Why Do Leaves Change Color In The Fall?

Every fall the leaves of many trees turn magnificent colors. One of the great benefits of the season is looking at the fall foliage, with its bright reds, oranges and purples, before the leaves fall off for winter. How exactly do the vibrant green leaves turn so many different colors, and why?

Over the spring and summer months, chlorophyll in the leaves absorb sunlight which is then used for energy. The energy is used to convert carbon dioxide, the kind of air we breathe out, to carbohydrates such as sugar and starch, for the tree to use or store. Chlorophyll gives the leaves' their green color. Other pigments are also in the leaves, such as carotenes and xanthophylls; these give yellow and orange pigments. During the spring and summer months, the chlorophyll is most prevalent, therefore the leaves appear green.

In the fall, the lower temperatures and shorter day lengths signal the trees to stop making food. The sugar and starch stored from earlier now serve as food for the tree during the winter months. Since the chlorophyll is not being used, it starts to break down, revealing yellow and orange pigments. Red and purples, or anthocyanin pigments, are made from different chemical interactions with the carotenes and xanthophylls. Thanks to these chemical changes, we are able to see extraordinary fall colors.

About the Author

Rebekah Shaffer

Rebekah ShafferRebekah Shaffer is currently a Junior at Slippery Rock University, PA. She is pursuing her B.S. in Biology, minor in Chemistry. She currently works as a microbiology lab assistant at Slippery Rock University and is a member of Beta Beta Beta Biology Honorary Society. She plans to obtain her Ph.D. in Molecular/Cellular Biology after completing her undergraduate degree.