Biology

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Materials

• 1 white flower (a carnation, daffodil, rose, tulip or chrysanthemum works well)
• 1 cutting board
• 1 sharp knife
• 2 drinking glasses
• Food coloring of two different colors
• 2 spoons
• Water

Short explanation

The different parts of the stem transport water to different parts of the flower. The water then evaporates from the flower while the colors remain.

Long explanation

A plant usually absorbs water in its roots. This water is then transported via the stem up to the leaves and flowers. There, the water is needed for photosynthesis, as well as to serve as the main content of the cells. The water then evaporates from the plant. This creates a suction that propagates all the way down to the roots and more water is absorbed. This suction works exactly the same as when you suck water through a straw, with the difference that in the plant it's the evaporation of water that creates the suction.

The water moves in small tubes called xylem. In the stem there are several xylem bundles. As this demonstration shows, some xylem tubes lead to one half of the flower, while other tubes lead to the other half.

When the flowers begin to show signs of wilting, you can dry them. Take them out of the water and hang them upside down on a string.

Experiment

You can turn this demonstration into an experiment. This will make it a better science project. To do that, try answering one of the following questions. The answer to the question will be your hypothesis. Then test the hypothesis by doing the experiment.

• Which flower species gives the best result?
• What does the flower look like after 1, 2, 4, 6, 12, 24, 48, 72 hours?
• How many parts can you divide the stem into and still make the demonstration work?
• What happens if you place the stem in some other kind of colored liquid (soda, juice, coffee)?
• Is there any color that the flower has a harder time turning into?
• What kind of color (watercolor, oil paint, etc.) gives the best results?
• What happens if you place one half of the stem in water with plant nutrients?
• What happens if you place one half of the stem in salt water?

Variations

Some white flowers have stems that are too small to divide, but it's still fun to color the flower in only one color.

Try dividing a stem into four parts and place each part in its own color. If you do the same with several flowers, you get a small bouquet that you can tie together and which then stands steadily on its four legs. Then you can put the whole bouquet in four small containers with colored water, so you save food coloring as well. Now you can really get rainbow flowers!

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