chasmogamous

Chasmogamy is a term in botany for a reproductive strategy in flowering plants in which flowers open at maturity, exposing the sexual organs to pollinators or to the external environment and enabling cross-pollination. The word derives from Greek elements meaning “gap” or “opening” and “marriage.”

In chasmogamous flowers, the corolla typically opens to reveal the stamens and pistil, making pollen transfer possible by biotic vectors such as insects, birds, or bats, or by abiotic means such as wind or water, depending on the species. This opening and exposure often align with pollinator activity and can promote cross-pollination, which increases genetic diversity. However, self-pollination can still occur if cross-pollen is unavailable or if the flower structure permits selfing.

Many plant groups use chasmogamy in combination with other reproductive strategies. Some species produce chasmogamous flowers alongside or within a mixed-mating system that also includes cleistogamous flowers—flowers that remain closed and self-pollinate without opening. The presence of both strategies provides reproductive assurance under varying environmental conditions and pollinator availability.

Cleistogamy, the contrasting strategy, involves flowers that never open, facilitating self-pollination and seed set when pollinator services are unreliable. The balance between chasmogamy and cleistogamy varies among taxa and habitats, reflecting different selective pressures related to pollination biology, genetic diversity, and reproductive assurance.