Thursday, October 18, 2012

Deep Purple Fall

Normally, when I think of fall and the changing leaves, I picture bright reds, yellows and oranges, complemented by bronze and gold. Your typical New England landscape in October, right? For some reason, this year my eye has been drawn to purple leaves, such as this sweet gum tree, which I don't really recall seeing before.
Even the dogwoods look more purple than red this season. Am I getting old and my vision changing? Well, yes, that's true, but I don't think color vision changes with age. Perhaps I'm just expanding my horizons. Yes, that's a much better sounding explanation.
The National Arboretum website has a page on the Science of Color in Autumn, explaining why leaves turn color. Hmm, I thought it might end up being related to chemistry somehow. According to the Arboretum folks, it's the longer nights that makes leaves start to change color, no matter what the temperature is. Chlorophyll makes the leaves green during summer when they are manufacturing sugars, but when the nights are longer, chlorophyll breaks down allowing other chemicals to show their colors. Chlorophyll normally masks the yellow pigments known as xanthophylls and the orange pigments called carotenoids — both then become visible when the green chlorophyll is gone. These colors are present in the leaf throughout the growing season. Red and purple pigments come from anthocyanins. In the fall anthocyanins are manufactured from the sugars that are trapped in the leaf. In most plants anthocyanins are typically not present during the growing season. 

Grapes are supposed to be purple, but these tiny wild grapes were so high in the tree I couldn't pick any for a closer look. But the birds certainly enjoyed them.

Sometimes, plants are supposed to be purple anyway, such as these beautiful asters. Whatever your favorite color may be, look around during the fall, and you will probably find it. Enjoy the colors now before they all disappear for the drab grays of winter.

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