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Seedling plugs of `Better Boy' tomato plants (Lycopersicon esculentum Mill.) were potted in 60% processed fiber: 40% perlite (by volume) media amended or nonamended with either crystalline or powdered hydrophilic polymer (2.4 kg·m-3), and treated with one of several concentrations (0%, 2.5%, 5%, 7.5%, and 10%) of antitranspirant GLK-8924, at the four true-leaf stage. Plants were either well-irrigated or subjected to short-term water stress, withholding water for 3 days, after antitranspirant GLK-8924 application. Leaf stomatal conductance, transpiration rate, whole-plant transpirational water loss, and growth were depressed by short-term water stress and antitranspirant GLK-8924. In contrast, hydrophilic polymer amendment increased plant growth, resulting in higher transpirational water loss. The depression of stomatal conductance and transpiration rate by short-term water stress was reversed completely in 2 days after rewatering while the reduction of plant growth rate diminished immediately. The effects of antitranspirant GLK-8924 were nearly proportional to its concentration and lasted 8 days on stomatal conductance and transpiration rate, 4 days on plant growth rate, and throughout the experimental period on plant height and transpirational water loss. Plant growth was reduced by antitranspirant GLK-8924 possibly by closing leaf stomata. In contrast, hydrophilic polymer amendment resulted in larger plants by factors other than influences attributed to stomatal status. Hydrophilic polymer amendment did not interact with antitranspirant GLK-8924 on all variables measured. The application of antitranspirant GLK-8924 was demonstrated to be useful for regulating plant water status, plant growth, and protecting plants from short-term water stress.

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Experiments were conducted to determine the effect of pre-treatments with abscisic acid (ABA), silver thiosulfate (STS), or ethylene on transpiration rate of Chrysanthemum morifolium L. cv. Bright Golden Anne during the dark. ABA and STS reduced subsequent dark transpiration, while exposure to ethylene increased it. Treatment with STS partially reduced the influence of ethylene. These results indicate the possibility of using pre-treatments to reduce water loss under dark shipping/storage conditions.

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A portable, nondispersive infrared (NDIR) gas analyzer was modified to measure the concentration of CO2 and water vapor in small gas samples. A 2-mL gas sample was taken from a series of sealed flasks partially filled with a saturated solution of chemicals known to produce various levels of relative humidity (RH). The modified NDIR instrument quantified water vapor content by its absorption at 2.59 μm. Peak height was displayed on a strip chart recorder and a standard curve constructed. At a specific temperature, the vapor pressure (VP) and vapor pressure difference (VPD) were calculated for sweet pepper (Capsicum annuum L., cv. Mazurka) fruit packed in trays that were covered with plastic films having several levels of perforations. Water loss from the fruit was highly correlated with VPD inside the packages. The modified NDIR instrument has an advantage over other instruments used to measure RH because it can rapidly and simultaneously determine the concentration of water vapor and CO2 in a single injection of a small gas sample.

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Broccoli (Brassica oleracea L., Italica Group) was held at 5°C in a stream of humidified air (control) or of humidified 14% O2/10% CO2 (CA), or it was wrapped with a nonperforated flexible polyvinylchloride (PVC) film and held in a humidified (90% to 95% RH) or nonhumidified (40% to 45% RH) stream of air for 3 weeks. Water loss was reduced 17% by the CA treatment and 50% by wrapping the broccoli. Broccoli stored in CA or wrapped in film retained quality significantly better than the controls. Atmosphere composition within packages reached equilibrium within the first 24 hr and did not change significantly over the 3 weeks. Self-generated atmosphere modification was greater within packages held in humidified air than within those held in nonhumidified air (7.8% vs. 13.2% O2; 9.0% vs. 6.7% CO2, respectively). The steady state of atmospheres within packages allowed the calculation of respiration rates of wrapped broccoli by monitoring changes in the air surrounding the package. Oxygen consumption and CO2 production by samples held in CA or in films were reduced 30% to 40% relative to the controls. The respiratory quotient for the CA and humidified wrapped samples was about 1.30, but 1.15 in the control and nonhumidified wrapped samples.

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Abstract

‘Magnum 45’ muskmelon fruit, (Cucumis melo L. var. reticulatus Ser.) either shrink-film-wrapped to maintain a water-saturated microatmosphere or non wrapped, were stored in 4°C, 85-95% RH, and were sampled at 10-day intervals for 40 days postharvest. Fruits maintained in a water-saturated microatmosphere via shrinkwrap exhibited no significant change in percentage of dry weight, firmness, soluble sugars, β-carotene, or a loss of membrane integrity throughout 40 days storage. Shrink-wrap fruit had a 1% reduction in fresh weight, and a decline in appearance rating and surface browning by 40 days postharvest but were generally rated as excellent to good salable quality. Unwrapped fruit maintained in 85-95% RH exhibited progressive decline in appearance, surface browning, percentage of dry weight, soluble sugars, mesocarp firmness, and loss of membrane integrity. No change was observed in β-carotene. Non wrapped fruit had a 5.7% reduction in fresh weight within 20 days postharvest and were generally rated as fair to poor salable quality. Mesocarp membrane integrity during postharvest storage was highly dependent on percentage of fresh weight loss over time for both shrink-film-wrapped and non wrapped muskmelon fruit.

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The effects of SO2 and NO2, singly and in combination, on the growth and physiology of nontuberizing Solarium tuberosum L. `Russet Burbank' plants were studied in controlled conditions. Plants were exposed to 0.11 μl SO2 and/or 0.11 μl NO2/liter for 24 hours a day up to 10 days. Statistically significant effects were observed mainly in the SO2+ NO2 treatments compared with the control plants. Leaf area was reduced from day 2 onward, and root fresh and dry weights were reduced from day 4 onward. Significant reductions in leaf and stem dry weights occurred on day 6. Net CO2 exchange rates were reduced for SO2 exposed compared with control plants beginning on day 3, while water loss rates were increased with SO2 + NO2 beginning on day 3. The increases in water loss rate were possibly due to the development of cuticular injury observed as abaxial glazing on the upper and middle canopy leaves. Leaf osmotic potential (π) of plants with SO2 + NO2 became more negative within the first 24 hours of the exposure. This reduction was accompanied by an increase in reducing sugar concentration. Xylem water potential was reduced in the mature and expanding leaflets by day 2 of the SO2 + NO2 exposure. The most sensitive aspect of the action of SO2 + NO2 appeared to be the increase in reducing sugars that affected osmotic potential in the leaves. Considering the retardation of root growth, these data suggest that the pollutant gases may have interfered with partitioning of dry matter from the leaves to the roots.

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We determined transpiration rate, survival, and rooting of unmisted, softwood cuttings of `Autumn Flame' red maple (Acer rubrum L.) and `Indian Summer' Freeman maple (Acer ×freemanii E. Murray). Effects of perlite at 24, 30, and 33 °C were assessed to determine whether responses of cuttings would be consistent with cultivar differences in resistance to root-zone heat previously shown with whole plants. During 7 d, cutting fresh mass increased by ≈20% at all temperatures for `Autumn Flame' red maple, but fresh mass of `Indian Summer' Freeman maple decreased by 17% and 21% at 30 and 33 °C, respectively. The percentage of cuttings of `Indian Summer' that were alive decreased over time and with increasing temperature. Transpiration rate decreased during the first half of the treatment period and then increased to ≈1.1 and 0.3 mmol·m-2·s-1 for `Autumn Flame' and `Indian Summer', respectively. Mean rooting percentages over temperatures for `Autumn Flame' and `Indian Summer' were 69 % and 16%, respectively. Mean rooting percentages at 24, 30, and 33 °C over both cultivars were 74%, 29%, and 25%, respectively. Over temperatures, mean root count per cutting was 41 and seven, and mean root dry mass per cutting was 4.9 and 0.4 mg, for `Autumn Flame' and `Indian Summer', respectively. Use of subirrigation without mist to root stem cuttings was more successful for `Autumn Flame' than for `Indian Summer'. Temperature × cultivar interactions for cutting fresh mass and the percentage of cuttings remaining alive during treatment were consistent with previous evidence that whole plants of `Autumn Flame' are more heat resistant than plants of `Indian Summer'. Mass and survival of stem cuttings during propagation in heated rooting medium may serve as tools for screening for whole-plant heat resistance among maple genotypes.

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‘Marsh’ grapefruit (Citrus paradisi Macf.) were seal-packaged in low-density, polyethylene films ranging from 20 to 40 µm in thickness and stored at temperatures from 5 to 28°C for periods up to 109 days. Film thickness had a negligible effect on transpiration, respiratory gas exchange, and juice quality. Storage temperature had a negligible effect on transpiration of seal-packaged fruit. However, 28° storage temperature significantly affected acid concentration in both seal-packaged and unwaxed fruit, probably as a result of increased respiratory activity at high storage temperatures. Quality of both seal-packaged fruit and unwaxed fruit deteriorated in storage at 28°.

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Upon microscopic examination, no stomata were found within 3 mm of the button in an area typically immune to stem end rind breakdown. Stomata outlined the oil glands 7 to 10 mm from the button in peel susceptible to this disorder. Heavy deposits of epicuticular wax were also found in the area void of stomata. Total epicuticular wax was inversely correlated to postharvest wt loss of ‘Valencia’ oranges (r2 = 0.94). A 1-min petroleum ether extraction of soft wax components increased wt loss 66% over washed-only fruit and resulted in etched patterns in the wax platelets suggesting that the soft and hard waxes are not uniformly mixed. A 1-min wax extraction with CCL4 : hexane (1 : 1 v/v) removed 85.6% of the surface wax and increased wt loss to 3 times that of the washed-only fruit over 24- and 48-hr time periods.

Open Access

Heliconia (Heliconia spp.), red ginger (Alpinia purpurata), and bird-of-paradise (Strelitzia reginae) inflorescences have similar stem structures and postharvest handling regimes. Inflorescences, especially heliconia, should be harvested in the morning while still turgid, and at the most suitable stage of development which varies with the species, its proposed use, and market requirements. Treatments that extend postharvest vase life, either or both enhance water uptake or prevent water loss and provide an exogenous energy source. Use of the most suitable temperature for shipping and storage prolongs vase life. Heliconia should be shipped and stored at >10 °C (50.0 °F), red ginger >12 °C (53.6 °F), and bird-of-paradise at >8 °C (46.4 °F). Sucrose (10% w/v), citric acid [150 mg·L-1 (ppm)] and 8-hydroxyquinoline citrate (250 mg·L-1) are major chemicals used in pulsing and holding solution for bird-of-paradise. Holding solutions for red ginger are similar except 2% (w/v) sucrose is recommended. The response of heliconia inflorescences to different pulsing and holding solutions has been shown to be negligible. A 200-mg·L-1 benzyladenine spray extends the vase life of red ginger and heliconia. Hot water treatment of red ginger at 49 °C (120.2 °F) and 50 °C (122.0 °F) for 12 to 15 min extends postharvest vase life, kills most of the pests that infest red ginger, and reduces the geotropic response. The major postharvest problems are saprophytic mold on bird-of-paradise, negative geotropic response of red ginger, and insect infestation of all three flowers. There is no reported method to control the postharvest nectar and slime production on bird-of-paradise that provides a substrate for saprophytic mold growth. Dipping inflorescences in benomyl or thiobendazole (TBZ) at 200 mg·L-1 does help control postharvest mold growth in bird-of-paradise and heliconia. Compared to most temperate flowers, there is a need for greater understanding of morphological and physiological factors that limit the vase life of heliconia, red ginger and bird-of-paradise flowers.

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