xenogamy

Xenogamy is a mode of fertilization in which male gametes (pollen) fertilize female gametes (ovules) from a different individual of the same species. In seed plants, xenogamy typically occurs through cross-pollination, where pollen must travel from one plant to the stigma of another. It is contrasted with autogamy, self-fertilization within the same flower or plant, and geitonogamy, pollination between flowers on the same individual.

The biological significance of xenogamy lies in promoting genetic diversity. By combining genes from distinct individuals, offspring often have increased heterozygosity and adaptive potential, and populations may experience reduced inbreeding depression. Many species have evolved mechanisms to favor xenogamy, such as self-incompatibility systems that prevent self-pollen from fertilizing ovules.

Pollination agents enabling xenogamy include biotic vectors like insects, birds, and mammals, as well as abiotic vectors such as wind or water. The success of xenogamy depends on pollen viability, compatible pollen–pistil interactions, and the timing of stigma receptivity relative to pollen arrival.

In plant breeding, xenogamy is often achieved through controlled cross-pollination, sometimes involving emasculation to prevent self-pollination and isolation to exclude unwanted pollen. While xenogamy commonly refers to cross-fertilization within a species, cross-species fertilization is generally not described as xenogamy and typically results in non-viable offspring.