Why Leaves Change Color
We are fortunate in New York State to be able to experience the beautiful colors of fall foliage. Did you ever wonder how and why an autumn leaf changes color?
Plants absorb, or take in, water through their roots, and carbon dioxide from the air. With the help of sunlight they convert water and carbon dioxide into glucose, which is a kind of sugar. Plants use glucose as food for energy and as a building block for growing. This conversion of turning water and carbon dioxide into sugar is called photosynthesis. Which means "putting together with light."
A chemical called chlorophyll helps make photosynthesis happen. Chlorophyll is what gives plants their green color. At the end of summer the days grow shorter and cooler. Plants slow down, and eventually stop producing the food necessary to maintain the green color, chlorophyll, which is the dominant color in leaves. This allows the latent colors, such as yellows and oranges to show. The red and violet colors come from a group of pigments called anthocyanins, which are created by the leaf to act as a sunblock. As the levels of chlorophyll are depleted, the leaf cannot use all the sun's energy that hits it. Anthocyanins absorb the excess so that the sun's rays don't damage leaf tissues.
Additional Articles About Leaf Color Change
- NYS Conservationist article, Nature's Palette (PDF, 300 KB)
- Harvard Forest: The Process of Leaf Color Change (Leaves DEC website)
- Why Leaves Change Color - US Forest Service (Leaves DEC website)