What is Grow Light Spectrum?

  litescience          2021-09-29

In short, the definition of the spectrum is the component information contained in light. According to the energy corresponding to the photon (usually expressed by wavelength), light can be classified. The wavelength ranges from short to long, followed by three sections of ultraviolet light, visible light, and infrared light. Different colors of visible light correspond to different wavelengths of light. The spectrum is the ratio information for each wavelength component in the light. The general expression method is the wavelength on the abscissa and the relative intensity on the ordinate. Such as sunlight spectrum.

When we talk about the spectrum of grow lights, the term "lights" to refer to the visible wavelengths of the electromagnetic spectrum that humans can see, ranging from 380-740 nanometers (nm). Ultraviolet (100–400 nm), far red (700–850 nm), and infrared (700–106 nm) wavelengths are called radiation.

In terms of plant growth, we should pay attention to the wavelength related to plants. The wavelengths of plant detection include ultraviolet radiation (260 – 380 nm) and the visible part of the spectrum (380 – 740 nm), including PAR (400 – 700 nm) and far red radiation (700 – 850 nm).

How Does Each Spectrum Affect Plant Growth?

The growth of plants depends on many factors. Although different plants respond differently to the spectrum, there are still some rules that can be followed.

Outlines below is the application of different wavebands of horticultural, so that you can refer to it when trying out the spectrum in your own growth environment and selected crop varieties.

UV Light Wavelengths (10nm-400nm)

Ultraviolet is the general term of radiation with the wavelength of 10nm-400nm in the electromagnetic spectrum, which can not cause people's vision. It is invisible light with a higher frequency than blue violet light.

Ultraviolet can inhibit the formation of some growth hormones in plants, thus inhibiting the elongation of stems. At the same time, the phototropism sensitivity caused by ultraviolet can promote the formation of anthocyanins. The increase in ultraviolet forms the special shape of plants. The stems are short, the leaf surface shrinks, hairy antlers are developed, the accumulation increases, chlorophyll increases, anthocyanins exist in the stems and leaves, and the color is particularly bright. Long ultraviolet (320nm-380nm) can stimulate the growth of plants, increase crop yield and promote the synthesis of proteins, sugars and acids. The germination of seeds can be improved by irradiating seeds with long ultraviolet. Short ultraviolet (200nm-280nm) can inhibit the growth of plants, prevent plant overgrowth, disinfect and sterilize, and reduce plant diseases.

Blue Light Wavelengths (400nm-500nm)

Blue light is the necessary supplementary light quality of red light for crop cultivation and normal crop growth. The biological amount of light intensity is second only to red light. Blue light inhibits stem elongation, promotes chlorophyll synthesis, is conducive to nitrogen assimilation and protein synthesis, and is conducive to the synthesis of antioxidant substances. Blue light affects phototropism, photomorphogenesis, stomatal opening and leaf photosynthesis.

In the early stage of plant growth, blue light plays an important role. The irradiation of blue light can not only help some seeds to germinate, but also ensure the strong growth of their rhizomes. This is due to the fact that blue light can promote plants to produce more chlorophyll, help seedlings better absorb and use the energy in photosynthesis, enable plants to grow and mature faster.

Green Light Wavelengths (500nm-600nm)

Green light was once mistaken for physiologically invalid light and was not needed for plant growth. Studies have shown that although plants absorb less green light, it does not mean that plants do not need green light.

In the light environment required for plant growth, if there is too much green light, the plant grows slowly and the shape is not good; if there is too little green light, the leaf of the lower layer of the plant are prone to yellowing prematurely, and the leaves senescence prematurely. Green light has strong penetrating properties. Therefore, adding a suitable proportion of green light during plant growth can alleviate the problem of premature senescence of the lower leaves and improve the quality of the plant to a certain extent.

In addition, green light and red and blue light can be harmoniously adjusted to adapt to the growth and development of plants. The green light effect is usually the opposite of the red and blue light effects. For example, green light can reverse the stomatal aperture (opening and closing of plant pores that make gas exchange possible) promoted by blue light, etc.

Red Light Wavelengths (600nm-700nm)

Chlorophyll, the basic photosynthetic pigment of plants, mainly absorbs and transforms red and blue light, which are the basic energy of photosynthesis.

Red light is the first light quality used in crop cultivation experiment, and it is the necessary light quality for normal crop growth. The amount of biological demand ranks first among all kinds of monochromatic light quality, and the most important light quality in LED grow light source. Red light can promote stem elongation and carbohydrate synthesis, so as to greatly enhance plant photosynthesis and promote plant growth, but too much will cause plants to increase branches and overgrowth. However, adding an appropriate amount of blue light to balance red light can make plants more compact.

In conclusion, it is always important to consider various ways in which different wavelengths of light affect each other.

Far-red Light Wavelengths (700nm-850nm)

Far-red light is mainly used as a signal light for plant growth, regulating the physiological activities of plants such as avoiding shade and flowering.

Although far-red light has little significance for photosynthesis, its intensity and its ratio to 660nm red light play an important role in the morphogenesis of crop plant height and internode length. Plant morphology and height were controlled by light quality regulation and R / FR ratio. When the ratio increases, the plant stem node spacing decreases, the plant dwarfs, and the breeding plants tend to elongate. The change of ratio also has different effects on axillary bud differentiation, chlorophyll content, stomatal index and leaf area. Plants' selective absorption of red light and selective transmission of far- red light make plants under shade in a far-red enriched light environment.

Based on the above, growers can make comprehensive considerations in combination with the planting environment and plant varieties to be planted. If you have more ideas about the spectrum of plant lights that need to be realized, Lite Science is happy to explore with you.

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