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  • Author or Editor: Kathleen B. Evensen x
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Abstract

Six cultivars of cantaloupe-type muskmelon (Cucumis melo L.), grown in central Pennsylvania, were harvested at the yellow full-slip, green full-slip, or half-slip stages of maturity and evaluated for quality after storage at 0° or 4.5°C. Fully ripe (yellow full-slip) melons had excellent appearance and flavor at harvest, but they deteriorated rapidly in storage, as shown by loss of flavor and ascorbic acid, development of stem-end cracks and decay, and water-soaking of the flesh. Of the 3 maturity stages, green full-slip melons had the highest soluble solids and ascorbic acid content and excellent flavor at harvest, and maintained flavor and appearance best in storage. Halfslip melons maintained a good appearance during storage, but were slightly inferior in flavor to full-slip melons. No evidence of chilling injury was found for melons harvested at any of the maturity stages and stored up to 2 weeks at 0° plus 1 day at 13°; in fact, melons stored at 0° were superior to those stored at 4.5° because less decay was evident.

Open Access

We studied the effects of environmental conditions during production on susceptibility of roses to postharvest infection by B. cinerea. For flowers harvested from a commercial greenhouse, susceptibility was linearly correlated (r = 0.97) with mean air velocity during the 5-week periods before each harvest. Susceptibility was also correlated with mean leaf to air temperature gradient (r = 0.83) and inversely correlated with wetness measured on an electronic leaf (r = -0.92), but these correlations were interpreted as secondary effects of the correlation with air movement. Susceptibility was not correlated with temperature, relative humidity (RH), or the other factors measured. In growth chamber experiments, flowers grown under high wind speed (0.55 m·s-1) were significantly more susceptible to infection than flowers grown under low wind speed (0.18 m·s-1). High relative humidity during production increased background infection levels (i.e., those infections not caused by laboratory inoculation) but did not affect susceptibility.

Free access

Postproduction quality, net C exchange, and petal abscission in response to ethylene were compared following forcing at 21(day)/16C(night) or 18/13C(18-hour photoperiod) of two cultivars of Pelargonium × domesticum L.H. Bailey. Fewer petals of 2- to 6-day-old florets abscised in response to 60 minutes of 0.7 μl ethylene/liter on plants forced at low temperature than on plants forced at 3C higher temperature. Forcing temperature did not affect floret longevity or the number of florets opening during forcing, but the floral display under simulated consumer conditions was prolonged in low-temperature plants by the continued development of buds. Dark respiration rates at 21C were lower in leaves from plants forced at low temperature than in leaves of plants forced at the higher temperature. Differences in postproduction quality between plants forced at high and low temperatures may have been related to the reduced rate of carbohydrate depletion in low-temperature plants.

Free access

Abstract

Flower longevity (as influenced by stage of maturity at harvest), dry weight, and flower preservative were studied using cut flowers of herbaceous peony (Paeonia spp.) cultivars Felix Crousse, Festiva Maxima, John C. Lee, Mons. Jules Elie, and Richard Carvel. Flowers harvested in the tight calyx stage frequently failed to open or opening was delayed. No substantial difference in longevity between flowers harvested at the loose calyx stage or first loose petal stage was found. Those cut at the loose calyx stage maintained quality well during dry storage at 0°C for up to 4 weeks. Vase-life and days to opening differed significantly with cultivar, length of storage, and their interaction. Fresh weight increased before or during flower opening, and the increase was greater after storage than for unstored flowers. Inclusion of a floral preservative in the vase solution increased gain in fresh weight upon hydration after storage and weight throughout vase-life.

Open Access

Ethylene-regulated gene expression is being studied in several plant systems, but the exact mechanism of ethylene action during plant development and senescence is poorly understood. When geranium (Pelargonium Xhortorum) flowers are exposed to 1 μ1/L of ethylene gas for 1 hour, petals begin to abscise within 60-90 minutes from the start of treatment, The rapidity of the response implies that it must be very direct. We now demonstrate that ethylene acts at the level of message accumulation. We have constructed a cDNA library from mRNA isolated from ethylene-treated geranium gynoecia. Ethylene-induced clones have been isolated by differential screening of this library with cDNA probes synthesized from ethylene-treated and untreated geranium gynoecia mRNA. Identification and characterization of these clones will be discussed.

Free access

Abstract

Continuous, low intensity, far red (FR) irradiation prevented germination, and continuous, low intensity, red (R) irradiation decreased the rate of germination of seed of dw-2 dwarf watermelon [Citrullus lanatus (Thunb.) Matsumara and Nakai]. Intermittent, 15 minute light treatments with R or FR at 6 hour intervals affected germination similarly to continuous irradiations. Seeds germinated best in darkness and would germinate in darkness following prolonged incubation in FR light. A short exposure to R light following a prolonged FR treatment enhanced subsequent germination in darkness (D), and the effect of R light was reversed by a short exposure to FR light, indicating phytochrome control of germination. Responses to single, short exposures to FR light after different periods of incubation, and to different intervals of D and prolonged FR light, indicated that germination of dwarf watermelon seeds is regulated by phytochrome between about 6 to 24 hours of incubation at 29 to 30°C.

Open Access

Impatiens (Impatiens × hybrida `Impulse Orange'), and marigold (Tagetes × hybrida `Janie Tangerine') plants grown under low phosphorus were more resistant to drought stress than plants grown with a conventional, high-P fertilization program. Low concentrations of P were supplied using alumina-buffered P incorporated into the peat media. Alumina was charged with two levels of P, giving two levels of P-desorption. The alumina-buffered P amendment amounted to 2% by volume of the medium. Control plants (high-P treatment) were fertilized with a nutrient solution containing a P concentration of 1.5 mm. Phosphorous leaching was reduced by 96% to 99.4% in the low-P treatments compared with controls. Low-P plants showed no signs of P deficiency or aluminum toxicity. Impatiens plant diameter was significantly reduced by low-P fertilization, and leaf area was reduced by low P in both species. In marigold plants, roots were confined to a small volume beneath the drip tube in high-P plants, while in low-P plants they were well distributed through the medium. Impatiens roots showed no obvious differences in root distribution. Plants at the marketing stage were exposed to drought. The low-P plants of both species wilted more slowly and recovered more quickly when irrigated than the high-P controls. The reduced leaf area on the low-P plants may account for the improvement in drought tolerance.

Free access

Grading criteria are proposed for judging potatoes (Solanum tuberosum) for chip quality and yield. The criteria were derived from a decision-making scheme developed from expert opinions, U.S. Dept. of Agriculture grades, and a statistical evaluation of stored potatoes. The criteria are presented as ranges of acceptable values for a limited set of variables found to be important for chip quality and yield. These variables include bruising, cracks, cuts, fusarium dry rot, lesions, and scab. The proposed criteria, besides being a practical decision-making tool for processors, could serve as a knowledge base for potato expert systems and the development of mechanized sorting equipment.

Full access

Abstract

‘Valencia’ oranges (Citrus sinensis (L.) Osbeck) damaged with rust mite (Phyllocoptruta oleivora Ashmead) responded to the abscission-accelerating chemical glyoxal dioxime (ethanedial dioxime) with greater ethylene production and greater reduction in bonding force than undamaged fruit. More than 90% of the 14C-glyoxal dioxime taken up by the rind was absorbed during the first 24 hrs. Absorption of 14C-glyoxal dioxime by rind tissue of mite-damaged fruit was more rapid than that of undamaged fruit. The differences in uptake of 14C-glyoxal dioxime due to mite damage were greatest on the first day after treatment, which was also the time of maximum ethylene production in response to glyoxal dioxime. The increased uptake in mite-damaged fruit is partially responsible for the increased effectiveness of glyoxal dioxime. It is likely that mite-damaged fruit are more permeable to many agricultural chemicals than undamaged fruit.

Open Access

Abstract

Ethylene production in peel explants of ‘Valencia’ oranges [Citrus sinensis (L.) Osbeck] treated with 5-chloro-3-methyl-4-nitro-1H-pyrazole (Release) was similar in pattern to ethylene production by whole fruits treated with the chemical. Smaller amounts of ethylene were produced by untreated peel explants. Explants from fruit harvested in October and March showed similar patterns of ethylene evolution when untreated and when Release was applied. The response to this chemical was localized in the flavedo. Ethylene production was dependent on temperature in both untreated and Release-treated peel explants, but the ethylene response to the chemical was particularly temperature-dependent. The temperature optimum in both cases was approximately 25°C. Peel disks from regreening fruit generally produced less ethylene than disks from nongreening fruit when Release or glyoxal dioxime (ethanedial dioxime, Pik-Off) was applied. The magnitude of the difference between regreening and nonregreening disks depended on the concentrations of Pik-Off or Release applied.

Open Access