Full Length Research Paper

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

Chao Wang^1,2*, Xue Yan¹, Pei-fang Wang^1,2 and Chun-mei Chen²

¹Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, 210098, P. R. China.

²College of environmental science and engineering, HoHai University, Nanjing, 210098 P. R. China.

*Corresponding author. E-Mail: cwang@hhu.edu.cn. Tel: + 86 25 83787330. Fax: + 86 25 83787330.

Accepted 29 July, 2008

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 V_max and K_m of P were between 0.29 and 0.88 µmolg^-1fwh^-1 and 12 and 5.7 µmol L^-1, respectively, and that they varied with different plant species. V. spiralis had the greatest V_max and the smallest K_m. 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.

Key words: aquatic plants, kinetics, V_max, K_m, interaction, peroxidase, nitrate reductase, mechanisms.