Control of the Co2Responses of Stomata by Indol-3ylacetic Acid and Abscisic Acid

Abstract
Previous studies of stomatal behaviour on detached epidermis of Commelina communis L. have suggested that abscisic acid (ABA) and C02 act independently to cause stomatal closure. Evidence is presented here that if indol-3ylacetic acid (IAA) is added to the medium used for incubating the epidermis, an interaction between ABA and Co2 becomes apparent. Increasing concentrations of IAA reduce the ability of the stomata to respond to CO2, and ABA appears to antagonize this effect. Recognition of the role of IAA enables us to reconcile earlier conflicting reports concerning the interdependence of effects of ABA and Co2on stomata.