Studies of the Inhibition of Stomatal Opening by Naphth-1-ylacetic Acid and Abscisic Acid

Evidence is presented which confirms the inhibitory action ofthe synthetic auxin, NAA, on stomatal opening. In contrast tothe natural auxin IAA, NAA exerts effects which, in some respects,resemble those of ABA. The mode of action of NAA on the guardcells is, however, thought to be different from that of ABA.When NAA and ABA are applied together, their combined actionresults in a greater reduction in stomatal aperture than wouldbe predicted from their separate effects. Key words: NAA, ABA, IAA Stomata, Commelina