Search results
Results from the WOW.Com Content Network
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).
Each haploid nucleus then undergoes two rounds of mitosis which creates 4 haploid nuclei on each end of the embryonic sac. One nucleus from each set of 4 migrates to the center of the embryonic sac. These form the binucleate endosperm mother cell. This leaves three remaining nuclei on the micropylar end and three remaining nuclei on the ...
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.
Nucellar embryony is able to occur within both fertilized and unfertilized ovules. Furthermore, instead of using the endosperm as nutritive tissue, it will utilize the surrounding nucellus tissue for nutrition. [3] For example, the ‘Valencia’ orange undergoes nucellar embryony in both fertilized and unfertilized conditions. [3]
Double fertilization occurs when the pollen tube releases two sperm. One sperm fertilizes the egg to produce a zygote and the other fertilizes the polar nuclei producing a triploid endosperm nucleus. The endosperm nucleus divides to produce endosperm food for the plant. The ovule develops into a seed and contains the embryo and the endosperm.
The nucleus of the other sperm cell fuses with two haploid polar nuclei (contained in the central cell) in the centre of the gametophyte. The resulting cell is triploid (3n). This triploid cell divides through mitosis and forms the endosperm , a nutrient -rich tissue , inside the seed . [ 7 ]
The endosperm is surrounded by the aleurone layer (peripheral endosperm), filled with proteinaceous aleurone grains. Originally, by analogy with the animal ovum, the outer nucellus layer was referred to as albumen, and the inner endosperm layer as vitellus. Although misleading, the term began to be applied to all the nutrient matter.
The aleurone layer is the outermost layer of the endosperm, followed by the inner starchy endosperm. [1] This layer of cells is sometimes referred to as the peripheral endosperm. It lies between the pericarp and the hyaline layer of the endosperm. Unlike the cells of the starchy endosperm, aleurone cells remain alive at maturity.