Here's a breakdown of the ploidy levels in the cells you mentioned, along with explanations:

1. Nucellus

* Ploidy: 2n (diploid)

* Explanation: The nucellus is the tissue that surrounds the megaspore mother cell (MMC) within the ovule. It's derived from the diploid sporophyte generation of the plant.

2. Megaspore Mother Cell (MMC)

* Ploidy: 2n (diploid)

* Explanation: The MMC is a diploid cell within the nucellus that undergoes meiosis to produce megaspores.

3. Functional Megaspore

* Ploidy: n (haploid)

* Explanation: The MMC undergoes meiosis, resulting in four haploid megaspores. Usually, only one of these megaspores survives and becomes the functional megaspore.

4. Female Gametophyte (Embryo Sac)

* Ploidy: n (haploid)

* Explanation: The functional megaspore undergoes mitotic divisions to form the female gametophyte (embryo sac), which is also haploid. The embryo sac contains the egg cell, which will eventually be fertilized by a sperm cell.

In Summary:

* The nucellus is diploid.

* The megaspore mother cell is diploid.

* The functional megaspore is haploid.

* The female gametophyte (embryo sac) is haploid.