During secondary growth in a dicot root, cork cambium is formed by the activity of

Options

A. cortex
B. pericycle
C. Endodermis
D. hypodermis

Answer

### Step-by-Step Solution:

1. **Understanding Secondary Growth**: Secondary growth in plants refers to the increase in thickness or girth of the plant, primarily due to the activity of lateral meristems. In dicot roots, this is important for the plant's stability and nutrient transport.

2. **Identifying the Cambium**: The cork cambium, also known as phellogen, is a type of lateral meristem that produces cork cells (phellem) and contributes to the protective outer layer of the plant.

3. **Roots and Cambium**: It is essential to note that roots lack a traditional vascular cambium, which is typically found in stems. However, secondary growth still occurs through the activity of other tissues.

4. **Source of Cork Cambium**: In dicot roots, the cork cambium is formed from the pericycle, which is a layer of cells located just inside the endodermis. The pericycle can undergo dedifferentiation, allowing it to form new meristematic tissue, including the cork cambium.

5. **Conclusion**: Therefore, during secondary growth in a dicot root, the cork cambium is formed by the activity of the pericycle.

### Final Answer:
The cork cambium is formed by the activity of the **pericycle**.

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