Which of the following is a cytokinin ?

Options

A. Phytochrome
B. Leucine
C. Ethylene
D. Zeatin.

Answer

To determine which of the following options is a cytokinin, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Cytokinins**: Cytokinins are a class of plant hormones that play a crucial role in promoting cell division and growth in plants. They are involved in various physiological processes, such as shoot formation and delaying leaf senescence.

2. **Review the Options Given**: The options provided are:
- A) Phytochrome
- B) Leucine
- C) Ethylene
- D) Zeatin

3. **Analyze Each Option**:
- **Phytochrome**: This is a photoreceptor in plants that helps in sensing light. It is not a cytokinin.
- **Leucine**: This is an amino acid and not a plant hormone. Therefore, it is not a cytokinin.
- **Ethylene**: This is a gaseous plant hormone involved in fruit ripening and other processes but is not classified as a cytokinin.
- **Zeatin**: This is a type of cytokinin that is naturally occurring in plants, particularly found in maize and coconut milk. It is known to promote cell division.

4. **Identify the Correct Answer**: Based on the analysis, the only option that is a cytokinin is **D) Zeatin**.

### Final Answer:
The cytokinin among the options is **D) Zeatin**.

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