Why such an intense effort on the part of leaves to survive a couple more weeks? Such an intricate process might seem to belie the fact that all this takes place over just six weeks or so, just before the leaf dies and falls from the tree. Reiser’s unique time lapse of leaf colors may be a key cog in proving this theory since the making of anthocyanins could also explain the spotty patterns of color on the leaves - since of course light exposure and even temperature can vary a great deal over the surface of a leaf, making the pigment appear only in small areas. Spotty coloring on leaves may be evidence of microenvironment of each leaf In what might be another crucial finding, these red pigments also act as antioxidants, protecting leaves from the toxic byproducts that are formed from the breaking down of chlorophyll when it ages. These anthocyanins actually help shield the leaf by absorbing excess light at wavelengths that cannot be used for photosynthesis, including the green part of the visible spectrum of light. However, most experts believe the theory propounded by horticulturist Bill Hoch that red pigments offer protection from excess light when the leaf is most vulnerable - and the would be the case in the Fall, when the light is very bright and clear and the trees and other plants are not photosynthesizing nearly as efficiently as they did when they had plenty of chlorophyll.
This would have the great advantage of discouraging bugs from feeding on it, or even laying eggs on such a surface. William Hamilton, an evolutionary biologist, stated that the color is used to protect plants from being eaten, because red might trick insects into believing that a leaf is toxic or unhealthy. So why would a leaf use up all its energy like this? Lee says there are two main theories on that. “People argue that the red color is (also) an unmasking from the breakdown of chlorophyll, and that’s simply wrong,” Lee explains, adding “The red color is actually made when the chlorophyll is beginning to break down - there’s a synthesis of those pigments, so it’s quite a different thing.” Most red tones in Autumn leaves are produced by a pigment called anthocyanin which the leaf produces as it dies. As the leaves continue to lose chlorophyll, they carotenoids eventually produce tannins and become brown. Yellow leaves that are seen on trees like witch hazel do indeed go through a breakdown of the green photosynthetic chemical called chlorophyll, which exposes the yellow pigments, or carotenoids, hiding underneath.Īnd just like you would imagine, carotenoids are the very same chemicals that give pumpkins and carrots their golden colors. Chlorophyll is seen inside the chloroplasts of a cell in a leaf.
Many people think all the Autumn colors are produced by the leaves in the same way - but that’s not true, with the one exception being the most vibrant and striking of them all, the reds. “Every fall, people write about color change, and typically the articles are full of all kinds of mistakes,” Lee states to Smithsonian.
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