Gametophyt

Gametophyt, also spelled gametophyte, is the haploid multicellular generation in the plant life cycle that develops from a spore by germination. It produces gametes by mitosis, and fusion of these gametes during fertilization forms a diploid zygote that grows into the sporophyt.

In bryophytes such as mosses, liverworts, and hornworts, the gametophyt is the dominant life stage, visible and photosynthetic, while the sporophyt is usually smaller and dependent on the gametophyt for nutrition. The gametophyt bears the sexual organs: antheridia producing sperm and archegonia housing the eggs. Fertilization typically requires water for sperm to reach the egg.

In vascular plants, the sporophyt is the dominant generation. The gametophyt is reduced and often dependent on the sporophyt. In seed plants, the male gametophyt is the pollen grain, and the female gametophyt develops within the ovule (the embryo sac in angiosperms). The pollen delivers sperm to the ovule, enabling fertilization to produce a zygote that grows into the new sporophyt.

Meiosis occurs in the sporophyt to generate haploid spores that seed the next gametophyt generation. Across plant groups, there are variations in the degree of gametophyt development and dependence on the sporophyt, as well as differences in how sperm reach the egg (water dependence versus pollen tubes).