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  • Author or Editor: Mikal E. Saltveit Jr. x
  • HortScience x
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Changes in membrane fluidity at low, non-freezing temperatures are thought to be involved in chilling injury - a physiological disorder of many economically important plants, e.g. banana, cucumber, maize, rice, and tomato. Atmospheres of 12 MPa He or N2 increased the rate of ion leakage from excised cucumber cotyledon discs, cucumber hypocotyl segments and tomato pericarp discs and also increased the threshold temperature at which chilling occurred by 2° to 6°C. Exposure to vapors of the mammalian anesthetics halothane and methoxyflurane reduced chilling injury in the same tissues. The relative effectiveness of the two anesthetics in reducing chilling injury was similar to their relative effectiveness in inducing anesthesia in animals and their relative lipid solubilities. The response of the tissues to halothane and methoxyflurane, which are known to increase membrane fluidity, and to high pressures, which are known to reduce membrane fluidity, are consistent with the hypothesis that a cold-induced phase transition of membranes could be responsible for chilling injury.

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The internal concentration of CO2 and C2H4 and the stage of ripeness was periodically measured in tomato fruit (Lycopersicon esculentum cv. Castelmart) attached to and detached from the plant. An external collection apparatus permitted nondestructive sampling of internal gases. The concentration of CO2 and C2H4 in the collection apparatus had equilibrated with the internal gas concentrations after 18 hr. A 20-fold increase in C2H4 during ripening of detached tomato fruit was paralleled by a 3-fold increase in CO2 concentration. Ripening attached fruit exhibited a 100-fold rise in C2H4 during ripening, but lacked a ripening associated climacteric rise in O02. CO2 did increase 2-fold in an erratic fashion during ripening of attached fruit, but the increase did not show any correspondence to increased C2H4 or ripening associated color changes. In tomato fruit, it appears that a CO2 climacteric per se, which has been considered an intrinsic quality of certain ripening fruit, may not be necessary for the ripening of “climacteric” fruit at all, but may instead be an artifact of using harvested fruit.

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Abstract

Prolonged physiological studies using gas mixtures containing μl/liter levels of a specific gas component (e.g. ethylene or propylene) require a flowthrough system to ensure that the plant or plant part under study is exposed to a relatively constant gas concn. This prevents tissue incorporations and/or emanations (e.g. biosynthesis of ethylene or CO2) from altering the physiological effective gas concn (1).

Open Access

Abstract

A simple, inexpensive method is presented to prepare an effective chemical scrubber which oxidizes volatile organic contaminants in gases. The scrubber is made by mixing 100 ml of 1 M KMnC4 per liter of dust-free Perlite in a large clear plastic bag.

Open Access

Abstract

Gas samples are often extracted from horticultural produce for analysis of ethylene, carbon dioxide, oxygen, and other gases by gas chromatography. This paper outlines procedures for extracting gas samples either by using a syringe needle to puncture a cavity within the fruit or vegetable or by subjecting the fruit or vegetable to a partial vacuum.

Open Access

Abstract

A device is described which maintains a set temperature ± 0.8°C from 5 to 30° above ambient in an inexpensive controlled-temperature chamber. Present construction cost is about $65. Ten chambers have performed satisfactorily during the past 3 years in research projects on chilling injury, seed germination, seeding growth, tissue culture growth, fruit storage, tree storage, and winter dormancy.

Open Access

Abstract

A 39-week production schedule is described in which container-grown apple trees (Malus domestica Borkh. cvs. Red Chief Delicious, Sundale Spur Golden Delicious, and Paulared) are cycled through 4 weeks of cold acclimation, 7 weeks of chilling, 5 weeks of growth before flowering, 21 weeks of fruit growth and maturation, and 2 weeks growth after fruit harvest.

Open Access

Abstract

A survey was conducted to measure the variability among gas chromatographic analyses of ethylene and the variability among the ethylene gas standards used in 22 laboratories in the United States and Canada. The linearity of gas chromatographic responses to injections of 10.0, 1.0, and 0.1 μl/l ethylene in air mixtures had an average coefficient of linear determination (R 2) of 0.9984, with a SD among the R 2 values of only 0.33%. The ethylene concentrations calculated for the laboratory standards varied from 11.3% higher to 21.7% lower than the value assumed by the participant; with an average variance of about 6% lower.

Open Access

Abstract

Firmness of ‘Starkrimson Delicious’ and ‘Golden Delicious’ apples was not significantly different when tested at 0° and 20°C after 26 weeks of storage at 0°. The volume of bruises produced in these cultivars by mechanical impact injury increased with increasing temperature (0°, 10°, 20°, and 30°) when injured, and with increasing holding temperature (0°, 10°, 20°, and 30°) during bruise development.

Open Access

Activity of phenylalanine ammonia-lyase (PAL) is critical in the induction of russet spotting (RS) in leaves of Iceberg lettuce (Lactuca sativa L.). RS is a major postharvest disorder of lettuce caused by exposure to ppm levels of ethylene at = 5C. Both PAL and RS are decreased when lettuce tissue previously exposed to ethylene is stored at = 15C or is transferred from = 5C to = 15C. To study the induction and inactivation of PAL, we exposed lettuce leaves to air ± 10 ppm ethylene at 5C for four days to initially induce high PAL levels. After four days, leaves were treated with water ± 2 mg/L cycloheximide, and transferred to air at 5 or 15 C. In leaves previously exposed to ethylene, PAL activity decreased rapidly to baseline levels within two days in non-cycloheximide treated leaves transferred to 15C. PAL activity remain elevated in the same treatment held at 5C. In leaves treated with cycloheximide and transferred to 15C, PAL did not begin to decrease until after four days. Cycloheximide treated leaves held at 5C showed increased PAL activity both two and four days after treatment.

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