INFLUENCE OF ABSCISIC-ACID AND TRANS CINNAMIC ACID ON SENESCENCE OF DETACHED TROPAEOLUM-MAJUS LEAVES IN RELATION TO STOMATAL MOVEMENTS

The influence of abscisic acid (ABA) and t cinnamic acid, individually and in combination, on senescence of excised nasturtium (Tropaeolum majus) leaves as related to stomatal movements has been studied. ABA (10(-5) M) induced an acceleration of chlorophyll loss in dark that was accompanied by an increase in stomatal diffusive resistance (SDR) of leaves. Trans-cinnamic acid (tCA) prevented the ABA-induced loss of chlorophyll and there was a proportionate decrease in SDR. When applied alone tCA, in general, delayed the chlorophyll loss SDR being slightly lower at 10(-5) M than in control. tCA treatment resulted in a massive release of potassium ions from senescing leaves. Significance of the findings is discussed.