The effects of pollen addition on fruit set and sex expression in the andromonoecious herb horsenettle (Solanum carolinense).

摘要

As part of an ongoing investigation into the evolution and maintenance of andromonoecy in horsenettle, a field investigation was conducted at the base of Salt Pond Mountain in Virginia, USA, to addressed the following questions: whether fruit and seed production are pollen-limited; whether pollen additions affect sex expression; and whether the size of the floral display or the percentage of flowers that are male are associated with percentage fruit set, and therefore possibly related to the attraction of pollinators? Pollen additions were conducted on 25 plants in each of two populations, and 25 open-pollinated control plants were monitored at each site. Mean percentage fruit set and seed set per fruit were significantly greater in the pollen addition treatment than in the control, which indicates that both populations were pollen-limited. The percentage of flowers on a plant that were male was significantly greater in the pollen addition treatment than in the control, which suggests that pollenaddition affects sex expression in horsenettle. Percentage fruit set did not correlate with total flower number or percentage of male flowers, which indicates that a larger floral display does not affect pollinator behaviour in ways that influence female reproductive success. The results document the existence of pollen limitation in the two horsenettle populations studied and suggest that future studies should determine if male flower production influences male fitness or vegetative reproduction.