Distyly is a floral polymorphism in which about half of the plants in a population have long styles and short stamens (Pin), whereas the remainder possess short styles and long stamens (Thrum). It has been suggested that the relative position of anthers and stigmas in distylous flowers enhances pollen flow between flowers of opposite morphs (legitimate pollination), in comparison to pollen flow between flowers of the same morph (illegitimate pollination). We studied the floral morphology of both floral morphs (six variables) in Palicourea padifolia (Rubiaceae) and found significant differences between floral morphs in floral traits that define the floral polymorphism. However, the correlations between morphological traits that define the floral morphs (morph-specific), and the significant correlations were stronger in the short styled morph. The morph-specific correlation patterns among some of the floral traits suggest differential selective pressures between floral morphs, regardless of corolla length.
Heterostyly promotes compatible pollination in buckwheats: Comparisons of intraflower, intraplant, and interplant pollen flow in distylous and homostylous Fagopyrum
