Sunday, November 6, 2016

Reds Made on Purpose

Red Maple Leaf in Autumn Drawing
A most interesting discussion has begun about a process that most of us marvel at each year and that is the turning of leaf colors.  We know that in the fall (or autumn if you prefer) when it starts to get colder, and daylight gets shorter, the chlorophyll that turns leaves green starts to break down and reveal the underlying cartotenoids, which then turn leaves yellow or orangey. This is familiar to us, but what about the reds? Those glorious reds? All the way back on October 25, 1936, in the New York Times Charlotte Wallum wrote “The red pigments are cell-sap colors.  They are supposed to be tannoid compounds (referred to as anthocyanin) and the pigments of red beets and dark grapes are similar compounds.”

Now eighty years later to the date, October 25, 2016 in the New York Times, Joanna Klein takes another look at this familiar yet extraordinary process in her wonderful article, “Why Does Fall Foliage Turn So Red and Fiery? It Depends.” Klein begins her article poetically, “Leaves scream their final cries in color before dropping to the ground.”  She reminds us of the normal break down of chlorophyll and the revealing of the underlying yellow or orange in most leaves.  Klein then explains that the story of the red leaves is different.  Red leaves are “made on purpose.”  She tells us that the anthocyanins that are produced come from built up sugars in the leaves that combine with the green pigments left in the leaves and turn into different shades of red depending on the species, the environment, and its own genetics.  Clearly eighty years later, scientists understand the process better.  But even today, they are asking why some leaves use their “precious energy” to turn red before they die.  Several theories have been posited: They may be flashing color to attract birds and mammals to their tree’s fruits hoping that they will be eaten and the seeds dispersed.  Or the red leaves could be a warning about the bad-tasting poisons or chemicals in the leaves so they should be left alone and not used as sites for pests wanting to lay eggs.  Or the red color could signal that the leaf is dying and not to be eaten because it has no nutrients.  And finally there is Robert Guy, a professor of forestry at the University of British Columbia who wonders if the red “works like a sunshade in maple trees.”  According to him, the red leaves may serve as a protection from bright and UV light so that the leaves have the time to send their nutrients back into the tree for storage before they drop to the ground. 

I don’t know how many of us will be around eighty years from now, but I certainly hope the maples, the aspens, the black tupelos, the sassafras, and all the other trees whose leaves turn red will be.  In fact, I hope all the trees and natural life of this planet will be. But for now, let's take joy in the glory of the reds, and the glory of the fall. 

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