Question

Which of the following best describes the widely accepted root pressure theory in plants?

• A. It explains the mechanism of water movement through transpiration pull.
• B. It describes the active uptake of minerals from the soil.
• C. It refers to the pressure exerted by roots to push water upwards through the xylem.
• D. It relates to the diffusion of gases in plant cells.

Hint:

Root pressure is particularly important in small plants and during the early stages of plant growth, helping to maintain water flow in the absence of strong transpiration forces.

Answer 1

The Correct Option is C

The root pressure theory explains how plants can transport water from the roots to the shoots without relying solely on transpiration pull. Root pressure is generated when ions are actively transported into the root xylem, lowering the water potential and causing water to enter the xylem from the soil by osmosis. This influx of water creates a positive pressure that pushes water upwards through the xylem vessels.
Mechanism of Root Pressure: \[ \text{Transport of Ions} \rightarrow \text{Lowered Water Potential} \rightarrow \text{Water Uptake by Osmosis} \rightarrow \text{Positive Pressure} \] 
Conclusion: Root pressure is a vital mechanism that assists in the upward movement of water, especially during times when transpiration is low, such as at night.