Changes in Growth and Antioxidant Enzymes in Bean (Phaseolus vulgaris L.) Under Heavy Metal Stress

The impact of different concentrations of copper sulphate, lead nitrate and mercuric chloride [12, 25, 37.4 mg/kg for (CuSO4 center dot 5H(2)O), 30, 60, 80 mg/kg for [Pb(NO3)(2)] and 8, 16, 24 mg/kg for (HgCl2)] on morphological parameters (root and shoot length, fresh and dry weight and water content) and antioxidant enzymes (catalase, poly-phenol oxidase and peroxidise) were investigated in bean seedlings {Phaseolus vulgaris cv. Giza 6) grown in peat moss. Our findings show that all morphological parameters decreased as concentration of metals was increased as compared to control plants. The present results showed that the increment of copper sulphate and lead nitrate concentration in the soil was associated with the enhancement in catalase activity. CAT activity increased in coincidence with low concentrations of Hgcl2 while decreased under higher level. Activity of both Peroxidise (POX) and polyphenol oxidase (PPO) stimulated with increasing doses of the metals studied. Based on these results it is concluded that the strongest effect on growth and antioxidant enzymes was found in bean plants exposed to mercury, followed by the sequence Cu++> Pb++.