Tonoplast is a

Options

A. Plasma membrane
B. Vacuolar membrane
C. Cytoplasmic membrane
D. all of these

Answer

**Step-by-Step Solution:**

1. **Understanding the Context**: The question is about the term "Tonoplast." To answer this, we need to understand what Tonoplast is and its role in plant cells.

2. **Identifying Tonoplast**: Tonoplast is the membrane that surrounds the large central vacuole found in mature plant cells. This vacuole is significant as it occupies a large volume within the cell.

3. **Function of Tonoplast**: The primary function of the tonoplast is to maintain turgor pressure within the plant cell. Turgor pressure is essential for keeping the plant rigid and helps it maintain its shape. It does this by pressing the plasma membrane against the cell wall.

4. **Structure of Tonoplast**: The tonoplast is composed of a lipid bilayer, similar to other cellular membranes, but it is specifically referred to as the vacuolar membrane because it surrounds the vacuole.

5. **Conclusion**: Based on the above points, we can conclude that the tonoplast is indeed a vacuolar membrane that plays a crucial role in the physiology of plant cells.

6. **Final Answer**: Therefore, the correct answer to the question "Tonoplast is a" is that it is a **vacuolar membrane**.

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