If Levitt's hypothesis is to be believed , then the opening and closing of stomata take place as a result of …...... in and out of guard cells .

Options

A. Active transport of calcium ions
B. Active transport of potassium ions
C. Diffusion of potassium ions
D. Diffusion of calcium ions

Answer

**Step-by-Step Solution:**

1. **Understanding the Role of Stomata:**
- Stomata are small openings on the surface of leaves that allow for gas exchange (CO2 in and O2 out) during photosynthesis.

2. **Day and Night Functionality:**
- During the day, stomata are generally open to facilitate photosynthesis, while at night, they tend to close as photosynthesis ceases.

3. **Introduction to Levitt's Hypothesis:**
- Levitt proposed that the opening and closing of stomata are regulated by the movement of potassium ions (K+) in and out of guard cells.

4. **Mechanism of Stomatal Opening:**
- During the day, when photosynthesis occurs, there is an increase in the concentration of hydrogen ions (H+) in the guard cells due to the formation of organic acids.
- To balance the increase in H+ concentration, potassium ions (K+) move from the surrounding subsidiary cells into the guard cells.

5. **Water Movement and Turgidity:**
- As potassium ions enter the guard cells, water follows by osmosis to maintain osmotic balance. This influx of water causes the guard cells to swell and become turgid.

6. **Stomatal Opening:**
- The turgidity of the guard cells leads to the opening of the stomatal pore, allowing for gas exchange necessary for photosynthesis.

7. **Mechanism of Stomatal Closing:**
- At night, the concentration of H+ decreases, leading to a reduction in K+ entering the guard cells. Consequently, water exits the guard cells, causing them to become flaccid and the stomatal pore to close.

8. **Conclusion:**
- According to Levitt's hypothesis, the opening and closing of stomata are primarily due to the active transport of potassium ions in and out of the guard cells.

**Final Answer:**
- If Levitt's hypothesis is to be believed, then the opening and closing of stomata take place as a result of **potassium ions (K+) transport in and out of guard cells.**

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