Reproductive biology in Acacia caven (Mol.) Mol. (Leguminosae) in the central region of Argentina

Studies on Acacia caven (Mol.) Mol. in central Argentina indicate that the species is polygamous (andromonoecious), some plants having a high proportion of staminate heads. Though pollen/ovule ratios of flowers, inflorescences and plants are at a level common for 'facultative xenogamic' systems, controlled pollination shows a marked xenogamy. The ratio between pollen grains in the polyad and the maximum number of seeds per pod is close to one. Observations support the idea of the inflorescence as a specialized reproductive unit with gynoecia functioning as fixed modules in which all or none of its ovules develop into seeds. Mass flowering prior to the growing season, the absence of other floral resources in the community, the high degree of fruiting limitations and scarce insect visitation suggest that, as in other Acacia , the reproductive system of Acacia caven involves a great sacrifice of floral resources.