Which is not true for abscisic acid?

Options

A. Acts as antitranspirant
B. Synthesized in chloroplast from carotenoids
C. Increases stress tolerance in plants
D. Induce epinasty of leaves and flowers

Answer

To determine which statement about abscisic acid (ABA) is not true, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Abscisic Acid (ABA)**:
- Abscisic acid is a plant hormone that plays a crucial role in various plant processes, particularly in response to stress conditions.

2. **Analyzing Each Option**:
- **Option 1**: "Acts as a trans anti-transpirant."
- This statement is true. ABA is known to reduce transpiration by closing stomata, which helps the plant conserve water during drought conditions.

- **Option 2**: "Synthesized in chloroplasts and carotenoids."
- This statement is also true. ABA is synthesized in the chloroplasts from carotenoid precursors, particularly during stress conditions.

- **Option 3**: "Increases stress tolerance in plants."
- This statement is true. ABA is often referred to as a stress hormone because it helps plants cope with various stresses, including drought and salinity.

- **Option 4**: "Induces happiness of leaves and flowers."
- This statement is not true. The term "happiness" in this context likely refers to "hygroscopicity," which is the drooping of leaves. However, it is ethylene, not abscisic acid, that is responsible for leaf abscission and the drooping of leaves.

3. **Conclusion**:
- The statement that is not true for abscisic acid is **Option 4: "Induces happiness of leaves and flowers."**

### Final Answer:
The correct answer is **Option 4**.

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