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
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.
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
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.
LED lights have several advantages over traditional lights：
1)LEDs can emit light in a narrow band, which helps to produce a specific (sometimes adjustable) spectrum;
2)LED generates less radiant heat;
3)The LED has a longer working life;