Volume 62 Number 4 Article 3
Year 2008 Month 10
Title: Modification of Branching Behavior in Apical-Dominant Apple Trees with Plant Growth Regulators and Their Residual Effects on Tree Growth After Transplanting
Authors: T. Jacyna, J. Barnard
Abstract:
Nursery trees of apple hybrids NY73334-35, NY75413-30 and NY75414-1 were treated once or twice with the
plant growth regulator (PGR) Accel or Promalin, alone or in combination, to induce branching.
Regardless of the
PGR used, or the rate and frequency of application, treated trees produced more shoots per tree than untreated control
trees for all three hybrid selections.
Medium [750 mg•L-1 N-(phenylmethyl)-1H-purine-6-amine (6 benzyladenine
or BA)] or high rates (1000 mg•L-1 BA) of both compounds were more efficient in shoot induction than low rates
(500 mg•L-1 BA). When comparable rates of both chemicals were applied, no differences in the number of lateral
shoots, shoot length distribution, total tree extension growth and apical dominance among chemical treatments
were noted.
Regression analysis on rates of Accel and Promalin vs. total number of shoots demonstrated that Accel
promoted a linear increase in this characteristic, whereas Promalin caused a parabolic effect on branching.
The
trees treated once or twice in the nursery at medium rates of either compound were transplanted into the orchard.
One year after transplanting the trees exhibited a pronounced increase in the total number of shoots and their extension
growth, and also considerable reduction in apical dominance.
It is believed that those changes may facilitate
canopy training, and thus accelerate the onset of bearing.
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