Parameter Tree:
EARTH SCIENCE > OCEANS > OCEAN OPTICS > PHOTOSYNTHETICALLY ACTIVE RADIATION

Definition:
Photosynthetically Active Radiation is the light in the whole wavelength
band from 400 nm (deep violet) to 700 nm (dark red) used by plants
in photosynthesis.  


Reference:
Open University. 1989. Seawater: Its Composition, Properties and Behavior.
Pergamon Press. England.