Abstract: In order to ameliorate the water quality of Taihu Lake, a eutrophic shallow lake, a special program was launched. One of the key tasks is to restore the submerged vegetation in the lake. Some of the submerged macrophyte species reestablished in the region of Lake Taihu have decomposed and died off, and dissolved oxygen in bottom water was low(1~2 mg/L) at the same time. An outdoor experiment was conducted in artificial ecosystem to illuminate the relationship between the growth of Vallisneria spiralis and the low dissolved oxygen of water. The treatment included two dissolved oxygen concentrations (low oxygen and high contrast oxygen) and two kinds of sediments. It is revealed that using bank sediment or sediment from central lake, low dissolved oxygen had no prominent effect on the growth of V. spiralis, but on the number and weight of tuber of the submersed plant. In low dissolved oxygen water, the root of V. spiralis growing in bank sediment became thin and their activity became weak. But, the root of the plant growing in centrallake sediment was not susceptive. It was proposed that other factors such as light play the key role on the growth of submerged plants in the lake and the effect of dissolved oxygen on aquatic macrophytes be a long time one.

Key words: low dissolved oxygen, Vallisneria spiralis, growth, sediment