• Horticultural Science & Technology
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• v.31 no.1
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• pp.56-64
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• 2013

Recent unusual weather due to global warming causes shortage of daily sunlight and constitutes one of the primary reasons for agricultural damages. LED light sources are frequently utilized to compensate for the shortage of sunlight in greenhouse agriculture. The present study is aimed at evaluating formations of phytochemicals as well as growth characteristics of mature strawberry fruits ('Daewang' cultivar) during cultivation in a closed growth chamber equipped with artificial LED light as a sole light source. Each LED light of blue (448 nm), red (634 and 661 nm) or mixed blue plus red (blue:red = 3:7) was separately supplied and the intensity of each light was adjusted to $200{\pm}1{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ at plant level with a photoperiod consisted of 16 hours light and 8 hours darkness. Strawberries grown under mixed LED light of blue and red wavelengths showed a higher production of fruits than those grown under other LED treatments. Fructose, one of the free sugars, increased in mixed LED light-grown fruits. Anthocyanin contents were elevated remarkably in the mixed LED light-grown fruits compared with those in other LED treatments. Contrastingly, contents of total phenolics and flavonoids were not of much different from one another among the fruits treated with various LED lights. On the other hand, ripening of strawberry fruits was found to be faster when grown under blue LED light compared with other LED treatments. Moreover, antioxidant activities of blue or red LED light-grown fruits, respectively, were significantly higher than those of mixed LED light-grown fruits. We suggest that when daylight is in shortage during cultivation in a greenhouse, supplementation of sunlight with LED light, which is composed of blue and red wavelengths, could be useful for the enhancement of productivity as well as of free sugar content in strawberry fruits. In addition, for the strawberry culture in the plant factory, selective adoption of LED light wavelength would be required to accomplish the purpose of controlling fruit maturation time as well as of enhancing contents of sugars and antioxidants of fruits.

• Journal of Bio-Environment Control
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• v.25 no.3
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• pp.139-145
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• 2016

The objective of this study was to compare the growth and light use efficiency of red leaf lettuce grown under three types of combined light-emitting diodes (LEDs) and fluorescent lamps (FL) in a closed-type plant production system. The eighteen days-old lettuce seedlings of red leaf lettuce (Lactuca sativa L., 'Jeokchima') were transplanted to the close-type plant production system equipped with three types of combined LEDs with red (R, 655 nm), blue (B, 456 nm), green (G, 515 nm), and white (W, 456 nm + 558 nm) (R:B=8:2, R:W:B=8:1:1, R:G:B=8:1:1) and FL. The seedlings were grown under normal growth conditions ($20^{\circ}C$, $181{\pm}4{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, 12 h photoperiod) for four weeks. Lettuce plants grown under FL had significantly higher leaf shape index than those under all LED treatments. Although growth of shoots and roots was not show any significant difference among LED treatments, all of the LED treatments induced about 34% higher shoot fresh weight than that of the FL. On the other hands, the total power consumption of FL was 145 kW for 4 weeks, while the mean value of LED treatments was 54 kW, which was about 3 times lower value than that of the FL. The light use efficiency based on dry matter in LED treatments was about 34 mg/W and this was about 3.5 times higher energy saving value than the FL. In conclusion, this study showed that irradiation of optimal combined LEDs in closed-type plant production systems can improve the lettuce growth as well as maximize in light use efficiency through energy saving than the FL.

• Korean Journal of Environmental Agriculture
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• v.32 no.1
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• pp.42-47
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• 2013

BACKGROUND: As improved LEDs (Light Emitting Diode) industry and decreased the price of LEDs in Korea, some farmers try to using the RED LEDs in green house and open field to increase the production of crop under bad weather condition. The aim of this study is to find out the effect of RED and FAR-RED LEDs lighting on the fruit quality of twelve-year old 'Hongro'/M.26 apple during night after sunset. METHODS AND RESULTS: FAR-RED (730nm, 2 and 4 hour) and RED (620nm, 2 and 4 hour) with 20 LED/PCB were treated in orchard for 16 weeks from June 10 to October 10 in 2009 and 2010 with control as an comparison. In our experiments, leaf weight was significantly higher in RED LEDs than control, tended to be decreased as times of FAR-RED lighting increased. Fruit weight was increased more in RED LEDs than control in 2009 and 2010, but decreased in FAR-RED lighting compared to control in 2010. Firmness and Hunter's a value of fruit were increased in FAR-RED lighting with 2 and 4 h than control. Soluble solid contents were higher in 2 h RED and 2, 4 h FAR-RED LEDs compared to control in 2009, there was no significant difference in 2010. Acid contents were no difference among the treatments. CONCLUSION(S): In our results, we found that RED LEDs was more helpful to increase the fruit weight and FAR-RED LEDs promote to be higher hunter a value of fruit skin. So, we thought that it is necessary to more study if mixed of RED and FAR-RED lighting is more helpful to promote fruit quality of 'Hongro' apple than single lighting of RED or FAR-RED LEDs respectively.

• 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.32 no.3
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• pp.193-200
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• 2013

BACKGROUND: Plant factory system of an artificial light type using Light-Emitting Diodes (LEDs), fluorescent light, or metal halide lamp instead of sun light is an ultimated method for plant production without any pesticides regardless of seasonal changes. The plant factory is also completely isolated from outside environmental conditions such as a light, temperature, or humidity compared to conventional greenhouse. Light-environment control such as a quality or quantity in the plant factory system is essential for improving the growth and development of plant species. However, there was little report that the effects of various light qualities provided by LEDs on Ledebouriella seseloides growth under the plant factory system. METHODS AND RESULTS: Ledebouriella seseloides seedlings transplanted at urethane sponge were grown in the plant factory system of a horizontal type with LED artificial lights for 90 days. Yamazaki solution for hydroponic culture of the seedlings was regularly irrigated by the deep flow technique (DFT) system on the culture gutters. Electrical Conductivity (EC) and pH of the solution was recorded at 1.4 ds/m and 5.8 in average, respectively during the experimental period. Number of unfolded leaves, leaf length, shoot fresh and dry weight of the seedlings were three times measured in every 30 days after beginning of the experiment. Blue LEDs, red LEDs, and fluorescent lights inside the plant factory were used as light sources. Conventional fluorescent lamps were considered as a control. In all the treatment, light intensity was maintained at $100{\mu}mol/m^2/s$ on the culture bed. Fresh weight of the seedlings was 3.7 times greater in the treatment with the mixture radiation of fluorescent light and blue+red LEDs (1:3 in energy ratio; Treatment FLBR13) than in fluorescent light treatment (Treatment FL). In FLBR13 treatment, dry weight per seedling was two times greater than in FL or BR11 treatment of blue+red LEDs (1:3 in energy ratio; Treatment BR11) during the culture period. Increasing in number of unfolded leaves was also significantly affected by the FLBR13 treatment comparing with BR11 treatment. CONCLUSION(S): Hydroponic culture of Ledebouriella seseloides seedlings was successfully achieved in the plant factory system with mixture lights of blue, red LEDs and fluorescent lights. Shoot growth of the seedlings was significantly promoted by the FLBR13 with the mixture radiation of fluorescent light, blue, and red LEDs under 1:3 mixture ratio of blue and red LEDs during the experimental period compared to conventional light conditions.

• 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.

• Korean Journal of Environmental Agriculture
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• v.29 no.4
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• pp.374-380
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• 2010

This experiment was carried out to investigate the effect of light qualities and lighting types provided by LED Chamber System which designed by Rural Development Administration on growth and development of Chrysanthemum (Dendranthema grandiflorum L., cv. 'Cheonsu') plantlet cultured in vitro. The explants of single-node cuttings were exposed to monochromic or mixture radiation of blue, red, or green under continuous and intermittent lighting for 42 days. The intermittent lighting of 20 sec. on and off per minute significantly stimulated shoot elongation with lower number of internodes compared with continuous lighting treatments. However, continuous blue, red, or green light gave greater dry weight comparing the intermittent lighting, and the lowest weight was recorded at the continuous fluorescent lamp. Otherwise, the plantlet growth in dry weight or leaf area was inhibited by the green light controlled at 50 times intermittence but internode elongation was significantly increased. These results showed that the plantlets were successfully grown under the LED Chamber System controlled with different light qualities and lighting types. Quantitative growth of the plantlets was improved under the shorter photoperiod with a intermittent lighting cycle compared with continuous lighting using fluorescent lamps. It is concluded that the growth and development of in vitro plantlets such as single-node cuttings can be achieved by the controlling of light quality or lighting type during the photoperiod per day with a lower electric cost compared with conventional continuous lighting system.

• Horticultural Science & Technology
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• v.34 no.4
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• pp.596-606
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• 2016

The growth and contents of anthocyanins and ascorbic acid in lettuce(Lactuca sativa L., 'Jeokchima') as affected by supplemental UV-A LED irradiation under different light quality and photoperiod conditions were analyzed in this study. Five light qualities, namely B (blue LED), R (red LED), BUV (blue LED+UV-A LED), RUV (red LED+UV-A LED) and Control (white fluorescent lamps) with photoperiods of 12/12 hours (day/night), 16/8 hours, or 20/4 hours were provided to investigate the effects of light quality and photoperiod on the growth and accumulation of anthocyanins and ascorbic acid in lettuce leaves. As measured 28 days after transplanting, the number of leaves, leaf length, leaf width, leaf area, shoot fresh weight and dry weight of lettuce were significantly affected by light quality and photoperiod. The number of leaves, leaf length, leaf width, leaf area, shoot fresh weight and dry weight of lettuce grown under R treatment increased with increasing light period. By contrast, leaf development was inhibited, but chlorophyll content increased, under B treatment. Supplemental UV-A irradiation significantly decreased leaf length, leaf width, leaf area and shoot fresh weight. Anthocyanins in lettuce increased significantly with decreasing dark period under B treatment. A synergistic effect of supplemental UV-A LED irradiation on anthocyanins accumulation was found for lettuce leaves grown under R treatment but not B treatment. Ascorbic acid in lettuce was greatly affected by photoperiod. Ascorbic acid content at BUV and RUV treatments increased by 20-30% compared to without UV-A LED irradiation. From these results, it was concluded that growth and contents of anthocyanins and ascorbic acid in lettuce are significantly affected by supplemental UV-A LED irradiation. The results obtained in this study will be informative for efforts to improve the nutritional value of leafy vegetables grown in plant factories.

• Journal of Bio-Environment Control
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• v.23 no.4
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• pp.356-363
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• 2014

This work was conducted to investigate the field growth and yield of the sweetpotato (Ipomoea batatas) slips grown under different light emitting diodes (LEDs). Sweet potato cuttings of 3 cultivars ('Matnami', 'Shinhwangmi', and 'Yeonhwangmi') were cultivated under fluorescent lamp (FL) and several LEDs (PPF $150{\pm}5{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ at 20cm distance) in deep flow culture system for 20 days. The plants were acclimatized under sunlight for 10 days, and then cuttings (30cm length) were planted with $75{\times}25cm$ planting density on June 10th, covered with black vinyl film during growth period. Length and diameter of vine, number of root were excellent in the red plus blue (7:3) LED than the other treatments. At 30 days after planting, the survival rate in red plus blue (7:3) LED was significantly higher than that in FL and red LED, and it was not different among cultivars. Vine length, vine diameter, and number of node were not significant among LED light qualities and cultivars. After 120 days in the field cultivation, vine length, vine diameter, number of node, number of branch, and fresh weight of shoot were not significant among LED light qualities, but those except the number of branch showed significant differences among cultivars. Yield characteristics among LED light colors were not significant, but weight of storage root per plant, mean weight of storage root, and yield showed significant differences among cultivars. The yield per 10a in 'Matnami', and 'Yeonhwangmi' was significantly higher than that in 'Shinhwangmi'.