Effects of Pb²⁺ stress on nitrogen metabolism and membrane lipid peroxidation in Aegiceras conrniculatum seedlings

The effect of Pb2+ stress on nitrogen metabolism and membrane lipid peroxidation in Aegiceras corniculatum seedlings was investigated.The activities of NADH-GOGAT and GS,soluble protein,and MDA content in the roots,the stems and the leaves of A.corniculatum seedlings,which were cultivated for 30 days in nutrient solution containing Pb2+,were analyzed.The results showed that the NADH-GOGAT activities in A.corniculatum seedling roots,stems,and leaves decreased under Pb2+ stress,while the contents of soluble proteins and MDA increased.The GS activities in the roots and stems decreased due to Pb2+ treatments with concentrations ranging from 0.1 to 2 mmol·L-1.GS activities in the leaves increased and was higher than that of the control.However,the activity was inhibited by Pb2+ at higher concentration of 2 mmol·L-1.Whether Pb2+ was added to the nutrient solution or not,the GS activity in the leaves was higher than those in the roots and stems.The GOGAT activity in the roots was higher than those in the leaves and stems.GS and NADH-GOGAT in roots were more sensitive to Pb2+ stress than those in stems and leaves.Thus,Pb2+ had the most effect on primary nitrogen metabolism in the root.It was also suggested that there was a negative correlation between the MDA content and the NADH-GOGAT or GS activity.