The unique advantages of LED make it one of the important light sources in plant tissue culture research. Since the 1980s, some countries in the world have begun to study the application of LED in plant tissue culture. Some institutions of higher learning and research institutes in China have begun research on this aspect and made some encouraging progress. This paper briefly summarizes the work done by LED in plant facility cultivation from the following aspects, and evaluates its application prospects in this field.
1. Effects of Light on Plants
Light is one of the most important environmental factors in plant growth. It not only provides radiation energy for plant photosynthesis, but also provides signal transduction for plants to regulate their development process. Plants are always in a changing light environment throughout their life cycle. In the long-term evolution, plants not only adapt to the changes of the light environment, but also interact with each other to change the surrounding light environment.
LED (light-emitting diodes), or light-emitting diodes, is a device that can effectively convert electrical energy into electromagnetic radiation . In 1962, a red-light semiconductor compound GaAsP was developed in the Joint Laboratory of GE, Monsanto and IBM. In 1965, the world's first commercially available infrared LED made of germanium materials was born. With the continuous progress of technology, the development of white LED is quite rapid in recent years. The luminous efficiency of white LED has reached 30 lm/W. The research results in laboratory can reach 60 lm/W, which is much higher than that of incandescent lamp and approaching to fluorescent lamp.
3. Application of LED Light Source in Plant Tissue Culture
The application of LED in plant tissue culture is based on the development of LED technology and the regulation of plant tissue culture environment. In the world, LED was first used for plant cultivation in Japan. As early as 1982, a red light LED light source with a wavelength of 650 nm was used to test tomato's supplementary light in greenhouse.  Later, LED was also applied to environmental regulation in plant tissue culture, and the role of LED in energy saving was discussed . At present, the application of LED in plant tissue culture mainly focuses on the effect of light quality and intensity on the growth of tissue culture seedlings, but less on the photoperiod. As far as the world is concerned, the application of LED in plant tissue culture mainly focuses on Japan and the United States. The research in Japan is in the leading position in the world. It not only develops LED light-emitting system specially applied to plant tissue culture, but also combines with other environmental regulatory factors to obtain some important basic data. Some Chinese scientific research institutions have also begun research in this field, and have developed some LED light source systems independently for plant tissue culture research.
4. Trend of development
LED is a new energy-saving and efficient light source. Using LED as light source in plant tissue culture can not only reduce the cost of tissue culture, but also make the study of plant photophysiology more in-depth because of its light quality, adjustable light intensity and narrow band. In the future, the application of LED in plant tissue culture should be strictly controlled from lighting devices, select appropriate LED, consider the performance and reliability and the special use conditions of plant lighting; combine the characteristics of LED, make rational use of LED, consider the rated working conditions of LED, design of driving circuit and selection of power supply, and combine with other factors of environmental control, such as CO2 fertilization, temperature control, etc. In addition, it should be combined with the use of plant growth regulators to make the application of LED in plant tissue culture more in-depth and systematic.