小慈姑的开花状态、传粉机制与交配系统

在自然种群中对沼生植物小慈姑（Sagittaria potamogetifolia Merr.）的开花状态和传粉过程作了观测，并用同工酶遗传标记法定量估测了其3个种群中5个样本的异交率。该种为中心媒传粉为主的虫／风 媒兼性传粉机制，访花昆虫的飞行距离多在0-2m范围内，并与花序密度呈不显著的正相关。异交率（－／^／t）为50.0％－92.8％，表明该种为异交为主的混合交配系统（ixed mating system）。对雌雄同株的小慈姑而言，异交率与各种群花期植株密度无关，异交水平取决于种群中开花花序的两个或两个以上的植株所占比例。

FLORAL EXPRESSION,POLLINATION MECHANISM AND MATING SYSTEM OF SAGITTARIA POTAMOGETIFOLIA

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.