Accumulation of which one of the following acids results in closure of stomata

Options

A. Malic acid
B. Aspertic acid
C. PEP
D. OAA.

Answer

To solve the question regarding which acid's accumulation results in the closure of stomata, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Stomata Function**:
- Stomata are small openings on the surfaces of leaves that allow for gas exchange (CO2 in, O2 out) and transpiration (water vapor loss).
- The opening and closing of stomata are regulated by guard cells.

**Hint**: Remember that stomata play a crucial role in gas exchange and water regulation in plants.

2. **Identifying the Role of Acids**:
- When plants experience stress conditions, such as water loss, they need to conserve water. This is where the accumulation of certain acids comes into play.
- The accumulation of specific acids in guard cells can lead to their closure.

**Hint**: Think about what happens in plants during adverse conditions and how they respond to conserve water.

3. **Evaluating the Options**:
- **Malic Acid**: Known to accumulate in guard cells and is associated with the closure of stomata during water stress.
- **Aspartic Acid**: Primarily involved in hormone production and does not directly relate to stomatal closure.
- **Phosphoenolpyruvate (PEP)**: An intermediate in glycolysis, not directly related to stomatal function.
- **Oxaloacetic Acid (OAA)**: An intermediate in the Krebs cycle, also not related to stomatal closure.

**Hint**: Analyze the functions of each acid and how they relate to the stomatal mechanism.

4. **Conclusion**:
- Based on the evaluation, malic acid is the acid that, when accumulated, leads to the closure of stomata in response to water stress.

**Hint**: Focus on the specific acid that is linked to the physiological response of guard cells in the context of stomatal regulation.

### Final Answer:
The accumulation of **malic acid** results in the closure of stomata.