Physiological Response Of Lolium Multiflorum And Pennisetum Americanum To Copper And Zinc Treatment And Purification Of Polluted Water With The Grasses

Copper and Zinc are not only essential micronutrients for organisms, but also pollution elements in environment. They have been the widespread heavy metal polluters caused water and soil pollution in China. Forage production is the important part of agricultural production and feed resource for herbivorous animals. Toxicological effects of copper and zinc pollution on forages would be diverted to herbivorous animals. Grasses have wild adaptation and can be applied to phytoremediation of polluted environment by heavy metal. As the grasses that have accumulation capacity for copper and zinc were used to remedy polluted environment, harmless forages would be produced.Lolium multiflorum and Pennisetum americanum are respectively important cool season and warm season grasses in forage production. Both of them have many advantages, for example wild adaptation, fast growth, great biomass, flourish roots and good quality. In this experiment, effects of Cu2+ and Zn2+ stress on seed germination of the two grasses were studied. The physiological response of seedlings to Cu2+ and Zn2+ stress and purification and accumulation of copper and zinc in polluted water with seedlings were studied through hydroponic experiments.The results showed that seed germination was not affected adversely when Cu2+ and Zn2+ concentrations were lower. High concentration Cu2+ and Zn2"1" had inhibition effect on seed germination in a short time. But the germination rates of seeds were not affected significantly at last. Cu2+ and Zn2+ stress had significant inhibition effect on root elongation. The relationship between inhibition rate of root elongation and Cu2+ and Zn2+ concentration could be estimated by logarithmic curves, coefficients reach the most significant level. Toxicity of heavy metal in the environment could be forecasted by the inhibition effect on root elongation. Toxicity of Cu2+ was heavier than Zn2+. Root elongation of L. multiflorum was more sensitive to copper and zinc pollution than that of P. americanum.Growth of seedlings of two grasses was inhibited under Cu2+ and Zn2+ stress ofdifferent concentration. Their biomass decreased. With increased Cu and Zn concentration, leaf area, chlorophyll content and root activities reduced. Furthermore, the activate oxygen metabolism system was destroyed and the balance of activities of SOD, POD and CAT was broken. That induced peroxidation of cell membrane lipid, MDA content and the electrolyte leakage of the cell membrane increased.With the increase of Cu2+ and Zn2+ concentration, copper and zinc content in the roots and leaves of two grasses increased. But there were no significant linear relationship between them. Copper and zinc content in the roots were higher than in the leaves. Seedlings could remove copper and zinc from water. The removing rule was fast sorption and slow absorption process.According to the results mentioned above, two grasses adapted to purify polluted water in which Cu2+ concentration was less than 2.5mg/L and Zn2+ concentration was less than 10mg/L, at the same time forages could be used to animal production.