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:
Which is the process that enables the passage of water from the soil into the root hair?
Topic: Osmosis
Answer
OSMOSIS (endosmosis).
Water moves from the DILUTE soil solution into the more CONCENTRATED cell sap of the root hair, across the SELECTIVELY PERMEABLE plasma membrane.
THE GRADIENT IS WHAT MAKES IT WORK: the cell sap is HYPERTONIC to the soil water. If the soil were the more concentrated — as after excess fertiliser — the flow would REVERSE and the plant would wilt, which is exactly what part (v) of this question asks you to draw.
Note that MINERALS enter differently, by ACTIVE TRANSPORT against the gradient, using energy from ATP. Water by osmosis, minerals by active transport.