PLANT PHYSIOLOGY , Vol 101, Issue 2 641-646, Copyright © 1993 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Involvement of Abscisic Acid in Ethylene-Induced Cotyledon Abscission in Cotton Seedlings
J. C. Suttle and J. F. Hultstrand
United States Department of Agriculture, Northern Crop Science Laboratory, P.O. Box 5677, State University Station, Fargo, North Dakota 58105
Cotton (Gossypium hirsutum L. cv LG102) seedlings raised from seeds exposed
to 100 [mu]M norflurazon (NFZ) during imbibition contained reduced levels
of free abscisic acid (ABA) and were visibly achlorophyllous. Exposure of
untreated cotton seedlings to ethylene concentrations >1 [mu]L/L for 24
h resulted in cotyledon abscission. In contrast, exposure of NFZ-treated
seedlings to concentrations of ethylene [less than or equal to]50 [mu]L/L
elicited no cotyledon abscission. Application of ABA, an ABA analog, or
jasmonic acid to NFZ-treated seedlings restored ethylene-induced
abscission. Isolated cotyledonary node explants prepared from NFZ-treated
seedlings exhibited an altered dose-response pattern of ethylene-induced
petiole abscission. Endogenous levels of free IAA were unaltered in
NFZ-treated seedlings. Ethylene treatment (50 [mu]L/L, 24 h) had no effect
on free indoleacetic acid (IAA) levels in either control or NFZ-treated
seedlings. Levels of conjugated (ester plus amide) IAA were substantially
increased in NFZ-treated seedlings regardless of ethylene treatment. These
results indicate that endogenous ABA plays an essential, but
physiologically undefined, role in ethylene-induced cotyledon abscission in
cotton.
