When you give a flower a drink of water, where does the water go? My daughter and I recently investigated this very question, and thought it would be a fun way to combine science while making custom-colored flowers for Valentine’s Day.
Supplies
- 1 dozen white flowers; carnations work really well!
- Water
- Vase
- 4 glasses or large cups
- Knife or box cutter
- Food coloring (several colors)
Directions
- With adult supervision, trim flowers to a workable length, and cut the ends at an angle. Keep all flowers in plain water until you are ready for the next steps.
- With an adult, use the knife to split three of the flower stems straight down the center. Return them to plain water.
- Fill four glasses with water and up to 20 drops of food coloring. Each glass should have a different color of water.
- Line up the cups next to each other. Using your split-stem flowers, place flowers straddling the cups so one side of the stem is in one color and one side is in another.
- Place one non-split flower in each cup of colored water. Leave the rest of your flowers in the plain water as a control.
- Leave all flowers for two to five days and make observations along the way! This is a good chance to make some predictions: What will happen to the flowers in colored water? Will the colors mix? Which colors will you see in the flowers first?
What’s happening?
Did any of your predictions come true? Take a look at the leaves, too. What do you notice? There’s some very cool science happening here. Flowers “drink” water almost like you would drink water through a straw. The flowers take up water through thin tubes called xylem in a process called capillary action.
As water evaporates from the leaves and petals of the flower (known as transpiration) and creates a low-pressure system, more water is drawn up through the tubes, because water molecules like to stick together. This is called cohesion. The dye in the water travels up the tubes, too, but doesn’t evaporate, so it remains in the leaves and petals.
Splitting the stems allows us to see how the tubes are arranged in the flower stem, and where they end. Try splitting your flower stem into thirds or swapping colors of dye after a few days. What happens then? Happy experimenting!
Did you know? Flowering plants have been around for more than 174 million years — they’re much older than the 66 million-year-old dinosaur, Victoria the T. rex, currently on display at Arizona Science Center through May.
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