Effects of Initial Density on Biomass,Number of Nodes and Shoot Length of 3 Kinds of Macrophytes

An experiment was designed to study the effect of various initial densities of Myriophyllum spicatum,Ceratophyllum demersum and Elodea nuttallii on their population through comparing their biomass,number of nodes and shoot length.The experiment was carried out in big barrels with freshwater and stream substrate in Cuihu National Urban Wetland Park.The macrophytes were harvested and the population's number of nodes and shoot length were measured at the time of harvest,then the macrophytes were dried,and weighed for each population,variables of individuals were counted through dividing the whole variables of populations.The results showed that 3 variables of these macrophytes increased when the density became higher,especially Ceratophyllum demersum and Elodea nuttallii even showed a trend of eruption growth,which indicated that all of these populations did not reach their limits.Biomass,number of nodes and shoot length of individual of Myriophyllum spicatum and Elodea nuttallii significantly declined when density became higher,however,density did not significantly affect individual of Ceratophyllum demersum.The reason was that Myriophyllum spicatum and Elodea nuttallii could possess more space by growing a lot of branches or extending their shoots,but high density restricted these growth.As to Ceratophyllum demersum,it could adapt to overcrowded environment by its high fractal dimension leaves.The higher density for Ceratophyllum demersum could be set to reach a higher production goal in productive activities.Elodea nuttallii is also widely used in aquatic product cultivation;more experiments need to be done to find a proper density to reach the largest production in a longer time.For Myriophyllum spicatum,it is always used in wetland ecological restoration with ordinary plant density.