effects of salinity stress on nucleic acid metabolism, antioxidants enzyme activity, chlorophyll fluorescence and osmotic adjustment in five canola genotypes

seedlings of five canola genotypes (hyola308, hyola401, hyola60, optlon50, and rgs003), were grown in hoagland nutrient solution containing s1=0, s2=100, s3=200 and s4=300 mm nacl in controlled environment. such antioxidant activities as catalase (cat), ascobrate peroxidase (apx) and guaiacol peroxidase (gpx), as well as osmolyte concentration (proline), chlorophyll fluorescence and some enzyme activities of nucleic acid metabolism were determined in the plants' shoots and roots 30 days after induction of salinity stress. results indicated that, application of stress significantly affected plant growth components such as fresh (fw) and dry weight (dw) in canola genotypes. among the genotypes, rgs003 experienced the highest reduction of fw and dw in the s3 treatment. by increasing nacl levels from 0 to 300 mm, the activity of two antioxidant enzymes (apx and cat) increased in shoot and root while gpx decreased in all the genotypes. the increase in salinity stress, increased proline concentration in both root and shoot tissues of canola genotypes. hyola401 genotype carried the maximum concentration of proline in root and shoot in s3 treatment. along with increased salinity stress in all the studied plants, salinity significantly increased the level of the total nucleic acid and the activity of dnase i in all the salinity treatments. moreover, at the s3 level, rgs003 carrying a maximum concentration of nucleolytic enzyme.