Which contributes most to the transport of water from the soil to the leaves of a tree ?

Options

A. Root pressure
B. Cohesion of water and transpiration pull
C. Capillary rise of water inside xylem
D. Hydrolysis of ATP

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which mechanism contributes most to the transport of water from the soil to the leaves of a tree. The options provided include root pressure, cohesion of water and transpiration pull, capillary rise of water inside xylem, and hydrolysis of ATP.

2. **Analyzing the Options**:
- **Root Pressure**: This is the pressure exerted in the roots of plants that helps push water upward. However, it is not the primary force for tall trees.
- **Cohesion of Water and Transpiration Pull**: Cohesion refers to the attraction between water molecules, which helps maintain a continuous column of water in the xylem. Transpiration pull is the force generated when water evaporates from the leaves, creating a negative pressure that pulls water upward from the roots.
- **Capillary Rise of Water Inside Xylem**: This refers to the ability of water to move upward through small tubes (xylem vessels) due to adhesion and cohesion but is not the main driving force for tall trees.
- **Hydrolysis of ATP**: This is a chemical process that provides energy for many cellular processes but does not directly contribute to water transport in plants.

3. **Identifying the Correct Answer**: The combination of cohesion of water and transpiration pull works together to effectively transport water from the roots to the leaves. The transpiration pull is particularly significant in tall trees, as it creates a negative pressure that draws water upward.

4. **Conclusion**: Therefore, the correct answer is **cohesion of water and transpiration pull** (Option B), as these two mechanisms work together to facilitate the movement of water from the soil through the plant to the leaves.