Question

Embryo sac develops from megaspore mother cell through
A. 1 meiosis and 2 mitosis
B. 1 meiosis and 3 mitosis
C. 1 meiosis and 2 meiosis
D. 2 meiosis and 2 mitosis

Answer 1

Hint:-Megaspores are a type of spore which is found in heterosporous plants. There are two types of spore and that are megaspores and microspores. Generally, the megaspore is the large spore that produces a female gametophyte and the microspore produces the male gametophyte

Complete step-by-step solution:
There are two types of spore present in the flowering plant which are the megaspores and microspores. Generally, female gametophyte develops from the megaspores which develop into an egg cell and male gametophyte develops from microspores which develop into sperm.
A megaspore mother cell is a diploid cell that is found in plants. The meiotic division takes place in the diploid cell and it leads to the production of four haploid megaspores. The megaspore mother cell is also known as megasporocyte. One spore develops into haploid female gametophytes. The megaspore mother cell grows within the megasporangium tissue. The megasporangium is also called the nucellus in flowering plants. The female gametophyte is called the embryo sac.
There are two processes to develop an embryo sac. These are megasporogenesis which is the formation of the megaspores in the megasporangium by the meiosis division and the other is mega gametogenesis which is the development of the megaspores into the megagametophyte.
During megasporogenesis, the megaspore is produced inside the megasporangium. A megaspore mother passes through the one meiosis division and develops four haploid cells. Meiosis results in four one-nucleate megaspores, of which three degenerate and one remain as functional. After that, the process of mega gametogenesis starts. In this process, a single functional megaspore passes through mitosis division three times and produces an eight-nucleate cell.
These eight nuclei are arranged into two groups in which the nucleus is present at the centre of the cell. These nuclei fuse before fertilization of the central cell and the three nuclei at the end of the cell form the egg apparatus, with an egg cell in the centre and two synergids. On the other end of the cell, a cell wall around the nuclei builds which forms the antipodal, and finally, the process results in an embryo sac.
Therefore, the correct option is option B.

Note:- A megaspore is a type of spore which is responsible for the development of female gametophyte. A megaspore mother cell is a diploid cell that develops into an embryo sac through two successive processes megasporogenesis and mega gametogenesis. In the first process, there is a one-time meiosis cell division that takes place, and in the second process, there is a three-way mitosis cell division.