A condition where the protoxylem lies towards periphery and metaxylem lies towards the centre is

Options

A. Exarch
B. Endarch
C. Mesarch
D. Diarch

Answer

To solve the question regarding the condition where the protoxylem lies towards the periphery and metaxylem lies towards the center, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Vascular Bundles**: Vascular bundles are the arrangements of xylem and phloem in plants. Xylem is responsible for water transport, while phloem transports nutrients.

2. **Identifying Protoxylem and Metaxylem**:
- **Protoxylem**: This is the first-formed xylem that develops during the early stages of plant growth.
- **Metaxylem**: This is the later-formed xylem that develops after protoxylem.

3. **Analyzing the Arrangement**:
- In the condition described, the protoxylem is located towards the periphery (outer part) of the vascular bundle, while the metaxylem is located towards the center (inner part).

4. **Recognizing the Terminology**:
- The arrangement where protoxylem is on the outside and metaxylem is on the inside is referred to as **Exarch**.
- This term indicates that the protoxylem is positioned externally (ex- meaning outside).

5. **Comparing with Other Conditions**:
- **Endarch**: Here, the protoxylem is located towards the center, and metaxylem is towards the periphery.
- **Massarch**: In this arrangement, protoxylem surrounds metaxylem.
- **Diarch**: This refers to the presence of two vascular bundles.

6. **Conclusion**: Based on the definitions and arrangements, the correct condition where protoxylem is towards the periphery and metaxylem is towards the center is called **Exarch**.

### Final Answer:
The condition where the protoxylem lies towards the periphery and metaxylem lies towards the center is called **Exarch**.

---