Question

Explain the development of female gametophyte in angiosperm by well labelled diagram only.

Answer 1

Development of female gametophyte of Embryo sac: It develops from female megaspore, which is present inside the ovule or megasporangium. During the initial stage of development of ovule, primary archesporial cell demarked at the apex of the nucellus below the epidermis. It divides periclinal into an outer primary parietal cell and an inner primary sporogenous cell. The latter as a megaspore mother cell which is enlarged in size and divides meiotically to form a row of four megaspores. Of the four cells, the upper three cells degenerate. While the lowest one functional and is called the functional megaspore.

This cell forms four haploid megaspores by meitiocally, which are arranged linearly tetrad.

Of the four megaspores, three megaspores which are near the micropylar end degenerate and one megaspore of the chalazal end becomes functional. This functional megaspore during development forms female gametophyte.