cold-induced changes of antioxidant enzymes activity and lipid peroxidation in two canola (brassica napus l.) cultivars

this study was conducted on two canola (brassica napus) cultivars, okapi a winter type and cold tolerant and rgs003 a spring type and cold sensitive. seedlings were grown in an environmentally controlled growth room with 16 h d-1 photoperiod at 22/16 °c (day/night, control). at the 4-leaf stage, half of pots were transferred to a cold growth room for 7 d at 10/3°c (day/night, cold treatment) and their leaves were harvested as required on 0, 2, 4 and 7 d as four sampling times. superoxide dismutase (sod), peroxidase (pod), catalase (cat), and ascorbate peroxidase (apx) activity and the amount of malondialdehyde (mda) in samples were assessed. analysis of variance showed that winter canola had more sod, cat and apx activity, lower amount of either mda or pod activities compared with the spring canola. this study indicated that antioxidant mechanisms caused more cold tolerance in the winter cultivar of canola compared with the spring cultivar.