Question

Embryo sac develops from megaspore mother cell through

• A. $2$ meiosis and $2$ mitoses
• B. $1$ meiosis and $2$ mitoses
• C. $1$ meiosis and $3$ mitoses
• D. $2$ meiosis and $1$ mitosis

Answer 1

The correct option is C $1$ meiosis and $3$ mitoses

Formation of megaspores
The megaspore mother cell undergoes the first meiotic division to form a dyad of $2$ haploid megaspores, which further undergoes the second meiotic division to finally form a linear tetrad of $4$ haploid megaspores. The megaspore on the chalazal remains functional whereas the other $3$ degenerate in case of monosporic development.


Embryo sac formation
1) The haploid nucleus of the functional megaspore divides mitotically to form two nuclei which move to the opposite poles to form a $2$nucleate embryo sac.
2) Two more mitotic nuclear divisions result in the formation of a $4-$nucleate embryo sac. This is followed by a final $8-$nucleate embryo sac consisting of $1$ egg cell, $2$ synergids, $3$ antipodal cells and $1$ central cell with $2$ polar nuclei.

Final answer
(B) $1$ meiosis and $3$ mitoses