In stomata guard cells are

Options

A. special types of epidermal cells
B. special types of mesophyll cells
C. special types of palisade cells
D. special types of spongy cells

Answer

### Step-by-Step Text Solution:

1. **Understanding Stomata**: Stomata are small pore-like structures found on the surface of leaves and stems. They play a crucial role in the process of transpiration and gas exchange.

2. **Function of Stomata**: The primary functions of stomata include the loss of water vapor (transpiration) and the exchange of gases such as carbon dioxide (CO2) and oxygen (O2).

3. **Guard Cells**: Each stoma is surrounded by a pair of specialized cells known as guard cells. These cells are responsible for regulating the opening and closing of the stomatal pores.

4. **Nature of Guard Cells**: Guard cells are classified as a special type of epidermal cells. They are not mesophyll cells, palisade cells, or spongy cells.

5. **Structure of Guard Cells**: The inner walls of guard cells, which face the stomatal pore, are thick and elastic. This structure allows them to change shape when they gain or lose water.

6. **Mechanism of Opening and Closing**: When guard cells take in water, they become turgid (swollen), causing the stomata to open. Conversely, when they lose water, they become flaccid, leading to the closing of the stomata. This process typically occurs during the day when photosynthesis is active.

7. **Conclusion**: Therefore, the correct answer to the question is that guard cells are a special type of epidermal cells.

### Final Answer:
**Guard cells are special type of epidermal cells.**

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