What is true ?

Options

A. ABA opens stomata
B. ABA opens stomata while cytokinin closes stomata
C. ABA closes while cytokinin opens stomata
D. ABA and cytokinin do not affect stomata

Answer

To determine which statement is true regarding the effects of abscisic acid (ABA) and cytokinin on stomata, we can analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding ABA (Abscisic Acid)**:
- ABA is a plant hormone known as an anti-transpirant.
- Its primary function is to induce seed dormancy and reduce transpiration by causing the closure of stomata during stress conditions.

2. **Understanding Cytokinin**:
- Cytokinin is another plant hormone that acts as an antagonist to ABA.
- It promotes cell division and growth and is known to open stomata, especially when the plant is recovering from stress.

3. **Analyzing the Statements**:
- **Statement 1**: "ABA opens the stomata."
- This is **false**. ABA actually causes the stomata to close.
- **Statement 2**: "ABA opens stomata while cytokinin closes the stomata."
- This is **false**. ABA closes the stomata, and cytokinin opens them.
- **Statement 3**: "ABA closes while cytokinin opens the stomata."
- This is **true**. ABA indeed causes stomatal closure, while cytokinin promotes stomatal opening.
- **Statement 4**: "ABA and cytokinin do not affect the stomata."
- This is **false**. Both hormones have significant effects on stomatal behavior.

4. **Conclusion**:
- The only true statement among the options provided is **Statement 3**: "ABA closes while cytokinin opens the stomata."

### Final Answer:
The correct option is **Statement 3**.