The primary reason for a passive flow of water from soil into the atmosphere through the plant body is

Options

A. Cohesive forces
B. Adhesive forces
C. Tension
D. Water potential gradient

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the primary reason behind the passive flow of water from the soil into the atmosphere through the plant body.

2. **Identifying the Process**: Water enters the plant through the roots, which are in contact with the soil. This process is passive, meaning it does not require energy input from the plant.

3. **Water Potential Concept**: Water moves from areas of higher water potential to areas of lower water potential. Water potential is a measure of the potential energy of water in a system, which influences the direction of water movement.

4. **Water Potential in Soil and Roots**: In this scenario, the soil has a higher water potential compared to the roots of the plant. This difference in water potential drives the movement of water from the soil into the roots.

5. **Transpiration and Water Movement**: Once water enters the roots, it moves upward through the plant and eventually evaporates into the atmosphere. This upward movement is facilitated by transpiration, which creates a negative pressure (tension) in the xylem vessels.

6. **Final Conclusion**: The primary reason for the passive flow of water from the soil into the atmosphere through the plant body is the water potential gradient. Water moves from an area of higher water potential (soil) to an area of lower water potential (roots and then leaves).

### Answer:
The primary reason for a passive flow of water from soil into the atmosphere through the plant body is the **water potential gradient**.

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