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J.H. Keithly, H. Kobayashi, H. Yokoyama, and H.W. Gausman

Application of DCPTA as a pregermination seed treatment (DCPTA plants) increased the seedling vigor, relative growth rate, harvestable yield, and yield quality of processing tomato (Lycopersicon esculentum Mill. cvs. UC82, VF6203, H100). When compared with controls, the growth rates of roots and shoots of 30 μm DCPTA plants were increased significantly (P = 0.05) during seed germination and midexponential growth. At fruit harvest, greenhouse-grown 30 μm DCPTA plants showed a 2- to 3-fold increase in leaf, stem, and root dry weight compared with that of controls. Improvements in the uniformity of fruit maturation significantly increased the harvestable fruit yields of greenhouse-grown DCPTA plants compared with that of controls. The total soluble solids (oBrix), glucose, fructose, and carotenoid contents of red-ripe fruits harvested from greenhouse- and field-grown DCPTA plants were significantly increased compared with controls. Chemical name used: 2-(3,4-dichlorophenoxy)triethylamine (DCPTA).

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Gene E. Lester

Plasma membrane (PM) from hypodermal-mesocarp tissues of muskmelon fruits (Cucumis melo L. var. reticulatus Naud.) were compared to the electrolyte leakage changes of the same tissue during maturation and storage at 4 or 24C. During fruit maturity and storage, leakage of the hypodermal-mesocarp tissue increased, which is coincident with increased total sterol: total phospholipid ratios and increased phospholipid fatty acid saturation index of the PM. ATPase activity, a marker for the PM, indicated that the PM increased in buoyant density from 1.13 g.cm-3 to 1.14 g.cm-3 during maturity and ATPase activity peaked with fruit maturation. ATPase activity decreased with 10 days postharvest storage and was less at 24C vs. 4C, which was coincident with increased hypodermal-mesocarp electrolyte leakage. Biochemical changes within the sterol and phospholipid matrix of the PM are suggested to contain the processes capable of altering fruit membrane permeability and subsequent muskmelon fruit storage life.

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Thomas J. Zabadal and Thomas W. Dittmer

Sunlight-exposed clusters of Vitis vinifera L. cv. Chardonnay at twelve positions on a N-S oriented, single curtain trellis were monitored for temperature to determine their patterns of heat summation and diurnal temperature.

Diurnal patterns of temperature differed greatly among these clusters. These differences reflected the solar insolation on individual clusters. Point-in-time measurements among clusters during mid-day varied as much as 12°C. 24-hour heat summation for these clusters revealed little difference among them. Heat summations for periods of daylight or solar insolation indicate more heat accumulation for clusters on the top of the trellis, at ground level and on the west side of the trellis than on the east side of the trellis. These differences might be usefully exploited when training vines to maximize aspects of fruit maturation in relatively cool climates.

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Paul J. Croft, Mark D. Shulman, and Roni Avissar

Cranberry (Vaccinium macrocarpon Ericaceae Ait.) stomatal conductivity (SC) was investigated in the field to examine plant response as a function of weather conditions. Measurements were made during fruit maturation on 14 days between 0540 and 1710 h r, as weather conditions permitted. SC ranged from 0.02 to 0.08 cm·s-1 and was much lower than for most other crops. Scatter plots of SC vs. leaf temperature by day indicated only a weak linear relationship. When the data were stratified by time of day and by clear and overcast skies, several significant Pearson correlation coefficients suggested a stomatal response. The findings, when combined with current knowledge of the physical structure of cranberry stomata, suggest that cranberries behave as xeromorphic plants.

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M.A. Nagao, E.B. Ho-a, and J.M. Yoshimoto

To study the vegetative flushing pattern of M. integrifolia (cvs. Keaau, Kau and Kakea) trees in Hawaii and determine when these vegetative flushes flower, trees were monitored for an entire year (1988), and shoots from these flushes were monitored for flowering during the 1988-89, 1989-90 and 1990-91 flowering seasons. Flushing occurred year-round but was most frequent during the spring-summer and fall months which coincided with the end of the flowering season and the period of fruit maturation. For all cultivars, sporadic flowering occurred in 1988-89 on shoots that were less than one year-old but was not always associated with the oldest shoots. Flowering in 1989-90 and 1990-91 was observed on a larger proportion of the shoots and occurred on shoots that had emerged throughout 1988. Flowering was most abundant on two year-old shoots (1990-91) and could occur on shoots that had flowered in the previous season (1989-90).

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Andrew G. Reynolds, Margaret Cliff, Douglas A. Wardle, and Marjorie King

Eighty-five cultivars, selections and clones from European winegrape (Vitis spp.) breeding and selection programs were evaluated between 1993 and 1995 in a randomized complete-block experiment. These included Vitis vinifera clones from France as well as Freiburg, Geisenheim, and Weinsberg, Germany. Small yield and fruit composition differences were found amongst the 'Chardonnay' clones. The standard Prosser clone produced wines with highest earthy aroma and acidity and with lowest perfumy aroma, body and finish; Dijon clones 76 and 96 were most perfumy and least vegetal. `Pinot noir' clones also differed somewhat in terms of yield and fruit composition; `Samtröt', `Gamay Beaujolais', and clone Q1342-01 were amongst the most highly colored clones. These clones also tended to have the most intense berry and currant aromas as well as berry, cherry, and currant flavors. These aforementioned clones appear to be highly adaptable to viticultural regions where low heat units during fruit maturation presently limit industry growth.

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William C. Mitchell and Gojko Jelenkovic

The NAD-dependent and NADP-dependent alcohol dehydrogenase activities of strawberries (Fragaria xananassa Duch.) were found to have broad substrate specificities including those alcohols and aldehydes responsible for strawberry aroma and flavor either directly or through their ester products. NAD-dependent activities were greatest against short-chained alcohols, whereas the NADP-dependent activities were most active against aromatic and terpene alcohols. Differences were seen in substrate specificity between receptacle and achene alcohol dehydrogenase activities. Alcohol dehydrogenase activities were found to be developmentally regulated in receptacle tissue and increased during the period of fruit maturation and ripening. Isoelectric focusing of NAD-dependent ADH activities showed that several isozymes of this enzyme exist, that they differ between receptacle and achene tissues, and that they vary among specific genotypes. Our results suggest that NAD- and NADP-dependent ADH activities are integral components of flavor and fragrance volatile production in ripening strawberries.

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D. Scott NeSmith and Gerard Krewer

Plants of the rabbiteye blueberry (Vaccinium ashei Reade) cultivars Brightwell, Climax, and Tifblue were subjected to pollination with bees or to applications of 250 mg·L-1 of gibberellic acid (GA3) to examine the influence on fruit size and maturation period. Plants were thinned to a similar fruit density (FD) 4 weeks after anthesis. `Tifblue' and `Climax' fruit were smaller on GA3-treated than on bee-pollinated plants, but no difference was observed for `Brightwell'. The fruit maturation period for `Climax' was not affected by treatments, but `Brightwell' and `Tifblue' fruit on pollinated plants ripened 2 weeks earlier than fruit on GA3-treated plants. These data suggest that excess fruit load is not the primary factor responsible for the smaller fruit size and lengthened fruit development period resulting from GA3 applications to rabbiteye blueberries.

Open access

S. J. Kays

Abstract

The O2 and CO2 concentration between the shuck and shell and within the nut of individual pecans (Carya illinoensis (Wang.) K. Koch cv. Stuart) was monitored over a 4 week period from predehiscence to post-dehiscence. Internal O2 levels increased after dehiscence from initial concentrations of 16-17% to near that of the external environment after 3 weeks. Internal CO2 concentration, conversely, decreased substantially after dehiscence. Treatment of nuts over the same physiological stages of development with 2.5, 5.0, 10.0, 21.0 and 100% O2 had little effect on the induction and development of the kernel's normal pigmentation. Both high and low O2 levels did, however, produce some discoloration after 21 days of treatment. Changes in the internal nut O2 partial pressure are apparently not a significant factor in the induction and development of the normal complement of pecan kernel pigments during fruit maturation.

Open access

Gene Lester

Abstract

Changes in morphology of epidermal layers and in permeability of mesocarp membranes of ‘Honey Dew’ and netted muskmelon fruits (Cucumis melo L., var. inodorus and reticulatus, respectively) were compared for 10 through 60 days after anthesis to relate tissue changes to storage life. Twenty-day-old netted muskmelon fruit developed lenticular tissue (net) over the entire melon surface. The muskmelon net had become fissured by 50 days after anthesis (10 days postharvest). ‘Honey Dew’ fruit did not develop lenticular tissue nor did the epidermis become fissured. ‘Honey Dew’ and netted muskmelon fruits had similar membrane electrolyte leakage characteristics (60% ± 3%) when harvested ripe, but, after 10 days at 20°C, electrolyte leakage was 70% and 87%, respectively. Membrane electrolyte leakage for both cultivars had a high regression coefficient (R 2 = 0.97) with fruit maturation and postharvest senescence. An intact epidermis indirectly affected mesocarp membrane permeability and perhaps contributed to differences in muskmelon cultivar storage life.