As the fourth-generation new lighting source, the LED has many characteristics different from other electric light sources, which makes it the first choice for energy conservation and environmental protection light source.
The LED in the field of plant culture also has the following characteristics: the wavelength type is rich, which coincides with the spectral range of plant photosynthesis and light form. The spectrum width is half wide and can be combined to obtain pure monochromatic light and composite spectrum according to the need. It is possible to focus a specific wavelength of light on the crops; It can not only regulate the flowering and fruity of crops, but also control plant height and plant nutrition. The system has little heating and little space, which can be used for multi-layer cultivation of three-dimensional combination system, which realizes low heat load and small production space. In addition, its strong durability also reduces operating costs. Because of these remarkable characteristics, LED is very suitable for plant cultivation in controlled environment, such as plant tissue culture, facility horticulture and factory seedling and aerospace ecological health protection system.
The facility horticultural lighting technology is mainly used in two aspects: first, it is the supplementary illumination for photosynthesis of the plant when the sunshine is short or the sunshine is short; Two, as the plant light cycle, the light form of the induced illumination.
1, LED as a supplementary lighting plant photosynthesis too much heat generated by the study of traditional artificial light, such as added using LED lighting and hydroponic system, air can be recycled, too much heat and moisture can be removed, electric energy can be efficiently transformed into effective photosynthesis radiation, eventually into the plant material. Studies show that LED lighting, growth rate and photosynthetic rate of lettuce are increased by more than 20%, and it is feasible to use LED in plant factories.
2. LED can influence the flowering time, quality and duration of flowering time of plants by inducing the specific wavelength of LED lighting as plant light cycle and light form. Some wavelengths of LED can increase the number of buds and flowers in plants; Some wavelengths of leds can reduce the floral response, regulate the length and duration of the pedicle, and facilitate the production and marketing of cut flowers. Thus, LED regulation can control the flowering and subsequent growth of plants.
3. Research on the application of LED in space ecological health protection system.
The establishment of a controlled ecological health protection system is the fundamental way to solve the problem of long-term human spaceflight, and the cultivation of higher plants is a key element of CELSS, and one of the key lighting.
Based on the special requirements of space environment, space light source must be used in higher plant cultivation has high luminous efficiency, output wavelengths is suitable for the plant photosynthesis and light morphogenesis, small volume, light weight, long service life, high safety and reliability record and no environmental pollution, etc. Compared with other light sources such as cold white fluorescent lamp, high pressure sodium lamp and metal halide lamp, the LED can effectively convert the light energy into photosynthetic effective radiation, and the effect of photosynthesis is better. In addition, it has the characteristics of long life, small size, light weight and solid state, so the LED is highly valued in ground and space plant cultivation.
Plants depend on the energy of light for photosynthesis to grow, blossom and bear fruit. But because often appear daedal nature changed due to climate change and the illumination, the plants in different growth period cannot be fully learned to their own needs during different growth photosynthetic nutrition, harm to growth, especially in seedling stage. In this regard, scientific and reasonable artificial spectra have created good absorption and reflection conditions for the growth of plants. The energy values of the blue and red areas are very close to the efficiency curve of plant photosynthesis (especially for green plant efficiency), which is the best light source for plant growth.
Led plant growth light adopted different from these measures, so as to avoid the there are varying degrees of problems, such as the lack of specific spectral composition of light qualitative analysis to handle is not pure, light intensity is not consistent, close to or even lower than the plant light compensation point, light light source, low energy efficiency. The results show that LED can solve these problems, especially suitable for artificial light control plant environment.