Ask a Teacher

Search



life cycle of broyophyte
 Like all plants, the bryophyte life cycle goes through both haploid (gametophyte) and diploid (sporophyte) stages. The gametophyte comprises the main plant (the green moss or liverwort), while the diploid sporophyte is much smaller and is attached to the gametophyte. The haploid stage, in which a multicellular haploid gametophyte develops from a spore and produces haploid gametes, is the dominant stage in the bryophyte life cycle. The mature gametophyte produces both male and female gametes, which join to form a diploid zygote. The zygote develops into the diploid sporophyte, which extends from the gametophyte and produces haploid spores through meiosis. Once the spores germinate, they produce new gametophyte plants and the cycle continues.
A bryophyte spore germinates and produces an often algal-like mat, called a protonema (plural protonemata) and the leafy or thalloid stage of the gametophyte develops from the protonemal stage. The protonemata are almost always ephemeral but there are exceptions. Amongst the mosses there is a small number of species in which the protonemata are persistent and the leafy plants are ephemeral. The spore was haploid and so are the resulting protonema and the ensuing leafy or thalloid stages. The male and female sex organs, the antheridia and the archegonia respectively, are produced on the gametophytic plants. Haploid sperm are released from the antheridia and when a haploid sperm reaches a haploid egg in an archegonium the egg is fertilized to produce a diploid cell. This cell will develop into the diploid sporophyte. In a great many bryophytes the tissue in the embryonic sporophyte differentiates. Typically there will be a foot, that anchors the embryonic sporophyte to the supporting gametophyte, and at the end opposite the foot is the part that will develop into the spore capsule. In between there is typically the part that will become the stalk (or seta) that supports the spore capsule, though in a number of bryophytes the seta is short or even non-existent. By the time the sporophyte has matured the spore capsule will contain haploid spores.


comments powered by Disqus