Which of the following is not the least convincing in the imbibtional theory of ascent of sap

Options

A. The imbibitional force is very high from 100-1000 atm
B. The imbibitional force can raise the water to a height of 200'-400' .i.e. the tallest tree
C. The movement of water is along the walls of the xylem vessels and not through the lumen (cavity) of the vessels
D. The movement of water, no doubt is slow, but to some extent can keep pace with tranpiration

Answer

To determine which of the following statements is not the least convincing in the imbibitional theory of ascent of sap, we need to analyze each option based on our understanding of the theory and the role of xylem in water transport in plants.

### Step-by-Step Solution:

1. **Understanding Imbibitional Theory**:
- The imbibitional theory suggests that water is absorbed by plant tissues through imbibition, which is the process of water being drawn into the plant cells due to the attraction between water molecules and the cell walls.
- This theory is one of the mechanisms that explain how water moves through plants, particularly through the xylem vessels.

2. **Role of Xylem**:
- Xylem is the tissue responsible for the conduction of water and minerals from the roots to the rest of the plant.
- Xylem vessels are crucial for this process, and water movement primarily occurs along the walls of these vessels rather than through their lumen.

3. **Analyzing the Options**:
- **Option 1**: "Imbibitional force is very high from 100 to 1000."
- This is incorrect because imbibitional forces are relatively low and cannot be quantified as high.
- **Option 2**: "Imbibitional force can raise the water to a height of 200 to 400, the tallest tree."
- This is also incorrect because imbibitional forces alone cannot raise water to such heights; transpiration pull is a more significant factor.
- **Option 3**: "Movement of water is along the walls of the xylem vessel and not through the lumen or the cavity of the vessel."
- This statement is correct and aligns with the understanding of how water moves through xylem.
- **Option 4**: "Movement of water no doubt is slow but to some extent can keep pace with the transpiration."
- This is misleading because while the movement of water is slow, it does not keep pace with the rapid rate of transpiration.

4. **Conclusion**:
- The most convincing statement regarding the imbibitional theory of ascent of sap is **Option 3**: "Movement of water is along the walls of the xylem vessel and not through the lumen or the cavity of the vessel."

### Final Answer:
**Option 3** is the most convincing statement in the imbibitional theory of ascent of sap.

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