Secondary nucleus in the middle of an embryo sac of angiosperms is

Options

A. Tetraploid
B. Triploid
C. Diploid
D. Monoploid

Answer

To solve the question regarding the nature of the secondary nucleus in the middle of an embryo sac of angiosperms, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Embryo Sac**: The embryo sac is a structure found in the ovule of angiosperms (flowering plants). It contains several nuclei, including the egg cell and the secondary nucleus.

2. **Identifying the Secondary Nucleus**: The secondary nucleus, also known as the definitive nucleus, is formed from the fusion of two polar nuclei located at the center of the embryo sac.

3. **Determining the Ploidy Level**:
- Each polar nucleus is haploid (monoploid), meaning it contains one set of chromosomes.
- When these two haploid polar nuclei fuse, they create a diploid nucleus (2n), which is the secondary nucleus.

4. **Conclusion**: Therefore, the secondary nucleus in the middle of an embryo sac of angiosperms is diploid.

5. **Understanding Related Concepts**:
- It is important to note that during fertilization in angiosperms, one male gamete fuses with the egg cell to form the embryo, while the other male gamete fuses with the secondary nucleus to form the triploid endosperm (3n).
- This process is known as double fertilization, which is characteristic of angiosperms.

### Final Answer:
The secondary nucleus in the middle of an embryo sac of angiosperms is **diploid**.

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