Regulation of Seed-Set and Gender Variation in the Hermaphroditic Plant Potentilla anserina

This study deals with aspects of the maternal and paternal function of ramets, and of individual flowers, during several years in a seashore meadow population of Potentilla anserina. Regulation of maternal investment in plants may act by means of production of flowers and ovules, and through maturation of seeds. Pollen limitation of seed-set occurred during one of the years. However, data suggest that pollen availability commonly sets the limit to seed production. The regulation of maternal investment is therefore acting mainly before fertilization. Variation in flower number per ramet explained 23% of the variation in seed-set in ramets. The number of ovules per flower increased in response to nutrient addition, and may act as an additional regulative factor. Gender variation occurs both between flowers and between ramets. Femaleness of flowers increased with increasing resource availability. The occurrence of non-fruiting flowers was probably an effect of pollen limitation, and the hypothesis of male function of surplus flowers was not supported. Variation in functional gender in ramets showed a bimodal distribution and was not correlated between years for individual ramets. Gender variation is therefore presumably environmentally induced. 0. Eriksson, Dept of Plant Ecology, Inst. of Botany, Univ. of Stockholm, S-106 91