Which structure among the following are diploid structures of gymnosperms?

Options

A. pollen grain
B. egg cell
C. microsporophyll
D. endosperm

Answer

To determine which structures among the given options are diploid structures of gymnosperms, we need to understand the basic life cycle of gymnosperms and the distinction between sporophytic and gametophytic structures.

### Step-by-Step Solution:

1. **Understanding Gymnosperms**:
- Gymnosperms are plants where the sporophyte is the dominant phase of the life cycle. The sporophyte is diploid (2n) and is responsible for producing spores through meiosis.

2. **Identifying Sporophytic vs. Gametophytic Structures**:
- Sporophytic structures are diploid and include parts of the plant that produce spores.
- Gametophytic structures are haploid (n) and arise from the spores produced by the sporophyte.

3. **Analyzing the Options**:
- **Pollen Grain**: This is the male gametophyte, formed from the microspore. Since it is a gametophyte, it is haploid (n).
- **Egg Cell**: This is the female gamete, also derived from the female gametophyte. Thus, it is haploid (n).
- **Microsporophyll**: This is a leaf-like structure that is part of the male cone (strobilus) in gymnosperms. It is associated with the sporophyte and contains sporangia, which are diploid (2n).
- **Endosperm**: In gymnosperms, the endosperm is not formed by double fertilization and is typically haploid (n).

4. **Conclusion**:
- Among the options provided, the **microsporophyll** is the only diploid structure because it is part of the sporophyte and contains sporangia that produce spores.

### Final Answer:
The diploid structure among the options is the **microsporophyll**.