Alterations in root lipid peroxidation and antioxidative responses in two rice cultivars under NaCl-salinity stress

The comparative alterations of short term NaCl stress and recovery on growth, water relations, ionic composition, lipid peroxidation and antioxidants in roots of two rice cultivars differing in salt tolerance were studied. Exposed for 24 h to increasing (50, 100 and 150 mmol l⁻¹) concentrations of NaCl, roots of 12D Oryza sativa L. cv. Lunishree and cv. Begunbitchi decreased in fresh weight, dry weight and relative water content. Increased Na⁺ and decreased K⁺ ion were determined at increasing NaCl concentrations. Both peroxide content and lipid peroxidation measured in terms of MDA level increased and the ratio was higher in Begunbitchi compared to Lunishree. Recovered roots showed lower peroxide and MDA content. Ascorbate and glutathione contents increased in the stressed and recovered roots of Lunishree, but decreased in Begunbitchi with increasing NaCl concentrations. Although SOD, CAT and GR activities decreased in the stressed roots, CAT activity also increased in recovered roots of both the cultivars. The POX activity increased in stressed and recovered roots of both Lunishree and Begunbitchi. Higher free radicals scavenging capacity and more efficient protection mechanism of Lunishree against salt stress, as revealed by the lower level of lipid peroxidation and improved plant water status as well as activities of some of the antioxidants, suggest that significant cultivar differences in response to salt stress in rice are closely related to differences in the activities of antioxidants and ion content. Another possible conclusion is that improved tolerance to salt stress may be accomplished by increased capacity of antioxidative system.