STUDIES ON THE FEMALE AND MALE REPRODUCTIVE FUNCTIONS WITH A HERMAPHRODITIC SPECIES, LOBELIA CARDINALIS (L.)

Perfect-flowered plants create difficulties when assigning sexual emphasis to individual plants. Perfect-flowered plants have generally been considered to place equal emphasis on both sexual functions. The studies reported use a perfect-flowered species, Lobelia cardinalis L. (Lobeliaceae), to examine this assumption.;Using the protandrous nature of the flowers, the phenotypic and functional gender of plants is examined. Phenotypic and functional gender vary temporally and there is considerable variation among plants. Phenotypic gender is male biased but functional gender is not. Numerous factors are shown to influence functional gender. In general, sex-differential reproductive success follows as a consequence of phenotypic gender but environmental variation makes this relationship less than precise.;With respect to seed and pollen production, bisexual flowers are functionally more female on the basal portion of the inflorescence and functionally more male on the terminal portion relative to the mean response of the inflorescence. Plants vary significantly in both seed and pollen production but no differences occur among the populations examined. Seed and pollen production per flower are genetically based and uncorrelated.;Plants vary considerably in seed and pollen yield. Seed and pollen yield are correlated but weakly. Yield components of seed are negatively correlated but yield components of pollen are not. Seed production per flower is negatively correlated with pollen yield; thus the relationship between seed and pollen production is quite complex and unlike that commonly assumed. Stressed plants change resource allocation patterns toward greater male emphasis.;Because the flowers of L. cardinalis are protandrous, the amount of time and nectar devoted to the sexual phases can be assigned and hummingbird visitation scored. Greater time and nectar are devoted to the staminate phase and hummingbirds visit staminate phase flowers more frequently. Thus plants emphasize the male function at anthesis and this emphasis is an intrinsic feature.;Perfect-flowered L. cardinalis plants are not equisexual but the description of sexuality is complex. Genetic constraints to sex allocation, sex specialization and sexual selection are discussed.