Salinity and copper-induced oxidative damage and changes in the antioxidative defence systems of Anabaena doliolum

This study provides first-hand information on the salinity and copper-induced oxidative damage and its protection in Anabaena doliolum by the antioxidant defence system. Oxidative damage measured in terms of lipid peroxidation, electrolyte leakage and H2O2 production was induced by different concentrations of NaCl and Cu2+. A greater electrolyte leakage by NaCl than Cu2+ supported the hypothesis of salinity being more injurious than copper. To explore the survival strategies of A. doliolum under NaCl and Cu stress, enzymatic antioxidant activities e.g. superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) and nonenzymatic antioxidant contents such as glutathione reduced (GSH), ascorbate, alpha-tocopherol, and carotenoid were measured. A general induction in SOD and APX activities as well as ascorbate and alpha-tocopherol contents was found under NaCl and Cu(2+)supercript stop stress. In contrast to this, an appreciable decline in GR activity, GSH pool and carotenoid content under Cu(2+)supercript stop and an increase under NaCl stress were observed. CAT activity was completely inhibited at high doses of NaCl but stimulated following Cu(2+)supercript stop treatment. The above results suggest the involvement of APX and CAT in the scavenging of H2O2 under Cu2+ stress. In contrast to this, only APX was involved in H2O2 scavenging under salt stress. Our postulate of Cu2+-mediated antagonism of salt stress can be explained by a conceivable reversion of Na+-induced disturbance of cellular homeostasis by redox active Cu2+.