Effects Of Water Level Fluctuation On The Growth Of Aquatic Plants (An Experimental Ecological Study)

Possible adaptive mechanisms to water fluctuation of several dominant macrophytes in Liangzi Lake (Hubei Province, China) were investigated. The results are as follows:1. The adaptions of Myriophyllum spicatum and Potamogeton maackianus to flooding. With the increasing of water level, M. spicatum allocated less biomass to root and stem but more to leaf, and plant height increased. P. maackianus allocated more biomass to stem but less to root and leaf, while shoot length increased first and then decreased with depth.2. The effects of water level fluctuation on morphological characteristics, growth and biomass allocation of four submersed macrophytes {Myriophyllum spicatum, Potamogeton maackianus, Vallisneria spiralis and Hydrilla verticillata). Specific stem length decreased significantly in all four species, root weight ratio increased except for M. spicatum in response to high water level fluctuation while other phenotypic characters (i.e. main stem length, total length, branch number) and biomass allocation to special organ of shoot varied among species.3. The mechanisms of germination and hiding from grazing in Vallisneria spiralis. Average turion size of V. spiralis in Liangzi Lake increased with depth range from 2cm to 30cm in silt. Turion weight showed significant differences between classes (with one bud, two buds and three buds). Sediment depth, water regime and turion size had pronounced impact onemergence of turion. Removing the first bud and cutting turion into pieces just with one bud, which simulate the graze behavior by predator, stimulate the germination; Turions produced in last year and in present year have the same potential germination ability. These may be the mechanisms of V. spiralis to sustain its population size and dominance under the strong graze pressure from waterfowl during winter drought.4. The adaptation of Hydrocharis dubia to water level changes. H. dubia could elongate the max root length to meet the flooding, when water level decreased, it tends to root and can subsequently adapt the flooding by plasticity of leafstalk.