All of the following statements are correct for guard cell except

Options

A. Bean shaped in dicots
B. Are green
C. Dumb-bell shaped in grasses
D. Outer walls are thick and the inner walls are thin

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 gas exchange and transpiration in plants.

2. **Structure of Guard Cells**:
- Guard cells are typically bean-shaped in dicots (two seed leaves).
- In grasses (monocots), guard cells are often described as dumbbell-shaped.

3. **Analyzing the Statements**:
- **Statement 1**: "Bean shaped in dicots" - This is correct. Guard cells in dicots are indeed bean-shaped.
- **Statement 2**: "They are green cells" - This is also correct as guard cells contain chloroplasts and are involved in photosynthesis.
- **Statement 3**: "Dumbbell shaped in grasses" - This is correct as well. In grasses, guard cells are typically dumbbell-shaped.
- **Statement 4**: "Their outer walls are thick and inner walls are thin" - This statement is incorrect. The outer walls of guard cells are actually thinner than the inner walls.

4. **Conclusion**:
- The only incorrect statement regarding guard cells is the fourth one, which states that their outer walls are thick and inner walls are thin. In reality, the inner walls are thick to facilitate the opening of the stomatal pore.

### Final Answer:
The statement that is incorrect about guard cells is: "Their outer walls are thick and inner walls are thin."

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