Nickel toxicity induces oxidative damage in Zea mays roots

Seven day-old maize (Zea mays cv. LG 23/01) plants were treated for five days with 250 muM NiCl2. The relationship between nickel (Ni) toxicity and oxidative reactions were studied in roots during metal accumulation. Membrane lipid peroxidation enhanced only 6 h after metal treatment before roots revealed a decrease in growth. The activities of superoxide dismutase (SOD), EC 1.15.1.1, guaiacol peroxidase (GPX), EC 1.11.1.7, were unaffected by Ni stress. However, catalase (CAT), EC 1.11.1.6, activity was increased from 24 h after metal treatment. In the ascorbate gluthatione cycle, only two enzymes, the ascorbate peroxidase (APX), EC 1.11.1.11, and monodehydroascorbate reductase (MDHAR), EC 1.6.5.4, were stimulated, while the activities of dehydroascorbate reductase (DHAR), EC 1.8.5.1, and glutathione reductase (GR), EC 1.6.4.2, remained around the control values. The results suggest that oxidative disorder is part of the overall expression of Ni toxicity in roots of Zea mays and that enhanced lipid peroxidation could be a consequence of primary effects of Ni stress.