The figure given below is a diagrammatic representation of a part of the cross section of the root in the root hair zone. Study the same and then answer the questions that follow: The figure given below is a diagrammatic representation of a part of the cross section of the root in the root hair zone. Study the same and then answer the questions that follow:
Name the pressure that is responsible for the movement of water in the direction indicated by the arrows. Define it.
Topic: Root pressure
Answer
ROOT PRESSURE.
ROOT PRESSURE is the positive pressure that develops in the root xylem as a result of cell-to-cell OSMOSIS in the root tissue: as each turgid cell presses on the next, water is forced inward and upward into the xylem.
Both halves must be answered: the NAME and the DEFINITION.
HOW IT ARISES: water entering the root hair makes that cell turgid, so its sap becomes more dilute than the next cell inward. Water therefore passes on to that cell, and so on across the cortex — a chain of osmotic gradients ending at the xylem. The accumulated push is root pressure.
DISTINGUISH IT from the two pressures WITHIN a single cell, which the 2016 paper also asks about: TURGOR PRESSURE is the outward push of the contents against the wall, WALL PRESSURE the equal inward push of the wall. Root pressure acts on the whole ROOT SYSTEM, not within one cell.
Root pressure alone cannot lift water to the top of a tall tree — that needs the TRANSPIRATION PULL from above.