Antitranspirants and the Regulation of Abscisic Acid Content

Abstract

The antitranspirants farnesol and phenylmercuric acetate increased abscisic acid (ABA) contents of spinach leaves by the same amount as wilting, and so this can account for stomatal closure. It is now proposed that leaf ABA contents are regulated by chloroplast permeability and a mechanism for this is described. ABA and its conjugate occur in the protoplasm of citrus fruit vesicle cells; considerably less is in the vacuolar sap.