A characteristic feature of higher plants is the presence of the correct alternation of generations in their life cycle. The plant is represented by

Alternation of generations in plants [Gametophyte sporophyte stages, phases]

A characteristic feature of higher plants is the presence of the correct alternation of generations in their life cycle. The plant is represented by two phases of development, naturally succeeding each other — gametophyte and sporophyte.

Gametophyte — a sexual generation, in which occurs the formation the antheridia and archegonium sexual organs, — is replaced by asexual generation — sporophyte, in which occurs formation of asexual reproduction organs — sporangia (in many plants male and female gametophytes are separate ones).

Spores form in the sporangia. Sporangium has a shell, consisting of one or more layers of cells. Inside of sporangia, forms a multicellular sporogenous tissue — archespore.

Mother cells of spores are formed during archesporial cell division. Mother cells commence meiosis, as result of which each of them form four haploid cells — tetrad of spores. Sporophyte is always diploid: each cell contains its double set of chromosomes (2X). Taken from http://worldofschool.org

In all higher plants, reduction division takes place during the formation of spores in sporangia. Spore is haploid, the gametophyte development starts from it.

Gametophyte is always haploid, all his cells have X chromosomes. The transition from haploid to diploid state occurs during fertilization. Zygote is diploid. Later a sporophyte develops from it.

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