Which of the following contributes most to transport of water from the ground to the leaves of a tall tree ?

Options

A. Break down of ATP
B. Root pressure
C. Capillary rise of water in xylem
D. Cohesion of water and transpiration pull

Answer

To determine which factor contributes most to the transport of water from the ground to the leaves of a tall tree, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Process of Water Transport in Plants**:
Water is absorbed by the roots from the soil and needs to travel up through the plant to reach the leaves.

2. **Identify the Mechanisms of Water Transport**:
The main mechanisms involved in the transport of water in plants include:
- Cohesion
- Adhesion
- Transpiration
- Root pressure
- Capillary action

3. **Focus on Cohesion and Transpiration**:
- **Cohesion** refers to the attraction between water molecules, which helps to maintain a continuous column of water in the xylem vessels.
- **Transpiration** creates a negative pressure (transpiration pull) in the leaves, which pulls water upward from the roots through the xylem.

4. **Evaluate Other Options**:
- **Root Pressure**: This is a minor contributor, especially in tall trees, as it primarily affects water movement in smaller plants.
- **Capillary Action**: While it plays a role in water movement, it is not the primary mechanism in tall trees.
- **Breakdown of ATP**: This is related to energy processes in cells, not directly to water transport.

5. **Conclusion**:
The primary contributors to the transport of water from the ground to the leaves of a tall tree are the cohesion of water molecules and the transpiration pull. Therefore, the correct answer is that the **cohesion of water and transpiration pull** contribute most to this process.

### Final Answer:
The cohesion of water molecules and the transpiration pull are the main contributors to the transport of water from the ground to the leaves of a tall tree.

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