In dicot root, cambium develops from secondary meristem. First to happen during secondary growth is

Options

A. cambium becomes active below phloem
B. conjunctive tisse inner to pheloem gets active
C. cambium develops from pericycle opposite to protoxylem
D. a wavy ring of cambium develops.

Answer

To answer the question regarding the first event that occurs during secondary growth in a dicot root, we can break down the process step by step.

### Step-by-Step Solution:

1. **Understanding Cambium**: Cambium is a layer of actively dividing cells located between the xylem and phloem. It plays a crucial role in secondary growth, allowing the plant to increase in thickness.

2. **Initial Condition in Dicot Roots**: In the initial stages of a dicot root, cambium is absent. The vascular bundles, which consist of xylem and phloem, are arranged radially.

3. **First Event in Secondary Growth**: The first event that occurs during secondary growth is the activation of parenchyma cells. These cells are located interior to the phloem.

4. **Meristematic Activity**: The parenchyma cells that are activated become meristematic, meaning they start to divide actively. This is crucial for the formation of cambium.

5. **Formation of Cambium Stripes**: Following the activation of parenchyma cells, four separate stripes of cambium begin to form. This occurs as the meristematic cells proliferate.

6. **Development of Continuous Cambium**: Eventually, these four stripes of cambium will connect laterally to form a continuous cambium ring.

7. **Location of Cambium**: The cambium ring is located below the phloem and above the protoxylem, contributing to the secondary growth of the root.

8. **Conclusion**: Therefore, the first event to happen during secondary growth in a dicot root is the activation of the parenchyma cells located interior to the phloem.

### Final Answer:
The first event to happen during secondary growth in a dicot root is the activation of the parenchyma cells that are located interior to the phloem.

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