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ne reason leaves oi some broad-leafed trees change color is that variations in temperature and daylight cause the leaves to stop their food- m a king process.
The food-making process takes place in leaf cells that contain the pigment chlorophyll, which gives the leaf its green color. The chlorophyll absorbs energy front sunlight and uses it in transforming carbon dioxide and water to carbohydrates such as sugars and starch.
Along with the green pigment, leaves also contain yellow or orange carotenoids which, for example, give carrots their color.
During most of the year, these yellowish colors are masked by the greater amounts of green coloring. In the fall when the foodmaking stops, the green color disappears and the yellowish colors become v isible.
At the same time, other chemical changes may occur which cause the formation of additional pigments that vary from yellow to red to blue. Some of them give rise to the reddish and purplish fall colors of leaves of the dogwoods and sumacs.
Tlie conditions that favor the most dramatic changes resulting in vibrant reds are warm sunny days, followed by cool nights when the temperature dips below 45 degrees Fahrenheit. Familiar trees that turn red are the red
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