Water will be absorbed by root hairs when the external medium is

Options

A. Hypotonic
B. Hypertonic
C. Isotonic
D. Viscous.

Answer

**Step-by-Step Solution:**

1. **Understanding the Context**: Water absorption by root hairs is influenced by the concentration of solutes in the external medium compared to the concentration of solutes inside the root hairs.

2. **Identifying the Types of Solutions**:
- **Hypotonic Solution**: A solution with a lower concentration of solutes compared to another solution (in this case, the inside of the root hairs).
- **Hypertonic Solution**: A solution with a higher concentration of solutes compared to another solution.
- **Isotonic Solution**: A solution with the same concentration of solutes as another solution.
- **Viscous**: Refers to the thickness or stickiness of a fluid, not directly related to solute concentration.

3. **Analyzing Water Movement**: Water moves from areas of higher concentration (more water, less solute) to areas of lower concentration (less water, more solute) through a process called osmosis.

4. **Applying the Concept to Root Hairs**:
- When the external medium is hypotonic, it has a lower concentration of solutes than the root hairs. This causes water to move into the root hairs from the soil.
- This movement is termed **endosmosis**, where water enters the cell.

5. **Conclusion**: Therefore, water will be absorbed by root hairs when the external medium is hypotonic.

**Final Answer**: Water will be absorbed by root hairs when the external medium is hypotonic.

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