Exarch xylem is found in

Options

A. leaf
B. petiole
C. stem
D. root

Answer

### Step-by-Step Solution:

1. **Understanding Exarch Xylem**:
- Exarch xylem refers to a specific arrangement of xylem tissues in plants where the protoxylem is located towards the periphery (outer side) and the metaxylem is located towards the center (inner side).

2. **Identifying Protoxylem and Metaxylem**:
- Protoxylem is the first formed primary xylem in the plant, while metaxylem is the later formed primary xylem. This distinction is important for understanding the arrangement in exarch xylem.

3. **Centripetal Development**:
- The development of exarch xylem follows a centripetal pattern, meaning that as the plant grows, the newer xylem cells are formed towards the center while the older cells are pushed outward.

4. **Characteristic Feature**:
- The arrangement of exarch xylem is a characteristic feature of roots in plants. This is different from other plant parts like stems and leaves, where different arrangements of xylem can be found.

5. **Conclusion**:
- Based on the above understanding, we can conclude that exarch xylem is specifically found in the roots of plants.

### Final Answer:
Exarch xylem is found in the root.

---