Effects of LED Light Quality on Plant Factories

With more and more LED lighting used in plant factory lighting, LED lighting ushered in a spring. Good light quality plays a key role in the healthy growth of plants. This paper focuses on the effects of different LED light qualities on plant growth and development.

 

Light is the basic environmental factor for plant growth and development. Light not only supplies energy for plant growth through photosynthesis, but also is an important regulator of plant growth and development. Different light quality or wavelength has different biological effects, including different effects on plant morphology and chemical composition, photosynthesis and organ growth and development.

 

Red light generally showed inhibition of internode elongation, promotion of tillering and increased accumulation of chlorophyll, carotenoids, soluble sugar and other substances. Red light promoted the growth of leaf area and accumulation of beta-carotene in pea seedlings; red light enhanced the activity of antioxidant enzymes and increased the content of pigment absorbed by near-ultraviolet light after pre-Red light applied near-ultraviolet light in lettuce seedlings, thereby reducing the damage of near-ultraviolet light to lettuce seedlings; strawberry full-light experiment showed that red light was beneficial to the extraction of beta-carotene. Content of organic acids and total phenols in strawberries.

 

Blue light can significantly shorten vegetable pitch, promote transverse extension of vegetables and reduce leaf area. At the same time, blue light can also promote the accumulation of secondary metabolites. In addition, blue light can alleviate the inhibition of red light on photosynthetic system activity and photosynthetic electron transfer ability of cucumber leaves, so blue light is an important factor affecting photosynthetic system activity and photosynthetic electron transfer ability. There are distinct species differences in the need for blue light in plants. The effect of Lan Guangzhong 470nm on anthocyanin and total phenol content was found in strawberry after harvest.

 

Green light has always been a controversial quality, some scholars believe that it will inhibit the growth of plants, resulting in short plants and reduce the yield of vegetables. However, there are also many studies on the positive role of green light on vegetables reported that low proportion of green light can promote the growth of lettuce; on the basis of red and blue light added 24% green light can promote the growth of lettuce.

 

Yellow light basically inhibits plant growth, and because many researchers incorporate yellow light into green light, there is little literature on the effects of yellow light on plant growth and development.

 

Ultraviolet light is generally shown to kill organisms, reduce plant leaf area, inhibit hypocotyl elongation, reduce photosynthesis and productivity, and make plants more susceptible to infection. However, proper supplementation of ultraviolet light could promote the synthesis of anthocyanins and flavonoids, promote the synthesis of polyphenols by adding a small amount of UV-B to Postharvest cabbage, and slow down the dissolution, mass loss and softening process of pectin in red pepper by UV-c treatment, thus significantly reducing the decay rate of red pepper and prolonging the quality of red pepper. It can also promote the accumulation of phenols 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 caused the phenotype of dwarf plants, small and thick leaves, short petioles, increased axillary branching and changes in root/shoot ratio.

 

Far red light is usually used in combination with red light. The effect of red light and far red light on plants can be mutually transformed and cancelled because of the structure of photopigment absorbing red light and far red light. When the white fluorescent lamp in the growth chamber was used as the main light source, the content of anthocyanin, carotenoid and chlorophyll was decreased, while the fresh weight, dry weight, stem length, leaf length and leaf width were increased by supplementing the far red radiation (emission peak 734 nm). The effect of supplementation of FR on growth may be due to the increase of leaf area and the increase of light absorption. Arabidopsis thaliana treated with low R / FR had thicker and thicker leaves and more biomass than that treated with high R / FR, and had more accumulation of soluble metabolites, thus improving cold resistance.