Light is the basic environmental factor for plant growth and development. It is not only the basic energy source of photosynthesis, but also an important regulator of plant growth and development. The growth and development of plants is not only restricted by the amount of light or light (photon flux density, photon flux density, PFD), but also by the light quality, that is, the light and radiation of different wavelengths and their different composition ratios.
The solar spectrum can be roughly divided into ultraviolet radiation (ultraviolet, UV<400nm, including UV-A320~400nm; UV-B280~320nm; UV-C<280nm, 100~280nm), visible light or photosynthetically active radiation (PAR, 400~700nm, including blue light 400~500nm; green light 500~600nm; red light 600~700nm) and infrared radiation (700~800nm). Due to the absorption of ozone in the stratosphere (the stratosphere), UV-C and most of the UV-B do not reach the Earth's surface. The intensity of UV-B radiation reaching the ground changes due to geographic (altitude and latitude), time (day time, seasonal variation), meteorological (cloud presence, thickness, etc.) and other environmental factors such as air pollution.
Plants are able to detect subtle changes in light quality, light intensity, length of light and direction in the growing environment, and initiate the physiological and morphological changes necessary to survive in this environment. Blue light, red light and far red light play a key role in controlling the photomorphogenesis of plants. Photoreceptors (phytochrome, Phy), cryptochrome (Cry), and photoreceptors (phototropin, Phot) receive light signals and induce growth and development of plants through signal transduction.
Monochromatic light as used herein refers to light in a specific wavelength range. The range of wavelengths of the same monochromatic light used in different experiments is not completely consistent, and other monochromatic lights that are similar in wavelength often overlap to different extents, especially before the appearance of a monochromatic LED light source. In this way, naturally, there will be different and even contradictory results.