Why do leaves change color in the fall? And why do different trees turn different colors? All leaves contain chlorophyll. Chlorophyll reflects green light making leaves look green. As the days shorten and the nights cool, trees form a layer of cork cells in the stem of their leaves. This causes the leaf to die and eventually fall off. But before they fall off, many leaves turn color.
Plants contain a class of compounds called carotenoids. Carotenoids help absorb extra light to prevent damage to leaves. These compounds are responsible for many of the bright colors in flowers and fruit. The colors of sunflowers, peppers, carrots, and mangos are all caused by a specific carotenoid. Carotenoids were first identified in carrots which gives the compounds their name. The two main carotenoids that color fall leaves are carotene and xanthophyll. Carotene is orange while xanthophyll is yellow. In growing leaves, carotenoids are hidden by the chlorophyll in the leaf. But in the fall, the leaves stop producing chlorophyll. Chlorophyll degrades quickly but carotenoids last much longer. This causes the leaves to turn different colors. The exact color varies from tree to tree depending on which carotenoid is more common in the leaves.
Another chemical is responsible for the bright red color in leaves. Anthocyanins produce red or purple colors in plants. Anthocyanins provide extra protection for leaves. Young leaves often appear reddish because they contain high concentrations of anthocyanins. Some plants have purple leaves at all times of the year. These plants continuously have high amounts of anthocyanins. The leaves of other plants only contain large amounts of these compounds in the fall. Additionally, anthocyanins are produced from chemical reactions with the sugars in the leaves. Anthocyanins are responsible for the brilliant reds and red purples in trees.
Fall color is more brilliant in healthy trees. This causes fall color to vary from place to place depending on the weather of the previous summer. In addition, cool nights and sunny days help boost fall color. And not only are blue skies good for fall color, but fall color is good for blue skies!