Application of LED light source in plant lighting and analysis of six major effects on plants

The research on the effects of LED lighting on plant growth and development has been carried out for many years, but scholars have studied it from the perspective of plant morphology. In recent years, this research has gradually turned to the field of the impact of LED lighting on the accumulation of functional chemicals in plants. This article reviews the latest developments in this area and points out the current problems and ideas and possible directions for future research for reference by researchers in the production and research sectors.

Among various environmental factors, light is one of the most important factors affecting plant growth and development and accumulation of functional chemicals (Kopselland Kopsell, 2008; Pérez-Balibrea et al., 2008). Plant growth and physiological indicators are strongly influenced by light (McNellis and Deng, 1995). The effects of light on higher plants are mainly manifested in two aspects: (1) providing the energy required for plant photosynthesis; and (2) regulating the growth, differentiation and metabolism of plants by receiving light signals (Wang et al., 2001). Different light qualities and light intensities have different effects on plants. In 1990, light-emitting diodes (LEDs) were first used in plant research (Bula et al., 1991) and proved to be a more efficient alternative to traditional light sources (Morrow, 2008). . Due to its low power consumption, narrow spectrum and low heat generation (Massaetal., 2008; Morrow, 2008; Wa-tanabe, 2011; Goto, 2012), after 2000, LED was quickly introduced as a more efficient light source. Plant factory. The method of controlling plant flowering and leaf morphogenesis by adjusting the distribution of LED spectra is not only simple, but also promotes an increase in the concentration of functional chemicals in plants (Goto, 2012).

Historically, the study of the effects of LEDs on plants began with plant morphology, and domestic researchers have done a lot of valuable work in this area. In recent years, researchers at home and abroad have begun to turn their research into the impact of LED on the accumulation of functional chemicals in plants, and have made great progress in many fields. This aspect of research is of great importance for the production of a variety of functional and medicinal plants with controlled output under the illumination of artificial light sources. This article reviews the latest research results for reference by researchers in the production and research departments. It also expects that China's research in this area will achieve more and better results.

First, LED and its application in plant lighting

LEDs are a special type of semiconductor diode. Depending on the semiconductor material used, the wavelength of light emitted by the LED can range from ultraviolet C (~250 nm) to infrared (~1 000 nm) (Bourget, 2008), and the wavelength range of light emitted by each LED can be very high. narrow. Thus, it is a very efficient plant illumination source with real spectrum control capabilities.

Unlike metal halide light sources, fluorescent lamps, and high pressure sodium lamps, the solid state lighting systems used in LEDs have some unique advantages. They are not only lightweight, small in size, long in service life, but also have the advantages of controllable wavelength and spectral composition, narrow bandwidth, low luminous surface temperature, low heat generation, high brightness, low radiation and high efficiency (Steranka et al., 2002; Narendran). And Gu, 2005; Spiazziet al., 2005; Tamulaitis et al., 2005; Cheng et al., 2006; Cheng and Cheng, 2006; Bourget, 2008; Massa et al., 2008; Morrow, 2008; Jang et al., 2012, 2014a, 2014b; Liu et al., 2014; Rodríguez-Vidal et al., 2014; Wu et al., 2014). These advantages of LEDs, especially the tunability of their spectrum, the constant innovation and maturity of technology, and the increasing use (and therefore the decreasing price) make it the first choice for plant illumination sources. At the same time, the luminous efficiency of LEDs is also increasing. For example, in 2006, the luminous efficiency of blue LED lamps was only 11%, and by 2011, it reached 49% (Mitchell et al., 2012). With the continuous advancement of technology and the continuous improvement of the technological level, the spectral control of LEDs will be more flexible in the future, and the manufacturing and use costs will be lower and lower, and its superiority will be more fully reflected (Massaet al., 2008; Morrow, 2008; Yeh and Chung, 2009; V?n-ninen et al., 2010).

These advantages also make LEDs gradually replace the status of traditional lighting sources (Jang et al., 2014a, 2014b) and are widely used in various fields such as displays, decoration, backlighting, communications, signage, general lighting and urban Night lighting, etc. (Tsao, 2004; Narendran and Gu, 2005; Shur and Zukauskas, 2005; Chengand Cheng, 2006; Brodrick, 2007; Fuet al., 2009; Juntunen et al., 2014; Ning et al., 2014).

In terms of plant lighting, LEDs are able to match the appropriate range of light waves to the plant's light receiver and affect the shape and composition of the plant (Morrow, 2008). For plants grown in a controlled environment, the superiority of LEDs also makes them the preferred source of light (Folta et al., 2005; Ilieva et al., 2010). In the area of ​​plant tissue culture, the use of LEDs has achieved remarkable results (Guptaand Jatothu, 2013).