Photosynthetically active radiation

From Glossary of Meteorology



photosynthetically active radiation

(Abbreviated PAR.) The electromagnetic energy in the 400– 700 nm wavelength range.

Measured as the photosynthetic photon flux (PPF) in quanta per second per square meter, or mole of quanta per second per square meter, or photosynthetic irradiance (PI) in watts per square meter for the specified wavelength band.