Abstract
Membrane-bound Mg++-activated ATPase activity in epidermal strips from tobacco leaves (Nicotiana tabacum L. Samsun NN) was stimulated by abscisic acid (ABA) when the strips were floated on ABA solution in light or in darkness. The optimum ABA concentrations in light and in darkness were 10−5 M and 10−6 M, respectively. Carbonyl cyanide m-chlorophenylhydrazone (CCCP) and N, N′-dicyclohexylcarbodiimide (DCCD) completely blocked the basal level membrane-bound epidermal ATPase activity. ABAinduced membrane-bound epidermal ATPase activity was completely inhibited by CCCP, but only partly by DCCD. H+-influx into epidermal strips on a solution in light was lower than that in darkness. ABA stimulated H+-influx into epidermal strips in light and in darkness. CCCP suppressed basal level H+-influx, whereas DCCD did not. CCCP also suppressed ABA-induced H+-influx, whereas DCCD did not. Interaction between H+-influx and membranebound epidermal ATPase activity is discussed.