Flower Phenology and Sexual Maturation: Partial Protandrous Behavior in Three Species of Orchids
Tremblay, Raymond L.
Méndez-Cintrón, María de Lourdes
MetadataShow full item record
Plants have theoretically multiple alternatives for preventing self pollination and consequently the effect of inbreeding, such as sequential flowering, dichogamy and self–incompatibility to name a few. We investigated the reproductive biology of three sequentially flowering (acropetal) endemic orchids from Puerto Rico. Since sequential flowering is present in the studied species and very rarely (1.0%) is there more than one flower open simultaneously on an inflorescence, we hypothesized that the orchids should be self-compatible and show no effect of protandry (dichogamy). We performed hand self—and crosspollinations and evaluated whether the species are self-compatible and whether the receptivity to pollination success (fruit set) is influenced by the age of flowers (protandry). We define protandry as pertaining to a hermaphroditic organism that assumes a functional male condition prior to shifting to a functional female state. We found that all three species are self-incompatible. Furthermore, flower age is important for predicting the likelihood of fruits set. Older flowers (6+ days) are significantly more likely to produce fruits (functional protandry). The multiple mechanisms for preventing self-pollination (sequential flowering, dichogamy and self-incompatibility) that are noted for these species suggest that the historical evolutionary processes for preventing inbreeding may be complex. We hypothesized that because multiple mechanisms are present for preventing self-pollination inbreeding depression is likely to be high.