How we did it:
- glass jars (4)
- food coloring
You’ve just watered a thirsty plant, and its roots are starting to absorb the water from the soil. But how does the water travel from the roots to the rest of the plant? The answer is tiny tubes inside the stem called the xylem. They draw the water up from the roots like a straw by a process called capillary action.
Capillary action is what happens when water climbs up things like small tubes. Water can do this because it’s sticky! Not sticky like glue, but sticky like the droplets that stick to your fingers after you wash your hands. Water sticks to the walls of a tube and starts to inch upward. It also sticks to itself, so it pulls more water after it as it climbs. Gradually, capillary action lets water climb up to all the different parts of a plant through the xylem tubes in the stem.
Check out this project to see capillary action at work through a celery’s xylem!
Gather your materials.
Cut about one inch off the bottom of four celery stalks.
Fill each jar about halfway with water. Then, drip a few drops of food coloring into each glass.
Stick the celery stalks in the colored water and let them sit for about 20 minutes.
Rip open 1 or 2 of the celery stalks to better see how the color travels through the stalks.
Come back to the celery after 20 minutes and check out the stalks! What do you see? Color should start to appear in little dots on the ends of them!
Leave the celery overnight and return to it in the morning to see if the colors have reached the leafy green celery tops!
Leaves help pull water up the xylem. They have little holes that let out extra water the plant is done using, so more water can come rushing up. Try comparing a celery stalk with leaves to one without — which gets color up to the top first?
There are lots of other ways to experiment with capillary action. Did you know that capillary action is how paper towels work? Check out https://www.kiwico.com/diy/Science-Projects-for-Kids/3/project/Capillary-Action-Rainbow/2945 or search for other capillary action projects above.