A brief introduction to the potential of LED light source and its spectral components in regulating horticultural crop production

Winter and early spring the short photoperiod and low light intensity environment is not conducive to the growth of greenhouse crops, so the artificial light usually is widely used in greenhouses to maintain normal photosynthesis of plants. High pressure sodium lamp is usually considered a greenhouse horticulture production of artificial light source is better, it can not only provide effective photosynthesis light to short wave mainly required for plant photosynthesis (400nm ~ 700 nm), but also the long wave emission (nm < 700). Naga Namihikaru affected plant temperature and greenhouse environment, which affected plant transpiration and morphological characteristics. However, due to the high concentration of sodium lamp spectral components in the red and yellow wavelengths, and the best spectral requirements of plant growth is still a big gap. In recent years, with the rapid development of science and technology, the new artificial light constantly, its spectral composition has been gradually optimized. LED light source is considered to be a revolutionary progress in horticultural production. The LED light source has the characteristics of monochromatic light, energy saving, good controllability and long service life, and can be used to form the spectrum of the plant after the combination of LED. Therefore, LED light source is considered to be the most ideal artificial light source in plant production. It is of great significance to promote the popularization and application of LED in horticultural production by a deep understanding of LED light source and its spectral components. LED light source spectrum of environmental control facilities under the condition of providing fast and accurate way to light plant growth is the most important environmental factor affecting nature. It is well known that light provides the source of energy for plant photosynthesis. In addition, light also affects plant growth and development. Such as light intensity and light quality (spectrum), the direction of the light, the light cycle of diurnal variation and annual variation can affect the seed germination, seedling establishment and morphological structure of adult plants and from vegetative to reproductive growth and transformation. The effect of light on the growth and development of plants depends largely on the spectral environment. In reality, in order to control the growth of horticultural crops, people usually adopt some auxiliary measures to change the spectrum under the conditions of environmental facilities to achieve its purpose, such as by different shading or artificial lighting and other measures to improve plant light environment. The advent of LED artificial light source will provide a fast and accurate way to control the spectrum environment under the condition of facilities. Referred to light, people usually think of first is light on Photosynthesis and dry matter yield. However, in the production of horticultural crops, this mindset has some limitations. First of all, the market value of many horticultural crops is not entirely determined by the size, quantity or weight of the product, and the appearance and intrinsic quality of horticultural crops also play an important role. Especially for high value-added floral crops, its market value is determined by its shape, and the external morphological characteristics of plant spectral environment plays a decisive role, such as to cultivate high-quality potted flowers, plants can be reduced by increasing the leggy red / far red ratio, so as to get some type of plant to improve its market value. For cut flower crops, the flowering period is controlled by the spectral environment (Figure 1). Therefore, the advent of LED artificial light source provides the possibility to produce high quality flower crops. In addition, recent studies have reported that the spectrum environment will also affect the internal quality of fruit and vegetable crops, such as the content of tomato fruit growth in the red and blue light environment can increase the vitamin C (Figure 2), but the spectral changes of internal quality of fruits and vegetables regulation is still in the preliminary study stage. Figure 1 LED light source used in the production of Gerbera Figure 2 LED light source control using LED light source quality of tomato canopy of fill in crop canopy light distribution is not uniform at the top of the canopy is much higher than that in the lower part of acceptance. Therefore, the leaves in the middle and lower leaves of the total leaf area of 80% of the total plant photosynthesis contribution is small. In addition, the photosynthesis of plant leaves showed a trend of saturation curve with the increase of light intensity. Therefore, the light intensity of the top leaves was lower. These phenomena lead at the top of the traditional light energy utilization rate is very low. The advent of LED light source provides the possibility to solve these problems. Since LED is a cold light source, it is possible to touch the plant tissue without being burned. In recent years, researchers use LED light carried out a series of studies on the canopy fill (Figure 3), the light in the canopy to solve the problem of uneven distribution, so as to improve the utilization rate of light energy. Holland scholars confirmed that using LED can improve yield of tomato canopy fill about 15%. Although the LED canopy light effect is obvious, but there are also some problems in its application, such as leaf easily twisted, thus affecting the canopy photosynthesis, which may be due to light quality does not meet the requirements of the plant the best ratio caused, therefore, the greatest potential for further research to solve these problems will play LED canopy light. Figure 3 LED light source light LED light source effect on canopy dry matter yield of light in biological research, photosynthesis and plant morphological characters are usually treated differently. However, from the point of view of plant dry matter production, there is a close relationship between them. The morphogenesis of plants has an important influence on the morphology and structure of plants. The plant morphological structure determines the light interception ability of the plant canopy, which affects the photosynthesis and dry matter yield. On the contrary, photosynthesis provides the energy for the formation of plant morphological structure. Light effect of plant dry matter yield reflected in two aspects: