Investigation of effects of copper treatments under drought stress induced oxidative damage and antioxidant defence responses in heat- sensitive and heat -tolerant corn (Zea mays L.) plant

The present study was conducted to present the responses of drought-sensitive (Shemal) and drought-tolerant (71may69) maize cultivars under drought condition (20 % Polyethylene glycol, -0.40 MPa) and three different copper concentrations (0.5 mM, 1 mM, 1.5 mM CuSO4.5H2O) for 5 days to determine the antioxidant enzyme responses of copper treatment in maize leaves. Copper treatments alone did not change stomatal conductance, relative water content and growth rate, proline, hydrogen peroxide (H2O2), malondialdehyde (MDA) content decreased and abscisic acid (ABA) level according to control groups. Combined treatment (drought and copper) alleviated the damage of PEG- induced drought stress in maize leaves. Superoxide dismutase (SOD), catalase (CAT), glutatione reductase (GR), peroxidase (POX) activity increased and glutathione -S transferase (GST) activity decreased, while ascorbate peroxidase (APX) activity did not change under drought stress in the tolerant cultivar. SOD, CAT and APX decreased and GST, POX activities were increased while GR did not change in sensitive cultivar. Also SOD, APX and CAT activity increased by copper treatment alone in both cultivars. Otherwise combined treatment increased SOD, APX and CAT activity at all concentrations, but GR and GST activity increased only by (PEG+1.5 mM) treatment when compared with PEG treatment alone in sensitive ones. POX did not change in Shemal. As a result, exogenous copper alleviated drought stress, while it induced an oxidative damage by increasing antioxidant enzyme activities differently from drought tolerance.