Responses of three submersed macrophytes to total nitrogen supply

In order to study the responses of submersed macrophytes to different total nitrogen (TN) supplies and provide scientific recommendations for pioneer species to be used in the restoration of an eutrophic lake, three common submersed macrophytes (Hydrilla verticillata, Vallisneria natans and Potamogeton malaianus) distributed in the lakes of China were cultivated for 45 days in 1/40 strength Hoagland nutrient solution at different TN concentrations (added as NH4NO3). TN concentrations tested were 2, 4, 8 and 16 mg·L-1. The results showed that all the plants grew well over the whole range of TN supplied. Tiller number and shoot height were positively correlated to TN concentrations, while root length was negatively correlated. P. malaianus had the largest tiller number, shoot height and root length. In general, the biomass increased with increasing TN concentration, and the order of biomass increase was P. malaianus V. natans H. verticillata. Therefore, P. malaianus is an ideal pioneer species in the restoration of eutrophic lakes.