SOME PHYSIOLOGICAL RESPONSES AND PROBLEMS OF OVERTREE MISTING FOR BLOOM DELAY ON 'GOLDEN DELICIOUS' APPLES.

摘要

The effects of overtree misting for bloom delay on 'Golden Delicious' apple trees were assessed over a period of three years. Misting caused a 13 day delay of full bloom in 1977 and a six day delay in 1978 and 1979. Fruit set of open pollinated flowers on misted trees was lower than that on nonmisted trees in 1979. Fruit set of flowers pollinated with 'Jonathan' pollen or the flower's own pollen was lower on the misted trees than on the nonmisted trees. Percent germination of pollen from misted trees was lower than that from nonmisted trees. Fruit set counts taken at specific time intervals relating to the abscission waves of apples showed that there was no difference due to misting treatments in fruit set influenced by pollination. Counts taken to reflect the influences of fertilization and nutritional competition showed that the misted trees had lower fruit set at both times than nonmisted trees. Soil water content was increased and percent air space reduced in the soil beneath the misted trees. There were no differences or sudden changes in percent relative water content of spur-leaves between misted and nonmisted trees. Misted MM 111 rootstocks that were placed in the field prior to the onset of misting in 1978 had lower levels of total nonstructural carbohydrates in the current season's leaves and roots than the nonmisted rootstocks after the completion of misting. Misting treatments had no apparent affect on the net photosynthesis or transpirational rates of the misted and nonmisted MM 111 rootstocks. Percent N of spur-leaves in 1978 and 1979 was lower at petal fall in the misted trees than in the nonmisted trees, with no differences in August leaf samples. The Ca and Mg concentrations of the misted trees were higher in the flowers and spur-leaves at full bloom than nonmisted trees and leaf Ca levels were lower in the misted trees in August samples in 1978 and 1979 than the no misted trees. Levels of B were lower in the misted flowers at full bloom and in the spur-leaves at petal fall than the nonmisted trees in 1978 and 1979. Soil applications of CaNO(,3) in 1977 and foliar applications of B in 1979 in misted and nonmisted blocks did not increase fruit set. Foliar applications of SADH + B in 1977 and B in 1978 that were applied as limb treatments increased fruit set of the misted trees. Levels of B in the flowers in 1979 of the misted trees were lower than the levels in the nonmisted flowers even with the application of foliar B sprays.