What makes leaves turn color

The vivid reds come from pigments called anthocyanins which are manufactures from sugars in the leaf. The sugars are stored in the twigs for next spring when leaves emerge again. This cyclic pattern repeats itself every September in countries that experience seasonal weather.

Although it might seem trivial, fall colors are one of those intangibles that make life exciting. The quantity and quality of the color vary depending on weather, sunlight and soil moisture. An article by the department of Biology at Appalachian State University states that trees are extremely sensitive to environmental shifts.

Climate change can result in higher temperatures, increased precipitation, and increased cloud cover, which all act together to disrupt the vibrancy, longevity and brilliance of fall tones. If global warming results in higher temperatures this would mute, and delay fall tones by causing confusion to the trees physiology.

The many beautiful interrelationships in the forest community leave us with myriad fascinating puzzles still to solve. Return to the St. Paul Field Office Home Page. Carotenoid pigments are also lost from the plastids during aging, but some of them are retained in the plastids after the chlorophyll is removed; this produces autumn leaves with yellow colors.

In unusual cases, sometimes in winterberry holly, a fair amount of chlorophyll is left in the leaves when they fall. Such leaves are a pale green in color, or perhaps yellow-green from the mixture of chlorophyll and carotenoids. Most interesting are leaves that turn red, because this color is the result of the active synthesis of anthocyanin pigments just before the leaves fall from the trees.

In these leaves, the actual shades of red are the consequences of the amounts of anthocyanin, the retention of carotenoids or even a little chlorophyll. 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. All these colors are due to the mixing of varying amounts of the chlorophyll residue and other pigments in the leaf during the fall season.