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The patterns of genetic variation among B. calyciflorus clones collected during summer from Lake Jinghu, Wuhu (China) were determined by allozyme electrophoresis, and the reproductive differences among the four clones (clone A, B, C and D, which were randomly selected from the four different composite electromorphs, respectively) were studied. Besides, sediment samples from the two sections of Lake Jinghu were hatched in situ as well as incubated at 10℃, 20℃and 30℃. The main results were presented as the following:1 Patterns of genetic variation among B. calyciflorus clones collected during summer from Lake Jinghu were determined using vertical polyacrylamide gel electrophoresis of isoenzymes. Two of the six enzymes assayed– malic dehydrogenase (MDH) and glucose phosphate isomerase (GPI)—were variable, and were selected to screen the 16 clones obtained from field collections. Four composite electromorphs (clone A,B,C and D) formed by combining isozymes variants were found in the 16 clones. The asexual and sexual reproductions of the four clones, each of which was randomly selected from the four composite electromorphs respectively, were compared under four concentrations (1.0,2.0,4.0,8.0×106 cells/ml) of alga S. obliquus. The results showed that there were significant effects of food concentration, clone and their interaction on the instantaneous rate of population increase, mixis rate, fertilization rate and resting egg production of B. calyciflorus. Among the four clones, instantaneous rate of population growth, mixis rate, fertilization rate and resting egg production of Clone D were all the largest, but the growth rate of Clone B as well as the mixis rate, fertilization rate and resting egg production of Clone A were the smallest. There were no significant correlations between food concentration and the rate of population increase of Clone B as well as the mixis rate and fertilization rate of Clone A, B and C. However, the relationships between food concentration and the rate of population increase of Clone A and C were significantly curvilinear, with the regression equation Y=0.0189X2-
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