Abstract:The changes and mechanism of membrane lipids in the broad bean leaves exposed to 0(CK)、8.82kJ/m 2(T 1) and 12.6kJ/m 2(T 2) of UV-B radiation were observed respectively.The results showed that the contents of malonaldehyde (MDA) and H 2O 2 were increased,and that of index of unsaturated fatty acid (IUFA) was decreased,lipoxygenase (LOX) activity was enhanced and superoxide dismutase (SOD) activity was slightly changed after UV-B radiation treatment.The diamine putrescine (Put),the polyamine spermidine ...