Wheat is one of the main crops occupying a large area in the world and also in Iran. Salinity is one of the factors that decrease wheat growth and productivity. Therefore, to study the effects of different salinity levels, changes in lipid peroxidation, antioxidant enzyme activities [catalase (CAT), ascorbate peroxidase (APX) and guaiacol peroxidase (GPX)], hydrogen peroxide (H2O2), membrane stability index (MSI), relative water content (RWC), soluble sugars, sodium (Na+) and potassium (K+) ions in two wheat varieties (Hirmand and Karkheh) were investigated. Seedlings were subjected to 100 and 200 mM NaCl and hoagland’s solution as control for 20 days. Salinity stress increased GPX and CAT in both cultivars compared with control. At the same time, the APX enzyme increased in ‘Hirmand’, but had no significant change in ‘Karkheh’ compared with control. The amount of H2O2 in ‘Hirmand’ did not significantly change in the saline condition compared with control, but showed a significant increase in ‘Karkheh’. The amount of malondialdehyde (MDA) in both cultivars under saline conditions increased in comparison with control. However, the highest increase was related to ‘Karkheh’. The results also showed a decrease in MSI in both of the cultivars. RWC decreased significantly in ‘Karkheh’ while in ‘Hirmand’ there was no significant change. Soluble sugars in both cultivars increased. The results indicated an increase in Na+ in both cultivars. But K+ reduced in ‘Karkheh’ and did not change significantly in ‘Hirmand’. The K+/Na+ ratio also decreased in both cultivars. These findings possibly suggest that by inducing the activity of antioxidant enzymes, no decrease in RWC, and K+, low increase of Na+ and increasing the soluble sugars, ‘Hirmand’ has a better protection mechanism against salt-induced oxidative damage than ‘Karkheh’.
