IMPLICATION OF HYDROGEN PEROXIDE – ASCORBATE SYSTEM ON MEMBRANE PERMEABILITY OF WATER STRESSED <i>VIGNA</i> SEEDLINGS

Abstract

S ummary When seedlings of Vigna catjang were subjected to increasing magnitudes of water stress (−0.5, −10 and −1.5 MPa) the induced changes in leaf water potential (LWP), were accompanied by increases in proline content, tissue permeability, H 2 O 2 content and ascorbic acid oxidase activity, and decreases in catalase activity and ascorbic acid content. Pretreatment with L‐cysteine (10 −3 M), reduced glutathione (10 −3 M) and abscisic acid (ABA, 10 −4 M) through the roots improved the water status of stressed seedlings maintained at – 10 MPa for 2 d, and decreased the tissue permeability, proline content, H 2 O 2 content and ascorbic acid oxidase activity, but increased the ascorbic acid content and catalase activity. Stressed seedlings from seeds pretreated with CaCl 2 (10 −2 M) behaved like plants treated with the reducing agents and ABA, and not like untreated stressed seedlings. The studies suggest that the maintenance of membrane integrity is of paramount importance, and that the hardening treatments might modulate the endogenous levels of H 2 O 2 and ascorbic acid in stressed seedlings which, in turn, might influence membrane integrity.