Effect of Different NaCl Salinity on Antioxidant Enzyme Activity and Relative Water in Winter Canola ( Brassica. napus )

To evaluate the effect of different levels of salinity on antioxidant enzymes activity of leaves and plant physiological characteristics of canola as a marker of resistance to salinity, an experiment was conducted in greenhouse of Research Center of Agriculture and Natural resources in East Azarbaijan in 2009. Treatments included combinations of five different levels of salinity (0, 50, 100, 150, and 200 mM) and four cultivars of brassica included (Elite, Licord, SLM046 and Okapi). With increasing salinity, stomatal conductivity, transpiration and leaf relative water decreased in all cultivars. Effect of salt stress on antioxidant enzymes of leaves was significant, and changes in the amount of super oxided dismutase enzymes, catalase and glutathion reductase was observed. Enzyme activity in the period of growth increased and in plant maturity decreased. Comparison between canola cultivars showed the strong correlation between leaf relative water and enzyme super oxide dismutase activity. SLM046 showed the least changes in leaf relative water level and the highest enzyme activity and was resistant cultivar and Elite were the most sensitive cultivar to salinity.