EFFECT OF SEXUAL SYSTEMS AND DICHOGAMY ON LEVELS OF ABORTION AND BIOMASS ALLOCATION IN PLANT REPRODUCTIVE STRUCTURES

The levels of abortion at three stages (ovule, seed, and flower-fruit) and biomass allocation to flowers, seeds, and fruits were determined in 231 species from five Venezuelan plant communities. These values we re analyzed as a function of the sexual systems of the plants and the presence of dichogamy. In this study, the only significant difference between sexual systems was in the level of ovule abortion, which was g reater in dioecious and hermaphroditic species than in monoecious and andromonoecious species. Species with protandrous or protogynous flowe rs had higher seed set and lower levels of aborted ovules and aborted flowers and fruits than species with adichogamous flowers. These resul ts indicate that hermaphroditic plants do not compensate for their ina bility to independently control the number of male and female flowers by producing an excess of flowers that function mainly as pollen donor s. On the other hand, the temporal separation of male and female funct ions in hermaphroditic and monoecious species may contribute to increa sed seed and fruit set by enhancing reallocation of assimilates from f loral organs or flowers to fruit formation in time, and by reducing po llen-stigma interference within plants.