Effect of freezing stress on the membrane system of the open-field winter cabbage

Freezing resistance of 4 cabbages varieties was studied under open-field winter growth seasons． The results show that the electrolyte leakage and content of ma1ondia1dehyde(MDA)in cabbage leaves increase as temperature declines，especially the electrolyte leakage in “8398”and “8132”declines by 50％ in January，and membrane system is damaged seriously．The activity of superoxide dismutase(SOD)of“8398”，“8132”and“Jingfeng No．1”declines quickly under freezing temperature conditions．The peroxides(POD) activity increases as temperature declines under freezing stress．But the electrolyte leakage and content of ma1ondia1dehyde(MDA)in“Donggua No．1”are lower than those of “8398”，“8132”and“Jingfeng No．1”．Under freezing stress in January，the activity of SOD and POD in“Donguan No．1”still remains higher．It is indicated that freeze-resistance of“Dongguan No．1” is strong．