Effects of different spectra on the growth of the

Plant growth Code: the impact of different spectra on growth

with the hot development of LED plant lighting, people have increasingly in-depth research on LED spectra. It has become a new direction of plant factories to control the growth of plants and improve the quality of crops by changing the spectra

scientific experiments have proved that different wavelengths of light have different effects on plant growth. For example, blue violet light and blue light in visible light play a great role in plant growth and bud formation. This kind of light can inhibit the elongation of plants and make them form a short and thick shape; At the same time, blue violet light is also the most important light that governs cell differentiation; Blue violet light can also affect the phototropism of plants. Ultraviolet light can inhibit the formation of some growth hormones in plants, thus inhibiting the elongation of stems; Ultraviolet light can also cause phototropism sensitivity and promote the formation of anthocyanins like blue, purple and cyan in visible light. Both red light in visible light and infrared light in invisible light can promote the germination of seeds or spores and the elongation of stems. Red light can also promote the decomposition of carbon dioxide and the formation of chlorophyll

then, what are the effects of different wavelengths of light on plant growth? How to design the best light formula in plant lighting? Aladdin Center analyzed the impact of different spectra on plant growth by interviewing representative plant lighting manufacturers, and interpreted the plant growth code from the data

effects of different spectral bands on plant growth

Chen Xingang, project director of the crystal photoelectric marketing center, a professional plant lighting LED chip supplier, analyzed the effects of different spectra on plant growth from the perspective of plant physiology. He pointed out that the light quality and light quantity required by plant lighting refer to the color (wavelength), irradiation intensity, photoperiod and cumulative total light quantity of light respectively. Different pigment molecules in plants absorb different wavelengths, such as chlorophyll, which is well-known, absorbs photons for photosynthesis to form ATP and NADPH chemical energy, and other phytochrome affected by red light and far red light, Affected by blue light, cyrptochrome and phototropin... Regulate the germination, growth and differentiation of plant seeds, the movement and development of chlorophyll, the opening and closing of stomata, the induction of flowering, the synthesis of pigments, the activation of enzymes, the synthesis of proteins, China is a major producer of refractories, and other physiological phenomena

Source: Sullivan and Deng（2003） Developmental Biology 260: .

Zhang Qiang, senior engineer of Hongli Zhihui, pointed out that the spectrum has been changing since the plant seedling stage. So now the monochromatic plant lighting products developed by the packaging factory are not only red and blue light, but also green light, ultraviolet and infrared. For example, there is relatively more blue light in seeds during development. When the amount of green light is high, it will inhibit plant growth, and the appropriate supplement of about 20% green light will promote plant growth. The corresponding infrared light has little significance in promoting plant photosynthesis, but it will affect the "height" of plants. In order to better match the growth stage of plants, the products developed by the LED packaging factory are also quite rich in light bands, from UV - Blue - Green - red - infrared, which can be said to be full band coverage, and some products are matched with phosphors, so that lighting and lighting can be achieved

Luo tie, R & D Engineer of Yimei Xinguang (Beijing) Technology Co., Ltd., talked about the influence of lighting on plant growth from the stage development theory of plant growth. He pointed out that plant growth can be divided into the following stages:

1) vernalization stage. At this stage, plants are in the budding stage, temperature and humidity play a major role in the external conditions, and the influence of lighting is very small

2) illumination stage. After the plant sprouts and grows the first few green leaves, this stage begins. Chlorophyll converts water and carbon dioxide into organic matter through photosynthesis. At this stage, the length of light will directly affect the growth of plants and the formation of plant morphology, especially the development and formation of plant sexual organs - flowers

3) spectral stage. After plants grow to a certain stage, spectral components begin to play a major role in the development and growth of plants. At this stage, the role of spectra on plant growth is as follows:

at the same time, plants have different absorption of different spectra. The most absorption is orange red light, followed by blue violet light and ultraviolet light with wavelength of nm, while the absorption of green yellow light with wavelength of nm is less. Plants with different habits in different regions also have different abilities to absorb light. Positive plants can generally absorb more than 80% of the light falling on their leaves, while negative plants generally absorb only about 60% of the light

4) illumination stage. At this stage, light intensity is the key factor affecting plant growth. The effect of spectral content in light on plant growth gradually retreats to the second place. Its function is mostly to promote the development and maturity of fruits, such as Yulian, tomato and other plants, which must be exposed to sufficient light intensity in order to bloom and bear fruit

the influence of photoperiod and total light on plant flowering

at the same time, Chen Xingang, project director of Jingyuan photoelectric marketing center, also analyzed the principle of plant flowering from the perspective of photoperiod and how to use specific spectrum to affect the flowering period of plants

he said that after hundreds of millions of years of evolution, many species have developed. The lighting characteristics are mainly divided into three types: long day plant, short day plant and day neutral plant. In addition, there are double day long type, long day short type and short day long type. The figure below explains the influence of the length of the light cycle on flowering. It can be seen that the influence of the critical dark period is more important than the critical day length, that is, the flowering of nocturnal plants is determined by the length of the dark period, and the length of non light time

in addition to the influence of photoperiod, the above figure also shows the influence of different wavelengths. Whether it is to inhibit the flowering of short day plants or promote the flowering of long and short day plants, 660nm red light (R) can be used for treatment. If the red light is treated and then irradiated with 730nm far red light (FR), the interruption of red light night will be offset by far red light. Therefore, it can be seen that photosensitizers are also involved in the induction of plant flowering, which is likely to be bought at a high price

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another concept of photoperiod is the daily light integral (DLI), which is the daily light intensity multiplied by time to obtain the daily cumulative total light. Just like people eat three meals a day, the light needs to be evenly distributed rather than excessively concentrated. The regulation of the total light will have a negative impact on the growth and development of plants if it is exceeded or not

dli unit: mol/m2

dli=ppfd x time (SEC)

luminus China Marketing Director Zhu Ming finally pointed out that at present, due to various factors of time and resources, the so-called perfect matching scheme and products have not been achieved, but breakthroughs and improvements have been made in some fields. For example, more and more customers have begun to add UVA to the "traditional" plant lighting spectrum (450nm, 660nm, 730nm and white light), In order to form a new and richer functional spectrum, because many studies have shown that UVA can affect the color and insect resistance of plant growth, so the use of UV-A with appropriate intensity is also conducive to plant growth. More comprehensive and multi-functional spectra and products need more enterprises to continue research and development

the influence of different wave bands on the growth of plant lighting is obvious. At present, many manufacturers are also improving the product lines of plant lighting in different wave bands, but how to use this influence to design perfect light formula solutions may be the key to LED plant lighting in the future