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← Explorers ScienceHow plants drink20 minutesStd 3–5

The Thirsty Stalk

✨ Cut the stalk open and you find coloured dots in a neat ring, the actual pipes the water travelled up.

A celery stalk standing in dyed water with narrow xylem tubes carrying the colour up to the leaves, a cut cross-section showing a ring of coloured dots, and vapour arrows leaving the leaves.
How it works

🧰 You need

  • a celery stalk with leaves, or a white flower
  • a glass of water
  • dark food colour
  • a knife for an adult to use
  • a ruler

⚠️ Ask an adult to do all the cutting.

👀 What you will see

Fine coloured lines run up the stalk and the leaf veins turn the colour of the dye. The cut end shows coloured dots arranged in a ring, not spread everywhere. A stalk with its leaves on carries the colour much higher than one without.

🧪 Do it

  1. Ask an adult to cut a fresh slice off the bottom of the stalk.
  2. Stir plenty of dark food colour into the glass of water.
  3. Stand the stalk in the coloured water in a bright place.
  4. Look after two hours and again after a whole day.
  5. Ask the adult to cut across the stalk about halfway up.
  6. Measure how high the colour has climbed and draw what the cut end looks like.

💡 Why it happens

Plants contain narrow tubes called xylem that run from the roots to the leaves, and those are the coloured dots you found. Water escapes from tiny holes in the leaves as vapour, a process called transpiration, and that loss pulls the next water up the tubes behind it. The dye cannot leave through the leaves, so it stays behind and stains the pipes, showing you the route. No pump is involved at all, which is how water reaches the top of a tall tree.

🔁 Now try this

Set up two stalks in the same colour, one with its leaves and one with every leaf removed, and compare how high the colour climbs in a day.

🤔 Think about it

If transpiration pulls the water, what happens to a plant on a hot windy day?

🧘 Ask the Acharya

“If transpiration pulls the water, what happens to a plant on a hot windy day?” — ask him and he will explain it from your own chapters.

Ask Guru →

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