Interaction of Ethylene and Auxin in the Regulation of Hook Growth II. The Role for Ethylene in Different Growing Regions of the Hypocotyl Hook of Phaseolus vulgaris

Summary In different growing regions of the hypocotyl hook of Phaseolus vulgaris synthesis and levels of endogenous ethylene are asymmetrically distributed. Significant difference exists between waterstress- and IAA-induced ethylene formation from isolated hook segments, which fits to the former results (Schwark and Schierle. J. Plant Physiol. 140, 562–570, 1992) that also endogenous auxin levels are asymmetrically distributed in the hook. 1-N-Naphthylphthalamic acid (NPA), a specific inhibitor of polar transport of indole-acetic-acid (IAA) equalizes the asymmetric distribution of aminocyclopropane-1-carboxylic acid (ACC), the immediate precursor of ethylene. This result indicates, that transport of endogenous IAA is causally linked with the asymmetric synthesis of ethylene in the hook.