I love all the beautiful colors of the fall, but have you ever wondered where they come from? What happens to make the leaves turn from green to yellow, orange, and red? I found out while doing my research that part of the answer is that trees have pigments of colorful molecules, inside them. These pigments make food for the trees during the warm, sunny months through the process of photosynthesis. Photosynthesis is when the energy of the sun is absorbed by plant pigments and turned into food energy, which keeps the leaves green; absorb the energy of the sun. However winter brings colder, shorter days, and without as much sunlight the trees shut down and the food making leaves for the winter. Therefore, what you see in the changing autumn colors is gradual change of these pigments.
• Chlorophyll (green) – Chlorophyll for photosynthesis, which is the chemical reaction that enables the plants to use sunlight to manufacture sugars for their food. Trees in the temperate zones store these sugars for the winter dormant period and so trees do not need to actively make food during the winter. Tree leaves must constantly make chlorophyll when they need it for photosynthesis, so once they stop, the green goes away.
• Xanthophyll (yellow) and Carotenoids (orange) –These pigments are also used for photosynthesis, and they are there all summer long, you just do not see them because they are usually masked by the strong color of the green chlorophyll. These pigments do not break down as fast as chlorophyll, so they are around longer during the fall. These pigments are also included in such things as corn, carrots and daffodils, as well as rutabagas, buttercups and bananas.
• Anthocyanins (red) – The anthocyanins are different, because they begin to appear after the plant stops making chlorophyll. These pigments are not there during the summer, and they appear latest in the fall succession of color. Anthocyanin’s are very intense color molecules, and they give color such familiar things as cranberries, red apples, concord grapes, blueberries, cherries strawberries, and plums. They are water-soluble and appear in the watery liquid of leaf cells.
• What makes a leaf look so colorful?
• Can I extract the pigment from a leaf?
• Why do leaves turn fall colors?
• Are plant pigments involved in leaves turning fall colors?
When you look at a leaf, you see the result of all colors mixing. However, if you separate the pigment molecules, you can see each individual pigment color by itself. One method for separating molecules is called paper chromatography. In this method, a solvent is used to dissolve the molecules of interest. Then the solution containing the dissolved molecules is passed through a strip of strong paper. The fibers of the paper trap the molecules as the solvent carries them through the paper. Larger molecules get trapped by the paper fibers first, and smaller molecules can travel farther along through the paper fibers. With this method a colorful mixture of pigments molecules, separated by size.
Why do leaves change colors?
Plants need water and sunlight to continue to grow. They take water from the ground through their roots. They also take a gas called carbon dioxide from the air. Plants use sunlight to turn water and carbon dioxide into glucose. Glucose is a kind of sugar, which plants use as food for energy and as building blocks for growing. The way plants turn water and carbon dioxide into sugar is called photosynthesis. A chemical called chlorophyll helps make photosynthesis happen. Chlorophyll is what gives plants their green color. During winter, there is not enough light or water for photosynthesis. The trees will rest, and live off the food they stored during the summer. They stop making food so the green chlorophyll disappears from the leaves. As the bright green fades away, we begin to see yellow and orange colors. Small amounts of these colors have been in the leaves all along.