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  • Author or Editor: R. Mason x
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Interactions of ethephon and irradiance reduction were investigated in terms of flower bud blasting in Easter lily (Lilium longiflorum Thunb. `Nellie White'). Silver thiosulfate (STS) was investigated as an inhibitor of ethylene-induced bud abortion. Fourteen days of 92% irradiance reduction significantly increased bud abortion when plants were exposed to 2.1 mm ethephon. Bud abortion was 39% and 60% for plants grown in ambient and reduced irradiance, respectively. Silver thiosulfate was applied to plants 2 or 3 weeks after the date of the first visible bud, followed by ethephon treatment 2 days later. Bud abortion was significantly reduced by 1 or 2 mm STS, without phytotoxicity. Pretreatment with 1 or 2 mm STS as early as 4 weeks before ethephon exposure significantly reduced ethephon-induced bud abortion. Silver thiosulfate application could inexpensively reduce flower bud abortion during latter stages of greenhouse forcing of Easter lilies.

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Ethylene accumulation increases after harvest and culminates in needle abscission in balsam fir [Abies balsamea (L.) Mill.]. We hypothesize that water deficit induces ethylene evolution, thus triggering abscission. The purpose of this research was to investigate the role of temperature and humidity on postharvest needle abscission in the presence and absence of exogenous ethylene and link vapor pressure deficit (VPD) to postharvest needle abscission in balsam fir. In the first experiment, branches were exposed to 30%, 60%, or 90% humidity while maintained at 19.7 °C (VPD of 1.59, 0.91, or 0.23 kPa, respectively); in the second experiment, branches were exposed to 5, 15, or 25 °C (VPD of 0.35, 0.68, or 1.26 kPa, respectively) while maintained at 60% relative humidity. Needle retention duration, average water use, xylem pressure potential relative water content, and ethylene evolution were response variables. Reducing water loss or xylem tension by changing temperature or humidity effectively delayed needle abscission, although the 90% humidity treatment had the most profound effects. In the absence of exogenous ethylene, branches placed in 90% humidity had a fivefold increase in needle retention, 67% decrease in average water use, and had a final xylem pressure potential of –0.09 MPa. There was a near perfect relationship between VPD and needle retention (R2 = 0.99). These findings suggest that increasing xylem tension or decreasing water status may trigger ethylene synthesis and needle abscission. In addition, these findings demonstrate an effective means of controlling postharvest needle abscission by modifying temperature and/or relative humidity.

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Abstract

Root growth of pine (Pinus mugo var. mughus (Scop.) Zen.) was studied at a rhizotron (underground root observation laboratory) on an in situ basis. Greater root elongation occurred in peat than in mineral soil and when there were sustained periods of temperature extremes, root growth increased or decreased 2 to 5 days following increases or decreases in soil temperature.

Roots of poplar (Populus alba var. pyramidalis Bunge), grown in glass-sided boxes under controlled growth conditions, suberized more quickly when exposed to natural and artificial light than when kept in the dark.

Open Access

Abstract

Each of 11 cultivars of sweet corn (Zea mays L.) was presented to red-winged blackbirds (Agelaius phoeniceus L.) in an aviary under no-choice conditions in 1985. This evaluation was repeated in 1986 with eight cultivars, five of which had been tested in 1985. In both years, there were significant differences in damage among cultivars; the damage rankings of the cultivars tested in both years were correlated. Total husk weight and husk weight beyond the cob tip individually explained 68% to 69% of the variation in damage among cultivars. Husk characteristics were more important than kernel characteristics in determining the amount of damage a cultivar received. Six of the cultivars evaluated in a field test near a blackbird roost showed differences in damage similar to that found in the aviary. In the field test, the most- and least-resistant cultivars had 16% and 76% of the ears damaged, respectively. Resistance is a viable approach to reduce damage in situations where sweet corn is grown near concentrations of blackbirds.

Open Access

Abstract

Kernels from Juglans regia walnuts stratified at 0°C were sampled at weekly intervals and extracted with methanol. The extracts were partitioned into 4 phases which were water, neutral ether, acidic ether and acidic butanol, then bioassayed for cytokinins, gibberellins, auxins and inhibitors. No cytokinins nor gibberellins were found in the tissue. There was activity analogous to that from auxins. An inhibitor which diminished during stratification was found. This inhibitor is believed to be abscisic acid, on the basis of UV absorption spectrum, Rf values established by co-chromatography on paper and silica gel plates, and derivatives analyzed by gas liquid chromatography.

Open Access

Abstract

In situ root growth of young plum trees (myrobalan rootstock on which ‘Shiro’ plum was budded) was studied for one season at the University of Guelph rhizotron. Root growth of this combination, at the field-transplant stage, began before leaf growth and extended past leaf fall. Relatively large roots of myrobalan stock made some winter growth in length, below frost penetration. The rate of growth during July to mid-September was twice that of the balance of the season, corresponding closely to shoot and trunk increments. Root diameter and elongation rate are positively correlated. Irregular and patchy suberization was the rule with the young plum roots.

Open Access

Abstract

Softening of ‘McIntosh’ apples (Malus domestica Borkh.) during storage was reduced by dipping fruit 2 days after harvest in 4% CaCl2 solution (40 g of commercial CaCl2 in 1 liter of water). The addition of Keltrol, a commercial food thickener, at 3 g/liter to retain more Ca solution on the fruit increased the effectiveness of the treatment. After 4 months storage at 0°C, fruit treated with CaCl2 and with CaCl2 plus Keltrol was 0.30 and 0.56 kg firmer by the pressure test than untreated fruit.

Open Access

Abstract

Mason, Henneberry, and Lehr (1) and Stoner and Mason (2, 3) reported differences in the resistance of tomato varieties to Drosophila melanogaster. They compared varieties representing a wide sample of those developed and grown commercially in the United States in recent years. Their tests included varieties with large and small fruits, round and paste types, those adapted for hand and machine-harvesting, and those used for processing and fresh market.

Open Access

There is strong evidence that Ambiol® (a derivative of 5-hydroxybenzimazole) promotes drought tolerance in many plants; it is often suggested that this is the result of its antioxidant properties. Recent evidence has also shown that several natural antioxidants promote carrot germination under drought stress. Thus, it was hypothesized that seed preconditioning using natural antioxidants might confer drought tolerance. Ambiol®, ascorbic acid, β-carotene, lutein, and lycopene were chosen as antioxidants at concentrations of 0.1 mg·L−1, 1.0 mg·L−1, and 10 mg·L−1. A preconditioning treatment was applied by soaking tomato (Solanum lycopersicum L.) seeds in an antioxidant solution for 24 h. Of the antioxidants tested, 10 mg·L−1 Ambiol®, 1.0 mg·L−1 β-carotene, 1.0 mg·L−1 ascorbic acid, and 0.1 mg·L−1 lycopene were shown to increase shoot dry mass by 114%, 94%, 56%, and 83%, respectively, in droughted seedlings when compared with a droughted control. Similar benefits were observed in root dry mass, leaf area, photosynthesis, and water use efficiency. Proteins were extracted from the seeds of certain treatments, before and after germination, and separated using isoelectric focusing. Specific proteins were found to be induced through all preconditioning treatments, whereas Ambiol® and β-carotene were found to induce specific proteins, independent of those induced through imbibition, both before and after germination. This result suggests that Ambiol® and β-carotene evoke specific proteins that may confer drought tolerance to the key physiological processes studied. In addition, protein profiles of ascorbic acid, β-carotene, and Ambiol® after germination had fewer visible bands than the controls, suggesting an accelerated mobilization or conversion of proteins within the seed.

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