Medium‐Length Stamen Mediates Delayed Selfing in a Two‐Step Self‐Pollination System in Commelina communis

We examined the functional roles of trimorphic stamens in self‐pollination in Commelina communis using quantum dots to label pollen grains. Under greenhouse conditions without pollinators, prior selfing via bud pollination and delayed autonomous selfing resulted in similar amounts of pollen deposition on stigmas. Delayed selfing was achieved primarily by the anther of the medium‐length stamen (M‐anther), whereas the long anthers (L‐anthers), adjacent to the stigma during anthesis, and the short anthers (S‐anthers), which produce few infertile pollen grains, did not contribute. In field experiments, a low visit frequency of illegitimate pollinators restricted pollen transfer between flowers. Nevertheless, pollen deposition via L‐anthers increased and became comparable to that achieved through prior selfing and M‐anther–mediated delayed selfing, reflecting pollinator‐mediated autogamy during anthesis. Our results reframe heteranthery in C. communis as part of a temporally structured two‐step self‐pollination system and provide a basis for reassessing its functional significance under variable pollination environments.