Parameter Tree:
EARTH SCIENCE > BIOSPHERE > VEGETATION > PIGMENTS

Definition:
Pigments are light-absorbing molecules. In addition to chlorophyll,
other pigments, principally yellow and orange carotenoids, as well as
other forms of chlorophyll, are also present in green plants. These
molecules absorb light and then pass the energy to the chlorophyll a.
Accessory pigments, like the carotenoids, enable the plants to use more of
the light than is trapped by chlorophyll a alone.  


Reference:
Gould, J. and W.Keaton. 1996. Biological Science. W.W. Norton and Company. New
York, New York.