Effects of NaCl salinity on seedling growth, senescence, catalase and protease activities in two wheat genotypes differing in salt tolerance

Changes in seedling growth, senescence, protease activities and possible involvement of hydrogen peroxide scavenging enzyme c.g., catalase. in relation to salt tolerance were investi-ated in two wheat genotypes differing in salt tolerance. The Mays old wheat seedlings were subjected to 5, 10 and 15dSm(-1) NaCl salinity for 6days. Data showed that salt-stress brought about a reduction of the growth and protein content, particularly at 15dSm(-1) NaCl salinity. Application of low salinity (5dSm(-1)) did not show marked effects, but under high NaCl stress growth was suppressed even in tolerant genotype. Overall good growth of wheat cultivar Lu-26 at seedling stage might be due to osmotic adjustment. Leaf senescence or decrease in leaf protein content was only observed at higher (15dSm(-1)) NaCl stress in salt sensitive wheat cultivar Pak-81. The magnitude of salt induced proteolysis was many folds higher in sensitive wheat genotype Pak-81 at 15dSm(-1) NaCl salinity. The prominent salt induced senescence in leaves of wheat cultivar Pak-81 was associated with hi-her salt sensitivity in terms of extensive proteolysis. Severe salt-stress resulted in an inhibition of the antioxidative enzyme catalase as revealed by spectrophotometric assay. Catalase activity was decreased at all salinity levels in both wheat cultivars signifying that high salinity generally reduced the catalase activity irrespective of wheat genotype. The results Suggest that cv. Lu-26, exhibits a better protection mechanism against salinity as indicated by lower salt induced proteolysis, higher biomass accumulation and protein content than the relatively sensitive cv. Pak-81.