Lipid peroxidation and antioxidative response in Arabidopsis thaliana exposed to cadmium and copper

Formation of lipid hydroperoxides, malondialdehyde (MDA) and hydroxyalkenals (HAEs), membrane damages and antioxidative response of plants expressed as changes in glutathione S-transferase activity (GST) and anthocyanin accumulation were studied in Arabidopsis thaliana (L.) Heynh cv. Columbia plants treated for 7 days with various concentrations: 5, 25, 50, 100 mu M Cd and Cu. Increased lipid hydroperoxide content was metal concentration-dependent. The level of MDA + HAE was elevated in Cd- and Cu- treated plants, but it was metal concentration-dependent under Cu stress. Electrolyte leakage measurements showed a larger membrane damage under Cu- than Cd- treatment. In Cu- stressed plants, GST activity was always enhanced in comparison with control, while in plants exposed to Cd it dropped slightly at lower metal concentrations; but at 100 mu M Cd it was even higher than in plants treated with the same Cu concentration. Anthocyanin accumulation was considerably higher under Cu than Cd stress. Both lipid peroxidation and antioxidative response was stronger in Cu- than Cd- treated Arabidopsis thaliana plants. Various mechanisms of defense against the lipid peroxidation products, depending on the metal type, are discussed.