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LED supplemental lighting as plant photosynthesis research

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發表於 2014-1-1 20:07:46 | 顯示全部樓層 |閱讀模式
2, LED used in the cultivation of plant facilities

In 1964 the world's first successful development of the red LED , yellow LED after appear until 1994 blue, green LED was developed. But because of its brightness difference , expensive , etc. limitations, has been unable as a general source application. Over the past decade , as people semiconductor light-emitting materials research deepening of continuous improvement and development of new materials LED manufacturing process , the development of LED breakthrough has been made , the price dropped significantly , which used in plant cultivation research scholars from various countries have been gradually concerned . Especially after the successful development of ultra-high brightness LED , is widely used in studies of plant physiology or cultivated fields , such as light morphogenesis , photosynthesis and chlorophyll synthesis research.

Research culture 2.1, LED used in plant tissue

In plant tissue culture , photosynthetic photon flux density (PPFD: Photosynthetic Photon Flux Density), photoperiod and spectral distribution of plant photosynthesis and morphogenesis, plays an important role . Plant tissue culture mainly rely on electric light, electric light plant traditional bio energy efficiency is very low , heat, lighting accounts for about 65% of the total electricity cost of electricity is one of the highest in plant tissue culture of non- labor costs. Therefore, the use of plant tissue culture in providing LED lighting , light quality regulation and PPFD, not only to the regulation of plant tissue culture growth and morphogenesis , shorten training cycles, improve quality , and can significantly reduce energy consumption and reduce costs.

2.1.1 , red (620 ~ 660 nm) and far-red light (710 ~ 740 nm)

Impact on tissue culture LED plant growth red and far-red spectrum flux ratio (R / FR) on plant morphogenesis , regulation has an important impact on plant height . R / FR ratio control plant morphology has become an important evaluation parameter . Fujiwara and other studies have found , LED light source , the red LED and red LED light source far more influence than Fluorescent light built form plantlets and growth . Tanaka et al study found that the red LED orchid plantlets promote leaf growth but reduced the chlorophyll content of dry weight , stem and roots . Lian research showed that: In a separate red LED light, lily vitro culture growth index and lower dry matter accumulation bulbs , which alone leads to lower CO2 assimilation red light effects. This result confirms the findings Goins , such as the red LED will be used in the photosynthetic production of wheat. However, the red or far-red LED on the growth of the plant tissue culture reports are not consistent. Miyashita and other studies have found increased PPFD with red LED , potato plantlets stem elongation , chlorophyll content also increased , but the leaf area and dry weight of no significant difference. Nhut other studies show that the red LED light, strawberry leaf tissue culture stretching elongated petioles , stem elongation significantly , but reduced the chlorophyll content . Kim and other studies suggest that a single red LED or red LED + LED treatment under far-red light , chrysanthemum stem tissue culture too fragile stem elongation lead to other important indicators also reduced growth , on the whole is not conducive to the normal growth and development of plants. Hahn et al found that the inhibitory effect of digitalis red LED on stem growth of plantlets . These phenomena are considered to cause the red light is monochromatic light energy systems available Ⅱ Ⅰ and uneven distribution , thus inhibiting the growth of stems . In addition, the study PPFD were 45 μmol / (m2 · s) of different light quality LED bulbs on the experimental results orchids small irradiation , we found the red LED treatment on callus induction from fragments of the original bulb is the most effective.

2.1.2 , Blu-ray (450 ~ 470 nm) LED plant growth on tissue culture

Blu-ray reports considered directly or indirectly affect regulation and synthesis plant hypocotyl elongation enzymes , maturity and light form pores open, chloroplast built. However, a significant impact of the growth of a single blue LED plantlets reports are rare. Appelgen been reported , such as blue geranium plantlets strongly inhibited stem extension . Nhut other studies showed that the blue LED single leaf tissue culture treated strawberry minimum number , root length shortest , strawberry plantlets growth inhibition , but no blue LED radiation can cause uneven development and plantlet growth of strawberry . The effect on the growth and photosynthetic tissue culture raised under conditions of calla study found that before LED treatment, no significant differences in the dry quality and growth rate , but add blue LED treatment on chlorophyll content and plant height indicators have a significant positive effects. Tanaka et al study found that the red LED to promote the growth of orchid leaves but decreased chlorophyll content , but the blue LED has reversed this effect .

2.1.3 , the impact of a combination of red and blue LED plant growth on tissue culture

So far, there are many reports believe that red and blue LED combined to produce a positive impact on the growth and development of plant tissue culture is superior to monochromatic treatment . As Hahn and other studies have found that digitalis plantlets by a single red LED or blue LED treatment appear leggy phenomenon , but in the red and blue LED light composite robust growth . Other studies have found that a double butterfly genus of plant tissue culture to take root in the red LED under the best and worst in the blue LED under the root ; while in the complex of red and blue LED light, roots , fresh weight and chlorophyll content of plants composite indicator significantly better than monochrome LED and Fluorescent processing . Some studies show that red and blue LED combination can increase the net photosynthetic rate in order to improve plant growth and development because of the red and blue spectral energy distribution is consistent with the chlorophyll absorption spectrum . Kim et al found in red , blue chrysanthemum plantlets LED light irradiation composite net photosynthetic rate under the highest quality fresh , dried and leaf area to achieve maximum quality , minimum number of stomata , stomatal aperture max. Tanaka et al reported that in red, fresh weight and dry blue LED light irradiation orchid plantlets composite weight increase . Lian et lily bulbs in vitro culture experiments drawn , red, blue LED light is more suitable for complex growth of bulbs , bulb size, fresh , dry the highest quality and the number of roots . But about the red and blue LED combined ratio, different tissue culture plants as test material reported results of the study carried out not consistent . If Nhut such as the use of 80% blue LED red LED +20% of its portfolio on banana tissue growth and acclimatization significant promoting effect . And one for the study of eucalyptus plantlets found that the same proportion of red and blue LED , and with breathable membrane and rockwool substrates to achieve its sugar-free culture . Nhut , etc. and then found in 70% of the red LED +30% blue LED illumination , number of leaves of strawberry plantlets , root number , root length, fresh weight, dry quality and value of the largest growing transplanted into the soil it's best . Spathiphyllum plantlets subsequent studies have yielded similar results. Thus, the mass ratio of the different plants of different sensitivity to light exhibit different flexibility. In the study of fresh / dried quality indicators accumulation of potato plantlets found that collaborative alternating light control than intermittent lighting control , 45% blue LED red LED +55% growth effect for treatment of potato plantlets is optimal. In addition , studies have found that in 25% +75 % blue LED combinations of red , from orchids to induce callus small bulbs can be obtained in the original body of the highest incidence of corm .

Research facilities gardening 2.2, LED applied

Over the past decade , the rapid development of Chinese horticulture area , plant growth light environment control lighting technology has attracted attention. Horticultural lighting technology is mainly used in two ways: First, in the sunshine or less hours of sunshine a short time as a supplementary lighting plant photosynthesis ; Second, as a plant light cycles, light morphogenesis induced lighting.

2.2.1, LED supplemental lighting as plant photosynthesis research

Nichols and other research found that the traditional artificial light inside the greenhouse to produce too much heat , such as the use of LED supplemental lighting and hydroponic systems, air loop can be used to excessive heat and moisture can be removed , the power can be efficiently converted into effective photosynthetic radiation, the final conversion of plant material . In the application of LED frequency of 400 ms and 50 % duty cycle , the growth rate, photosynthetic rate lettuce have increased more than 20 percent , the study showed that the LED for plant factory is feasible. Yanagi other study found that , compared with the fluorescent lamps , the red LED on the growth effect is not obvious , after adding spinach morphology blue LED indicators improved significantly. Yorio and other studies have found that application of 90% red LED +10% blue LED lighting as a supplement , can significantly promote the growth of spinach, radishes and lettuce . Shin and other studies have found that the amount of sugar beet red and blue LED under bioaccumulation composite light-grown maximum gross beet roots accumulated the most significant factors and produce the highest sugar and starch accumulation in the hair roots . There are reports that compared with the control metal halide lamps , grown under red and blue LED light composite pepper stems, leaves anatomic significant changes occur . Choi and other studies have similar conclusions , in red and blue LED light-grown basil composite stems , leaves anatomical structural changes are significant differences in the metal halide lamp with a growing basil , and as PPFD increased photosynthetic rate increased basil . Heo marigold and sage on the microscopic structure observed with monochromatic blue or red LED compared to an increase in the number of holes in both red and blue LED light composite plants .

2.2.2, LED as light cycle plant , induction lighting Photomorphogenesis

Goins other study found that the red LED can delay flowering time in Arabidopsis . Heo other study found that red + blue LED effect on the induction of flowering cyclamen , 10h photoperiod treatment , the highest number of flower buds and flowering ; separate red or blue LED illumination reduces the flowering response , regulating the length and peduncle flowering , cut flower production and is conducive to the listing . Thus by light quality and photoperiod can regulate flowering and subsequent plant growth. Heo , etc. The results showed that: under fluorescent light + blue LED, Fluorescent + red LED, Fluorescent red LED light treatment + far , no dry Ageratum significant differences in quality ; fluorescent lamps and fluorescent lamps + under the red LED light treatment , and marigold plant height Ageratum no significant difference , but the maximum height Fluorescent + two plants under far-red light treatment ; compared to treatment with a single fluorescent lamps , fluorescent lamps + red + far-red LED and Fluorescent LED light treatment significantly improved composite marigold number of stomata .

2.3, LED research aerospace Ecological Life Support System used in

At present the international community generally believes that the establishment of Controlled Ecological Life Support System (Controlled Ecological Life Support System, CELSS) is the fundamental way to solve the long-term manned space life support issues. To establish good this system , one of the key technologies that must solve one of the higher plant cultivation techniques, one of the key issues in the space of higher plants cultivation is related to lighting technology. Based on the special requirements of the space environment , space higher plants cultivated sources used must have a high luminous efficiency, light output suitable for plant photosynthesis and morphogenesis , small size, light weight, long life, high safety and reliability record and no environmental pollution. Therefore , the application of light-emitting diodes in recent years, plant cultivation in space much attention. Xenon metal halide and found the two LED lighting systems can provide the required spectral energy distribution and uniform CELSS illumination , but using LED lighting system using the power conversion efficiency of more than 5 times the xenon metal halide lamp system. Guo Shuangsheng other study found that the normal growth of plants in space can be a certain red and blue LED combined with 90% red +10% blue LED tube is more appropriate. Kim et al study found that 24% green + blue + red (RGB) treatment promotes the growth , compared to the group treated with cool white fluorescent lamps , lettuce photosynthetic output RGB treatment group improved significantly lettuce .

3 , the prospects of LED used in the analysis of plant cultivation

The 21st century will be the century of ecological agriculture , and agriculture is one of the main ways the physical realization of ecological agriculture in many disciplines of knowledge in physics , optics plays a vital role in which , therefore , some scholars believe that the "light of the Century " coming. How lack of regulation in the particular circumstances of artificial sunlight green light for the implementation of the different " light fat" , not only to promote crop growth , but also to increase production , efficiency, quality , disease , pollution purposes, which for the promotion of Chinese Modern Agriculture the development has a very important practical significance. LED with its inherent advantages are attracting the attention of the world, particularly in lower global energy shortage fears rise again in the background. The LED used in plant cultivation areas has many advantages : it can provide a variety of complex spectra of pure monochromatic light and can provide the appropriate spectrum combined according to different crops and different growth stages ; has PPFD adjustable features that can simulate sunlight intensity changes ; emitting frequency and duty cycle can be adjusted to provide the high-frequency characteristics for light intermittent mode , help investigate the mechanism of photosynthesis and control out of the dark period , and can be expanded saving space. LED applied research in the field of plant physiology and plant cultivation has attracted worldwide attention . Japan and the United States as the representative of developed countries, not only in-depth study of the mechanism of regulation LED plant growth and development , research will focus more on the positive LED technology and products are widely used in the field of plant cultivation . American Research Center NASA facility as the LED fill light base Closed universe of life support systems related technology research . Studies in Japan Closed LED plant factory has entered the practical stage ; CCS plant growth produced by the company through the growth control system software to control LED lighting , to achieve automatic control of light quality ; new LED light source tissue culture vessel "Uni-PACK" also successfully developed tissue culture has improved space utilization , effective wavelength utilization and lighting efficiency, reduce production costs and other advantages of tissue culture . So far , LED application mechanism of China in the field of plant cultivation is still in its infancy. Learn from foreign research results, further in-depth study of the system used in China LED basic theory cultivation areas is necessary. It is worth noting that the combination of the desired spectrum of different plants in different growth stages , there are some differences in PPFD and photoperiod , although some foreign applications reported in the literature , such as red and blue LED spectra for different combinations of plant growth and morphogenesis impact study , but the lack of binding growth characteristics of different periods and different species , research and analysis of plant responses to the LED light quality -control mechanism , and therefore failed to give different plants in different growth stages the best LED spectral composition , reliable parameter PPFD and photoperiod and system data . In addition , although China is a big country of plant cultivation area , but in cultivation areas have developed proprietary LED technology products, basic or blank, the urgent need discipline and plant engineering disciplines work together researchers , developed in line with China 's actual production LED plant light, automatic lighting control systems, new plant growth regulating device and a large factory plant nursery facilities. With the development and production costs decreased year by year LED technology, especially with the start of China's semiconductor lighting project , I believe that in the near future , various technologies and LED -related products and production practices will be widely used in plant cultivation .
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