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What kind of LED lights does plants growth need ?

Author : Linda Wu

Update time : 2021-06-30 16:29:37

The first thing to know about plant lighting is that not all light can be used by plants, basically only blue and red light can be absorbed by plants.

Different kinds of light have different effects on plants
UVC: sterilization;
UVB: Inhibitory growth, limit stem growth and increase the content of secondary metabolites;
UVA: Enhance color and secondary metabolite content, including natural aromas;
460nm（B）: Helps plant root growth, the effect is most obvious in the early stage of the plant;
660nm（R）: Good for plant stem and leaves, flowering and fruit growth;
730nm（F）: It is beneficial to control the flowering period of plants and the synthesis of nutrients in the body.

Different light quality or wavelengths have different biological effects, including different effects on plant morphology and chemical composition, photosynthesis and organ growth and development.

different effects on plants

1. Red light
Red light generally inhibits interstitial elongation, promotes tillers, and increases chlorophyll, carotenoid, soluble sugar and other substances. Red light promoted the growth of leaf area of pea seedlings and β-carotene accumulation. It was found that red light could enhance the activity of antioxidant enzymes and increase the content of near-ultraviolet absorbing pigment, thus reducing the damage to lettuce seedlings caused by near-ultraviolet light. It was found that red light was beneficial to increase the contents of organic acids and total phenols in strawberry.

2. Blue light
Blue light can obviously shorten the pitch, promote the lateral extension and reduce the leaf area of vegetables. Meanwhile, blue light can promote the accumulation of secondary metabolites in plants. In addition, we found that blue light can reduce the inhibition of red light on photosynthetic system activity and photosynthetic electron transport ability of cucumber leaves, so blue light is an important factor affecting photosynthetic system activity and photosynthetic electron transport ability. There are significant species differences in the blue light requirement of plants. It was found that 470nm in different wavelengths of blue light had obvious effect on the content of anthocyanins and total phenols.

3. Green light
Green light has long been a controversial light quality, with some researchers claiming it inhibits plant growth, stunts plants and reduces the yield of vegetables. However, many studies have been reported on the positive effects of green light on vegetables. Low levels of green light can promote the growth of lettuce. Adding 24% green light to the red and blue light increased lettuce growth.

4. Yellow light
Yellow light basically inhibits plant growth, and since many researchers have incorporated yellow light into green light, there are very few literatures on the effects of yellow light on plant growth and development.

5. Ultraviolet light
Ultraviolet light is generally more destructive to organisms, reducing leaf, inhibiting hypocotyl elongation, reducing photosynthesis and productivity, and making plants more susceptible to infection. However, appropriate supplementation of UV light can promote the synthesis of anthocyanins and flavonoids, and a small amount UV-B can promote the synthesis of polyphenols in postharvest cabbage. Postharvest UV-C treatment can slow down the pectin dissolution, quality loss and softening process of red pepper, significantly reduce the decay rate of red pepper, prolong shelf life, and promote the accumulation of phenolic substances on the surface of red pepper.In addition, ultraviolet light and blue light also affect the elongation and asymmetric growth of plant cells, thus affecting the directional growth of plants. UV-B radiation results in stunted plant phenotypes, thick leaves, short petioles, increased axillary branching, and changes in root/crown ratio.

6. Far red light
Far-red light is usually used in proportion to red light. Due to the structure of photosensitive pigment of absorbing red light and far-red light, the effects of red light and far-red light on plants can be converted into each other and offset each other. When the white fluorescent lamp was the main light source in the growing room, LEDs were used to supplement the distal red radiation (emission peak 734nm), the content of anthocyanin, carotenoid and chlorophyll decreased, while the plant fresh weight, dry weight, stem length, leaf length and leaf width increased.The promoting effect of FR supplementation on growth might be due to the increase of light absorption caused by the increase of leaf area.Under low R/FR treatment, Arabidopsis thaliana had larger and thicker leaves, increased biomass,increased accumulation of soluble metabolites, which improved cold resistance compared with high R/FR treatment.

Due to the high cost of plant lighting lamps now, whether you want to avoid buying inferior plant lighting products, or want to do a good job as a LED plant grow lighting designer, you need to pay attention to the following indicators and performance:
1. Uniformity of illumination
2. Rationality of combination of light and mass
3. Heat dissipation reliability
4. Waterproof, dustproof and corrosion resistant
5. Power suitability
6. High efficiency of luminous surface
7. Visual comfort

Different kinds of plants require different levels of light uniformity. For this point, there are two indicators: "uniformity between plants" and "regional uniformity", these two indicators are generally required to reach 95% or even above 98% in order to be a qualified lamp. In addition, except the uniformity of light quantum flux, the uniformity of spectral distribution is also a point that cannot be ignored. In the design of optical design and plant lighting, these indicators play a pivotal role. As mentioned above, different plants need different light quality in different growth stages. Because different wavelengths of light have different effects on the growth of plants, different lamps need to be used to provide different wavelengths of light for plants, so it is necessary to reasonably match light of different light quality.

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