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Matthew D. Whiting and David Ophardt

The development of novel crop load management techniques will be critical to the adoption and success of high density sweet cherry orchard systems based on new clonal rootstocks. Herein we report on a comparison of potential means of balancing crop load of `Bing' sweet cherry grown on the productive and precocious rootstocks `Gisela 5' and `Gisela 6'. In 2002, thinning treatments were applied to entire trees and consisted of an unthinned control (C), and manual removal of 50% of the blossoms (B) or 50% of 2-year-old and older fruiting spurs (S), throughout the tree. In 2003 all trees were left unthinned to characterize the carry-over effect of thinning treatment in 2002. In 2002, compared to C, thinned trees had 38% to 49% fewer fruit per tree, 22% to 42% lower yield, 8% to 26% higher fruit weight, and 2% to 10% larger fruit diameter. S and B treatments reduced yield by 42% and 22% on `Gisela 5' and by 40% and 31% on `Gisela 6', respectively. `Gisela 5'-rooted trees showed greater improvements in fruit quality than did trees on `Gisela 6'. Compared to C-, S-, and B-treated trees on `Gisela 5' yielded fruit that was 15% and 26% heavier, respectively. Yield of fruit ≥25.5 mm diameter was increased by 240% by S and 880% by B, though yield of this size fruit was still low (1.5 and 5.2 kg/tree, respectively). Neither technique had any beneficial carryover effect in the year following treatment despite S trees bearing about 25% fewer fruit than B and C trees. In both years, `Gisela 5'-rooted trees bore about 15% fewer fruit than trees on `Gisela 6'. Compared to `Gisela 5', `Gisela 6'-rooted trees were about 41%, 46%, and 24% more productive for C, S, and B, respectively. Number of fruit/tree in 2003 was within 4% and 8% of the previous year on `Gisela 6' and `Gisela 5', respectively. Crop value analyses suggest growers would be rewarded for producing high yields of medium size fruit (e.g., 21.5 to 25.4 mm) compared to low yields of high quality fruit.

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Olivia M. Lenahan, Matthew D. Whiting, and Donald C. Elfving

This paper reports on the potential of gibberellic acid (GA3 and GA4+7) to reduce sweet cherry (Prunus avium L.) floral bud induction and balance fruit number and improve fruit quality in the season following application. In 2003, GA3 was applied to `Bing'/`Gisela 1' trees at 50 and 100 mg·L-1 at the end of stage I of fruit development, end of stage II, and on both dates. These treatments were compared to the industry standard application of 30 mg·L–1 applied at the end of stage II and an untreated control. Fruit quality was evaluated in the year of application (i.e., nontarget crop) and return bloom, fruit yield and quality were assessed in the subsequent season (2004). In 2003, GA3 delayed fruit maturity proportional to rate. In 2004, bloom density and fruit yield were related negatively and linearly to GA3 concentration. GA3 reduced the number of reproductive buds per spur and did not affect the number of flowers per reproductive bud. Nonspur flowering at the base of 1-year-old shoots was more inhibited by GA3 than flowering on spurs. Double applications significantly reduced bloom density and yield versus single applications. Trees treated with two applications of 50 and 100 mg·L–1 yielded fruit with 7% and 12% higher soluble solids, 15% and 20% higher firmness, and 7% and 14% greater weight, respectively. However, no treatment improved crop value per tree. In a separate isomer trial, GA3 and GA4+7 were applied to `Bing'/`Gisela 1' trees at 100 and 200 mg·L–1 at both the end of stage I and II in 2004. GA3 and GA4+7 applied at 100 mg·L–1 reduced bloom density similarly by 65%. GA3was more inhibiting than GA4+7at 200 mg·L–1, reducing bloom density by 92% versus 68%. We observed a 4- to 5-day delay in flowering from both GA formulations at 200 mg·L–1. At both concentrations, GA3 reduced yield by 71% and 95% versus 34% and 37% reduction by GA4+7. Fruit weight and soluble solids were unaffected but fruit firmness was increased by all treatments (6% to 17%). However, crop value per tree was highest from untreated control because improvements in fruit quality were insufficient to offset reductions in yield. GA3 shows potential as a novel crop load management tool in productive `Bing' sweet cherry orchard systems.

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Thomas E. Marler and Christopher A. Shaw

plants were tagged and dated to record emergence of reproductive events during early 2003. Trees that bore 22-month-old mature seeds in Feb. 2005 were used to study source-sink relations. Study 1: Somatic tissue size and mega-gametophyte sterols. Seeds

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James W. Olmstead, Amy F. Iezzoni, and Matthew D. Whiting

, fruit size can also vary several fold as a result of variations in canopy source–sink relations ( Lang and Ophardt, 2000 ; Whiting and Lang, 2004 ). Between-cultivar differences in fruit flesh cell number and cell size related to overall fruit size

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Wenjing Guan, Xin Zhao, and Donald J. Huber

ripeness before harvest for the grafted watermelon plants. The delayed ripening observed in grafted watermelons might be linked to increased fruit load burdening source–sink relations rather than delayed flowering ( Soteriou et al., 2014 ). Fig. 1

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Zhen Shu, Yimin Shi, Hongmei Qian, Yiwei Tao, and Dongqin Tang

Freesia flower senescence. Carbohydrates are primary energy source in plants ( Gibson, 2004 ); some are consumed as respiratory substrates and some others are converted to other compounds. Changing source–sink relations are a common event during plant

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Chris A. Martin, Sean A. Whitcomb, and Jean C. Stutz

through changes in carbon source sink relations and subsequent patterns of allocation ( Yuan et al., 2009 ). The authors are aware of no published studies on rates of landscape shrub leaf maturation and senescence, photosynthetic efficiency, and carbon

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Thomas E. Marler

formation on large stem cuttings. The direct relationship between carbohydrate status at the time of stem excision and propagation success rates indicates that the inclusion of a plant physiologist with knowledge of source–sink relations may be a

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Sachiko Kawamura, Kyoko Ida, Masako Osawa, and Takashi Ikeda

.J. 1995 Levels of apoplastic solutes in developing strawberry fruit J. Expt. Bot. 46 743 752 Roitsch, T. Ehneß, R. 2000 Regulation of source/sink relations by cytokinins Plant Growth Regulat. 32 359 367 Sugiyama, K. Morishita, M. 2000 Fruit and seed