Question

In angiosperms, the female gametophyte develops from a single cell of megasporangium.

Name that cell of megasporangium and describe the sequential changes it undergoes to form a mature female gametophyte.

Answer 1

Megaspore mother cell (MMC, megasporocyte) of the nucellus.

Sequential changes:

1. MMC (2n) undergoes meiosis → a linear/tetrad of four haploid megaspores.
2. Three megaspores degenerate; one functional megaspore remains (monosporic development).
3. Functional megaspore undergoes three successive free‑nuclear mitoses → 2 → 4 → 8 nuclei.
4. Nuclei arrange (three micropylar, three chalazal, two polar); cell walls form around six nuclei → a mature embryo sac (female gametophyte) that is 7‑celled, 8‑nucleate (egg + two synergids; three antipodals; central cell with two polar nuclei).