Chromatography with leaves
We all know that green leaves turn yellow to orange color during winter. But is there a way to find out what color, the leaves of a particular tree would turn during winter? We can find that using paper Chromatography. Learn more about paper Chromatography by doing this science project “Chromatography with food colors”. The pigment which gives the winter colors for the leaf is also present during summer. But during summer, the leaves contain far more green pigment called chlorophyll which hides the other pigments. The chlorophyll produces food by photosynthesis using sunlight. But in the winter time, the chlorophyll breaks down and other pigments reveal their colors. Some new pigments will also form in some plants during winter called anthocyanin which is red in color. Let’s find out what would be the winter color of the leaves of some of the trees in our backyard using paper Chromatography.
- Chromatography paper or filter paper
- Leaves of some plants
- Isopropyl alcohol
- Mortar & pestle or Food mixer grinder
- Capillary tube
- Take a filter paper and cut it into 1 X 6 inch rectangular strips or use a Chromatography paper. Draw a horizontal line 4 cm form one end of the paper using pencil.
- Grind leaves of different trees separately using Mortar & Pestle or Food mixer grinder with very little water into a fine pulp. Pour enough isopropyl alcohol to just cover the leaves and stir the solution. Isopropyl alcohol is used because it dissolves the color pigments in the leaves. Stronger the leaf pigments in the alcohol, the brighter the color spots on the Chromatography paper.
- Using a fine capillary tube, put a drop of the mixture in the middle of the pencil line. Let it dry. Again put a drop on the same spot and let it dry. Do this 5 or 6 times. More repetition is necessary if the mixture has weak concentration.
- Tape the strip to a pencil and let the pencil sit across the beaker, the strip will hang down into the beaker.
- Pour isopropyl alcohol into the beaker until it barely touches the bottom of the strip. Note that the mixture spot should not touch the isopropyl alcohol.
- Leave the strip hanging in the isopropyl alcohol until the isopropyl alcohol wets the top of the strip. After the isopropyl alcohol reaches the top, take it out and let it dry.
You should be able to see the "green" color break up into several different colors as the different pigments begin to separate. You'll see different shades of green, and perhaps other colors like orange, purple or yellow as well. It depends on the type of leaves used. In winter, the leaf color would be a mix of colors in the strip other than the green.
As the water rises up the paper, it carries the components of the mixture with it. Some components will travel faster than the other, causing the different colors to spread out.
Were you able to see multiple bands of color on your test strips?
Were leaves of different plant have same or different band of color pigments?
Try the experiment with leaves at more intermediate stages of change of a tree with a wide range of colors. You can also try this experiment with other plant sources like beets, spinach, flowers, red cabbage, Jamun fruit or other intensely colored plants.