Which one of the following does not cause opening of stomata?

Options

A. Internal clock
B. Light
C. High carbon dioxide concentrations
D. Movement of Kt into guard cells

Answer

To determine which factor does not cause the opening of stomata, let's analyze each option provided in the question step by step:

### Step-by-Step Solution:

1. **Understanding Stomata Function**: Stomata are small openings on the surface of leaves that regulate gas exchange and transpiration. Their opening and closing are influenced by various factors.

2. **Option Analysis**:
- **Internal Clock**: This refers to the plant's circadian rhythms, which can influence stomatal behavior but does not directly cause stomata to open or close. It mainly helps in timing the opening and closing based on the time of day.
- **Light**: Light is a significant factor that causes stomata to open. During the day, light stimulates the guard cells to take up potassium ions, leading to water influx and swelling, which opens the stomata.
- **High Carbon Dioxide Concentration**: An increase in carbon dioxide concentration leads to the closing of stomata. Therefore, it does not cause stomata to open.
- **Movement of Potassium Ions into Guard Cells**: The influx of potassium ions into guard cells is crucial for stomatal opening. It causes water to enter the guard cells, leading to their swelling and the opening of the stomata.

3. **Conclusion**: Among the options, the **internal clock** is the factor that does not directly cause the opening of stomata. While it plays a role in regulating when stomata should be open or closed, it does not actively cause the opening.

### Final Answer:
**The correct answer is: Internal Clock.**