The water potential in guard cells during day time in photoactive stomata

Options

A. Initially decreases and later increases
B. Initially increases and later decreases
C. Increases at all times
D. Decreases at all times

Answer

**Step-by-Step Solution:**

1. **Understanding Guard Cells**: Guard cells are specialized cells that surround the stomata (the pores on the leaf surface) and are responsible for regulating their opening and closing. This regulation is crucial for gas exchange and transpiration in plants.

2. **Photoactive Stomata**: The term "photoactive" refers to the stomata being active during the daytime when photosynthesis occurs. During this time, the plant needs to take in carbon dioxide for photosynthesis, which requires the stomata to be open.

3. **Water Loss During Daytime**: When stomata are open, water vapor escapes from the plant through transpiration. This loss of water leads to a decrease in the water potential within the guard cells.

4. **Water Potential Dynamics**: Initially, during the daytime, the water potential in the guard cells decreases due to the loss of water as the stomata remain open. However, if conditions change (like reduced light or humidity), the guard cells may take up water again, leading to an increase in water potential later on.

5. **Evaluating the Options**: The question provides several options regarding the changes in water potential:
- Initially decreases and later increases: This is correct as explained.
- Initially increases and later decreases: This is incorrect because water potential does not initially increase.
- Increases at all times: This is incorrect as water potential decreases during the day.
- Decreases at all times: This is also incorrect as water potential can increase later.

6. **Conclusion**: The correct answer is that the water potential in guard cells during daytime in photoactive stomata initially decreases and later may increase.

**Final Answer**: Initially decreases and later increases.

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