Stomata generally open during the day because the guard cells have

Options

A. Outer thin wall
B. Chlorophyll
C. Kidney-shape
D. Larger nuclei

Answer

**Step-by-Step Solution:**

1. **Understanding the Structure of Stomata:**
- Stomata are small openings on the surface of leaves, primarily surrounded by a pair of specialized cells known as guard cells.

2. **Role of Guard Cells:**
- The primary function of guard cells is to regulate the opening and closing of stomata, which controls gas exchange and water loss in plants.

3. **Presence of Chlorophyll:**
- Guard cells contain chlorophyll, which is essential for photosynthesis. During the day, when light is available, chlorophyll absorbs light energy to drive the process of photosynthesis.

4. **Photosynthesis and Organic Compounds:**
- During photosynthesis, chlorophyll facilitates the conversion of carbon dioxide and water into glucose (sugar) and oxygen. This process also leads to the production of organic acids and salts.

5. **Impact on Water Potential:**
- The accumulation of sugars and organic salts in the guard cells increases their concentration, which decreases the water potential inside the guard cells.

6. **Water Movement:**
- Due to the lower water potential inside the guard cells compared to the outside, water moves into the guard cells from the surrounding cells through osmosis.

7. **Turgidity of Guard Cells:**
- As water enters the guard cells, they swell and become turgid. This turgidity is crucial for the opening of the stomata.

8. **Opening of Stomata:**
- When the guard cells are turgid, they bow outward, causing the stomatal pore to open. This allows for gas exchange (CO2 in, O2 out) and transpiration to occur.

9. **Conclusion:**
- Therefore, stomata generally open during the day because the guard cells have chlorophyll, which enables photosynthesis, leading to the accumulation of organic compounds that create a water potential gradient, resulting in the turgidity of guard cells and the opening of stomata.

**Final Answer:**
Stomata generally open during the day because the guard cells have chlorophyll.

---