effects of drought stress on the lipid peroxidation and antioxidant enzyme activities in two canola (brassica napus l.) cultivars

drought is one of the most important abiotic stresses affecting plant growth and development. in the present study, the changes in lipid peroxidation rate and antioxidant enzyme activities were determined at different concentrations of polyethylene glycol (peg) 6000 (0, 5, 10, and 15% (w/v)) for two canola cultivars (slm046 and hyola 308). in order to produce water deficit, 12 days old canola seedlings were treated with peg 6,000 in half strength hoagland solution for 24 hours. peg treatments increased the content of malondialdehyde (mda), a product of lipid peroxidation, in roots and shoots of both cultivars; but for hyola 308 cultivar, the rate of increase of mda was higher than slm046 cultivar. in addition, drought did not have any significant effect on mda content in roots of slm046 cultivar. on the other hand, water stress increased superoxide dismutase (sod), peroxidase (pod), catalase (cat) and ascorbate peroxidase (apx) antioxidant enzyme activities of both shoots and roots of the studied cultivars; but activity of these antioxidants in slm046 cultivar was obviously higher than in hyola 308 cultivar. these results showed a higher water stress tolerance for slm046 cultivar.