Choose the correct statement(s) regarding guard cells control.
Intensity of light entering
Photosynthesis
Closing and opening of stomata
Change in green colour

Options

A. I and II
B. Only III
C. I and IV
D. I,II and III

Answer

To solve the question regarding the functions controlled by guard cells, let's analyze each statement step by step:

### Step-by-Step Solution:

1. **Understanding Guard Cells**:
- Guard cells are specialized cells located around the stomata (tiny openings on the leaf surface) that regulate their opening and closing.
- They play a crucial role in controlling gas exchange and transpiration in plants.

2. **Evaluating the Statements**:
- **Statement 1: Intensity of light entering**:
- While light intensity can influence the opening of stomata, it is not directly controlled by guard cells. Instead, it affects the guard cells' behavior.
- **Statement 2: Photosynthesis**:
- Photosynthesis occurs in the presence of light and involves gas exchange (CO2 intake and O2 release) through stomata. However, photosynthesis is not a direct function of guard cells; rather, it is a process that is influenced by the opening of stomata.
- **Statement 3: Closing and opening of stomata**:
- This is the primary function of guard cells. They control the stomatal aperture, which regulates gas exchange and transpiration.
- **Statement 4: Change in green color**:
- The green color of leaves is due to chlorophyll and is not controlled by guard cells. This statement is unrelated to the function of guard cells.

3. **Conclusion**:
- After evaluating all the statements, the only correct statement regarding the function controlled by guard cells is the third one: **Closing and opening of stomata**.

### Final Answer:
The correct statement regarding guard cells control is: **Closing and opening of stomata**.

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