Which of the following facilitates opening of stomatal aperture ?

Options

A. Contraction of outer wall of guard cells
B. Decreases in turgidity of guard cells
C. Radial orientation of cellulose microfibrils in the cell wall of guard cells
D. Longitudinal orientation of cellulose microfibrils in the cell wall of guard cells

Answer

To solve the question "Which of the following facilitates opening of stomatal aperture?" we will analyze the options provided and determine which one is correct based on our understanding of guard cells and their function in stomatal movement.

### Step-by-Step Solution:

1. **Understanding Stomata**:
- Stomata are small openings found on the epidermis of leaves and young stems that allow for gas exchange. Each stoma is surrounded by two specialized cells known as guard cells.

2. **Role of Guard Cells**:
- Guard cells are responsible for the opening and closing of stomata. They have a unique shape (kidney or bean-shaped) and contain chloroplasts, which allow them to perform photosynthesis.

3. **Analyzing the Options**:
- **Option A: Contraction of outer wall of guard cells**: This option suggests that the contraction of the outer wall facilitates the opening of the stomatal aperture. However, this is not correct as the opening occurs when guard cells swell due to turgor pressure.

- **Option B: Decrease in turgidity of guard cells**: This option implies that a decrease in turgidity would lead to the opening of stomata. This is incorrect because stomata open when guard cells become turgid (swollen with water).

- **Option C: Radial orientation of cellulose microfibrils in the cell wall of guard cells**: This option states that the radial orientation of cellulose microfibrils facilitates the opening of stomatal apertures. This is correct because the radial arrangement allows the guard cells to expand outward when they take up water, leading to the opening of the stomata.

- **Option D: Longitudinal orientation of cellulose microfibrils in the cell wall of guard cells**: This option is incorrect because the longitudinal orientation would not facilitate the outward expansion necessary for stomatal opening.

4. **Conclusion**:
- The correct answer is **Option C: Radial orientation of cellulose microfibrils in the cell wall of guard cells**. This orientation allows the guard cells to expand and thus open the stomatal aperture.