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Pollen itself is not the male gamete. [4] It is a gametophyte, something that could be considered an entire organism, which then produces the male gamete.Each pollen grain contains vegetative (non-reproductive) cells (only a single cell in most flowering plants but several in other seed plants) and a generative (reproductive) cell.
Four chambers (pollen sacs) lined with nutritive tapetal cells are visible by the time the microspores are produced. After meiosis, the haploid microspores undergo several changes: The microspore divides by mitosis producing two cells. The first of the cells (the generative cell) is small and is formed inside the second larger cell (the tube cell).
[7] [8] These tissue arise from meristems that produce cells that differentiate into the different tissues that produce the parts of the gynoecium including the pistil, carpels, ovary, and ovules; the carpel margin meristem (arising from the carpel primordium) produces the ovules, ovary septum, and the transmitting track, and plays a role in ...
Gnetophyta may have 2 or 3 celled pollen grains depending on the species, and Coniferophyta pollen grains vary greatly ranging from single celled to 40 celled. [ 11 ] [ 10 ] One of these cells is typically a germ cell and other cells may consist of a single tube cell which grows to form the pollen tube, sterile cells, and/or prothallial cells ...
In the pollen grain, the generative cell gives rise to the sperm, whereas the vegetative cells have a tube cell that grows the pollen tube. Some plants have mechanisms in place to prevent self pollination, such as having stigma and anther mature at different times or being of different lengths, which significantly contributes to increasing ...
They had pollen grains that contained the male gametes for protection of the sperm during the process of transfer from the male to female parts. It is believed that insects fed on the pollen, and plants thus evolved to use insects to actively carry pollen from one plant to the next. Seed producing plants, which include the angiosperms and the ...
The pollen is carried to the pistil of another flower, by wind or animal pollinators, and deposited on the stigma. As the pollen grain germinates, the tube cell produces the pollen tube, which elongates and extends down the long style of the carpel and into the ovary, where its sperm cells are released in the megagametophyte.
Tapetum is important for the nutrition and development of pollen grains and a source of precursors for the pollen coat. [1] The cells are usually bigger and normally have more than one nucleus per cell. As the sporogenous cells undergo mitosis, the nuclei of tapetal cells also divide. Sometimes, this mitosis is abnormal, which is why many cells ...