Plant growth is

Options

A. Irreversible
B. Increase in size
C. Localised
D. All the above.

Answer

**Step-by-Step Solution:**

1. **Understanding Plant Growth**: Plant growth refers to the increase in size of various parts of the plant, such as roots, stems, and leaves. This growth is a fundamental characteristic of living organisms.

2. **Irreversible Change**: Growth in plants is an irreversible process. Once a plant part increases in size, it cannot return to its original size. This is a key feature of growth.

3. **Cellular Level Growth**: Growth occurs at the cellular level. When individual cells increase in size, the tissues made up of those cells also grow. This, in turn, leads to the growth of organs and organ systems.

4. **Localized Growth**: In plants, growth is not uniform throughout the organism. It occurs in specific regions known as meristems. These are areas where cells are actively dividing and differentiating.

5. **Types of Meristems**:
- **Primary Meristems**: These include the shoot apical meristem (SAM), located at the tip of the shoot, and the root apical meristem, located at the tip of the root. They are responsible for the elongation of the plant.
- **Secondary Meristems**: These contribute to the increase in girth of the plant, allowing it to grow thicker.

6. **Conclusion**: Given that plant growth is characterized by an irreversible increase in size, occurs at the cellular level, and is localized in specific regions (meristems), we can conclude that the correct description of plant growth aligns with these features.

**Final Answer**: Plant growth is an irreversible increase in size of an organ, localized in specific regions known as meristems.

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