Abstract:Hydrophyte especially the submerged macrophytes are important primary producer and main contributor to the subprime productivity in the water ecosystem. Improper agriculture and industry practices have led to deteriorated water quality, and eutrophication is one of the most pressing problems. The quantity of many kinds of hydrophytes, especially submerged macrophytes, have declined and even disappeared in the world as a result. The submerged macrophytes segments keep germinating when eaten by fish and cut by boats. There is not enough information about the effect of water nitrogen concentration on the germination and growth of the submerged macrophytes. In this experiment, the fragments with 3 nodes of M. spicatum and C. demersum were used, the bud number, location of bud and biomass were investigated under five nitrogen levels in water: 0 (CK), 0.5 mg/L (N1), 2 mg/L (N2), 8 mg/L (N3) and 12 mg/L (N4). The results indicate that the tolerance to high N level is different with different submerged macrophytes. The shoot length and biomass of M. spicatum were largest when the N concentration was 0.5 mg/L and 2 mg/L respectively, those of C. demersum were largest when the N concentration was 8.0 mg/L and 2 mg/L respectively. The segment germination and growth of the submerged macrophytes would be restrained when the N concentration was higher than 2 mg/L.