Which one is stress hormone -

Options

A. ABA
B. `C_2 H_4`
C. `GA_7`
D. `IA A`

Answer

**Step-by-Step Solution:**

1. **Identify the Options**: The question provides four options:
- Option 1: ABA (Abscisic Acid)
- Option 2: C2H4 (Ethylene)
- Option 3: GA7 (Gibberellic Acid)
- Option 4: IAA (Indole-3-Acetic Acid)

2. **Understand Plant Hormones**: All the options listed are plant growth regulators, also known as phytohormones. These hormones are produced by plants to regulate various physiological processes.

3. **Classify Plant Hormones**: Plant hormones can be categorized into two groups:
- **Plant Growth Promoters**: These include auxins (like IAA), gibberellins (like GA7), and cytokinins, which promote growth.
- **Plant Growth Inhibitors**: These include hormones that inhibit growth, such as abscisic acid (ABA).

4. **Focus on Stress Response**: Among the plant growth inhibitors, abscisic acid (ABA) is specifically known for its role in plant responses to stress conditions, such as drought or injury. It helps in processes like stomatal closure to reduce water loss.

5. **Conclude the Answer**: Given that ABA (Abscisic Acid) is recognized as the primary stress hormone in plants, the correct answer to the question "Which one is a stress hormone?" is **Option 1: ABA (Abscisic Acid)**.

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