Comparison of protective enzyme activity in leaves of soybean at different yield levels

【Objective】The study was performed to explore changes of protective enzyme activities in leaves of soybean at different yield levels.The purpose was to provide some physiological basis for soybean breeding and high-yield cultivation.【Method】Nine soybean(Glycine max(L.) Merr.) cultivars were divided into three yield levels(low yield cultivars,high yield cultivars,middle yield cultivars) were planted under the same environmental condition.After podding stage,the superoxide dismutase(SOD) activities,catalase(CAT) activities,peoxidase(POD) activities,malondialdehyde(MDA) contents and cell membrane permeability were measured in soybean leaves.【Result】After podding stage,the activities of SOD,CAT and POD in leaves were the highest at high yield cultivars,then at middle yield cultivars and the lowest at low yield cultivars.The change tendency of those enzymes was consistent,which all reached maximum value at seedfilling-flourishing stage and then decreased.The activities of SOD,CAT and POD in leaves of high yield cultivars were significantly higher than that of low yield cultivars.The contents of MDA and cell membrane permeability in leaves were the highest at low yield cultivars,then at middle yield cultivars and the lowest at high yield cultivars after podding stage.Following the breeding proceeding,the contents of MDA and cell membrane permeability all showed rising tendency and reached maximum value at maturation stages,then the MDA contents and the cell membrane permeability of high yield cultivars were very significantly lower than those of low yield cultivars.【Conclusion】After podding stage,the ability in leaves of high yield cultivars to eliminate active oxygen was better and the degree of lipid peroxidation was low.The leaf of high yield cultivars senescence was delayed and the function of leaves extended,which make for dry matter accumulation at later stage and conduce to increase yields.