Effects of low potassium on membrane lipid peroxidation and protective enzyme activity of soybean leaves.

Membrane lipid peroxidation and protective enzyme activities under different potassium (K) levels were investigated in pot trails using high K-efficient soybean cultivar Shennong 6 and low K-efficient Tie 95068-5.Results indicated that,when the K concentration decreased,both relative conductivity and MDA (malondialdehyde) content were increased with different reactions between the 2 materials.The increases of Shennong 6 were much lower than those of Tie 95068-5.SOD activities declined when K concentration increased.Low K supply activated the protective enzymes at each observed stage.CAT and POD activities of the two materials increased initially and then decreased.The activity of CAT reached peak in blooming stage (R2),while that of POD reached peak at seeding stage (R6) of Shennong 6 and podding stage (R4) of Tie 95068-5,respectively.Compared to Tie 95068-5,Shennong 6 had greater activities of SOD,CAT and POD at all growth stages.This suggested a direct correlation between soybean K-efficiency and its protective enzyme activities of active oxygen clearing.