Science 7–10 · Year 8

Water transport in celery: dye rising through the xylem

Science understanding: Biological sciences

PracticalLow risk

The idea

Water travels up a celery stalk through xylem vessels, and the rate depends on how fast the leaves lose water.

Safety card

Low riskAn adult supervises

Hazards

Knife

Controls

Cut on a board away from the hand

Note

No hazardous chemicals; record a RiskAssess risk assessment for the activity as school procedure requires.

What you need

Celery stalks with leaves attached, three per group, plus one with leaves removed and one spare stalk for cross-sections
Red or blue food dye, 10 mL in 100 mL of water, in tall containers
Knife, board, ruler, a fan and a lamp, timer

How to do it

Cut 2 cm from the base of each stalk under water and stand each at once in the dye.
Place one stalk in still air, one under the fan, one under the lamp, and the leafless stalk in still air.
Every 30 minutes for two hours cut a thin slice from the base of a spare stalk to see the dyed vascular bundles as dots, and on each test stalk hold a ruler against the outside to read how high the colour has climbed.
Record height against time and calculate the rise rate in centimetres per hour for each condition.
At the end, cut each stalk lengthwise to show the dyed vessels as lines.

What you should see

Dye rises through the vascular bundles and later colours the leaf veins. The stalks under the fan and the lamp are expected to show the dye front higher at each reading than the stalk in still air, and the leafless stalk the lowest, because transpiration from the leaves pulls the water up. A cross-section shows the dye confined to the ring of bundles, not spread through the stalk. The learner knows it worked when the height readings rise steadily and the cross-section shows dye only in the bundles.

What changes

What you change: Air movement or light at the leaves; presence of leaves
What you measure: Height of dye front (cm) against time; rise rate (cm per hour)
What you keep the same: Dye concentration
Stalk length and freshness
Temperature
Time between readings

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

Water soaks up through the whole stem like a sponge.
Roots push water up; the main pull is from the leaves.
The dye is absorbed by the plant as food.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Science 7–10 Syllabus (2023)SC4-LIV-01 SC4-WS-01 SC4-WS-06
Australian Curriculum v9AC9S8U02AC9S8I03AC9S8I05

Sources

The pages the author read to write this activity.

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