Pollen tube growth in tristylousPontederia cordata(Pontederiaceae)

摘要

Pollen tube growth rates in legitimate cross- and self-pollinations were compared by controlled hand pollination in two varieties ofPontederia cordataL. (Pontederiaceae). In each pollenndash;stigma combination pollen germinated readily on stigmas and pollen tubes penetrated stigmatic tissue. Pollen tube length in styles was positively correlated with pollen size. In most pollinations legitimate pollen tubes grew more rapidly in styles than self pollen tubes. This difference was statistically significant in most comparisons. Inhibition of incompatible pollen tubes was either in the style or ovary. It is suggested that the mechanisms of incompatibility may differ among the floral morphs and depend on the particular pollen size involved in pollinations. The observed differences in pollen tube growth of legitimate cross- and self-pollinations inP.cordatasuggest that the species is primarily outbreeding.