Suppression of Stomatal Opening in Leaves Treated with Abscisic Acid

Abstract

Small doses of abscisic acid (approximately 0.02 μg cm-2 of leaf) applied to the leaf surface as a 10-4 M solution caused marked stomatal closure in Xanthium pennsylvanicum, and the effect persisted for up to 9 days after application. Similar effects were found when 10-4 M abscisic acid was supplied to detached tobacco leaves via their petioles. CO2-free air did not cause a reversal of the closure, and it was therefore concluded that the effect was not due simply to an increase in the intercellular CO2concentration; a more direct effect on the stomatal apparatus is suggested. It is considered that abscisic acid could play an endogenous role in the control of stomatal aperture, and that this, and/or related substances, might be more useful as ‘anti-transpirants’ than the phytotoxic substances currently employed for this purpose.