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Yue Wen, Shu-chai Su, Ting-ting Jia, and Xiang-nan Wang

examined. During this study, we conducted 13 C-labeling experiments involving C. oleifera to study the dynamics of allocation of assimilates from different source leaves to buds and fruits during different fruit growth periods and the role of leaves in

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Craig S. Charron, Steven J. Britz, Roman M. Mirecki, Dawn J. Harrison, Beverly A. Clevidence, and Janet A. Novotny

C-enriched foliar respiration was detected, leaf incorporation of 13 C was not significantly different from control trees. Successful atmospheric labeling with 13 CO 2 poses a number of challenges. Uniform labeling is highly advantageous because

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Marlene Ayala and Gregory Lang

(grams)] and DW (grams), diameter (millimeters), and soluble solids content [SSC (percent)]. Thirty FS, NFS, and ES were measured for FW, DW, leaf number, and LA. Treatments (T) and 13 C labeling. From the 600-branch population previously characterized

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Xiaohua Yang, Susan K. Brown, and Peter J. Davies

in volts. Peaks are labeled with retention time and the gibberellins identified by gas chromatography-mass spectroscopy. Fifty percent of the [ 14 C]GA 12 feeding material (peak A, GA 12 ) was metabolized quickly into peak B (GA 15 ) at 30 min ( Figs

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Robert E. Rouse, Monica Ozores-Hampton, Fritz M. Roka, and Pamela Roberts

block of 16 year-old ‘Valencia’ orange ( Citrus sinensis Macf.) trees on Swingle citrumelo rootstock [ C. paradisi × Poncirus trifoliata (L.) Raf.]. The experimental design was a split-plot with pruned and nonpruned as the main plots and four

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Marius Huysamer, L. Carl Greve, and John M. Labavitch

Discs from outer pericarp of mature green (MG) and light red (LR) tomatoes were incubated with 13C6-glucose as precursor to cell wall constituents, to determine biosynthetic capacity of the outer 2mm (including cuticle) and adjacent inner 2mm of tissue. Cell wall material was fractionated into pectic and hemicellulosic classes by sequential extraction, and alditol acetates and partially-methylated alditol acetates were prepared. Neutral sugars (NS), glycosidic linkage compositions and incorporation of label were determined by GC-FID and GC-MS. Rhamnose, arabinose and galactose accounted for ca. 90% of both labeled and total NS in the pectic fractions (sugar ratios within ripeness stage were the same for labeled and total NS). Xylose and glucose accounted for ca. 70% of both labeled and total NS in the hemicellulosic fraction (sugar ratios within ripeness stage were different between labeled and total NS). In the crude cell wall, galactose and glucose contents were significantly higher in the inner than in outer tissues for both MG and LR tomatoes. Loss of galactose during ripening was higher from outer tissues. These results show compositional differences between inner and outer tissues, and suggest that ripening-related wall synthesis may give rise to pectic polymers similar in NS composition to existing polysaccharides, and hemicellulosic polymers which may differ in composition.

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Caixi Zhang, Kenji Tanabe, Fumio Tamura, Akihiro Itai, and Shiping Wang

The aim of this study was to investigate the roles of spur characteristics and carbon partitioning in regulating cultivar differences in fruit size of two late-maturing japanese pear cultivars, `Atago' and `Shinkou'. The study of spur characteristics showed that the two cultivars displayed different patterns in leaf development, flower characteristics, fruit growth, and shoot type. In contrast to `Atago' with dramatically larger fruit, `Shinkou' is a heavily spurred cultivar with a higher total leaf area and leaf number per spur early in fruit growth, less vegetative shoots, and smaller fruit but larger core. No significant differences were obtained in specific leaf weight, leaf thickness, chlorophyll content, and net photosynthesis of mature leaves, and seed number per fruit between the two cultivars. The results of trace experiment with 13C revealed that on a spur basis, there were no significant differences in the amount of 13C assimilate produced by spur leaves on each labeling date except at 190 days after anthesis, however, there were highly significant differences in the amount of 13C allocated to fruit between cultivars. Moreover, a higher amount of 13C assimilates was allocated to `Atago' flesh (or fruit) than that in `Shinkou'. Analysis of relative sink strength (RSS) indicates that the sink strength of fruit was dominant over those of other organs in the spur measured in both cultivars except at the early stage of fruit growth. `Atago' exhibited a greater RSS of fruit and lower losses of 13C for respiration and export than `Shinkou'. These results suggest that the movement of photosynthates into the fruit was determined by sink strength of the fruit rather than the source strength in the two cultivars.

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B.E. Maust and J.G. Williamson

Experiments were conducted with `Hamlin' orange [Citrus sinensis (L.) Osb.] budded on Cleopatra mandarin (Citrus reticulata Blanco) or Carrizo citrange [Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.] seedling rootstocks to determine minimum container solution N concentrations required for optimum growth and fertilizer uptake efficiency at various growth stages. Plants were fertigated daily with 1 liter of N solution at either 0, 12.5, 25, 50, 100, or 200 mg·liter-1 from NH4NO3 or 0, 3.13, 6.25, 12.5, 25, or 50 mg·liter-1 from NH4NO3 dissolved in a complete nutrient solution, respectively. Percentage of N in the mature plant tissues increased as N concentration in the medium solution increased. Shoot length and leaf area increased as N concentrations increased up to a critical concentration of 15 to 19 mg·liter-1. The critical N concentration for root, shoot, and total plant dry weight was ≈18 mg·liter-1 for `Hamlin'-Cleopatra mandarin nursery plants and 15 mg·liter-1 for `Hamlin'-Carrizo nursery plants. The critical N concentration for relative total plant dry weight accumulation (percentage) for the two experiments was 16.8 mg·liter-1. In a separate experiment, plants were given labeled fertilizer N (FN) (15NH4 15NO3) at one of five growth stages: A) in the middle of rapid shoot extension of the third flush, B) immediately following the cessation of the third flush shoot extension but during leaf expansion, C) immediately following leaf expansion, D) before the fourth flush, or E) in the middle of rapid shoot extension of the fourth flush. Labeled FN recovery increased during rapid shoot extension of the fourth scion flush compared to the other labeling periods. FN uptake per gram of total plant dry weight was greatest during rapid shoot extension (A and E) and lowest during the intermediate labeling periods (B-D). FN supplied 21% to 22% of the N required for new growth during rapid shoot extension.

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Hiroshi Yakushiji, Kunihisa Morinaga, and Hiroshi Nonami

for 13 C determination of plant tissues. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.

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Warren E. Copes and Eugene K. Blythe

maximum acceptable level) at 13 min 54 s submersion in 55 °C water ( Fig. 1 ). In Expt. 6, Rhizoctonia was eliminated from stem pieces with increasing water temperature when stem pieces were submerged for 30 s and 60 s ( Fig. 2 ). Significant factors