Shohreh Fahimirad - Department of Plant Breeding and Biotechnology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran
Ghasem Karimzadeh - Department of Plant Breeding and Biotechnology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran
Faezeh Ghanati - Department of Plant Biology, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran

This study was conducted on two canola (Brassica napus) cultivars, Okapi a winter type and cold tolerant and Rgs۰۰۳ a spring type and cold sensitive. Seedlings were grown in an environmentally controlled growth room with ۱۶ h d-۱ photoperiod at ۲۲/۱۶ °C (day/night, control). At the ۴-leaf stage, half of pots were transferred to a cold growth room for ۷ d at ۱۰/۳°C (day/night, cold treatment) and their leaves were harvested as required on ۰, ۲, ۴ and ۷ 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.

Antioxidant enzymes (APX, CAT, POD, SOD), Canola, Cold Stress, Lipid peroxidation