ; however

.'l tivar peas and vetch, have shown a decrease .in chlorophyll content (66). A spectrophoLometric trace of a chlorophyll

Chlorosis and increased height of Mesa-Sirsa alfalfa following GA application under field conditions.

Table 19- Effect of GA on chlorophyll content of primary and secondary leaves of

Mesa-Sirsa alfalfa.

Leaf type

Treatment

Primary

Control

A mg/g F.W,

1.20 a'

1.32 a

Chlorophvll

B mg/g F.lv.

Total

Chlorophyll

.8^1 a

1.50 b

2.16 a

%

Chlorophyll

A'

80.0 a

61.1 b

Treated

Control

.30 a

80.0 a

8 6 a

1 32 a I.56 a

Values between treatments within the .05 level according to the same

Multiple Range Test.

7'6

percentage: prott:.i.n of field grown alfalfa rooty v,

7 ere measured (Table 20). The results of the field experiments agree with the growth chamber studies. A reduction in each carbohydrate fraction was evident in both harvests. The regrowth of the plants treated with GA in the first harvest was intermediate in. the acid-hydros,able carbohydrate fraction at the end of the second regrowth period. These data indicate that starch storage was delayed only for the first harvest and GA had ny influence on subsequent trans­ the treated plants.

Qualitative determinations of the free sugar extract i n d i c a t e d t h a t o n l y s u c r o s e w a s p r e s e n t ( F i g .

2 f l)

Dobrenz (.1.6) indicated that sucro.se wets the major component of the free sugars; however, glucose and fructose were present in small quantities. In the present study, sample preparation and a different c.ultivar may have accounted for the absence of glucose and fructose. Lee and Rosa

(3'0

found a reduction of starch in tobacco leaves treated with (iA

-

3 , 'l 5 that starch metabolism was affec.ted and more sucrose was present in. trc?aled corn leaves (50).

100 /-1—

'

700

Fig. 23* Effect of GA on per cent transniittance of a chlorophyll extract of Mesa-Sirsa alfalfa.

79

Table 20. Effect of GA on carbohydrate fractions and protein content of roots of field grora .Mesa-Sirsa alfalfa.

Harvest

Mav 28

Treatment

Treated

Control

% of control

Carbohydrate fractions, % ethanol

9

!

i a

:

11.1 a

8^.9

"2-50/,

6.0 b

18.9 a

31-7

Protein l^i.5 a

13.9 a

104

.8

June 22 Control

Regrowth

0' of control

9-5 b

13-6 a

13-9 a

k.7

c

11.0 a

7.9 b

ZLO

i

a

9-5 a

9-5 a

109-6

'Values between treatments for each parameter followed by the same letter are not significantly different at the .05 level according to Duncan's Nultiple

Range Test.

8i

Fig.

2k.

Photograph showing the separation of free sugars by thin layer chromatography. Standards were prepared at a concentration of 2 mg/ml. Maltose was spotted with 10 and 25 [il , respectively. Sucrose (S) and fructose (F) were spotted with 25 JJ,1 and the unknown was spotted respectively.

82

The datct of the field experiment indicate that the water requirement of alfalfa can be lowered by increasing dry forage production. Under field conditions, GA increased the total forage produced when applied as an root reserves were reduced and regrowth was lower on the subsequent harvest. Therefore, the application of GA oil a practical basis is not

SUMMARY were used to evaluate the offact of various growth regula­ i

1 s Iran

-UH

e efficiency lathhou.se, growth chamber, and field environments.

Water-use efficiency values were significantly lower when plants were sprayed with an aqueous solution of regulator or antitranspirant chemicals were applied no sign.i

r.i

.caut effec t was found on water requirement in a greenhouse environment. The water requirement of alfalfa was increased when plants were sprayed with PMA and CCC in. a lathhouse environment.

Gibberellie acid increased total forage production stem-petiole production with essentially no change in leaflet production. However, in some experiments secondary brandling was increased by GA and this resulted in an increased amount of leaflet tissues. in pi.th cell length, .'leaf thickness, i.nternodo length, stem

A 3

height, ,'ind .rate of stem elonga

f o u n d

on plants

8'i

The effect

o f

GA on

l;raTiP|):i

rati was mediated

b y

transpiration rates were significantly increased, Two alfalfa genotypes responded differently to GA treatment.

Photosynthesis (nig C0 r dm " ar ' ) was I ower for plants treated with GA when .grown under growth chamber and field were expressed on a leaf weight: basis, variable results were found depending on the time of measurenient after cutoff. field conditions. The yellowing was primarily caused by a reduction in the chlorophyll 1! content, of primary leaves.

Also, all fractions of the chlorophyll extract were lowered in both primary and secondary leaves.

Plants treated with GA had a .1 owor percentage of

This effect was found in both greenhouse and field environ­ i :i. v e effect was found on the free sugars r s x r

85

Percentage protein of the roots showed a slight inc.rea.se when the plants were sprayed with GA. However, no effect on protein percentage was evident in the above ground forage when the plants were treated with GA.

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73.. Yeli, Yu-Tsai. 1967* Ef a vitamin B mixture on the vegetative growth and

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