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Therefore, the resulting embryo sac is a seven-celled structure consisting of one central cell, one egg cell, two synergid cells, and three antipodal cells. [ 2 ] [ 3 ] The bisporic and tetrasporic patterns undergo varying processes and result in varying embryo sacs as well.
The haploid microspore is stressed to trigger the embryogenesis pathway and the resulting haploid embryo either doubles its genome spontaneously or with the help of chromosome doubling agents. Without this double haploid technology, conventional breeding methods would take several generations of selection to produce a homozygous line.
The megagametophyte develops within the megaspore of extant seedless vascular plants and within the megasporangium in a cone or flower in seed plants. In seed plants, the microgametophyte (pollen) travels to the vicinity of the egg cell (carried by a physical or animal vector) and produces two sperm by mitosis.
Selaginella canaliculata Selaginella selaginoides Selaginella willdenowii is known for its iridescent colours. There are about 750 known species of Selaginella. [21] They show a wide range of characters; the genus is overdue for a revision which might include subdivision into several genera. [citation needed] Species of spikemoss include:
At least one of the spores develop into haploid female gametophytes, the megagametophytes. [1] The megaspore mother cell arises within the megasporangium tissue. In flowering plants the megasporangium is also called the nucellus, and the female gametophyte is sometimes called the embryo sac or embryonic sac.
There is debate as to whether endospory or heterospory evolved first. Some debate centers upon the requirement of endospory to develop before heterospory. [2] Endospory is assumed to follow heterospory but it has been suggested that without endospory, early plant species dependency on water fertilization and environmental impacts on gametophytic gene expression would have reduced the chances ...
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The gametophyte produces an egg cell. After fertilization, the ovule develops into a seed containing the embryo. [14] In flowering plants, the female gametophyte (sometimes referred to as the embryo sac) has been reduced to just eight cells inside the ovule. The gametophyte cell closest to the micropyle opening of the ovule develops into the ...