Chromatography

Chromatography allows you to take a closer look at the glorious colors of autumn leaves.

Autumn leaves change colors because chlorophyll levels are reduced. These levels change because of plant hormones, called auxins, that prepare leaves to fall before snow or heavy rains in winter. This period of preparation is called senescence. The act of dropping leaves is called abscission.

Through most of the growing season, leaves are one shade of green or another. The green pigment we see is the chlorophyll used in photosynthesis. There are actually several other colors present, we just can’t see them. Chromatography gives you an inside view into those colors.

Materials needed to perform chromatography at home (Kate Russell)

Chromatography and pepper heat

High-tech chromatography (and some crazy math) are used to rank the heat of chili peppers. The American Spice Trade Association (ASTA) measures the pungency of different samples with Scoville heat units (SHUs), as a function of capsaicin levels.

Chromatography and companion planting

While there is plenty of science to support the importance of installing plants where they will thrive, the concept of plants ‘liking’ and ‘helping’ one another is actually a failed attempt at simplifying complex processes. Back in the 1930’s, Dr. Ehrenfried Pfeiffer conducted a study he called the “sensitive crystallization method” using chromatography. Somehow, the good doctor decided that matching colors implied compatibility, which it doesn’t. But the process is very fascinating, nonetheless, so let’s get started!

Your chromatography experiment

You will need the following supplies:

• several glasses or jars
• mortar and pestle (or a heavy duty spoon)
• white coffee filters or paper towels
• rubbing alcohol (isopropyl alcohol)
• leaves (try to get some of each color, including green)

Here are the steps:

1. Sort your leaves by color.
2. Tear the leaves into tiny pieces.
3. Crush the leaf bits, using the mortar and pestle (or the back of a spoon).
4. Place the crushed leaf bits into their labelled jars.
5. Cut the coffee filters or paper towels into strips that are longer than the depth of your jars.
6. Insert the paper strips into the jars, with the ends draping over, or taping the top edge.
7. Pour enough rubbing alcohol into each jar to cover the mashed leaves.
8. Wait and watch the magic!

The chromatography results are in! (Kate Russell)

You can speed up this process by setting the jars in a Pyrex baking pan and pouring boiling water around (not in) the jars.

Check out my pages on deciduous, abscission, and senescence to see what those different colors mean.