A measurement of the amount of photosynthetically active light (400–700 nm) hitting a surface per second, expressed in micromoles per square meter per second (µmol/m²/s). Used to determine whether plants are receiving adequate or excessive light.
Mr. Q and Dakota performed live PPFD checks throughout the episode. In the CO2 room on level 5, they measured 500 µmol at the canopy center and ~400 at the sides. At plant canopy height, moving up 10 inches raised readings by 200 µmol. Outdoors in the greenhouse, overcast readings hit 1,000–1,300 µmol; full noon sun previously measured 2,000–2,500 µmol.