GROWTH OF SEVEN SUBMERSED MACROPHYTES CULTURED ON FIVE SEDIMENT MIXTURES FROM THE LAKE ERHAI

In an outdoor 70d experiment, seven submersed macrophytes, Vallisneria natans, Hydrilla verticillata, Pota-mogeton maackianus, Potamogeton malaianus, Potamogeton lucens, Potamogeton perfoliatus and Myriophyllum spicatum were cultured on five sediment mixtures consisting of different proportions in lake sediment and local soil from the Lake Erhai, with aims to examine effects of sediment properties on the plant growth. At the end of the experiment, V. natans, P. malaianus and P. lucens grown on the sediment mixture of 50% deep-layer lake sediment and 50% local soil (C:31.59 mg/g; N:0.334 mg/g; P:0.095 mg/g), which had the highest shoot heights, and so did for H. verticillata, P. maackianus, P. perfoliatus and M. spicatum grown on the 100% deep-layer lake sediment (C:37.88 mg/g; N:0.803 mg/g; P:0.149 mg/g). On the 100% deep-layer lake sediment, V. natans, H. verticillata, P. maackianus, P. malaia-nus and P. lucens had the highest relative growth rate (RGR) and biomass production, and so did for P. perfoliatus and M. verticillatum grown on the 100% surface lake sediment (C:77.37 mg/g; N:5.691 mg/g; P:0.136 mg/g), and the sediment mixture of 50% surface lake sediment and 50% deep-layer lake sediment (C:49.27 mg/g; N:2.005 mg/g; P:0.131 mg/g) respectively. All the plant species did not grown well and got marginal biomass production on the 100% local soil (C:22.06 mg/g; N:0.327 mg/g; P:0.231 mg/g). The results revealed that the sediment mixtures with intermedium nutrients contents (C:31.59-49.27 mg/g; N:0.334-2.005 mg/g; P:0.095-0.131 mg/g) were most beneficial to growth of submersed macrophytes, instead of the sediments with extremely higher or lower nutrient contents.