Root hair cells and the pathway of water

Transport in plants · Water uptake · note 1 of 2

Spec 8.2.1, 8.2.2, 8.2.3Download all Water uptake notes (PDF)Download all notes (PDF)4 pages

Root hair cells and the pathway of waterSpec 8.2.1, 8.2.2, 8.2.3

In short

A root hair cell is a cell in the outer layer of the root with a long, thin extension that absorbs water and mineral ions from the soil. The root hair gives a large surface area, which increases uptake. Water then passes through the root cortex cells, into the xylem, and up to the mesophyll cells of the leaf.

Root hair cells

A root hair cell is a cell in the outer layer of the root that has a long, thin extension called the root hair. Its functions are to absorb water from the soil and to absorb mineral ions from the soil.

The root hair gives the cell a large surface area, which increases the uptake of water and mineral ions.

A root hair cell in soil, labelled thin cell wall, cytoplasm, cell membrane, vacuole with cell sap, nucleus, mitochondria and the long root hair, with arrows for water entering by osmosis and mineral ions by active transport. — A root hair cell. Its long extension gives a large surface area for absorbing water and mineral ions.

The pathway of water

Water takes the same route from the soil to the air. You need to be able to outline it.

Water enters the root hair cells from the soil.
It passes through the root cortex cells.
It enters the xylem and moves up the root and stem.
It leaves the xylem in the leaf and reaches the mesophyll cells.

The pathway of water: soil water enters a root hair cell, passes across the root cortex cells into the xylem in the root, moves up the xylem in the stem, then leaves the xylem in a leaf vein and moves to the mesophyll cells. — Water moves from the soil into the root hair cells, across the root cortex cells, up the xylem and into the mesophyll cells.

Exam tip:

Give the cells in the right order: root hair cells, root cortex cells, xylem, mesophyll cells. Writing 'roots to leaves' alone will not score.

Written and checked against the Cambridge IGCSE Biology (0610) specification · Updated October 2026

Frequently asked questions

How are root hair cells adapted to absorb water?

Root hair cells have a long, thin extension called the root hair, which gives a large surface area. This increases the uptake of water and mineral ions from the soil. The root hair cells are in the outer layer of the root, so they are in close contact with the soil water.

How does water move from roots to leaves?

Water enters the root hair cells from the soil and passes through the root cortex cells. It then enters the xylem and moves up through the root and stem. In the leaf, it leaves the xylem and reaches the mesophyll cells. Give the cells in this order, because 'roots to leaves' alone will not score.

How do you show that water travels up the xylem?

Stand a freshly cut stem, such as celery, in water containing a stain such as eosin, and leave it in a warm, light place for several hours. Then cut a thin cross-section of the stem. Only the xylem in the vascular bundles is coloured, in a ring of small dots, showing that water travels in the xylem.