By Editors Gametophyte Definition Gametophytes are the stage which produces sex cells in plants and algae that undergo alternation of generations. Unlike animals and other organisms that use sexual reproductiongametophytes do not produce their sex cells through meiosis.
Table of Contents Alternation of Generations All plants undergo a life cycle that takes them through both haploid and diploid generations. The multicellular diploid plant structure is called the sporophyte, which produces spores through meiotic asexual division.
The multicellular haploid plant structure is called the gametophyte, which is formed from the spore and give rise to the haploid gametes. The fluctuation between these diploid and haploid stages that occurs in plants is called the alternation of generations.
The way in which the alternation of generations occurs in plants depends on the type of plant. In bryophytes mosses and liverwortsthe dominant generation is haploid, so that the gametophyte comprises what we think of as the main plant.
The opposite is true for tracheophytes vascular plantsin which the diploid generation is dominant and the sporophyte comprises the main plant. Bryophyte Generations Bryophytes are nonvascularized plants that are still dependent on a moist environment for survival see Plant Classification, Bryophytes.
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 liverwortwhile 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. Tracheophyte Generations Tracheophytes are plants that contain vascular tissue; two of the major classes of tracheophytes are gymnosperms conifers and angiosperms flowering plants. Tracheophytes, unlike bryophytes, have developed seeds that encase and protect their embryos.
The dominant phase in the tracheophyte life cycle is the diploid sporophyte stage. The gametophytes are very small and cannot exist independent of the parent plant. The reproductive structures of the sporophyte cones in gymnosperms and flowers in angiospermsproduce two different kinds of haploid spores: This phenomenon of sexually differentiated spores is called heterospory.
These spores give rise to similarly sexually differentiated gametophytes, which in turn produce gametes.
Fertilization occurs when a male and female gamete join to form a zygote. The resulting embryo, encased in a seed coating, will eventually become a new sporophyte.Alternation of Generations Sexual reproduction involves the two alternating processes of meiosis and fertilization.
In meiosis, the chromosome number is reduced from the diploid to the haploid number. In fertilization, the nuclei of two gametes fuse, raising the chromosome number from haploid to diploid.
Plants exist in alternation generations called sporophytes and gametophytes.
Sporophytes represent the diploid phase of plants. Gametophytes represent the haploid phase of plants. Alternation of generations is a type of life cycle found in terrestrial plants and some algae in which subsequent generations of individuals alternate between haploid and diploid organisms.
This can be contrasted to sexual reproduction in animals, in which both . Jul 16, · C-Fern offers an obvious advantage in teaching alternation of generations because the gametophyte and sporophyte are macroscopic, free-living generations and the process of fertilization, involving the release of sperm that swim to the archegonia, can be .
While considering gametophyte versus sporophyte generations, there are some stark points, such as sporophyte is a diploid phase, whereas gametophyte is a haploid generation. Sporophyte stage is asexual, while gametophyte stage is sexual.
The 'alternation of generations' in the life cycle is thus between a diploid (2n) generation of sporophytes and a haploid (n) generation of gametophytes. Gametophyte of the fern Onoclea sensibilis (the flat thallus at the bottom of the picture) with a descendant sporophyte beginning to grow from it (the small frond at the top of the picture).