FLORAL EXPRESSION, POLLINATION MECHANISM AND MATING SYSTEM OF SAGITTARIA POTAMOGETIFOLIA
小慈姑的开花状态、传粉机制与交配系统

The floral expression and pollination mechanisms of Sagittaria potamogetifolia Merr., a helophyte species, were observed in natural populations. The species is insect and, concurrently, wind pollinated, but pollen flows are mediated mainly by insect pollination. The movements of pollinators are correlated with densities of inflorescence in populations, because the insect visitors have a certain capability to adapt to variations in population density. Outcrossing rates of 5 samples from 3 populations were quantitatively estimated by sampling from natural habitats and using an isozyme locus as a genetic marker. The outcrossing rates in the 5 samples (50 0%-92 8% ) indicate a mixed mating system dominated by outcrossing mechanisms. For the monoecious species S. potamogetifolia Merr., outcrossing rates are not correlated with densities of blooming plants in populations, but the level of outcrossing is dependent on the frequencies of individuals bearing more than two inflorescences.