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An endosperm is formed after the two sperm nuclei inside a pollen grain reach the interior of a female gametophyte or megagametophyte, also called the embryonic sac.One sperm nucleus fertilizes the egg cell, forming a zygote, while the other sperm nucleus usually fuses with the binucleate central cell, forming a primary endosperm cell (its nucleus is often called the triple fusion nucleus).
In the most common type of megagametophyte development in flowering plants (the Polygonum type), three mitotic divisions are involved in producing the gametophyte, which has seven cells, one of which (the central cell) has two nuclei that later merge to make a diploid nucleus.
The maternal contribution to the genetic constitution of the triploid endosperm is double that of the sperm. In a study conducted in 2008 of the plant Arabidopsis thaliana, the migration of male nuclei inside the female gamete, in fusion with the female nuclei, has been documented for the first time using in vivo imaging. Some of the genes ...
These form the binucleate endosperm mother cell. This leaves three remaining nuclei on the micropylar end and three remaining nuclei on the antipodal end. The nuclei on the micropylar end is composed of an egg cell, two synergid cells, and the micropyle, an opening that allows the pollen tube to enter the structure. [ 4 ]
In the process of double fertilization, two sperm nuclei from a pollen grain (the microgametophyte), rather than a single sperm, enter the archegonium of the megagametophyte; one fuses with the egg nucleus to form the zygote, the other fuses with two other nuclei of the gametophyte to form 'endosperm', which nourishes the developing embryo.
A typical embryo sac contains seven cells and eight nuclei, one of which is the egg cell. Two nuclei fuse with a sperm nucleus to form the primary endospermic nucleus which develops to form triploid endosperm, which becomes the food storage tissue in the seed.
Aleurone (from Greek aleuron, flour) is a protein found in protein granules of maturing seeds and tubers. [clarification needed] The term also describes one of the two major cell types of the endosperm, the aleurone layer. The aleurone layer is the outermost layer of the endosperm, followed by the inner starchy endosperm. [1]
Authors may at times report the total combined ploidy of all nuclei present within the cell membrane of a syncytium, [38] though usually the ploidy of each nucleus is described individually. For example, a fungal dikaryon with two separate haploid nuclei is distinguished from a diploid cell in which the chromosomes share a nucleus and can be ...