Which of the following statement is not correct for the vacuoles?

Options

A. Contractile vacuoles are helpful in excretion
B. Usually tonoplast facilitates the transport of ions against the concentration gradient into the cytoplasm
C. Food vacuoles are formed by engulfing the food particles
D. Sap vacuole is bound by a single membrane

Answer

To determine which statement is not correct regarding vacuoles, let's analyze each option step by step.

### Step-by-Step Solution:

1. **Identify the Statements**: We need to evaluate the given statements about vacuoles. The statements are:
- A) Contractile vacuoles are helpful in excretion.
- B) Usually, tonoplast facilitates the transport of ions against the concentration gradient into the cytoplasm.
- C) Food vacuoles are formed by engulfing food particles.
- D) Sap vacuole is bound by a single membrane.

2. **Evaluate Statement A**:
- Contractile vacuoles are indeed involved in excretion and osmoregulation, especially in unicellular organisms like amoeba.
- **Conclusion**: This statement is correct.

3. **Evaluate Statement B**:
- The tonoplast is the membrane surrounding the vacuole in plant cells. It facilitates the transport of ions, but it does so into the vacuole, not into the cytoplasm.
- **Conclusion**: This statement is incorrect because it misstates the direction of ion transport.

4. **Evaluate Statement C**:
- Food vacuoles are formed when organisms like amoeba engulf food particles through a process called phagocytosis, which involves surrounding the food with pseudopodia and forming a vesicle.
- **Conclusion**: This statement is correct.

5. **Evaluate Statement D**:
- The sap vacuole in plant cells is indeed surrounded by a single membrane known as the tonoplast.
- **Conclusion**: This statement is correct.

6. **Final Conclusion**:
- The only statement that is not correct is Statement B. Therefore, the answer to the question is that Statement B is the incorrect statement regarding vacuoles.

### Summary of the Answer:
The statement that is not correct for the vacuoles is: "Usually, tonoplast facilitates the transport of ions against the concentration gradient into the cytoplasm."