Why does the foliage of some evergreen plants, especially ones growing beneath deciduous forest canopies, turn reddish in the fall and winter? Part of the explanation may be that, with higher light levels reaching the leaves because of the loss of canopy shade, and with lower temperatures, the photosynthesis apparatus cannot keep up. The leaves are receiving more intense light at a time when some of the biochemical machinery (the “dark” reactions of photosynthesis) are slowing down due to the lower temperatures. By synthesizing the red pigment anthocyanin as a sort of “sunscreen,” the leaf diverts some of this extra light energy away from the green, photosynthetic pigment, chlorophyll, thus protecting the system from destruction due to overload. Here is Wintergreen (Gaultheria procumbens), a small evergreen plant, still green beneath a forest canopy, and more reddish in early fall in a more open setting.
Posted on: Fri, 07 Nov 2014 17:50:23 +0000
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