Response of bean to some heavy metals in sewage water

Seed germination and early growth of bean (Phaseolus vulgaris) seedlings were significantly reduced when irrigated with a mixture of Cu, Zn, Cd and Pb at concentrations of sewage water. Leaf content of photosynthetic pigments, carbohydrates, nucleic acids and total nitrogen also decreased. Cd and Pb significantly inhibited the activity of alpha and beta-amylases and protease enzymes during germination. Treatment of the mixture solution by precipitation, rice residue or EDTA decreased its retarding effect. The effect of precipitation was more pronounced. Whilst the lower concentration of Cu and Zn stimulated germination, growth and metabolism of bean seedling, the higher concentrations showed inhibitory effects. Even at very low concentrations of Cd and Pb germination, growth and metabolism of bean significantly decreased. Precipitation treatment alleviated the adverse effects of higher concentrations of Zn, Cu, Cd and Pb. Whilst rice residue and EDTA treatments slightly enhanced germination of seeds treated with high concentrations of Zn and Cu, they did not affect germination of seeds treated with Cd or Pb.