Give different stages of development of female gametophyte.

Solution:

Female gametophyte is the main reproductive tissue found in the ovule and is developed by a single megaspore.

• Angiosperms have specialized sporophytic tissue present in the ovule. 
• Firstly, Megaspore mother cells present in the micropylar region undergo meiosis to give rise to 4 megaspores.
• In the majority of the angiosperms, only one out of the 4 megaspores remains functional whereas the other three degenerates. This type of development is called monosporic development.
• This functional megaspore then shows 3 mitotic divisions to form complete female gametophyte, also called an embryo sac.
• This functional megaspore nucleus divides mitotically to give rise to 2 nucleated embryosac which arranges at the micropylar and chalazal end each.
• Each of the megaspore then undergo 2 mitotic divisions further to give rise to the first 4 nucleated embryo sac and then 8 nucleated embryo sac. 
• Once the 8 nucleated stage is achieved, cell walls are formed resulting in the organization of female gametophyte.
• 2 megaspores from each end, come at the center to form polar nuclei or central cell below the egg apparatus whereas three cells at the micropylar end are called egg apparatus.
• 3 cells at the chalazal end are called antipodals.

This is how a 7-celled 8-nucleated mature embryo sac is formed.

​​​​​​Below picture is the diagrammatic representation of development of female gametophyte.