Photosynthetically Active Radiation (PAR)

Photosynthetically Active Radiation (abbreviated as PAR) refers to the waveband of light between 400 and 700 nanometers (nm). This waveband correlates very well with the energy of photons that can stimulate photosynthesis in plants, and outside of this range, photons are less or not effective. Thus, this is the waveband used when the amount, or intensity, of photosynthetic light is measured or reported.