Kids, as you know, plants need water to live. Water goes from the root, up the stem, and into the leaves. Did you ever wonder how the stem is specially made so that water can travel up it? This experiment will help you find out.
Please note: All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.
You will need a glass one-third full of water, blue food coloring, and a 8-10" stalk of celery that has been freshly cut on both ends by an adult partner. Notice the small dots on the narrow end of the celery stalk. Add 5 drops of the food coloring to the water and place the wide end of the celery in the water. After a few hours you should see that the little dots on the top of the celery are now blue. Use a fingernail to start pulling away one of the blue tubes at the top. Can you pull it all the way down and remove it totally from the stalk? Try another experiment with two new celery stalks. Carefully remove all of the tubes from only one new stalk and then place them both in the blue water. Compare them after 24 hours.
This activity should help you discover how water can move up through a plant stem. Many plants have a series of tube-like cells that bring water up, and another set that takes nutrients produced in the leaves down the plant. After 24 hours, the celery without the tubes should be much more limp than the piece with the tubes intact. You might also be surprised to see what happens to a white carnation after being placed in a glass of water with food coloring for several hours; try other food colors and make a multi-colored bouquet! (Hint: cut about 1" off the bottoms of the of the carnation stems first).
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Kathleen Carrado Gregar, PhD, Argonne National Labs
[email protected]
Aug-Sept 1993
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