Why do leaves change color in autumn? The short answer: chlorophyll, carotene, and anthocyanins, three pigments found in leaves. Chlorophyll absorbs red and blue light from sunlight. Carotene absorbs blue-green and blue light. Anthocyanins, formed by a reaction between sugars and certain proteins in cell sap, absorb blue, blue-green, and green light. Light reflected from chlorophyll appears green; light reflected from carotene appears yellow; and light reflected from leaves anthocyanins appears red. Cold (but not freezing) weather destroys chlorophyll and allows the yellow reflected from carotene to dominate. Low temperatures and bright sunshine also stimulate anthocyanin production. Dry weather increases sugar concentration in sap and adds additional anthocyanin. So, the brightest autumn colors are produced when dry, sunny days are followed by cool, dry nights.
- US Department of Agriculture
Why leaves change color
Chemical of the week: the chemistry of autumn colors
Last updated by Ginger L. on March 14, 2011
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