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- Author or Editor: Robert D. Belding x
- Journal of the American Society for Horticultural Science x
Abstract
One-year-old apple trees (Malus domestica Borkh., MM. 106) were subjected to all combinations of 10° and 20°C root and shoot temperatures after their chilling requirement had been satisfied at 4°. Tree root temperature of 20° significantly increased percent budbreak over trees with roots at 10°. Trees with a shoot temperature of 20° caused accelerated budbreak over trees with 10° shoots, but the final (day 18) total budbreak was not different due to shoot temperatures. Shoot temperatures strongly influenced extension of new shoots, starch breakdown in fibrous roots, and soluble sugar increase in fibrous roots and root shank. Shoot temperature of 20° increased all these parameters over the 10° shoot temperature.
Variation in amount and composition of epicuticular wax among several apple (Malus ×domestica Borkh.) cultivars was characterized by gas chromatography, thin-layer chromatography, and gas chromatography-mass spectroscopy. Across cultivars, wax mass ranged from 366 to 1038 μg·cm-2. Wax mass decreased during the 30 days before harvest. Ursolic acid accounted for 32% to 70% of the hydrocarbons that make up the epicuticular wax. Alkanes, predominantly 29-carbon nonacosane, comprised 16.6% to 49%. Primary alcohols of the hydrocarbons ranged from 0% to 14.6% of the epicuticular wax. Secondary alcohols of the hydrocarbons were the most cultivar specific, making up 20.4% of the epicuticular wax in `Delicious' and only 1.9% `Golden Delicious' strains. Aldehydes and ketones of the hydrocarbons represented a small amount of total wax, ranging from 0% and 6.0%. Percentage of primary alcohol in the epicuticular wax increased as fruit developed. Other components showed no distinct trends with fruit development. Examination of the ultrastructure of cuticular wax using scanning electron microscopy revealed structural differences among cultivars.