Analysis of growth, carbohydrate and photosynthetic characteristics of Vallisneria natans (Lour.) Hara induced by a change in water depth

The effects of water depth on the growth, carbohydrates and photosynthetic response of Vallisneria natans (Lour.) Ham were studied using a five-month (June to October) mesocosm experiment to explore the plant ecological adaptability of different water depths by examining the morphological index, relative growth rate (RGR) and contents of non-structural carbohydrates (soluble and reducing sugars, starch), the maximum photosynthetic efficiency (F-v/F-m) and maximum electron transport rate (rETR(max)) in the plants. The results show that the shoot length, and ramet number increased significantly during the studied period, and the shoot number progressively increased from June to October, except at a 45 cm water depth. The root biomass, root length, root diameter, leaf width and RGR were the lowest in the most shallow (45 cm) water. The content of non-structural carbohydrates in the shoots of V.natans were significantly affected by the water depth,which was positively correlated with starch and total biomass, but negatively correlated with the soluble sugar, positive correlations were also observed between starch and the total biomass. The parameters F-v/F-m and rETR(max) of V. natans show dynamic changes with plant growth and development in terms of pigment characteristics. Based on the analysis, the water depth had an important effect on plant growth, carbohydrates and photosynthetic characteristics