The molecules of chlorophyll are attached to the membranes of disc-like structures, called chloroplasts, inside the cells. The molecules of these compounds are large: C 55H 72MgN 4O 5 for chlorophyll a, and C 55H 70MgN 4O 6 for chlorophyll b. Therefore, the light reflected by the leaves is diminished in red and blue and appears green.Ĭhlorophyll actually includes two pigments, chlorophyll a and chlorophyll b. Chlorophyll absorbs red and blue light from the sunlight that falls on leaves. The green pigment in leaves is chlorophyll. These color changes are the result of transformations in leaf pigments. Formerly green leaves, depending on the species, may turn to brilliant shades of yellow, orange, and red, as well as brown. In certain regions, the shedding of leaves is preceded by a spectacular color show. In these preparations, they shed billions of tons of leaves. It’s called Learn About … The Chemistry of Autumn Colors and in addition to the chemistry of leaf color, you’ll also learn how the colors of leaves are determined and why they aren’t always the same from year-to-year:Įvery autumn across the Northern Hemisphere, the lengthening nights and falling temperatures induce trees to prepare for winter. Yet I know that leaves respond to a number of different cues in making their transition, which I learned about in large part thanks to this story, from the website of the award-winning UW–Madison Chemistry Professor, Bassam Shakhashiri, that we shared here first last fall. But it always seems like the days are too long, the air temperatures still too high, when I first observe the telltale signs of autumn. Not that I am hesitant to see the start of fall, a season I embrace in all its cool-weather, crisp-air glory (and no, it’s definitely not because of #PSL). “But isn’t it too soon?” I think to myself. The trees and prairies slowly changing their attire. Each year, as August fades into September here in southern Wisconsin, it always seems to take me by surprise to see the bright greens of spring and summer subtly transition to the goldens and burgundys of autumn.
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