Interfascicular cambium formation is induced by

Options

A. Auxin
B. Cytokinin
C. Gibberellin
D. Ethylene.

Answer

### Step-by-Step Solution:

1. **Understanding Interfascicular Cambium**:
- Interfascicular cambium is a type of cambium that forms between the vascular bundles in dicotyledonous plants. It plays a crucial role in secondary growth, contributing to the increase in girth of the plant.

2. **Identifying Plant Hormones**:
- The question provides four options: auxin, cytokinin, gibberellin, and ethylene. We need to analyze each hormone's role in plant growth and development, particularly in relation to cambium formation.

3. **Analyzing Auxin**:
- Auxin is known for promoting cell growth and elongation. However, it is not specifically involved in the formation of interfascicular cambium. Therefore, this option can be eliminated.

4. **Analyzing Cytokinin**:
- Cytokinins are plant hormones that promote cell division and are essential for various growth processes. Kinetin, a type of cytokinin, has been shown to induce the formation of interfascicular cambium. This makes cytokinin a strong candidate for the correct answer.

5. **Analyzing Gibberellin**:
- Gibberellins are involved in regulating growth, organ development, and responses to environmental stimuli. However, they do not play a direct role in the formation of interfascicular cambium, so this option can also be eliminated.

6. **Analyzing Ethylene**:
- Ethylene is a gaseous hormone that primarily influences processes such as seed germination, fruit ripening, and leaf abscission. It does not induce cambium formation, making this option incorrect as well.

7. **Conclusion**:
- After analyzing all the options, the correct answer is that interfascicular cambium formation is induced by **cytokinin**, specifically by **kinetin**.

### Final Answer:
Interfascicular cambium formation is induced by **kinetin**, which is a type of cytokinin.

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