The hormone which reduces transpiration rate by inducing stomatal closure is

Options

A. ABA
B. ethylene
C. cytokinin
D. gibberellin

Explanation

To answer the question, "The hormone which reduces transpiration rate by inducing stomatal closure is," we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Options**: The options provided are:
- A) Abscisic acid
- B) Ethylene
- C) Cytokinin
- D) Gibberellin

2. **Understand the Function of Each Hormone**:
- **Abscisic Acid**: Known as the stress hormone, it plays a crucial role in plant responses to stress, particularly drought. It induces stomatal closure, which reduces transpiration.
- **Ethylene**: Primarily involved in fruit ripening and responses to stress but does not directly induce stomatal closure.
- **Cytokinin**: Promotes cell division and growth; it does not reduce transpiration.
- **Gibberellin**: Promotes stem elongation and seed germination; it does not have a role in reducing transpiration.

3. **Analyze the Role of Abscisic Acid**:
- Abscisic acid concentration increases during stress conditions such as drought. This increase leads to the closure of stomata, which are small openings on the leaf surface that allow for gas exchange and transpiration.

4. **Conclude the Answer**:
- Since abscisic acid is the only hormone that induces stomatal closure and thereby reduces transpiration, the correct answer is **A) Abscisic acid**.

### Final Answer:
The hormone which reduces transpiration rate by inducing stomatal closure is **Abscisic acid**.

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