Define senescence in plants. Name its different types.

Explanation

**Step-by-Step Solution:**

1. **Definition of Senescence in Plants:**
- Senescence in plants refers to the process of aging that occurs after a plant reaches reproductive maturity and continues until its death. It is characterized by a series of physiological changes that lead to the deterioration of plant tissues and ultimately the plant itself.

2. **Understanding the Process:**
- During senescence, various parts of the plant, such as leaves, flowers, and fruits, undergo changes that lead to their eventual shedding. This process is often regulated by phytohormones, particularly abscisic acid, which plays a crucial role in initiating and promoting senescence in mature leaves.

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