gametofytet

Gametofytet, also called the gametophyte, is the haploid, multicellular generation in the life cycle of plants that bears the gametes. It develops from a spore produced by meiosis in the preceding sporophyte and, by mitosis, forms the male and female gametangia—antheridia and archegonia—where sperm and eggs are produced. Fertilization of an egg by sperm restores the diploid state and gives rise to the sporophyte.

In bryophytes such as mosses, liverworts, and hornworts, the gametophyte is the dominant, conspicuous, free-living phase, while the sporophyte is typically smaller and dependent on the gametophyte for nutrients. In most vascular plants, including ferns and seed plants, the sporophyte is the larger, longer-lived generation, and the gametophyte is reduced; in ferns the gametophyte is often a small, independent structure called a prothallus, whereas in seed plants the male and female gametophytes are microscopic and intimately associated with the sporophyte.

Gametophyte anatomy varies: in bryophytes it is usually leafy or thalloid and photosynthetic; in hornworts it is flattened; in ferns the prothallus is heart-shaped and nourishes gametangia. Gametangia produce gametes by mitosis; fertilization requires water for sperm motility in non-seed plants, after which the zygote grows into a new sporophyte.

Ecological and evolutionary significance: the gametophyte stage allows life cycle completion under moist conditions, contributes to genetic diversity via sexual reproduction, and reflects the plant's evolutionary shift toward sporophyte dominance in many lineages.