Nitrogen Uptake by Tropical Freshwater Macrophytes

摘要

The kinetics of nitrogen uptake were examined for three species of aquatic macrophytes which are common on Guam. Nitrate-nitrogen and ammonium-nitrogen uptake by Pistia stratiotes were monitored in response to a wide range of substrate concentrations. First order kinetics of nitrate-nitrogen uptake were examined for Pistia stratiotes, Hydrilla verticillata and Microspora sp. Uptake rates were higher after twenty-four hours of exposure to the nitrate source than immediately after exposure. The rate of uptake of nitrate-nitrogen by P. stratiotes was greater in the light than in the dark. Nitrate uptake followed a pattern which could be described by the Michaelis-Menton expression. Rates of ammonium-nitrogen uptake were similar in the dark and in the light. Ammonium-nitrogen uptake response to substrate concentration appeared to be linear.