ANTIOXIDANT DEFENSE IN THE LEAVES OF MAIZE PLANTS (Zea mays L.) UNDER CADMIUM AND PARAQUAT STRESS

Zea mays L. plants exposed to 25, 50 and 100 mu M Cd and paraquat (PQ) - 25 mu M alone and in combination (25 mu M Cd + 25 mu M paraquat) were analysed with reference to metal and herbicide effects oil the antioxidant enzymes. Maize plants responded differently to Cd and PQ with enhanced activities of most of the enzymes monitored in the present study. Cd and PQ induced enhancement in superoxide dismutase (SOD) activity which was more pronounced at 50 and 100 mu M Cd and 25 mu M PQ. The same trend was observed in the activity of catalase (CAT) in (lie leaves treated with 50 and 100 M Cd and 25 mu M paraquat. The increase of glutathione reductase (GR) activity, was more distinct at 100 mu M Cd than at 25 and 50 mu M and it was higher in the leaves after combined treatment. Glutathione peroxidase (GPER) activity decreased in the leaves after Cd and PQ treatment and slightly increased after combination. Increased activities of antioxidative enzymes in Cd and PQ treated plants suggested that they have some additive function in the mechanism of metal tolerance in maize plants.