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Mitosis does occur, but no cell divisions are ever made. [13] This results in the mature female gametophyte in some Gnetophyta having many free nuclei in one cell. Once mature, this single celled gametophyte is 90% smaller than the female gametophytes in other gymnosperm orders. [14]
It is the biological process of gametogenesis during which cells that are haploid or diploid divide to create other cells. It can take place either through mitotic or meiotic division of diploid gametocytes into different cells depending on an organism's biological life cycle. For instance, gametophytes in plants undergo mitosis to produce gametes.
The resulting meiospores develop into a gametophyte. Both the spores and the resulting gametophyte are haploid, meaning they only have one set of chromosomes. The mature gametophyte produces male or female gametes (or both) by mitosis. The fusion of male and female gametes produces a diploid zygote which develops into a new sporophyte.
However, the parent sporophyte may be monoecious, producing both male and female gametophytes or dioecious, producing gametophytes of one gender only. Seed plant gametophytes are extremely reduced in size; the archegonium consists only of a small number of cells, and the entire male gametophyte may be represented by only two cells. [27]
These spores then germinate and divide by mitosis to form a haploid multicellular phase, the gametophyte, which produces gametes directly by mitosis. This type of life cycle, involving alternation between two multicellular phases, the sexual haploid gametophyte and asexual diploid sporophyte, is known as alternation of generations .
The sporophyte creates spores via meiosis which also then divide mitotically producing haploid individuals called gametophytes. The gametophytes produce gametes via mitosis. In some plants the gametophyte is not only small-sized but also short-lived; in other plants and many algae, the gametophyte is the "dominant" stage of the life cycle. [19]
When you buy a bottle of vitamins from a nutrition store, you’ll probably notice a best-by date on the bottom of the jar. But that inscribed number isn’t a hard-and-fast rule—there is some ...
The anther produces pollen grains that contain male gametophytes. The pollen grains attach to the stigma on top of a carpel, in which the female gametophytes (inside ovules) are located. Plants may either self-pollinate or cross-pollinate. The transfer of pollen (the male gametophytes) to the female stigmas occurs is called pollination.