Abstract: Submerged macrophytes are important primary producers in shallow lakes, with water depth and sediment type as the key factors affecting their growth. Vallisneria natans is a common submerged macrophyte in shallow lakes in the middle and lower reaches of the Yangtze River. The effects of water depth and sediment type on the growth of V. natanshave been reported, but the physiological traits of V. natans leaves are seldom examined. In this study, two sediment types (sand and mud) were used to plant V. natans at three water depths (40, 120, and 200 cm) to explore the ecological and physiological adaptation strategies of V. natans. The results showed that V. natansadapted to shallow water (40 cm) and deep water (200 cm) by changing plant height, ramet number, and leaf number, increasing antioxidant enzyme activity, and reducing chlorophyll concentration. V. natanshad low antioxidant enzyme activity but high chlorophyll concentration at the medium water depth (120 cm). Sediment types affected the growth of V. natans. The height, number of leaves, and ramets of V. natans were generally higher in the mud than in the sand. The chlorophyll concentration of V. natansin the mud at a water depth of 40 cm was higher than that in the sand, while the chlorophyll concentration of V. natans in the sand was higher at water depths of 120 and 200 cm. Sediment type did not change the antioxidant enzyme activity of V. natans. Our results indicated that 40-120 cm water depth and mud sediment were more conducive to the growth of V. natans than the other conditions. V. natansused different physiological and ecological adaptation strategies under different water depths and sediment conditions, which are of great significance to the restoration of submerged vegetation and the construction of freshwater ecosystem.

Key words: submerged macrophyte, environmental factor, morphological trait, antioxidant enzyme, chlorophyll.