Sexual asymmetry in hermaphroditic plants.

Populations of hermaphroditic plants show variation in ovule and pollen production, so that the implicit assumption that hermaphrodite individuals function half as male and half as female is not valid. Such variation in gamete production results in sexual asymmetry, defined as nonconstant ratios of pollen to ovule production among plants of a population. This article reviews (1) some of the considerable amount of recent evidence for sexual asymmetry and non-equal malelfemale sex functioning in hermaphroditic seed plants, and (2) some models of asymmetry and sex functioning, with emphasis on their biological and evolutionary relevance.