[Effects of Cu2+ on nitrogen and phosphorus removal by ryegrass cultivated in eutrophic water body]

Solution culture experiment was carried out to investigate the effects on the removal efficiencies of N and P by perennial ryegrass (Lolium perenne L.) under the Cu stress and the ecological response of ryegrass to various dosages of Cu2+. The results indicated that the removal efficiencies of N and P decreased under all the intimidating conditions compared with the control tanks, which followed the second-rate equation. The removal efficiencies of N and P and the plant growth at low Cu2+ concentrations (< or = 0.2 mg/L) were higher than those at high Cu2+ concentration (> or = 0.5 mg/L), and the biomass (dry weight) was increased at low Cu2+ concentrations (< or = 0.2 mg/L) relative to control solution. In addition, the plant was able to remove Cu2+ in the eutrophic water simultaneously, and the removal efficiencies under the high Cu2+ concentrations were higher than those under low Cu2+ concentrations. Results show that the root was the main section for accumulating Cu2+ and the data of Cu2+ uptake by perennial ryegrass fitted Michaelis-Menten kinetics equation. Perennial ryegrass were sensitive to Cu2+ treatment. Root elongation was reduced in Cu2+ treatment solutions, but the numbers of new-growth roots increased compared with those cultivated in control solution.