Each fall, we enjoy the scenery of changing foliage as summer is extinguished in a blaze of color of color. The yellow and orange pigments in leaves are actually there all year round - we don't see them in spring and summer because the green chlorophyll is more concentrated.

The red and purple colors, however, are made in the leaves in the fall. These colors come from pigments called anthocyanins, and why trees such as maples and oaks make them in the autumn is still a bit of a mystery. New research suggests they're produced partly for protection at a time when the tree is vulnerable. In the fall, trees are busy taking in nutrients from their leaves and storing those nutrients for the winter. During this time, the leaf tissues that are responsible for photosynthesis are especially sensitive to stresses, such as too much light.

Researchers have found that just as the storing process begins, leaves start producing large amounts of anthocyanins. The researchers believe that these pigments act, in a way, like sunscreen - they shade the vulnerable parts of the leaves from too much sunlight at a time when the trees are busy preparing for winter. Whether that sunscreen is SPF 15 or SPF 30 the researchers didn't say.