Photosynthetic characteristics and activity of antioxidant enzymes in salinity tolerant and sensitive rice cultivars

A study was conducted to determine the physiological and biochemical characteristics of salinity tolerant (CSR-13) and sensitive (MI-48) rice genotypes in comparison with Pokkali (salinity tolerant check). Twenty-five days old seedlings were transplanted in earthen pots with control and two levels of salinity stress (6.17 and 11.68 dS m⁻¹) treatments. Observations were recorded for rate of photosynthesis, chlorophyll content, relative water content, lipid peroxidation and activities of RuBP Carboxylase (RuBPC), superoxide dismutase (SOD) ascorbate peroxidase (APX) and catalase (CAT) enzymes at 30 and 60 days after transplanting. Rate of photosynthesis, RuBPC activity and chlorophyll content decreased marginally by salinity stress in CSR-13 and Pokkali but MI-48 showed greater reduction. Pokkali and CSR-13 maintained higher RWC under salt stress compared to salt sensitive MI-48. Membrane lipid peroxidation was higher in both CSR-13 and MI-48 genotypes. SOD and APX activities were highly induced under salt stress in Pokkali but CAT activity decreased. In CSR-13, induction of SOD, APX and CAT activities was higher than that of MI-48. The results indicate that maintenance of higher RWC and induction of SOD and APX activities under salt stress in CSR-13 contributed to its salt tolerant characteristics.