Tracing water transport with dye in celery and white flowers, with… · Concept Studio

The idea

Water travels through xylem vessels, which stain along their length and can be located in a stem section, and adjacent vessels exchange water sideways.

What you need

Celery stalks with leaves, 3; white carnations or chrysanthemums with long stems, 2
Food dye (blue and red) or 0.5 percent eosin, in 100 mL measuring cylinders
Scalpel on a white tile; hand lens; slides, coverslips and microscope; ruler; stop clock; polythene bag

How to do it

Stand a celery stalk in dyed water and a second in plain water; enclose a third in a polythene bag in dyed water to reduce transpiration.
Split the stem of a white flower lengthwise for half its length and stand one half in blue dye and the other in red.
After 1, 2 and 24 hours cut 1 cm slices from the celery and record the highest point the dye has reached; calculate the rate of rise in centimetres per hour.
Cut a thin transverse slice about 1 mm thick (as the source advises), view it under the microscope at 40x then 100x, identify the stained vascular bundles and draw the position of the xylem within a bundle.
Record the colour distribution in the flower petals at 2 hours and then each day.
Compare the bagged and unbagged stalks.

What you should see

The dye rises several centimetres in the first hours and reaches the leaves within a day; slices show the stain confined to small dots in the vascular bundles (the xylem), which lie in a row just inside the ribbed outer surface of the stalk, not spread through the surrounding tissue. The split flower first shows the two colours on separate sides, and over the following days both colours spread across the whole head as water passes sideways between vessels (as the source describes). The bagged stalk shows a lower rise than the open one. The learner knows it worked when the stain is localised to the bundles in section and the flower shows the two-colour pattern.

What changes

What you change: transpiration condition (bagged or open)
What you measure: height reached by the dye after a fixed time
What you keep the same: dye concentration
stalk length and source
temperature and light
time

Common misconceptions

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

Water spreads through the whole stem like a sponge; it travels in specific vessels.
Xylem and phloem carry water in both directions; xylem carries water upward and phloem carries sugars.
Petals change colour because dye is absorbed through them; the dye arrives through the stem vessels.

Safety card

Low riskLearners carry it out

Hazards

Scalpel cuts
Dyes stain skin and clothing

Controls

Carry scalpels in a tray; cut away from the body
Wear gloves or wash hands after handling dye

Note

Food dyes and eosin are low hazard: RiskAssess (https://www.riskassess.com.au/).

Curriculum references

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

Biology Stage 6 Syllabus (2017), current: Year 11 taught to the end of 2026 and Year 12 to Term 3 2027BIO11-9 BIO11/12-4 BIO11/12-7
Biology 11–12 Syllabus (2025), Year 11 focus area Cells to systems; new syllabus not yet taught: Year 11 from Term 1 2027, Year 12 from Term 4 2027BI-11-02
Biology 11–12 Syllabus (2025), Year 11 Working scientifically; new syllabus not yet taught: Year 11 from Term 1 2027, Year 12 from Term 4 2027BI-11WS-04 BI-11WS-07
Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.