Studies on the Relation between Molecular Structure and Physiological Activity of Plant Growth-Regulators. I. Abscission-Inducing Activity

Abstract

1. Excision of the terminal bud of the seedling of Phaseolus vulgaris var. Black Valentine results in the formation of an abscission layer in the subjacent internode. A similar result can be induced by application of various chemicals to the intact bud. 2. The most effective compounds found, in tests of more than six hundred substances, were certain 2,3,5-trihalogenated benzoic acids; a large number of other compounds of considerable structural diversity also exhibit activity. 3. The abscission-inducing activity of 2,3,5-triiodobenzoic acid (TIBA) can be counteracted by concurrent application of a number of compounds including 3-indoleacetic acid and 1-naphthalenacetic acid.