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A megaspore mother cell, or megasporocyte, is a diploid cell in plants in which meiosis will occur, resulting in the production of four haploid megaspores. At least one of the spores develop into haploid female gametophytes, the megagametophytes. [1] The megaspore mother cell arises within the megasporangium tissue.
Pollen cones or microstrobili usually develop toward the tips of the lower branches in clusters up to 50 or more. The microsporangia of gymnosperms develop in pairs toward the bases of the scales, which are therefore called microsporophylls. Each of the microsporocytes in the microsporangia undergoes meiosis, producing four haploid microspores.
These become pollen grains, within which the microspores divide twice by mitosis to produce a very simple gametophyte. Heterosporous plants that produced microspores in microsporangia and megaspores in separate megasporangia evolved independently in several plant groups during the Devonian period.
Microgametogenesis is the process in plant reproduction where a microgametophyte develops in a pollen grain to the three-celled stage of its development. In flowering plants it occurs with a microspore mother cell inside the anther of the plant.
The pollen grains, which are the male gametophytes, are reduced to only a few cells (just three cells in many cases). Here the notion of two generations is less obvious; as Bateman & Dimichele say "sporophyte and gametophyte effectively function as a single organism". [8] The alternative term 'alternation of phases' may then be more appropriate ...
The result is the production of four haploid cells (n chromosomes; 23 in humans) from the two haploid cells (with n chromosomes, each consisting of two sister chromatids) [clarification needed] produced in meiosis I. The four main steps of meiosis II are: prophase II, metaphase II, anaphase II, and telophase II.
The outcome of sexual reproduction most often is the production of resting spores that are used to survive inclement times and to spread. There are typically three phases in the sexual reproduction of fungi: plasmogamy, karyogamy and meiosis. The cytoplasm of two parent cells fuse during plasmogamy and the nuclei fuse during karyogamy.
Each microsporocyte undergoes meiosis, forming four haploid microspores, each of which can eventually develop into a pollen grain. A microspore undergoes mitosis and cytokinesis in order to produce two separate cells, the generative cell and the tube cell. These two cells in addition to the spore wall make up an immature pollen grain.