How a Leaf Changes Color in Fall

Carotenoid pigments (figure 2): These pigments are also found in plastids. The carotenoids occur, along with the chlorophyll pigments, in tiny structures - called plastids - within the cells of leaves. Sometimes they are in such abundance in the leaf that they give a plant a yellow-green color, even during the summer. But usually we become aware of their presence for the first time in autumn, when the leaves begin to lose their chlorophyll.
Carotenoid yellow and orange color is in many living things, giving characteristic color to carrots, corn, canaries, and daffodils, as well as egg yolks, rutabagas, buttercups, and bananas. Their brilliant yellows and oranges tint the leaves of such hardwood species as hickories, ash, maple, yellow-poplar, aspen, birch, black cherry, sycamore, cottonwood, sassafras, and alder.