Analysis of growth response and tolerance index of Glycine max (L.) Merr. under hexavalent chromium stress

Background: Metal pollution has become one of the most serious environmental problems due to various human activities. It can damage or alter the biosphere reducing the agricultural productivity and can affect both animals and humans. Emission of various pollutants into the atmosphere has many harmful effects on plant growth. Rapid urbanization, unregulated industrialization, growing transport, metal plating and agricultural activities have created a problem of heavy metals contamination. Methods: A greenhouse experiment was conducted to determine the toxicity of chromium on Glycine max. Chromium concentration applied to G. max was managed as 0.5, 2.5, 5, 10, 25, 50 and 100 mg kg(-1) for experimental period of 90 days. The phytotoxic effect of chromium metal was analyzed by studying seed germination, seedling vigor index, root and shoot length, root and shoot fresh and dry weights, chlorophyll content and tolerance index. Results: The data presented in this study showed that chromium metal adversely affects the growth of G. max and significantly (p<0.05) reduces seed germination and growth. The toxic effect of chromium on the seeds increased with increasing the concentration of the metal. It was also found that high concentrations of chromium (50 and 100 mg kg(-1)) can completely inhibit the seed germination. Conclusion: The chromium metal is extremely toxic for seeds and young seedling of G. max at high concentrations. Moreover, G. max has little potential to counteract the deleterious effect of chromium metal in soil at aforementioned treatments. The results of the present study may help in better understanding of the mechanisms involved in pytoextraction.