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Why do maple leaves turn red and yellow in autumn?
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Temperate forest
Worldwide distribution of temperate forests.
The vibrant red and yellow colors of maple leaves in autumn are the result of a controlled biological process as trees prepare for winter dormancy.
During the growing season, leaves appear green due to the presence of chlorophyll, a pigment essential for photosynthesis. As day lengths shorten and temperatures cool, the tree stops producing chlorophyll and begins to break down the existing pigment.123
This degradation reveals other pigments that were previously masked by the green:
- Yellow and Orange: These colors are produced by carotenoids, which are present in the leaf throughout the growing season but are hidden by the dominant chlorophyll.13
- Red and Purple: These hues are caused by the accumulation of anthocyanins, which are produced in the leaves as chlorophyll breaks down.13
This color change is part of the abscission process, where the tree seals off the vessels connecting the leaf to the twig to protect itself from winter cold and prevent water loss.23