Comparative lipid peroxidation, antioxidant defense systems and proline content in roots of two rice cultivars differing in salt tolerance

The changes in the activity of antioxidant enzymes such as superoxide dismutase (SOD: EC 1.15.1.1), catalase (CAT: EC 1.11.1.6), peroxidase (POX: EC 1.11.1.7), ascorbate peroxidase (APOX: EC 1.11.1.11) and glutathione reductase (GR: EC 1.6.4.2), free proline content, and the rate of lipid peroxidation level in terms of malondialdehyde (MDA) in roots of two rice cultivars (cvs.) differing in salt tolerance were investigated. Plants were subjected to three salt treatments, 0, 60, and 120 mol m(-3) NaCl for 7 days. The results showed that activated oxygen species may play a role in cellular toxicity of NaCl and indicated differences in activation of antioxidant defense systems between the two evs. The roots of both cultivars showed a decrease in GR activity with increase in salinity. CAT and APOX activities increased with increasing salt stress in roots of salt-tolerant cultivar Pokkah but decreased and showed no change, respectively, in roots of IR-28 cultivar. POX activity decreased with increasing NaCl concentrations in salt-tolerant Pokkah but increased in IR-28. SOD activity showed no change in roots of both cultivars under increasing salinity. MDA level in the roots increased under salt stress in sensitive IR-28 but showed no change in Pokkah. IR-28 produced higher amount of proline under salt stress than in Pokkali. Increasing NaCl concentration caused a reduction in root fresh weight of Pokkah and root dry weight of IR-28. The results indicate that improved tolerance to salt stress in root tissues of rice plants may be accomplished by increased capacity of antioxidative system. (c) 2004 Elsevier B.V All rights reserved.