’ mm er ABSCTSSTON or FLOWERS . A ~ ‘ ANDFRLBITS 05FPHASEDLUSEVULGARBL? .- Dissertation for the Degree of Ph DU . 1 . MTCHTGAN STATE UNTVERSTTY SURANANT SUBHADWANDHU A " 1976 ’ lllllllllllllllllllllllllllfillflllfllllflllllllfllllll This is to certify that the thesis entitled CONTROL OF ABSCISSION OF FLOWERS AND FRUITS OF PHASEOLUS VULGARIS L. presented by Suranant Subhadrabandhu has been accepted towards fulfillment of the requirements for Ph.D. Mgmenr Department of Crop and Soil Sciences Major professor DatEZZzzz/m’i ”7% 0-7639 L; i:- #43" ; wall?‘ MSU RETURNING MATERIALS: Place in book drop to LIBRARIES remove this checkout from “ your record. FINES will be charged if book is returned after the date stamped below. il‘lll‘ll-IIIL} \n‘ 2 two "dry l Turtle S< “Seafare: house an‘ differen tern. " Produced abscissi ferences Signifi( Synthe 5; me“ am hOUSe it deereats resDons ,A‘a 1.. I 5 /zx2 £?€7l?” ABSTRACT CONTROL OF ABSCISSION OF FLOWERS AND FRUITS OF PHASEOLUS VULGARIS L. BY Suranant Subhadrabandhu Abscission of flowers and fruits was studied in two dry bean (Phaseolus vulgaris L.) cultivars, "Black Turtle Soup," an indeterminate, semi—vine type, and "Seafarer,“ a determinate bush type. Under normal green- house and field conditions, these two cultivars exhibited differences in percent pod abscission and flowering pat- tern. "Black Turtle Soup" had a longer flowering period, produced fewer flowers and exhibited less flower and pods abscission than "Seafarer." In spite of the above dif- ferences, seed yields from the two cultivars were not significantly different. Environmental conditions favorable for photo— synthesis, such as long days and carbon dioxide enrich- ment applied during the reproductive phase in the green— house increased vegetative growth and leaf area, and decreased pod abscission. "Black Turtle Soup" was more responsive than "Seafarer." Long vegetative g! and starch ir abscission. "Bla< starch in veg ticularly in and starch i1 Bean potential we: decreasing c1 probabilitie between pod grows withi abscisic aci were determi PEdicel, usi trealtments a dihYdrOphaSe and dihydrop "Seafarer" t with high at contain high data obtains acid and its sion of dry Suranant Subhadrabandhu Long days and carbon dioxide enrichment promoted vegetative growth and seed yield, increased free sugar and starch in the vegetative parts, and reduced pod abscission. "Black Turtle Soup" contained more sugar and starch in vegetative tissues than did "Seafarer," par— ticularly in stem and leaf. The levels of free sugar and starch in seeds were similar in the two cultivars. Bean populations having a low or high abscission potential were established by either increasing or decreasing competition between flowers. Abscission probabilities based on a predetermined relationship between pod size and abscission were assigned to sub— groups within each population. Levels of endogenous abscisic acid, phaseic acid and dihydrophaseic acid were determined in methanol extracts of both pod and pedicel, using gas liquid chromatography. None of the treatments affected abscisic acid, phaseic acid or dihydrophaseic acid level in pedicels. Abscisic acid and dihydrophaseic acid levels in pods were higher in "Seafarer" than in "Black Turtle Soup." Populations with high abscission potential from both cultivars also contain higher abscisic acid levels in the pod. The data obtained here cannot explain the role of abscisic acid and its related compounds in flower and pod abscis— sion of dry bean. in CONTROL OF ABSCISSION OF FLOWERS AND FRUITS OF PHASEOLUS VULGARIS L. BY Suranant Subhadrabandhu A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Crop and Soil Sciences 1976 DEDICATION To my parents, wife and sons. ii I wis? gratitude to and Dr. F. G. valuable advi course of thi criticism of I am experience 0: Dr. D. Penne: A gr Hanover Who thank Dr, D. Served 011 th Study, Than fifld assist and encomag kindly assis I w encourageme] Studyl Sin her SaCr-lfi ACKNOWLEDGMENTS I wish foremost to express my sincere thanks and gratitude to my advisers, Dr. M. W. Adams, Dr. D. Penner, and Dr. F. G. Dennis Jr., for their encouragement, valuable advice, guidance and interest throughout the course of this investigation and for their constructive criticism of this manuscript during its preparation. I am most honored and grateful to have had the experience of working in both Dr. F. G. Dennis‘ and Dr. D. Penner's laboratories. A grateful acknowledgment is extended to Dr. J. W. Hanover who served on the guidance committee. I wish to thank Dr. D. A. Reicosky and Dr. E. A. Mielke who also served on the guidance committee in some parts of this 'study. Thanks are also extended to Mr. J. L. Taylor for field assistance and to Dr. J. V. Wiersma for suggestions and encouragement. Special thanks to my Thai friends who kindly assisted in field planting in 1974. I would like to thank my father for his kind encouragement and endless support during my graduate study. Sincere thanks to my loving wife, Pannee, for her sacrifices, understanding, and encouragement especially in this study am of this manus thanks for th Apinya, for a Lastl support grant out my stay i especially in time of frustration during the course of this study and also to her valuable help in preparation of this manuscript. To my sons, Dhanant and Dhanat, many thanks for their unsuspecting sacrifices and to my sister, Apinya, for assisting in preparation of this manuscript. Lastly, I wish to acknowledge the financial support granted me by the Rockefeller Foundation through- out my stay in America. iv LIST OF TABLI LIST OF FIGU INTRODUCTION CHAPTER 1: Introduct Genetics Absciss Types of Factors ( Absciss Envirc Lic_ Phc Ter Ca] Rel So: Inten CarbOhYd: Carbohyd Extra Analy Role of Role of REFERENCES. TABLE OF CONTENTS LIST OF TABLES . . . . LIST OF FIGURES . . . INTRODUCTION . . . . CHAPTER 1: LITERATURE REVIEW . . Introduction . . . . . Genetics Control of Reproductive Structure Abscission . . . . . . Types of Abscission. . . . . . Factors Controlling Reproductive Structures Abscission . . . . . . . . . Environmental Factors . . . . . . . Light intensity . . . . . . . . Photoperiod . . . . . Temperature . . . . . Carbon dioxide . . . . . Relative humidity . . . . . Soil moisture stress . . . . Internal Factors. . . . . . Carbohydrate Availability. . . . Carbohydrate Determination . . . Extraction. . . . . . . Analysis . . . . . . Role of Carbohydrates in Abscission Role of Abscisic Acid (ABA) in Abscission REFERENCES. u o u a a o c n n 9 . Page l4 l6 l6 l7 l9 CHAPTER 2: Abstract. Introduct Materials Greent Field Results . Greeni Field DiSCUSSi( REFERENCES CHAPTER 3: Abstract Introduc Material Results Pod s Leaf Plant Seed REFERENCES CHAPTER 4 : IntrOdu Page CHAPTER 2: ABSCISSION OF FLOWERS AND FRUITS IN PHA— SEOLUS VULGARIS L. I. VARIETAL DIFFER- ENCE IN FLOWERING PATTERN AND ABSCISSION . 31 Abstract. . . . . . . . . . . . . . . 31 Introduction . . . . . . . . . . . . . 32 Materials and Methods . . . . . . . . . . 33 Greenhouse Experiment . . . . . . . . . 33 Field Experiment . . . . . . . . . . . 33 Results . . . . . . . . . . . . . . . 34 Greenhouse Experiment . . . . . . . . . 34 Field Experiment . . . . . . . . . . . 36 Discussion . . . . . . . . . . . . . . 39 REFERENCES . . . . . . . . . . . . . . . 47 CHAPTER 3: ABSCISSION OF FLOWERS AND FRUITS IN PHA- SEOLUS VULGARIS L. II. GROWTH AND POD ABSCISSION AS AFFECTED BY DIFFERENT DAYLENGTHS . . . . . . . . . . . 49 Abstract. . . . . . . . . . . . . . . 49 Introduction . . . . . . . . . . . . . 50 Materials and Methods . . . . . . . . . . 51 Results and Discussion . . . . . . . . . . 53 Pod Abscission. . . . . . . . . . . . 53 Leaf Development . . . . . . . . . . . 58 Plant Development. . . . . . . . . . . 58 Seed Yield . . . . . . . . . . . . . 60 REFERENCES . . . . . . . . . . . . . . . 64 CHAPTER 4: ABSCISSION OF FLOWERS AND FRUITS IN PHA— SEOLUS VULGARIS L. III. RELATIONSHIP OF POD ABSCISSION TO DIFFERENTIAL LEVELS OF CARBOHYDRATES PRODUCED BY VARIATION IN DAYLENGTH . . . . . . . . . . 66 Abstract. . . . . . . . . . . . . . . 66 Introduction . . . . . . . . . . . . . 68 vi Materials Sample Determ Determ hydr Results a Free 5 Starct Relati Avai REFERENCES CHAPTER 5 : Abstract Introduc Material Results Pod A Leaf Plant Seed REFERENCES CHAPTER 6: AbStrac Introdu Materia Samp Materials and Methods . . . . . . . . Sample Preparation . . . . . . . Determination of Free Sugars. . . Determination of Total Nonstructural Carbo- hydrates (TNC). . . . . . . . . . Results and Discussion. . . . . . . . . Free Sugar. . . . . . . . . . . . Starch . . . Relationship of Pod Abscission to Levels of Available Carbohydrates. . . . . . . REFERENCES . . . . . . . . . . . . . CHAPTER 5: ABSCISSION OF FLOWERS AND FRUITS IN PHA- SEOLUS VULGARIS L. IV. GROWTH AND POD ABSCISSION AS AFFECTED BY CARBON DIOXIDE LEVELS . . . . . . . Abstract . . . . . . . . . . . . . Introduction . . . . . . . . . . Materials and Methods . . . . . . . . . Results and Discussion. . . . . . . . . Pod Abscission . . . . . . . . . . Leaf Development. . . . . . . . . . Plant Development . . . . . . . . . Seed Yield. . . . . . . . . . . . REFERENCES . . . . . . . . . . . . . CHAPTER 6: ABSCISSION OF FLOWERS AND FRUITS IN PHA- SEOLUS VULGARIS L. V. RELATIONSHIP OF POD ABSCISSION TO DIFFERENTIAL LEVELS OF CARBOHYDRATES PRODUCED BY VARIATION IN CARBON DIOXIDE CONCENTRATION. . . Abstract . . . . . . . . . . . . . Introduction . . . . . . . . . . Materials and Methods . . . . . . . . . Sample Preparation . . . . . . . . . Page 68 68 69 70 71 71 79 86 89 91 91 92 93 93 101 104 110 111 111 113 113 113 Results a Free E Starct Relati Cart REFERENCES . CHAPTER 7: Abstract Introduc Material Plant Extra Fract Analy Results Pod G Hormo AE PA DE Discussj REFERENCES CHAPTER 3: APPENDIcrs Appendix A- caox F] Results and Discussion . . . . Free Sugar . . . . . . . . . . . . Starch . . . . Relation of Pod Abscission to Available Carbohydrates . . . . . . . . . REFERENCES . . . . . . . . . . . . . . CHAPTER 7: ABSCISSION OF FLOWERS AND FRUITS IN PHA- SEOLUS VULGARIS L. VI. THE RELATIONSHIP BETWEEN POD ABSCISSION AND ENDOGENOUS ABSCISIC, PHASEIC, AND DIHYDROPHASEIC ACIDS IN THE PEDICELS AND FRUITS. . . Abstract. . . . . . . . . . . . . Introduction . . . . . . . . . . Materials and Methods . . . . . . . . . Plant Culture . . . . . . . . . . . Extraction . . . . . . . . . . . . Fractionation . . . . . . . . . . . Analysis. . . . . . . . . . . . . Results . . . . . . . . . . . . . . Pod Growth vs. Abscission . . . . . . . Hormone Content vs. Absc1551on . . . . ABA . . . . . . . . . . . . . PA . . . . . . . . . . . . . DPA . . . . . . . . . . . . . Discussion . . . . . . . . . . . . . REFERENCES CHAPTER 8: SUMMARY AND CONCLUSIONS. . . . . APPENDICES Appendix A. GROWTH AND POD ABSCISSION AS AFFECTED BY DIF- FERENT DAYLENGTHS. . . . . . . . viii Page 114 114 117 125 130 131 131 133 134 134 135 136 136 137 137 139 139 139 139 139 143 145 147 Appendix B. RELATI LEV] TIOl C. GROWT] CAR‘ D. RELAT LEV TIO SELECTED BIB Appendix Page B. RELATIONSHIP OF POD ABSCISSION T0 DIFFERENTIAL LEVELS OF CARBOHYDRATES PRODUCED BY VARIA- TION IN DAYLENGTH . . . . . . . . 153 C. GROWTH AND POD ABSCISSION AS AFFECTED BY CARBON DIOXIDE LEVELS. . . . . . . . 159 D. RELATIONSHIP OF POD ABSCISSION TO DIFFERENTIAL LEVELS OF CARBOHYDRATES PRODUCED BY VARIA- TION IN CARBON DIOXIDE CONCENTRATION . . . 165 SELECTED BIBLIOGRAPHY . . . . . . . . . . . 171 ix l l CHAPTER 2 l. Effec the 2. Mean Flc ves Abs CHAPTER 3 LIST OF TABLES CHAPTER 2 Page 1. Effects of Cultivar on Yield Components in the Greenhouse . . . . . . . . . . 35 2. Mean Values per Space-planted Plants of Flowers Produced, Pods Retained at Har- vest and Percentage of Flower and Pod Abscission . . . . . . . . . . . 40 CHAPTER 3 1. Effects of Daylengths and Harvesting Time on Number of Flowers, Number of Pods, and Percentage of Pod Abscission of Two Dry Bean Cultivars Grown Under Greenhouse Con— ditions in 1975 and 1976 . . . . . . 54 2. Correlation Coefficients Between Percentage of Pod Abscission or Leaf Area and Other Parameters in Two Dry Bean Cultivars Sub- jected to Different Daylength Treatments After Flowering. . . . . . . . . 57 3. Effects of Daylengths, Harvesting Times and Cultivars on Leaf Weight Per Plant, Leaf Area Per Plant and Number of Trifoliate Leaves Per Plant Grown Under Greenhouse Conditions in the Year 1975 and 1976. . . 59 4. Effects of Daylengths, Harvesting Times and Cultivars on the weight Per Plant of Root, Stem and Total Plant Grown Under Green— house Conditions in the Year 1975 and 1976 . . . . . . . . . . . . . 61 5. Effects of Daylength on Number of Seeds Per Plant, Total Seed Weight Per Plant and Weight Per Seed in Two Dry Bean Cultivars Grown in 1975 and 1976 Seasons. . . . . 62 amFTER 4 1. Devel Eff Pla 2. Effec Fre 3. Effec Sup 4. Effec on Ti: co m "h Ph (D CHAPTER 5 1' Stat L1 Page CHAPTER 4 1. Developmental Stages, Cultivars and Daylength Effects on Soluble Sugar Level in Various Plant Parts . . . . . . . 72 Effects of Cultivar and Time of Sampling on Free Sugar Concentrations in Bean Tissues . 74 2. 3. Effects of Photoperiod and Cultivar on Free Sugar Concentration in Bean Tissues . . . 75 Effects of Photoperiod and Time of Sampling on Free Sugar Concentration of Bean Tissues . . . . 77 Developmental Stages, Cultivars and Daylength Effects on Starch Level in Various Plant Parts . . . . . . . . 80 Effects of Photoperiod and Cultivar on Starch Concentration in Bean Tissues. 4. o o o a o o n 5. 6. . . 81 Effects of Cultivar and Time of Sampling on Starch Concentration in Bean Tissues. . . 83 Effects of Photoperiod and Time of Sampling on Starch Concentration of Bean Tissues. 7. 8. 9. Correlation Coefficients Between Percentage of Pod Abscission and Available Carbohy— drate in the Vegetative Tissues of the Two Drybean (Phaseolus vulgaris L.) Cultivars Grown Under 3 Daylengths. . . . . . . 88 CHAPTER 5 1. Stages of Pod Development and Carbon Dioxide Levels Effect on Number of Flowers, Number of Pods and Percentage of Abscission in Two Dry Bean Cultivars Grown Under the Two Seasons ' o o o a o u I o . . 94 Effects of Carbon Dioxide Levels on Number of Flowers, Number of Pods Retained, and Per— centage of Pod Abscission in Two Dry Bean Cultivars Grown Under the Two Seasons . . 95 2. xi 3. Effect Weig Plar Grow 4. Effect Area and Cul‘ 5. Stage ide Lea Cul 6. Corre of act jec Aft \l Effec of P12 Bee co Corre of Che je< Afr CHAPTER 6 3. Effects of Carbon Dioxide Levels on Dry Weight Per Plant of Root, Stem and Total Plant Weight in Two Dry Bean Cultivars Grown Under the Two Seasons . . . . 4. Effects of Carbon Dioxide Levels on Leaf Area Per Plant, Number of Leaf Per Plant and Leaf Weight Per Plant in Two Dry Bean Cultivars Grown Under the Two Seasons. . 5. Stages of Pod Development and Carbon Diox- ide Levels Effect on Number of Leaf and Leaf Area Per Plant in Two Dry Bean Cultivars Grown Under the Two Seasons. . 6. Correlation Coefficients Between Percentage of Pod Abscission and Other Growth Char— acters in Two Dry Bean Cultivars Sub- jected to Different Carbon Dioxide Levels After Flowering . . . . . . . . . 7. Effects of Carbon Dioxide Levels on Number of Seeds Per Plant, Seed Weight Per Plant and Weight of One Seed in Two Dry Bean Cultivars Grown Under Two Seasons 8. Correlation Coefficients Between Percentage of Pod Abscission and Other Reproductive Characters in Two Dry Bean Cultivars Sub— jected to Different Carbon Dioxide Levels After Flowering . . . . . . . . . CHAPTER 6 l. The Effects of Developmental Stage and Carbon Dioxide Levels on Free Sugar Concentration in Various Plant Parts of the Two Bean Cultivars. . . . . . 2. Effects of Carbon Dioxide and Time of Sampling on Free Sugar Concentration of Bean Tissues . . . . . . . . . 3. Effects of Developmental Stages and Carbon Dioxide Levels on Starch Concentration in Various Plant Parts of the Two Dry Bean Cultivars . . . . . . . . . 4. Effects of Carbon Dioxide and Cultivar on Starch Concentration in Bean Tissues . . xii Page 96 97 100 102 105 106 115 119 121 APPENDIX A A-l. Effl N m 0 G 1H- Eff Page 5. Effects of Carbon Dioxide and Time of Sampling on Starch Concentration of Bean Tissues . . . . . . . . . . . 124 6. Correlation Coefficients Between Percentage of Pod Abscission and Available Carbohy- drate Fractions in Vegetative Tissues in Two Dry Bean Cultivars Under Two Levels of Carbon Dioxide . . . . . . . . . 126 7. Correlation Coefficients Between Seed Weight Per Plant and Available Carbohydrate Fractions in Vegetative Tissues in Two Dry Bean Cultivars Under Two Levels of Carbon Dioxide. . . . . . . . . . . . Correlation Coefficients Between Stem Weight Per Plant and Available Carbohydrate Fractions in Vegetative Tissues in Two Dry Bean Cultivars Under Two Levels of Carbon Dioxide . . . . . . . . . . CO 0 128 CHAPTER 7 1. Levels of ABA, PA and DPA in Relation to Per— centage of Abscission of the Two Bean Cultivars . . . . . . . . . . . . 140 APPENDIX A A—l. Effects of Daylengths on Number of Flowers, Number of Pods and Percentage of Pod Abscission at 3 Stages of Development of Two Dry Bean Cultivars Grown Under Greenhouse Conditions in 1975 . . . . . 147 A-Z. Effects of Daylengths on Number of Flowers, Number of Pods and Percentage of Pod Abscission at 3 Stages of Development of Two Dry Bean Cultivars Grown Under Greenhouse Conditions in 1976 . . . . . 148 A-3. Effects of Daylengths on Leaf Area Per Plant, Number of Leaf Per Plant and Leaf Weight Per Plant at 3 Stages of Development of Two Dry Bean Cultivars Grown Under Green- house Conditions in 1975 . . . . . . . 149 xiii .—\ ,7 Page A—4. Effects of Daylengths on Leaf Area Per Plant, Number of Leaf Per Plant and Leaf Weight Per Plant at 3 Stages of Development of Two Dry Bean Cultivars Grown Under Green- house Conditions in 1976 . . . . . . . 150 A—5. Effects of Daylengths Effects on Root Weight Per Plant, Stem Weight Per Plant and Total Plant Weight at 3 Stages of Development of Two Dry Bean Cultivars Grown Under Green— house Conditions in 1975 . . . . . . . 151 A—6. Effects of Daylengths on Root Weight Per Plant, Stem Weight Per Plant and Total Plant Weight at 3 Stages of Development of Two Dry Bean Cultivars Grown Under Greenhouse Conditions in 1976 . . . . . 152 APPENDIX B B—l. Effects of Developmental Stages and Daylength on Free Sugar Levels in Vegetative Tissues of Two Phaseolus vulgaris L. Cultivars . . 153 3-2. Effects of Developmental Stages and Daylength on Free Sugar Levels in Reproductive Tissues of Two Phaseolus vulgaris L. . . . 154 3-3. Effects of Developmental Stages and Daylength on Starch Levels in Vegetative Tissues of Two Phaseolus vulgaris L. Cultivars . . . 155 B-4. Effects of Developmental Stages and Daylength on Starch Levels in Reproductive Tissues of Two Phaseolus vulgaris L. Cultivars . . . 156 B—S. Effects of Developmental Stages and Daylength on Total Nonstructural Carbohydrate Levels in Vegetative Tissues of Two Phaseolus vul— garis L. Cultivars . . . . . . . _T- . 157 B-6. Developmental Stages and Daylength Effects on Total Nonstructural Carbohydrate Levels in Reproductive Tissues of Two Phaseolus vul- garis L. Cultivars . . . . . . .——T . 158 APPENDIX C (3-1. Effec Flo Pod of C-2. Effec Flc Poc' of C-3. Effec Wei am De‘ Gr( APPENDIX D ”‘1. Em C. C1 Page APPENDIX C C—l. Effects of Carbon Dioxide Levels on Number of Flowers, Number of Pods and Percentage of Pod Abscission at 3 Stages of Development of Two Dry Bean Cultivars Grown in 1975 . . 159 C-2. Effects of Carbon Dioxide Levels on Number of Flowers, Number of Pods and Percentage of Pod Abscission at 3 Stages of Development of Two Dry Bean Cultivars Grown in 1976 . . 160 C-3. Effects of Carbon Dioxide Levels on Root Weight Per Plant, Stem Weight Per Plant and Total Plant Weight at 3 Stages of Development of Two Dry Bean Cultivars Grown in 1975. . . . . . . . . . . 161 C—4. Effect of Carbon Dioxide Levels on Root Weight Per Plant, Stem Weight Per Plant and Total Plant Weight at 3 Stages of Development of Two Dry Bean Cultivars Grown in 1976. . . . . . . . . . . 162 C—5. Effects of Carbon Dioxide Levels on Leaf Area Per Plant, Number of Leaf Per Plant and Leaf Weight Per Plant at 3 Stages of Development of Two Dry Bean Cultivars Grown in 1975. . . . . . . . . . . 163 C-6. Effects of Carbon Dioxide Levels on Leaf Area Per Plant, Number of Leaf Per Plant and Leaf Weight Per Plant at 3 Stages of Development of Two Dry Bean Cultivars Grown in 1976. . . . . . . . . . . 164 APPENDIX D D-l. Effects of Stages of Pod Development and Carbon Dioxide Levels on Free Sugar Con- centration in Root, Stem and Leaf of the Two Dry Bean Cultivars. . . . . . . . 165 0-2. Effects of Stages of Pod Development and Carbon Dioxide Levels on Free Sugar Con— centration in Seed and Pod Wall of the Two Dry Bean Cultivars . . . . . . . . . 166 XV Effec Twc Effects of Stages of Pod Development and Carbon Dioxide Levels on Starch Concen- tration in Root, Stem and Leaf of the Two Dry Bean Cultivars . . . . . . Effects of Stages of Pod Development and Carbon Dioxide Levels on Starch Concen- tration in Seed and Pod Wall of the Two Dry Bean Cultivars . . . . . . . Effects of Stages of Pod Development and Carbon Dioxide Levels on Total Non- structural Carbohydrate Concentration in Root, Stem and Leaf of the Two Dry Bean Cultivars. . . . . . . . . Effects of Stages of Pod Development and Carbon Dioxide Levels on Total Non- structural Carbohydrate Concentration in Seed and Pod Wall of the Two Dry Bean Cultivars . . . . . . . . . . xvi Page 167 168 169 170 CHAPTER 2 1. Flow 6. P06 1 CHAPTER 3 1- In CHAPTER 1 LIST OF FIGURES CHAPTER 2 1. Flower production in a specific day as a percentage of total flowers produced under greenhouse conditions . . . . . . 2. Pods retained from flowers borne on a spe— cific day, as a percentage of total pods at harvest grown under greenhouse conditions . 3. Pods retained per day as a percentage of flowers produced on that day. . . . . . 4. Flower production in a specific day as a percentage of total flowers produced under field conditions . . . . . . . . . 5. Pod retained from flowers borne on a specific day, as a percentage of total pods at har— vest grown under field conditions . . . 6. Pods retained per day as a percentage of flowers produced on that day. . . . . . CHAPTER 3 1. Interaction between developmental stages and daylengths on percentage of pod absc1SSion (A), and total plant weight (B). . . . . CHAPTER 6 1. Levels of starch in A. root; and B. stem; of two Phaseolus vulgaris L. cultivars during their reproductive phase, averaged from the two carbon dioxide levels . . . . . 2. Levels of starch in seed of two Phaseolus vul aris L. cultivars during their repro— ductive phase, averaged from the two carbon dioxide levels . . . . . . . . . xvii Page 37 38 41 42 43 46 55 116 123 CHAPTER 7 1. Growt poé CHAPTER 7 Page 1. Growth curves of abscising and persisting pods A. Black Turtle Soup; B. Seafarer . . 138 xviii i w » Absc characterist excessive m (We: limiting yi' pods the fa‘ understood. by the leve and/0r prot The hYPOtheses is control] is Control] INTRODUCTION Abscission of flowers and immature fruits is characteristic of many economic plants, which produce . l excessive numbers of flowers, including dry beans { (Phaseolus vulgaris L.), and may be an important factor limiting yield. To prevent abscission of flowers and pods the factors controlling their abscission must be understood. Abscission may be regulated by hormones or by the level of nutrients available, chiefly carbohydrates and/or proteins. The objectives of this study were to test two hypotheses concerning abscission, namely (a) abscission is controlled by carbohydrate level vs. (b) abscission is controlled by abscisic acid level. Ab51 part of an . plant. In identified stalk which cells. An this zone, the Organs. Stages in 1 traumatic < and it may Some chemi. uSually as abscission searched f in this ph SyntheSiZe The indu C t CHAPTER 1 LITERATURE REVIEW Introduction Abscission is the process by which an organ, or part of an organ, separates from the main body of the plant. In fruits and leaves an abscission zone can be identified at the base of the organ or its supporting stalk which is characterized by smaller, less lignified cells. An abscission layer usually develops through this zone, which eventually brings about separation of the organs. In nature abscission occurs at defined stages in the life of a deciduous organ or following traumatic or accidental interruptions of its development, and it may be influenced by environmental changes. Also, some chemical message, sent to the abscission zone, is usually assumed to be responsible for the regulation of abscission layer formation. Physiologists have long searched for evidence of involvement of plant hormones in this phenomenon. These messengers are presumed to be synthesized outside of the abscission zone itself (82). The induction of these hormonal changes is believed to be controlle internal one plant parts The that of leai mechanisms first based (55), the St mones are p blade, and sion, analo Ana growth regu for the coy This shoulc' 0f the fruj angia whicl Also, they Correlativ. De fruit absc For eXampl with Persi In Some in °CCurs 0n] develop a be controlled either by environmental factors or by internal ones, such as competition between different plant parts (82). The physiology of fruit abscission parallels that of leaf abscission, suggesting similar regulatory mechanisms (55). Two arguments support such a hypothesis, first based on the presumed homology of the two organs (55), the second on analogies in their behavior. Hor— mones are produced in both the fruit and in the leaf blade, and injury to a fruit may result in rapid abscis— sion, analogous to that observed on deblading. Analyses of hormone levels and responses to growth regulators suggest that a simple, direct mechanism for the control of fruit abscission is unlikely (85). This should not be surprising in view of the complexity of the fruit. Unlike leaves, fruits enclose megaspor- angia which have a complex development of their own. Also, they are heterotrophic and therefore more prone to correlative control. Despite the proposed analogy between leaf and fruit abscission (55) several differences are noteworthy. For example, immaturity and active growth are associated with persistence in leaves, but with abscission in fruit. In some instances (e.g., avocado, tomato), abscission occurs only in young fruit; the mature fruit does not develop a complete abscission layer. Sinc (5,6,18, 5 abscission c EVil grouped inti sion (23, l are often d such as ear same thing This is evi duced varie Evi time of f1( (23). In a vars, comp; in F1' and late flOWe generation in Snap be flOWering the case. (early flc fwiring) (24). In Since many reviews have dealt with leaf abscission (5, 6, 18, 55, 56, 90), this review will be limited to abscission of reproductive structures. Genetics Control of Reproductive Structure Abscission Evidence for genes control of abscission can be grouped into two parts flowering time and rate of abscis- sion (23, 107). The blossoms of early flowering lines are often damaged by adverse environmental conditions such as early spring frost, and abscise prematurely. The same thing happens in the very late flowering varieties. This is evident in some fruit trees, and certain intro— duced varieties of field crops. Evidence for the existence of genes controlling time of flowering was obtained for Phaseolus vulgaris L. (23). In a cross between early and late flowering culti- vars, complete dominance for early flowering was observed in F1’ and a good fit to 3:1 and 1:1 ratios of early to late flowering plants was observed in F2 and in P2 x Fl generations respectively. Similar results were reported in snap beans, and the dominant gene controlled the early flowering character (28). However, this is not always the case. In the cross of White Seeded Tendergreen (early flowering) x Bush Blue Lake OSC 949-1864 (late flowering), the late flowering character was dominant (24). In the cross of G.N. 1140 (early flowering) x Nebraska #1 flowering i: being domin of more the flowering. tropical or (79) found backcross 1 time was qt most of the time exhibi Thus genes among vari: trolling e habitats ( daylength, 0f floweri Ge reProdueti Early WOrk in the Per aPple Varj Same Orcha detemline< Persentag‘ garden be‘ Nebraska #1 selection (late flowering), the time of flowering is controlled by two major genes, with earliness being dominant to lateness. This indicates involvement of more than one locus for the gene expressing time of flowering. In Goiano and Mexico 450, bean cultivars of tropical origin which are daylength insensitive, Ortega (79) found continuous variation of flowering time in F2, backcross l and backcross 2, suggesting that flowering time was quantitatively inherited. He concluded that most of the genes involved in the control of flowering time exhibited additive effects and lack of dominance. Thus genes controlling time of flowering appear to differ among varieties. Daylength plays a major role in con— trolling earliness and in adaptation of cultivars to new habitats (36). Therefore, environment, and especially daylength, may interact with genes in the control of time of flowering. Genes may control the rate of abscission of reproductive structures, as well as time of flowering. Early work of Heinicke (50) showed marked differences in the percentage of immature fruit abscission in three apple varieties. Since the trees were growing in the Same orchard, the rate of fruit drop must have been determined genetically. Cowpea varieties differ in percentage of aborted ovules (75). Soybean (107) and garden bean (13) varieties exhibit different rates of blossom and correlation vs. yield E vs. yield p Un< ductive st: ing events (1) La me is (2) Fa us ma hi (3) Ir 0) blossom and pod drop. In the latter species negative correlations between total number of blossoms per plant vs. yield per plant, and percentage blossom and pod drop vs. yield per plant were reported (13). Types of Abscission Under natural conditions, the abscission of repro— ductive structures ensues when one or more of the follow- ing events occurs. (1) Lack of pollination due to unfavorable environ— mental conditions or absence of insects, which is followed by abscission of the flower; (2) Failure of the pollen tube to reach the ovule usually results in the flower abscission. This may be due to genetically controlled incompati- bility between the pollen tube and the style. (3) In some species, fertilization occurs and the ovule is formed; however, during fruit develop— ment the ovule ceases growth and abscission of : the young fruit follows. In soybeans, pod abscission was found to occur during the early stages of embryo development, 3 to 7 days after anthesis (59). Competition for carbohydrates, mineral nutrients, and growth regulators may be responsible for this type of abscission. (4) Fru mat thi OCC Environment The responsive temperatun Li and photOp The carboh Utilized d environmgn overall gr is less 1i PhotosYntp absCissior increased are reduCE bean Flam deciduOuS greater 01 (4) Fruit maturation. Abscission of fruit at maturity is common in some fruits, however, this type of abscission does not commonly occur in field crops. Factors Controlling Reproductive Structures Abscission Environmental Factors The abscission of reproductive structures is very responsive to environmental factors, including light, temperature, C02, relative humidity, and moisture stress. Light intensity. Both photosynthetic effects and photoperiodic effects of light influence abscission. The carbohydrates resulting from photosynthesis are utilized directly for deposition of cell walls. When environmental factors favor photosynthesis but restrict overall growth, cell walls are thicker and abscission is less likely to occur (9). The opposite is true when photosynthesis is limited. Cell walls are thinner and abscission rates are higher. Cotton boll drop is increased from 46 to 86% by shading (30). Pea yields are reduced 50% under 50% shade (71). Shading of soy— bean plants increases the abscission of pods (69). In deciduous fruit trees abscission of young fruit is greater on twigs deficient in carbohydrate or with few leaves (19). P113: long days ir of three Set and in subse they showed days at abor happened rel or low (78) of flower a nation on t tary (52). Var high levels (9, 127, 1; With decrea initiation regard to , leads to a buds (9) . Stmng sin buds alter Zones of t Vernal 19E '3 high tempq soybean ( Photoperiod. Ojehohon et a1. (77) reported that long days induce abscission of flower buds on the main axis of three South American cultivars of Phaseolus vulgaris L., and in subsequent experiments with one of these cultivars they showed that the buds began to fail to develop in long days at about the stage when meiosis occurred. This happened regardless of whether light intensity were high or low (78). Long photoperiods also increase the percentage of flower and pod abscission in soybeans (60, 106). Infor— mation on the physiology of the response is only fragmen- tary (52). Various reports indicate that long days favor high levels of auxins, gibberellins and abscisic acid (9, 127, 128). Hormonal changes in leaves associated with decreasing day length could be one factor in the initiation of leaf abscission in the fall (9). With regard to vernal leaf abscission, increasing daylength leads to an upsurge of hormone synthesis, especially in buds (9). Consequently, buds and developing shoots became strong sinks, and the auxin moving downward from the buds altered the auxin gradient across the abscission zones of the old leaves. This would serve to promote vernal leaf abscission. Temperature. Under natural growing conditions, high temperature increases flower and pod abscission in soybean (106), temperatures above 40°C being especially effective ( is due to l photosynthe ature (40). abscission temperature In young cr period of V buds, flow with periol processes . Such adver high tempe abscission g duction ha of greenhc increased enriched a cmicentrm Storage C; tillers 1] whereas 1] increased grain in di0xide e effective (69). Cessation of pod growth at 40°C possibly is due to lowered rates of photosynthesis, since net photosynthesis of soybeans is very low at this temper— ature (40). In lima bean, the daily rate of blossom abscission was positively correlated with the maximum temperature and possibly the attendant low humidity (22). In young cotton fruits, abscission increased during the period of warm nights (30°C) (43). Abscission of flower buds, flowers and young fruits is frequently correlated with periods of hot weather (118). Various metabolic processes are adversely affected by excessive heat (104). Such adverse metabolic effects probably mediate the high temperature induction of flower and young fruit abscission. Carbon dioxide. Marked increases in plant pro— duction have been obtained by carbon dioxide enrichment of greenhouse atmosphere (119). Soybean yields have been increased when plants were grown in a carbon dioxide enriched atmosphere (20). Increasing carbon dioxide concentration during the reproductive stages may increase storage capacity and yield. The number of ear—bearing tillers in barley was increased by such treatment (41), whereas in rice both grain number and grain size were increased (126). Carbon dioxide enrichment only during grain filling can also increase yield (41, 126). Carbon dioxide enrichment at flowering increased the number of pods in soy was reduced increased 1: concentrati 350 to 1,00 fruits by r also increa as well as indicate t1 ment are b4 Al‘ abscission abscission appreciabl 0f ethylen 33. together w lima bean “One inc: When Combj retention S( \ flOWering flowers in 10 pods in soybeans under field conditions, but seed size was reduced, whereas enrichment during pod filling increased both seed size and yield (45). Increasing the concentration of carbon dioxide in the atmosphere from 350 to 1,000 ppm decreased abscission of young cotton fruits by nearly 50% (43). Carbon dioxide enrichment also increased the yield of sugar beet and kale (39), as well as many greenhouse crops (119). These results indicate that plants grown under carbon dioxide enrich— ment are better able to retain fruits. Although there are few reports on its effects on abscission in intact plants, carbon dioxide retards abscission in explants; it reduces the rate of abscission appreciably (4), and counteracts the promotive action of ethylene (3). Relative humidity. Low relative humidity, together with high temperature, promotes abscission in lima bean flowers and fruits (22, 63). High humidity alone increases pod set and retention, but is detrimental when combined with low temperature (38). In peanuts, high relative humidity favors the development and retention of fruits (64). Soil moisture stress. Moisture stress during the flowering and pod filling period increases abscission of flowers and fruits in garden beans (13), and cotton (37). Soil moistu Among the c auxin (49) ethylene re 127, 128) . Fa< rainfall (I abscission Internal F In flower abs tally unti flowers th on the has being char the facto: in Which 1 flower, w that the from the tended to grow more they WOu] on the be Thus , tht 11 Soil moisture stress alters hormone levels in plants. Among the changes reported are: decreases in diffusible auxin (49) and cytokinin activity (54); increases in ethylene release (68) and abscisic acid levels (122, 127, 128). All these changes would favor abscission. Factors such as nutrient deficiency (69), excess rainfall (l4) and severe defoliation (67) also favor abscission of reproductive structures. Internal Factors In lima beans, position on the raceme influences flower abscission (22). Fruit setting occurred acrope- tally until a "capacity set" was attained; the remaining flowers then abscised. Therefore, pods occurred largely on the basal portion of the raceme, the terminal part being characteristically barren. Ojehomon (76) examined the factors controlling pod retention in Vigna unguiculata, in which only the pods of the basal racemes, the first to flower, were normally retained. Autoradiographs showed that the upper flowers did receive some labelled assimilate from the subtending leaf. Ovaries which failed to develop tended to be smaller at the time of flower opening, to grow more slowly, and eventually to lose weight. However, they would abscise even if comparable in size to those on the basal racemes, unless the latter were removed. Thus, the basal racemes appeared to promote abscission in the mor the assimi through tl A] reported a like hormt hormones ; better de: Powell an. probably V Pods form on the Cl and anti- POd, naph henzoic a eluded tt (110). z in lupine Which del of flowe; elusiVe, (flower (mature h°seHME HM Owfiflflnwwm mmVOAW ~U0UH~U0HQ mHmwwaHrnn IHO MURMHW mvwnwcfiwfinwlmnvmnmm H0“ WQUHM> 2.002 N QHQMH 4O .AHo>oH wmv Home mmcmm mamfluasz m_cmosso on“ an moosouommap uGMUAMHcmflm oumoflpcfl soEEoo ca uoc mnopuoq "ouoz mm mm on As a so 6 mm a pm eaonm amneosm moon em a om m on 6 mm m OOH announce new as on we a mm 6 mm 66 son mmouceuo moon mm a am 6 mm so so no sea emesee on was n am 6 mm eon mm co has meow nausea noeam u am 6 mm n we 8 mm o med nmnmueom 6 Ana a am a co co mm 6 was «as opens be can n mm a so one me n «mm memo mean as on as n we a am he mmm mace can em a Hm be as he mm m sea conserves an. no. mammal 33...... e an... nus. coflmmflomom com com Hozoam mo oomudoouom pom umo>nnm pm cocfiwuom moom .omosponm muozoam mo mucmam owucuamloommm mom monam> Goo: N OHQdB 9T 82' 66 .% hcanbmnm flowe: Plant 41 98t- Black Turtle Soup . Seafarer -_ __ Michelite 3 2 "$3 "3 '-.\ ‘:\ :1\// 66 - i Percent u: o I \ _ \ 34 \ \ \ \\ '\ \ //\\ I, l8— \/ \ I a \ /\ ' \ . \v \ I \ \ ’ \ '2 \I \ l '. L \l \ I 0 5 IO l5 Days after flowering Fig. 3. Pods retained per day as a percentage of flowers produced on that day (data from greenhouse grown plants). I2— l0— c r e p a ition d 42 l2 " [,4 / \ Block Turfle Soup / \ / .. . Seafarer , ‘\..-_- Michelife Percent o L J l \' a 5 IO IS 20 Days after flowering Fig. 4. Flower production in a specific day as a percentage of total flowers produced under field con— ditions. doom 0:3... xoo_m .II. . .mcoauflwqoo madam Hops: GBOMm #m®>Hms um m mm .hMU dawfloomm a so canon mum3oam Eoum coca mcom ngou mo mvmwnmoymm meme com .m .mfim octmso: 5:0 900 m: o. m 43 2:93;). -llll &m&°‘omm 0.000 a... asom 22:... «.005 attribut conditio diseases Also it much gre to that high rai associa* on fielr between and pod Apart f cultiva growing the lee Michelj absciss Vars u] the gr due to Were g time ( (10) , Vars M farer of Mi< 44 attributed to greater variations in the environmental conditions such as moisture stress, heat, wind, pest and diseases to which the plants were occasionally subjected. Also it was noticed that under the field conditions a much greater number of flowers were produced as compared to that of greenhouse grown plants (Table l and 2). A high rate of abscission in the field probably can be associated with the greater number of flowers produced on field-grown plants. A high negative correlation between the yield per plant and the percentage of flower and pod abscission was reported in garden beans (1). Apart from the higher abscission rate under the field, cultivar differences in abscission existed under both growing conditions. Black Turtle Soup, which produced the least number of flowers, had the lowest while Michelite and Seafarer had the highest percentage of abscission (Table l and 2). The pattern of flowering was longer in all culti- vars under the field—grown plants as compared to that of the greenhouse—grown plants (Fig. l and 4). This may be due to the longer daylength in summer when the plants were grown in the field, and better growth rates at that time (Table l and 2), the same as was shown in soybean (10). The patterns of pod retention for the three culti— vars were similar under both greenhouse and field. Sea- farer had an earlier peak for pod retention than those of Michelite and Black Turtle Soup. This pattern of pod retentic duced f: ripe po< phenome 6). Th flowers develop or by t flowers growth mately These in eit and 2) and ph are nc also k t0 it: archi- 45 retention peaks indicates that the flowers that are pro- duced first are most likely to be retained to produce ripe pods containing good seeds (Fig. 3 and 6). This phenomenon was also shown in lupin (ll) and cowpea (5, 6). This may be explained either by assuming that early flowers have the first share of nutrients for their development, thus having a greater chance of survival, or by the release of an inhibitory substance to inhibit flowers set at a later time. Although Seafarer and Michelite differ widely in growth habit and flowering patterns, they share approxi- mately 92% of their germplasm in common (Adams, per com.). These two cultivars have similar percentage of abscission in either greenhouse or field—grown conditions (Table l and 2). This indicates that there may be separate genetic and physiological factors controlling abscission which are not affected by growth habit. These factors must also be considered in breeding to better fit the plant to its environment especially when gross changes in plant architecture are proposed. 2:932). LOLO&O0W QJOW 0:51;. loo—m ...... 46 .AmucmHm CBOMmIUHon Eouw m no poouwonm mnozoaw mo ommusoouwm c no how Mom UmsHMpoH mpom wwcwmwmc @5826: 5:0 930 m. 0_ m _ 5.4.1.1151, .. _ ll . . II'IOO 2:222 .irll hob°&°0m coo... aaom 2:3 .305 omen OO_ Bin] Gre‘ Hod Kan Oje Ojr REFERENCES Binkley, A. M. 1932. The amount of blossom and pod drop on SlX varieties of garden beans. Proc. Amer. Soc. Hort. Sci. 29: 489—492. Greenwood, E. A. N., P. Farrington and J. D. Beres— ford. 1975. Characteristics of the canopy, root system and grain yield of a crop of Lupinus angustifolius cv. Unicrop. Aust. J. Agric. Res. 26: 497-510. Hodgson, G. L. and H. E. Blackman. 1956. An analysis of the influence of plant density on the growth of Vicia faba. I. The influence of density on the pattern of development. J. Expt. Bot. 7: 147-165. Kambal, A. E. 1968. A study of the agronomic char— acters of some varieties of Vicia faba Sudan Agric. J. 3: 1-10. Ojehomon, O. O. 1970. Effect of continuous removal of open flowers on the seed yield of two varieties of cowpea, Vigna unguiculata (L) Walp. J. Agric. Sci. 74: 375—381. Ojehomon, O. O. 1972. Fruit abscission in cowpea, Vigna unguiculata L. Walp. 1. Distribution of I21C—aSSimiIates in the inflorescence, and com— parative growth of ovaries from persisting and abscising open flowers. J. Expt. Bot. 23: 751—761. Rowlands, D. G. 1961. Fertility studies in the field bean (Vicia faba L.) II. Inbreeding Heredity 16: 497-508. SOPer, M. H. R. 1952. A study of the principal factors affecting the establishment and develop— ment of the field bean (Vicia faba) J. Agric. Sci., Camb. 42: 335—346. 47 6 .SW Val 10. ll. 48 9. Swen, M. A. 1933. Factors affecting flower shedding in soybean. Ph.D. dissertation, University of Illinois, Urbana. 10. Van Schaik, P. H. and A. H. Probst. 1958. Effects of some environmental factors on flower production and reproductive efficiency in soybeans. Agron. J. 50: 192—197. 11. Van Steveninck, R. F. M. 1957. Factors affecting the abscission of reproductive organs in yellow lupins (Lupinus luteus L.). I. The effect of different patterns of flower removal. J. Expt. Bot. 8: 373-381. ABSCIS bean Q 18-hou: The run counte (10 da Pod fi Weight record Greate tWO cu under _______——— _____._———— CHAPTER 3 ABSCISSION OF FLOWERS AND FRUITS IN PHASEOLUS VULGARIS L. II. GROWTH AND POD ABSCISSION AS AFFECTED BY DIFFERENT DAYLENGTHS Abstract Greenhouse—grown plants of two cultivars of dry bean (Phaseolus vulgaris L.) were subjected to 8, l3, and l8-hour photoperiods after the flower buds became visible. The numbers of flowers that opened on each plant were counted daily. Plants were harvested at peak flowering (10 days after initiating photoperiodic treatment), at pod filling (20 days), or at maturation (40 days). Weights of roots, stems, leaves, fruits and seeds were recorded, and leaf areas determined. Pod abscission was greater under short photoperiods and differed for the two cultivars. Plants were larger and yielded more seed under longer daylengths. 49 l l l l as the c Among tl soil mo: plant n1 mechanil photosy in cott Factors plant c spacing (6, 12) ation a Can be Ontoge that p Plants t0 mes fruit area b Photo: Stage: 50 Introduction A number of environmental factors have been cited as the cause of abscission of reproductive structures. Among these factors are extremes of temperature, humidity, soil moisture, light duration and intensity, inadequate plant nutrition, disease, insect infestation, and mechanical forces such as wind and rain. Abscission may be promoted by a deficiency of photosynthate. For example, shading increases abscission in cotton (5, 6, 7), soybean (3, 11) and Vining peas (13). Factors which reduce the amount of light reaching the plant canopy, such as cloudy weather (9, 12) and close spacing (2) increase abscission in young cotton fruit (6, 12), and soybean (lO). Partial or complete defoli— ation also increases abscission. Most of these results can be attributed to a deficiency of photosynthate. Abscission can occur at several stages in ontogeny. However, Meadley and Milbourn (13) showed that pod abscission in pea was markedly increased when plants were shaded from flowering onwards. In order to meet the increased demand for photosynthate during fruit development either photosynthetic rates or leaf area must be increased. In soybean the rates of leaf photosynthesis are much higher during the pod filling stages (4, 8). i i ! effects dayleng Turtle in fld Three greenh days a plant 0f eac stem ( was we dry WE Mam: divid under house Were throu consi With inCar Plani 51 The purpose of this study was to measure the effects on growth and pod abscission of differential daylengths. Materials and Methods Two dry bean cultivars, "Seafarer" and "Black Turtle Soup" were chosen for study because they differed in flowering habit and rate of pod abscission (Chapter 2). Three seeds were planted in each of 150 35-cm pots in the greenhouse in early April, 1975 at East Lansing. Ten days after emergence the seedlings were reduced to one plant per pot. At flower initiation lO uniform plants of each cultivar were harvested, and separated into root, stem (including petioles), and leaf. Leaf area per plant was measured and, after freeze drying of all plant parts, dry weights were determined. At the time of flower initiation 90 uniform plants of each cultivar were selected, and randomly divided into three groups of 30 plants, which were placed under 8, 13, or 18—hour photoperiods in the same green- house. For the 8—hour day, black polyethylene curtains were opened at 8 a.m. and closed at 4 p.m. each day throughout the experiment. The l3— and 18—hour treatments consisted of natural light plus supplemental lighting with a mixture of high intensity from fluorescent and incandescent lights. The intensity of the light at the plant level was 70,000-75,000 lux, ample for maximum photosy: to avoit was main night. opened flowers ing (10 at pod experin harvesf harvesl ments, (1 the s HOWQV 52 photosynthesis. A black screen separated the treatments to avoid any interference. The greenhouse temperature was maintained at 25—29°C in the daytime and 18—21°C at night. All plants were numbered, and the flowers that opened each day were recorded to give the number of flowers produced. Plants were harvested at peak flower- ing (10 days after the beginning photoperiodic treatment), at pod filling (20 days), and at maturity (40 days). The experiment was analyzed factorially with three factors, harvesting time, cultivar, and daylength. In each harvest, 10 plants per cultivar were used for all treat— ments, and the parameters measured in each harvest were: (1) Number of pods and number of seeds per plant (second and third harvest only); (2) Number of trifoliate leaves per plant (first and second harvest only, since leaves had senesced on mature plants); (3) Leaf area per plant (first and second harvest only); (4) Root, stem (including petiole), leaf, seed and pod dry weight. The above experiment was repeated in 1976, using the same greenhouse, cultivars and lights as before. However, 25 cm pots were used instead of 35 cm pots. Pod Abs‘ more po percent Turtle show th hours ( ever, r since 1 ever, a one—hai days a: greate of pod the 8- Stage In gen from a Cultiw deerea AbScis inc1u( SiOn 1 well floWe 53 Results and Discussion Pod Abscission Both cultivars produced more flowers and retained more pods as daylength increased (Table 1). In l975, percent pod abscission was markedly reduced in Black Turtle Soup under l3—hour day, while Seafarer did not show this reduction until daylength was extended to 18 hours (cultivar x daylength significant at 1%). How— ever, no interaction was evident in 1976. Pod abscission was not recorded at peak flowering since the pods were still attached to the plants. How— ever, at pod filling many pods had abscised. More than one—half of the pods lost having fallen in the first 20 days after anthesis in both cultivars. In Seafarer a greater portion of the pods abscised at the early stages of pod development (Table A-1, A-2, Appendix A). Under the 8—hour day many pods abscised at the pod filling stage in both cultivars (Table A—1, A-2, Appendix A). In general, considering both years increasing daylength from 8 to 13 to 18 hours reduced pod abscission in both cultivars (Table 1). At the mature stage pod abscission decreased progressively as daylength increased (Fig. 1A). Abscission data recorded at the pod filling stages included both late flowers and young pods. The abscis— sion of these structures may involve hormonal levels as well as nutrients. Similarly, shading of peas after flowering increased pod abscission (12). U-ICr H com m0 w WMDGTUH0R . vim \muom U0 unwed-z . MHmubaC _.n_. EC refill-5.2 H WHQNH. .umwB mmadm meHuHSE m.cmo:do mp Ho>mH wH wsu um qunowch NHHucMOHstmHm Hos mum mucuuoH HMHHEHm ha waOHHow HwHOEMHmm OEdm 05¢ GHSUHB mammzm .m.: .m.: .m.c «a .m.q .m.e HHH x HH x H .m.n an .m.: as .m.: as HHH x HH .m.: a. a a .m.: .m.c HHH x H .m.: .m.: .a .3 .m.e .m.c HH x H m:0HuomumucH x h mm x 5 mm N >.m N m.>H N «.mH N m.v~ mndom mH h w.we h v.n¢ a h.n % N.0H w «.mH a m.mH mndom MH N m nm N h.mm x m.m x m.m x «.0H x H.0H mudom m mnumcmHmma .HHH c a.mm : «.mm c N.m a o.vH : o.nH a >.v~ Hwnmmmmm E N.mm E m.om E m.m E m.m E m.m E w.0H msow mHuHse HOMHm A. 5 Hm>Hu H50 . H H n H.vm n p.mm m m.m m m.> no w.NH m p.mH huHusumz m H.~v m m.mm n m.h A m.m n w.mH m w.bH mcHHHHH com I r o ¢.0H o e.mH m m.HH m m.>H mcHuoson xwmm wEHB mcHumw>umm .H mhmH mhaH man man msmH man :OHmmHomn< w wcom mo uwnfisz mnw3on mo HwnEdz mAmucwEumouu you mecca mucmmoummu mummy mhmH was mhmH :H wCOHqusoo wmsoncmmuw Hops: GBOHU wum>HuHso comm mun 039 m0 GOHmmHoma¢ com mo ommuscouom can .mpom mo Honfidz .wumonm mo Hmnfidz co wEHB msHHmo>Hmm can mnumconmo mo mpomwmm H magma 55 ' 8 hour do c 80? y 0 '5 U) '5 U) .D O 'U 0 Q. o\° Days after flower initiation E 8 hour day .. eat- :2 0 E asses: l3 hour day 3 Is— 7 3: Vi l8 hour day .m, E, 0 IO : ' 3 : B -’ 3. "" .‘ 9 5 0 IO 20 40 Days after flower initiation Fig. 1. Interaction between developmental stages and daylengths on percentage of pod abscission (A), and total plant weight (B). (Data taken from 1975, averaged over two cultivars.) L“ _. _.._. pods a hour d abscis in Bla under correl abscis with h photop negati negati under Vegeta the es the cc Signil betweg istics Photo} Sigl‘ii: of b0. for b. titio: 56 Competition for nutrients between flowers, young pods and growing apices was probably severe under the 8— hour day. The correlation between percentage of pod abscission and number of flowers produced was significant in Black Turtle Soup under 8- and l3~hour days but not under the l8—hour photoperiod (Table 2). The positive correlation agrees with data for garden bean in which abscission of flowers and pods is greater in varieties with high flower number (1). However, under the l8—hour photoperiod the number of flowers borne per plant was negatively correlated with abscission (Table 2). The negative correlation was insignificant in both cultivars under the 18-hour day. Because Seafarer is determinate, vegetative growth competed less with fruit set than was the case in the indeterminate Black Turtle Soup. Thus the correlation between abscission and flower number was significant only at the l3-hour photoperiod (Table 2). The preponderance of negative relationships between percentage of pod abscission and the character— istics representing vegetative growth at the l8—hour photoperiod, though individually not always statistically Significant (Table 2) nevertheless implies that the plants Of both cultivars are producing photosynthate sufficient for both an increase in growth and a removal of compe— tition between developing POdS- AMHCMHQ CBCLC UPOr 5(lu (iii! llurruL r 1 . MDGMEHMOHB QUEGQHNMQ UCUH0MWHQ 0U UQUowflfldm MHM>HUHUU Gflmm AHQ 03H GH WHQU®ENHMN HUSRO 6G6 mwhfl Mfl0fl H0 SOHmmfiomflfi 00% N0 mmMUGwUHmm C$03U®m mHC0HUHMMQOU COHUMHQHHOU N ”damp“ .Hu>mH WH um usmonHamHmh .Hm>mH am no nemoHMHemHmm om. Mme. mm. mo. omm. cam. ucmHoB comm me. 9mm. new. MHw. 3mm. who. mpoow mo Hmflfisz th. Hm. amp. me. Hm. chm. mpom mo HMQESZ 9mm. we. 9mm. new. now. new. wuaonw mo Honfidz mv. mm. com. MH. MH. 3mm. UOHHom maHHQBOHm "m> wand mama ow.i 5H. wH.I Hm.i hm. Hm. mono mood wo.i mo. mN.i mH.i we. cam. Hunada Moog mm.i om. MH.| me.i ow. aHm. HamHm3 wood Ne.i Hm. mo.i vN.I me. we. pamHuB Eme W mm.i mH. mH. mm.| hm. mm. ummHms poem om.| mv. he. mH. mm. new. usmHoS comm th.i Hm. mm. Hm.i mm. new. woman mo Hunfidz Qm>.i mN.i hm.i hv.i mm. mo. mcom mo HoQESZ «o.i mHm. vm. vm.i new. mHn. muuson mo HmQESZ mm. mm. om.i mm. mm. mm. UOHnom maHuoBOHm um> QOHmmHomnm com w musom mH mmdom mH musom m mnsom wH mmsom MH mndom m mhmumfimnmm HdHMwmmm msom oHpHDB MOMHm AmwsmHm czoum mhmH Eoum cowpm @GHHHHM com any um deMH opccv msHHoson Hopm< masufipmuue numaonmQ ucmHmmeQ op puuooflndm mum>HHHdo swam use 039 GH muoqudem Humpo was scum wqu Ho GOHmmHomQ< pom mo meHGmouum doquom mucoHOHmmooo GOHHcHoHHoo N GHQMB Leaf De cantly weight Turtle differs of lea‘ mentin (Table signif no lea compon tent w Capaci nifica both c Photo; nifica days j nific; for S( 58 Leaf Development Leaf number, area, and weight increased signifi- cantly with daylength (Table 3). Leaf area and leaf weight per plant were significantly greater in Black Turtle Soup than in Seafarer in 1975; only the latter difference was significant in 1976. However, the number of leaves per plant was not affected by cultivar, docu- ) menting the larger leaf size in the Black Turtle Soup (Table 3). Leaf number and area per plant did not change significantly with time in 1975 (Table 3) indicating that no leaf growth occurred after the pods were set. Leaf area was positively correlated with yield components in all daylengths (Table 2). This is consis— tent with many reports that greater photosynthetic capacity results in higher yield. Leaf area was sig— nificantly correlated with length of flowering time in both cultivars under 8—hour day, but not under longer photoperiods (Table 2). Yield (seed weight) was sig- nificantly correlated with leaf area under 8 and l3—hour days in Black Turtle Soup (Table 2). However, no sig— nificant correlation existed between leaf area and yield for Seafarer plants under 8 and l8—hour days. Plant Development Weight of all vegetative parts increased with daylength in both cultivars and in both years (Table 4, A-5, and A-6). This was associated with a greater number rill LI‘r UGM HGMHAH “mum .mflmmdn WW0H.~HGMHW Hmnu Dimflwg Hmwfl G0 Whambfinvwnfic Tin ".0in {lulllilil -. i M: MyHfifiMn—w ll--i-.: la. .umoa madam mHmHuHEE m.Ed0CDQ an Hm>wH wH can no uswummec HHucmonHamHm Hos cum mhupumH HMHHEHm an poBOHHOH noqumHmm uEam on» EHQHHS mqmozm .m.s .m.c .m.a .m.a .m.a .m.a HHH x HH x H .m.: «. .m.E a3. .m.E «a HHH x HH .mé .m.: .m.: .mé .. .mé HHH x H .m.a .m.s .m.c .m.c .m.: .w.a HH x H mGOHuoaMupaH N mH N mH N ONMH N nme N m.m N h.m musom mH s NH s 3 m 83 s 33 s TN m w.m mueom S x OH x «H x mmw x NbHH x w.H x m.N mudom w managing .HHH mu EMH a pH E era E Nva E m.m E w.m Hmumumum E NH m mH a mvHH a eon E m.N a h.e muom oHuHSB Moon Hm>HuHDU .HH b mH m mH n HMHH m thH m m.~ n m.q mcHHHHH com m NH a pH w Hmm m «mMH m m.~ m >.m maHHwBOHH Mmom oEHB msHHm®>me .H mhmH mhmH man mhmH mhmH man MEMHm\Hm0H oUMHHOHHHB Ho uwnEdz ANEOV HEMHm\mmH< mood Amv ucmHm\u3 Moog mfiucmEumoHu How msme munomwummu mumcv man cam mhmH Hmow map EH mnoHuHUsoo mmsoacuouo Hopes ESOHU HGMHA Hem mm>muH oHMHHowHHB Ho uwnEdz can usch new comm mama .ngHm Hum usmHoB mama so mum>HHHSU cam meHB mEHHmw>Hmm .mEHmEOHmmo Ho muoomwm m mHnma and pe vegeta with 1 Black plants ing; 1 while plant fillh weigh' after sink and s more organ Tenet orgar Photc Sad plan- leng Plan (Tab Turt 60 and percentage of pods retained (Table 1). Greater vegetative growth (Table 3 and 4) was also associated with lower abscission (Table 1) when 1975 values for Black Turtle Soup are compared with those for Seafarer. The weight of the vegetative portions of the plants in this experiment did not increase after flower- ing; root and stem weights tended to decrease (Table 4), while leaf weight remain unchanged (Table 3). Total plant weight increased from peak flowering to the pod filling stages (Table 4), as a result of increasing pod weight. It could be assumed from these results that, after flowering, pod development comprises such a strong sink for assimilate (or nutrients) that pods are effective and successful competition with vegetative organs. A more likely explanation is simply that the vegetative organs have reached their final size, as determined by genetic potential in this environment, and that these organs are, in fact, no longer competing for the available photosynthate (or nutrients) with the pods. Seed Yield The number of normal—sized seeds produced per plant was greater for both cultivars under longer day— length (Table 5), resulting in greater seed weight per plant. Weight per seed was not affected in 1976 (Table 5); effects varied with cultivar in 1975. Black Turtle Soup seeds were larger under 13 and 18 hour than FNI+CE T‘fl Ellis-U ills: l . i v OHQMH 61 um uaouomec NHHEMUHwHamHm Ho: .pmwB wmcmm a mum mnuuuoH HmHHEHm an po3oHHow HoquaHm m wEmm msu EHEHHS mucosa .m.a a .m.: .m.c .m.c .m.: HHH x HH x .m.E .m.E .m.E an * .m.E HHH X H% is a; a a; an. on ..... a... ..... . a... a...“ .m .w mEOHuomuuucH N m.oH N H.mH N m.H N N.N N m.H N o.~ mudom mH N e.m N N.m N H.H N e.H N m.o N o.H mayo: ma x m.m x n.m x m.o x m.H x m.o x m.o mHDom m manmeoHNmo .HHH E v.h E w.m E v.H E h.H E H.H E H.H kumwmwm E v.w G o.HH E ~.H : m.H E m.o : v.H m50m mHuHSB xomHm Hm>Hquo .HH 9 m.> a m.HH a H.H m w.H m m.o m m.o muHHDuwS n m.m o m.NH n m.H n o.m m o.H n H.H maHHHHH pom m m.v a N.N m H.H Q o.m m o.H o m.H mGHston gnaw mEHB msHumo>Hmm .H mbmH mhmH whmH man man mhmH flow #3 HGMHm HMHOB Amv HEMHm\u3 Emum Amv Hame\p3 uoom MAHdUEUMNHU. .HOM mdmwfi mpaomcumou mumcv man cam man you» on» CH mGOHuHcaoo omsoscuono Hones azouw HEMHN Hmuoa can Eouw .uoom Ho pamHm Hum uanoz unu so mum>HuHsu can moEHB mEHuwo>Hmm .mnumsoHNMQ Ho muuomum a magma dfiHBSmLBBBQNaHQEHWHofi .mucm VvC—KFQ. (rd!) I—.f_.>\u..fl.h«h "\(lrk Fltlll m THQMB 62 smog ** omtflH omen om'HH Oman HH x H EOHHOMHMHEH x eH.o x NN.o N N.m N 0.x N a.mm N a.mw NH x NH.o x «N.o N N.m N m.e N m.mN N a.mm NH x mH.o x mm.o x m.N x e.N x m.HH x m.mH m H.muev sumaoHNmo .HH n mH.o m mm.o m N.m m m.e m N.mN m a.mm noummmom m vH.o m Nm.o m H.m m w.m m a.mm m m.mm msom oHuHSB Mome Hm>HHHdo .H whmH mhmH mhmH mhmH mbmH mhmH Nov Ame emmm\uz .ne comm Hmooe pcmHm\emom .oz mmEOmmom mbmH can mhmH EH EBOHw mum>HuHoo scum Nun 038 CH comm Mom uanoz can HGMHm Ham uEmHoz comm Houoa .Haon Hum mcoom mo uonEsz so EpmcuHNwo Ho muoommm m mHQMB under for Se growt] absci ditio ment 63 under 8-hour daylengths, whereas the reverse was true for Seafarer. Within the same variety, plants having greater growth before flowering usually associate with lower abscission level. Also favorable environmental con- ditions after flowering are required for seed develop— ment and fruit retention. 10. REFERENCES Binkley, A. M. 1932. The amount of blossom and pod drop on Six varieties of garden beans. Proc. Amer. Soc. Hort. Sci. 29: 489-492. Brown, K. J. 1971. Plant density and yield of cotton in northern Nigeria. Cotton Growing Rev. 48: 255—266. Cartter, J. L. and E. E. Hartwig. 1962. The manage— ment of soybeans. Adv. in Agron. 14: 360—412. Dornhoff, G. M. and R. M. Shibles. 1970. Varietal differences in net photosynthesis of soybean leaves. Crop Sci. 10: 42-45. Dunlap, A. A. 1943. Low light intensity and cotton boll shedding. Science 98: 568-569. Eaton, F. M. and D. R. Ergle. 1954. Effects of shade and partial defoliation on carbohydrate levels and the growth, fruiting and fiber proper— ties of cotton plants. Plant Physiol. 29: 39-49. Eaton, F. M. and N. E. Riglez. 1945. Effect of light intensity, nitrogen supply, and fruiting on carbohydrate utilization by the cotton plant. Plant Physiol. 20: 380-411. Ghorashy, S. R., J. W. Pendleton, R. L. Bernard and M. E. Bauer. 1971. Effect of leaf pubescence on transpiration, photosynthetic rate, and seed yield of three near-isogenic lines of soybeans. Crop Sci. 11: 426—427. Goodman, A. 1955. Correlation between cloud shade and shedding in cotton. Nature 176: 39. McAlister, D. F. and O. A. Krober. 1958. Response of soybeans to leaf and pod removal. Agron. J. 50: 674-677. 64 65 ll. Mann, J. D. and E. G. Jaworski. 1970. Comparison of stresses which may limit soybean yields. Crop Sci. 10: 620—624. 12. Mason, T. G. 1922. Growth and abscission in Sea Island cotton. Ann. Bot. 36: 457-483. 13. Meadley, J. T. and G. M. Milbourn. 1971. The growth of Vining peas. III. The effect of shading on abscission of flowers and pods. J. Agric. Sci. 77: 103-108. ABSCI III (m 13 an repro struc seed, durin with tion there the s TUrtI free Cult Stem root CHAPTER 4 ABSCISSION OF FLOWERS AND FRUITS IN PHASEOLUS VULGARIS L. III. RELATIONSHIP OF POD ABSCISSION TO DIFFERENTIAL LEVELS OF CARBOHYDRATES PRODUCED BY VARIATION IN DAYLENGTH Abstract "Black Turtle Soup" and "Seafarer" dry bean (Phaseolus vulgaris L.) cultivars were subjected to 8, l3 and lS—hour photoperiods in the greenhouse during their reproductive phase. Free sugar, starch, and total non— structural carbohydrate concentration of root, stem, leaf, seed, and pod wall were determined at different stages during pod development. Free sugar concentration increased with photoperiod in all tissues. Higher starch concentra— tion was found in all tissues except in the root where there was no difference in starch concentration between the short (8—hour) and the long (18—hour) days. Black Turtle Soup, an indeterminate cultivar, contained more free sugar in all tissues than Seafarer, a determinate cultivar. Black Turtle Soup contained more starch in stem and leaf, but not in root and seed. Free sugars in root and leaf rose from peak flowering to pod filling, then 66 67 decreased. However, free sugars in stem, seed, and pod wall declined as the pod matured. In general, starch concentration of vegetative organs (root, stem, and leaf) decreased as the plants matured, while that of the seeds increased. The general pattern of higher available car— bohydrate under long photoperiods was associated with greater vigor, higher yield, and reduced pod abscission. Pod abscission data indicated an inverse relationship to available carbohydrate concentration in vegetative organs. 68 Introduction Seed yield is determined by the number of flowers produced, the percentage of fruit set, the number of seeds per fruit, and seed size. Flower and young fruit abscis— sion is extensive in many economic crops (4, 6, 14, 15), and is often related to environmental conditions, espe- cially those that influence photosynthesis (3). Abscission of young fruits may be controlled by levels of nitrogenous or carbohydrate reserves (5, l6). Spraying cotton plants with 20% sucrose and 1% nitrogen as urea actually increased abscission (1). However, the endogenous carbohydrate level was not influenced. Gird- ling increased carbohydrate level, and a 2% urea spray increased the nitrogen level (1). However, combining the two treatments considerably increased boll abscission. These results raise a question on the role of carbohydrate in fruit abscission (1). In previous work, pod abscission was reduced and seed yield increased in dry beans by exposure to long photoperiods during the reproductive phase (see Chapter 3). The present study was designed to determine the effect of photoperiod on levels of available carbohydrates. Materials and Methods Sample Preparation Two dry bean cultivars, "Seafarer“ and “Black Turtle Soup," were chosen because of differences in plant 69 type, flowering habits, and pod abscission rates. Seeds were planted in 35-cm pots in the greenhouse at East Lansing in early April 1975. Growing conditions have been described previously (see Chapter 3). Plants were harvested at (a) flower initiation, just before beginning photoperiod treatments, (b) peak flowering, 10 days after flower initiation, (c) pod filling, 20 days after flower initiation, and (d) maturity, 40 days after flower initiation. At each harvest 10 uni- form plants of each cultivar were separated into root, stem (including petioles), leaf, pod, and seed. The samples were freeze-dried, weighed, ground in a Wiley mill having a 40—mesh sieve, and stored in scintillating vials at room temperature prior to extraction. Determination of Free Sugars The method used was a modification from Laidlaw and Reid (7). Free sugars were extracted by refluxing 100 mg samples in 80% ethanol in a water bath at 60°C for two hours, with occasional shaking. Samples were filtered through Whatman #1 paper and the filtrate was evaporated under vacuum at 50°C to near dryness. Volume was adjusted to 25 ml with distilled water. The solution was clarified with 10% lead acetate and then deleaded with potassium oxalate (8). Volume was adjusted, to 50 ml in the case of root and pod wall and 100 ml for 70 stem, leaf and seed tissues, with distilled water prior to analysis. For analysis of free sugars, 5 ml of 70% anthrone reagent (19) was added to each 1.0 ml of extract. Before and after the addition of anthrone reagent the tube was immersed in cold water and shaken to obtain thorough mixing. The solution was heated in boiling water for 10 minutes, cooled to room temperature and absorbance was determined at 620 nm. Sugar content was expressed as glucose equivalents per gram dry weight. Determination of Total Non— structural Carbohydrates TNC) The extraction employed was modified from Smith (11). One hundred mg of tissue was placed in a 45 by 400 mm test tube, 15 ml distilled water was added, and the solution was boiled for 5 minutes to gelatinize the starch. After cooling to room temperature, 10 ml of buffer, pH 4.45, and 10 ml 0.5% takadiastase (Clarase 900) enzyme solution were added. The tubes were shaken in a water bath at 45°C for 44 hours (17). The solution was filtered through Whatman #1 paper into a 125 ml Erlen— meyer flask, and 2 ml of 10% neutral lead acetate was added to precipitate the proteins. After centrifugation at 12,000 xg for 5 minutes, the supernatant fluid was decanted into a second 125 ml flask containing 100 mg powdered potassium oxalate. These mixtures were kept 71 overnight in the refrigerator. The solution was stored overnight at 4°C, then centrifuged at 12,000 xg for 10 minutes, filtered through Whatman #52 paper, and made up to 200 ml with distilled water. TNC was determined colorimetrically at 620 nm using the anthrone—reagent technique as described earlier (19), and expressed as mg glucose per gram dry weight. Since TNC in legumes consists mainly of free sugars and starches (ll, 12), starch concentration was estimated as the difference between TNC and soluble sugars. The data were analyzed factorially using 10 plants per treatment (one plant per replication). Results and Discussion Free Sugar In general, free sugar levels increased with photoperiod in root, stem, leaf, seed and pod wall (Table 1). However, in the leaf highest levels occurred in plants subjected to l3—hour days (Table 1). Under the l8~hour daylength the movement of assimilate out of the leaf might have been more rapid, resulting in less free sugar in the leaf. Free sugars were higher in all tissues of Black Turtle Soup than in Seafarer (Table 1), indicating either a difference in rate of assimilation of carbon dioxide or a difference in rate of translocation of sugar, or .pom EOHH oumummmm Hog comma .umua omamm uHmHuch Hm uaoHomHHc NHHEmOHHHEmHm “on one muouuoH HopoEmncm oEcm map EHEHHB mucosa llIllllllllllllllllllllllllllli m.Emusso an H®>mH NH 03» HoHHEHm an cmBOHHoH . . HH x H ¥ omadn fix. an m C HHH u." anon. .m.G um ¥ yawn HHH uh HH 3; a a; «:1 c3. HHH X H a... a». a as «us HH x H mEOHuumnoucH N a.mNH N m.mm N a.mm N N.mm N m.mH muses mH x N.m0H N a.mm N N.Ne N N.Hm N m.HH mason NH x N.OHH x a.mm x m.mm x a.mv x H.NH musoc m 2 anmaoHNeo .HHH 7 a m.w0H E m.nm c a.mm E 0.5a c N.NH Honmmcmm E a.mmH E N.os E m.mm E m.>m E a.mH adom uHHHSH MomHm Hm>HuHso .HH m H.mN m m.HN - e N.sm n N.MH NNHHeumz n HeH e a.me n H.@@ n N.Nm o H.HH meHHHHN eon no mNH i a m.mm o w.wn c a.mH maHuosoHH xmum oEHH .H pom comm mood Emum uoom uzmHoB Nun a Hum omoous m2 AuEmHoB NHU .0 Hum meOSHm .mEv m . m whom ucch mSOHHm> EH Hu>aH Hmmsm ouum so muommmm EHmeHmmo can mHMbHuHDU .mmmmum HmpcwEmon>oQ H aneH 73 both. Differences in rates of translocation of 14C assimilates among bean cultivars have been reported (18). Differences in response of the two cultivars to increasing daylength was evident in free sugar accumu— lation (Table 2). Free sugar concentration of root, stem, and leaf was proportional to photoperiod in Black Turtle Soup, but not in Seafarer (Table 3). In the latter, the effects of photoperiod were nonsignificant in root, stem, and leaf sugars which were not increased by extending the photoperiod from 13 to 18 hours. This could be due to the differences in growth habit, for Black Turtle Soup plants continue growth after the reproductive stage is attained. Seafarer, on the other hand, is determinate and makes only slight additional growth after the reproductive phase has been reached. This may have reduced free sugar content under longer photoperiods (Table 3). Cultivar did not affect free sugar levels in seed and pod wall except under the lB—hour photoperiod (Table 3). This may be due to the greater ability of Black Turtle Soup to accumulate free sugars in these organs under longer daylength. In roots of Black Turtle Soup free sugar rose from flower initiation to pod filling, then decreased at maturity (Table 2). However, in Seafarer, free sugar levels did not change between pod filling and maturity. The accumulation of free sugar in roots at the later 74 .pmoa omsom onHuHDS m. #0: one muouHoH noHHEHm EHHB sooqso an Ho>oH NH o Huwm .onov muom use an on season uHe NHHEMOHHHeeHm mEESHoo EHEHHS moooZM iIiIIllIIIliIIIIIIIIliIIiiiliiiillli m H.wm a m.HN i a m.vm H N.MH coo: o m.mm n m.mN i o m.Hm a H.HH Houomoom m p.mm no H.Nm i Q m.mm n m.MH a50m oHuuse EDMHm ov a HeH a a.mm a H.mm a N.Nm a H.NH new: a emH m a.mm a m.mm o m.w¢ a o.vH uouomoom o mmH n m.m> c a.mn o m.mn o N.om doom oHuHSB Eoon om H oNH i a m.mm H m.vb m a.mH Enos 0 omH i o m.mv t m.om m m.m Houomoom c bmH i o N.Hm H «.mm a m.eH a90m oHuHSB Moon 0H i i a a.me m H.wm a m.NH ewes i i o H.vv co H.mm Q N.MH Houomoom i i o m.MOH m H.NHH o m.HH Edam oHHHDB Moon 0 HHoz com coom HmoH Eouw uoom Hmwmcv EOHuo Ho>HuHoo iHuHcH HoEOHm osmmHB “ovum oEHB omoSmmHB doom aH HucmHos Nnc m\omoosHm mEv mEOHpoHucoosoo Homsm oonm co mEHHmEom Ho oEHB can Hm>HuHso Ho muoommm N oHQMB 75 .umoB omsom onHuHsz m.EooEdQ NQ Ho>oH NH oQu um quHoHHHc NHHEMOHHHEmHm Hos oum mHoHHoH HMHHEHm QHHB Ame .OQoV muom cam mEEdHoo EHQuHB mEoozo . illllIIIIIIIi N m.mmH N w.omH N a.mm N a.mm N m.mH coo: o HHH o N.NHH Q m.mm Q m.mm m N.NH HoHoHoom Q NHH c m.mmH o N.HN p p.mb o w.mH QDOm oHquE Moon mH x m.GOH N N.NOH N N.Nm N N.He N m.eH new: a MOH Q w.HOH Q v.nm Q m.om o H.MH Houomoom m OHH 0Q m.MOH c m.on o m.HN Q «.mH doom oHuHDB Moon MH x m.OHH x m.Hm x m.mm x a.mv x H.NH coo: a mOH o n.5m o e.hv o N.Nm m o.mH Honomoom o mHH Qo m.vm Q m.mm Q w.mm o m.mH doom oHuHsa Moon m HHoz com coom HooH Eopm poem Hons v 0: Ho>Hu d onmeB H U UOHHoQOHOQm omosmmHB doom EH HHE NHU m\mEv coHpoHucooaoo Hmmsm ooum co Ho>HuHso can cOHHoQOHOQm Ho mHooHHm m oHQMB 76 stages of pod development in Seafarer may imply that there is a genetically programmed characteristic of this variety, or that root sink strength exceeds stem or pod strength. The level of free sugar in stem decreased as the pods matured in both cultivars (Table 2). Free sugar in leaves increased from peak flowering to pod filling (Table 2). The marked reduction in leaf free sugar from flower ini- tiation to peak flowering stages in Black Turtle Soup may be due to the movement of sugar from the leaves to the flowers. The decreased abscission of flowers and young pods at peak flowering of Black Turtle Soup as compared to Seafarer (Chapter 3) may be related to the drop in leaf sugar level at this stage. Levels of free sugar in seeds were not affected by cultivar, but fell rapidly between peak flowering and pod filling (Table 2 and 3). In both cultivars the sugar level in pod walls rapidly decreased as the seed matured (Table 2). This may reflect redistribution from the pod walls to the growing seeds, although a decreased rate of photosynthesis in aging pod walls may also be held accountable. Interactions between photoperiod and developmental stages were noted for sugar concentration of root, stem, leaf, seed and pod wall (Table 4). In the root, at peak flowering and at pod filling, free sugar level increased as photoperiod was extended to l3—hour, but no further increase occurred at l8-hour (Table 4). Levels were ,J .com EOHH ououomom HOE pooMQ oHaHuHsz m.emoaeo Na Ho>oH NH one on economee NHuemoHuHamHm HHEHm QHHB ANNx NOQov muom paw mEESHoo EHQuHE mcoozo .pmoB omcom HOE mum mHoHHoH Hm ilIllllllllllllllllllllllllllll N H.mNH N m.mm N m.mm N m.on N N.mH coo: . U H.NN I U N.mv o m.hH ow N m WMH e m.ON a N.NO m H.HH o O.OH ON o mmH i Q m.Ho o m.vN UoQ N.MH oH I I o m.m> m H.ww Qo m.NH o mH N N.OOH N O.OO N m.OO N v.NO N N.NH new: a m.vm 0Q a.mn i Q m.mm oQo m.NH ov a NNH n O.HO o m.MN e 0.00 o m.mH ON a NNH i n N.OO m e.HO so a.mH OH 7 r i o N.MN a H.OO om m.NH O NH 7 x m.0HH x N.wm x m.mm x w.mm x N.NH Enos o m.mm Q m.vm I o m.HN Qo H.HH ow o mvH o N.mv Q m.Hm o m.nv c m.vH om on mmH i o H.HH c w.hm o v.0H 0H t r o O.mN a H.Om be m.NH O O HHoB com coom mooH Eopm uoom HmNocv ECHpo H . “Hoocv i.HHEH HoBOHm m oSmmHB Houmm oEHB poHHo ouonm .m v oHQMB modmeB doom Ho HuQmHoB Nut m\mEv aoHpoHucooaoo Homsm oon co mcHHmEom Ho oEHB can pOHHomouosm Ho mpoowmm 78 proportional to photoperiod at maturity. In stems, the levels of free sugars at the peak flowering stage were similar under all photoperiod (Table 4), with the l8-hour treatment slightly lower than the l3-hour. At pod filling and at maturity, level was proportional to photoperiod. Under all photoperiods stem free sugar decreased as the pods reached maturity (Table 4) possibly due to re— distribution from the stem to the growing pods. Free sugar in leaves was significantly lower under 8-hour than under longer photoperiods at the peak flowering stage (Table 4), possibly because of a light period insufficient for maximal photosynthesis. However, the level increased at the pod filling stages under both the 8 and l3—hour daylengths, but not under the l8—hour photo- period (Table 4). This may be due to the stimulating effect of longer daylength on sugar movement out of the leaf. Free sugar concentration in seeds was proportional to photoperiod at all sampling dates, with maximum dif— ferences at pod filling, when the l8-hour treatment remained high relative to the 8- and l3-hour treatments (Table 4). The concentration decreased in all daylength treatments from peak flowering to pod filling. At maturity, however, the concentration increased slightly under 8- and l3-hour daylengths, while decreasing slightly under the 18—hour treatment. The increase in free sugar levels in seeds under the 8- and l3-hour daylengths was 79 accompanied by a decrease in stems and roots (Table 4). Free sugar levels in pod wall decreased independently of photoperiod as maturation advanced (Table 4), possibly due to re-allocation to the growing seeds. In pea, the pod exports all of its assimilate to the enclosed seed (2). Starch In vegetative tissues starch levels did not con- sistently increase with photoperiod (Table 5), levels in roots being lower under the l8—hour day in both cultivars (Table 6). No cultivar difference in starch level was evident under any of the daylength regimes. However, differences were seen in stems of Black Turtle Soup under the l3- and 18-hour daylengths (Table 6) since it stored more starch in stems than Seafarer. Also, Black Turtle Soup, which showed a greater growth response to longer daylength (l3, and see Chapter 3), had a higher level of starch in the stems under the longer daylengths. This response did not occur in Seafarer. The starch level was found significantly higher only in leaves of Black Turtle Soup under the lB—hour day (Table 6). The level of starch in seed and pod wall was not affected by increasing daylengths (Table 6). No cultivar differences for starch were found in these organs under the longer daylengths (l3 and 18 hours). .pom EONH oumuomom uoc mcoomQ 0 Nb Ho>oH NH on» um .uwoB omcom onHpHDE m.EmOE5 mo pcoHoHHHU NHuaoonHamHm Hos ohm mnouuoH HoHHEHm NQ coEOHHoH ma Em illlIllllllllllllllllllllllll .m.E .m.E «a as ea HHH N HH X H a N sx rr .m.E HHH XNHW as as «a re as HHH x H as .m.E re an « WWIlllllllll mEOHuooHoch N mmH N vmm N m.wm N a.mmH x a.mH mHSOQ wH N NON N NOH x a.me N O.NN N O.NN mason NH x ONH x NNN x N.Oe x O.em N N.NH mason N % npvaoHNoo .HHH E v.mmH E mmm E M.Hv E m.mm E a.mH HOHMmem E a.meH E mom a N.NN a m.m0H E m.mH doom oHuHDB EUMHm Hm>HuHso .HH N a.mN a N.NHN i a N.NN n N.HN NHHNsnmz o NHNNN o O.ONN m N.NN n N.NHH m a.mH meHHHHN com an m ON i n N.NN n N.NHH a H.ON aeHaoson Nana oaHa .H com poom HooH Eon uoom uQmHoB NHQ 0 Mom owoous m2 ompuom ucon mDOHuo> EH Ho>oH nouopm co mpoommm EHmEoHNoQ cam mum>HuHoo .mommum HouaoEQOHo>oQ m GHQMB 81 .#mwB mmcmm mamwuasz m.cmocsm NQ Hm>ma wa map um pom mum muwwpwa HMHNEHm :uH3 AuNx Nonmv mumm cam mGEDH pamHGMMH o NHNNNONNNNNNN oo :NNNN3 mammzm xIIIII|Illuulllnllllnlnnllnxxnln N ama N mmm N.Nm N ¢.mma N a.ma Emma o mmH a mmm «.mv n m.mm m N.NH Hmummmmm NH on mmH on mmm a.mNH o m.mmH gm N.NH mnom mHuNse xomam N NNH N NNN a.mN N a.mN N a.mm cum: 0 mma c nmm m.mm m m.mm do m.mm HmHMMMQm o NNH No mmm m.mm n a.moa c N.NN msom mauuse Nomam ma x wma x mmm m.wv x m.vm x a.ma cum: 2 mva Q omm m.mv m N.hw on h.ma Mmummmmm m Noa N NNN m.mv N w.~m an m.NH msom mapusa onHm m HHGS Uom mem “Amman emflm “Com AWHHAOASV mummaa Hm>flpasu UOHHwQOposm wwwnmmfla comm Ga AusoflwB an m\mEv Goaumuucwocoo noumum co Hm>fluaso dam coauwmogosm mo muommmm w GHQMB 82 The pattern of starch accumulation in roots during pod development of the two cultivars showed that at the onset of flowering Black Turtle Soup stored more starch in roots than Seafarer (Table 7). This difference remained until the peak flowering stage. However, when seeds started to develop, the starch level in the roots of Black Turtle Soup dropped to the same level as Seafarer and subsequently there were no cultivar differences (Table 7). Black Turtle Soup stems contained higher starch levels in the flower initiation and pod filling stages than Seafarer; cultivar differences in starch level in the stems disappeared at maturity (Table 7). The high starch level in the stem of Black Turtle Soup may have been due to the indeterminate character and prolonged flowering behavior of this cultivar. This ability to continue vegetative growth after flower ini- tiation can also result in higher starch level in leaves of Black Turtle Soup (Table 7). No differences were evi- dent between cultivars for the starch level in seeds during pod development (Table 7). The starch level in immature pods of both cultivars was lower at the peak flowering stage. At the pod filling stage when seeds could be separated from the pod wall, starch levels in green pod wall of both cultivars rose considerably (Table 7). At maturity the seeds still contained a high ii .pom Eoum wpmummmm won pmwmn : i W .umme mmcmm mamfluasz m.cmocna Nb Hw>mH wa map um quHwMMHU Napcmoflwflcmflm m uoq mum mumpuma NMHHEHm SuNB Anwm .onmv mumm Una mEEdHoo cflnuHB mammZM m «.mm m m.mvm I m m.mm w m.am now: no m.mv m m.mmm I w N.mm mp o.NN kumwmmm m m.vm m o.>vm I m v.mm moo m.am msom mHuHSB Momam ov H m.nmm w o.mmm m b.mm H ¢.NHH m v.ma com: U m.nnm o m.mmm m m.vm o o.mN on m.na Mohammwm o o.mmm n m.mnm m o.mm p h.mmH b N.mH msom mHuMDB Mowam cm 3 w m.mm I w m.mm H N.mHH v w.om cows 8 3 «.mm I b m.mm o m.>m won m.na “madmmom ab m.vm I o v.HNH U a.mva m a.mm msom manage MOMHm 0H m «.mm 6 N.wm m H.¢H com: I I m m.mm a H.Hm m a.N “mummmmm I I m H.bm 9 «.mm moo N.Hm m50m mHuHDB xomam o Ham: pom comm mama Emum uoom amNmpv cofiuw Hm>HpHDo INHHGH Hmzoam mummfla uwuwd mEHB Mmmsmmfie amwm EH Apnmflwz NHU w\mmoosam mEv coflpwupcmocoo noumum so mafiHmEmm mo oEHE paw um>wuadv mo muommwm N magma 84 starch content (Table 7), but starch in the matured, yellow pod wall dropped to a very low level (Table 7). Under the 8— and l3-hour daylength, the starch level in roots followed a similar pattern for both cultivar (Table 8). It was high at peak flowering, dropped markedly at the pod filling stage where carbohydrate reserve was in great demand for embryo development, and increased again at maturity where the final size of various organs had been achieved (Table 8). Under the l8-hour daylength the plants retained more flowers and pods (see Chapter 3, Table 1), thus more carbohydrates may have been available to support these reproductive organs and less was left for the root. This trend was especially evident at peak flowering (Table 8) where the starch level in root decreased. From peak flowering to pod filling where more than one-half of pod abscission had occurred, the plants had adjusted the number of pods to be retained. This may have caused a rise in starch level in roots at the pod filling stage under the lB-hour daylength. The interaction between daylength and stage of pod development on starch level in stems was shown in Table 8. The longer the daylength, the more starch was found in the stems at peak flowering and pod filling (lO and 20 days after flower initiation). At maturity, no significant dif— ferences were found for starch levels in stems between the l3- and 18—hour daylengths, but a significantly 85 .oom EOHM mumummmm poo wmmmn .umme wmsmm wamflpHSE m.cNoc5Q Nb Hw>wH NH was u boa mum mumupma HMHHEHm nufl3 AuNx .OQNV muMm paw msEd N NNNNNNNHN NH H00 sflsufl3 msmmzm NNNOHNHQNHN IIIIIIIIIIIIIIIIIIIIIIIIlIlilll N mmH N «mm N H.NN N H.NOH x m.mH NNNs a m.ON a HNm I N a.mm on m.om as N o.NNm a Nmm QN «.mN N N.NNH n o.mH cm a o.HN I N N.NNH N H.NNH N N.N OH NH I I a «.mm a N.Nm QN N.NH o N NNH N Hoe x a.ms N N.MN N m.HN NNNs N N.NN a HNN I N m.mm N N.NN ow N H.NHN N was a N.NN N H.NOH a m.NH om n m.Nm I n m.NN No m.mm N H.mm 0H I I n a.mm a N.mm NN N.NH o NH x NNH x Nmm x N.NN x N.mm x N.NH NNNz N N.NH N Nam I N a.mH a m.mH ON 0 N.mom N NNN N o.NH a m.mN N m.NH om an a.mm I o m.mN on H.mm No m.mm OH I I n a.mm n p.mm QN N.NH o N Hams pom comm mama Ewum boom AmNmov coaum Ansosv IflpflcH HmBOHm mdmmHB kuMAN GEM—H. UOHHGQOpOSm cmmswmfle cmwm mo Aunonz Nun @\wmoosHm mEV QOHumuudmocoo gouwum no mcHHmEdm mo wEHB paw poflummouoam mo muommmm w magma 86 lower starch level was found under the 8-hour regime (Table 8). The starch level in leaves reached the maximum at peak flowering and then declined rapidly. This was seen in both 8— and 18-hour daylength treatment (Table 8), while in the l3-hour day the starch level did not drop at the pod filling stage. No explanation for this is apparent. The starch level in seed and pod wall reached a maximum at pod filling and declined at maturity (Table 8). The rate of decline was more rapid in the pod wall than in the seed (Table 8) possibly due to the export of starch from pod wall to seed as was shown in field pea (2). This pattern was seen in all three daylength regimes, except no decrease was seen in starch level in the seed at maturity in the l8—hour day (Table 8). Perhaps the great decrease in starch in stems from pod filling to maturity may be related to the changes in the level of starch in seeds under this lB-hour day (Table 8). Relationship of Pod Abscission to Levels of Available Carbohydrates Increasing the daylength during the reproductive phase increased plant weight, seed yield, and pod retention in these two dry bean cultivars. In this study increasing the daylength after flower initiation also caused an increase in free sugar and starch levels in roots, stems and leaves. A relationship may exist between available carbohydrate in the vegetative organs and percentage of 87 pod abscission as was suggested in the nutritional hypo- thesis first put forward by Mason (9). In this study no precise relationship could be established between percentage of pod abscission and available carbohydrate levels in the vegetative organs of these two cultivars (Table 9). However there was a general trend of negative correlation between percentage of pod abscission and available carbohydrates in most organs. This indicated that the higher the carbohydrate levels, the lower the abscission rate. The data presented here, though con— sistent with Mason's explanation, do not prove the level of available carbohydrates to be the cause of pod abscis- sion in beans. Since abscission is a complex process, other factors than carbohydrate levels, such as nitro- genous levels or even endogenous hormonal levels, may play a part in determining pod abscission. Future studies toward establishing the balance of these factors in relation to pod abscission are needed. 88 .HN>NH NH NN NNNNHNHNNHNN .HN>NH Nm NN NNNoHMHNmHmN illIllII\\I\ Emwm as soumum mN.I Ho.l . . . mm I .I .I I mm mO.| OM.| WM.I %W. Mm. “OOH Cfl SOH69m mm. “wWNI WMNI WOol MHW.| QMWN EQHm Gun Hmwgm mmHh mm. mm.I NN.I NH.I HN.I oa. boos ca HomSm mmnm NuflusumE um .HH No. No. . . . . NN ca soNNum . Q VA mv hm I Ho I m H . MH.I MM.I waol Hv. thol mflol E®¥m CH SOHNUW mN.I oH.I mm.I mH. mm. me. boos NH noNNum mm. NH. mo.I ma. mm.l mm.l Mama EH Hmm5m mmhm mm.I mm.I won.l no. ma. HA. Ewum :H Howsm mmum av Hm. m¢.| Ha. H¢.I mo. uOOH CH ummdm mmum mmmum mcHHHHm com be .H mudom ma musom mH mudom m musom ma mudom MH musom w HOHMMM®M mhmuomumno moom mHuHDB Monam mgvmsmHNmo m Hoods E30H0 mHN>HuH50 A.H mHHNmHs> msHommmamv smwaHo 03$ map mo mmsmmfie m>aumumwm> may sH waHCNnOQNNo memHHN>¢ can scammflombs tom mo mmmuswoumm smmzumm mucwHOHmmmoo coaumHouHoo mmflfie REFERENCES l. Eaton, F. M. and D. R. Ergle. 1953. Relationship of seasonal trends in carbohydrate and nitrogen levels and effects of girdling and spraying with sucrose and urea to the nutritional interpretation of boll shedding in cotton. Plant Physiol. 28: 503-520. 2. Flinn, A. M. and J. S. Pate. 1970. A quantitative study of carbon transfer from pod and subtending leaf to the ripening seeds of the field pea (Pisum arvense L.) J. Expt. Bot. 21: 71—82. 3. Guinn, G. 1974. Abscission of cotton floral buds and bolls as influenced by factors affecting photo— synthesis and respiration. Crop Sci. 14: 291-293. 4. Greenwood, E. A. N., P. Farrington and J. D. Beresford. 1975. Characteristics of the canopy, root system and grain yield of a crop of Lupinus angustifolius cv. Unicrop. Aust J. Agric. Res. 26: 497-510. R. S., R. L. Matlock and C. Hobart. 1933. Physiological factors affecting the fruiting of 5. Hawkins, cotton with special reference to boll shedding. 46: 361-407. Arizona. Agri. Exp. Sta. Tech. Bull. 6. Hicks, D. R. and J. W. Pendleton. 1969. floral bud removal on performance of soybeans. 9: 435—437. Effect of Crop Sci. G. Reid. 1952. Analytical 7. Laidlaw, R. A. and S. studies on the carbohydrates of grassland clovers. I. Development of methods for the estimation of J. Sci. Fd. free sugar and fructosan contents. Agric. 3: 19—25. 8. Loomis, W. E. 1926. A study of the clearing of alcoholic plant extracts. Plant Physiol. 1: 179-189. 89 — m, 1::1. q _ 90 Growth and abscission in Sea Ann. Bot. 36: 457—483. Fruit abscission in cowpea, J. Expt. Bot. 23: 9. Mason, T. G. 1922. Island Cotton. 10. Ojehomon, O. O. 1972. Vigna unguicuiata L. Walp. 751-761. 1969. Removing and analyzing total non— ll. Smith, D. structural carbohydrates from plant tissue. Research Report #41. University of Wisconsin, 12 pp. Smith, D. and L. F. Graber. 1948. top growth removal on the root and vegetative J. Amer. development of biennial sweet clover. 40: 818-831. 1976. The influence of 12. Soc. Agron. Subhadrabandhu, S., M. W. Adams and D. Penner. Abscission of reproductive structures in dry bean. 13. II. Effects of daylengths on growth and pod abscission in Phaseolus vulgaris L. Agronomy 77. 14. Van Schaik, P. H. and A. H. Probst. 1958. Effects of some environmental factors on flower production and reproductive efficiency in soybeans. Agron. Abstracts, p. J. 50: 192-197. 15. Van Steveninck, R. F. M. 1957. Factors affecting the abscission of reproductive organs in yellow lupins (Lupinus luteus L.) I. The effect of dif— ferent patterns of flower removal. J. Expt. Bot. 8: 373—381. 16. Wadleigh, C. H. 1944. Growth status of cotton plant as influenced by the supply of nitrogen. Sta. Bull. 446: 1—138. Arkansas Agr. Exp. 17. Weinmann, H. 1947. Determination of total available carbohydrates in plants. Plant Physiol. 22: 279-290. 18. Wien, H. C., S. L. Altschuler, J. L. Ozbun and D. H. Wallace. 1976. l4C-assimilate distribution in Phaseolus vulgaris L. during the reproductive period. J. Amer. Soc. Hort. Sci. 101: 510-513. E. W. and A. J. Willis. 1954. Stomatal move- ments and changes of carbohydrate in leaves of 53: 373-396. 19. Yemm, Chrysanthemum maximum. New Phytol. CHAPTER 5 ABSCISSION OF FLOWERS AND FRUITS IN PHASEOLUS VULGARIS L. IV. GROWTH AND POD ABSCISSION AS AFFECTED BY CARBON DIOXIDE LEVELS Abstract Abscission of young pods was studied in the green- house in two Phaseolus vulgaris L. cultivars over two Plants were grown under 300 (ambient air) and seasons. 800 ppm carbon dioxide after their flower buds became Visible. High carbon dioxide level reduced pod abscis— sion, increased plant size and seed yield. The relation- ship between pod abscission and growth is discussed. 91 ‘ 92 Introduction Since the report of Wittwer (5) on increasing crop yield by carbon dioxide enrichment, numerous reports have confirmed his observations. Yields of field—grown soybean have been increased nearly 30% by carbon dioxide enrichment (1,200 ppm) (4), as a result of both an increase in number of pods filled and a decrease in pod abortion. In cotton an increase in carbon dioxide concentration in the atmosphere decreased abscission of floral buds and bolls (3). In barley (2), rice (6), and soybean (4) increasing the carbon dioxide concentration during the reproductive phase increased yield. Growing dry bean plants under long photoperiods after flowering increased yield (see Chapter 3). This was associated with less pod abscission and larger plants. The study reported here was designed to determine the effects of increasing carbon dioxide levels during the pod development period on growth and pod abscission of dry beans. Materials and Methods Two dry bean cultivars, "Seafarer" and "Black Turtle Soup," were grown in the greenhouse at East Lansing in the spring of 1975 and 1976 (for procedures, see Chapter 3). When the plants reached the flower initi- ation stage, 30 of each cultivar were placed in each of two clear polyethylene chambers (7.2 by 3 by 3 meters). 93 In each chamber air drawn in from one end was released at the other end. Carbon dioxide was fed into the mixing chamber of carbon dioxide and air. The gas mixture was introduced into one chamber with a fan at the rate of 148 cubic meters per hour. The concentration at the plant level was maintained in the range of 750 to 850 ppm, as maintained with an infra—red gas analyzer. This was continued for 40 days. Ambient air was blown into the second chamber at the same rate. The carbon dioxide concentration was in the range of 300 to 350 ppm. Three harvests were made, pod abscission and growth were measured as before (Chapter 3). Results and Discussion Pod Abscission Plant subjected to a high carbon dioxide level produced more flowers and retained more pods than the control (Table 1). Response was similar in both cultivars (Table 2). Data for both 1975 and 1976 showed the same trends (Table l). Pod abscission was reduced more by carbon dioxide level in Black Turtle Soup than in Sea— farer (Table 2). This was associated with larger plant (Table 3), more leaves, greater leaf area and leaf weight per plant in Black Turtle Soup (Table 4). Pod abscission was not recorded at peak flowering (10 days after flower initiation). At pod filling stage .uwme meNm mamfiuasz N.ENUGSQ Na Hw>w NHquOHMHGon boa NHN muwupma HNHHEHm Nb NNBOHHOM HouoENHNm oENm may samuas quwz . N H WM 63“ #m “Gwhmwwwfi .m.: .9: NE NE NE .mé HHH x HH x H N .m.c .m.E .m.c .m.c .m.c HHH x HH .m.: NMNHH NWoC ¥¥ umod— oMoHH HHH um H .m.fi .m.E «% «s .w.G « HH x H mmmmmmmmmmmm x «:8 x a.mm N m.HH N NNH N NNH N N.NH Nam cow N m.mw N m.vv x o.w x m.m x v.0H x m.vH Emu oom HN>NH Noo .HHH a «.mm c m.vv c o.HH E m.va : m.mH : w.HN HNHNmNNm E m.om E m.Hm E m.m E m.m E m.m E m.oa msom mHuHSB HONHm . NN>HHH5 .HH n m.Nv b H.Hv N m.N N w.m b m.mH N N.ma NuflusuNz N v.mm N H.mm N N.m b m.HH N a.mH N m.mH mcHHHHw com I I b m.OH o m.vH N m.NH N m.oH mcfluwonm wam mmepm HNuEmEmon>ma .H man mbmH mhma mhma man mnma commmflomnd w moon .oz muwzoam .oz Mmcommwm 03B 02». HGUGD ECHO mHN>HuH50 stm Nun 039 EH coammfiownm mo mmNucoouwm ocN mmom Mo HNQEEZ .mHOBOHm mo HwnEsz so uowmmm mHm>mH moflxoflo EOQHNU psN quEmon>wQ pom mo wmmNum H wand? ”I v " .bmme onNm meNbHDE m.bNoEso Nb Hm>ma w Iamacmam uo: NHN mumbbwa HNHHEHN Nb UNBOHHOM HwwaNHNm sw>fim N cabeB mcmwz - n n I m a wbu uN ucmnwmwfip NaucNu H hm.mw b mN.vm H H.NH o N.MH m a.mm U m.mm HmbNmNmm m NN.NH N om.m N o.m o N.HH v m.HH b m.HH msom NHHNNN MONHN oom m mm.mw o mm.mm c m.n b H.w H m.mH o 0.0m HNHNMNwm a mo.Nm N NN.Nm m H.N N m.m m N.m N m.m Enom NHNNNN HONHm com mnma mbmH man mhma mhmH man HEmmv me>wH HN>HuHso ECHmmHomb< oom w bNNHm\moom .oz bsNHm\mHN30Hm .oz NNHxOHo NObHNU NHmmeum mcwumm>HNb HAN bN mstE wHN Nprv mnemem 039 mbb moons QBOHw mHN>HuHSU cNmm Nun 039 GM EOHNNH0mb< pom mo meucwoumm UEN .pmcHmem mpom wo HwbEsz .mumsoam mo umbEsz so me>wq onxOHo EObHNo mo mbommwm N magma 96 .bmwe mmst mHmHuHsz m_cNoc5Q Nb Hm>mH NH mbb bN pcmhmmeU NHpENo IHMHcmHm boa mHN muwubmH HNHHEHm Nb UNBOHHOM HmumENHNQ Em>Hm N EHbuHB mENNEN N N.N n N.HH a N.H b m.H N N.H b N.H NNNNNNNN m H.oH o a.mH N N.N o m.m N H.m o N.H msom NHNNNH onHm oom m m.m N N.N m N.o N N.H a N.o N o.H NNNNNNNN a m.m N o.N m o.H N m.H N N.H N o.H muom NHNNNN onHm com NNNH mNmH NNmH mNmH NNmH mNmH HN>HbHDU HEmmV me>mH Hoe Ame Hue NNHxOHo NObNNo .Hs NNNHN HNboa ucNHm\.us swam NNNHN\.us boom Nflmmmme msHbmm>HNb HHN uN mcmoE NHN NHNUV mEONNwm 039 wbu Hobbs Ezouw mbN>HuHDU chm NHQ 039 EH bbmez chHm HNuOB UEN Ewbm .boom mo HENHm Hum bbmHmz NHQ so mHm>wH wUHxOHb EObHNU mo muowmmm m NHNNH 97 .bmmB mmbmm meHbHsz N.ENOEDQ Nb Hw>wH NH mbb bN ucmswmwao NHucNo IHMHcmHm boa mHN mumbwa HNHHEHm Nb pmsoHHom HmmeNHNm sm>HN N bebHS mENwz. . . . N IIIIIIIIIIIIIIIIIIIIII N N.m o N.m N «H N NH N mas N NNN NNNNNNNN m m.m N o.m H NH b NH N MNOH b omm msom NHHNNN MUNHm oom m m.H N o.m m OH N MH m Nwm N mmm HNHNMNwm N m.m b N.N m HH N HH m ONN N NNN msom NHHNNN onHm oom mNNH mNNH mNNH mNNH mNNH mhmH HEmmV mHm>wH HN>HbH50 Amy ubNHm ubNHm\MNmH HNEOV prxOHD EObHNU \bbmez MNNH mbNHHOMHHB HmbEdz uENHm\NwH< MNmH Nfimmebm mbemwbuNb HHN bN wENmE mHN NbNUV mcowNwm 039 mbb Amoco szonw mHN>HuHSU cmwm NHQ 039 EH bENHm Mom bbmflmz MNwH UEN ucNHm me “Nob mo HwbEsz .bENHm Ham qum MNNH so me>mH OUHNOHQ EObHNU mo mbommmm N NHNNN 98 and at maturation, high carbon dioxide reduced pod abscission in both cultivars (Table 1, Appendix C tables C-1 and C-2). About half of the pod abscised at pod filling stage in Black Turtle Soup under the control treatment, but only one-third were lost at this same stage when this cultivar was grown under high carbon dioxide (Table C—l). However, for Seafarer, a cultivar with a high abscission level, about two-thirds of pod loss occurred at the pod filling stage when they were grown under ambient carbon dioxide. This ratio was decreased to one—half when high carbon dioxide level was supplied to the plants (Table C-l). Similar results were obtained in 1976 (Table C-2). Two interpretations are offered for these results. First, high competition for carbohydrates occurred during the early stages of pod development, and this competition will determine the amount of pods to be retained. This was supported by the high portion of pods abscised at pod filling in relation to that at maturity when plants were grown under a low carbon dioxide level. The second explanation was shown in the drop of this ratio of pod abscision at pod filling and at maturity with carbon dioxide enrichment. This indicated that more carbohydrate was made available under a high carbon dioxide regime for feeding young pods at this stage. Percentage of pod abscission obtained by carbon dioxide enrichment was similar to that obtained by increasing daylength, as reported earlier (Chapter 3). Leaf Development With high carbon dioxide levels more leaves per plant were obtained. This resulted in greater leaf area and higher leaf weight produced by the plant (Table 5). With a low carbon dioxide level there was no significant difference in number of leaves and leaf area per plant of the two cultivars, but when the plants were subjected to the higher carbon dioxide level cultivar differences in number of leaves and leaf area were obtained. Black Turtle Soup exhibited greater response to increasing carbon dioxide than Seafarer (Table 4). This response occurred in both the 1975 and 1976 experiments (Table 4). This high response to increasing carbon dioxide level in Black Turtle Soup can be related to its growth habit. Black Turtle Soup is a semi-vine bean and the plant can still make some vegetative growth after flowering. Therefore, when more carbohydrate was synthesized under with a high carbon dioxide level, vegetative growth may also be promoted and this resulted in more leaves being produced. For Seafarer, a determinate type, vegetative growth does not continue much after the plant reaches the reproductive phase, therefore, more carbohydrate pro— duced by carbon dioxide enrichment did not result in more leaves being produced (Table 4). However, the high carbon dioxide treatment did result in lower percentage of pod abscission. A negative correlation between percentage Table 5 Stages of Pod Development and Carbon Dioxide Levels Effect on Number of Leaf and Leaf Area per Plant in Two Dry Bean Cultivars Grown Under the Two Seasonsa Leaf Area/ NO Leaf Plant (cmz) 1975 1976 1975 1976 I. Developmental Stages Peak flowering 15.8 b 10.7 a 742 a 549 a Pod filling 12.6 a 12.9 b 756 a 716 b Maturity - - - - II. Cultivar Black Turtle Soup 15.2 m 12.3 n 799 m 732 n Seafarer 13.3 m 11.3 m 699 m 533 m III. CO2 Level 300 ppm 12.2 x 10.2 x 663 x 381 x 800 ppm 16.2 y 13.4 y 835 y 883 y Interactions I x II * ** n.s. n.s. I X III n.s. ** ** ** II X III ** -k ** ** I x II x III * n.s. n.s. n.s. aMeans within the same parameter followed by similar letters are not significantly different at the 1% level by Duncan's Multiple Range Test. 101 of pod abscission and leaf area per plant was also noticed in both cultivars under both levels of carbon dioxide (Table 6). However, at 300 ppm carbon dioxide, at which leaf area may be more important in supplying carbohydrate for pod retention, a highly significant cor— relation occurred. This significant correlation was seen in the indeterminate cultivar, Black Turtle Soup. In Seafarer, the determinate type bean, no significant cor— relation between leaf area and percentage of pod abscis— sion was found. At the high carbon dioxide level (800 ppm), more ideal for photosynthesis, leaf area per se may not be as critical for supporting the young pods, therefore, no significant correlation between leaf area and pod abscission was found (Table 6). The number of leaves per plant was significantly lower at the pod filling stage as compared to peak flower- ing (Table 5). This was due to the loss of some old leaves at pod filling. However, leaf area and leaf weight per plant were not significantly different at these two stages. This indicated that very little or no leaf growth occurred after peak flowering in 1975. This was in con— trast to the 1976 data where there were indications of leaf growth after this stage (Table 5). Plant Development Greater growth and larger plants were observed with the carbon dioxide enrichment treatment. Increase .HNNNH NH HN HNNNHNHNNHNN .HN>NH Nm NN NNNNHNHNNHNN IIIIIIIIIIIIIIIIIIIIIIIIIIIIIII NNHN MNNH NH.I NN.I NN.I NNN.I mo. mo. no.1 mm.l Hmbfidc Mmmq we. Nm-I mm6| nowcl ugmflwg “mug m H.H.l MN.I me.l mo.l #SWHQ? EOQm NN. NN.I mm.I NNN. NNNHNN Noom moo ENE N N N com 00 ENE com 00 ENE com 00 5mm oom mumbONHNbu uwHNwNwm muom meHdE NUNHm HNmNum NGHHHHM pom uN smeu Nprv NEHH030HN Hound mHm>mH mpHxOHQ EObHNU bENHNMMHQ 0b Umbownbnm mHN>HbH50 ENmm NHQ 03B EH mumbONHNbU bu3ouo bwbuo NEN ECHmmHombm pom m0 mNNucwoumm E003bwm mbcmHonmmoo EOHbNHNHbou 9 meNB 103 in root, stem, leaf and total plant weight occurred in both cultivars (Table 3) in both years of study. The increase in vegetative growth with the high carbon dioxide level in both cultivars was associated with a higher number of pods retained (Table 2). Black Turtle Soup produced more dry weight in the vegetative organs than the Seafarer (Table 3). The greater growth response with high carbon dioxide enrich— ment was also evident by reduced pod abscission in Black Turtle Soup. Whether the higher vegetative weight deter— mined pod abscission was not known, but the data Show a relation between these characters (Table 6). Total plant weight was greater with the carbon dioxide enriched treatment after flowering, while under the ambient carbon dioxide level this weight was decreased (Table 2). This may be due to the loss of senescing leaves at maturation. The slightly higher total plant weight at maturity under high carbon dioxide enrichment was due to the increased weight of reproductive organs (seeds and pods). This was also seen in decreased weight of root and stem (Table C—4) from peak flowering to maturation. This loss in vegetative weight compensated for an increase in reproductive weight. This dynamic situation in weight allocation affected the yield of a plant. Competitive ability of various organs at any developmental stage of plants grown under a particular environment would undoubtedly influence pod abscission. Seed Yield Plants growing under the high carbon dioxide level (800 ppm) produced more mature seeds. This was seen in both cultivars (Table 7). The more seed produced, the greater the seed weight per plant. The high number of seed produced under the high carbon dioxide level resulted in slightly smaller seeds produced in 1975 (Table 7). This may have been due to the competition between the more numerous seeds in the pods. However, this seed size difference was not observed in 1976 (Table 7). Cultivar differences in seed yield existed in response to increasing carbon dioxide concentration. Under the high carbon dioxide level, Black Turtle Soup produced more seed and had higher yield than Seafarer in both years (Table 7). This greater response by Black Turtle Soup was also seen in vegetative growth and pod abscission. The correlation between percentage of pod abscis- sion and other reproductive structures at pod filling was given in Table 8. At the ambient carbon dioxide level, the number of flowers produced in both cultivars was positively correlated to percentage of pod abscission. This suggested that under this carbon dioxide level at the pod filling stage, competition for carbohydrate occurred between the flowers and young pods. The more reproductive organs, the more competitive force and the .amms wmcwm mamauass m_:moqsa an am>ma ma may am uqmammmam maacmo Hm maoaama HMHHEam ma posoaaow Hmumfiwamm 08mm may gflnuaz msmozm uamacmam poo o m ma.o m ma.o a a.m o m.m a an n mm awamwmmm a ma.o m ma.o m a.a o a.m H mm 0 mm muom mauass somam mom 5 a ma.o gm ma.o a a.m m m.m a am m ma “manawwm 0 1 a ma.o n aa.o a o.m n a.« a mm m mm anew manage somam com mama mama mama mama mama mama Amv Amy Hm>auaoo flammv mam>ma unwam\momwm .oz moaxoao sonamo comm\unmaw3 unmam\.p3 comm mammmmum msapmw>amn Ham um momma mam mumov msowmom 039 swoop cacao mam>auaso comm man 039 Ga comm moo mo unmawz com “swam Mom unmaoz comm .psmam Mom mpomm mo awnEsz so mHo>®a moaxoao doaamo mo muomwmm h wanna 106 .am>ma ma um acmoamacmamn .am>ma mm am acmoaaacmamm av.| am.l mm.| nab. pnmawz comm me.l aw.| am.| woa. mvwom mo umnEdz ma.| mm.| av.| mv. mpom mo Hmnfidz new. nvv. Ha. 9mm. mum3oam mo Hmnfidz Mmm.l mm. mm.| Mam. poaamm moauosoam suausums pa .aa ma. mm. mm. nmm. psmaos owmm oao. 00.: aN.| we. mommm mo umnsdz m¢.| am.| am.l mm.u wpom mo Honesz an. 0mm. wN.I th. meBOHM m0 Hwnfidz mom. ma.| ma.l om. coanmm mqauozoam ommpm mcaaaam com pm .a N8 2mm com Noo Ema com Noo Ema mom Noo Ema com mamuomamno Housmmom mdom meHSB xomam unauwsoam Momma maw>ma opaono conamo usmuommflo on pouowmnsm mum>auaso comm wan 039 ca muouomamzu o>au05poammm Honuo pom soammaomné pom mo ommucooamm cwm3uwm mudoaoamwooo soaumamaaoo w magma 107 more they would abscise. However, when the plants were grown under the high carbon dioxide level, a negative correlation was seen in Black Turtle Soup while the posi— tive correlation was still observed in Seafarer (Table 8). The negative correlation in Black Turtle Soup may have resulted from a greater vegetative growth response by this cultivar to the higher carbon dioxide level. Therefore, flowers and young pods had a greater share of the assimilate produced, thus fewer pods would have to sacrifice themselves by abscissing. However, for Seafarer which is a determinate plant, vegetative growth did not occur after flowering, the plants exhibited less growth response to the increased carbon dioxide level. Also this cultivar produced many flowers in a short flowering time as compared to Black Turtle Soup (see Chapter 2). Thus the demand for food from these flowers and young pods was made in a short time period; even if plants had grown larger under the high carbon dioxide, the increase in growth may not have been sufficient to meet the demand from those flowers and pods. Therefore, a high percentage of pod abscission still occurred as more flowers were produced. Negative correlation between percentage of pod abscission and yield (seed weight) at maturity indicated that as percentage of abscission went up lower yield resulted. This was seen in Black Turtle Soup grown at 108 300 ppm carbon dioxide and in both cultivars at the 800 ppm carbon dioxide level (Table 8). Although pod abscission can affect seed yield, in dry beans there are many components affecting yield (1). Thus, non- significant negative correlations under these conditions may be explained. It is possible that percentage of pod abscission might be significantly correlated to any one of the yield components instead of total yield in this case. The significantly positive correlation of 0.77 between percentage of pod abscission and seed yield in Black Turtle Soup grown under ambient air (300 ppm carbon dioxide) may be explained as follows. The limited photosynthesis may have been insufficient for retaining many pods. Thus the competition among pods for growth could result in a condition that the more pods abscised the greater the chance for the remaining pods to grow. The previous study of cultivar response to increasing daylength showed positive response to day— length in both cultivars, but Black Turtle Soup seemed to exhibit a greater response than Seafarer (Chapter 3). A similar result was also found when these two cultivars were grown under high carbon dioxide concentration. These two experiments pointed out two things. First, Black Turtle Soup had greater response when grown under conditions favoring photosynthesis after flowering. The second was that since both extending daylength and 109 carbon dioxide enrichment gave similar results in pod abscission, seed yield, and growth rate, there must be similar physiological responses of plants that result from these two environmental factors. These physiological responses may be responsible for determining the abscis— sion capacity of the plants. If that physiological factor is not carbohydrate availability, then it must be some factors influenced by or closely associated with the levels of carbohydrate. REFERENCES Adams, M. W. 1967. Basic of yield component compen— sation in crop plants with special reference to the field bean. Phaseolus vulgaris L. Crop Sci. 7: 505—510. Gifford, R. M., P. M. Bremner and D. B. Jones. 1973. Assessing photosynthetic limitation to grain yield in a field crop. Aust. J. Agric. Res. 24: 297-307. Guinn, G. 1974. Abscission of cotton floral buds and bolls as influenced by factors affecting photosynthesis and respiration. Crop Sci. 14: 291—293. Hardman, L. L. and W. A. Brun. 1971. Effect of atmospheric carbon dioxide enrichment at dif- ferent developmental stages on growth and yield components of soybeans. Crop Sci. 11: 886-888. Wittwer, S. H. and W. M. Robb. 1964. Carbon dioxide enrichment of greenhouse atmospheres for food crop production. Econ. Bot. 18: 34—56. Yoshida, S., J. H. Cock and F. T. Parao. 1972. Physiological aspects of high yields. In "Rice Breeding" IRRI, Los Banos, pp. 455—468. 110 CHAPTER 6 ABSCISSION OF FLOWERS AND FRUITS IN PHASEOLUS VULGARIS L. V. RELATIONSHIP OF POD ABSCISSION TO DIFFERENTIAL LEVELS OF CARBOHYDRATES PRODUCED BY VARIATION IN CARBON DIOXIDE CONCENTRATION Abstract Levels of free sugar, starch and total non- structural carbohydrates were determined in two dry bean (Phaseolus vulgaris L.) cultivars grown under ambient (1}300 ppm) and enriched (£:800 ppm) level of carbon dioxide. Free sugars were higher in both vegetative (root, stem, and leaf) and reproductive (seed and pod wall) tis— sues in both cultivars grown under high carbon dioxide, while starch concentration was higher only in the vegeta— tive tissues. Black Turtle Soup (indeterminate) contained significantly more starch in the vegetative tissues, but not in the seed, than did Seafarer (determinate). Free sugar and starch decreased at maturity in the vegetative tissues, but not in seed, where most of the carbohydrate was stored as starch. A shift of available carbohydrates from the vegetative tissues and the pod wall to the seed lll 112 occurred with maturation. The role of available carbo- hydrates in pod abscission, seed yield, and vegetative growth is discussed. 113 Introduction An extensive review article by Wittwer and Robb (5), emphasizing tremendous increases in crop production obtained by carbon dioxide enrichment of greenhouse atmospheres, aroused the attention of crop physiologists in the early sixties. Carbon dioxide enrichment has since been reported to increase yield in soybean (l, 3), wheat (4) and cotton (2). Our previous studies with Phaseolus vulgaris L. showed that growth rate, seed yield, and pod retention could be increased by raising the ambient carbon dioxide concentration (see Chapter 5). The objective of the present study was to determine the effects of such treat- ment on carbohydrate concentration of various tissues. Materials and Methods Sample Preparation Two dry bean cultivars, "Black Turtle Soup" (indeterminate) and "Seafarer" (determinate), were grown and treated with two carbon dioxide levels as previously described (see Chapter 5). Harvesting times, handling of samples during har— vesting, preparation of samples, and analysis of free sugars and total nonstructural carbohydrate has been described elsewhere (Chapter 4). Free sugar, starch, and total nonstructural carbohydrate concentrations are expressed as mg glucose equivalent per g of dry tissues. The t (plar Free free cult: free hows the Thea Seaf and Soup but atp was acti stag the Cart (Fig hch POd 114 The data were analyzed factorially, using 10 replications (plants) per treatment. Results and Discussion Free Sugar Increasing the carbon dioxide level increased the free sugar concentration in all tissues analyzed for both cultivars (Table 1). Black Turtle Soup retained more free sugars in the root, stem, and leaf than did Seafarer; however, the reverse occurred in seeds and pods, although the difference was not significant (1%) in pods (Table 1). These data indicate a stronger sink effect of seeds in Seafarer than in Black Turtle Soup. No interaction was observed between cultivar and carbon dioxide level except in the leaf. Black Turtle Soup leaves contained more sugar at 300 ppm carbon dioxide, but no difference was evident at 800 ppm (data not shown). The free sugar levels in all tissues were high at peak flowering and decreased as the pods developed, as was seen in a previous study (Chapter 4). Several inter— actions were noted between carbon dioxide level and growth stage. As the pods matured, the free sugar level in the stem and leaves decreased at a faster rate at the low carbon dioxide level than at the high carbon dioxide (Fig. 1A and 1B). These results are consistent with the hypothesis that available free sugars are limiting during pod formation and filling. The free sugar level in the 115 Iwaemam .pmoa omcmm mamanadz m.nmocso ma ao>ma ma man an unoummwac ma non mum muwuuma HmaaEam ha UwBOHHOM aoumfimamm oEMm msu canvas mammzm .Uom Eoum muwammom no: pmwmn wanna [Illvll‘l HHH x HH x H unmaoz who @ Mom meOSHO m2 ** * .mlq ** 0mOC .m.c .m.q as .m.c .m.q aaa x Ha s ** .m.d HHH N H ow.C cm..—H omwm omuwm .muflH HH x H Illlllllllll mcoauowuoch a ama a Noa a a.mm a m.mm a m.mm and mom x mNH x mm x a.mm x m.mv x m.mH 8mm oom am>mamoo .aaa E mva c aw E m.mw E m.w¢ E «.ma anumammm E ama E em G v.ma : m.mm c N.vN mdom manage Monam mam>auaso .HH m a.am m.ow I m m.mm m m.om wuausumz n o.aaa m.om m «.ma n N.mm m a.ma meaaaaw pom no a.am~ . m a.mm o a.mm n m.m~ mcauwsoaa xmmm «gas .H pom Comm mama Ewum uoom mwum>HuHsU cmom 038 mnu mo mpumm unmam mdoaum> Ca :Oaumau Icoocoo Hmmnm wmam no mam>ma moaxOHQ Conamu paw mmmum amuswEQOHmwmo mo muoomwm one a magma 116 40%— A o- ----- 0 Black Turtle Soup \ ‘-——-‘Seafarer 3O 20 E >. 5 10 a \ v 3 07 l l l 3 L 10 B 20 30 4O .3, 300 //°\\\ o------oBlackTurHe Soup 2 // \n\‘1<:f———oSeaiarer / / \\ 200- / \\ / \ 5 \ \ \ 100'— \‘o l l l 0 1O 20 30 40 Days after flower initiation Fig. 1. Levels of starch in A. root; and B. stem; of two Phaseolus vulgaris L. cultivars during their repro- ductive phase, averaged from the two carbon dioxide levels. 117 leaves of plants exposed to 800 ppm carbon dioxide increased between peak flowering and pod filling (Table 2). The level of free sugar in flowers and newly set pods (seed could not be separated at this stage) was high under both the high and low carbon dioxide treatment at peak flowering but decreased sharply with maturation (Table 2). High carbon dioxide significantly increased seed free sugar concentration at all developmental stages. Free sugars in seeds dropped between pod filling and maturity under the high carbon dioxide treatment, but increased slightly during the same period at the ambient carbon dioxide level (Table 2). Greater pod retention in the high carbon dioxide treatment (Chapter 5) probably created greater competition for sugar among seeds, result- ing in a decline in free sugar level from pod filling to maturity. Much pod abscission occurred under the ambient carbon dioxide level and fewer pods and seeds were retained (Chapter 5). This reduced competition and prevented a decline in concentration in the seeds. Free sugar content of pod walls decreased with maturation under both carbon dioxide levels (Table 2). Starch High carbon dioxide increased starch concentra— tions in vegetative tissues (root, stem and leaf), but decreased them in the seed and pod wall (Table 3). Starch 118 .pom anw mamammom no: comma #0: .ume omsmm mamapasz m.awoado an Hm>ma ma mfiu um ustwMMHU handsommaqmam mam maouuoa amaafiaw an owsoaaow amumsdamm meow mnu manuas memos m IIIIIIIIIIIIIIIIIIIIIIIIIIIIII Q N.mv Q m.mw I O a.mm O . . D H vN ow U N.mNH O m.mHH w N.mm O h.Nm Q ¢.HN ON M w Hmm I O m.v> w G.Nh O H.mN OH I I a a.mm o m.ma am m.om o mom 6 HHmN m m.mh I m b.mH w b.hH ow o h.vca m m.vm m m.mm Q m.m¢ w v.mH ON Qm m mvN I Q m.vm 0 m.mm 0Q h.NN OH I I v a.mm w m.mh QM m.ON 0 com IIIIIIIIIIIIIIIIII com comm mama Emum uoom Ameov “Emmy am>ma SOHflwHuHGH H630Hm TGHNOHQ GOQHmO moSmmaB aoum< mama . . mwSmmaB Gwom mo aunmaos who m\mmoosam may coaumauswosoo ammnm mosh no mcaamfimm mo oEHB tow wpaxoao conumo mo mpowwmm N magma 119 .pom anm oumammwm no: boom a .umwa wmqmm mamauadz n.smoodo ha Hm>oa wa map um unwammmap hauomo lamaamam uos who mamuuma Hmaafiwm ma pmsoaaom kumfimumm GEMm Gnu casua3 mammzm .m.s .m.q aa a .m.: HHH x HH x H a .w.: am as .m.s HHH x HH .3. a; «L. as a HHH x H .m.d .1 .m.c ta. a; HH N H mGOHpomawuoH x mma x aam a «mm a oaa a a.mm and mom a cam a 0mm x mma x mma x a.ma Edd oom aw>ma Noo .Haa s oma E mom a mam s m.oa s m.ma awammmmm a mom 5 aom a mam : mam a m.om dsom manage somam mHM>a¥adU .HH m o.mm m mom I m N.am m a.v muausumz o mom n mam m mom a maa o o.mm maaaaam com an oma I n mmm n mma n m.am msaawzoaw xmwm msae .a com omwm mama swam uoom unmawz who 0 mom ustm>stm wmoosao m2 mmam>aua50 cmmm man 039 mcu mo muamm udmam msoaam> ca coaumuucwocoo moamum so waw>oa opaano sonamo cam wwomum amucmfim0ao>oo mo muommmm m THQMB 120 accumulation was greater in the vegetative organs and pods in Black Turtle Soup than in Seafarer, however, no dif— ferences were evident in seed (Table 3). No interaction was seen between carbon dioxide levels and cultivars in root starch concentration (Table 3). Although starch concentration in the stems increased significantly with increasing carbon dioxide concentration in both cultivars (Table 3), the increase was not significant in Seafarer (Table 4). Starch concentration was consistently low in Seafarer stems even under field conditions; this may be characteristic of the determinate growth habit. Carbon dioxide enrichment markedly increased starch accumulation in leaves of both cultivars (Table 4). Interaction was again significant (Table 3), with a 4-fold increase in Seafarer as compared with a 3—fold increase in Black Turtle Soup (Table 4). Carbon dioxide—cultivar inter— action in seed starch concentration was nonsignificant (Table 3). The concentration of starch in the vegetative tissues decreased with maturity (Table 3). This decrease, especially in stems and leaves coincided with an increase in starch concentration in seeds and pod walls. Starch concentration in all tissues was lower at maturity than at pod filling (Table 3), possibly due to hydrolysis. Significant interactions occurred between culti— vars and starch concentration in roots, stems and seeds I. ‘ _ "f - '- .ummB wmcmm mamapasz m.cmocdo an am>ma ma on“ as #swammmap mausmoamacmam poo mam mawupoa awaaEHm Spas Aumx .onmv mumw paw mQESHOU canaas msmozm x a.mma x m.mam a m.a~m a N.oaa a a.mm cams m a.aaa m a.mam o m.mmm a m.aa a m.ma amamammm n m.ama m o.a~m e a.mmm o o.mmm o m.mm snow manage somam mom 1 n a N.oam a m.mm~ x m.mma x m.-a x a.ma saw: a m.mom a a.mmm m a.mm m m.mm m a.aa amamammm a m.aam a a.mmm n m.mma n a.mma m a.ma msom manage Momam mom eom emmm mama swam poem am>apaso lease am>ma mdmmHB . OUHXOHQ GOQHMU Mmosmmae zoom ca Annmamz map m\omoosam mEv soaumausoosoo nonmum do Hm>auaso can moo mo muoommm w GHQMB 122 during the reproductive phase (Table 3). In roots, the starch concentration was higher in Black Turtle Soup at all developmental stages except maturity (Fig. 1A), but the difference was minimal at peak flowering. On the other hand, the difference was maximal at this time in the stem (Fig. 1B). In both cultivars, the starch levels in roots and stems decreased as the seeds matured (Table 3). In leaves there was no interaction between cultivar and growth stage during pod development (Table 3). As the pods developed, the starch concentration in leaves decreased (Table 3). Cultivar-developmental stage inter— action on seed starch was shown in Figure 2, where starch concentration in seeds of both cultivars increased from peak flowering to pod filling, then decreased at maturity (Fig. 2). Interaction between carbon dioxide levels and stage of pod development on starch concentration was noted (Table 3). In root, stem and leaf, carbon dioxide enrich- ment increased starch accumulation (Table 5), but response varied considerably with time. However, in seed, carbon dioxide enrichment decreased starch concentration regard— less of the stage of pod development (Table 5). The greater number of seeds produced apparently reduced the starch available for storage in each seed. The rapid decline in starch concentration in the pod wall at maturity (Table 5) paralleled data obtained in a previous 123 400'— 0.----0 Black Turtle Soup o————4 Seafarer 3300— Z‘ 'a a) \ a 3 E 6’200--- a: E A: I | I l 0 1O 20 30 40 Days after flower initiation Fig. 2. Levels of starch in seed of two Phaseolus vulgaris L. cultivars during their reproductive phase, averaged from the two carbon dioxide levels. 124 .ummB mmsmm mamauasz w.oaosda kn Ho>ma WA on» no “soHQMMHU waucmoflmasmam poo mam maopuoa amaafiam >9 pascaaom Honoamamm mean any casuas mcmozm m m.om m m.mmm I n m.ama am m.a om a a.mam n m.amm a m.mmm a m.aam a a.mm ON n m.ama I m m.ama a a.mma o a.am oa I n a.mma n m.am a m.am o mom I m m.am m o.~ om a m.ama o a.mom m m.mm o m.mma 0 «.mm on o a.mom I u a.mmm a m.ama n o.ma oa I n a.mma n m.am a m.am 0 com mom owmm mama swam uoom imamov : madmmaa Hmumd mafia . . amosmmas swam mo Annmaos who m\omoosam may coaumaucoocoo aoaaum do msaamaam mo oEHB can opHNOaQ conamo mo mpoommm m manna 125 experiment (Chapter 4), and suggests rapid utilization of starch from the pod wall by the growing seeds. Relation of Pod Abscission to Available Carbohydrates The data presented in Chapter 5 showed that carbon dioxide enrichment during the reproductive phase increased plant size, seed yield, and pod retention. In this study, using the same growing conditions, increasing the carbon dioxide concentration increased free sugar and starch in root, stem, and leaf. Available carbohydrate concen— tration paralleled vegetative growth, seed yield, and pod retention, suggesting a direct influence of carbohydrate in limiting abscission. However, correlation coefficients between percentage of pod abscission and free sugar and starch levels under the two carbon dioxide levels did not reveal any significant relationships (Table 6). Non— significant negative correlations were observed between abscission rates and levels of available carbohydrate. Starch concentration of stems was negatively correlated with percentage of abscission in both cultivars at least at pod filling (Table 6). This may indicate that the carbohydrates temporarily stored in stems are used to retain pods. No significant correlations were evident between available carbohydrate in vegetative tissues or Stem weight and seed yield (Table 7 and 8). Abscission is a complex process whose mechanism is not fully .Ho>oa ma pm usmoawacmamn .am>ma mm am unmoamacmamm _ ow.I mo. mo.| aa. Ewan Ga commum om.| ea.I Na. NN.I uoom Ca nouaum «N. am.I am.I No. Eopm ca aamnm ooum am. ma. aw.I mm. noon ca Hagan moam wuaaUumS pd .HH mo.I av.I ma. «v.1 mama om noumum nma.I am.| om.| amm.l Eoum ca noamum % ma.I mm.I mm. mm.I uooa ca souwum 1 ma.1 av. mo.I No. mama ca “moon ooam mm.| aa.l Hm. mom. Hopm Ga Hmwdm mmum mo. mm. aa. hwa.| uoou Ga Hagan moan mmmum acaaaam com am .a N N oo sea com 00 Ema oom N00 and mom N8 and mom maouomaano Hoaawmom msom oauuoa Momam opwxoao cognac mo mao>oa 039 moons maa>aua50 comm wao 039 CH monomaa o>wumuw®o> Ga macauomam macaw Iagonaao magmaaa>< com scammaomhm pom mo omwusooawm soosuom muaoaoawwooo coaumaoaaoo m wanes 127 .ao>ma ma am aqaoamaqmamn .am>ma mm am ucmoamacmamm aw. ma. mN.I mm. mama ca nonmum ma. mm. am.I mo. noon Ca amamum No.I ma. NH. mo.| Emma Ga ammom mmam om.| mo. NN. mm. moon ca ammdm mmHm suaasums an va.I om. am. am.: mama ca noamum amm.l om. woa.l mm.I Emum Ca amaaam mv.I mv.I aN.I mo.I uooa ca soaaum ma. we. we. Na. mama aw Hausa mmum ma. am. who. av. Empm Ca ummsm mmum mv.l oa.| om.I mom.l moon ca Hmmsm mmam wmmpm mqaaaam mom a4 .HH N N N N oo and mom oo and com 00 and mom oo Ema mom mumuomamno amammmmm msom mamasa Momam mpaxoao Gonumo mo mam>ma 039 “moss mam>aua50 comm wan 03% ca mmSmmHB m>aumummm> Ca mcoauomam mumap>50hamo mammaam>¢ cam panam Hmm unmamz pmmm smmzumm mucmHoamwmoo coaumamuuoo a magma A r . 128 .am>ma ma am aqmoamaamamn .am>ma mm mm #cmoamacmamm aa.- aa.I mm. mm. ma.I mm. aa. ma.I mam. ma.I mm. «am. am. mo. ma.I mm. mm. ma.I am. ma.I mm.I ma.I am. ao.I mm. mm. mm.I mo. aa.I ma.I Noo sac com N8 and mom Noo sac mom N mm. Empm ca commum mm. moon ca coamuw mm. Emma ca Hmmcm mmam Nm. mooa ca Hamcm mmam muacsumz um ma.I mama ca cocmpm 9m. Emum ca commum Hm. moon ca coaaum mo. mama cw Hmmcm mmum ma.I Emwm ca ammcm mmam va. moon ca Hamcm mmum wmmum meaaaam mom pa om and com mamuomamco amamwmmm moom mauac9 moaam mpaxoao conamo mo mam>ma 039 ampcb maa>apaco comm mam 039 cm mmcmmfl9 m>aumumom> cw mcoauomam mumucmcomamo mammaam>m ccm pcmHm Hmm ucmHmB Emum cmm3umm mucmaoammmoo comumamaaoo m wanna .HH 129 understood. Available carbohydrate probably plays only an indirect role in the phenomenon. REFERENCES Cooper, R. L. and W. A. Brun. 1967. Response of soybeans to a carbon dioxide enriched atmosphere. Crop Sci. 7: 455—457. Guinn, G. 1974. Abscission of cotton floral buds and bolls as influenced by factors affecting photo- synthesis and respiration. Crop Sci. 14: 291—293. Hardman, L. L. and W. A. Brun. 1971. Effect of atmospheric carbon dioxide enrichment at dif— ferent developmental stages on growth and yield components of soybeans. Crop Sci. 11: 886—888. Krenzer, Jr., E. G. and D. N. Moss. 1975. Carbon dioxide enrichment effects upon yield and yield components in wheat. Crop Sci. 15: 71—74. Wittwer, S. H. and W. M. Robb. 1964. Carbon dioxide enrichment of greenhouse atmospheres for food crop production. Econ. Bot. 18: 34—56. 130 CHAPTER 7 ABSCISSION OF FLOWERS AND FRUITS IN PHASEOLUS VULGARIS L. VI. THE RELATIONSHIP BETWEEN POD ABSCISSION AND ENDOGENOUS ABSCISIC, PHASEIC, AND DIHYDRO- PHASEIC ACIDS IN THE PEDICELS AND FRUITS Abstract In two cultivars of dry bean, populations of fruits having low vs. high abscission potential were established by removing early-opening flowers from half the plants. Fruits were harvested 4 to 5 days after anthesis and separated according to length, which was negatively cor- related with abscission potential. Abscisic acid (ABA), phaseic acid (PA), and dihydrophaseic acid (DPA) contents were determined in methanol extracts of both pods and ped- icels, using electron capture gas liquid chromatography (GLC). None of the treatments affected the content of these 3 compounds in pedicels. ABA content of pods was positively correlated with abscission potential of the 2 cultivars and with fruit load, but was unaffected by fruit size. PA content increased with fruit size and with fruit load, but was not affected by cultivar. DPA content was greater in the cultivar exhibiting the higher rate of 131 132 abscission, but was unaffected by pod size or fruit load. I conclude that levels of extractable ABA, PA, and DPA do not regulate fruit abscission in bean. 133 Introduction During fruit abscission, both persisting (actively growing) and abscising fruits occur in the same population (3, 7). In order to make valid comparisons, one must be able to recognize and separate persisting and abscising fruits. Earlier attempts to do so were based on criteria such as fruit size, color, or loosening (2, 3, 5), which are useful only in the terminal stages of abscission (7), well after induction has occurred. Growth inhibitors have been frequently viewed as potential abscission-regulation hormones (2, 4). Abscisic acid has been identified and believed to have this abscis— sion regulating property (7). In peach, greater levels of abscisic acid was found in abscising (i.e. loose) than in persisting (i.e. tight) fruits (5). A strong correlation between abscisic acid content and abscission was reported in cotton fruit (2). However, the abscisic acid data presented in that paper could also be interpreted to be correlated with fruit growth. The evidence of abscisic acid levels correlated with growth rates was presented in soybean pods (9). Studying abscission in peach fruit, Zucconi (12) found levels of abscisic acid to be negatively correlated with abscission. My purpose was to test the hypothesis that ABA content controls fruit abscission in bean. Differential treatments, which had previously been shown to result in ~ 1mm}, ’1' i I r I.- - .. I l I .l\ I 'u t L. :' - '1 x . I -".' '.JI'2-a-" .- .--I:;Ii. 1'13 134 different rates of abscission, were applied, and pods were sampled during the induction phase for subsequent analysis. PA and DPA, previously shown to be metabolites of ABA (6), were also measured. Materials and Methods Plant Culture Two Phaseolus vulgaris L. cultivars, "Black Turtle Soup" and "Seafarer," were selected for their contrasting growth habits and abscission potentials. Seeds were planted in soil mixture (1:1:1 ratio of sand: sandy loam and peat) in 25 cm. pots in a greenhouse maintained at 24 i 3°C on February 16, 1976 for Black Turtle Soup and February 21, 1976 for Seafarer. The reason for sowing at different times is to get the two cultivars flowering at the same time. On emergence, the seedlings were thinned to one per pot. When the plants reached flowering stage on March 26, 1976, they were divided into two groups of 150 plants of each cultivar and differential treatments applied. Flowers opening six days or later after the first flower on the same plant have a high abscission potential in comparison with those opening earlier (Chapter 2). In the control treatment, flowers borne on the first five days were left on the plant. In the second group of plants, all flowers opening during the first five days were removed. Flowers opening the sixth day and thereafter 135 were tagged with color-coded wire, and the pods from these tagged flowers were harvested at 2-day intervals, immediately frozen on dry ice and stored at —lO°C. Eighty plants of each cultivar and treatment were used to record the rate of abscission. For each cultivar and treatment, 40 flowers that were borne on day six were tagged and individually numbered. Pods from these tagged flowers were measured every day and abscission was recorded. After freeze-drying, pods sampled on day 4 and 5 were divided into 3 groups: small (< 1.5 cm), medium ( 1.5-3.0 cm) and large (> 3.0 cm). An abscission potential was assigned to each subgroup based on the relationship between pod length and abscission probability determined experimentally from comparable pods monitored (in vivo) throughout their development. Extraction Pedicels (20 mg) and fruits (100 mg) were homogen- ized in 10 ml methanol, following the addition of 100 ng t, t-ABA to correct for losses. No t, t—ABA was recovered from nonspiked samples, and the amount of c, t—ABA recovered from blanks containing 5'5—ABA alone was negligible. The homogenates were left for 6 to 12 hours at 2°C in the refrigerator, then filtered, and the tissue was rinsed with methanol. The filtrate was reduced to 136 dryness in a flash evaporator at 40°C and resuspended in 20 ml distilled water. Fractionation The extract was adjusted to pH 8.0 with 0.1 N NH4OH and washed 3 times with 10 ml methylene chloride (CH2C12). The CH2C12 fraction was discarded. The water phase was adjusted to pH 3.0 with 0.1 N formic acid and partitioned 3 times with 15 ml ethyl acetate (EtAc) to obtain the acidic fraction, which was evaporated and stored at —lO°C until analyzed. Analysis The samples were resuspended in 0.5 m1 methanol and methylated with diazomethane according to Schlenk and Gellerman (8). The methylated samples were evaporated under nitrogen, the residues resuspended in 2 and 1 ml ethyl acetate for the pod and pedicel samples, respec- tively, and 2 ul of each sample was injected into a Packard 7300 Gas-Liquid Chromatograph equipped with a 63 Ni electron capture detector operated at 5v. The column was 2 mm i.d X 1.83 m, packed with 1% XE—60, 12,500 Centistrokes (CS or CSTK - the viscosity rating), on Gaschrome Q 80/100 mesh. Column, inlet and detector temperatures were 200°, 240°, and 240°C, respectively. The carrier gas was N2 at a flow rate of 40 ml/min at 40 psi. Nitrogen scavenger gas was supplied to the detector at 90 ml/min. 137 Data were quantified by measuring peak heights and comparing with a standard curve (semi—log) for each compound measured. Peak heights were linear over a range of 0.05 to 1.0 ng/ul ABA, 0.10 to 2.0 ng/ul PA and 0.05 to 2.0 ng/ul DPA. Data were corrected for losses during extraction and fractionation from the percentage of recovery of the standard t,t-ABA, assuming parallel losses, in c,t-ABA, PA and DPA. Results Pod Growth vs. Abscission Persisting and abscising pods could not be distin- guished on the basis of length during the first three days after pod setting. However, the growth rate of abscising pods began to decrease thereafter, and the differences in pod size increased until the pods abscised from the plants (Fig. 1A and B). Control vs. deflowered plants differed markedly in percentage of pod abscission. Only 30 and 20% of the pods abscised in the latter vs. 55 and 75% in the former for "Black Turtle Soup" and "Seafarer" respectively. Within treatments and cultivars, the degree of abscission was strongly correlated with pod size on days 4 and 5, smaller pods having a much greater tendency to abscise (Table l). I... ,,,,._it, $7.“;— v- -': _ .. .' I ._ V 6 4 _ o abscising pod o persisting pad 2 E A I c 4 l I I l .. 5 1O 15 20 25 2 Days after setting 2 1: o t 6 4 o abscising pod 2 o persisting pod 0 B I L l I I 5 1 O 15 20 25 Days otter setting Fig. 1. Growth curves of abscising and persisting pods. A. Black Turtle Soup; B. Seafarer. a ’-'—-_— . shtv-‘I 139 Hormone Content vs. Abscission ABA. ABA content of "Seafarer" pods was higher than that of "Black Turtle Soup" pods, particularly in the control treatment (Table l). Deflowering reduced ABA content in all cases. However, the effect of pod size was inconsistent. Thus, ABA content paralleled abscission in the case of cultivar and treatment effects, but not in size effect. None of the treatments affected ABA content of the pedicels. 25. Low levels of PA were detected in both pod and pedicel. PA was higher in pods from control plants than in those from deflowered plants in all but one case (Table 1). However, large pods contained more PA than medium or small pods, indicating no correlation with abscission. Cultivar did not affect PA content. PA levels in the pedicels were not affected by any of the treatments. DPA. "Seafarer“ pods contained significantly more DPA than did "Black Turtle Soup“ pods (Table 1). However, neither deflowering nor pod size affected DPA content of the pedicels. Discussion Although the work of both Martin and Nishijima (5) and Davis and Addicott (2) suggests a positive relationship between the content of ABA or ABA—like M I, i ucmumwmap Naucmowmacmam uoc mum m e m.v e a.mm e m.m : m.am e m.m a m.am e m.a a a.N x m.m x a.mm x a.o s a.mm x .m x m.am x m.o x m.~ umuuma Hmaafiam Na omsoa . HMQB Omar—IN n mm m 0H m ma n Nm M mN m mamauasz m. a3 um... Emu 05 ca memumm m cmocco ha am>m a mm on... um SUM? MENU—LN mound Ecfivmz aamsm umumummm m9m "MMMImmmmm a.” o.mm o m.am m.aa a.mm o emam mum nu m.m a.mm m.~ m.ma a.ma m.am 0 30a m a nu . . . . . . ma a a 0 an m a o v a aa 0 aoa mm s .m l . m m m.aq o m m.- a.mm o 30a seams: m.~ o.mm m.a m.aa a.ma a.mma mm swam m.m m.am m.~ o m.m~ m.aoa aa 30a aamsm umummmmm ans qnma o a.vm m.am a.mm o smam m m o a o o o.ma o.m m sea wmuma sum mumm a.a m.m a.ma a.ma mm Ema: o m m o o o m.aa v.oa o 30a asaomz Mum mnma ano o m.aa a.mm mm roam N v m N o m.aa 0.0H wv BOA HAM—um mBm awoaawm com awoaewm mom awoaamm mom can mm umaum> a .uz who m\m: M H mand9 MHN>H D .ua a seam 039 was no :oammaomn4 mo ammuqmouwm o» coauMamm :a ace can an .4m4 mo mam>ma 141 inhibitors in fruits and their abscission, Zucconi (12) has pointed out the fallacy of measuring ABA content of abscising fruits, yiz., that one is measuring the result of abscission rather than its cause. ABA content should be measured during induction. Zucconi (12) actually demonstrated a negative correlation between content of an ABA—like inhibitor and the induction of abscission in peach fruits. In the present study, ABA content of the fruits paralleled relative abscission potential as affected by cultivar and treatment (deflowering), but fruit size, which greatly affected abscission, had little effect on ABA content. I conclude from this that the cultivar and treatment effects on ABA content were fortuitous, rather than being causally related to abscission. If ABA con— tent were in fact responsible for abscission, one would expect differences to be apparent in the pedicel, where abscission actually occurs. However, this was not the case. PA and DPA have not been implicated directly in abscission, and their levels appear to bear little relationship to fruit retention. There was no correlation between relative levels of PA vs. DPA in the pods; PA levels were significantly affected by deflowering and by pod size, while DPA content varied only with cultivar. 142 If ABA regulates abscission, it must do so inde— pendently of concentration in the tissue as a whole. Concentrations might be very different in the cells of the abscission zone itself, for example. On the other hand, diffusible ABA could control abscission indepen- dently of the size of the pool of extractable ABA. REFERENCES Addicott, F. T. and J. L. Lyon. 1969. Physiology of abscisic acid and related substances. Ann. Rev. Plant Physiol. 20: 139-164. Davis, L. A. and F. T. Addicott. 1972. Abscisic acid: correlations with abscission and with development in the cotton fruit. Plant Physiol. 49: 644—648. Leuty, S. J. and M. J. Bukovac. 1968. A comparison of the growth and anatomical development of naturally abscising, non—abscising and naphthal— eneacetic acid-treated peach fruits. Phyto- morphology 18: 372-379. Luckwill, L. C. 1953. Studies of fruit development in relation to plant hormones. I. Hormone pro— duction by the developing apple seed in relation to fruit drop. J. Hort. Sci. 28: 14-24. Martin, G. C. and C. Nishijima. 1972. Levels of endogenous growth regulators in abscising and persisting peach fruits. J. Amer. Soc. Hort. Sci. 97: 561—565. Milborrow, B. V. 1974. The chemistry and physiology of abscisic acid. Ann. Rev. Plant Physiol. 25: 259-307. Ohkuma, K., J. L. Lyon, F. T. Addicott, and O. E. Smith. 1963. Abscisin II, an abscission- accelerating substance from young cotton fruit. Science 142: 1592—1593. Powell, L. E. and C. Pratt. 1966. Growth promoting substances in the developing fruit of peach (Prunus persica L.). J. Hort. Sci. 41: 331—348. Quebedeaux, B., P. B. Sweetser, and J. C. Rowell. 1976. Abscisic acid levels in soybean reproduc- tive structures during development. Plant Physiol. 58: 363—366. 143 10. ll. 12. 144 Schlenk, H. and J. L. Gellerman. 1960. Esterifi— cation of fatty acids with diazomethane on a small scale. Anal. Chem. 32: 1412-1414. Swanson, B. T. Jr., H. F. Wilkins, C. F. Weiser, and I. Klein. 1975. Endogenous ethylene and abscisic acid relative to phytogerontology. Plant Physiol. 55: 370-376. Zucconi, F. 1975. Reassessment of the relationship between hormonal and developmental changes during abscission with particular reference to peach (Prunus persica L. Batsch) fruit. Ph.D. disser— tation, Michigan State University. CHAPTER 8 SUMMARY AND CONCLUSIONS Elucidation of the causes of physiological pro— cesses is difficult, especially in an area as complex as abscission. However, an effort must be made to generate reasonable hypotheses, and to design appropriate experi- ments to test them, if progress is to be made. In this work, differences were established in abscission potential of reproductive structures in dry bean cultivars. Among the bean cultivars studied, Black Turtle Soup and Seafarer were selected for their contrasting growth habits and abscission rates. Black Turtle Soup, an indeterminate type, had a lower pod abscission rate than Seafarer, a determinate bush bean. Exposure of either cultivar to long photoperiods or high carbon dioxide levels after the onset of flowering increased vegetative growth and leaf area, reduced pod abscission and consequently resulted in higher seed number and greater seed yield. Black Turtle Soup was more responsive to both factors than was Seafarer. 145 146 Levels of free sugar and starch in root, stem and leaf increased with photoperiod and carbon dioxide level. Available carbohydrate concentration in vegetative tissues was higher in the Black Turtle Soup cultivar, consistent with larger plants, greater leaf area and a lower abscis- sion rate. However, the results provide only correlative evidence in support of the carbohydrate hypothesis. Levels of abscisic acid and its related compounds in pod and pedicel were not related to the role of abscission in either cultivar. Young pods of Seafarer contained more abscisic acid and dihydrophaseic acid than did those of Black Turtle Soup. Levels in the pedicel were not affected by cultivar. In conclusion, pod abscission in dry bean is not totally dependent on available carbohydrate levels. Many nutritional factors such as nitrogen, or carbohydrate/ nitrogen ratio could regulate abscission. Although endo- genous abscisic acid content was not correlated with abscission, other naturally occurring growth regulators, such as ethylene, cytokinin and auxin could play a role. The interplay between the nutritional and hormonal levels at a particular stage of development may control pod abscission. Since abscission is a complex process influ— enced by many environmental factors, care must be taken to design critical experiments to test available hypotheses. APPENDICES APPENDIX A GROWTH AND POD ABSCISSION AS AFFECTED BY DIFFERENT DAYLENGTHS .umm9 mmcmm mamauadz m.cdocdo Nb am>ma wa mcu um ucmummmap maucmoawacmaw Doc mum mcmuuma HmaaEam an ©m30aaom umumEaHam mEdm mcu cacua3 mcmmzm r .m.c as .m.c poaummouocm x Hm>auaco x mmmum .>mo av as «a as tOHHmQODocm x Hm>auaco Am «« s .m.c poaummouocm x mmmmm .>mm AN .m.c «a .m.c ua>auaco x mmmum .>mm Ra mcoauomumucH c a.mm c ea c mm Emanummm Hm>aua50 E m.am E m E Ha w9m cams xa.mm 31am Na.mm «ma aoa xm umm lama xoa new: ca.mm m.av m.am «.mm mm va m m mmw mm ma Ha cam: e.wm w.mm m.aa a.ma m ma 9 m mm mm mm va Hmumwmmm m.ov a.mm H.om o.mm a «A m m aa 9a m m mcom mauuc9 Moaam muaucumz am.wm a.mN m.mv o.mm nmw aa m m aMm mN ma m cmmz m.Nm a.mv m.mm m.av aa ma m m vm mm 9N NH Hmnmwmmm o.o~ m.m H.HN w.mm m ma 9 m aa 9a m m moom mauuc9 monam mcaaaam com I I I I ofl mm aa m mala ma ma ma :3: I I I I mm om am Na «N am mm Na cmumwmmm I I I I OH ma m 9 ca aa m a A“com mauuc9 Momam wcaum30am xmmm cam: ma ma m cam: ma ma w cam: ma ma m mcpmcmHNMQ mnumcmawmm mcumcmahao Hm>wuaco mmmmuw .>mo coammaomnm tom w moon mo .02 mam30am mo .02 amama ca wcoauaccoo mmsoccmmcw umocs c3ouw mum>auacu cmmm man 039 m0 ucmEm0am>mo mo mmmmum m mm c0flmmHUmnm pom mo mmmucmunmm ocm mcom mo cmnEcz .mum3oam wo HmnEcz co wcumcmawmo mo muomuwm HI< manm9 147 .uwm9 mmcmm mamauacz m.amoccm mm Hm>ma wa mcu um pcmumwmap maucmoamacmam uoc mum mumuuma HaaaEam an pm30HH0m HmumEmumm mEMm ms» casua3 mcmmZM .m.c .m.c .m.c vOaHmmouocm x um>wuaco x madam .>mo Av .m.c .m.c .m.c voaummouocm x Hm>auaco am .m.: a .m.: coaummouonm x madam .>mo mm .m.: «a .m.c Hm>auaco x mmmum .>mo AH WGOHHUMHOUGH c No.Nw c m c aa Hmummmmm Hm>fluadu e ma.mm a m a m mam :mmz xa.mm am.me um.am Noa am xm nma ama xoa cam: na.mm m.am m.am a.mm mm m m m mmm aa ma m emmz nu «.mm a.am a.~m m.ma m m m m aa mm ma ma umnmmmmm M“ a.mm a.mm m.am m.am m a m m m aa m m meow manage xomam muausumz ma.mv a.mm m.am m.am AM oa a m mwm aa ma aa cums m.am 0.0m m.am m.am m aa m m ma mm ma ma “mammmmm m.m~ a.ma m.am m.am a ma m m m ma m a snow manage xomam maaaaam mom 0mm aa aa m mmm Na Na oa :mmz I I I I ma ma ma ma oa ma ma ma umumwmmm I I I I a m m m a m m m muom manage somam mEaumzoam ammo qmmz ma ma m Emma ma ma m :mms ma ma m mcuacmaxao mcumcmawmo wcumcmahmo Hm>auacu mmmmum .>mo coamwaomcm pom m muom mo .02 mnmzoam mo .02 amama ca mc0auapcou mmcoccmmuo cmcco c3ouo mam>auaco cmmm who 039 mo ucmEmoam>mo mo mmmmum m um coammaomnm pom mo mmmucmoumm can moon m0 HmnEcz .wcm3oam mo umnEdz co mcumcmahao m0 muomuwm Nlm mHQmB .umm9 mmcmm mamauacz m.cmoccm >9 am>ma wa mcu um ucmummmap Naucmoamacmam uoc mam mcmuuma HmaaEam >3 ©m3oaaow HmumEmHmm mEmm mcu casua3 mcmmZm .m.c .m.c .m.c poaummouocm x um>auaco x momum .>mc am as a as voaummoaonm x Hm>aua50 Am .m.c .m.: .m.: coaummouocm x macaw .>mo AN .m.c .m.c .m.c cm>auaco x mmmum .>mo aa mcoauomumuca E w.m E aa E Nvma cmummmmw um>aua30 c a.v E ma c vmwa m9m cam: w xa.m amm xm.m nma Ema xma namma mom: xmaaa 5m: 1 Ema. a.m ma. Tm mmla. 8 ma ma mmama mmaa mama mmaa :mmz a.v m.v a.v m.m aa ma aa va omma amma omma avoa umcamamm o.m m.m o.m m.m ma om ma ma vmma aaam Nvaa mmNa mcom mauuc9 madam mcaaaam mom aa.m m.m a.m v.N MMM ma ma ma nemma coma mama woma cam: a.m a.e m.m m.~ aa aa ma aa vmma amma aaNa mmaa umumwamw m.v a.a m.m m.m aa an ma ea vmma moma mama mmNa mcow maucc9 moaam mcaum3oam xmmm cam: ma ma m cam: wa ma m cam: ma ma m mcumcmammo mcumcmawmo mcumcmahmo um>auaco mmaum .>mo Amv ucaam\ucmam3 mama ucaam\mmma .oz ucmam\mmum mama amhaa ca chauavcoo mmcoccmmuo Emacs c3ocw mua>aUaco cmmm NED 039 mo ucmEQOam>mo Mo mmmmum m an unwam Hmm ucmamz mama pca unwam umm mama wo cmnEcz .ucaam Hmm amum mama c0 mcumcmahmo mo muomuwm mld man09 150 .uwm9 mmcmm maQHUaSE m.amucdo MD am>ma wa mcu um ucmnmmwaw maucmoawacmam uoc mum mumuuma Hmaafiam an pm30aa0m HmumEmnmm mEMm mcu cacua3 mcmmza .m.c .m.: .m.: wOaHmmouocm x Hm>auaso x mmmum .>mo av .m.c .m.c .m.c woaumm0pocm x Hm>auaco am m .m.: .m.: poaummouocm x mmmum .>mo AN 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