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Activity 1.4
Building a plant from the ground up…sort of
In the following activity, you will build a model of a plant that actually evapotranspires.

What You Need:

  • A couple of plastic drinking straws (the larger the diameter, the better)
  • A clean household sponge
  • Scissors
  • Small bottle, or similar container that can hold water
  • Food coloring
  • A small piece of plastic wrap

What To Do:

  1. Using the scissors cut some long thin pieces of sponge. Each piece should be approximately ¼ inch square and as long as possible.
  2. Cut the straw in segments approximately 1 – 3 inches shorter than the sponge segments (the longer the sponge relative to the straw, the better).
  3. Slide the sponge into the straw. It will be tight fit, so you may need to twist the sponge as you push it through. Position the straw so that there is about the same amount of sponge exposed on either end of the straw.
  4. Using the scissors cut the exposed portions of the sponge to create a branching pattern. These branches represent the roots and leaves of the plant.
  5. Using the food coloring, dye a small amount of water in the small bottle, the darker the better.
  6. Now get the sponge in the straw wet with water, and then place it in the bottle with only the ‘roots’ of the homemade plant in the dye.
  7. Have your plant poke through the plastic wrap so that the only way water can leave is through the straw.
  8. Let your plant sit undisturbed and watch for the appearance of the dye on the top.

What's Going On:

The water is traveling up the stem of your plant via adhesion and cohesion. As the water reaches the plant’s simulated leaves, it evaporates, pulling water behind it. The dye is hitching a ride on the water, much like a ride on an escalator.

Take It A Bit Further:

Idea One:
See if you can change the rate of water travel up your plant stem with changes in temperature. You can place a plant in a warm, sunny place and a cool, dark place in your house.

Idea Two:
How does changing the length of the ‘leaves’ of your plant affect the rate of evapotranspiration? Can you graph your results?

Go Back to Activity 1.3