SALT-INDUCED VARIATION OF INORGANIC NUTRIENTS, ANTIOXIDANT ENZYMES, LEAF PROLINE AND MALONDIALDEHYDE (MDA) CONTENT IN CANOLA (BRASSICA NAPUS L.)

Present experiment was performed to determine the effect of salinity stress on canola (Brassica napus L.) using the parameters of inorganic nutrients, malondialdehyde (MDA) and leaf proline content and the activity of antioxidant enzymes. Four canola cultivars viz., Oscar, Ac Excel, Cyclone and Dunkled and two levels of salt (0 mmol/L NaCl, 120 mmol/L NaCl) were used. Root fresh and dry weight of four canola cultivars markedly declined due to salinity stress. Salt stress significantly increased leaf proline content in four canola cultivars and higher values were recorded in cultivar Dunkled and Ac Excel than those in Cyclone and Oscar. Salt stress significantly enhanced antioxidant enzyme activities including SOD, POD and CAT in all canola cultivars. SOD showed highest value in Cyclone and Dunkled, POD in Ac Excel, Cyclone and Dunkled while CAT in Ac Excel and Dunkled. Malondialdehyde (MDA) showed variable response in all canola cultivars under saline conditions. Shoot and root (Na+, Cl-, K+, and Ca2+) were significantly affected under salt regimes. Salt stress increased Na+ content in root and shoot in canola cultivars. High shoot Na+ was found in Oscar and Cyclone, root Na+ in Oscar, Ac Excel and Cyclone. Value of K+ and Ca2+ in shoot and root was markedly reduced under saline conditions. It is concluded that high salt tolerance of canola cultivar "Dunkled" could be accredited due to exclusion of Na+ and accumulation of K+ ions, enhanced leaf free proline content and also antioxidant enzyme CAT activity.