In angiosperms, for the formation of one embryosac, 1 meiosis takes place in the megaspore mother cell. And subsequently 3 mitotic divisions occur for the development of the 7 celled 8 nucleated structure. So, to form four fully developed polygonum type of embryosac in angiosperm the total number of meiosis and mitosis division generation required are (1*4=4 and 3*4=12) respectively.

In angiosperms, the formation of embryo sacs occurs within the ovule and is crucial for sexual reproduction. Each embryo sac contains the female gametophyte, which plays a key role in fertilization. The formation of four fully developed polygonum-type embryo sacs requires a specific number of meiosis and mitosis divisions.



The formation of the polygonum-type embryo sac involves a series of developmental processes that can be divided into several stages:

1. Megaspore Mother Cell (MMC) Formation:
- The process begins with the formation of a megaspore mother cell (MMC) within the ovule.
- The MMC undergoes meiosis to produce four haploid megaspores.

2. Megaspore Selection:
- Out of the four megaspores, three degenerate, and only one functional megaspore remains.
- The functional megaspore undergoes mitosis to form two nuclei.

3. Nuclear Fusion:
- One of the nuclei undergoes three rounds of mitosis without cytokinesis, resulting in the formation of an eight-nucleate structure called the female gametophyte or embryo sac.
- The other nucleus migrates to the micropylar end and degenerates.

4. Embryo Sac Development:
- Within the embryo sac, the eight nuclei arrange themselves into specific patterns.
- Antipodal cells, located at the chalazal end, are formed by the three nuclei that migrate away from the micropylar end.
- The central cell, located in the center of the embryo sac, contains two polar nuclei.
- The egg cell, which is the female gamete, is located at the micropylar end of the embryo sac.
- Synergids, which play a role in guiding the pollen tube to the embryo sac, are also present.

5. Fertilization:
- Pollen grains are deposited on the stigma and germinate to form pollen tubes.
- The pollen tube grows through the style and reaches the micropyle of the ovule.
- Double fertilization occurs when one sperm fuses with the egg cell to form the zygote, and the other sperm fuses with the two polar nuclei to form the endosperm nucleus.



To form four fully developed polygonum-type embryo sacs, the following meiosis and mitosis divisions are required:

- Meiosis Divisions: One meiosis division occurs during megaspore mother cell formation, resulting in the production of four haploid megaspores.

- Mitosis Divisions: After megaspore selection, one mitosis division occurs, resulting in the formation of two nuclei within the functional megaspore. Subsequently, three rounds of mitosis occur within the embryo sac, leading to the formation of eight nuclei.

Therefore, a total of one meiosis division and four mitosis divisions are required for the formation of four fully developed polygonum-type embryo sacs in angiosperms.