What is correct about root pressure ?

Options

A. Provides a modest push in the over all process of water transport
B. Play a major role in water movement in tall trees
C. Is not observable at night
D. Cannot explain the loss of impure water from hydathodes

Answer

### Step-by-Step Solution for the Question: What is correct about root pressure?

1. **Definition of Root Pressure**:
- Root pressure is defined as the positive pressure that develops in the roots of plants due to the active absorption of water and nutrients from the soil.

2. **Mechanism of Active Absorption**:
- The roots, particularly through root hairs, actively absorb nutrients and water from the soil. This active absorption process requires energy and is crucial for the plant's nutrient uptake.

3. **Formation of Pressure**:
- As water is absorbed, it increases the pressure within the xylem vessels of the plant. This increase in pressure is what we refer to as root pressure.

4. **Movement of Water**:
- The root pressure helps to push water upward through the plant, but it is important to note that this upward movement is typically limited to small heights.

5. **Experimental Observation**:
- Root pressure can be experimentally observed by cutting the stem of a well-watered plant. On a humid day, when the stem is cut, a solution (sap) oozes out from the cut end, indicating the presence of root pressure.

6. **Relation to Guttation**:
- Root pressure is also associated with the process of guttation, where water is lost from the plant in the form of liquid droplets, typically seen at the edges of leaves. This occurs due to the pressure built up in the roots.

7. **Role in Water Transport**:
- While root pressure plays a role in water transport, it is primarily effective for short distances. It helps maintain a continuous column of water in the xylem, facilitating overall water transport in the plant.

8. **Conclusion**:
- Based on the above points, root pressure provides a moderate push in the overall process of water transport in plants. Therefore, the correct statement about root pressure is that it is a positive pressure that aids in the upward movement of water, particularly in small heights.