Give 2 important roles of abscisic acid .

Explanation

**Step-by-Step Solution:**

1. **Identify Abscisic Acid**: Abscisic acid (ABA) is a naturally occurring plant hormone that plays a crucial role in regulating various physiological processes in plants.

2. **Role in Leaf Senescence**: One important role of abscisic acid is to promote the senescence (aging and eventual falling off) of leaves. This process is vital for the plant to conserve resources, especially during unfavorable conditions.

3. **Role in Stomatal Closure**: Another significant role of abscisic acid is to stimulate the closure of stomata, which are small openings on the surface of leaves. This closure helps the plant to reduce water loss during times of drought or stress, thereby increasing its tolerance to adverse environmental conditions.

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