In horticulture lighting there are biological, optical, and electrical parameters. Let's start with the biological basics. What does a plant need? A plant needs light. The photosynthetic active radiation (PAR) is the region from 400 nm (blue light) to 700 nm (red light). In this region, the plant absorbs the light and uses it for photosynthesis. The most important wavelengths here are 450 nm and 660 nm. In general, the plant can recognize light between 280 nm and 800 nm wavelengths. The 730 nm wavelength is one of the three most important wavelengths. To measure the efficacy of an LED, the customer will have to look at the PPE value (photosynthetic photon efficacy). This value refers to how efficient a lighting system is at converting electrical energy into photons of PAR.