Explain with the help of a diagram the development of a mature embryo sac from a megaspore mother cell in angiosperm.

Explanation

The primary sporogenous cell functions directly as diploid megaspore mother cell or megasporocyte. The megaspore mother cell (MMC) undergoes meiosis and forms a linear tetrad of 4 haploid megaspores. The process of meiotic formation of haploid megaspores from diploid megaspore mother cell is called megasporogenesis. Commonly the chalazal megaspore remains functional while the other 3 degenerate

The functional megaspore is the first cell of female gametophyte. The cell enlarges and undergoes three free nuclear mitotic divisions. The first division produces two nucleate embryo sac. The two nuclei shift to the two ends and divide there twice forming four nucleate and then eight nucleate structure. One nucleus from each side moves to the middle. they are called polar nuclei. The remaining three nuclei form cells at the two ends. 3 celled & apparatus at the micropylar end and three antipodal cells at the chalazal end. The middle binucleate part organises itself into central cell.