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Location of ovules inside a Helleborus foetidus flower. In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the integument, forming its outer layer, the nucellus (or remnant of the megasporangium), and the female gametophyte (formed from a haploid megaspore) in its center.
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] The nuclei on the antipodal end are simply known as the antipodal cells. [5]
A megaspore mother cell, or megasporocyte, is a diploid cell in plants in which meiosis will occur, resulting in the production of four haploid megaspores. At least one of the spores develop into haploid female gametophytes, the megagametophytes. [1] The megaspore mother cell arises within the megasporangium tissue.
The mature embryonic sac of an unfertilized ovule is 7-cellular and 8-nucleate. It is arranged in the form of 3+1+3 (from top to bottom) i.e. 3 antipodal cells, 1 central cell (binucleate), 2 synergids & 1 egg cell. One sperm fertilizes the egg cell and the other sperm fuses with the two polar nuclei of
At the other end of the cell, a cell wall forms around the nuclei and forms the antipodals. 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]
Three of these independent gametophyte cells degenerate and the one that remains is the gametophyte mother cell which normally contains one nucleus. [24] In general, it will then divide by mitosis until it consists of 8 nuclei separated into 1 egg cell, 3 antipodal cells, 2 synergid cells, and a central cell that contains two nuclei.
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 ...
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).