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Desert Diary
Plants/Green Plants


Plants leaves are some shade of green, but why? Somewhat simplified, because green is not part of the color spectrum that is absorbed by leaves—or more specifically, by the chlorophyll pigments in the leaves. Not being absorbed, the green is available to be reflected back to our eyes, giving the plant its green coloration. However, some other parts of the spectrum are absorbed and never make it back out of the chlorophyll. Plants have two kinds of chlorophyll, which in an inspired moment, were named chlorophyll a and chlorophyll b. These two slightly different pigments absorb light in the violet-blue and red frequencies which, thus, are not available to be reflected back out.

Light is made up of packets of energy called photons. Photons in the blue and violet range have lots of energy, whereas photons representing the red end of the visible spectrum carry much less energy. Both are absorbed by the chlorophylls, however, and the energy thus captured is used to manufacture food--food used by the plants and, in part, ultimately by ourselves.
pen and ink


Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.

View of plants showing various greens

View on University of Texas at El Paso campus showing a variety of greens. Photograph by A.H. Harris.