The earliest LEDs used in the world for plant cultivation were Mitsubishi Corporation of Japan. As early as 1982, there were reports on the use of red LEDs with a wavelength of 650 nm for the replenishment of greenhouse tomatoes.
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LED application in the field of plant cultivation
In 1991, Bula et al. used a red light 660 nm LED combined with a blue fluorescent lamp to carry out a cultivation test of lettuce (Lactuca Sa-tivaL) and succeeded. Tanaka et al. used LED to carry out practical research on plant cultivation, and discussed the effects of pulsed light irradiation period and duty cycle on plant growth.
The results show that plant growth can be accelerated by a duty cycle of 25% to 50%. Okamoto et al. use ultra-high brightness red LEDs and blue LEDs to properly grow lettuce when the red-blue ratio (R/B) is 2:1. Yanagi et al. used red LEDs and blue LEDs to investigate the effects of light quality and light quantity on lettuce growth and photomorphogenesis. The lettuce was cultivated in a pure blue LED (170 μmol·m-2·s-1) environment. Differentiated growth, although the weight of dry matter is less than that of pure red or red-blue light, plants under pure blue light appear to be more robust and healthy.
Lee et al. and Ladislav also used the intermittent light source generated by LED to produce algae, which is very effective. Kozai et al. used LED pulsed light to study the effects of lettuce growth and photosynthetic reactions. The results showed that under the condition of pulsed light with a period of 100 μs or less, the growth of lettuce was 20% higher than that under continuous light irradiation. Irradiation of lettuce with different frequency pulsed light accelerates its growth.
Heo et al. found that fluorescent light + red LED, fluorescent light + far infrared LED composite light treatment can significantly increase the number of stomata pores than single fluorescent light treatment. Wei Lingling et al. used red LED (660 nm) + blue LED (450 nm) to carry out the seedling test of cucumber. The results showed that the physiological indicators of cucumber seedlings were 7:1 when the red-blue ratio (R/B) of LED was 7:1. Optimal, LED energy consumption is 1:2. 73 compared with fluorescent lamps, energy saving effect is remarkable.
So far, LED has been successfully used in a variety of plant cultivation experiments, including: lettuce, pepper, courgette, wheat, spinach, tiger head orchid, strawberry, potato, white crane and algae [etc. With the deepening of LED research, more and more plant cultivation will be successful.
Conventional LED packaging method and application field