Ascent of sap in tall trees is helped by

Options

A. Cohesion of water
B. Adhesion of water with walls of xylem
C. Transpiratory pull
D. All the above

Answer

### Step-by-Step Text Solution:

1. **Understanding Ascent of Sap**: The ascent of sap refers to the movement of water and dissolved minerals from the roots of a plant to its leaves. This process is crucial for the plant's survival and growth, especially in tall trees.

2. **Role of Transpiration**: Transpiration is the process through which water is lost from the plant, primarily through small openings in the leaves called stomata. This loss of water creates a negative pressure within the xylem vessels, which helps pull the sap upward.

3. **Cohesion and Adhesion Forces**:
- **Cohesion**: This is the force that holds water molecules together. Water molecules tend to stick to each other due to hydrogen bonding, forming a continuous column of water in the xylem vessels.
- **Adhesion**: This is the force that attracts water molecules to the walls of the xylem vessels. The interaction between water molecules and the xylem walls helps to counteract the force of gravity.

4. **Mechanism of Ascent**: As water evaporates from the leaves (transpiration), it creates a pull (negative pressure) that draws more water up from the roots through the xylem. The cohesion between water molecules ensures that the column of water remains intact, while adhesion helps the water to stay attached to the xylem walls.

5. **Conclusion**: The ascent of sap in tall trees is primarily facilitated by the combined effects of transpiration, cohesion, and adhesion. These forces work together to ensure that water and nutrients are effectively transported from the roots to the leaves.