MadSci Network: Botany

Re: Why do leaves change colour in the fall?

Area: Botany
Posted By: Gary Bachman, Grad Student Horticulture-Plant Physiology, Ohio State University.
Date: Tue Sep 24 20:44:14 1996
Message ID: 842210180.Bt

The changing of leaf colors in the fall is part of a complex reaction of trees to decrease in light and lowering of temperatures.

As winter approaches trees move nutrients in the leaves to the roots where the nutrients are stored. These stored nutrients provide the energy for the first growth in the spring. As nitrogen and magnesium are taken from the leaves the characteristic green color of leaves is also removed. What remains are pigments called anthocyanins and carotenoids.

Anthocyanins are responsible for the red, purple, and blues. Reds, yellows, and oranges are from carotenoids. Production of these pigments are enhanced by high light and cool temperatures.

Usually colors are similar in the same species of trees. Oaks are reddish, maples have yellow, orange, and reds, while sweetgums produce dark reds and purples.

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