Different theories have been put forth to explain water translocation except

Options

A. Root Pressure
B. Capillarity
C. Cohesion theory
D. Pressure flow theory

Answer

To answer the question regarding the theories that explain water translocation in plants, we will analyze each of the given options step by step.

### Step-by-Step Solution:

1. **Understanding Water Translocation**:
Water translocation in plants primarily occurs through the xylem, which is responsible for transporting water and minerals from the roots to the leaves.

2. **Analyzing Root Pressure**:
- Root pressure is a phenomenon where water is pushed upward from the roots into the xylem vessels due to osmotic pressure.
- This is caused by the movement of water from areas of low solute concentration in the soil to areas of higher solute concentration in the root cells.
- **Conclusion**: Root pressure is a valid theory explaining water translocation.

3. **Analyzing Capillarity**:
- Capillarity refers to the ability of water to rise in narrow tubes due to adhesive and cohesive forces.
- In plants, the xylem vessels can be considered as capillary tubes, allowing water to move upward.
- **Conclusion**: Capillarity is also a valid theory for explaining water translocation.

4. **Analyzing Cohesion Theory**:
- Cohesion theory states that water molecules are attracted to each other (cohesion) and this property helps in the continuous column of water being pulled up through the xylem.
- This theory explains how water can travel long distances against gravity.
- **Conclusion**: Cohesion theory is a valid explanation for water translocation.

5. **Analyzing Pressure Flow Theory**:
- Pressure flow theory, also known as the mass flow hypothesis, primarily explains the movement of sugars in the phloem, not water in the xylem.
- It describes how sugars are transported from source (where they are produced) to sink (where they are used or stored) through the pressure gradient created in the phloem.
- **Conclusion**: Pressure flow theory does not explain water translocation.

### Final Answer:
The theory that does not explain water translocation is **Pressure Flow Theory**.

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