Abscisic acid is called stress hormone as it

Options

A. Induces flowering
B. Breaks seed dormancy
C. Promotes leaf fall
D. Promotes stomatal closure.

Answer

**Step-by-Step Solution:**

1. **Understanding Abscisic Acid (ABA)**: Begin by recognizing that abscisic acid is a plant hormone. It plays a crucial role in various plant physiological processes.

2. **Role in Stress Response**: Abscisic acid is often referred to as the "stress hormone" because it is produced in response to environmental stress conditions such as drought, salinity, and extreme temperatures.

3. **Inducing Seed Dormancy**: One of the primary functions of abscisic acid is to induce seed dormancy. This means that ABA helps seeds to remain inactive and not germinate until conditions are favorable for growth, which is a protective mechanism during stressful conditions.

4. **Promoting Stomatal Closure**: Abscisic acid also promotes the closure of stomata, which are small openings on the leaf surface. This closure is particularly important during water stress, as it helps to reduce water loss through transpiration.

5. **Decreasing Transpiration Rate**: By inducing stomatal closure, abscisic acid effectively decreases the rate of transpiration. This is crucial for conserving water in times of drought or when the plant is under stress.

6. **Conclusion**: Therefore, abscisic acid is called the stress hormone because it helps plants cope with stressful environmental conditions by inducing seed dormancy and promoting stomatal closure to decrease transpiration.

**Final Answer**: Abscisic acid is called the stress hormone as it induces seed dormancy and promotes stomatal closure under water-stressful conditions to decrease the rate of transpiration.

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