Effect of Sediment Redox on Physiological Ecology and Heavy Metal Uptake of Vallisneria natans

Degradation of organic matter in sediments of water body would deplete oxygen in the sediment, resulting in an anoxic condition therein, which in turn affects growth of submerged macrophytes and their uptake of certain heavy metals. Under the condition of simulated anoxic sediment, Vallisneria natans was grown and monitored for stress of heavy metal pollutants in the sediment and contents of the elements in the plant tissues. Results show that the anoxic condition of the heavy metals polluted sediment lowered chlorophyll content, POD activity and soluble protein content in V. natans, raised soluble sugar content, promoted growth of the plant in biomass when the anoxic condition was kept at a certain level, and increased the uptake of Cr, Ni, Pb and Cu up to 2.2, 5.4, 3.0 and 1.5 times as high as in the tissues of the plant under the control condition, while the uptake of Zn in the shoot and root was suppressed and lowered to 64% and 81% of that, respectively, in the control. All the findings demonstrate that the redox condition of sediments significantly affects the physiology of V. natans and heavy metals uptake of the plant.