• Biotechnology and Bioprocess Engineering:BBE
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• v.6 no.3
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• pp.194-199
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• 2001

Chlorella kessleri cultivated in artificial wastewater using diurnal illumination of 12h light/12h dark (L/D) cycles. The inoculum density was 10(sup)5 cells/mL and the irradiance in light cycle was 45$\mu$mol㎡s(sup)-1 at the culture surface. As a control culture, another set of flasks was cultivated under continuous illumination. Regardless of the illumination scheme, the total organic carbon (TOC) and chemical oxygen demand (COD) was reduced below 20% of the initial concentration within a day. However, cell concentration under the L/D lighting scheme was lower tan that under the continuous illuminating scheme. Thus the specific removal rate of organic carbon under L/D cycles was higher than that under continuous illumination. This result suggested that C. kessleri grew chemoorganotrophically in the dark periods. After 3 days, nitrate was reduced to 136.5 and 154.1mg NO$_3$-N/L from 168.1mg NO$_3$-N/L under continuous illumination and under diurnal cycles, respectively. These results indicate nitrate removal efficiency under continuous light was better than that under diurnal cycles. High-density algal cultures using optimized photobioreactors with diurnal cycles will save energy and improve organic carbon sources removal.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.2
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• pp.7-12
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• 2005

When a light is projected upon a material, part of its radiant energy is absorbed and the rest is reflected or transmitted according to the nature of the material. The molecules of the substance absorbing a light obtains the radiant energy to make thermal reactions or photochemical reactions. Specially, photochemical reactions by ultraviolet(UV) radiation brings about photochemical degradation such as color change. Because the photochemical damage brings about a devaluation of material and once damaged, it is irretrievable, it is necessary to minimize the damage and conserve the native quality of a material by a protective lighting system. This paper presents the measurement and photochemical damage for UV radiation from light sources. We measured the optical radiations from artificial light sources and daylight, and we analyzed a functional relation between irradiance and UV radiation form the results.

• Horticultural Science & Technology
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• v.34 no.1
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• pp.84-93
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• 2016

Plant factories with artificial lights require a large amount of electrical energy for lighting; therefore, enhancement of light use efficiency will decrease the cost of plant production. The objective of this study was to enhance the light use efficiency by using filters to diffuse the light from LED sources in plant factory conditions. The two treatments used diffuse glasses with haze factors of 40% and 80%, and a control without the filter. For each treatment, canopy light distribution was evaluated by a 3-D ray tracing method and canopy photosynthesis was measured with a sealed acrylic chamber. Sixteen lettuces for each treatment were cultivated hydroponically in a plant factory for 28 days after transplanting and their growth was compared. Simulation results showed that the light absorption was concentrated on the upper part of the lettuce canopy in treatments and control. The control showed particularly poor canopy light distribution with hotspots of light intensity; thus the light use efficiency decreased compared to the treatments. Total light absorption was the highest in the control; however, the amount of effective light absorption was higher in treatments than the control, and was highest in treatment using filters with a haze factor of 80%. Canopy photosynthesis and plant growth were significantly higher in all the treatments. In conclusion, application of the diffuse glass filters enhanced the canopy light distribution, photosynthesis, and growth of the plants under LED lighting, resulting in enhanced the light use efficiency in plant factory conditions.

• Journal of Bio-Environment Control
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• v.8 no.4
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• pp.275-280
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• 1999

This study was conducted to investigate the effects of $CO_2$ concentration(310 or 950$\mu$ mol.mol$^{-1}$ ) and air current speed(0.3, 0.5, 0.7 or 0.9m.s$^{-1}$ ) on the growth and development of eggp1ant Plug seedlings (Solanum melongena L.) under artificial 1ighting. For the treatment of $CO_2$ enrichment, stem length and diameter, the ratio of stem length to stem diameter, plant height, leaf area, net photosynthetic rate, top dried weight were significantly different at 1% level. Stem length of plug seedlings decreased at the condition under enriched $CO_2$ and high air current speed above plug stand. Stem diameter of plug seedlings increased and plant height decreased with the increasing $CO_2$ concentration. Plug seedlings had maximum net photosynthetic rate at the air current speed of 0.7m.s$^{-1}$ . Net photosynthetic rate at $CO_2$ concentration of 950$\mu$mol.mol$^{-1}$ increased by 46% than those at 310$\mu$mol.mol$^{-1}$ . Thus $CO_2$ enrichment would be effective for the production of plug seedlings with high quality.

• KIEAE Journal
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• v.13 no.5
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• pp.43-50
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• 2013

Recent researches on plant factory system deal with the convergence of lighting technology, agricultural technology inclusive to the high-tech industries worldwide in order to respond to the decreasing crop harvest due to global warming and abnormal weather phenomena. However, the fundamental performance standard is not currently being introduced in the case of plants factory and its commercialization is not activated because of high initial investment and operating cost. Large portion of the initial investment and operating cost of a plant factory is ascribed to artificial light sources and thermal control facilities, therefore, innovation should be provided in order to improve the economics of the plant factory. As an alternative, new plant factory could harness solar thermal and geothermal systems for heating, cooling and ventilation. In this study, a natural light dependent multi-layer plant factory's thermal environment was analyzed with two-dimensional numerical methods to elicit efficient operation conditions for optimized internal physical environment. Depending on the supply air temperature and airflow rate introduced in the facility, the temperature changes around the crops was interpreted. Since the air supplied into the plant factory does not stay long enough, the ambient temperature predicted around the plating trays was not significantly different from that of the supplied air. However, the changes of airflow rate and air flow pattern could cause difference to the temperature around the planting trays. Increasing the amount of time of air staying around the planting trays could improve energy performance in case the thermal environment of a natural light based multi-layer plant factory is considered.

• Journal of Plant Biotechnology
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• v.42 no.3
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• pp.245-256
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• 2015

In the agricultural industries, LEDs are used as supplementary, as well as main lighting sources in closed cultivation systems. In cultivation using artificial light sources, various light qualities have been tried to supplement fluorescent lamps to promote plant growth and metabolism. Microarray analysis of Brassica rapa seedlings under blue and fluorescent mixed with blue light conditions identified changes in three genes of the glucosinolate pathway. This attracted attention as functional materials highly expressed 3.6-4.6 fold under latter condition. We selected four more genes of the glucosinolate pathway from the Brassica database and tested their expression changes under fluorescent light mixed with red, green, and blue, respectively. Some genes increased expression under red and blue mixed conditions. The Bra026058, Bra015379, and Bra021429; the orthologous genes of CYP79F1, ST5a, and FMOGS-OX1 in Arabidopsis, are highly expressed in Brassica rapa under fluorescent mixed with blue light conditions. Further, Bra029355, Bra034180, Bra024634, and Bra022448; the orthologous genes of MAM1, AOP3, UGT74B1, and BCAT4 in Arabidopsis, are highly expressed in Brassica rapa under fluorescent mixed with red light conditions. The various light conditions had unique effects on the varieties of Brassica, resulting in differences in glucosinolate synthesis. However, in some varieties, glucosinolate synthesis increased under mixed blue light conditions. These results will help to construct artificial light facilities, which increase functional crops production.

• Horticultural Science & Technology
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• v.28 no.4
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• pp.535-539
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• 2010

The formation and elongation of runners, growth of runner plants, and transplant propagation rates of 'Maehyang' strawberry were investigated at various photosynthetic photon flux (PPF) levels. Strawberry plants having $3.1{\pm}0.4$ leaves and $7.0{\pm}1.1mm$ of crown diameter were used as propagules and were cultured for 35 days in 9 transplant production modules using fluorescent lamps as artificial lighting sources. Applied PPF levels were $137.4{\pm}2.1$, $217.0{\pm}1.0$, and $274.7{\pm}8.4{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ as measured on the surfaces of empty shelves. The numbers of runners and runner plants per propagule were the greatest at $280{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ PPF. The runner plant propagation rate was 0.27 plant/day/propagule at $280{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, which was significantly greater than that of conventional propagation methods. Results indicate that high PPF levels promotes the formation of runners and runner plants of strawberry and that the rapid propagation method with high PPF levels can be feasible for production of vigorous transplants in a closed transplant production system.

• Journal of Bio-Environment Control
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• v.28 no.2
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• pp.143-149
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• 2019

This study was conducted to investigate the graft-taking and growth of grafted cucumber seedlings as affected by light quality and blink cycle of LED modules. Four light quality treatments, namely blue, red, blue+red, white LED and four blink cycle levels of 5s/5s, 7s/3s, 9s/1s and control were provided to investigate the effect of lighting quality and blink cycle on the graft-taking and growth of grafted cucumber seedlings. Photoperiod for the control was 12/12 h. Photosynthetic photon flux, air temperature, and relative humidity for healing were maintained at $100{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, $25^{\circ}C$, and 90%, respectively. There was no significant difference in graft-taking of grafted cucumber seedlings according to light quality except the blue LED with the blink cycle of 5s/5s. Regardless of the blink cycle, there was no significant difference in graft-taking of cucumber seedlings healed under red, blue+red, and white LED modules. These results implied that the effects of light quality and blink cycle on the graft-taking were not significant. Differences in the leaf length, leaf area, and fresh weight of cucumber seedlings healed blue or red LED with the blink cycle of 9s/1s were found to be significant. There was no significant effect of the blink cycle on the growth of cucumber seedlings healed under white LED modules. The prices of white LED are gradually falling due to increased demand. Considering the manufacturing unit price of white LED modules, the cost savings of 10-15% are expected as compared to the conventional blue/red LED modules. Therefore, it was concluded that the use of white LED modules will be economical as an artificial lighting sources for healing of grafted seedlings.

• Korean Journal of Environmental Agriculture
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• v.34 no.1
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• pp.38-45
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• 2015

BACKGROUND: For commercial production of greenhouse crops under shorter day length condition, supplementary radiation has been usually achieved by the artificial light source with higher electric consumption such as high-pressure sodium, metal halide, or incandescent lamps. Light-Emitting Diodes (LEDs) with several characteristics, however, have been considered as a novel light source for plant production. Effects of supplementary lighting provided by the artificial light sources on growth of Kale seedlings during shorter day length were discussed in this experiment. METHODS AND RESULTS: Kale seedlings were grown under greenhouse under the three wave lamps (3 W), sodium lamps (Na), and red LEDs (peak at 630 nm) during six months, and leaf growth was observed at intervals of about 30 days after light exposure for 6 hours per day at sunrise and sunset. Photosynthetic photon flux (PPF) of supplementary red LEDs on the plant canopy was maintained at 0.1 (RL), 0.6 (RM), and $1.2(RH){\mu}mol/m^2/s$ PPF. PPF in 3 W and Na treatments was measured at $12{\mu}mol/m^2/s$. Natural light (NL) was considered as a control. Leaf fresh weight of the seedlings was more than 100% increased under the 3 W, Na and RH treatment compared to natural light considering as a conventional condition. Sugar synthesis in Kale leaves was significantly promoted by the RM or RH treatment. Leaf yield per $3.3m^2$ exposed by red LEDs of $1.2{\mu}mol/m^2/s$ PPF was 9% and 16% greater than in 3W or Na with a higher PPF, respectively. CONCLUSION: Growth of the leafy Kale seedlings were significantly affected by the supplementary radiation provided by three wave lamp, sodium lamp, and red LEDs with different light intensities during the shorter day length under greenhouse conditions. From this study, it was suggested that the leaf growth and secondary metabolism of Kale seedlings can be controlled by supplementary radiation using red LEDs of $1.2{\mu}mol/m^2/s$ PPF as well as three wave or sodium lamps in the experiment.

• Journal of Bio-Environment Control
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• v.23 no.1
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• pp.19-25
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• 2014

In this study, we analyzed the growth characteristics of red lettuce under Light-emitting diode (LED) light environment as well as the change of vitamin C and anthocyanins of lettuce. We made five monochromatic light treatments (red 647 nm, 622 nm, blue 463 nm, 450 nm, White), six mixed red (R) and blue (B) light treatments (R : B = 9 : 1, 8 : 2, 7 : 3, 6 : 4, 5 : 5) and red + white, and three light treatments made according to photoperiod of LED with lighting sources ratio of red : blue (R : B = 8 : 2(18/06 h, 15/09 h, 12/12 h)). It was composed of totally 14 control beds. As a result, the red lettuce the most developed leaf height, leaf numbers and fresh weight under red single light, root length and leaf developed when grown under blue single light. Therefore, red light were related to above part of the lettuce, blue light were related to the growth of the underground part of lettuce. Case of the mixed light, leaf height, leaf numbers, fresh/dry weight of above and underground part were highest red + white light and root length and chlorophyll content were highest under red 7 : 3 blue light. Result of growing investigation by photoperiod, the red lettuce were considered to be most effective in 15/09 h (on/off). The content of anthocyanins; the single light source, mixed light and light irradiation period were highest under blue light (463 nm), red 7 : 3 blue and 18/06 h (on/off) light irradiation, respectively. The vitamin C showed the lowest content of $1.26mg{\cdot}L^{-1}$ under the white light, but showed the greatest content of $3.02mg{\cdot}L^{-1}$ for the control group.