Q.Explain the process of megasporogenesis leading to the formation of a functional megaspore.

This is the female counterpart of microsporogenesis.

Within the nucellus of a young ovule, one cell differentiates as the megaspore mother cell (MMC) -- a large cell with dense cytoplasm and a prominent nucleus, situated toward the micropylar end. The MMC is diploid and undergoes meiosis (megasporogenesis), producing four haploid megaspores, which are typically arranged in a linear (or occasionally T-shaped) tetrad.

In the great majority of flowering plants, only one of these four megaspores remains functional -- usually the one situated at the chalazal end of the tetrad -- while the other three progressively degenerate. This single surviving cell is called the functional megaspore, and it alone goes on to develop, through further mitotic divisions, into the mature embryo sac (female gametophyte). Because only one of the four products is retained, this pattern is described as monosporic development.

Start from the MMC in the nucellus, apply meiosis to get four megaspores, then state which one (chalazal) typically survives as functional.

Confusing the megaspore mother cell (undergoes meiosis) with the functional megaspore (its surviving haploid product); assuming all four megaspores develop further.