Effects of Lead and Zinc on seed germination and seedling growth of Soybean (Glycine max L)

In this research, the effects of different concentrations of ZnCl2 (5, 10, 15, 20 µM) and PbCl2 (0.5, 2.5, 4.5, 6.5 µM) on Soybean were examined. The effects of ZnCl2 and PbCl2 on the percentage of germination and germination rate of seeds, longitudinal growth of roots and shoots of seedlings of Soybean and the activity of antioxidant enzymes were studied. The seeds were transferred to petril dishes containing filter paper after surface sterile. There were 4 repeat from each treatment and there were 6 seeds in each repeat. The results showed that Pb stress had no significant effect in the percentage of germination of seedlings, and increase in both Zn and Pb treatment caused increasing in germination rate, but, it caused significant decrease in the length of roots, shoots and seedlings. Zn stress caused significant decrease in the percentage of germination in the higher concentrations and decrease in the length of roots and shoots in all of concentrations. The activities of Catalase and Peroxidase (POX) enzymes had significant increase in the plants under treatment with Zn and Pb in all concentrations. Obtained results of this research indicated that in comparison with Zn, Soybean has more Tolerance to Pb. It seems that in short term stress of Zn and Pb, the plant decreases stress intensity with induction of fast response, but, in spite of definitions that exist for the tolerable plants of Zn and Pb, it doesnot seem to include Soybean from tolerable plants to these heavy metals.