Effect of cadmium on nitrogen metabolism and relative enzymes activity in Solanum nigrum L seedlings

Nitrogen metabolism in Solanum nigrum L seedlings under cadmium(Cd)stress was investigated by nutrient solution culture method.The results showed that NO3--N and soluble protein contents,NR and GS activities in the leaves and roots increased firstly and decreased with increasing Cd concentration in the solutions,and decreased along with treatment time.And,soluble protein contents in the roots decreased with more extent.After 8 d of Cd exposure(25μm),NO3--N contents and NR activities in the leaves of S.nigrum reached peak values,but root NO3--N contents reached maximum after 8 d of 50μm Cd exposure,and leaf NO3--N were more sensitive to root.However,NH4 +-N contents in the leaves of S.nigrum increased with increasing Cd concentration and along with treatment time,and reached maximum after 16 d of 100μm Cd exposure,which suggested significant NH4 +-N accumulation in the leaves of S.nigrum subjected to Cd stress.Furthermore,GDH activities in the leaves and roots increased with increasing Cd concentration and along with exposure time,and reached peak values after 16 d of 100μm Cd exposure.