Chemistry Pic of the Week

ginko2

The leaves are finally really turning into their oranges and yellows, and Ginko trees have always been among my favorite to see change color in autumn. They tend to fall easily after changing color to form blankets of brilliant yellow leaves. I’m glad I snapped this before the rain knocked the leaves down.

The reason the leaves change color in autumn is that the green chlorophyll in the leaves is broken down as the the days grow shorter and the temperatures decrease. Eventually the chlorophyll is broken down to colorless products while the other chemicals in the leaves are left behind. The yellows and oranges are from carotenoids like beta-carotene (yes, the same chemical you find in carrots, as well as many other vegetables) and other xanthophylls (a class of chemical that includes carotenoids).

The reds are a little more special. Again, you’re sure to have encountered the chemical responsible in food, but this time the class of chemicals are called anthocyanins. They’re also responsible for red cabbage and red onions (but not beets). Anthocyanins aren’t present in all leaves at all times, but are instead produced by different plants during different processes.

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