A Distinction between the Fast and Slow Responses to Abscisic Acid

Abstract

Data already in the literature show that closure of stomata of intact leaves by abscisic acid (ABA) occurs rapidly by the (+) enantiomer, but the (-) is ineffective. Germination and growth are inhibited equally by (+)-ABA and (-)-ABA. The stomata in Commelina and Tropaeolum epidermal strips have now been shown to respond to (+)-ABA but not to (-)-ABA and protein synthesis in wheat embryos is inhibited by both. Thus the receptor sites for fast and slow responses to ABA have different molecular requirements and the fast reaction, therefore, cannot be a prerequisite for the slow.