GROWTH CHARACTERISTICS OF CLONES OF A SUBMERGED MACROPHYTE POTAMOGETON CRISPUS

Aquatic environment was more suitable for clonal propagation than terrestrial environment,so most aquatic plants were inclined to clone.Potamogeton crispus was one of clonal aquatic plants.It was a dispersed species which flourished in urban waterways in North China.The growth conditions of clones decided the dynamics of clonal plant population and the survival strategies of clones effected the utilization of environmental resources by clonal plant population.We studied the growth characteristics of Potamogeton crispus clones on typical development phases,so the results may supply basis to predict population fluctuation of Potamogeton crispus and to control population scale of Potamogeton crispus.Typical development phases of Potamogeton crispus were seedling growth phase,winter-through phase,exponential growth phase and propagation phase.The growth characteristic of clones during each time phase was studied at individual level.Intact clones were collected in Jinhe River from November 2006 to June 2007.We culled 30 intact clones randomly and then cut off erect stems from rhizomes of each clone.After these erect stems numbered,we measured their height and divided them into three equal parts with the same length.Trace the outline of all leaves on each equal part on paper with even texture,and calculate leaf area of each equal part by weighing method.The clones were separated into three parts containing leaves,stems and rhizomes(five parts containing leaves,stems,rhizomes,turions and inflorescence during propagation phase) finally.Every member was dried at 65℃ for 96h and then weighed by analytical balance.The correlation among its several quantity properties were analyzed in our laboratory.Linear function(y= a+bx),power function(y=axb) and exponential function(y= aebx) were used to fitting the correlation among these quantity properties.The function with the maximal determination coefficient was culled to be description model.The results showed that along with the development of Potamogeton crispus clones,biomass allocation proportion of leaves was gradually increased and the proportion of stems was reduced gradually.Biomass allocation proportion of rhizomes and roots was relatively stable on different development phases.As a whole,the sequence of member biomass allocation proportion of mature clones were leavesstemsrhizomes and roots.With the increase of ramets height,leaves biomass of ramets were exponent-functionally increased during exponential growth phase.The power allomteric growth of leaves and stems biomass on propagation phase were much more affected by environmental conditions when compared with winter-through phase.Leaves and stems biomass of ramets were steadily positively correlated with total biomass of ramets on all development phases.The total biomass of ramets was allocated to leaves and stems of ramets differently on every development phase and the proportion was highly controlled by heredity.With the increase of ramets height,the upper,middle,nether part leaves area of ramets were in an power allometric growth on seedling growth phase and winter-through phase whereas they were in a linear isogony growth on exponential growth phase and propagation phase.Especially the upper part leaves area was the furthest positively correlated with ramets height on every development phase.