Abstract:To understand the influence of interspecific relationships on community structure of submerged plants, the interaction of Vallisneria natans with Hydrilla verticillata and Myriophyllum spicatum was studied in the middle and lower reaches of the Yangtze River with different combinations of species under different light levels (20% and 50% nature light). The results showed that the biomass, height and leaf number of V. natans co-cultured with M. spicatum had not significant changes under low light intensity. The biomass of root and root/leaf of V. natans decreased with co-cultured ratio of M. spicatum increasing. Under high light intensity, the biomass and leaf biomass of V. natans increased with co-cultured ratio of M. spicatum increasing, while the height, root length and leaf number of V. natans had not change. There were no significant differences in height, root length and leaf number of V. natans between co-cultured with H. verticillate and M. spicatum, while biomass and leaf biomass of V. natans co-cultured with M. spicatum were lower than those co-cultured with H. verticillate. Therefore, both the species composition and co-cultured ratio could affect the interaction relationships between V. natans and other species, and then affect the community dynamics of submerged vegetation.