‘ MSU LIBRARIES “- RETURNING MATERIALS: Place in book drop to remove this checkout from your record. FINES will be charged if book is returned after the date stamped below. CARBOHYDRATE PRODUCTION, BALANCE AND TRANSLOCATION IN LEAVES, SHOOTS AND FRUITS OF' MONTMORENCY' SOUR CHERRY 3)! Ewalo Maximilian Kappes A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Horticulture 1585 ABSTRACT CARBOHYDRATE PRODUCTION, BALANCE AND TRANSLOCATION IN LEAVES, SHOOTS AND FRUITS OF 'MONTMORENCY' SOUR CHERRY By Ewald Maximilian Kappes Carbohydrate production, export and use were studied for different organs of sour cherry (Prunus cerasus L.'Montmorency'h Gross carbohydrate (”(202) export started between 27.2 and 77.6% of full leaf expansion. The 10th leaf developing started export later than the 7th leaf, suggesting that higher carbohydrate availability during leaf expansion delays export initiation. In support of this, gross export started earlier (44.4 - 52.4% full expansion) after source leaf removal, than in the control (77.6%). Translocation was primarily vertical (following orthostichies). Most leaves of fruiting shoots exported bidirectionally to the apex and fruits, only leaves closestLto fruits exported exclusively to fruits during rapid cell division (Stage I) and rapid cell expansion (Stage III). Net export, determined from carbohydrate balance mooels started at I7 and 51% expansion for the 7th and terminal leaf, and at 26.5% of shoot elongation. Cumulative carbohydrate proouction of the 7th and terminal leaves during the first 9 ano 11 days after emergence, exceeded carbohydrate accumulated at final size, 404.2 and 148.9 mg. A fruit carbohydrate balance was develOped to determine contributions by fruit photosynthesis and fruit respiration, and to identify periods of greatest carbohydrate import. Fruit photosynthesis contributed 11.2% of total carbohydrates accumulated and respired. Fruit photosynthetic contribution was high during stage I (19.4%) and the subsequent embryo developmentstage (II) (29.7%) and negligible during stage III (1.5%). Respiratory consumption was 30.9% overall, with 32.7, 70.9 and 19.9% during stages I, II and III, reSpectively. Carbohydrate imports were highest (16.54 and 35.14 mg day'l') during mid stages I and III. Fruit photosynthesis during development was characterized unoer different environmental conditions. Gross photosynthesis and chlorophyll content per fruit increased to a. maximum during stage II and decreased thereafter. Light saturation was at 1000 pmol m'zs"1 and 002 saturation at 400 cm3m‘3. Gross photosynthesis approached a maximum at 40°C. Since dark respiration increased exponentially over the same temperature range, net photosynthesis reached a maximum at 18°C. Photorespiration was not detected. Dark 002 fixation was 10% of light 002 fixation during stages I and II, and 100% during stage III. ACKNOWLEDGMENTS I wish to express my sincere gratitude to my major professor Dr. J. A. Flore for his direction, encouragement and criticism during the course of my graduate program. I would also like thank Drs. M. J. Bukovac, F. 6. Dennis, Jr., N. E. Good and M. J. Zabik for serving on my guidance committee and for their helpful suggestions. My special thanks to my wife Arlene and my'parents for their love, support and understanding. ii Guidance Committee: The Journal paper format was chosen for this thesis in accordance with departmental and university regulations. The thesis is divided into four sections. Sections one, two and three are intended for publication in The Journal of the American Society for Horticultural Science and section four is intenoeo for publication in Photosynthetica. Appendix A is intenoeo for publication in Acta Horticulturae. TABLE OF CONTENTS LIST OF TABLES ....................... LIST OF FIGURES ...................... INTRODUCTION ..... . . . . . . . . . . . ...... . . Section I The Influence of Phyllotaxy and Stage of Leaf and Fruit Development on the Initiation and Direction of Gross Carbohydrate Export from Sour Cherry (Prunus Cerasus L. 'Montmorency') Leaves . . . . . . . . . . . . . . . . . . . Abstract .......... . ....... . . . . . Section II Estimation of Net Carbohydrate Export From Sour Cherry (Prunus cerasus L.'Montmorency0 Leaves ano Shoots Abstract ....................... Introduction ..................... Materials and Methods ................ Results ....................... Discussion ...................... iv Page vii 3s 36 37 39 42 Page Literature Cited ................... 72 Section III Sour Cherry Fruit Carbohydrate Balance During Development, from Empirical Models of Carbohydrate Accumulation, Net Photosynthesis, Gross Photosynthesis and Dark Respiration . . 76 Abstract . ...................... 77 Introduction . . . ...... . . . . .'. . . . . . . 78 Materials and Methods . . . . . . . . . . . . . . . . 79 Results . . . . . . . . . . . . . . . . . . . . . . . 82 Discussion . . . . . ...... . ....... . . . 90 Literature Cited . . . . . . . . . . ......... 95 Section IV Photosynthesis and ReSpiration of Sour Cherry (Prunus cerasus l" 'Montmorency”) Fruits During Development as IfiTTUEHCed by the Environment . . . . . . . . . . . . . . . 98 Abstract . ...................... 99 Introduction . . . . ................. 100 Materials and Methods ................ 100 Results . . . . . . . . . . . . . . . . . . . . . . . 103 - Discussion . . . . . . ...... . . . . . . . . . . 123 Literature Cited ................... 129 SUMMARY AND CONCLUSIONS .................. 133 Appendix A Carbohydrate Balance Models for 'Montmorency' Sour Cherry Leaves, Shoots and Fruits During Development . . . . . . . Abstract . . . . . . ...... . . . . . . . . . . . Introduction ............ . . . . . . . . . Equations ...................... Predictions . . . . . . . . . . . . . . . . ..... References . . . . . . . . . . . . . . . . . . . . . . Appendix B CHERRYCARB: A BASIC Carbohydrate Balance Model Program for 'Montmorency' Sour Cherry Leaves, Shoots and Fruits During Development . .. . .. . . .. . .. . .. . . . . .. .. Appendix C Validation of Leaf and Shoot Carbohydrate Balance Models. . Appendix 0 Comparison of Photosynthesis Measurements under Field and Laboratory Conditions . . . . . . . . . . . . ...... vi Page 137 138 139 140 141 144 157 164 LIST OF TABLES Table Section I 14COguptake by the seventh leaf of 'Montmorency' sour cherryduringpulsing Levels of visual detection by autoradiography after 3 d exposure of autoradiOQraphy film to oven dried fignples. Sampling of shoots after 30 min exposure to 02 (QICi) and 24 hr translocation . . . . . . . . Gross carbonydrate export from the 7th leaf of 'Montmorenc ' sour cherry during expansion in 1983 (31.2115.0cm final size) . . . . . . . . . . . . .. Gross carbohydrate export from the 10th leaf of 'Montmorency' sour cherry during expansion in 1983 (28.8:10.2cm3final size) . . . . . . . . . Gross carbohydrate export from the 7th leaf of 'Montmorency', sour cherry during expansion in 1985 (55.b3_13.5 cm‘ final size) . . . . . . . . . . . . . Gross carbohydrate export from the 10th leaf of 'Montmorency' 5 ur cherry during expansion (l985)(46.8:12.2 cm final size) . . . . . . . . . . Gross carbohydrate export from the 10th leaf of defoliated 'Montmorency‘ sour cherry during expansion (1985)(53.8:16.1 cm final size) . . . ....... Section II Correlation coefficients (8(12 - 8(4)) and coefficients of determination (r ) of the regression equations for daily net photosynthesis (DPN). daily gross PDOWSYDWESIS (DP ) and daily dark respiration (0RD) for the seventh an terminal eaf and shoots of 'Montmorency' sour cherry during growth ....... vii Page 12 16 17 16 19 20 21 49 Table 2. 1. .1. 3. Thirty day simulated carbohydrate balance for the 7th leaf of 'Montmorency' sour cherry from the beginning of leaf emergence, until full expansion . . Twenty day simulated carbohydrate balance for the terminal leaf of 'Montmorency' sour cherry from the beginning of leaf emergence, until full expansion .. Comparison of 7th leaf and terminal leaf and the whole shoot of 'Montmorency' sour cherry . .. .. . “ Sixty-five day simulated carbohydrate balance for the whole shoot of 'Montmorency‘ sour cherry from bud break, until full expansion .... .... . .. . . .. Section III Regression coefficients for 'Montmorency' sour cherry fruit daily net photosynthesis (DPN), daily gross photosynthesis (DP and daily dark respiration (0RD) ) as a function 0? carbohydrate content, and of. carbohydrate accumulation (CHZO) as a function Of time, during fruit growth .. . .. . .. .. .. .. Simulated carbohydrate balance (mg CH20. % 0“ total CHZO in parentheses) of 'Montmorency‘ sour cherry fruits during their development ” .. . .. . .. . Time course of daily gross photosynthesis (DPG) as a percentage of daily dark respiration (0RD) (experimental data) C C C . Q 0 O C O C O O C C C O 0 Simulated carbohydrate import (mg CH20 day'l) 0f 'Montmorency' sour cherry fruits during development from full bloom to maturity . . . . . . . . . . . . . Section IV Dark respiration 010 of"Montmorency” sour cherry frUit O O O O O O O O O O O O O O O O I O O O O O O 0 Oxygen response of gross photosynthesis (PG, net photosynthesis (P , and dark respiration Roof 'Montmorency' sour c erry fruits and leaves . . . .. 14Carbon dioxide fixation by"Montmorency‘ sour cherry leaves and fruits,irifull sunlight and Hithe dark, during exposure to 185,000 Bq .. . .. .. .. .. . viii Page 51 59 60 68 86 89 91 92 118 121 Table Appendix A 1. Carbohydrate balance (mg CH20, % of total CHZO in parentheses) of 'Montmorency”sour cherry fruits during their development 0 O O O O O O O O O O O O O O O I 0 Appendix C 1. Chi2 values calculated from predicted and observed data sets of daily gross photosynthesis (DPG), daily net photosynthesis (DPN), daily dark respiration (0RD) and cumulative carbohydrate content (CHzo) of 7th and terminal leaves and shoots of 'Montmorency' sour cherry during development . .. . .. . .. . .. . . Appendix D 1. Rate of net photosynthesis (PM) Dug 002 dm-Z h-l) and stomatal conductance (g‘s)(cm 5-1) of the 10th leaf (just fully expanded). At the beginning of the 10th leaf's expansion proximal leaves were removed, as compared to the non-defoliated control. Measurements were taken outside with a portable photosynthesis unit . . ix Page 143 159 167 ' LIST OF FIGURES Figure Section I 1. l4C-pulsing apparatus (schematic drawing) . ..... 2. Levels of detection by autoradiography in leaf and fruit tissue, as presented in Table 2,iu)(-), trace (tr) and high (+) activity . .. . .. . .. . .. . :L Pattern of carbohydrate export developed from autoradiographs from the 7th leaf of non-fruiting 'Montmorency'sour cherry. Each field represents a leaf; leaves are numbered in sequence from shoot base to apex. Leaves of common orthostichies are shown in the same angle (schematic drawing) . .. .. .. .. 4. Autoradiographs (left) and corresponding shoots (right) showing the pattern of 14C-carbohydrate export from the 7th (a-d) and 10th (e-f) leaf of non- fruiting 'Montmorency“ sour cherry during shoot elongation. a. Shortly after onset of export. Exporting to part of the 9th leaf to the 10th leaf and the shoot apex. Traces can be detected in the proximal leaves. b. Exporting to part of the 9th leaf, to the 10th, 12th and the shoot apex, and traces only to the 11th lea£.Traces are also detected in petioles of other leaves. c. Exporting to the 10th, 12th, 13th leaf and the apex,andtracesto the 9th and 11th leaf, and proximal petioles. (L Exporting to the 10th, 12th, 13th, 14th leaf, the apex and its axial shoot, and traces to the 9th and 11th leaf. e. Before initiation of export. f. Exporting to part of the 11th leaf, to the 12th, 14th and the shoot apex. Traces are detected in the 13th leaf and proximal leaves and petioles .. .. . Page 13 23 25 Figure Page 5. Autoradiographs (left) and corresponding shoots (right) showing the pattern of 14C-carbohydrate export from leaves of fruiting 'Montmorency' sour cherry shoots during fruit and shoot development. The pulsed leaf is marked with an arrow. a-c. Stage I of shoot development. d-f. Stage II of fruit development. g-i. Stage III of fruit development . . . . . . . . . . . 28 Section II 1. Relationship between leaf area and carbohydrate content of the 7th leaf of 'Montmorency' sour cherry during leaf expansion, observations (circles) and fitted curve (line) .. . .. . .. . .. . .. . .. 43 2. Carbohydrate accumulation of the 7th leaf, of 'Montmorency" sour cherry, starting at leaf emergence, observations (circles), fitted curve (solid line) and carbohydrate accumulation rate (broken line) . . . . 45 3. Daily gross photosynthesis (DPG ) (A) da1ly net photosynthesis (DP )(B) and daily dark respiration (DRD ) (C) of the Sth leaf of Montmorency' sour cherny, observationsh (circles) and fitted curves (lines) at different leaf sizes during leaf expansion . . 47 4. Relationship between leaf area and carbohydrate content of the terminal leaf of 'Montmorency” sour cherry, observations (circles) and fitted curve (line) during leaf expansion .. . .. . .. . .. . .. . 52 5. Carbohydrate accumulation of the terminal leaf of 'Montmorency' sour cherry during leaf expansion, observations (circles), fitted curve (solid line) and carbohydrate accumulation rate (broken line) . . . . 54 6. Daily gross photosynthesis (DP G) (A) daily net photosynthesis (DPN ) (B) and dailyG dark respiration 10R 0) (C) of the terminal leaf of ‘Montmorency sour cherry, observations (circles) and predicted curves (lines) at different leaf sizes during leaf expansion . . 57 7. Relationship between length and carbohydrate content of the whole shoot of 'Montmorency' sour cherry during leaf expansion, observations (circles), fitted curve (line) . . . . . . . . . . . . . . . . . . . . . . . . 62 xi Figure 8. Carbohydrate accumulation of the whole shoot of 'Montmorency' sour cherry during shoot elongation observations (circles), fitted curve (solid line) and carbohydrate accumulation rate (broken line) . . . . . 9. Daily gross photosynthesis (0P3) (A) daily net photosynthesis (DP ) (B) and daily dark respiration (0RD) (C) of the wflole shoot of Montmorency' sour cherry, observations (circleS) and fitted curves (lines) at different shoot sizes during shoot elongation .. . .. . .. . .. . .. . .. . .. . Section III 1. C02 gas exchange of fruits as a function of fruit carbohydrate content during development of 'Montmorency' sour cherry fruit, observations (circles) and fitted curves (lines).lL Daily gross photosynthesis (DPS), B. Daily net photosynthesis (DPN) and C. daily dark respiration (0RD) - . - . - . 2. A. Relationship between time after full bloom and carbohydrate accumulation of 'Montmorency‘ sour cherry fruit during development,observations (circles), fitted curve (solid line), carbohydrate accumulation rate (broken line) . ...... . .......... xii Page 64 b6 83 87 Figure 1. 2. 6. 7. Section IV IL Total chlorOphyll per fruit (open circles) and per unit fruit surface area (closed circles) during 'Montmorency‘ sour cherry fruit development. 8. Surface area (open circles) and volume (closed circles) of 'Montmorency' sour cherry fruit during development. Vertical bars indicate standard error of the mean . . Fruit gross photosynthesis (P3)(0pen circleS) and dark respiration (RD) rates (closed circles) per fruit (A) per unit surface area (B) and per unit volume (C) o 'Montmorency' sour cherry fruit during development. Vertical bars indicate standard errors of the mean .. Scanning electron micrograph of fruit surface of 'Montmorency' sour cherry during stages I (A), II (B) and III (C) of fruit development illustrating size and shape of stomata Fruit stomatal conductance to 00- (9's) in the light (open circles) and in the dark Cc osed circles) of 'Montmorency' sour cherry fruit during development. Vertical bars indicate standard errors of the mean .. . Effect of photosynthetic photon flux density (PPDF) on net photosynthesis rate (PM) of 'Montmorency' sour cherry fruits during Stage 1. Different symbols on the graph represent different replications, and each replication is the average of 4 fruits. . . . . . . . A. Mathematical functions for the effect of temperature on gross photosynthesis (P~) (top line), net photosynthesis (PN) (center line) and dark respiration (RD) (bottom line) in stage I. 8. Observed values for net photosynthesis (PN) (open symbols) and dark respiration (PD) (closed symbols) in stage III of 'Montmorency' sour cherry fruits, as affected by temperature. Different symbols on the graph represent different replications, and each replication is the average of 4 fruits . .. . .. . .. . .. . . Effect of external C02 concentrations (ca) 0" "9t photosynthesis (PM) of 'Montmorency” sour cherry fruits during Stage I. Different symbols on the graph represent different replications, and each replication is the average of 4 fruits .. . .. . .. . .. . .. xiii Page 105 107 109 111 113 115 119 Figure 1. Comparisonof rates of net photosynthesis ofthetenth leaf of defoliated(closed circles, broken line) and control(open circles, solid line) 'Montmorency' sour cherry during development, observations and regression lines 0 O O O O O O O O O f O O O O O O O O O O O O 0 Appendix C Comparison of predicted and experimental data for: A.Carbohydate accumulation of the seventh leaf B.Carbohydrate accumulation of the whole shoot C.Daily net photosynthesis of the seventh leaf D.Daily gross photosynthesis of the seventh leaf E.Daily dark respiration of the seventh leaf .. . Comparison of predicted and experimental data for: A.Daily net photosynthesis of the terminal leaf E.Daily gross photosynthesis of the terminal leaf C.Daily dark respiration of the terminal leaf D.Daily net photosynthesis of the whole shoot E.Daily gross photosynthesis of the whole shoot F.0aily dark respiration of the whole shoot . . . . . Appendix D xiv Page 160 162 168 INTRODUCTION A major goal in horticulture is the improvement of crop yield. To accomplish this goal one must understand the limitations to yield. Yield is the product of net photosynthetic production and the harvest index, which is an efficiency factor representing the proportion of assimilates partitioned to the harvested plant parts. Yield can theoretically be limited by either, net photosynthetic production or harvest index. Net photosynthetic production appears to limit yield in sour cherry only in the rare case of a leaf-to-fruit ratio below 1.5 or 2 (Flore and Sams, 1985).Thus, assimilate partitioning (which determines the harvest index) plays the key role in sour cherry fruit production. The partitioning process starts at the source leaf where assimilates are either used by the leaf (accumulation, respiration) or exported (phloem loading). Phloem unloading in various organs further determines partitioning and seems to be controlled by the carbohydrate demand of the sinks connected to the particular phloem strand. Source-sink relationships can be summarized in a translation of a statement by Walter Eschrich (1984), which could apply as well to sour cherries: “It is not because a lot of sugar migrates along the sieve tubes that potatoes grow, but because potatoes grow, a lot of sugar mi grates along the sieve tubes". Thus, fruit number, growth rate and duration of the growth period, rather than carbohydrate production, seem to control carbohydrate allocation in the fruit crop. However, carbohydrate availability during early reproductive development might affect fruit number, since an adequate carbohydrate supply is associated with high fruit set in sweet cherry (Feucht et al., 1972) and grape (Sartorius, 1926) Carbohydrates imported by sour cherry fruits are incorporated into fruit dry matter or used for respiration to supply energy for transport and synthesis. Respiration leads to a loss of carbohydrates sometimes regarded as wasteful. Besides the carbohydrates supplied by the transport system, fruits use carbohydrates produced by their own photosynthetic activity. A better understanding of yield formation requires a better knowledge of carbohydrate partitioning in the leaf, export from the leaf and import, production and use by the fruit; Thus the major objectives of this study were to investigate a) the initiation and regulation of carbohydrate export from leaves and shoots, b) the carbohydrate need, import, production and use by the fruits, and c) the factors affecting fruit photosynthesis. Literature Cited: 1.Eschrich, N. 1984. Untersuchungen zur Regulation des Assimilattransports. Ber. Deut. Bot. Ges. 97:5-14. 2;Feucht, N., M. Z. Khan and N. Gruppe. 1972. Die Rolle von Nuchshormonen und des ll-Stoffwechsels 'hi der Reifephase von Kirschenfruechten. Gartenbauwissenschaft, 37:409-418. 3. Flore, J. A. and C. E. Sams. 1985. Does photosynthesis limit yield of sour cherry (M cerasus ‘Montmorency')? In: Lakso, A. N. and F. Lenz (eds.) Regulation of photosynthesis in fruit trees. N. Y. Sta. Agr. Expt. Sta. Spec. Bull. (In press). 4.Sartorius, 0. 1926. Zur Entwicklung und Physiologie der Rebbluete. Angew. Bot. 8:29-89. Section I The Influence of Phyllotaxy and Stage of Leaf and Fruit Development on the Initiation and Direction of Gross Carbohydrate Export from Sour Cherry (Prungs cerasus L. 'Montmorency') Leaves Abstract. The influence of phyllotaxy and stage of leaf' and fruit development on the initiation and direction of carbohydrate (CHZO) export from sour cherry leaves was investigated during 2 different seasons. One-year-old sour cherry trees on Mahaleb rootstock were pruned to a single shoot, the 7th and 10th leaf (from the base) were pulsed with 14coz, and labelled carbon products were located after 24 hr using autoradiography. In 1983 gross export (EG) from the 7th and 10th leaf was initiated when the area of the 7th leaf reached 8.5 cm2 (27.2% expansion) and when that of the 10th leaf reached 13.8 to 20.8 cm2 (48.0 - 72.3% expansion), respectively. E5 was generally initiated later in 1985 than in 1983, for the 7th leaf later than 26.3 cm2 (47.5% expansion) and for the 10th leaf at 36.3 cm2 (77.6% expansion). Leaf size was greater at full expansion in 1985 than in 1983. We suggest that after a leaf has developed the potential for phloem loading, the onset 0f CH20 export is a function of the CHZO availability in the plant at the time of leaf expansion. To test the effect of CH20 availability on the initiation of E9, in 1985 all leaves older than the 10th leaf were removed at the beginning of its development. 0n defoliated shoots the 10th leaf (53.8:16.1 cm2 full expansion) started export between 23.9 and 28.2 cm2 (44.4 - 52.4% expansion), whereas control leaves on non- defoliated shoots started export at 36.3 cm2 (77.6% expansion). Translocation paths followed closely the orthostichy of the exporting leaf. Fruit effects on the direction of translocation were studied in 2- year-old trees. During stages I and III of fruit development leaves closest to the base showed basipetal translocation only. All leaves during stage II and leaves distal to the the midpoint of the shoot during stages I and III showed bidirectional translocation to the shoot apex and the fruits. Leaf ontogeny in PEIEtiOH t0 CH20 utilization usually passes through 3 phases: i. a phase when the leaf imports CH20, ii- 3 phase when DOth import and export occur simultaneously and, iii. a phase when only export takes place (8). The transition between source and sink is accompanied and may be caused by morphological and physiological changes (2,3,10). Leaves might not accept messages from sinks demanding assimilates until a certain degree of maturity is reached (17). Sugar beet leaves start gross carbohydrate export (E5) (phase ii) it 35% 0f the final laminar length (3), while-soybean and squash begin gross export at 30% and as: of full expansion, respectively (15,16). The onset of 56 from grape leaves occurs at 30% (7) or 50% (4) of leaf expansion. Simultaneous export and import of CHZO has been ObSEPVEd in soybean (15), squash (18), grape (7) and sugar beet (3). The start of gross export is therefore a first step in leaf development towards autotrophy. Total autotrophy cannot be reached until export exceeds import, i. e. the onset of net export (EN). The direction of translocation is coupled to a leaf's orthostichy, as demonstrated in peach (11), apple (8), willow (5) and cottonwood (9). 11115 phenomenon is known as autonomy of orthostichies (8). Sink-source relationships can also affect the direction of translocation and create distinct zones for acropetal and basipetal translocation. The removal of ‘the basal leaves in apple causes translocation from apical leaves to the roots (13). Grape fruits become strong sinks during their development and attract photosynthates from an increasing number of leaves (7,14). Grape leaves close to the apex translocate acr0petally, leaves close to the base translocate basipetally, and only a few intermediate leaves translocate bidirectionally (4,7). The objectives of this study were: a) to determine when E5 by leaves at different positions on the shoot is initiated, b) to determine the effect of orthostichies on the pattern of translocation within the shoot, c) to determine if distinct zones for acropetal and basipetal translocation exist in sour cherry and, d) to test whether CHzo supply affects the initiation of E5- Materials and Methods Plant material fo r studying the start of gross export: One-year-old 'Montmorency' sour cherry trees on Mahaleb rootstock were obtained from Hilltop Orchards and Nurseries, Hartford, MI, potted in the spring of 1983 and 1985 in 7.5 liter containers using a mixture of peat, sand and field loam (3:2:5,v:v:v), and pruned to a single bud. During the study only I shoot was permitted to grow. Trees were grown outside at the Horticulture Research Center in East Lansing, MI. Hater, fertilizer (20% N. 20% P205, 20% K20) and pesticides (Captan, Guthion, Kelthane) were applied as necessary. Trees were placed in a completely randomized design. Twenty trees were used as a control to measure leaf expansion. Fourty trees were used ‘for: the labelling treatment, 20 of them to label the 7th leaf from the shoot base and the remaining 20 to label the 10th leaf. The study was repeated a 2nd season, with 40 additional trees which were defoliated below the 10th leaf at the beginning of its development. Twenty defoliated trees were used to determine the initiation of export from the 10th leaf and 20 were used to determine leaf area at full expansion. Plant material for studyinggfruit effects on the direction of ‘ translocation: Some of the trees potted in 1983 were transferred to 12- liter containers in the spring of 1984. The flowers (lateral on 1-year- old wood) were hand-pollinated with 'Montmorency' pollen. Nine fruiting plants were selected at random, and extension shoots with fruits in close proximity to them were used for the experiments. 14C-labelling: One leaf per plant was selected and exposed to 14C02 using the method of Quinlan (12) modified as follows (Fig. 1). The leaf was enclosed in a polyethylene bag containing about 1 liter of ambient air. The bag was sealed around the petiole using modelling clay. A 30 cm plastic tube leading from the interior of the bag to a disposable three- way stopcock was connected to a 1 ml and a 50 ml syringe. An aliquot of a stock solution of 14C-sodium bicarbonate (47.1 mCi/mmol) obtained from New England Nuclear (Boston, MA) was diluted to contain 10 pCi/ml, and 0.5 ml (5}1Ci) were transferred to the 50 ml syringe. The 1 ml syringe was filled with 5N sulfuric acid. While the valve was open between the two syringes the acid was transferred to the bicarbonate to release the 'L4c02. Then the connection between the large syringe and the bag was opened by turning the valve, and the plunger was moved back and forth several times to mix the acid with the bicarbonate and to mix the releasead 14C02 with the air in the bag. The bag was kept in position Figure l. 14C-pulsing apparatus (schematic drawing). LEAF. "ODELING CLAY s i: . 10 Figure 1. POLYETHYLENE BAG | ~./' .2 /. 3-wAY STOPCOCK aqf/r ‘\"We , POLYPROPYLENE TUBING 1 ML‘SYRINGE 50 ML-SYRINGE 11 f0? 30 min, after WhiCh l4C02 uptake was almost complete (97.4%) (Table 1). Area (A) of the treated leaves was calculated from length (L) and width (W) using the following regression equation: A - L * u * 0.65 r2 - 0.998 n . 73 Determination of transport patterns: Twenty-four hr after pulsing the shoot was sampled, mounted on paper and dried for 3 days at 105°C in a forced draft oven. The dry samples were placed in contact with X-Omat AR film (Eastman Kodak 00., Rochester, NY) for 3 days using Kodak exposure holders and then developed according to manufacturer guidelines. Autoradiographs were used to examine whether radioactivity occurred in non-treated leaves or fruits. To determine levels of detection by autoradiography, samples were combusted using a Biological Oxidizer 9 0x400 (R. J. Harvey Instument Corporation, Hillsdale, NJ). The combustion products were trapped in Carbon-l4-Cocktail (R. J. Harvey Instrument Company, Hillsdale, NJ) and the radioactivity counted in a liquid scintillation counter (1211 Rackbeta, LKB-wallac, Turku, Finland). Corrections were made for combustion, trapping and counting efficiency, and data were calculated as disintegrations per minute (dpm). Levels of visual detection by autoradiography are shown in Table 2 and Figure 2. 12 Table 1- l4C02 uptake by the seventh leaf of 'Montmorency' sour cherry during pulsing Time Residual Activity Activity (absorbed) (min) yCi %. yCi % 1 0.62:0.33 12.4 4.38 87.6 2 0.79:0.39 15.8 4.21 84.2 5 0.49:0.05 9.8 4.51 90.2 10 0.38:0.08. 7.6 4.62 92.4 30 0.13_+_o.os 2.6 41.87 97.4 13 Figure 2. Levels of detection by autoradiography in leaf and fruit tissue, as presented in Table 2, no (-), trace (tr) and high (+) activity. tr tr 111 15 A 2/5 phyllotaxy configuration was determined according to the method of Allard (1). The angular distances from orthostichy a for orthostichies a-f are therefore (6): Orthostichy a 0° b 1440 c -720 d 72° e -144° f 0° The direction of export as affected by the phyllotaxy was then determined by the methods described above. Results Start of gross carbohydrate export in 1983: At full expansion the sizes of the 7th and 10th leaf were 31.2:15.0 cm2 and 28.8:10.2 cmZ, respectively. EG from the 7th leaf was initiated at 8.5 cm2 or 27.2% of full expansion (Table 3). 50 from the 10th leaf started between 13.8 and 20.3 cm2 or 48.0 and 72.3% of full expansion (Table 4). Start ofggross carbohydrate export in 1985: The final size of the 7th and 10th leaf was 55.6:13.5 and 46.8:12.2 cmz, respectively. The final size of the 10th leaf of the defoliated plants was 53.8:16.1 cmz. 56 from the 7th leaf was initiated between 26.3 and 55.0 cmz. or 47.5 and 98.9% of full expansion (Table 5). EG from the 10th leaf started at 36.3 cm2 or 77.6% of full expansion (Table 6). 58 from the 10th leaf of defoliated shoots started between 23.9 and 28.2 cm2 or between 44.4 and 52.4% of full expansion (Table 7). 16 Table 2. Levels of visual detection by autoradiography after 3 d exposure of autoradiography film to oven dried samples. Sampling of shoots after 30 min exposure of a leaf to 14002 (fipCi) and 24 hr translocation. Activity Pulsed High *Tracé' No leaf (+) (tr) (-) Leaf (dpm chi-1) 165802130434 77978: 20710 1339_+_ 1256 84_+_ 61 Pedicelz (dpm) - p 33608: 21236 2636: 2387 .344: 275 Fruitz (dpm) - 4603071272687 18599119271 2290:1463 zFruits were lateral on I-year-old wood proximal to the treated leaf on the current seasons growth Table 3. l7 Gross carbohydratez export from the 7th leaf of 'Montmorency' sour cherry during expansion in 1983 (31.2:15.0 cm2 final size) Leaf area $3 iTEf Final siié of control Export O meNooowNOioooOimw HHO—‘HHD—‘HHHH ooooooaimao-n-Nmoooooow 0 HP tom . 0110 20. 23.5 25.1 36.1 23.4 27.2 27.5 28.2 38.4 40.4 45.5 45.8 47.4 48.0 53.5 57.9 58.6 59.3 60.9 62.5 65.0 75.3 80.4 115.6 + + + + + + + + + + + + + + + + + + +¢+ 1 z Pulsed with 5 pCi of 14002 for 30 min, and 14C distribution determined 24 hr after pulsing. 18 Table 4. Gross carbohydratez export from the 10th leaf of"Montmorency' sour cherry during expansion in 1983 (28.8:10.2 cm2 final size) Leaf area Export % of final siie of control ‘9 . O O C O mHNmemonwO—IP‘MQNVN oiwmmbommmwommmbwwwi o o o wwNNNND—‘HO—‘HH sommwmmmbwwmmwt—aw too-aceruiNmmr-amr-o-hmmm O O O O I ooootowoo'aimooommtotomtoio t—r—a PO Na) 0 O 010-4 ff 1 1 1 + + + + + + 1 i + + 1 i¢+ |¢+ I I zPulsed with 5 pCi of 14002 for 30 min, and 14C distribution determined 24 hr after pulsing 19 Table 5. Gross carbohydratez export from the 7th leaf of 'Montmorency' sour cherry during expansion in 1985 (55.6:13.5 cm2 final size) Leaf area . . Export .2 72:12:38: 3.3 5.9 - 6.3 11.3 - 7.0 12.6 - 7.8 14.0 - 8.5 15.3 - 8.8 15.8 - 10.5 18.9 - 11.2 20.1 - 12.2 21.9 - 17.8 32.0 - 20.0 36.0 - 26.3 47.5 - 55.0 98.9 + zPulsed with SyCi of 141.102 for 30 min, and 14C distribution determined 24 hr after pulsing. 20 Table 6. Gross carbohydratez export from the 10th leaf of ‘Montmorency' sour cherry during expansion (1985)(46.8:12.2 cm2 final size) Leaf area r7 . Export .2 $112213? 5.2 11.1 - 10.6 22.6 - 12.4 26.5 - 14.3 30.5 - 19.4 41.5 - 26.9 57.5 - 36.3 77.6 + 36.4 77.8 + 37.4 79.9 + 38.1 81.4 + 48.6 ' 103.8 + 55.7 119.0 + zPulsed with SyCi of 14C02 for 30 min, and 14C distribution determined 24 hr after pulsing. Table 7. 21 Gross carbohydratey export from the defoliatedz 'Montmorency' sour cherry during expansion cm2 final size). Leaf area Export %'final siie cm2 of control 3.4 6.3 — 4.9 9.1 - 9.5 17.7 tr 10.5 19.5 - 11.0 20.4 tr 14.3 26.6 - 20.9 38.8 tr 23.9 44.4 + 24.0 44.6 + 24.5 45.5 - 26.8 49.8 + 27.2 50.6 - 28.2 52.4 + 33.7 62.6 + 44.2 82.2 + 46.4 86.2 + 48.3 89.8 + 72.4 134.6 + +— yPulsed with SlpCi of 14C02 for 30 min, and 14C distribution determined 24 hr after pulsing. z Shoots were defoliated below the 10th leaf at the beginning of its expansion. 10th leaf of (1985)(53.8;I-_16.1 22 Effects of phyllotaxygon direction of translocation: Translocation followed closely the 2/5 phyllotaxy for the distal leaves near the pulsed leaf, but not for the less developed apical leaves (Fig. 3 and 4). The 7th and 8th and the 7th and 11th leaf obviously do not share translocation paths (Fig. 3). Angular distances between the 7th and 8th and the 7th and 11th leaf are 144° (Fig. 3). Part of the 9th leaf shares translocation paths with the 7th leaf, the angular distance between them is 72° (Fig. 3). The 10th léaf is also at an angular distance of 72° and the 12th leaf is at an angular distance of 0° to the 7th leaf (same orthostichy) (Fig. 3). Both the 10th and 12th leaf seemed to share the same translocation paths with the 7th leaf (Fig. 3 and 4b-d). Leaves distal to the 12th leaf imported from the 7th leaf regardless of their orthostichies. There was no translocation to leaves proximal to the pulsed leaf. Translocation out of the shoot was not determined. Fruit effects on direction of translocation: During stage I of fruit development leaves close to the apex (Fig. 5a), midpoint (Fig. 5b) or base (Fig. 5c) of fruiting shoots were pulsed. Apical and center leaves exported bidirectionally to apex and fruits. From the basal leaf no export could be detected. Export could have occurred to fruits or vegetative growth proximal to the examined shoot, however this was not examined. During stage II of fruit development leaves close to the apex (Fig. 50), midpoint (Fig. 5e) and base (Fig. 5f) were again pulsed. In all cases bidirectional export to the shoot apex and fruits was detected. During stage III of fruit development leaves close to the apex (Fig. 59) and the midpoint (Fig. 5h) exported bidirectionally. The leaf 23 Figure 3. Pattern of carbohydrate export developed from autoradiographs from the 7th leaf of non-fruiting 'Montmorency' sour cherry. Each field represents a leaf; leaves are numbered in sequence from shoot base to apex. Leaves of common orthostichies are shown in the same angle (schematic drawing). /./////////0 4 25 Figure 4. Autoradiographs (left) and corresponding shoots (right) showing the pattern of 4C-carbohydrate export from the 7th (a-d) and 10th (e-f) leaf of non-fruiting 'Montmorency' sour cherry during shoot elongation. a. Shortly after onset of export. Exporting to part of the 9th leaf, to the 10th leaf and the shoot apex. Traces can be detected in the proximal leaves. b. Exporting to part of the 9th leaf, to the 10th, 12th and the shoot apex, and traces only to the-11th leaf. Traces are also detected in petioles of other leaves. c. Exporting to the 10th, 12th, 13th leaf and the apex, and traces to the 9th and 11th leaf, and proximal petioles. d. Exporting to the 10th, 12th, 13th, 14th leaf, the apex and its axial shoot, and traces to the 9th and 11th leaf. e. Before initiation of export. f. Exporting to part of the 11th leaf, to the 12th, 14th and the shoot apex. Traces are detected in the 13th leaf and proximal leaves and petioles. 26 O igure A l ’ 27 close to the base (Fig. 51) exported basipetally to the fruit only. Translocation between leaves seemed to follow phyllotaxy, as was demonstrated for non-fruiting shoots (Fig. 3 and 4). Leaf to fruit translocation also seemed to follow distinct phloem connections (Fig. 5), since activity could not be detected in all fruits. However whether translocation followed the phyllotaxy could not be determined since orthostichies are hard to follow across the demarcation between current and last year's growth. Discussion The use of autoradiography was inadequate to determine the exact degree of leaf expansion for the initiation of EG- Variability in final leaf size and initiation of export between plants and years was very high, so that generally over a range of absolute leaf sizes some leaves exported while others did not. In 1983 E3 started for the 7th leaf at 27.2% (Table 3) and for the 10th leaf between 48~0 and 72.3% of full expansion (Table 4).In 1985 E3 started later, the 7th leaf started E3 after 47.5% (Table 5) and the 10th leaf at 77.6% of full expansion (Table 6). In the 1985 season, later initiation of E5 was accompanied by a greater final leaf area. Differences in growth between seasons might have been caused by different temperatures and light intensities, which could also explain differences reported for grape, which started 50 at 50% of full expansion in California (4), but only at 30% in Switzerland (7). The 7th leaf of sour cherry develops rapidly, expanding from 25 to 75% expansion in 6 days (data not shown); therefore differences between seasons in leaf age at initiation of 56 were small in relation to time. 28 Figure 5. Autoradiographs (left) and corresponding shoots (right) showing the pattern on14C-carbohydrate export from leaves of fruiting 'Montmorency" sour cherry shoots during fruit and shoot development. The pulsed leaf is marked with an arrow. a-c. Stage I of shoot development. d-f. Stage II of fruit development. g-i. Stage III of fruit development. 29 Fig? 5 a A \LI \i Q: , 1 O V- ' o If" 30 Small increases in leaf growth rate due to nutrition or temperatures, or decreases in photosynthetic rate due to light conditions may cause a delay in the initiation of E5. To the best of our knowledge the onset of E5 as a function of leaf position on the shoot has never been studied. Our results from both seasons (Table 3 - 6) indicate that leaves developing later in the season started 58 at a greater absolute leaf area and % of full leaf expansion. During the expansion of the 10th leaf more carbohydrates are available to the plant, because more expanded leaves are present and acting as sources. we propose that the initiation of CHzo export from a leaf capable of phloem loading is a function of CH20 availability in the total plant. To test this. CH20 supply to the plant was decreased by defoliation prior to devel0pment of the 10th leaf. The 10th leaf of the COHtVOI shoots started 56 at 77.6% of full expansion, as compared to defoliated shoots which, in support of the pr0posal, started considerably earlier between 44.4 and 52.4%. The mechanism involved in regulation of the initiation of 56 by CH20 availability is not known. Our study demonstrates that translocation in sour cherry, as in peach (11), apple, willow (5) and cottonwood (9) is limited to the leaf orthostichy. Leaves with angular distances of 144° used separate translocation paths, with the exception of the tenth leaf in which the entire blade was usually labelled when the seventh leaf was pulsed. This could have been caused by radial transport in the phloem. Leaves with angular distances of 72° shared some of their translocation paths. The 31 leaves closest to the apex did not have differentiated phloem connections with respect to their phyllotaxy and were therefore uniformly labelled. Carbohydrate translocation from leaves to fruits probably also followed the orthostichies, as is the case in peach (11). This is difficult to determine if the translocation occurs between tissues of different years. Sour cherry, with separate leaf and fruit buds, is not well suited for translocation studies along orthostichies between leaves and fruits. In 2-year-old apple seedlings translocation followed a spiral pattern (6) because the sieve tubes are arranged helically (8) Generally during stage II of fruit growth all leaves supplied new expanding leaves and fruits at the same time by bidirectional translocation. However, during stages I and III of fruit development the leaves closest to the fruits exported basipetally onlyu This differs from grape (7), where leaves close to the apex show acropetal translocation, some of the leaves distal to the fruit clusters show basipetal translocation and those in a small transition zone shows both. The rapid stages of fruit development (I and III) in sour cherry seemed to attract translocated carbohydrates most strongly and caused the development of a distinct zone of basipetal translocation. During grape fruit set (4) and veraison (7,14) translocation becomes markedly directed toward the clusters. The present study demonstrates that both initiation and direction of E5 in sour cherry are regulated by CH20 SUPPIY and demand. GFOSS export is limited within the autonomous orthostichies. 32 Literature Cited 1.Allard, H. A. 1942. Some aspects of phyllotaxy of tobacco. J. Agric. Res.64:49-55. 2. Christy, A. L. and C. A. Swanson. 1976. Control of translocation by photosynthesis and carbohydrate concentrations of the source leaf, p.329-338. In: Transport and transfer processes in plants. Nardlaw, I. F. and J. 8. Passioura (eds.) Academic Press, New York. 3. Fellows, R. J. and D. R. Geiger, 1974. Structural and physiological changes in sugar beet leaves during sink to source conversion. Plant Physiol. 54:877-885. 4.Hale, C. R. and R. J. Weaver. 1962. The effect of developmental stage on direction of translocation of photosynthate in Vjtj§_vinifera. Hilgardia,33:89-131. 5.Ho,'L. C. and A. J. Peel. 1969. Transport of l4C-labelled assimilates and 32P-labelled phosphate in Salix'viminalis in relation to pnyllotaxis and leaf age. Ann. Bot. 33:743-751. 6.Jankiewicz, L. S., R. Antoszewski, and E. Klimowicz. 1967. Distribution of labelled assimilates within a young apple tree after supplying 14602 to a leaf or shoot. Biol. Plant. 9:116-121. 7.Koblet, N. 1969. Nanderung von Assimilaten in Rebtrieben und Einfluss der Blattflaeche auf Ertrag und Qualitaet der Trauben. Hein- Hissenschaft 24:277-319. 8.Kursanov, A. L. 1984. Assimilate transport in plants. Elsevier, Amsterdam. 33 9.Larson, P. R. 1972. Interpretation of radiosotope translocation patterns in forest trees, p.277-288. In: Isotopes and radiation in soil-plant relationships including forestry. IAEA, Vienna. 10.Loescher, N. H., G. C. Marlow and R. A. Kennedy. 1982. Sorbitol metabolism and sink-source interconversion in developing apple leaves. Plant Physiol. 70:335-339. 11.Petrov, A. A. and P. B. Manolov. 1974. Factors determining the donor- acceptor connection in peach fruit nutrition. Proc. Int. Hort. Congr., Warsaw. Vol.1a, p.72. Abstract. 12.Quinlan, J. D. 1965. The pattern of distribution of 14carbon in a potted apple rootstock following assimilation of 14carbon dioxide by a single leaf. Annu. Rept. E. Malling Res. Sta. for 1964, p.117-118. 13.0uinlan, J. D. 1966. The effect of partial defoliation on the pattern of assimilate movement in an apple rootstock. Annu. Rept. E. Malling Res. Sta. for 1965,p.128-129. 14.Stoev, K. and V. Ivantchev. 1977. Donnees nouvelles sur le probleme de la translocation descendante et ascendante des produits de la photosynthese de la vigne. Vitis 16:253-262. 15.Thrower, S. L. 1962. Translocation of labelled assimilates in soybean. II. The pattern of translocation in intact and defoliated plants. Aust. J. Biol. Sci. 15:629-649. 16. Turgeon, R. 1973. Leaf development and phloem transport in Cucurbita p393: Transition from import to export. Planta 113:179-191. 17. Turgeon, R. and J. A. Nebb. 1976. Leaf devel0pment and phloem transport in Cucurbita pepo: Maturation of the minor veins. Planta 129: 265-269 . 34 18.Hebb, J. A. and P. R. Gorham. 1964. Translocation of photosynthetically assimilated 14C in straight-necked squash. Plant Physiol. 39:663-672. Section II Estimation of Net Carbohydrate Export from Sour Cherry (Prunus cerasus L. 'Montmorency‘) Leaves and Shoots 36 Abstract. The initiation of net carbohydrate export from leaves and shoots of 'Montmorency' sour cherry trees on Mahaleb rootstock was estimated “$109 carbohydrate (CHZO) balance modeling for determination of the empirical models. Using 1-year-old trees pruned to a single shoot, expansion of the 7th (from the base), and the terminal leaf, and shoot elongation were measured from bud break until terminal bud set. Comparable trees were used to measure daily C02 gas exchange of leaves and whole shoots as a function of their development. After destructive harvest, CHzO contents of the 7th and the terminal leaves and whole shoots were determined. Mathematical models were fitted to leaf area and shoot extension as a function of CHzo content, leaf and shoot CHZO content as a function of time and to respiration and net and gross photosynthesis as a function of leaf and shoot CHzo content. The 7th leaf and the terminal leaf started net export approximately at 17 and 51% expansion, respectively, which coincides with the onset of gross export. The whole shoot started exporting at 27% elongation. 37 Initial leaf expansion and shoot elongation in deciduous trees occurs at the expense of reserves stored during the previous season until the shoot's daily net photosynthetic rate (DPN), equals the CH20 accumulation rate. Leaf expansion and shoot elongation require import of CHZO from either reserves or from exporting leaves until the CH20 fixation rate exceeds utilization. This marks the beginning of net CH20 export and the point when a leaf or shoot becomes autonomous with respect to its CHZO supply. At this time a leaf or shoot is able to support other vegetative and reproductive growth and replenish CHzo reserves in the tree. Fruits and leaves develop concurrently early in the season and compete for CHZO from reserves or exporting leaves. Gross export (E5) refers to detectable movement of CH20 out Of the source leaf or shoot, while net export (EN) occurs when CHZO export exceeds import of CHZO and DPN exceeds CHZO accumulation rate. Kappes and Flore (11) demonstrated that 58 for sour cherry began between 27.2 and 98.9% of full leaf expansion depending on the leaf position and the growing season (11). Kappes and Flore (11) hypothesized that the initiation of CHZO export was regulated by supply from earlier expanded leaves and demand by the terminal growth or by other sinks within the plant. A hypothesis concerning source-sink effects on rate , rather than the initiation 0f. CHZO export was reported for tomato, where Khan and Sagar (12) demonstrated that a decrease of source strength by leaf removal or an increase of sink strength by growth regulator application to fruits accelerated l4C-export from leaves. 38 Various methods have been used to determine when EN begins in -deciduous fruit crops. Apple leaves were reported to start EN at 5% 0f full expansion (21). Apple shoots start EN 19 days after bud break, when shoots are 4 cm long (8% elongation), and 10 leaves are unfolded (10). Relative leaf expansion values for the start of EN in grape have not been reported, however, Martinez de Toda (15) reported that EN occurred after plastochron index 10. This is much later than suggested by Koblet's (13) data, which might be a result of the method used. Few studies on EN in woody perennials have been reported (10,15,21). Budgeting techniques using punched leaf disks have been used with annuals having large leaves (7,8,20); however most fruit tree leaves are too small to excise disks at an early stage without affecting leaf physiology, thus limiting the general use of this technique. An alternative method applicable to fruit trees (10,21) is the use of CH20 balance mOdeling (daily CH20 fixation “y; accumulation). Using this method, Hopkinson (8) showed that cucumber leaves started to export between 17 and 25% expansion, while Turgeon and Webb (20) found that pumpkin leaves started to export at about 45% expansion. The objectives of this study were to a) define when EN occurs for leaves and shoots of sour cherry, and b) determine if the magnitude or the initiation of EN is influenced by leaf position on the shoot during development. 39 Materials and Methods Plant material. One-year-old 'Montmorency' sour cherry trees on Mahaleb rootstock (Hilltop Orchards and Nurseries, Hartford, M1), were potted in 9-liter containers using a mixture of sandy loam and peat (3:1,v:v). A single shoot was allowed to develop, creating a simple uniform system to study the source-sink relationship. Trees were grown outdoors at the Horticulture Research Center, East Lansing, MI. Hater, fertilizer (20% N, 20% p205, 20% K20). and pesticides (Captan. Guthion. Kelthane) were used as necessary. Treatments were assigned in a completely randomized design. Ten trees were used for the measurement of leaf expansion and shoot elongation, 56 for whole shoot photosynthesis, 24 for the photosynthesis of the 7th leaf and 20 for the photosynthesis of the terminal leaf. Photosynthesis was followed by a destructive analysis for CHZO content which was expressed as a function of leaf area and shoot length. Curve fitting: Relationships between variables were determined by curve fitting with PLOTIT (2), a program designed for the fitting of linear and nonlinear regression models, as well as the graphic display of data. Models were chosen on the basis of the residual sums of squares, the coefficient of determination (r2), and the visual fit of the regression lines in relation to the observed data. Measurement of COB-fixation: Gas exchange was measured in an open system, as described by Sams and Flore (18). Photosynthesis of leaves and small shoots was measured in a leaf chamber (18), that of larger shoots in a 40-liter polyethylene bag attached to a large chamber where temperature, light and incoming water vapor pressure were controlled. 40 Unless otherwise stated standard conditions were as follows: photosynthetic photon flux density (PPFD), 1000‘pmol m‘zsec'l; 16 hr light, 8 hr darkness; day and night temperature, 25° and 15°C, respectively. The dew point of the air entering the chamber was held at 5°C, resulting in vapor pressure deficits of approximately 2.5 and 1.5 kPa during the light and the dark periods, respectively, for the leaf chamber, and 1.5 and 0.5 kPa for the large chamber. Photosynthesis (light period) and respiration (dark period) were determined at 2 hr intervals over a 24-hr period. The first measurement in the dark was taken at 25°C, to estimate respiration during the light period. Daily net photosynthesis (DPN), daily dark respiration (0RD) and, by addition, daily gross photosynthesis (DPS) were calculated for the 24-hr period. 0?", DPG, and 0RD (mg CH20 leaf'1 day‘l) or (mg CHZO shoot"1 day'l) were correlated with leaf or shoot size during leaf expansion or shoot elongation. Definitions: DP“ 8 net photosynthesis (day) - dark respiration (night) 0RD - dark respiration (day) + dark respiration (night) DPG ' DPN + DRD Measurement of carbohydrate accumulation: Areas (A) of the 7th and terminal leaves were estimated from length (L) and width (W) using equation 1 (11). A=L*H*0.65 (Eq.1) 41 Leaf area and shoot length of control plants were determined every 2nd day during leaf expansion and shoot elongation. Length of shoots and area of leaves used in gas exchange determination were measured. Then shoots and leaves were dried in a forced-draft oven (105°C) for 3 days and ashed for 6 hr (500°C) in a muffle furnace. Neight loss during ashing was used as an estimate of the total CH20 content. Dry ashing was used because dry weight alone (10) does not account for the mineral content, and wet ashing (7) limits sample size. Mineral contents (%) of the 7th and terminal leaves increased slightly with increasing dry weight (0R) (9) following equations 2 and 3, respectively, while shoot mineral content decreased with increasing DH (Eq. 4). Y - 5.232 + 3.306E-3 * 0w . (Eq.2) r2-0.287 Y . 4.111 + 3.7475-3 * 0v (Eq.3) r2-0.037 Y a 6.927 - 1.636E-4 * on + 3.2175-9 * 0w2 (Eq.4) r2=0.628 The relationship between CH20 content and leaf area or shoot length was determined and the resulting regression equations were used to estimate CH20 content during growth. Nonlinear regression models were fitted for CHZO accumulation y§_time, after the beginning of leaf emergence and bud break, and the difference between CHzo of day(n+0.5) and day(n-0.5) was used as an estimate of the CH20 accumulation rate of day". Estimation of the onset of export: Net CHzo export from a shoot or a leaf equals the DPN minus the c520 accumulation rate. Negative net export values represent net import. The point of transition from net import to net export was determined by comparison of daily values for Up“ and the CHZO accumulation rate. 42 Results Seventh leaf: Leaf area and leaf CH20 were linearly related (Fig. 1). indicating a constant specific leaf weight (SLW) during expansion. Carbohydrate accumulation data best fit Weibull's model (9) (Eq. 5 and 6, Fig. 2). Carbohydrate content increased mainly during the first 15 days and then remained constant. The accumulation rate reached a maximum of 38.4 mg/day at day 7. The coefficients for the model equation of leaf CHZO accumulation (in mg CHZO) and the difference equation (in mg CH20 day'l) as determined by nonlinear regression analysis are as follows: .8(1)-464.212 8(2)=0.236 B(3)=0.0849 B(4)=2.401 v . 8(1) * (1 - 91-13(2) + 8(3) * Mimi) (Eq.5) YD ‘ Y(x+0.5) - Y(x-0.5) (Eq-°) Where: Y 3 Leaf or shoot CHzo in mg YD 8 Leaf or shoot CHZO accumulation rate in mg day“1 X 8 Progressive days from leaf emergence or start of shoot elongation Estimated area at full expansion of the 7th leaf equaled 63.2 cmz, compared to the mean of the control plants used in the study, 64.3:16.8 cmz. The OP“, DPG and 0RD of the 7th leaf in units of CH20 leaf‘1 day'1 were linearly related to leaf CH20 content (mg CH20 leaf'l) (Eq. 79 Table 1, Fig. 3). Figure 1. Relationship between leaf area and carbohydrate content of the 7th leaf of 'Montmorency' sour cherry during leaf expansion, observations (circles) and fitted curve (line). . 44 Figure l. LEAF AREA (cmz) T l O O 4508 l O 0 no 750- (...-lv31 o‘Ho ow) 1N31Noo EIVBGAHOSBVO 3x731 45 Figure 2. Carbohydrate accumulation by the 7th leaf of 'Montmorency' sour cherry, starting at leaf emergence, observations (circles), fitted curve (solid line) and carbohydrate accumulation rate (broken line). 46 Figure 2. CARBOHYDRATE ACCUMULATION RATE (mg cuzo ddy“) c3 5; 53 :3 T 1 J a I n 'I- 6 r3 10 <3 c>cm> 0 do _u3 o c: c>c¢3 01 do ca 1o «o c>q<3 <3 oo <3 <3 Claw: <3 «3 _c3 cu <3 o <3<3db <3 db 01 / \ I I I I I C O i O O O In O In C In I" (D V’ n F" (1.31731 0113 5w) 114311403 31vedxl-loeavo 9‘73"! TIME AFTER LEAF EMERGENCE (ddys) 47 Figure 3. Daily gross photosynthesis (DPG) (A), (DPN) (8), and daily dark respiration (0RD (C) of the 7th af of 'Montmorency' sour cherry, observations (circles) and fitted curves (lines) at different leaf sizes during leaf expansion. daily net photosynthesis e 48 Figure 3 5 2°- 3? . °= h as 15- / “o ‘ O O O o 1' 0 go so. a g , . . w o 3 5- n 160 260 360 460 300 600 76c LEAF CARBOHYDRATE CONTENT (mg cup LEAF") 49 Table 1. Correlation coefficients (8(1) - 8(4)) and coefficients of determination of the regression equations for photosynthesis daily gross photosynthesis (DP ) respiration (0RD) for the 7th and terminal lea? 'Montmorency' sour cherry during growth. 8(1) 8(2) 8(3) 8(4) r2 Seventh 133:, 0?“ 3.064 0.340 0.540 DPG 28.568 0.319 0.440 0RD 9.716 0.0125 0.207 Terminal 19.31. DP" -7.348 0.235 0.936 0P5 -3.484 0.258 0.946 080 3.919 0.0234 0.309 M DPN 21.977 0.172 -.33lE-5 0.907 DPG 58.853 0.207 -.406E-5 0.911 DRD 34.308 0.0457 -.176E-5 0.249E-10 0.772 r— and daily dark and shoots of 50 Y = 8(1) + 8(2) * x (Eq.7) EN from the 7th leaf was initiated after 3 days, when 76.9 mg of CH20 were accumulated (leaf area = 10.6 cm2 and 17% full expansion) (Table 2). Five days after leaf emergence the cumulative CHZO balance (Table 2) was positive, indicating that the leaf had fixed more CHzo than it had consumed to that date. Daily EN reached a maximum of 161 mg CH20 per day by day 24. while total CHgo exported exceeded 3000 mg by day 29 (Table 2). TerminaliLeaf. Leaf area and total leaf CHZQ were linearly related (Fig, 4). The CH20 accumulation data of the terminal leaf best fit the sigmoid Gompertz model (1,9) (Eq. 8 and 9, Fig. 5). At day 2 CHZO accumulation rate reached a maximum of almost 10 mg , which" equaled 25.5% of the maximum rate estimated for the 7th leaf. Model equation coefficients for the terminal leaf are as follows: B(1)=156.471 B(2)=l.515 8(3)=0.171 -8(3) * X) Y . 8(1) * e(-B(2) * e( ) (Eq.8) YD ' Y(x+0.5) - Y(x-0.5) (ER-9) With definitions for Y, Y0 and X identical to those used in equations 5 and 6. Estimated terminal leaf area at full expansion was 18.1 cmz, while the mean for the control plants in the study was 18.015.7 cmz. op", 0P3. and DRD (CHZO leaf‘l day‘l) were linearly related to the leaf CH20 (mg CHZO ' leaf'l) (Eq. 7,Table 1, Fig. 6). Linear regression coefficients and r2 51 Table 2.. Thirty day simulated carbohydrate balance for the 7th leaf of 'Montmorency' sour cherry from the beginning of leaf emergence until full expansion. Progressive Giza Cl-ulativo UPI Cumulative Daily Cl-ulatm 4m acct-nation rate 6120 rate 0P); “Po"- Wort Iotuzo Isthzo' IgCHzo nothzo nsouzof nocuz°i day-1 day‘l dart 1 180° 29.3 13.0 1300 .500 .1603 2 23.8 50.3 20.2 33.2 -3.7 -17.1 3 29.1 7609 29.2 626‘ 001 .1‘05 4 33.4 106.2 39.9 102.3 6.4 -6.0 5 36.5 143.4 51.8 154.1 15.3 10.7 6 38.2 160.9 64.6 218.7 26.4 37.7 7 36.4 219.4 77.7 296.3 39.3 76.9 6 37.2 257.4 90.6 366.9 53.4 129.5 9 34.6 293.5 102.6 469.7 66.1 196.3 10 31.4 326.7 114.1 603.9 62.7 277.2 11 27.4 356.1 124.2 726.0 96.7 371.9 12 23.2 361.5 132.6 660.6 109.6 479.3 13 19.0 402.5 139.9 1000.7 121.0 596.2 14 15.0 419.4 145.7 1146.4 130.7 726.9 15 11.5 432.6 150.2 1296.5 138.7 863.9 16 6.5 442.6 153.5 1450.1 145.0 1007.5 17 6.1 449.8 156.0 1605.1 149.9 1156.3 18 4.2 454.9 157.7 1763.8 153.5 1308.9 19 2.8 458.4 158.9 1922.7 156.1 1464.3 20 1.8 460.7 159.7 2082.4 157.9 1621.7 21 1.2 462.1 160.2 2242.6 159.0 1780.4 22 0.7 463.0 160.5 2403.1 159.8 1940.0 23 0.4 463.6 160.7 2563.7 160.3 2100.2 24 0.2 463.9 160.8 2724.5 160.5 2260.6 25 0.1 464.0 160.8 2885.3 160.7 2421.3 26 0.1 464.1 160.9 3046.2 160.8 2582.1 27 0.0 464.2 160.9 3207.1 160.8 2742.9 28 0.0 464.2 160.9 3368.0 160.9, 2903.8 29 0.0 464.2 '160.9 3528.9 160.9 3064.7 30 0.0 464.2 160.9 3689.8 160.9 3225.6 52 Figure 4. Relationship between leaf area and carbohydrate content of the terminal leaf of 'Montmorency' sour cherry, observations (circles) and fitted curve (line) during leaf expansion. 53 Figure 4. l I I” II II I II I T I I O O O O O O O In 0 l0 0 0’) O 10 '0 I“) N N v- '- (I-d‘v’B‘l o‘Ho 5w) 1N31NOO BLVBCIAHOBHVO $131 LEAF AREA (cmz) 54 Figure 5. Carbohydrate accumulation of the terminal leaf of 'Montmorency' sour cherry during leaf expansion, observations (circles), fitted curve (solid line) and carbohydrate accumulation rate (broken line . 55 Figure 5. CARBOHYDRATE ACCUMULATION RATE (mg CH20 day") —l() “P1“?.I.‘l‘. 2C) 1 1004 Efl3~ () I O In F 250~ 'zoofi (.._-Iv3'l o‘Ho 5w) . 1N31NOO aivaoxHoaavo :NB'I TIME AFTER LEAF EMERGENCE (doys) 56 are shown in Table 1. The terminal leaf initiated EN (Table 3) after accumulating 72.9 mg of CH20 (leaf area = 9.2 cm2, 51% expansion). Cumulative CHgO export (Table 3) became positive after 10 days of growth. Maximum daily EN of the expanding terminal leaf was slightly over 25 mg. 16.4% 0f the maximum EN of the seventh leaf. Carbohydrate accumulation, photosynthesis and export by the 7th leaf and the terminal leaf are compared in Table 4. §fl£2£- Shoot CHZO content as a function of shoot length was best described by a second order equation (Fig. 7). Total shoot CH20 accumulation best fit the sigmoid Heibull's model (Eq. 5 and 6, Fig. 8). The CHZO accumulation rate reached a maximum of more than 700 mg day"1 by day 33. Model equation coefficients for the shoot are as follows: B(1)=19424.785 B(2)=0.0902 B(3)=0.02524 B(4)=3.815 DP" and OPS of the whole shoot in units of CHZO shoot‘1 day‘1 were best related to the shoot CHZO content (mg CH20 shoot’l) with a 2nd order equation (Eq. 10, Table 1, Fig. 9). DRD showed a 3rd order relation to the shoot CH20 content (Eq. 11, Fig. 9, Table 1). v - 3(1) + 3(2) * x + 3(3) * x2 (Eq.10) v - 3(1) + 3(2) * x + 3(3) * x2 * 3(4) * x3 (Eq.ll) 57 Figure 6. Daily gross photosynthesis (DPG) SA), daily net photosynthesis (DPN) (B), and daily dark respiration (DRD (C) 0f the terminal leaf 0f 'Montmorency sour cherry, observations (circles) and predicted curves‘ (line) at different leaf sizes during leaf expansion. 58 Figure 6 I 150 160 A B C . 4 1 q 3 < «I a 4 4 . i D IIITJIJI .1444. w n a m c w w w n c m u. m. “.98 0.5 9.. A18 6.26 Wk Ala: 35 9: 39: 5:2 mm 53 39.22629: :3 29.3.53: 53. is 300 .350 250 .i\ I 150 200 (mg cup LEAF 100 LEAF CARBOHYDRATE CONTENT 59 Table 3. Twenty day simulated carbohydrate balance for the terminal leaf of 'Montmorency' sour cherry from the beginning of leaf emergence until full expansion m3". C1120 leative 0P). leative Daily Cwlatm day: acct-Nation rate Ci'IzO rate "I export wort Immfll «$331 lUGQP swam: .1331 loan” marl My"1 our"1 1 9 5 43.6 2.9 2.9 -6.6 -40.7 2 9.8 53.3 5.2 6.1 o4.6 -45.2 3 908 6302 705 1506 .203 “706 4 9.5 72.9 9.8 25.4 0.3 047.5 5 9.0 . ' 62.2 12.0 37.3 2.9 -44.8 6 8.4 90.9 14.0 51.3 5.6 ‘39.6 7 7.7 99.0 15.9 67.3 8.2 ~31.8 a 70° 1“.4 17.7 “09 100‘ .2105 9 ‘03 ‘ 11300 1902 10‘01 1209 -809 10 5.6 119.0 20.6 124.7 15.0 5.6 11 4.9 124.2 21.8 146.6 16.9 22.4 12 4.3 128.8 22.9 169.5 18.6 40.7 13 3.7 132.8 23.9 193.4 20.1 60.6 14 3.2 136.3 24.7 218.0 21.5 81.8 15 2.8 139.3 25.4 243.4 22.6 - 104.1 16 2.4 141.8 26.0 269.4 23.6 127.6 17 2.0 144.0 26.5 295.9 24.5 151.9 18 1.7 145.9 26.9 322.8 25.2 176.9 19 1.5 147.5 27.3 350.2 25.8 202.6 20 1.3 148.9 27.6 377.8 26.4 228.9 60 Table 4. Comparison of 7th leaf and terminal leaf and the whole shoot of 'Montmorency' sour cherry. Parameter , 7th Terminal Shoot Area (cmz),Length (mm) 62.3 18.1 603 (Full Size) Area (cmz),Length (mm) 10.6 9.2 160 (Start of export) CHzO content (mg) 464 149 19.4 (Full size) CH 0 content (mg) 76.9 72.9 1531 (Sgart of export Expansion (%) 17 51 27 (Start of export) _ CHgO accumulation (%) 17 49 7.9 (S art of export) Days after emergence 3 4 17 (Start of export) Net photosynthesis 29.2 9.8 277.5 (mg day‘ ) (Start of export) Export maximum 161 27 ' 2.1 (m9 day‘l) Net photosynthesis (same as export maximum) (Maximum) 61 Net export of the whole shoot started after it had accumulated 1531 mg of CHZO (shoot length = 160 mm, 26.5% of full extension) (Table 5). The estimated cumulative photosynthesis always exceeded CHzo accumulation, which likely results from an overestimation of DPN at the beginning of shoot development. Modeling does not allow us to estimate these relatively small changes in the CH20 balance in the initial phase of shoot development accurately enough to calculate when the balance becomes positive. However, whole shoot EN began at day 15. and reached a maximum rate of more than 2100 mg day’1 after 61 days (shoot length = 600 mm) with approximately 21 to 22 leaves. Discussion Methods involving heat girdling of the petiole or measuring leaf CH20 accumulation using leaf disks to determine EN from developing leaves are not adequate for sour cherry leaves. Heat girdling has been used in grape (15), although its disadvantages include the potential damage to the leaf, the inhibition of the movement of non-carbohydrate substances to and from the leaf and the difficulty in estimating import and export quantitatively. The removal of leaf disks can also physically affect photosynthesis and export. These problems were avoided by developing empirical models for leaf and shoot CHZO accumulation and C02 935 exchange in sour cherry. The models of Neibull (9) and Gompertz (1,9) gave the best fit for leaf and shoot £320 accumulation in sour cherry and were used to estimate the onset of CHzo export, These models have also been reported for other sigmoid growth phenomena (1,9). 62 Figure 7. Relationship between length and carbohydrate content of the whole shoot of 'Montmorency' sour cherry during leaf expansion, observations (circles), fitted curve) (line). 63 Figure 7. (3.100143 o‘Ho 5w) .—0L x 1N3_LNOO aiwoxwoaavo .LOOHS SHOOT LENGTH (mm) 64 Figure 8. Carbohydrate accumulation of the whole shoot of 'Montmorency' sour cherry during shoot elongation, observations (circles), fitted curve (solid line) and carbohydrate accumulation rate (broken line). 65 Figure 8. CARBOHYDRATE ACCUMULATION RATE (mg CHZO day“) O O O O O K) O 10 '9) ID 1, “P ‘1' . I ?f c: I\ (D 'CID /..o G) 'CID CD 0 000 / 0 0'0 0 o . o / o o 0 an "In 0 0 mo» / (1300:” / l" @ O'I. o nooo o / 01“ L." I 0wa / 00 mm. o 0000:. o 00: .0 _o \ O ’01) F) o I i0|® \ O ('4! \ 0.61. . 0.1! O \ CI 0 -64 \ n' “)b \ ,- \ ‘53 o 3 I I I ‘I I I r I ' ‘3 In C In C 10 O N N III- '— (x-iOOHS OZHO 5w) e-OL x 1N31NOO aivadAHoeavo .LOOHS TIME AFTER BUD BREAK (days) 66 Egguge 9é)Daily gross photosynthesis (DP ) (A), daily net hotos thesis N s and daily dark respiration DR ) (C) of the w ole 5 act of 'Montmorency' sour cherry, observations ? circles) and fitted curves (lines) at different shoot sizes during shoot elongation. 67 .Figure 9. A m3 .Lsaafiacge .oxa >3 f :uwufimfi. m-m(w,.w-m-m 4w 3.3%.... Es... 26 T I5 9&8 Oar-O OE 20...ng g g SHOOT CARBOHYDRATE CONTENT X 10‘J (mg CH,O SHOOT") 68 Table 5. Sixty-five day simulated carbohydrate balance for the whole shoot of 'Montmorency' sour cherry from bud break until full expansion. mam Gizo o-umm no, mum. omy 84.31881" days emulation rate c1120 rate DP). export Wt new ”0'20 40120-3sz ~sz new“ ur‘ day-1 our-1 . 1 4.3 5.1 22.5 22.5 18.5 17.7 2 7.5 10.9 23.9 46.7 16.3 35.8 3 12.0 20.5 25.5 72.2 13.5 51.7 4 17.8 35.2 28.0 100.2 10.3 65.2 5 25.2 56.5 31.7 131.9 6.5 75.5 6 34.2 85.9 36.7 168.7 2.5 82.7 7 45.2 1250‘ ‘30, 211.2 .107 “a, 8 58.1 176.8 52.3 264.4 05.8 87.6 9 7301 2‘201 630‘ 327.9 -507 ”07 1 90.3 323.5 77.3 405.1 013.0 61.6 11 109.7 423.2 94.2 499.3 -15.5 76.1 12 131.3 543.4 114.5 613.8 -16.9 70 4 15503 038.8 836-; 75203 '16.8 6503 14 181.5 854.6 166.5 918.8 .14.9 64.3 15 205.8 1049.9 158.9 1117.8 -.0.9 67.8 16 240.2 1274.7 35.8 1353.6 .3 78.9 17 272.4 1530.8 277.5 1631.1 5.1 100.3 18 308. 1820.0 324.0 1955.2 .7 135.2 15 341.6 2143.8 375.5 2330. 33.9 166.9 20 377.8 2503.4 431.8 2762.5 .0 . 21 414.8 .6 492.9 3255.3 78.1 355.7 22 451.9 3333.0 558.5 3813.8 106.6 .9 23 488.8 3803.2 628.3 .1 139.6 838.8 24 524.8 4310.0 701.8 5143.9 177.2 833.5 25 559.1 4862.0 778.6 5922.5 215.5 1070.4 28 591.6 5427.7 858.0 6780.5 266.4 27 621.5 6034.8 539.4 7715.9 317.5 1885.3 28 848.1 6685.8 1021.5 8741.8 373.8 2072.0 25 670.5 7325.8 1104.9 5848.7 433.9 2516.8 30 885.4 8010.6 1187.4 11034.1 488.0 31 703.1 8707.4 - 1268.7 12302.8 565.6 3595.4 32 711. 9415.4 1348.0 13650.8 636.5 .4 34 711.5 10542 7 1497.5 16573. 766.2 :7-3 4 35 703.0 11550.7 1567.1 15143.2 . 55:5 5 36 068.7 2237.2 1.2200 1977202 "Jo‘ 1223.3 37 666.3 12326.6 16:2.3 2146~ 5 1.23.4 8... 9 33 643.9 13563.: 1747.5 232-2.. 1103 7 952:.5 39 05"; 1321302 1.38.0 25486.00; 1.35.; 7:12-50; 40 550.5 14311.1 1543.4 25653.4 1252.: 12441.4 41 543.4 15373.4 1253.9 23737.4 1240.5 .2252.3 4' 5 3.7 15557.2 1915.5 306:1.1 14-5.. .4.::.: 43 462 3 15350.3 1351.3 32565 4 1469 2 1:4-:.. 44 419.: 15521.2 1976.7 3456! 1 15:9.1 .::§5.. 45 376.9 17215.4 2002.3 35533.3 152: 4 .:-:§ 9 4o .34.: 1757:.1 2022.5 .6511 3 .664 1 2.45.: 4 254 3 17889-3 2033.5 40651.5 1135.5 2: :2 . 48 255.2 .516.. 2054.1 42705 6 1796.9 24561.9 49 218 5 15400.4 2066.2 44771.7 1847.3 25371.4 50 185.4 15602.1 2076.2 46647.9 1590.3 25245.8 51 155.0 18771.9 2084.4 48932.2 1929.4 38150.4 52 117.9 1.5123 2091.0 51323.2 19.3.: 3.45.. 53 104.1 19028.5 2096.4 53119.6 1992.2 34091.. 54 83.6 15122.0 2100.7 55220.3 2017.0 36098.3 55 66.2 19196.5 2104.0 57324.3 2037.5 35127.8 50 51.5 19255.1 2106.6 59431.0 2055.0 40175.9 57 39.7 19300.4 2108.7 61539.5 2069.3 42239.2 58 30.0 19335.0 2110.2 63049.8 2060.2 44514.8 59 22.3 19360.9 2111.3 65761.1 2089.0 46400.2 60 16.4 19330.1 2112.2 67873.3 2095.8 48493. 61 11.8 19394.0 2112.8 69986.0 2101.0 50592.0 62 8.3 19403.9 2113.2 72099.2 2104.9 52695.3 63 5.8 19410.9 2113.5 74212.7 2107.7 54801.8 64 4.0 19415.7 2113.7 76326.4 2109.7 56910.7 65 2.7 19418.9 2113.9 78440.3 2111.2 59021.3 69 DPN, 0P6, and DRD were linearly related to leaf area and CHZO content (Fig. 3 and 6), resulting in approximately constant rates when expressed on an area basis. In contrast, Sams and Flore (18) reported that PM in developing sour cherry leaves first increased, then and remained constant thereafter. The proposed model for DPN, however, should not be extrapolated to the period after full leaf expansion for several reasons. First, different source-sink relationships could influence DPN. Fruiting trees reportedly have higher photosynthetic rates than non-fruiting trees (14), although this relationship has not been consistent for sour cherry (19). Second, linearity might be lost within a tree canopy, where the light intensity decreases during leaf expansion. Third, leaf PN decreases during senescence (18). The correlation of UP", 0P5, and 0RD with leaf CH20 content was much closer for the terminal leaf than for the 7th leaf. This was probably due to greater uniformity of source-sink relationships during expansion of the terminal leaves. The slopes of the regression lines for DPN 30d 0P3 represented by the parameter 8(2) were greater for the 7th leaf than for the terminal leaf. This indicates greater rates of photosynthesis for the 7th leaf than for the terminal leaf (Table 4), not only because of its greater size but also in terms of unit leaf area. A reduced leaf size is generally observed before terminal bud set, although the reasons for this are not known. The reduction in PN per unit leaf area is probably due to intrinsic differences in photosynthetic capacity. A reduction of PN due to feedback inhibition is not likely, since no marked diurnal rate changes were observed (data not shown). The DPN and DPG of the whole shoot were related to the shoot CH20 content by a 2nd 70 order equation. The slope decreased with shoot CH20 accumulation. The shoot's leaf area was probably proportional to the CH20 content, as is the case in apple (10). This supports the hypothesis that distal leaves have lower photosynthetic rates per unit area. DRD ShOWEd 3rd order relations to the shoot CH20 content, following a similar pattern as DPN and DPG (Fig. 9). The models for CHgO accumulation and DPN indicated that the onset of EN occurred at approximately 17% and 51% of full expansion, and 27% of full elongation, for the 7th and terminal leaves and the shoot, respectively (Table 4). In an earlier study with sour cherry we reported (11) that EG from the 7th leaf starts between 27.2% and 98.9% expansion and from the tenth leaf between 48.0% and 77.6% expansion. Net CHZO export did not start later than E3, indicating that CH20 import stops close to the time when export starts. These findings are in contrast to those reported for grape, in which import and export occur simultaneously for leaves between 30% and 50% expansion (13). Our results for the OUSEt 0f EN from leaves are similar to those reported for herbaceous plants (8,20). He found, however, that in terms of degree 0f leaf expansion, EN for sour cherry leaves started much later than reported for apple leaves (21). It is difficult to compare results of export initiation, since neither time after emergence, nor absolute or percent expansion are closely linked to the mechanism involved (11). Apple shoots were 4 cm long and had 10 unfolded leaves when EN began (10), while sour cherry shoots were 16 cm long and had an almost fully expanded seventh leaf. The apple shoots had used 831 mg of CHZO for 71 accumulation and respiration (10), while the cherry shoots had accumulated 1531 mg, not accounting for respiration. This indicates that the sour cherry shoots started export at a greater size, even though leaf number was similar. The differences observed betweeen sour cherry and apple could have resulted from different growing conditions. The earlier start of EN from the 7th leaf, as compared to the terminal leaf, supports the hypothesis of Kappes and Flore (11) that Chzo supply and demand regulate the time of onset of export. Net export for the 7th and terminal leaf occurred at approximately the same absolute size (10.6 and 9.2 cm2) (Table 4), although the percentage of full expansion was much greater for the terminal leaf (51%) than for the 7th leaf (17%)} Reaching a certain absolute leaf size, however, does not seem to trigger export (ll). Leaves begin making a positive contribution to the CHzo balance of the plant after a short period of expansion. The overall CH20 balance became positive after 5 days in the 7th leaf (Table 2) and after 10 days in the terminal leaf (Table 4). After this time leaves stopped being net consumers 0f CH20 produced by the rest of the plant. The whole shoot started to export 17 days after bud break, at 27% of full elongation, 7.9% CH20 accumulation and when the 7th leaf was almost fully expanded. The plants studied did not bore fruits, thus demand for CHZO came from the shoot, root growth, growth of the trunk and replenishment of CHZO reserves. He speculate that replenishment of reserves was a strong sink, since export from the shoot started at a time when shoot CHzo accumulation rates were still increasing. 72 This study demonstrates that leaves start EN soon after initiation of their expansion. Shortly after EN starts leaves have produced more CH20 than they use for development and become net sources of CH20 for the plant. Shoot cumulative EN remains close to 0 indicating that the shoot does not use much of the reserves, although EN takes 17 days to start. Even the terminal leaf, which develops latest in the season when growth has slowed down, produces more CHZO than needed for its development. Near the end of leaf or shoot expansion, cumulative DPN exceeds the cumulative CHZO several fold. The models in this study were developed for non-fruiting plants, trained to 1 shoot, which is a much simpler system than a bearing fruit tree. Fruits could cause an earlier initiation of export from leaves and shoots if sour cherry fruits have the first priority for CH20, 65 has been speculated for other plants (5,6). The shoots in our experiment exported, according to our model (Table 6), a maximum of more than 29 of CH20 per day, which is equivalent to the CHZO accumulated by 3 mature fruits in 57 days. Literature Cited l.Causton, D. R. and J. C. Venus. 1981. The biometry of plant growth. Edward Arnold, London. 2.Eisensmith, S. P. 1984. PLOTIT. Ein interaktives Graphikprogram. (Version 1.0). 73 3.Flore, J. A. and C. E. Sams. 1985. Does photosynthesis limit yield of sour cherry (from cerasus). In: A. Lakso and F. Lenz (eds.). Regulation of Photosynthesis in Fruit Trees. N. Y. State Agr. Expt. Sta. Spec. Bull. (In press) 4.Hale, C. R. and R. J. Weaver. 1962. The effect of developmental stage on direction of translocation of photosynthate in gill—5 vinifera. Hilgardia 33:89-131. 5.Hansen, P. 1967. J~4C-Studies on apple trees. I. The effect of the fruit on the translocation and distribution of photosynthates. Physiol. Plantarum 20: 382-391. 6.Hansen, P. 1977. The relative importance of fruits and leaves for the cultivar-specificogrowth rate of apple fruits. J. Hort. Sci. 52:501- 508. 7.Ho, L. C. and A. F. Shaw. 1979. Net accumulation of minerals and water and the carbon budget in an expanding leaf of tomato. Ann. Bot. 43:45-54. 8.Hopkinson, J. M. 1964. Studies on the expansion of the leaf surface. IV. The carbon and phosphorus economy of a leaf. J. Expt. Bot. 15:125-137. 9.Hunt, R. 1982. Plant growth curves. Edward Arnold, London. 10.Johnson, R.S. 1982. A computer simulation of the carbon balance of a growing apple shoot and its application to different climatic and growing conditions. Ph.0. Thesis. Cornell University. 74 11.Kappes, E. M. and J. A. Flore. 1985. The influence of phyllotaxy and stage of leaf and fruit develOpment on the initiation and direction of gross carbohydrate export from sour cherry (M cerasus L. 'Montmorency') leaves. In preparation. 12.Khan, A. and G. R. Sagar. 1969. Alteration of the pattern of photosynthetic products in the tomato by manipulation of the plant. Ann. Bot. 33:753-762. 13.Koblet, N. 1969. Handerung von Assimilaten in Rebtrieben und Einfluss der Blattflaeche auf Ertrag und Qualitaet der Trauben. Hein- Nissenschaft 24:277-319. 14.Lenz, F. 1977. Einfluss oer Frucht auf Photosynthese und Atmung. Z. Pflanzenernaehr. Bodenk. 140:51-61. 15.Martinez de Toda, F. 1982. Metodo de evaluacion de la zona parasitica apical de los pampanos en Vitis vinifera L. Vitis 21:217-222. 16.Neales, T. F. and L. D. Incoll 1968. The control of leaf photosynthesis rate by the level of assimilate concentration in the leaf: A review of the hypothesis. Bot. Rev. 34:107-125. 17.5ams, C. E. 1980. Factors affecting the leaf and shoot morphology and photosynthetic rate of sour cherry (m cerasus L. 'Montmorency'). Ph.0. Thesis. Michigan State University, East Lansing. 18.Sams, C. E., and J. A. Flore. 1982. The influence of age, position, and environmental variables on net photosynthetic. rate of sour cherry leaves. J. Amer. Soc. Hort. Sci. 107:339-344. 75 19.Sams, C. E., and J. A. Flore. 1982. Net photosynthetic rate of sour cherry (Prunus cerasus L. ‘Montmorency' ) during the growing season with particular reference to fruiting. Photosynthesis Research 4:307- 316. 20.Turgeon, R. and J. A. Webb. 1975. Leaf development and phloem transport in Curcurbita 2329: Carbon economy. Planta 123:53-62. 21.Hatson, R. L. and J..L Landsberg. 1979. The photosynthetic characteristics of apple leaves (cv. Golden Delicious) during their ‘ early growth, p.39-48. In: R. Marcelle, H. Clijsters and M. van Poucke (eds.) Photosynthesis and plant development. Dr H. Junk, The Hague. Section III Sour Cherry Fruit Carbohydrate Balance during DevelOpment, from Empirical Models of Carbohydrate Accumulation, Net Photosynthesis, Gross Photosynthesis, and Dark Respiration 77 Abstract. A fruit carbohydate (CH20) balance was developed from models derived from measurements of CH20 accumulation and 002 935 exchange from shortly after full bloom to maturity. Daily gross photosynthesis (DPG) never compensated for daily dark respiration (0RD) under the conditions tested. DPG increased during stage I of fruit development and decreased thereafter as fruit chlorophyll decreased and anthocyanin increased. DPG 35 a percentage 0f 0RD decreased during the entire period. Fruit gross photosynthesis accounted for 11.2% of the total CH20 utilized during development of the fruit, while 88.8% had to be imported. Fruit gross photosynthesis contributed 19.4%, 29.7% and 1.5% of the CHZO used during stages I, II and III of fruit development, respectively. 0f the total CHZO used, 30.9% was used for dark respiration and 69.1% was incorporated into fruit dry matter. The share of Cfizo used by the fruit for dark respiration was 32.7%, 70.9% and 19.9% during stages I, II, and III of development, respectively. Sour cherry fruit photosynthesis contributes a significant portion of the CHZO used for fruit growth and dark respiration. The major part of this contribution is made during stages I and II of fruit development when the leaf area of the tree is Still small. Use of CHZD for dark respiration is high during the lag phase (stage II), probably due to synthesis of lignin and lipids, during pit hardening and embryo development. Dark respiration is intermediate during cell division (stage I) and low during cell expansion (stage III). 78 The influence of fruit photosynthesis on subsequent fruit size and fruit set is not well documented. Fruit photosynthesis, however, appears to contribute to, and perhaps limit yield in grape (9, 10, 13, 17) and apple (3, 16). During bud break and immediately thereafter vegetative and reproductive buds compete for the CHzo reserves stored within the plant, leaves and shoots become net exporters. For sour cherry the minimum leaf to fruit ratio for maximum fruit size has been estimated to be 1.5 to 2 (35-50 cm2 fruit'l), which in practice is usually exceeded (19,8). Thus fruit photosynthesis may make a significant CHzo contribution early in the season during fruit set and cell division when competition for CHZO is high, or later in the season in cases of excessive fruit load (less than 1.5 leaves per fruit) or severe defoliation. Most of the work related to fruit photosynthesis has focused on the effects of environmental factors (16, 9). Noga and Lenz (16) observed that evolution of C02 from apple fruits was much greater in the dark than in the light and suggested that this may alter the net photosynthetic balance of the plant. CHzo fixed by grape berries is assumed to be of minor importance in the CH20 balance of the fruit, even though in some cultivars it compensates for most of the fruit respiration (9, 10, 17). Koch and Alleweldt (13), however, concluded that fruit photosynthesis is an important factor for growth, especially of the young grape berry. A survey (1) focusing on the contribution of fPUlt photosynthesis to the CHZO balance of the reproductive organs in several species showed that the contribution ranged from 2.3% in guercus macrocarpa to 64.5% in Acer platanoides. In the closest relative 79 of sour cherry studied, Prunus serotina, the fruit contributed 19.2% of the CHZO used for its development. Similar CH20 balance calculations are needed to estimate more precisely the fruit photosynthetic contribution of commercially produced fruits. The main objectives of this study were to determine a) the share of CH20 supplied by fruit photosynthesis in sour cherry, b) the share of CHZO used by dark respiration during the different stages of fruit development, c) the share of CH20 import required and the change of import rates during fruit development. Materials and Methods Plant material: Branches with an average to high fruit load (2-6 leaves/fruit) were randomly selected from the outer edge of all quadrants of the tree, approximately 2 m from the ground, in a 12-year- old sour cherry ('Montmorency' on Mahaleb) orchard at the Horticulture Research Center, East Lansing, MI. Branches were cut, immediately immersed in water and transported to the laboratory. Bases were then recut under water to eliminate air from the vascular system and branches were used for £02 gas exchange determination. Previous studies (20) indicated that this procedure gives results equal to that of attached branches for leaf gas exchange characteristics, if the precautions of Lakso (15) are considered. 80 Curve fitting: Mathematical relationsnips between variables were determined by curve fitting with PLOTIT (5). Models were chosen on the basis of the residual sums of squares, the coefficient of determination and the visual fit of the regression lines in relation to the observed data. Measurement 0f C93 gas exchange: Fruit gas exchange was measured with an open system as previously described by Sams and Flore (19). Photosynthesis and dark respiration were determined at 4-day intervals from full bloom until maturity, using 4 attached fruits per assimilation chamber, replicated with 4 different shoots and 4 chambers. Standard assimilation chamber conditions were: photosynthetic photon flux density, 1000 pmol m"2 sec'l, 16 hr light, 8 hr darkness, day and night temperature, 25° and 15°C, respectively. The dew point of the air entering the chamber was kept at 5°C, resulting in vapor pressure deficits of approximately 2.5 and 1.5 kPa during the light and the dark periods, respectively. The fruits were kept in the chamber for 24 hr while photosynthesis (light period) and dark respiration (dark period) were determined at 2-hr intervals. The first measurement in the dark was taken at 25° to estimate respiration during the light period. Daily net photosynthetis (DPN), daily gross photosynthesis (0P3) and daily dark respiration (0RD) were calculated in terms of mg CH20 fPUlt'l day-1. Definitions: DPN a net photosynthesis (day) - dark respiration night DRD = dark respiration (day) + dark respiration night DPG - DPN - DRD 81 Fruit DPN, DPG and 0RD were correlated with fruit CH20 content. Using these regression equations and the CH20 accumulation equation, data were calculated for the photosynthetic parameters as a function of time over 57 days of fruit development. Cumulative Ups and DRD were calculated from fitted equations at different times of fruit development and for the entire period of fruit growth. Measurement of carbohydrate accumulation: Fruit growth was estimated from observations made on 20 fruits which were selected randomly and tagged 5 days after full bloom. Suture diameter (S) and length (L) were measured using calipers (precision s 0.1 mm) at 2-day intervals at 10 a.m. Fruit volume (V) was estimated (Eq. 1) assuming that the fruit is a sphere whose diameter equals the mean of suture diameter and length (22). 4/3 * Pi * ((s + L) * 0.5 * 0.5)3 (Eq.1) < ll Fruits (n 16) were sampled at random from the same trees used for photosynthesis and CH20 accumulation studies at 4-day intervals during fruit development. Fruit volume was estimated and composite samples were dried in a forced draft oven for 3 days and ashed at 650 °C for 7 hr in a muffle furnace. The weight loss per fruit during ashing was used as an estimate of fruit CHZO content (12). Relative mineral content decreased during fruit develOpment following a quadratic curve (Eq. 2). v - 6.341 - 1.176E-2 * Du + 8.312E-6 * bwz (Eq.2) r2=0.77l The regression between total fruit CHzo content and fruit volume was used to convert fruit volume increase to CH20 accumulation. 82 Because of the large variation in final fruit sizes, the CHzo accumulation data were normalized by dividing all data by the final CH20 content of the respective fruit. The normalized data were then multiplied by the mean of the final fruit CH20 content. The values obtained were correlated with time to obtain a CHzo accumulation curve. The final value of this curve was used as an estimate of the total CH20 accumulated during the entire period of fruit growth. Daily differences from this curvve were used as an estimate for the rate of CH20 accumulation. Stages of development were defined according to Tukey (22), stage I being the first period of rapid growth (days 1-22 after full bloom), stage II the lag phase (days 23-35 after full bloom) and stage III the second period of rapid growth (days 36-57 after full bloom). Results Fruit DPG (Fig. 1A) increased with fruit CHZO content during stage I. DPG peaked during stage II and decreased as the fruits lost chloroohyll (data not shown) and turned red. Fruit DPN (Fig. 18) was negative during the entire course of fruit development. It decreased as the fruit CHZO content increased, reached temporary minimum during stage II, then increased slightly and decreased further during stage III. Fruit 0RD (Fig. 1C) increased with the fruit CH20 content during stage I, peaked during stage II, then decreased to its original level during stage III. 83 Figure 1- C02 gas exchange of fruits as a function of fruit carbohydrate content during development of 'Montmorency' sour cherry fruit, observations (circles) and fitted curves (lines). A. Daily gross photosynthesis, B. Daily net photosynthesis and C. Daily dark respiration. . 84 Figure 1.- 1W ‘- 34 m“! I 4 o 2 7:00 0.20 g has. m8 >3 < I . 7% 5% FRUIT WEOHYDRATE CONTENT mg CH,O FRUIT") 300 85 DPN, UPS, and 0RD as a function of fruit CH20 could be simulated best using a multiplicative exponential model to which a linear part was added (Eq. 3, Table 1). Y=B(1)+B(2)*X+B(3)*(XB(4))*e(3l5)*x) (Eq.3) where: Y=DPN, 095 or 0RD (mg CH20 day’ll X=cumulative fruit CHzo (mg CHZO) Fruit CHZO accumulation (Fig. 2) followed the double sigmoid pattern of sour cherry fruit growth (22), and the CH20 accumulation curve could best be modeled using a general logistic equation with a saddle (11) (Eq. 4, Table 1). The resulting curve for the growth rate (Eq. 5, Table 1) exhibits peaks during stages I and III and a minimum during stage II. y=3(1)/(1+e(B(2)+B(3)*X+B(4)*X*X+B(4)*B(4)*X*X*X/(3*B(3)))) (Eq.4) YD Y(x+o.5) - Y(x-o.5) (EB-5) Where: Y 8 cumulative fruit CHZO (mg CH20) X time after full bloom (days) YD daily CH20 accumulation at day x The simulated cumulative CHZO balance for the fruit (Table 2) indicates that 30-9% of the CHZO was utilized for dark respiration, while 69.1% was incorporated into the fruit. The fruit imported most of the CH20 it used from external sources (i.e., leaves or reserves). However, a significant share of the CHZO was fixed by the fruit itself. Under the given conditions, fruit gross photosynthesis accounted for 86 Table 1. Regression coefficients for 'Montmorency' sour cherry fruit daily net photosynthesis (0PM). daily gross photosynthesis (0P5) and dell] dark respiration (0RD) as a function of carboh drate content, and of carbohydrate accumulation (CHZO) as a function (i tlme,dur1ng frolt growth DPN DPG . RD CH20 3(1) -0.397 2.007 -2.757 513.9 3(2) -0.522£-2 -0.467E-2 -0.679E-3 9.354 3(3) -0.330£-17 0.1525-7 -0.411£-3 -0.947 3(4) 9.375 4.525 4.372 0.3455-1 3(5) -0.433£-1 -0.302£-1 -0.231£-1 -- r2 0.624 0.903 0.551 0.929 87 Figure 2. Relationship between time after full bloom and carbohydrate accumulation of 'Montmorency' sour cherry fruit during development, observations (circles), fitted curve (solid line), carbohydrate accumulation rate (broken line). CARBOHYDRATE ACCUMULATION RATE 88 Figure 2. (mg CHZO day“) '0 O IO 0 O 7") N N c- ‘- l 1 L I J L I l O (O o 0 not 0 o , o - oo .— ’ —8 m0“- " O .— ‘" ’ - .- = 0‘; _ K, oomodno \ O o “"0 ‘ ‘ ‘0 CI! 000 -2 4— o 000. \ \ 0‘” . \ - 0 0'0: I \ = o \ —,9, Q o...» l o o. I L 001 O /- / 0 II( / <3 CD-i 4’ “-53 Conn. /. .0137. .- — \ \ o \ ‘ ho \ v- 8 8 8 B CO v- I TIME AFTER FULL BLOOM (days) .89 .moocuoz ace m_upcmumx c. uma_cummu me mpmaos .ou_c_qem sage cm>_cma ~ .m.nm. m.=ea Am.ea. m.eam Am.a~. a.me Aa.=o. “.354 Au-a+mu km a 9:26 33¢ 22.3.5 25.». .xucocoscoz. mo 38355:: 5 oiu .33 we a 6.5 95 3:23 323.3336 omen—=53 .N «3: 90 11.2% of the total CH20, which was 30.1% of fruit dark respiration (Table 2). The percentage of CHZO contributed by fruit gross photosynthesis was highest during stage II of fruit development (29.7%) and lowest during stage III (1.5%)(Table 2). The percentage of CHZO used by dark respiration was also highest during stage II (70.9%) and lowest during stage III (19.9%)(Table 2). The gross photosynthesis as a percentage of dark respiration (Table 3) decreased markedly during the course of fruit growth. Throughout the period of its development, the fruit remained a net importer of CH20 (Table 4), since the OPE never exceeded the CH20 accumulation rate. The period of greatest CH20 import (Table 4) coincideowith the two peaks for growth rate (Fig. 2), 14-15 and 43 days after full bloom. Discussion The importance of fruit photosynthesis for the CHZO production of a tree becomes evident only if a fruit CHZO balance is calculated. Under the given conditions sour cherry fruits produced a substantial share (ll-2%) 0f their CH20 needs. Sour cherry fruit photosynthetic contribution to its CHZO balance is relatively low when compared to most species surveyed by Bazzaz and coworkers (1). One must consider that the sour cherry CHZO balance was obtained at high light intensities which are only found early in the season, at the canopy surface or after severe defoliation. However, since the highest percentage contribution 91 Table 3. Time course of daily gross photosynthesis (DPm as a percentage of daily respiration (0RD)(experimental data) Days after DPG/DRD sd full bloom % 4 86. 4 9.5 8 61.1 8.3 12 63.1 7.3 16 69. 8 5.5 20 55.9 8.2 24 41.8 4.8 28 34.3 10.7 32 31. 4 4.3 36 19. 3 9.3 40 -25. 8 18.3 44 -12.3 0.6 48 -25.4 3.9 52 -23.1 2.2 56 -53.3 19.7 92 'Table 4. Simulated carbohydrate import (mg CHzo day'l) of 'Montmorency' sour cherry fruits during devel0pment from full bloom to maturity. Stage I Stage II Stage III Day Import Day Import Day Import 1 1.00 23 6.00 36 14.77 2 1.11 24 4.92 37 17.83 3 1.33 25 4.10 38 21.22 4 1.71 26 3.55 39 24.82 5 2.34 27 3.28 40 28.42 6 3.29 28 3.29 41 31.69 7 4.62 29 3.60 42 34.13 B 6.34 30 4.20 43 35.14 9 A 8.40 31 5.10 44 34.25 10 10.62 32 6.32 45 31.34 11 12.78 33 7.88 46 26.84 12 14.61 34 9.80 47 21.56 13 15.90 35 12.09 48 16.41 14 16.54 49 12.05 15 16.54 50 8.77 16 15.97 51 6.54 17 14.94 52 5.16 18 13.59 53 4.36 19 12.02 54 3.94 20 10.39 55 3.74 21 8.78 56 3.65 22 7.30 57 3.61 93 by fruit photosynthesis, 19.4 and 29.7%, occurred during stages I and II, respectively, when the light intensity in the canopy is still high (7), this balance seems realistic. The importance of fruit photosynthesis for yield will depend on the changing CH20 supply and demand during the season. Our results suggest, in agreement with the findings of Koch and Alleweldt for grape (13), that fruit photosynthesis is highest and most important early in the season. At this time carbohydrate demand is high due to the first peak of fruit growth, which competes with early vegetative growth for CH20- At this time CH20 supply is limiting because of the small leaf area (5, 12). Fruit set is determined between bloom and 'June drop' (Stage I and 111- If the CH20 supply limits fruit persistence on the tree, which has been suggested, but never conclusively demonstrated (22, 7), then the photosynthetic contribution of the fruit should be important. Light intensity in the canopy is high at that time, for there is little shading by leaves. Fruit photosynthesis may be important to supplement leaf photosynthesis in the case of large fruit load (leaf to fruit ratio below 1.5) or defoliation. However, later in the season leaf photosynthesis becomes more important, light intensity and fruit photosynthetic capacity are low and fruit photosynthesis loses its importance. The decrease of DPN during fruit development could be caused by several factors. There is evidence that fruit photosynthesis is subject to feedback inhibition by leaf photosyntates (14). However, chlorophyll loss seems to be the main cause for the decrease in fruit photosynthesis 94 in sour cherry, as suggested for several other species (2, 3, 9). DPG compensation for 0R0 decreased steadily from full bloom to maturity (Table 3) due to decreasing fruit photosynthesis. Import maxima of 15.54 and 35.14 mg 0320 day-1 occurred 14-15 and 43 days after full bloom, respectively; If during the second maximum a leaf area of 35 to 50 cm2 fruit'1 is required for fruit growth, export to the fruit must be approximately 0.7 to 1.0 mg CH20 cm"2 day'l. A maximum rate of CHzo export of 1.5 to 2.5 mg or2 day'1 can be calculated from previously reported estimates (12), which is more than twice the rate required for fruit growth and leaves sufficient CH20 for vegetative growth. Dark respiration required 30.9%-of all CHzo used during fruit development. However, the share used by dark respiration changed throughout fruit development, being 32.7, 70.9 and 19.9% during stages I, II and III respectively. The levels of dark respiration were, according to the expected energy requirement for the different stages, high for lignin and lipid synthesis during pit hardening and embryo development (Stage II), intermediate during cell division (Stage I) and low during cell expansion with accumulation of sugars, sugar alcohols and organic acids. The present study demonstrates that fruits are not only sinks for CH20, but are capable of contributing significantly to yield by means of their photosynthetic activity. 95 LITERATURE CITED 1.Bazzaz, F. A., R. M. Carlson, and J. L. Harper. 1979. Contribution to reproductive effort by photosynthesis of flowers and fruits. Nature 279:554-555. 2.Bean, R. C., G. G. Porter, and B. K. Barr. 1963. Photosynthesis and respiration in developing fruits. III. Variations in photosynthetic capacities during color change in citrus. Plant Physiol. 38:285-290. 3.Clijsters, H. 1969. On the photosynthetic activity of developing apple fruits. Qualitas Plantarum et Materiae Vegetabilis 19:129-140. 4.Eisensmith, S. P. 1984. PLOTIT. Ein interaktives Graphikprogramm (Version 1.0). 5.Eisensmith, S. P., A. L. Jones, and J. A. Flore. 1980. Predicting leaf emergence of 'Montmorency' sour cherry from degree-day accumulations.iJ. Amer. Soc. Hort. Sci. 105:75-78. 6.Feucht , 9., M. Z. Khan and N. Gruppe. 1972. Die Rolle von wuchshormonen und des N-Stoffwechsels in der Reifephase von Kirschenfruechten. bartenoauwissenschaft 37:409-418. 7.Flore, J. A. 1981. Influence of light interception on cherry production and orchard design. Proc. Mich. State Hort. Soc. 111:161- 169. 8.Flore, J. A. and C. E. Sams. 1985. Does photosynthesis limit yield of sour cherry (M cerasus)? In: A. Lakso and F. Lenz (eds). Regulation of photosynthesis in fruit trees. N.Y. State Agr. Expt. Sta. Spec. Bull. (In press). 96 9.Frieden, K. H. 1984. Transpl‘ration und C02 von Trauben verschieaener Rebsorten. Dissertation, Universitaet Bonn. 10.Geisler, G., and F. Radler. 1963. Entwicklungs- und Reifevorgaenge an Trauben von fills. Ber. Deut. Bot. Ges. 76:112-119. 11.Hau, B. and S. P. Eisensmith. 1985. Growth curves of double sigmoid pattern. In preparation. 12.Kappes, E. M. and J. A. Flore. 1985. Estimation of net carbohydrate export from sour cherry (M cerasus L. 'Montmorency') leaves and shoots. In preparation. 13.Koch, R., and G. Alleweldt. 1978. Der Gaswechsel reifender Heinbeeren. Vitis 17:30-44. 14.Kurssanow, A. L. 1934. Die Photosynthese gruener Fruechte und ihre Abhaengigkeit von der normalen Taetigkeit der Blaetter. Planta 22:240-250. 15.Lakso, A. N. 1982. Precautions on the use of excised shoots for photosynthesis and water relations measurement of apple and grape leaves. HortScience 17:368-370. 16.Noga, G. and F. Lenz. 1982. Einfluss von verschiedenen Klimafaktoren auf den cog-Gaswechsel von Aepfeln waehrend der Licht- und Dunkelperiode. Gartenbauwissenschaft 47:193-197. 17.Pandey, R. M. and H. L. Farmahan. 1977. Changes in the rate of photosynthesis and respiration in leaves and berries of 113E115. vinifera grapevines at various stages of berry devel0pment. Viti S 16:106-111. 97 18.Sams, C. E. 1980. Factors affecting the leaf and shoot morphology and photosynthetic rate of sour cherry (Prunus cerasus L. 'Montmorency'). Ph.0. Thesis, Michigan State University, East Lansing. 19.Sams, C. E., and J. A. Flore. 1982. The influence of age, position, and environmental variables on net photosynthetic rate of sour cherry leaves. J. Amer. Soc. Hort. Sci. 107:339-344. 20.Sams, C. E. and J. A. Flore. 1983. Factors affecting net photosynthetic rate of sour cherry (Ms cerasus L. 'Montmorency') during the growing season. Photosynthetic Res. 4:307-316. 21.Sartorius, 0. 1926. Zur Entwicklung und Physiologie der Rebbluete. Angew. Bot. 8:29-89. 22.Tukey, H. B. 1934. Growth of the embryo,seed and pericarp of the sour _ cherry (Prunus cerasus) in relation to season of fruit ripening. Proc. Amer. Soc. Hort. Sci. 31:125-144. Section IV Photosynthesis and Respiration of Sour Cherry (Prunus cerasus L. 'Montmorency') Fruits during Development, as influenced by the Environment 98 99 ABSTRACT GFOSS photosynthesis (Pg), net photosynthesis (PN) and dark respiration RD rates of 'Montmorency' sour cherry fruits during development were investigated. PG was closely related to the chlorophyll content of the fruit and reached a maximum rate during stage II of fruit growth. RD rate per unit fruit volume also reacned its maximum during stage 11, indicating a high respiratory need for energy and biosynthesis. Light saturation was reached at 1000 pmoles m"2 5‘1. PG approacheo a maximum at 40°C. RD increased exponentially with temperature. As a result, PN reached its maximum at 18°C- PN rates increased with increasing C02, reaching saturation at 400 cm3 m-3, A postillumination C02 burst could not be detected. RD increased with increasing 02 levels and PN decreased as a result of increased RD. PG was not affected by the 02 concentration. The data suggest that sour cherry fruits do not have an apparent photorespiration. Abreviations: P5, gross photosynthesis; PN, net photosynthesis; RD, dark respiration; RL, photorespiration; g's, stomatal conductance to 002; ca. ambient C02 concentration; c1, internal 002 concentration; PPFD, photosynthetic photon flux density; VPD, vapor pressure deficit; LSD, least significant difference. 100 Photosynthesis by fruits of sour cherry (Kappes and Flore 1985a) and from other Species (Clijsters 1969 and 1975, Frieden 1984, Jones 1981, Noga and Lenz 1982a) contributes to the fruits' carbon balance. Kappes and Flore (1985a) demonstrated that the sour cherry fruit’s overall contribution to its carbon balance amounted to 11%, while the contribution during stages I and II (according to Tukey”s (1934) description of fruit development) was 47.3 and 29.5%, respectively (Kappes and Flore 1985aL R0 of sour cherry fruits has been reported (Pollack §t_al. 1961, Blanpied 1972). However, no reports are known concerning sour cherry fruit photosynthesis or how the fruitfls C02 gas exchange is affected by different environmental factors, or on the effect of 02 concentration on P", PG or RD in fruit tissues. The objective of this study was to investigate the influence of developmental stage and environmental factors on sour cherry fruit PG, PM: RD and RL, MATERIALS AND METHODS Unless otherwise stated all experiments were conducted with fruit on excised branches from 12-year-old sour cherry ('Montmorency' on Mahaleb rootstock) trees growing at the Horticulture Research Center in East Lansing, Michigan. Branches (50 cm in length) were excised around 07:00 h, the cut ends submerged in water, and transported to the laboratory, where the bases were recut under water. Four adjacent fruits were placed in each of 4 assimilation chambers, while remaining attached to the branch (see Sams and Flore 1982 for details concerning assimilation chamber design and environmental control). Gas exchange rates were expressed per fruit, per unit surface area or per unit fruit volume. 101 Fruit chlorophyll content was determined at 6-day intervals, using the method of Moran (1982). Chlorophyll was extracted from intact fruits using 10 to 600 mg fruit fresh weight cm‘3 N,N-dimethylformamide as chlorophyll concentration in fruits decreased from full bloom to maturity. Fruit surface area and volume were estimated from fruit diameters (Tukey 1934). PG was calculated from PN and RD, assuming that R0 was the same in the light as in the dark. This assumption is conventional and holds for tissues with high metabolic need for respiration, even though RD can be affected by light (Graham 1980). Seasonal changes in P3, p" and RD were determined by measurements at 4-day intervals from full bloom to maturity. Standard conditions, unless otherwise stated, were: temperature, 25°C, PPFD, 1000 or Olumol m'2 s‘1 for the light and dark treatment, respectively, and leaf to air VPD, approximately 2kPa. Fruit stomata were observed by scanning electron microscopy in the Michigan State University Center for Electron Optics. Fruit surface . sections (6 - 8 mm diameter) were fixed in buffered glutaraldehyde (5%, 1 h), rinsed in sodium phosphate buffer (0.1M, pH 1, 15 min) and dehydrated in a graded series of aqueous ethanol (25%, 50%, 75%, 95%, 100%, 15 min each). Samples were critical point dried, transferred to specimen stubs and coated with a film of evaporated gold. Samples were viewed at 15 kV, from a 90° angle to the surface, at 360-fold magnification. 102 The effects of PPFD 0n PM were determined during mid stage I, 9 days after full bloom. PPFD was reduced during the experiment from 2000 to 0 ‘pmol m'z 5'1. Fruits were kept in ambient air adjusted for a VPD of 2.3kPa. Temperature effects on P5, PM and RD were examined during mid to late stage I, 15 days after full bloom, and during early stage III, 41 days after full bloom. The fruit temperature was increased from 10 to 40°C in increments of 5°, while the VP0 increased from 0.3 to 6 kPa. At the beginning 0f stage 111. R0 was measured only at the highest and the lowest temperature and was found to be equal to PN- Fruit photosynthesis response to increasing ca was measured in late 3 stage I, 19 days after full bloom. RD was determined at 3 c3 of 50 cm m‘3, assuming that R0 was not affected by ca. The effect of 02 concentration on P5, PM and R0 of fruits (plants described above) was examined in late stage I (15 days after full bloom) and in early stage II (19 days after full bloom) and for young fully expanded 7th leaves on I-year-old sour cherry ('Montmorency' on Mahaleb) trees obtained from Hilltop Orchards and Nurseries, Hartford, Michigan, potted in spring in 9-liter containers. The air supplied to the chambers consisted of a mixture of N2, 02, C02 and water vapor to give a ca Of 350 cm3 m-3, a VPD of 2.3302 kPa for the fruits and 1.3102 for the leaves. Increasing (stage I fruits and leaves) and decreasing (stage II fruits) 02 concentrations between 1.5 and 70% used were measured using an oxygen analyzer (Madel 0260, Beckman Instruments, Inc., Irvine, CA). 103 14C02 uptake in the light and dark fruits and leaves of '3-year-old sour cherry trees ('Montmorency' on Mahaleb, in 15-liter containers) was determined by exposing the leaf or fruit to 14002 (185,000 Bq) as described previously (Kappes and Flore 19856). Plant material was sampled after 30 min exposure, immersed in liquid nitrogen and transported frozen to the laboratory. Samples were combusted using a Biological Oxidizer - 0x400 (R. J. Harvey Instrument Corporation, Hillsdale, New Jersey). The combustion products were trapped in Carbon- 14-Cocktail (R. J. Harvey Instrument Corporation, Hillsdale, NJ) and the radioactivity counted in a liquid scintillation counter (1211 Rackbeta, LKB-Hallac, Turku, Finland). Corrections were made for combustion, trapping and counting efficiency, and data were calculated as dpm. The occurrence of a post illumination C02 burst in sour cherry fruits was examined using smaller chambers (2.5 * 1.0 * 1.7 cm, L * H * H) to reduce the dead time to approximately 1 min. The infrared gas analyzer response was monitored using a strip chart recorder. Fruits were kept at light saturation, 25°C, 340 cm3 m'3 002 and 66% 02. RESULTS Seasonal changes: The total chlorophyll content per fruit increased during the first twenty days after full bloom (stage I), from 5 ug i’ruit‘l to a maximum of 30 ug fruit'l, then decreased to 0 (Figure 1a). 'Fotal chlorophyll per unit surface area (Figure 1a) and per unit fresh weight (data not shown) decreased continuously starting from 130 mg m"2 and 200 mg kg"1 fresh weight at full bloom to 0 at maturity. Fruit 104 surface and volume increased following a double sigmoid curve (Figure 1b), as first described by Tukey (1934). The chlorophyll a/b ratio during stage I was 3.22:0.82. PG per fruit followed a pattern similar to that of total chlorophyll, increasing during stage I and then decreasing (Figure 2a). PG per unit fruit surface area increased slightly during stage I and then decreased (Figure 26). RD per fruit remained constant during fruit development, with the exception of a marked increase during stage II (Figure 2a). RD per unit fruit volume decreased during fruit development, with the exception of a transient rise during stage II (Figure 2c). Stomata remained intact throughout fruit development (Figure 3), whether they remained functional cannot be judged from the visual appearance. Stomatal conductance to C02 decreased during the course of fruit devel0pment. g'S was lower in the dark than in the light (Figure 4). PPFD: During stage I of fruit development PN increased with 1 increasing PPFD until saturation at approximately 1000‘pmoles m'2 s’ (Figure 5). At light saturation PG did not compensate for R0- Temperature; PN during stage I followed a curve with a maximum at approximately 18°C (Figure 6a, Equation 1), which is the sum of an exponential saturation curve for PG (Figure 6a, Equation 2) and an exponential curve for R0 (Figure 6a, Equation 3). At the beginning of stage III PN was equal to RD, and PG was 0. Dark respiration followed an exponential curve (Figure 6b, Equation 4). 105 Figure 1. A. Total chlorophyll per fruit (open circles) and per unit fruit surface area (closed circles) during 'Montmorency' sour cherry fruit development. 8. Surface area (open circles) and volume (closed circles) of 'Montmorency' sour cherry fruit during development. Vertical bars indicate standard error of the mean. 106 SE. 0:83.021... Ase 31v 3:: 525. A33 5 0. s 0. 42.. —150.0 #1210 -100.0 ~75.0 ~50.0 ~25.0 ~05 L 0 ._._.H. II T 50 Figure 1 a 1. , sax». an 1H ‘ 2 0 - q q n O 8 6 4 1 35- 1 A123: as jerzoomodzo .59 rev .2 x 6% 8:sz :2: TIME AFTER FULL BLOOM (days) 107 Figure 2. Fruit gross photosynthesis (P )(open circles) and dark respiration (RD) rates (closed circles) per gruit (A), per unit surface area (B) and per unit volume (C) of 'Montmorency' sour cherry fruit during development. Vertical bars indicate standard errors of the mean. 108 Figure 2 .n -m A 1 I 1 .n .w 1.» .w a .w i f f a. I” r” +1.. to 1 .1 to 1.0 i- , l -1... -, .o .aaa........li. , . d L- 1...: A.-. 5:2: .8 as W 1‘ A.-. TE .8 “mugs—Q: wmozc 203%”! 832 1 m '5 ‘ d 11 ‘ ‘i Mu 4 a a A.-. :5 .8 as out man FULL BLOOM (days) 107 Figure 2. Fruit gross photosynthesis )(Open circles) and dark respiration (RD ) rates (closed circles) per (Ptruit (A), per unit surface area (B) andD per unit volume (C) of 'Montmorency' sour cherry fruit during development. Vertical bars indicate standard errors of the mean. 108 Figure 2 -m -m A 1 I 1 0 .w 4» 1 1 r” .w 1 1 .0 -w 1 1 f a 1 1 5 .m 1 . rm rm 1 . i 1.0 1.0 i i l 4 11m . . . . 4 4 1m .IiJll m a o a m {m m w e m m m. w m .- . ... d . . . i .- A.-. is... .3 as A.-. TE .8 §§U¢ g 2 mm mO—OIQ mmozo 11.1.1315... A.-. a... .8 as flMEAFERlflnLIlDOM(dmn) 109 Figure 3. Scanning electron micrograph of fruit surface Of 'Montmorency' sour cherry during stages I (a), II (b) and III (c) of fruit development illustrating size and shape of stomata. 110 Figure 3. 170 Literature Cited 1.Lenz, F. 1979. Sink-source relationships in fruit trees. Pp. 141-153. In: T. K. Scott (ed.). Plant regulation and world agriculture. Plenum Press, New York. 2.Neales, T. F. and L. D. Incoll. 1968. The control Of leaf photosynthesis rate by the level of assimilate concentration in the leaf: A review Of the hypothesis. Bot. Rev. 34:107-125. 3.Sams, C. E. and J. E. Flore. 1982. The influence of age, position and environmental variables on net photosynthetic rate of sour cherry leaves. J. Amer. Soc. Hort. Sci. 107:339-344. 169 Figure 1. 40- rm 1 T v) m r“ C ( o . m . .Hn An 0 114 mm .- IL red 1 A I. d u i- d 0 O O O O 3 2 11 AL; sec N8 95 mamxezmosxo Dz 168 Figure 1. Comparison of rates of net photosynthesis of the tenth leaf of defoliated (closed circles, broken lines) and control (open circles, solid lines) 'Montmorency' sour cherry during development, Observations and regression lines. 167 Table 1. Rate Of net ppotosynthesis (P )(mg C02 0m"2 h'l) and stomatal conductance (g' S)( cm s ) of the tenth ieaf (just fully expanded). At the beginning ofS the 10th leaf' s expansion proximal leaves were removed, as compared to the non- -defoliated control. Measurements were taken Outside with a portable photosynthesis unit. PN 9's Treatment 10:00 hr 15:00 hr Mean 10:00 hr 15:00 hr Mean Control 17.5 5.4 11.5 0.129 '0.077 0.103 Defoliated 16.7 12.3 14.5 0.103 0.118 0.111 Mean 17.1 8.8 13.0 0.116 0.098 0.107 LSD (5%) Treatment PN g's Time 4.95 0.0602 Defoliation 4.95 0.0602 Time*DefOl. 7.00 0.0850 166 at 10:00 and 15:00 hr, respectively, full sunlight, ambient €02 concentration, 363:2 cm3m‘3, and vapor pressure deficit, 1.9:0.1 and 3.0:0.2 kPa at 10:00 and 15:00 hr, respectively. Net photosynthesis rates of partially defoliated and control plants, measured in the laboratory, increased at a similar rate during leaf expansion (Figure 1). A t-test did not reveal significant differences in slopes Of the regression lines. Net photosynthesis rates Of fully expanded leaves, measured outside, showed statistical differences at the level of interaction between defoliation treatment and time of the day (Table 1). Net phOtosynthesis rate decreased significantly during the day in leaves of control plants, but not in leaves of partially defoliated plants. The decrease in PN was parallel to a small, but statistically nonsignificant, decrease‘ in stomatal conductance to 002 (g's). ‘ The results indicate that leaves from defoliated and control plants were not intrinsically different with respect to their photosynthetic capacity; however, control plants were subject to feedback inhibition in contrast to the partially defoliated plants. Short term PN measurements in the laboratory show intrinsic maximum rates only, not affected by feedback inhibition. It can be assumed that feedback inhibition can only be Observed after the whole plant has been carrying on photosynthesis for an extended period of time. Under laboratory conditions, working with single leaf assimilation chambers, where the rest of the plant is under low light conditions, the single leaf will usually have maximum PN for the given environment. 165 Sink-source relationships affect net photosynthetic rates (PN) of fruit trees (Lenz, 1979) and other plants (Neales and Incoll, 1968). The objective of this study was to determine intrinsic differences between and effects of feedback inhibition on PN in partially defoliated and intact plants. Plant material: One-year-Old sour cherry trees ('Montmorency' on Mahaleb) (Hilltop Orchards and Nurseries, Hartford, M1) were potted in 7.5 liter containers, using a mixture of peat, sand and field loam (3:2:5,v:v:v) and pruned to a single bud. During the study 1 single shoot was permitted to develop. Trees were grown outside at the Horticulture Research Center, East Lansing, MI. Hater, fertilizer (20% N, 20% P, 20% K) and pesticides (Captan, Guthion, Kelthane) were used as necessary. Trees were placed in a random design, and at the beginning of emergence of the ‘1Uth leaf from the base, half of the trees was defoliated below the 10th leaf. Photosynthesis of the 10th leaf of defoliated and control plants was measured. Photosynthesis measurements: Photosynthesis of the 10th leaf was measured during leaf development, as described by Sams and Flore (1982). Conditions were: temperature, 24.911.00C, photosynthetic photon flux density, 1000 pmol m'zs‘l, ambient C02 concentration, 328114 cm3m‘3, and vapor pressure deficit, 1.6:O.5 kPa. Photosynthesis was measured in the field using a portable chamber and gas analyzer (Analytical Development Co. Ltd., Hoddesdon, England) at 10:00 and 15:00 hr. Conditons were: temperature, 21.310.50C and 29.0100C Appendix 0 Comparison Of Photosynthesis Measurements under Field and Laboratory Conditions 164 NIIISIS ) SS PHOTO? DICIED . 1‘ cup do 39m ( DNLYGR non PREDICTESVA (mg CH.O day“) DAILY {MRK RE ') I PHOTIOSJrTKSIS (210.0 day- NEPREDIC E "‘9 DMY ( 163 Figure 2. 701 ‘A 004 5a. ‘ e do. 6 o 4 O 0 so. ‘ O O 20‘ 03 104 inflate-35.337: use-ates. zeal-*5. DNLYN PHOTOSYNTHESIS outvcaqggpworosmmese i635 ) (mo CH,o day“) (no Ciao our“) 3°! - (C a H ° 0 O o . A 1 . . E 0- ° 0 g - g o. 5 a. m . 8g? 1 5 V 1 24 > . g 1.. c ah I f r I c T I r r v I . 1 r j 0 2 ‘ 6 3 I: O Mimimmmmmmm DAILY DARK RESPIRAT'ION ONLY GROSS PHOTO [SIS O SERVED) (OBSERVED (mg ch,o day“) (mg 014,0 day") 3' § ,, ION I KRE 333?; 5 § § nifi our 8 ‘0 ”'3. i6} 200 :66 400 T960 060 700 DAILY dank RESPIRATION '(CBSER‘ (mg 614,0 day“) 4') 0-1 I soon 1650 2066' DAILY m? PHOTOSYNTi-IESIS OBSERVED) (m9 Ciao dor‘) 162 Figure 2. Comparison of predicted and experimental data for: A.Uaily net photosynthesis of the terminal leaf E.Daily gross photosynthesis of the terminal leaf C.Daily dark respiration of the terminal leaf D.Daily net photosynthesis of the Wh01€ shoot E.Daily gross photosynthesis of the whole shoot F.Daily dark respiration of the whole shoot 161 Figure 1. °°°1 . 1A 9 3 ”a? qp u x " 03.3%: '2 g “at . W 88 o 333% 23:83 —. ‘ o 5" $8 3N4 0‘50 0 g E? J 3 . v _ Ely m1 9 v i a C.) 100.4 c * l r r 1 o . A 1 . O ‘00 2% 300 400 500 600 O 5 10 75 CARBOHYDRATE CONTENT CARBOHYD TE CO x 10" (ESSERVED) {‘85 E m9 Clip) m9 CH9 230. g ‘c . ! mu 0 ° 2: « ° ° ~12!le $3.;- 4 mg 100- WO- av? =3 a a: l 2 ”i 3 J co :3 We l; 230 230 5 150 150 zoo {3 l“ 8 "ON ‘6 8 _... 4L.4.-L__5_.l W ARK RESP PRC! MC] E D 83 (.39 cup day") 5 A ONIY O u DAILY oaoss pworommeszs (cassava?) (mo CH9 day“) 2'0 7: DAILY omen nesemnon cassava? 23 23 mohozn_ .52 115 Figure 6. A. Mathematical functions for the effect of temperature on gross photosynthesis (Pg) (top line), net photosynthesis (PN) (center ine) and dark l‘e'-il3l'l"d’£l0ll»(RD) (bottom line) in stage I. 8. Observed values for net photosynthesis (PM) (open symools) and dark respiration (Pg) (closed symbols) in stage III of 'Montmorency' sour cherry fruits, as affected by temperature. Different symbols on the graph represent different replications, and each replication is the average of 4 fruits. 114 9...... N...c.. _oE >._..mzmo x34... ZOHOIQ o. Ihz>mOHOIQ ijw Figure 5. com. OO¢F 000. can com cowl L P L — p F p b n — n can! 6 . 100*! m . o 6 icon! 8.... o onumoo 8 88.. o D T O 0 W . d 4 4 loop! a o a . (,..s z-“J 67’) SiSEHlNASOiOHd 1.3N 113 Figure 5. Effect of photosynthetic photon flux density (PPDF) on net hotosynthesis rate (PN ) of 'Montmorency' sour cherry fruits during Stage . Different Nsymbols on the graph represent different replications, and each replication is the average of 4 fruits. 112 Figure 4. r ' r I\ CO if) 81" F) N v- ‘ (,-s 015) _ z-OL X BONVJQOGNOO 1V1VWO1S TIME AFTER FULL BLOOM (days) 111 Figure 4. Fruit stomatal conductance to C02 (9‘ ) in the light (open circles) and in the dark (closed circles) of 'Mon morency' sour cherry fruit during develOpment. Vertical bars indicate standard errors of the mean 0