It seems appropriate to feature the “orange-y” colors of autumn as we celebrate All Hallow’s Eve today in recognition of saints, martyrs, and our own dearly departed.
Yellow leaf colors derive from the unmasked xanthophyll pigments in the leaves; orange colors are a result of underlying carotene pigments. These pigments are always present in the leaf, helping soak up the excess light energy that impinges on a leaf in bright sunlight and passing some of that energy on to the chlorophyll molecule for photosynthesis. But photosynthesis shuts down in the fall, with low air temperatures and short daylength, and chlorophyll stops being synthesized. Then, xanthophyll and carotene pigments absorb light in the blue, blue-green, green, and long red wavelengths, leaving the yellow and orange colors to be reflected to our eyes, and producing the kaleidoscopic show we call fall color.
Happy Halloween to all!