Which bands of spectrum are needed for plant growth?

The sensitivity of plants to the spectrum is different from that of the human eye. The most sensitive spectrum of the human eye is 555nm, which is between yellow and green light. It is less sensitive to the blue light zone and the red light zone. This is not true for plants, which are most sensitive to the red light spectrum and less sensitive to green light, but the difference in sensitivity is not as great as the human eye. The most sensitive area of plants to the spectrum is 400-700nm. This section of the spectrum is usually called the effective energy region of photosynthesis. About 45% of the energy of sunlight lies in this section of the spectrum. Therefore, if an artificial light source is used to supplement the amount of light, the spectral distribution of the light source should also be close to this range.

The energy of the photons emitted by the light source varies with the wavelength. For example, the energy of wavelength 400nm (blue light) is 1.75 times the energy of 700nm (red light). But for photosynthesis, the effect of the two wavelengths is the same. The excess energy in the blue spectrum that cannot be used for photosynthesis is converted into heat. In other words, the photosynthesis rate of plants is determined by the number of photons that the plant can absorb in 400-700nm, and is not related to the number of photons sent by each spectrum. However, most people generally believe that the color of light affects the rate of photosynthesis. Plants have different sensitivity to all spectra. This reason comes from the special absorption of pigments in the leaves. Among them, chlorophyll is the most known. But chlorophyll is not the only pigment useful for photosynthesis. Other pigments also participate in photosynthesis, so the photosynthesis efficiency cannot only consider the absorption spectrum of chlorophyll.