Question

Explain how the Female Gametophyte development process works at a mechanistic level?

Answer 1

Female gametophyte development starts occuring during ovule development.This happens when the diploid mother megaspore cell undergo meiosis. After meiosis, then this goes to form haploid megaspore which forms the female gametophyte.Genetic and epigenetic process mediate specific development process from a diploid megaspore to haploid female gametophyte.Auxins also help in maintaining a gradient to begin the formation of female gametophyte polarity to induce proper development of the female gametophyte. This gametophyte can be formed by both asexual and sexual processes. The asexual method of gametophytic formation is known as gametophytic apomixis. So the process is like - diploid megaspore mother cell- haploid megaspore- haploid female gametophytes. The last step is known as megagametogenesis. The female gametophyte develops within ovule to form three antipodal cells, one central cell, two synergid cells and one egg cell. Female gametophyte is also known as embryo sac or megagametophyte. In angiosperms, two sperm cells are delivered to the female gametophyte in which one fuses with central cell and one with egg cell . Female gametophyte development is important for formation of sexual and apomictic seed formation. Usually the most common development is polygonum type. The megaspore enlarges in the beginning, forms a four nucleate coenocyte. This consists of two nuclei at pole. Cellularization process occurs and causes cell wall formation on all sides of gametophyte. This results in a seven celled structure.

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