中文摘要：

为了解不同沉水植物对春季低水位的生理响应，在2014年春季开展为期3个月的控制实验，研究不同程度的春季低水位，包括极低水位（水深18cm）、较低水位（36cm）和低水位（54cm）对3种乡土沉水植物微齿眼子菜、穗花狐尾藻和菹草的最大光化学量子产量（Fv/Fm）、总叶绿素含量和可溶性糖含量的影响，并与外来种伊乐藻作对比。结果显示，随着水位的降低，微齿眼子菜、菹草和伊乐藻R／‰显著升高，而穗花狐尾藻的只，R无显著变化；在3种水位下伊乐藻的Fv／Fm都明显高于其他3种植物。微齿眼子菜和菹草总叶绿素含量也随着水位降低有升高趋势，而穗花狐尾藻和伊乐藻的总叶绿素含量随水位没有显著变化。所有水位下微齿眼子菜总叶绿素含量最高，穗花狐尾藻最低，菹草只在低水位下显著低于伊乐藻。微齿眼子菜、菹草和伊乐藻的可溶性糖含量随着水位的降低而下降，穗花狐尾藻的可溶性糖含量随着水位的降低有升高趋势。在低水位和较低水位下穗花狐尾藻和菹草的可溶性糖含量分别是所有植物中的最小和最大，但在极低水位下4种沉水植物的可溶性糖含量无明显差异。以上结果表明，春季极低水位对微齿眼子菜、伊乐藻和菹草不产生胁迫，但对穗花狐尾藻产生了胁迫；伊乐藻潜在光合能力强于乡土种，在春季浅水区具备较强的入侵性。

英文摘要：

To study effects of spring low water level on physiology （such as Fv/Fm, total chlorophyll content and soluble sugar） of different submerged macrophytes, three shallow water levels （18 cm, 36 cm and 54 cm） were treated with three native submerged plants Potamogeton maackianus, Myriophyllum spicatum and P. crispus, and an alien species Elodea nuttallii The results showed that decreasing water levels increased the Fv/Fm ofP. maackianus, P. crispus and E. nuttallii but not on M. spicatum. Fv/Fm orE. nuttallii was significantly higher than that of other three native species at all water levels. The total chlorophyll content ofP. maackianus and P. crispus increased with decreasing water levels, while that of M. spicatum and E. nuttallii showed no significant change. The value of chlorophyll content of P. maackianus and M. spicatum was the highest and lowest at all water levels, respectively. The content of total chloro- phyll ofP. crispus was significant lower than that ofE. nuttallii at 54 cm water depth, but other species had no signifi- cant difference. The soluble sugar ofP. maackianus, P. crispus and E. nuttallii decreased with decreasing water level, while that ofM. spicatum increased. The soluble sugar ofM. spicatum was the highest and P. crispus was the lowest at both 54 cm and 36 cm depth. However, no significant differences of soluble sugar among four species were found at 18 cm water depth. The results suggest that extremely low water level had stressful impacts on M. spicatum but not on P. maackianus, P. crispus and E. nuttallii, and that the higher potential photosynthesis orE. nuttallii compared with native species would aid its invasive risk in shallow water in spring.