The pressure develop in xylem in herbs and in tall trees respectively during ascent of sap

Options

A. Positive, positive
B. Negative, negative
C. Positive, negative
D. Negative, positive

Answer

To answer the question regarding the pressure developed in the xylem during the ascent of sap in herbs and tall trees, we can break down the explanation into several steps:

### Step-by-Step Solution:

1. **Understanding Ascent of Sap**:
- The ascent of sap refers to the movement of water and dissolved minerals from the roots to the leaves of a plant. This process is crucial for plant nutrition and hydration.

2. **Types of Pressure Involved**:
- There are two main types of pressures that facilitate the ascent of sap:
- **Adhesion Pressure**: This is the pressure that arises due to the attraction between water molecules and the xylem walls.
- **Cohesion Pressure**: This is the pressure resulting from the attraction between water molecules themselves.

3. **Pressure in Herbs**:
- In herbaceous plants (herbs), the pressure developed in the xylem is **positive**. This is because the water is pushed upward due to root pressure, which is generated when water is absorbed by the roots.

4. **Pressure in Tall Trees**:
- In tall trees, the pressure developed in the xylem is **negative**. This is due to the process of transpiration, where water evaporates from the leaves, creating a negative pressure that pulls water upward against gravity.

5. **Conclusion**:
- Therefore, the pressure developed in the xylem during the ascent of sap is **positive in herbs** and **negative in tall trees**.

### Final Answer:
- The pressure developed in xylem in herbs is **positive**, and in tall trees, it is **negative**.

---