M. Mirzaee - Department of Plant Breeding and Biotechnology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran.
A. Moieni - Department of Plant Breeding and Biotechnology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran.
F. Ghanati - Department of Plant Breeding and Biotechnology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran.

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) ۶۰۰۰ (۰, ۵, ۱۰, and ۱۵% (w/v)) for two canola cultivars (SLM۰۴۶ and Hyola ۳۰۸). In order to produce water deficit, ۱۲ days old canola seedlings were treated with PEG ۶,۰۰۰ in half strength Hoagland solution for ۲۴ hours. PEG treatments increased the content of Malondialdehyde (MDA), a product of lipid peroxidation, in roots and shoots of both cultivars; but for Hyola ۳۰۸ cultivar, the rate of increase of MDA was higher than SLM۰۴۶ cultivar. In addition, drought did not have any significant effect on MDA content in roots of SLM۰۴۶ 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 SLM۰۴۶ cultivar was obviously higher than in Hyola ۳۰۸ cultivar. These results showed a higher water stress tolerance for SLM۰۴۶ cultivar.

Antioxidant, MDA, Osmotic stress, PEG ۶۰۰۰