In a mature 7-celled or 8-nucleate embryo sac, the ploidy level of secondary nucleus is the same as that of:

Options

A. Synergids
B. Antipodals
C. Nucellus
D. Polars

Answer

To solve the question regarding the ploidy level of the secondary nucleus in a mature 7-celled or 8-nucleate embryo sac, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Structure of the Embryo Sac**:
- A mature embryo sac typically contains 7 cells and 8 nuclei. It consists of one egg cell, two synergids, three antipodal cells, and one central cell with two polar nuclei.

2. **Identifying the Secondary Nucleus**:
- The secondary nucleus is formed by the fusion of the two polar nuclei located in the central cell of the embryo sac.

3. **Determining the Ploidy Level of the Secondary Nucleus**:
- Each polar nucleus is haploid (n), meaning it contains one set of chromosomes. When these two haploid nuclei fuse, they form the secondary nucleus, which is diploid (2n). Thus, the secondary nucleus has two sets of chromosomes.

4. **Comparing with Other Structures**:
- Now, we need to compare the ploidy level of the secondary nucleus (2n) with the other options given:
- **Synergids**: These are haploid (n).
- **Antipodals**: These are also haploid (n).
- **Nucellus**: This is the tissue surrounding the ovule and is diploid (2n).
- **Polar Nuclei**: These are haploid (n).

5. **Conclusion**:
- The only structure that has the same ploidy level (2n) as the secondary nucleus is the **nucellus**. Therefore, the correct answer is **nucellus**.

### Final Answer:
The ploidy level of the secondary nucleus is the same as that of the **nucellus**.

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