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  • Author or Editor: Max W. Williams x
  • Journal of the American Society for Horticultural Science x
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Abstract

The growth retardants 2-chloroethylphosphonic acid (ethephon) and succinic acid-2-2-dimethylhydrazide (SADH) increase flower initiation in young apple trees. At comparable rates, ethephon is more effective than SADH. High rates of ethephon cause flower and fruit abscission. When ethephon was combined with SADH and applied 4 to 5 weeks after bloom, satisfactory promotion of flower bud formation was obtained with lower rates of each chemical with a min of undesirable side effects.

Open Access

Abstract

In late September of 1981 and 1982, eight-year-old ‘Oregon-spur Delicious’ apple (Malus domestica) trees on M7 rootstock were sprayed immediately after harvest with 500 ppm AVG. The following spring of both years the number of spur leaves and lateral shoots on one-year-old wood was increased on treated trees. Total N was reduced and sucrose and fructose were increased in dormant one-year-old shoots of AVG-treated trees. Cold hardiness was not affected. Throughout the dormant period both apical and one-year-old lateral buds excised from treated trees and incubated in the dark at 24°C produced less ethylene over a period of 24 hr than buds from untreated trees. In situ ethylene production from apical buds of treated trees was also reduced as growth resumed in the spring. Chemical name used: N-(phenylmethyl)-lH-purin-6-amine (AVG).

Open Access

Abstract

Cytokinins and gibberellins applied to dormant buds on young apple trees significantly increased the number of growing buds and the angle between the main trunk and the new shoot. Total shoot growth on treated trees was nearly double that of control trees. Nursery trees treated with growth regulators several weeks before planting produced branches with wide crotch angles from which good permanent primary scaffold limbs could be selected.

Open Access

Abstract

Fruit color of ‘Golden Delicious’ apples was closely related to N content and color of leaves. This relationship was significant for both spur leaves and mid-terminal leaves. Prediction of fruit color from spur and mid-terminal leaves was obtained in late July and mid-September. Nitrogen content was higher in the mid-terminal leaves than in the spur leaves.

Open Access

Abstract

Fruit growth measurements in several orchards, from 1959 to 1968 have been used to prepare a table for predicting final harvest size of ‘Bartlett’ pears. At 60 days from full bloom, final fruit diameter to within ⅛ inch can be accurately predicted 83% of the time. The nearer to harvest the sample is taken, the more accurate the harvest size prediction. Temperatures above 80° and below 55°F appear to reduce pear fruit growth.

Open Access

Abstract

The levels of auxin, gibberellin, and cytokinin were measured using bioassay methods in pruned and unpruned apple trees (Malus domestica Borkh. cv. McIntosh). Vigorous shoot growth following heavy dormant pruning was accompanied by an increase in cytokinin concentration in the tissues in the early spring. As cell division and cell expansion progressed, the levels of auxin and gibberellin increased. The gibberellin activity in samples from pruned trees was 3 times higher than in samples from unpruned trees. Pruning diminished the midsummer level of cytokinins in the annual shoots.

Open Access

Abstract

Summer pruning, dormant pruning, and growth-regulator treatments were applied for 5 years on newly planted ‘McIntosh’ and ‘Melba’ apple trees (Malus domestica Borkh.) on Alnarp 2 and Mailing 26 rootstocks. All forms of pruning reduced tree growth and yield. Light-to-moderate pruning was the best treatment for forming tree canopies. The reported stimulative effect of summer pruning on flower bud formation was not supported by this research. Pinching shoot tips led to a new secondary growth and inhibited rather than stimulated flower bud formation.

Open Access