Physiological Reactions of Potamogeton malaianus to Different N and P Concentrations in the Growth Medium
不同N、P浓度条件下竹叶眼子菜的生理反应

The soluble sugar contents, biomass and the activities of superoxide dismutase (SOD), peroxidase (POD) and ATPase of %Potamogeton malaianus% cultured in media with different N and P concentrations corresponding to oligo-, meso-, ertro- and hypertrophic conditions respectively were analysed. %P. malaianus% in the control experiment (oligotrophic) had significantly higher soluble sugar content and biomass than those in other different N and P treatments. In general, the activities of SOD and ATPase increased first and decreased later during the experiment, while that of POD showed a contrary pattern. SOD activities increased in the first week while POD activities decreased in the first two weeks, and plants from the control experiment had the smallest changes of activities. The activities of chloroplast and mitochondria Mg 2+-ATPase showed rising patterns during the first three and two weeks respectively, and plants from the control experiment had lower activities, while mitochondria Mg 2+-ATPase showed the highest activities in the third week. Both Ca 2+-ATPase activities of chloroplast and mitochondria increased in the first two weeks. The plants from the hypertrophic condition had the highest activities, and the activities increased with increased N and P concentrations in general. The results indicated that %P. malaianus% was more preferable to oligo- and mesotrophic waters, the raised N and P concentrations were a stress to %P. malaianus%, and could affect its physiological functions and restrain its growth. Although %P. malaianus% could resist the changes of N and P concentrations to some extent, its tolerance gradually weakened as time went on.