From the Museum of Science and Industry, Chicago.
Flowers are living things that need nourishment to grow. Using their roots, flowers “drink” water up into their stems, leaves and flowers to make food. Eventually, the water evaporates from the plants, much like human sweat. This is called transpiration. Even cut flowers without roots can do this! More water is pulled up from below to fill the empty space left by transpiration. This cycle is called capillary action, and it happens because water sticks to itself-cohesion. By watching the journey of harmless food coloring, we can see all the places water goes in a plant!
- White carnations (daisies and other white flowers may work, too!)
- Clear, plastic cups or vases
- Food coloring
- Knife (optional)
1. Fill each cup ¾ full with water.
2. Add 20-30+ drops of food coloring to each glass. Lots of color is better! Leave one glass unaltered as your “control”.
3. Have an adult cut the stems of the carnations on a diagonal. The cut must be fresh to allow for maximum water absorption.
4. Place one carnation in each colored water glass, and one in the plain water.
5. Watch what happens! The carnations will soak up the water, and take on the new colors. This can show in only hours, but may also need a few days.
Examine everything- the stems, leaves, and even deep within the blooms for color changes. Compare the flowers with food coloring to the ones without. These blooms really are what they eat!
If you want to get extra fancy, CAREFULLY cut the stem of a carnation in half with a knife. Place each half into a different color. Make predictions. Observe.
Also think about…
- What would happen to these flowers if the water became polluted?
- How are these flowers like people? What happens to what we eat? How does it change us?