Which part is different from others with reference to ploidy number in Cycas

Options

A. Nucellus
B. Endosperm
C. Seed coat
D. Perisperm.

Answer

To determine which part is different from others with reference to ploidy number in Cycas, we need to analyze the ploidy levels of the various components mentioned in the options.

### Step-by-Step Solution:

1. **Understand the Ploidy Levels**:
- Ploidy refers to the number of sets of chromosomes in a cell.
- Diploid (2n) means there are two sets of chromosomes, while haploid (n) means there is one set.

2. **Identify the Options**:
- A. Nucleus
- B. Endosperm
- C. Seed coat
- D. Perisperm

3. **Analyze Each Option**:
- **Nucleus**: In the context of Cycas, the nucleus of the somatic cells is diploid (2n).
- **Endosperm**: The endosperm is formed during fertilization and is typically haploid (n) in gymnosperms like Cycas.
- **Seed coat**: The seed coat is derived from the integuments and is diploid (2n).
- **Perisperm**: The perisperm, which is the tissue that nourishes the seed, is also diploid (2n).

4. **Compare the Ploidy Levels**:
- Nucleus: 2n
- Endosperm: n (haploid)
- Seed coat: 2n
- Perisperm: 2n

5. **Identify the Different Part**:
- The only part that is different in terms of ploidy number is the **endosperm**, which is haploid (n), while all the other options (nucleus, seed coat, and perisperm) are diploid (2n).

6. **Conclusion**:
- Therefore, the part that is different from others with reference to ploidy number in Cycas is **B. Endosperm**.

### Final Answer:
B. Endosperm