Stomatal opening is under the control of

Options

A. Epidermal cells
B. Palisade cells
C. Spongy parenchyma cells
D. Guard cells

Answer

**Step-by-Step Solution:**

1. **Understanding Stomata**: Stomata are small openings found on the surface of leaves that facilitate gas exchange (CO2 and O2) and transpiration (water vapor loss).

2. **Identifying the Key Cells**: The stomatal pores are surrounded by specialized cells known as guard cells. These cells are crucial for the regulation of the stomatal opening and closing.

3. **Function of Guard Cells**: The primary function of guard cells is to control the size of the stomatal pore. This is achieved through changes in their turgidity (the state of being swollen due to high water content).

4. **Mechanism of Opening and Closing**:
- When guard cells absorb water, they become turgid (swollen), which causes them to bend and open the stomatal pore.
- Conversely, when guard cells lose water, they become flaccid (less swollen), leading to the collapse of their inner walls and the closing of the stomatal pore.

5. **Conclusion**: Therefore, the opening and closing of stomata are primarily controlled by the turgidity of guard cells. This regulation is essential for maintaining the plant's water balance and facilitating gas exchange.

**Final Answer**: Stomatal opening is under the control of **guard cells**.

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