How Does Water Climb a Tree?

Next time you're flopped out under a shady tree, ask yourself this: how does the water flow up from the tree's roots to its leafy crown? Here's an experiment to help you solve the mystery.

You'll need:

• a cup, half-filled with water
• some blue or red food colouring
• a stalk of celery with some leaves on it

1. Mix a teaspoon of the food colouring into the water.
2. Cut the celery stalk about 2 cm (about 1 inch) from the bottom to expose a fresh end and stand the stalk in the water.
3. Leave the celery in the water for an hour or two and you'll see the dye gradually colouring the leaves.
4. When the colour has spread to the tips of the leaves, take the celery out of the water and cut across the stalk. You'll see a row of tiny circles outlined in colour-they're the cut ends of fine long tubes that travel the length of the stalk. The coloured water travelled up those tubes. Trees have similar tubes running up through their trunks.

What's happening?

Excerpt from The Jumbo Book of Science by the Ontario Science Centre, used by permission of Kids Can Press Ltd., Toronto.