Differences in biochemical responses to cold stress in two contrasting varieties of rape seed (Brassica napus L.)

Changes in isozymes of peroxidase, catalase, superoxide dismutase, polyphenol oxidase, and esterase and activities of peroxidase and polyphenol oxidase in two annual Brassica varieties (AS-3 and CON, cold-tolerant and cold-sensitive, respectively) after 4℃ treatment were assayed. After the low temperature treatment, PAGE patterns of isozymes of peroxidase, catalase, superoxide dismutase, polyphenol oxidase, and esterase showed that the expressions and activities of these enzymes in the AS-3 variety were higher than the CON variety. Under normal and cold conditions, peroxidase and esterase activities of AS-3 were higher than those of CON. The relative freezing tolerance of these two cultivars was discussed.