Which wall of the guard cells is thickened?

Options

A. Lateral
B. Inner
C. Outer
D. All of these

Answer

**Step-by-Step Solution:**

1. **Understanding Guard Cells**: Guard cells are specialized cells that surround the stomata (the pores on the leaf surface). Their primary function is to regulate the opening and closing of these stomata, which is crucial for gas exchange and transpiration in plants.

2. **Structure of Guard Cells**: Each guard cell has three main walls: the inner wall, the outer wall, and the lateral walls. The inner wall is the one that faces the stomatal pore, while the outer wall is on the opposite side.

3. **Thickening of Walls**: Among these walls, the inner wall of the guard cells is thickened. This thickening is important because it allows the guard cells to change shape effectively when they gain or lose turgor pressure, which in turn opens or closes the stomata.

4. **Functionality**: When the guard cells take up water and become turgid, the inner thickened walls help them to bulge outward, causing the stomata to open. Conversely, when the guard cells lose water and become flaccid, the stomata close.

5. **Conclusion**: Therefore, the correct answer to the question "Which wall of the guard cells is thickened?" is the inner wall of the guard cells.

**Final Answer**: The inner wall of the guard cells is thickened.

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