Most of the water lost by the plant through transpiration exist through the stomatal pores . Which of the following statements about transpiration and stomatal functioning is false ?

Options

A. Stomata normally open in response to a shift from dark to light conditions
B. When the turgor pressure of guard cells increases , the stomatal aperture opens
C. With the shift from dark to light , the osmotic potential becomes less negative resulting in stomatal closure
D. The turgor pressure of guard cells increases after the osmotic potential becomes more negative

Answer

To determine which statement about transpiration and stomatal functioning is false, we need to analyze the behavior of guard cells under different light conditions and how it affects stomatal opening and closing.

### Step-by-Step Solution:

1. **Understand the Role of Stomata**: Stomata are small openings on the surface of leaves that allow for gas exchange and transpiration. The opening and closing of stomata are controlled by guard cells.

2. **Behavior in Dark Conditions**: In the dark, guard cells lose water, become flaccid, and as a result, the stomata close. This is a mechanism to conserve water when photosynthesis is not occurring.

3. **Behavior in Light Conditions**: In light, guard cells take up water through osmosis, become turgid (swollen), and the stomata open. This allows for gas exchange necessary for photosynthesis.

4. **Evaluate the Statements**:
- **Statement 1**: If there is a shift from dark to light conditions, the stomata will open. This is true because guard cells become turgid in light.
- **Statement 2**: When the turgor pressure of guard cells increases, the stomatal aperture opens. This is also true as increased turgor pressure leads to stomatal opening.
- **Statement 3**: When there is a shift from dark to light, the osmotic potential becomes less negative. This statement is false. In fact, the osmotic potential becomes more positive, which results in stomatal opening.
- **Statement 4**: The turgor pressure of guard cells increases after the osmotic potential becomes more negative. This statement is true because as water enters the guard cells, their turgor pressure increases.

5. **Identify the False Statement**: The false statement among the options is the one that claims that with the shift from dark to light, the osmotic potential becomes less negative resulting in stomatal closure. This is incorrect; it actually leads to stomatal opening.

### Conclusion:
The false statement regarding transpiration and stomatal functioning is that with the shift from dark to light, the osmotic potential becomes less negative resulting in stomatal closure.

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