In dicot roots, initiation of lateral roots and vascular cambium during the secondary growth takes place by________cells.

Options

A. Parenchyma
B. Pericycle
C. Endodermis
D. All

Answer

To answer the question regarding the initiation of lateral roots and vascular cambium during secondary growth in dicot roots, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Secondary Growth**:
- Secondary growth refers to the increase in thickness of roots and stems in plants, particularly in dicots. This growth is facilitated by specific types of meristematic tissues.

**Hint**: Remember that secondary growth is associated with an increase in girth, not length.

2. **Identifying Meristems Involved**:
- In dicots, two main lateral meristems are involved in secondary growth: the vascular cambium and the cork cambium. These meristems are responsible for producing new vascular tissues and protective tissues, respectively.

**Hint**: Think about what types of tissues are produced by these meristems.

3. **Role of the Pericycle**:
- The pericycle is a layer of cells located just inside the endodermis of roots. It plays a crucial role in the formation of lateral roots and vascular cambium during secondary growth.

**Hint**: The pericycle is a key player in root development; consider its position and function.

4. **Formation of Lateral Roots**:
- The pericycle cells can divide and differentiate to form lateral roots. This process typically occurs near the xylem elements of the root.

**Hint**: Lateral roots emerge from which specific layer of the root?

5. **Contribution to Vascular Cambium**:
- In addition to forming lateral roots, the pericycle also contributes to the formation of the vascular cambium, which is essential for secondary growth.

**Hint**: Think about how the pericycle interacts with other tissues during growth.

6. **Conclusion**:
- Therefore, the initiation of lateral roots and vascular cambium during secondary growth in dicot roots takes place by **pericycle cells**.

### Final Answer:
The correct answer is **pericycle**.