Observations and results
Were you able to see multiple bands of color on your test strips? Did you see that some of the bands present were different for the different color solutions used?

Even though a plant leaf looks like it is mostly one color, it is actually made up of a mixture of pigment molecules. In this procedure, paper chromatography separated the pigments by the size of their molecules. Consequently, you should see different colors at different locations as you go along one of the paper towel strips, and the order in which the colors appear should be roughly the same among the different color solutions you tested.

What are the different bands of color on the test strips? These are the different pigments in the leaves. The ones you may see on your paper towel strips are: green chlorophylls, yellow xanthophylls, orange carotenoids and red anthocyanins. Pigments with larger molecules generally stay near the bottom of the strip, where the solution was first "painted" onto the pencil line, because it is harder for them to travel up through the paper towel's woven fiber. Smaller pigments can more easily traverse the paper towel and, consequently, they usually travel farther up the strip.

Because the color of the leaf is dependent on the mixture of pigments within it, different colored leaves will display different colors on their paper towel strips. For example, very green leaves may not have any red colors (anthocyanins) on their strips.

Cleanup
Because some plant pigments can stain, be careful not to spill your colored solutions when throwing them away.

More to explore
"What Causes the Leaves on Trees to Change Color in the Fall?" from Scientific American
"Why Leaves Change Color," from S.U.N.Y. College of Environmental Science and Forestry E-Center
"Autumn Foliage Color," from The Fisher Museum, Harvard Forest, Faculty of Arts and Sciences of Harvard University; and Florida International University, Department of Biological Sciences
"Paper Chromatography Resources," from Science Buddies
"Paper Chromatography: Basic Version," from Science Buddies

This activity brought to you in partnership with Science Buddies

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