During absorption of water by roots , the water potential of cell sap is lower than that of

Options

A. pure water and soil solution .
B. neither pure water nor soil solution .
C. pure water but higher than that of soil solution .
D. Soil solution but higher than that of pure water

Answer

### Step-by-Step Solution

1. **Understanding Water Potential**: Water potential is a measure of the potential energy in water, which determines the direction of water movement. It is influenced by solute concentration and pressure.

2. **Role of Root Hair Cells**: The primary site for water absorption in plants is the root hair cells. These cells have a large vacuole that stores cell sap, which contains various solutes.

3. **Mineral Absorption**: Root hair cells absorb minerals from the soil through active transport. This process requires energy (ATP) because it moves minerals against their concentration gradient.

4. **Hypertonic Solution**: As root hair cells absorb minerals, the concentration of solutes in the cell sap increases, making it hypertonic compared to the surrounding soil solution. This means the cell sap has a lower water potential.

5. **Osmosis**: Water moves from areas of higher water potential (more free water molecules) to areas of lower water potential (fewer free water molecules) through osmosis. Since the root hair cell has a higher concentration of solutes (due to mineral absorption), it has a lower water potential than the surrounding soil solution.

6. **Comparison with Pure Water**: Pure water has the highest water potential (0 MPa) because it contains no solutes. The cell sap in root hair cells, being hypertonic, will have a lower water potential than pure water as well.

7. **Conclusion**: Therefore, during the absorption of water by roots, the water potential of cell sap is lower than that of both pure water and the soil solution.

### Final Answer
The water potential of cell sap is lower than that of both pure water and soil solution.

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