Differences in antioxidant activity in response to salinity stress in tolerant and susceptible wheat genotypes

Effects of long-term sodium chloride salinity (100 and 200 mM NaCl; ECe = 6.85 and 12.3 dS m^–1) were studied in tolerant (Kharchia 65, KRL 19) and susceptible (HD 2009, HD 2687) wheat genotypes. NaCl decreased relative water content (RWC), chlorophyll content (Chl), membrane stability index (MSI) and ascorbic acid (AA) content, and increased the contents of hydrogen peroxide, thiobarbituric acid reactive substances (TBARS), and activities of superoxide dismutase (SOD), ascorbate peroxidase (APOX) and glutathione reductase (GR). Kharchia 65 showed lowest decline in RWC, Chl, MSI and AA content, lowest increase in H₂O₂ and TBARS contents and higher increase in SOD and its isozymes, APOX and GR, while HD2687 showed the highest decrease in AA content, highest increase in H₂O₂ and TBARS contents and smallest increase in activities of antioxidant enzymes. KRL 19 and HD 2009 showed intermediate response both in terms of oxidative stress and antioxidant activity.