Plants use visible light for photosynthesis. Visible light ranges from low blue to far-red light and is described as the wavelengths between 380 nm and 750 nm. The region between 400 nm and 700 nm is what plants primarily use to drive photosynthesis and is typically referred to as Photosynthetically Active Radiation (PAR). Plant biologists quantify PAR using the number of photons in the 400-700 nm range received by a surface for a specified amount of time, or the Photosynthetic Photon Flux Density (PPFD) in the units μmol/s.
During photosynthesis, plants take in carbon dioxide (CO2) and water (H2O) from the air and soil. Within the plant cell, the water is oxidized, meaning it loses electrons, while the carbon dioxide is reduced, meaning it gains electrons. This transforms the water into oxygen and the carbon dioxide into glucose. The plant then releases the oxygen back into the air, and stores energy within the glucose molecules.