The blockage of one or two tracheary elements in a tree may cause

Options

A. Breakage in the continuity water column
B. No breakage of continuity of water column and ascent of sap will take place
C. Breakage of cohesion force in water molecules
D. None of the above

Answer

### Step-by-Step Solution:

1. **Understanding Tracheary Elements**:
- Tracheary elements, which include tracheids and vessel elements, are part of the xylem tissue in plants. They are responsible for the conduction of water and minerals from the roots to the rest of the plant.

2. **Impact of Blockage**:
- When one or two tracheary elements are blocked, it is important to consider how this affects the overall water transport system in the plant.

3. **Water Column Continuity**:
- The water column in the xylem is maintained by cohesion and adhesion properties of water. A blockage in one or two tracheary elements does not necessarily break the continuity of the water column because there are usually many other tracheary elements that can compensate for the blockage.

4. **Ascent of Sap**:
- The ascent of sap refers to the upward movement of water and dissolved nutrients from the roots to the leaves. Even with one or two blocked tracheary elements, the overall ascent of sap can still occur through the remaining functional elements.

5. **Evaluating the Options**:
- **Option A**: Breakage in the continuity of water column - This is incorrect because the continuity is maintained by other tracheary elements.
- **Option B**: No breakage of continuity of the water column and ascent of sap will take place - This is correct as the remaining elements can still transport water.
- **Option C**: Breakage of cohesion force in water molecule - This is incorrect as the cohesion forces are not broken by the blockage of a few elements.
- **Option D**: None of the above - This is also incorrect since option B is correct.

6. **Conclusion**:
- The blockage of one or two tracheary elements in a tree may cause no breakage of continuity of the water column, and the ascent of sap will still take place. Therefore, the correct answer is **Option B**.