GROWTH REGULATORS AND THE FLOWERING OF EVERGREEN AZALEAS (RHODODENDRON CV.)
GROWTH REGULATORS AND THE FLOWERING OF EVERGREEN AZALEAS (RHODODENDRON CV.)
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Date
1960
Authors
Ballantyne, David J.
Advisor
Link, Conrad B.
Citation
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Abstract
Spraying experiments were conducted in 1958 and 1959
to find the effectiveness of certain growth regulators upon
multiple flower bud formation and rate of flower bud development
of evergreen azaleas. Paper chromatograms of extracts
of vegetative buds and of flower buds treated with 37°F.
storage and potassium gibberellate (GAk) sprays, were tested
with a wheat coleoptile bioassay in 1959.
Foliar sprays of 2, 3, 5-triiodobenzoic acid (TIBA),
an antiauxin, showed evidence of inhibiting multiple flower
bud formation, and a foliar spray of 2,200 ppm indoleacetic
acid (IAA) tended to promote multiple flower bud formation.
The time of spraying in relation to the time of floral
initiation apparently is important if growth regulators are
to influence multiple flower bud formation.
The rate of flower bud development was increased by
two weeks of 37°F. storage and either two sprays of 200 ppm
TIBA or single sprays of 160, 400 or 1,000 ppm TIBA, or by
three weeks of 45°F. storage and a single spray of 1,000
ppm IAA. Rate of flower bud development was increased by two sprays of 200 ppm TIBA and one spray of 1,000 ppm
gibberellic acid (GA).
Flower bud dormancy was removed by foliar sprays of
900 ppm GAk with no cold storage or two weeks of 37°F. Four
weeks of 37°F. storage was effective without GAk and six
weeks of 37°F. storage gave no increase over four weeks of
storage. Concentrations of GAk lower than 900 ppm were
ineffective. GAk was effective whether applied before or
after two weeks of 37°F. storage.
Naphthalene acetic acid in concentrations of 9 ppm
or greater inhibited the rate of flower bud development.
Apical dominance was removed by 800 ppm or more of
TIBA.
The wheat coleoptile bioassay indicated that a growth
inhibitor in the flower buds was removed by three or more
weeks of 37°F. storage and three sprays of 1,000 ppm GAk.
The promoter was not in vegetative buds and could not be
considered to be IAA, GA or GAk.