This extraordinary chemical absorbs from sunlight the energy that is used in transforming carbon dioxide and water to carbohydrates, such as sugars and starch. Along with the green pigment are yellow to orange pigments, carotenes and xanthophyll pigments which, for example, give the orange color to a carrot.
Most of the year these colors are masked by great amounts of green coloring. But in the fall, because of changes in the length of daylight and changes in temperature, the leaves stop their food-making process. The chlorophyll breaks down, the green color disappears, and the yellow to orange colors become visible and give the leaves part of their fall splendor. At the same time other chemical changes may occur, which form additional colors through the development of red anthocyanin pigments.
Some mixtures give rise to the reddish and purplish fall colors of trees such as dogwoods and sumacs, while others give the sugar maple its brilliant orange. The autumn foliage of some trees show only yellow colors. Others, like many oaks, display mostly browns.
This pigment is also used to convert sunlight into energy for the tree. In summer, chlorophyll is constantly replaced in the leaves. When it gets cold, the plants stop making chlorophyll and it breaks down into smaller pieces. The trees can reuse the nitrogen that is in the chlorophyll molecule. This is why leaves change colors before they fall off of the tree; the important nutrients that can be reused are taken out of the leaf.
The time when leaves start changing color is more dependent on light than on temperature so leaves start changing color at about the same time each year. When deciduous trees reach this light threshold , carbohydrates are transferred from the leaf to the branch and no new minerals are brought in. The trees prepare to separate with their leaves. The green color of chlorophyll is so strong that it masks any other pigment.
The absence of green in the fall lets the other colors come through. Leaves also contain the pigments called carotenoids; xanthophylls are yellow such as in corn and carotenes are orange like in carrots. And 5 Other Burning Questions N. Join the conversation. Related Stories. Gardening Sumac by Laura Boyle.
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Extreme weather changes can also have an effect on the leaves. So if you want to know how long the colors will last this fall, be sure to keep an eye on the weather! Weather Forecasting. The Short Answer:.
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