Effect of abscisic acid on membrane-bound epidermal ATPase from tobacco leaves

Membrane-bound Mg⁺⁺-activated ATPase activity in epidermal stripsfrom tobacco leaves (Nicotiana tabacum L. Samsun NN) was stimulatedby abscisic acid (ABA) when the strips were floated on ABA solutionin light or in darkness. The optimum ABA concentrations in lightand 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 epidermalATPase activity. ABAinduced membrane-bound epidermal ATPaseactivity was completely inhibited by CCCP, but only partly byDCCD. H⁺-influx into epidermal strips on a solution in light was lowerthan that in darkness. ABA stimulated H⁺-influx into epidermalstrips in light and in darkness. CCCP suppressed basal levelH⁺-influx, whereas DCCD did not. CCCP also suppressed ABA-inducedH⁺-influx, whereas DCCD did not. Interaction between H⁺-influxand membranebound epidermal ATPase activity is discussed. (Received May 23, 1978; )