Brief Introduction to the Principle and Prospect of Plant Growth Lights

In order to scientifically select light sources to better control the speed and quality of plant growth, we must choose artificial light sources that are closest to natural light and meet plant photosynthesis conditions. Measuring the "photosynthetic flux density PPFD" produced by a light source can help us understand the rate of plant photosynthesis and the efficiency of the light source. An ideal light source should have the following characteristics: high-efficiency electrical energy conversion capability, high radiation intensity within the effective range of photosynthesis (especially low infrared radiation), and a radiation spectrum that meets the physiological needs of plants. Among many artificial light sources, sodium lamps have become one of the most effective light sources in greenhouses to influence plant photosynthesis and promote correct growth due to their high energy conversion efficiency and superior spectral characteristics. Tubular sodium lamps can achieve high light efficiency radiation of 150lm/w and are currently the best choice to promote the growth of various crops. By increasing the sodium vapor pressure in the ceramic arc tube, it is possible to expand the spectral range of blue and red light, which is the high range of wavelengths pursued.

Among high-pressure sodium lamps used in horticultural products, brands such as PLANTASTAR (OSRAM), SON-T AGRO (PHILIPS), and LUCALOX XO (GE) perform outstandingly. They increase the higher 0-40% blue light range and activate the chlorophyll of plants. . In order to obtain the highest radiant energy, all sodium lamps are equipped with a reflective layer on the inner side of the lampshade.

In most domestic factories, sodium lamps used as street lamps are generally used as sodium lamps for plants. The export has caused a lot of losses to the majority of users. Light environment is one of the important physical environmental factors for plant growth and development. Controlling plant morphology through light quality adjustment is an important technology in the field of facility cultivation. Different wavelengths of light have different effects on plant physiological processes. For example, the 280nm ~ 315nm band has minimal impact on morphology and physiological processes; the 315nm ~ 420nm band has low chlorophyll absorption, affecting the photoperiodic effect and preventing stem elongation; 420nm ~ 500nm The (blue) band has the largest absorption ratio of chlorophyll to carotenoids and has the most significant impact on photosynthesis; the absorption rate of pigments in the 500 nm ~ 620nm band is not high; the 620nm ~ 750nm (red) band has a high chlorophyll absorption rate and has the most significant impact on photosynthesis and photoperiod The effect has a significant impact; while the band greater than 750nm is mainly converted into heat. The richness of these wavelength types coincides with the spectral range of plant photosynthesis and photomorphogenesis. The narrow half-width of the spectral wave width makes it possible to obtain pure monochromatic light and composite spectrum according to needs, concentrating light of specific wavelengths to uniformly illuminate crops. This not only helps regulate the flowering and fruiting of crops, but also controls plant height and nutrient content. The system generates less heat and takes up less space, making it suitable for multi-layer cultivation three-dimensional combination systems, achieving low heat load and miniaturization of production space.

Although sunlight is one of the indispensable factors for plant growth, its uncontrollability is also well known. For this reason, the application of artificial sunlight in horticultural cultivation is increasingly recognized. It can not only artificially control the growing season of plants, but also greatly shorten the growth cycle of plants. As supplementary lighting, artificial sunlight can enhance light intensity at any time and help plants continue photosynthesis. Especially in winter, extending effective lighting time is crucial to ensure the normal growth of plants. Whether it is dusk or night, artificial sunlight can provide a stable and reliable lighting environment, ensuring that plants grow healthily without being affected by changes in the external environment. In a greenhouse or plant laboratory, artificial light sources can completely replace natural light to create an ideal growing environment for plants. For the vast majority of growers, plant sodium lamps and metal halide lamps are the best light source options to replace sunlight. Metal halide lamps are rich in blue light components, which are suitable for the growth of early plant branches and leaves; while agricultural sodium lamps are rich in red-orange light components, which have a positive effect on promoting plant flowering and fruiting.

With the rapid development of facility horticulture area in my country, light environment control lighting technology for plant growth has attracted widespread attention. This technology is mainly used in two aspects: first, as supplementary lighting for plant photosynthesis when the amount of sunshine is small or the sunshine time is short; second, as induction lighting for the establishment of plant photoperiod and light form.