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Alison L. Reeve, Patricia A. Skinkis, Amanda J. Vance, Katherine R. McLaughlin, Elizabeth Tomasino, Jungmin Lee, and Julie M. Tarara

estimate wine quality. Given the relationships between tissue N and vine growth measures, N was likely a physiological driver of source–sink relationships affecting berry composition. Total soluble solids were best explained by crop load, whereas other

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Guohai Xia, Lailiang Cheng, Alan Lakso, and Martin Goffinet

exemplifies the central role of the source-sink relationship in determining apple fruit growth, which also provides a very useful framework for understanding the effect of many other factors on apple fruit growth and final fruit size. Increasing nitrogen (N

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Arthur A. Schaffer, Marina Petreikov, Daphne Miron, Miriam Fogelman, Moshe Spiegelman, Zecharia Bnei-Moshe, Shmuel Shen, David Granot, Rivka Hadas, Nir Dai, Moshe Bar, Michael Friedman, Meir Pilowsky, Nehama Gilboa, and Leah Chen

The carbohydrate economy of developing tomato fruit is determined by wholeplant source–sink relationships. However, the fate of the imported photoassimilate partitioned to the fruit sink is controlled by the carbohydrate metabolism of the fruit tissue. Within the Lycopersicon spp. there exists a broad range of genetic variability for fruit carbohydrate metabolism, such as sucrose accumulation and modified ratios of fructose to glucose in the mature fruit and increased starch synthesis in the immature fruit. Metabolic pathways of carbohydrate metabolism in tomatoes, as well as natural genetic variation in the metabolic pathways, will be described. The impact of sink carbohydrate metabolism on fruit non-structural carbohydrate economy will be discussed.

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Jean-Pierre Privé, J.A. Sullivan, and J.T.A. Proctor

Leaf removal, cane girdling, and 14C translocation patterns were used to study source-sink relationships of primocane-fruiting (PF) red raspberries. Although the leaves in the reproductive zone were most important for vegetative and reproductive development, compensatory effects between the cane leaves were evident. When 14C translocation was studied in the reproductive portion of the cane, the lateral closest to the 14C-treated leaf was the major sink for carbohydrate from that leaf, independent of leaf position or reproductive development. Thereafter, partitioning to leaves and/or flowers or fruits above the 14C-treated leaf was related to leaf phyllotaxy 75% of the time.

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Ted M. DeJong

Previous research using relative growth rate models indicates that under normal cropping conditions peach fruit growth and yield is alternately source and sink limited during different phases of fruit growth. An experiment was designed to test this concept on whole trees in the field. Shortly after bloom central leader trees of `Spring Lady' and `Cal Red' peaches, were thinned to various crop loads ranging from -50 to -400 fruit per tree. At specific intervals trees representing the full range of crop loads were harvested to determine mean individual fruit weight/total crop weight relationships for whole trees. Then, assuming that fruit on low cropped trees grew at their maximum potential growth rate (sink demand) and that total crop growth on unthinned trees represented the maximum dry matter available for fruit growth (source supply), the relative source and sink limitation between each harvest interval was calculated. With `Cal Red', fruit growth appeared to be primarily source limited early and late in the season but primarily sink limited during the mid-period (Stage II) of fruit growth. At normal commercial crop loads, `Spring Lady' was less source limited than `Cal Red'.

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David P. Miller, G. Stanley Howell, and James A. Flore

The measurement of whole-plant CO2 uptake integrates leaf-to-leaf variability, which arises from such sources as angle of incident radiation, source/sink relationships, age, and biotic or abiotic factors. Respiration of above-ground vegetative and reproductive sinks is also integrated into the final determination of whole-plant CO2 assimilation. While estimates of whole-plant CO2 uptake based on single-leaf determinations have been used, they do not accurately reflect actual whole-plant assimilation. Chambers were constructed to measure gas exchange of entire potted grapevines. The design and construction are simple, inexpensive, and easy to use, allowing for the measurement of many plants in a relatively short time. This enables the researcher to make replicated comparisons of the whole-plant CO2 assimilation of various treatments throughout the growing season. While CO2 measurement was the focus of this project, it is also possible to measure whole-plant transpiration with this system.

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John W. Kelly, George L. Staby, and Grady W. Chism


When silver thiosulfate (STS), an antiethylene agent, was used prior to a preservative holding solution for carnations (Dianthus caryophyllus L.), there was no benefit in using the cytokinin benzyladenine (BA). If no STS or preservative was used, BA extended longevity. Most of the BA applied to the cut carnation remained localized in stem tissue. Stem, petal, gynoecium, and leaf tissue all metabolized BA. The applied BA levels increased in the gynoecium during carnation senescence, but STS prevented this increase. It is likely that STS altered the source:sink relationship between petals and gynoecium, since movement of cytokinin into the gynoecium corresponded to increased gynoecium fresh weight.

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Sang Gyu Lee* and Chiwon W. Lee

The relationship between source leaf position and the photo-assimilate translocation and distribution was characterized for tomato (Lycopersicon esculentum Mill.) grown in the greenhouse. Three different positions of source leaf on the stem (first node above or below the first fruit cluster and fifth node above the first fruit cluster) were tested for their influence on 14CO2 assimilation and transfer to different parts of the plant. The leaves at the fifth node above the first fruit cluster transferred the highest (57%) proportion of C14 to other plant parts, followed by leaves borne on the first node below the first fruit cluster (50%), and the first node above the first fruit cluster (39%). In all treatments, fruits served as the strongest sink for C14, followed by stem, leaf, and root tissues. The leaf borne on the fifth node above the first fruit cluster transferred the largest amount of C14 to the second fruit cluster.

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Robyn McConchie and N. Suzanne Lang

Protea neriifolia R. Br., P. susannae E.P. Phillips × compacta R. Br., and P. eximia (Salis. ex Knight) Fourcade cut flower stems were examined to determine the relationship between postharvest leaf blackening rate and preharvest carbohydrate status. Postharvest leaf blackening was highest (83% by day 4) in P. eximia floral stems, which had the lowest preharvest sucrose concentrations. In contrast, P. susannae × compacta had <5% leaf blackening by day 4 and the highest preharvest leaf sucrose concentrations. Starch concentrations were highest in P. neriifolia; however, leaf blackening was intermediate between P. susannae × compacta and P. eximia and reached 52% at day 4. Preharvest carbon-exchange rate and stomatal conductance in all three species were extremely low, despite high photosynthetically active radiation and apparent lack of water stress. Comparing preharvest carbohydrate profiles in vegetative and floral stems suggests that vegetative stems may have a sink-to-source transition zone between the second and third divisions, while most leaves on floral stems may have transferred carbohydates to source leaves at harvest. While preharvest floral stem sucrose concentrations can be linked to leaf blackening rate, the high starch reserves in P. neriifolia reduced leaf blackening little in this species. We conclude that leaf blackening may be related more to inflorescence sink demand after harvest and oxidative substrate availability than preharvest reserve carbohydrate concentrations in each species.

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Gina E. Fernandez and Marvin P. Pritts

The objective of this experiment was to determine the effects that altering the probable source-sink relationships would have on subsequent growth and yield components under field conditions. The balance between vegetative and reproductive growth was altered by imposing light stress (shading) on various growth phases, or removing primocanes, floricanes or fruit. Removal of primocanes significantly increased yield the year of removal. However, if primocane removal coincided with canopy shading, this increase in yield was not achieved. Overall, a significant negative correlation existed between 1991 and 1992 yields. Treatments with high yields in 1991 had low yields in 1992, and visa verca. This evidence-suggests that: 1) primocanes and floricanes are competing for light, not photosynthates during the flowering and fruiting period and 2) altering the balance of vegetative and reproductive growth one year had a significant effect on growth the subsequent year.