Which one develops from exostome

Options

A. Arillode
B. Operculum
C. Sarcotesta
D. Endothelium.

Answer

To determine which structure develops from the exostome, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Exostome**:
- The exostome is defined as the opening in the outer integument of the ovule. The integument serves as the protective covering for the ovule.

2. **Identifying Related Structures**:
- The options provided are: eryloid, operculum, sarcotesta, and endothelium. We need to analyze these terms in relation to the exostome.

3. **Analyzing the Structures**:
- **Aryl**: This structure develops from the funicle, which is the stalk that attaches the ovule to the ovary wall. However, there is a distinction made here that the "airyloid" (often referred to as false aryl) does not develop from the funicle but instead from the exostome.
- **Operculum**: This is typically a lid-like structure found in some plant reproductive structures but is not directly related to the exostome.
- **Sarcotesta**: This refers to the fleshy outer layer of a seed, which does not develop from the exostome.
- **Endothelium**: This is the inner layer of the seed coat, which also does not originate from the exostome.

4. **Conclusion**:
- Based on the analysis, the structure that develops from the exostome is the "airyloid." Therefore, the answer to the question is **airyloid**.

### Final Answer:
The structure that develops from the exostome is **airyloid**.