Investigating the pathway of water with a stain

Transport in plants · Water uptake · note 2 of 2

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Investigating the pathway of water with a stainSpec 8.2.4

In short

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.

You can show where water travels in a plant by putting the cut stem in water that contains a coloured stain (dye), such as red food colouring or eosin. The stain is carried in the water, so it shows the route.

Fill a beaker with water and add a few drops of the stain.
Cut the base of a stem (for example celery, or a white flower) so that it has a fresh end, and stand it in the stained water.
Leave the plant in a warm, light place for several hours, or overnight.
Look for stain in the veins of the leaves or the petals.
Cut a thin cross-section (transverse section) of the stem with a sharp blade and look at it with a hand lens or microscope. Cut away from your fingers.

The stain is found in the xylem. In a cross-section of the stem, only the xylem in the vascular bundles is coloured, in a ring of small dots. This shows that water travels up the stem in the xylem. In a longitudinal section, the stain appears as coloured lines.

A celery stalk standing in a beaker of red-stained water, labelled stained water, cut base and coloured veins in the leaf, beside a cross-section of the stalk where only the xylem in the ring of vascular bundles is stained red, with unstained phloem, unstained cortex and the epidermis labelled. — The stain travels with the water, so only the xylem is coloured.

Practical skill:

Control the variables if you are comparing plants: same type of plant, same volume and concentration of stain, same time, same light and temperature. Write what you see, not just what you expect.

Quick check

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.

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.

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