Water uptake — Cambridge IGCSE Biology
How root hair cells take in water and mineral ions, the route water takes through the plant, and how to trace it with a stain.
Revision notes
2 short notes, in the order of the specification. Each one 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.
Standing a cut stem in water containing a coloured stain, such as eosin or red food colouring, shows the pathway of water. After several hours, a cross-section of the stem shows the stain only in the xylem of the vascular bundles, as a ring of small dots. This shows that water travels up the stem in the xylem.
Exam questions
6 exam-style questions (15 marks), each with its mark scheme.
Answer the questionsFlashcards
4 cards: flip them, mark what you knew, and practise the rest.
Practise the cardsMind map
The whole of transport in plants on one page, so you can see where this subtopic fits.
Open the mind mapPractical sheet
Method, variables, risks and a results table, with questions to answer.
Print it
Free PDFs to print or save.
Quick check questions
What do root hair cells absorb?
Show answer
Water and mineral ions.
Why does a root hair increase uptake?
Show answer
It gives the cell a large surface area.
Give the pathway of water in order.
Show answer
Root hair cells, root cortex cells, xylem, mesophyll cells.
Where is a stain found after a stem stands in stained water?
Show answer
In the xylem.
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.
Written and checked against the Cambridge IGCSE Biology (0610) specification · Updated October 2026