Interactive Influence of N and P on their uptake by four different hydrophytes

Abstract

The uptake kinetics of nitrogen (N) and phosphorus (P) by hydrophytes can be influenced by the interaction between N and P. In this study, Pistia stratiotes (a floating plant), Eichhornia crassipes (a
floating plant), Vallisneria spiralis (a submerged plant), and Cyperus papyrus (an emergent plant) were selected to measure the uptake kinetics of N and P. The results indicated that the values of Vmax and Km of P were between 0.29 and 0.88 ìmolg-1fwh-1 and 12 and 5.7 ìmol L-1, respectively, and that they varied with different plant species. V. spiralis had the greatest Vmax and the smallest Km. As for P. stratiotes, N and P uptake kinetics were influenced by interaction of N and P. Moreover, it was also found that peroxidase (POD) activity and nitrate reductase activity (NRA) were influenced. The NRA of P. stratiotes was found to increase first and then decrease with increasing P content, while the P content affected peroxidase (POD) activity in P. stratiotes. Both NRA and POD could indicate the rates and abilities of nutrient removal of aquatic plants.