#FYI: Why Do Leaves Turn Different Colors? Leaves are loaded with chlorophyll which makes them green. But all green plants also carry a set of chemicals called carotenoids. On their own these look yellow or orange carotenoids give color to corn and carrots for example but they re invisible beneath the chlorophyllic green of a leaf for most of the year. In the fall when the leaves are nearing the end of their life cycle the chlorophyll breaks down and the yellow-orange is revealed. âÂ#Âoethe color of a leaf is subtractive like crayons on a piece of paperã¢Â# says David Lee formerly of Florida International University who has studied leaf color since 1973. Most trees have evolved to produce a different set of chemicals called anthocyanins when it s bright and cold in autumn. These have a reddish tint and are responsible for the color of a blueberry. They re also sometimes made in newly sprouting leaves which explains their sometimes reddish tint. Where chlorophyll and anthocyanins coexist the color of a leaf may run to bronze as in ash trees. At high enough concentrations anthocyanins will make a leaf look almost purple as in Japanese maples. More drab autumn colors form as leaves really die and complete the breakdown of the chloroplasts. When they re all dried out the pigments link up together into what Lee calls a âÂ#Âoebrownish gunk. âÂ# Have a burning science question you'd like to see answered in our FYI section? Email it to fyi@popsci. com. This article originally appeared in the November 2013 issue of Popular Science
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