heterosporösa

Heterosporösa (heterospory) denotes the condition in which a plant produces two distinct sizes and types of spores: smaller microspores that develop into male gametophytes and larger megaspores that develop into female gametophytes. This reproductive strategy contrasts with homospory, where only one kind of spore is produced and gametophytes are typically bisexual.

Heterospory occurs in several plant lineages, including some lycophytes (for example Selaginella and Isoetes), a limited number of ferns (such as members of Marsileaceae and Salviniaceae), and all seed plants (gymnosperms and angiosperms). The trait has arisen independently multiple times during plant evolution and is associated with changes in lifecycle organization, notably endosporic development of the gametophyte—where the gametophyte matures within the spore wall or retained tissues—and increased specialization of reproductive roles.

Ecologically and evolutionarily, heterospory is significant because it enables partitioning of resources between male and female reproductive functions, can reduce sibling competition and self-fertilization, and in seed plants it set the stage for the evolution of seeds through retention and protection of the megaspore and its developing female gametophyte. In ferns and lycophytes, heterospory is often linked to specific habitats or life histories, such as aquatic or heterophyllous species. Overall, heterosporous reproductive systems represent an important modification of the ancestral plant life cycle with substantial consequences for reproduction, dispersal, and diversification.