Secondary xylem and phloem in dicot stem are produced by

Options

A. Vascualr cambium
B. Phellogen
C. Apical meristems
D. Axillary meristems

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the source of secondary xylem and phloem in dicot stems. Secondary growth is a characteristic of dicots, which leads to an increase in the thickness of the stem.

2. **Identifying the Relevant Tissues**: In dicot stems, the vascular system consists of xylem and phloem. Xylem is responsible for water and nutrient transport, while phloem transports food.

3. **Role of Vascular Cambium**: The vascular cambium is a type of lateral meristem that is responsible for the production of secondary xylem (wood) and secondary phloem (inner bark). It is located between the xylem and phloem.

4. **Location of Xylem and Phloem**: In dicot stems, the xylem is produced towards the inside (centrally located), while the phloem is produced towards the outside (peripherally located) of the vascular cambium.

5. **Understanding Meristem Types**: The vascular cambium is formed from two types of meristems:
- **Fascicular Cambium**: Located within the vascular bundles.
- **Interfascicular Cambium**: Located between the vascular bundles.

6. **Conclusion**: The secondary xylem and phloem in dicot stems are produced by the vascular cambium, which is responsible for secondary growth.

7. **Final Answer**: The correct answer is **vascular cambium**.

---