• Journal of Bio-Environment Control
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• v.21 no.3
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• pp.180-185
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• 2012

The objective of this study was carried out to elucidate the effect of LEDs (light emitting diodes) irradiation in relation to early growth and inorganic elements in leaf lettuce (Lactuca sativa L. 'Rollo Rosa'). In morphological changes of leaves, shoot elongation and hypocotyl length showed poor growth in red light irradiation, while the red + blue light irradiation induced shorter plant height and much greater leaf numbers resulting in increased fresh weight. In change of the Hunter's color and SPAD values, lettuce seedlings grown under in red + blue and fluorescent light irradiation had a higher $a^*$ value, otherwise SPAD values were not changed in these light irradiations. Interestingly, relative chlorophyll contents showed 1.8 times increased redness in the treatment of red + blue light irradiation. Inorganic element (N, Ca, Mg, Mn, and Fe) and ascorbic acid contents were increased in lettuce plants grown under LEDs light irradiation compared to those of lettuce grown under the fluorescent light which showed higher P and Mn contents. In conclusion, it is considered that red + blue light irradiation which stimulates growth and higher nutrient uptake in leaf lettuce could be employed in containers equipped with LEDs.

• Journal of Life Science
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• v.24 no.2
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• pp.148-153
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• 2014

The objective of this study was to elucidate the effect of light-emitting diode treatment on early growth and inorganic elements in leaf lettuce (Lactuca sativa L. 'Oak Leaf'). In changes to leaf morphology, shoot elongation and hypocotyl length showed poor growth under red light irradiation, while red+blue light irradiation induced shorter plant height and more leaves, resulting in increased fresh weight. With respect to Hunter's color and SPAD values, lettuce seedlings grown under red+ blue and fluorescent light irradiation had a higher $a^*$ value but showed no other changes to SPAD values. Interestingly, redness in relative chlorophyll content was 1.4 times higher under red+blue light irradiation. Inorganic element (N, Ca, Mg, and Fe) and ascorbic acid concentrations increased in lettuce plants grown under LED light irradiation compared to those of lettuce grown under fluorescent light, which showed a higher P content. In conclusion, red+blue light irradiation, which stimulates growth and higher nutrient uptake in leaf lettuce, could be employed in containers equipped with LEDs.

• Korean Journal of Environmental Agriculture
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• v.38 no.4
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• pp.225-236
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• 2019

BACKGROUND: Hydroponics is one of the methods for evaluating plant production using the inorganic nutrient solutions, which is applied under the artificial light conditions of plant factory system. However, the application of the conventional inorganic nutrients for hydroponics caused several environmental problems: waste from culture mediums and high nitrate concentration in plants. Organic nutrients are generally irrigated as a supplementary fertilizer for plant growth promotion under field or greenhouse conditions. Hydroponic culture using organic nutrients derived from the agricultural by-products such as dumped stems, leaves or immature fruits is rarely considered in plant factory system. Effect of organic or conventional inorganic nutrient solutions on the growth and nutrient absorption pattern of green and red leaf lettuces was investigated in this experiment under fluorescent lamps (FL) and mixture Light-Emitting Diodes (LEDs). METHODS AND RESULTS: Single solution of tomatoes (TJ) and kales (K) deriving from agricultural by-products including leaves or stems and its mixed solution (mixture ration 1:1) with conventional inorganic Yamazaki (Y) were supplied for hydroponics under the plant factory system. The Yamazaki solution was considered as a control. 'Jeockchima' and 'Cheongchima' lettuce seedlings (Lactuca sativa L.) were used as plant materials. The seedlings which developed 2~3 true leaves were grown under the light qualities of FL and mixed LED lights of blue plus red plus white of 1:2:1 mixture in energy ratio for 35 days. Light intensity of the light sources was controlled at 180 μmol/㎡/s on the culture bed. The single and mixture nutrient solutions of organic and/or inorganic components which controlled at 1.5 dS/m EC and 5.8 pH were regularly irrigated by the deep flow technique (DFT) system on the culture gutters. Number of unfolded leaves of the seedlings grown under the single or mixed nutrient solutions were significantly increased compared to the conventional Y treatment. Leaf extension of 'Jeockchima' under the mixture LED radiation condition was not affected by Y and YK or YTJ mixture treatments. SPAD value in 'Jeockchima' leaves exposed by FL under the YK mixture medium was approximately 45 % higher than under conventional Y treatment. Otherwise, the maximum SPAD value in the leaves of 'Cheongchima' seedlings was shown in YK treatment under the mixture LED lights. NO₃-N contents in Y treatment treated with inorganic nutrient at the end of the experiment were up to 75% declined rather than increased over 60 % in the K and TJ organic treatment. CONCLUSION: Growth of the seedlings was affected by the mixture treatments of the organic and inorganic solutions, although similar or lower dry weight was recorded than in the inorganic treatment Y under the plant factory system. Treatment Y containing the highest NO₃-N content among the considered nutrients influenced growth increment of the seedlings comparing to the other nutrients. However effect of the higher NO₃-N content in the seedling growth was different according to the light qualities considered in the experiment as shown in leaf expansion, pigmentation or dry weight promotion under the single or mixed nutrients.

• Journal of Bio-Environment Control
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• v.31 no.3
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• pp.180-187
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• 2022

In order to select suitable light in a plant factory, electric energy use efficiency and light use efficiency should be considered simultaneously to consider operating costs as well as quantitative and functional aspects. The growth characteristics, electric energy use efficiency, light use efficiency by light intensity, LED ratio, and photoperiod conditions were compared together. Light intensity is 60, 130, 230, and 320 µmol·m^-2·s^-1 treatments, and light quality is the mixing ratio of red light and blue light 8:2, 6:4, 4:6, and 2:8 treatments. Photoperiod is 9, 12, 15, and 18 hours treatments based on the daytime. In the light intensity experiment, the growth rate increased as the light intensity increased, but there was no significant difference in the light use efficiency. When comparing the leaf fresh weight per power consumption, only the 320 µmol·m^-2·s^-1 treatment group showed significantly low efficiency, and there was no significant difference in the other treatments, so 230 µmol·m^-2·s^-1, which produced the most, was the most efficient. In the light quality experiment, the ratio of red light and blue light was measured to be high at the same time as the growth rate and light use efficiency in RB 8:2, and there was no significant difference in color difference and flavonoids content, so a Red:Blue ratio of 8:2 was the most suitable condition. In the photoperiod experiment, the longer the photoperiod, the higher the growth rate. However, there was no significant difference in the growth rate over 12 hours of daytime, so 12 hours considering the light consumption efficiency was a suitable condition. Based on the above results, LED light environmental conditions for perilla growth in plant factories were light intensity, light quality, and day length of 230 µmol·m^-2·s^-1 or more, 8:2, and 12 hours or more, respectively.

• Journal of Bio-Environment Control
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• v.18 no.4
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• pp.370-376
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• 2009

To produce uniform seedlings of tomato and cucumber with inexpensive way, their seedling quality by different light sources was investigated. The raising of seedling was performed by red LED (light emitting diodes), blue LED, red-blue mixed LED or fluorescent light with a fixed PPF(photosynthetic proton flux) level, about $40{\sim}60{\mu}mol{\cdot}m^{-2}{\cdot}sec^{-1}$. In the both tomato and cucumber, the rapid extension of hypocotyledonary axis was observed in Blue LED than fluorescent light, but opposite result was found in Red and mixed LED. During the nursery period of tomato and cucumber, the fresh weight was the highest in Red LED as 74% increasement in tomato and 74% in cucumber. In the case of seedling quality after the tomato nursery, there was no difference in the positions of 1st flower cluster and the number of bearing-flower per flower cluster by each light source. In case of cucumber, until 20th node, the setting ratio of female flower was higher in LED than fluorescent treatment, and also more healthy fruit setting was found in LED. Therefore, we assume that the Red or mixed (Red 2 + Blue 1) LED is more favorable to produce high quality tomato and cucumber seedlings in closed nursery facility.

• Korean journal of food and cookery science
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• v.31 no.4
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• pp.505-509
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• 2015

Light emitting diodes (LED) are able to selectively control the wavelength of light, enabling them to enhance photosynthesis by increasing specific wavelengths. The objectives of this study were to determine the effects of LED light exposure with various wavelengths (630 nm: 550 nm: 450 nm=8:1:1) on plant growth and bio-active compound concentrations in cherry tomato and red cabbage. With cherry tomatoes, LED decreased the number of fruits compared to fluorescent light (FL) but resulted in a significantly higher value in the total weight of the fruits and in sugar content. However, lycopene contents were not significantly different between the groups. With red cabbages, the weight and length were both significantly higher in the LED group than in the FL group. Furthermore, the anthocyanin contents in the red cabbage LED group were two times higher than those of the FL group. These results suggested that exposure to LED light with a high ratio of red wavelength can increase the anthocyanins contents in red cabbages but not the lycopene content in cherry tomatoes. Further studies will be needed to determine which LED wavelength can enhance lycopene content in cherry tomatoes.

• Korean Journal of Environment and Ecology
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• v.30 no.5
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• pp.821-828
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• 2016

We examed physiological and flowering response of S. capitata, the endangered plant in Korea, under LED light conditions in plant factory to cultivate artificially for conservation. We cultivated S. capitata and measured its physiological responses and the number of flowers under red, blue, white, red+far-red mixed, red+blue mixed, and red+blue+white mixed light. The results showed that its photosynthetic rate and chlorophyll content were recorded relatively high in red+blue+white and red+blue mixed light respectively. Transpiration rate and stomatal conductance appeared relatively high in the white single light while water use efficiency was no difference. Photochemical efficiency of photochemical photosystem II by minimum and maximum chlorophyll fluorescence was the highest in the red+blue+white mixed light condition than other ones. The number of flowers of S. capitata was at its peak under the red light or red+far-red mixed light. Therefore, we conclude that the most efficient way to grow for flowering of S. capitata is to provide red light or red+far-red mixed light in the plant factory.

• KIEAE Journal
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• v.13 no.2
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• pp.61-66
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• 2013

This study is to eliminate the need for conventional high density plant factory's artificial light source such as LED to reduce the initial investment of the light source installation as well as the operation cost. Use of solar light could enhance the quality of the vegetables similar to those grown in the natural environment. Provision of solar light into the multilayer vegetable cultivation facilities and collecting maximum and sustainable sunlight without too much loss by tracing solar path and properly distributing it through careful control during daytime are crucial for realizing the investigated rooftop light shelf system for multi-layered vegetable cultivation. In this study, we developed an innovative way of effectively allocating sunlight inside even to otherwise shaded zone of a multi-layer vegetable cultivation facility. To prove the effectiveness of the system's sunlight collection and distribution capability, both simulation and experiment in Daejeon are performed and the outcome is analyzed.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.123-123
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• 2017

식물공장 내 작물의 생육은 제공되는 인공광원의 광원 및 광질에 영향을 받으며, 광흡수 파장에 따라 다르다. 또한 광합성에 효과적인 형태의 빛의 계속적인 빛의 조사보다는 광 펄스를 조절하여 공급하여 준다면 더욱더 효과적인 생육 환경을 제공해 줄 수 있다. 식물의 최적 생장을 위해 특정 파장대의 빛을 선택적으로 조사할 수 있는 LED특성을 사용하여 UV광원을 포함한 인공광원의 펄스폭 변조에 따른 적치마 상추의 생육특성을 알아보고자 하였다. 광환경은 Red(660 nm), Blue(450 nm), UV(395 nm) LED를 8:1:1 비율로 광량 $160{\mu}mol{\cdot}m^2{\cdot}s^{-1}$, 주파수 1.25, 2.5, 3.75, 5.0 kHz로 조사하여 주었으며, 온도 $20{\sim}23^{\circ}C$, 습도 50~60%, $CO_2$농도 1,000 ppm으로 조성하여 주었다. 아시아종묘 적치마상추를 파종 후 18일 째 되는날 정식, 정식 후 14일 28일 째 되는날 SPAD, 지상부 지하부의 생체중 및 건물중, 엽폭, 엽장을 측정하였으며, 측정한 엽폭과 엽장을 이용하여 엽형지수 산출, 지상부 지하부 생체중 값을 이용하여 S/R율을 산출하였다. SPAD 측정결과 생육시기가 증가할수록 SPAD함량은 감소하였으며, 1.25와 2.5 kHz에서 생육 시기 증가에 대한 SPAD함량 감소가 컸고, 3.75와 5.0 kHz의 경우 SPAD함량의 감소량은 작았다. 지상부 생체중은 3.75 kHz에서 121.51 g으로 가장 높은 값을 나타냈으며, 2.5, 1.75, 5.0 kHz 순으로 높은 값을 나타났다. 지하부 생체중의 경우 3.75 kHz에서 31.31 g으로 가장 높은 값을 나타냈으며 2.5, 5.0, 1.25 kHz 순으로 높게 나타났다. 엽형지수는 생육 시기가 증가에 따라 감소하는 것으로 나타났으며, 1.75, 2.5, 5.0, 3.75 kHz 순으로 크게 나타났다. 지상부 건물중 측정결과는 지상부 생체중 결과와, 지하부 건물중의 측정결과는 지하부 생체중 결과와 동일하였다. S/R율은 1.75 kHz를 제외하고 생육시기가 증가할수록 S/R율은 감소하는 것으로 나타났으며, 주파수가 높아질수록 S/R율은 감소하는 것으로 나타났다. 엽형지수는 엽폭/엽장으로 엽형지수를 산출한 결과로 값이 작을수록 엽폭이 넓은 형태를 의미하며, 생체중값이 가장 크게 나타났던 3.75 kHz에서 엽형지수의 값이 가장 낮게 나타났으며 3.75 kHz를 제외하고 주파수가 높을수록 엽형지수의 값이 낮게 나타났다. 이에 주파수에 따른 적상추의 생육은 3.75 kHz에서 가장 좋은 것으로 판단할 수 있었다.

• Journal of Bio-Environment Control
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• v.22 no.4
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• pp.392-399
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• 2013

This study aimed to investigate responses of photosynthesis, plant growth, and phytochemical contents to different artificial light sources for 'Seneca RZ' and 'Gaugin RZ' two butterhead lettuce (Lactuca sativa L.). In this study, fluorescent lamps (FL), three colors LEDs (red, blue and white, 5 : 4 : 1; RBW) and metalhalide lamps (MH) were used as artificial lighting sources. Photoperiod, air temperature, relative humidity, EC, and pH in a cultivation system were maintained at 16/8 h, $25/15^{\circ}C$, 60~70%, $1.4{\pm}0.2dS{\cdot}m^{-1}$, and $6.0{\pm}0.5$, respectively. The photosynthetic rate of both two butterhead lettuce were the highest under RBW in middle growth stage. However, in late growth stage, the photosynthetic rate of both two butterhead lettuce were higher under RBW and MH than FL. The light sources showed significant results for plant growth but those effects were different to variety. Fresh and dry weight of 'Gaugin RZ' butterhead lettuce under MH were heavier than other lights in all growth stages. Growth of 'Seneca RZ' butterhead lettuce was maximized highest under MH in middle growth stage and FL in late growth stage. In the leaf tissue of 'Seneca RZ' butterhead lettuce, tipburn symptom occurred under all light sources and in the leaf tissue of 'Gaugin RZ' butterhead lettuce, it occurred under two light sources except for fluorescent lamps in late growth stage. kinds of lamp affect plant growth more than plant quality. Relative growth rate of both two butterhead lettuce was faster in middle growth stage than late stage. Growth of 'Gaugin RZ' was shown by kinds of lamp in middle growth stage and but it was not significantly affected by light sources and variety in late stage. Most of the phytochemical contents of two butterhead lettuce were significantly affected by different light sources. Contents of all vitamins showed higher than other light sources on RBW for both two lettuce, especially ${\beta}$-Carotene content of 'Gaugin RZ' was the highest. Plant growth, photosynthesis, and phytochemical contents were observed significant effects by different light sources for two butterhead lettuce but those effects were highly different between variety and kinds of phytochemicals. Therefore, the selection of optimum light source should be considered by variety and kinds of phytochemicals in the plant factory.