What Does Photosynthetically Active Radiation (PAR) Mean?
Photosynthetically active radiation (PAR) is the available light required for photosynthesis to take place. The wavelengths of photosynthetically active radiation that plants can use are generally in the range of 400-700 nanometers (nm).
Photosynthetically active radiation is absolutely essential for a plant to survive, and plants grow fastest in conditions of higher PAR. Plants germinate, grow, bloom, and produce fruit during the summer months when PAR is at its highest. But as the levels of PAR begin to drop towards autumn, plants slow their growth, dieback and eventually go dormant.
Photosynthetically active radiation is generated by the sun and commercially available plant grow lamps.