Abstract: The pollination mechanism and mating system of Sagittaria pygmaea were studied synthetically. In natural or experimental populations, interfloral pollination by insects was observed, and the pollen flows are mediated by insect pollination. Most pollen grains moved by pollinators are very near to neighbors, occa-sionally longer distance pollination is occurred. The pollen flows mediated by wind were not found. Results of artificial isolation and pollination showed that the fruit - sets after artificial selfing/outcrossing were consider-ably high, and that the monoecy and dichogamy in inflorescence were outcrossing mechanisms. Using isozyme genetic markers, the mating system parameter of a population in this species was estimated quantita-x lively. According to the value of the outcrossing rate ( t = 49. 9% ) , the mating system of the species stud-ied could be a concurrent selfing/outcrossing system. The authors deduced that the higher rate of selfing of population in S. pygmaea should be due to the frequency of crossing between different ramets in the same in-divadual.

Key words: Sagittaria pygmaea