By Ian Ashdown, P. Eng. (Ret.), FIES Senior Scientist, SunTracker Technologies The phrase déjà vu translates from French as “already seen,” which nicely describes a current issue with horticultural lighting design.

By Ian Ashdown, Senior Scientist SunTracker Technologies Whereas human vision relies on five opsins as photoreceptors, most plants have a wide variety of photopigments that are responsive to optical radiation from 280 nm to 800 nm. Beyond photosynthesis, plants rely on this radiation to control photomorphogenesis, phototropism, shade avoidance, and both circadian and circannual rhythm entrainment.