The secrets of why the leaves of trees change yellow or red in the autumn are slowly being revealed. Those eye-seducing hues, it appears, are a lot more than pretty. They’re the result of trees doing their utmost to survive. They’re the shades of evolutionary success.
Let’s start with the green leaf: We all learned in school that it’s the result of the most abundant pigment in the leaf being the green chlorophyll. When the cool air and shorter days of autumn arrive, leaves change to red or yellow not because the leaves are dying, but because of a series of clever processes underway.
Not so surprisingly, yellow leaves undergo one sort of color changing process and red leaves another. As the chlorophyll is being turned off, most leaves turn yellow, which is just a color that’s already in the leaves but is usually flooded by green the rest of the growing season.
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