A typical angiosperm embryo sac contains 8 nucleus and 7 cells. These 8 nucleus are formed by ………..

Options

A. 4 mitotic divisions
B. 7 mitotic divisions
C. 5 meiotic divisions
D. 4 meiotic divisions

Answer

To solve the question about how the 8 nuclei in a typical angiosperm embryo sac are formed, we can break down the process step by step:

### Step-by-Step Solution:

1. **Understanding the Structure**:
- A typical angiosperm embryo sac contains 8 nuclei and 7 cells. The 8 nuclei are formed from a single functional megaspore.

2. **Formation of the Megaspore**:
- Inside the ovule of the angiosperm, a diploid cell called the megaspore mother cell (MMC) undergoes meiosis. This process is crucial as it reduces the chromosome number by half.

3. **Meiosis Process**:
- The MMC undergoes meiosis, resulting in four haploid megaspores. However, only one of these megaspores is functional, while the other three degenerate.

4. **Mitosis of the Functional Megaspore**:
- The single functional megaspore then undergoes a series of mitotic divisions.
- The first mitotic division occurs, resulting in a two-nucleate stage.
- These two nuclei migrate to opposite poles of the cell.

5. **Further Mitosis**:
- The two nuclei undergo another round of mitosis, leading to a four-nucleate stage.
- These four nuclei then undergo a third round of mitosis, resulting in an eight-nucleate stage.

6. **Cell Formation**:
- Out of the 8 nuclei formed, 6 nuclei are surrounded by cell walls, forming 7 cells in total. The remaining 2 nuclei are located in the central cell, which is known as the polar nuclei.

7. **Conclusion**:
- In summary, the 8 nuclei are formed from 1 meiosis (in the MMC) followed by 3 mitotic divisions of the functional megaspore. Therefore, the answer to the question is that the 8 nuclei are formed by 1 meiosis and 3 mitotic divisions.