Light Sources Needed by Plants
Photosynthesis and light
Different wavelength sensitivity between human and plants
Light plays a critical role in the growth, development, blossoming, and fruit bearing of plants. Because plants' response to light spectrum has different characteristics from that of human eyes, light for plants is measured in different units.
The sensibility of human eyes varies by the wavelength and colour of light - highest to green light with the wavelength of 555nm and lower at any other wavelength that is either longer or shorter. Lumen (lm) and lux (lx) are the units of luminous flux and illumination. They are based on the vision of human eyes.
Plants are sensitive to blue and red lights. The following figure shows the absorption spectrum of plant leaves. In the measurement of plants, photosynthetic photon quanta flux density (PPFD) is usually used to evaluate how lighting affects plant leaves in photosynthesis. Its unit is μmol/m2/s.
Lights that are bright for human may not be so for plants.
Lumen (lm) and illumination (lx) are the units that are based on the relative luminous efficiency of human. They cannot reflect effective light intensity for plant cultivation.
(* Source: Mr. Goto, Graduate School of National University Corporation Chiba University)