Specificity and reversibility of the rapid stomatal response to abscisic acid

Abstract
Closure of stomata caused by low (10-7M) concentrations of abscisic acid (ABA) is specific for cis-trans ABA, and is initiated within 5 minutes. Upon withdrawal of the hormone supply, reopening starts within 5 minutes. Gas analysis of leaves treated with ABA or DCMU allows one to distinguish effects on the stomatal apparatus from inhibition of photosynthesis and to conclude that ABA acts on stomata directly.