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Megagametogenesis; development of the megaspore(s) into the megagametophyte(s) which contains the gametes. [2] In gymnosperms and most flowering plants, only one of the four megaspores is functional at maturity, and the other three soon degenerate.
Plant embryonic development, also plant embryogenesis, is a process that occurs after the fertilization of an ovule to produce a fully developed plant embryo. This is a pertinent stage in the plant life cycle that is followed by dormancy and germination . [ 1 ]
Prior to megagametogenesis, a developing embryo undergoes meiosis during a process called megasporogenesis. Next, three out of four megaspores disintegrate, leaving only the megaspore that will undergo the megagametogenesis. [3] The following steps are shown in Figure 1, and detailed below. The remaining megaspore undergoes a round of mitosis.
As the embryo and endosperm develop, the wall of the embryo sac enlarges and combines with the nucellus and integument to form the seed coat. The ovary wall develops to form the fruit or pericarp, whose form is closely associated with type of seed dispersal system. [68] Other parts of the flower often contribute to forming the fruit.
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 parts of a flower Double fertilization. Double fertilization or double fertilisation (see spelling differences) is a complex fertilization mechanism of angiosperms.This process involves the fusion of a female gametophyte or megagametophyte, also called the embryonic sac, with two male gametes (sperm).
The female gametophyte — specifically termed a megagametophyte — is also called the embryo sac in angiosperms. The megagametophyte produces an egg cell for the purpose of fertilization. The ovule is a small structure present in the ovary. It is attached to the placenta by a stalk called a funicle. The funicle provides nourishment to the ovule.
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 ...