• Journal of Bio-Environment Control
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• v.32 no.3
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• pp.217-225
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• 2023

This experiment was conducted to investigate the effects of microwave irradiation on the growth and secondary metabolite contents of lettuce seedlings. Seedlings at three weeks after sowing were treated by a microwave oven for 0, 4, 8, and 12 seconds with 200 W. After cultivation in a close plant production system for 4 weeks, plant growth measurements and secondary metabolite analysis were performed. The results showed that the fresh and dry weights of the shoot and root, leaf area, leaf length, and the number of leaves were decreased as increasing the microwave treatment times. Chlorophyll a and b, total carotenoids were increased and total phenolics were decreased at the 12-second treatment compared to the 4-second treatment. Total flavonoid contents were decreased at the 8-second treatment compared to the control. These results suggest that the changes in the levels of secondary metabolites were caused by oxidative stress. Although there was no significant difference in secondary metabolite contents excluding total flavonoid contents on the microwave treatments compared to the control, the significant difference suggests that the microwave treatment of 200 W and 2.45 GHz may alter secondary metabolite contents of lettuce after 4 weeks.

• Journal of Bio-Environment Control
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• v.26 no.4
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• pp.418-423
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• 2017

In hydroponics, the nutrient solution is supplied considering the water and nutrient uptake characteristics of crops. However, as the ionic uptake characteristics are changed as a result of the weather conditions or the growth response of the crops, the root zone can not be maintained in optimal condition. In addition, the coir substrate has been used mainly for the tomato cultivation in place of the inorganic substrate, there are few studies on long-term cultivation using coir substrate. Therefore, this study was conducted to investigate the effect of EC level of irrigation solution on tomato growth and inorganic ions of root zone in soilless culture using coir. Coir substrate mixed with 5 : 5 chip and dust was used. EC level of irrigation solution was 1.0, 1.5, 2.0, and $3.0dS{\cdot}m^{-1}$. At the initial stage, $NO_3-N$, P, Ca and Mg in the drainage were lower than the irrigation level at 1.0 and $1.5dS{\cdot}m^{-1}$. However, EC $2.0dS{\cdot}m^{-1}$ or higher, all the ions except P were highly concentrated in the drainage. The average fruit weight was not significantly different between 1.0 and $1.5dS{\cdot}m^{-1}$ until 3th cluster, but from the next cluster, the higher the EC level, the smaller the weight. The number of fruit and yield to 6th cluster was the highest at $1.5dS{\cdot}m^{-1}$. From the next cluster, The yield was decreased with the higher EC level. At the early stage of growth, BER occurred only in EC $3.0dS{\cdot}m^{-1}$, but increased in all treatments with increasing irradiation. The incidence rate of EC $3.0dS{\cdot}m^{-1}$ was higher than that of the lower EC level treatment.

• Journal of Bio-Environment Control
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• v.26 no.2
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• pp.123-132
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• 2017

This study was aimed to investigate the effect of 1)irradiation with several different ratios using red, green, and blue LEDs and 2)various pulsed light irradiation with 50% duty ratio using red and blue LEDs on the growth and morphogenesis of three lettuce cultivars (Lactuca sativar L. cv. 'Jukchukmeon', 'Lolo Rosa', and 'Grand Rapid') in hydroponics culture system for 4 weeks after transplanting. Seeds were sown in rock-wool plug trays and they were placed in a culture room which was controlled at $23{\pm}1^{\circ}C/18{\pm}1^{\circ}C$ temperature and 50-60/70-85% for day and night, respectively, during cultivation period. Irradiated RGB ratios with LEDs were 6:3:1, 5:2.5:2.5, 3:3:4, 2:2:6, and 1:1:8 with $110{\pm}3{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ PPFD on the surface of cultivation bed. The frequencies of pulsed lighting was 50, 100, 500, 1,000, 5,000, 10,000, 25,000Hz (20, 10, 0.1, 0.04 ms) with red and blue LEDs and 50% duty ratio. At the RGB ratio of 6:3:1, the average fresh weight of 'Jukchukmeon' was significantly higher than that of other RGB treatments, but no significant difference compared to the fluorescent treatment. The average fresh weight at 1:1:8 RGB ratio in 'Lolo Rosa' was significantly lower than that of other RGB treatments. Leaf number and fresh weight of 'Grand Rapid' were significantly lower in the control and 1:1:8 RGB treatments, compared to the other RGB treatments. As the ratio of blue light increased, leaf length decreased and leaf shape became round in three lettuces. Although there is little change in growth, it could not be found any tendency to affect the growth and morphogenesis of three lettuces caused by increasing or decreasing frequency of pulsed lighting with 50% duty ratio at the $72{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ PPFD.

• Journal of Bio-Environment Control
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• v.30 no.3
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• pp.188-195
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• 2021

This study was conducted to investigate the growth and quality characteristics of melon (Cucumis melo L.) cultivars and the irrigation requirements for cultivars. In our previous study in 2019, twelve melon cultivars including 'Dalgona' were examined for their cultivar characteristics under the same irrigation condition for all cultivars, and sorted into several groups based on different growth condition; for the internode length (from 0 to 20th node), leaf area, and fruit weight, 'Kingstar' belonged to the largest group, 'Worldstar' the middle group, and 'Dalgona' the smallest group. After analyzing the results of the previous experiment, 'Dalgona', 'Worldstar', 'Kingstar', and 'Rubyball' were selected as test cultivars for the growth group in 2020, and irrigated according to different irrigation levels for each cultivar. The control of the irrigation volume for each melon cultivar by monitoring the drainage rate during the cultivation periods showed that all four cultivars required a similar amount of irrigation in the 'early growth' stage where crops grew at about the same rate. From 'flowering time', however, the change in irrigation requirements showed a similar tendency for 'Worldstar' and 'Kingstar' and for 'Rubyball' and 'Dalgona' respectively. A sudden change in each irrigation volume was observed from the fruit set; 'Dalgona' began first to decline and 'Rubyball' was second, followed by 'Worldstar' and 'Kingstar'. In conclusion, the irrigation volume was the largest in 'Kingstar', followed by 'Worldstar', 'Rubyball', and 'Dalgona' in the same order as the growing amount of plant length, leaf area, and fruit weight. Therefore, it is necessary to control exactly the irrigation volume by reflecting the unique growth characteristics of each cultivar for the production of high-quality fruit in melon hydroponics, and especially to use great care when different cultivars are cultivated together.

• Journal of Bio-Environment Control
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• v.32 no.4
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• pp.449-455
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• 2023

In this study, the effect of crown heating on the cultivation environment, budding, flowering and yields of strawberry was analyzed. In December, January, and February, when the outside temperature was low, the average strawberry crown temperature at daytime in the test zone was 1.3℃ higher than that in the control zone, and the average strawberry crown temperature at nighttime in the test zone was 2.7℃ higher than that in the control zone. The average bed temperature at daytime in test zone was 1.7℃ higher than that in the control zone, and the average bed temperature at nighttime in test zone was 2.4℃ higher than that in the control zone. As a result of performing correlation analysis and regression analysis on strawberry crown temperature and budding period, the correlation coefficient was -0.86, which tended to be shorter as the crown temperature was higher, and the determination coefficient was 0.74. The total yields of strawberry during test period were 392.6 g/plant for test greenhouse and 346.0 g/plant for control greenhouse respectively. As for the quality of strawberries, the ratio of 2L (very large) grades and L (large) grades was 62.4% in the test greenhouse and 58.5% in the control greenhouse, indicating that the proportion of high quality strawberries was higher in the test greenhouse.

• Journal of Bio-Environment Control
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• v.22 no.4
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• pp.349-354
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• 2013

This study examined a technique for cooling root zone aimed at lowering substrate temperature for sweet pepper (Capsicum annum L. 'Orange glory') cultivation in coir substrate hydroponics during hot season, from the $16^{th}$ of July to $15^{th}$ of October in 2012. The root zone cooling technique was applied by using an air duct (${\varnothing}12$ cm, hole size 0.1 mm) to blow cool air between two slabs during night (5p.m. to 3a.m.). Between the $23^{rd}$ of July and $31^{st}$ of August (hot temperature period), average daily substrate temperature was $24.7^{\circ}C$ under the root zone cooling, whereas it was $28.2^{\circ}C$ under condition of no cooling (control). In sunny day (600~700 W $m^{-2}{\cdot}s^{-1}$), average substrate temperatures during the day (6a.m. to 8p.m.) and night (8p.m. to 6a.m.) were lower about $1.7^{\circ}C$ and $3.3^{\circ}C$, respectively, under the cooling treatment, compared to that of control. The degree of temperature reduction in the substrate was averagely $0.5^{\circ}C$ per hour under the cooling treatment during 6p.m. to 8p.m.; however, there was no decrease in the temperature under the control. The temperature difference between the cooling and control treatments was $1.3^{\circ}C$ and $0.6^{\circ}C$ in the upper and lower part of the slab, respectively. During the hot temperature period, about 32.5% reduction in the substrate temperature was observed under the cooling treatment, compared to the control. Photosynthesis, transpiration rate, and leaf water potential of plants grown under the cooling treatment were significantly higher than those under the control. The first flowering date in the cooling was faster about 4 days than in the control. Also, the number of fruits was significantly higher than that in the control. No differences in plant height, stem thickness, number of internode, and leaf width were found between the plants grown under the cooling and control, except for the leaf length with a shorter length under the cooling treatment. However, root zone cooling influenced negligibly on eliminating delay in fruiting caused by excessively higher air temperature (> $28^{\circ}C$), although the substrate temperature was reduced by $3^{\circ}C$ to $5.6^{\circ}C$. These results suggest that the technique of lowering substrate temperature by using air-duct blow needs to be incorporated into the lowering growing temperature system for growth and fruit set of health paprika.

• Journal of Bio-Environment Control
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• v.18 no.4
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• pp.363-369
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• 2009

This experiment was conducted to find out the effect of nutrient solution composition on the growth of cucumber plants and the changes in macro-elements in nutrient solutions in recirculating hydroponic systems. Cucumber plants (Cucumis sativus L. cv. Joeun Baegdadagi) were grown in closed perlite cultivation systems supplied with different nutrient solutions developed by NHRS (National Horticultural Research Station in Japan), Yamasaki, PBG (Proefstation voor Bloemisterij en Glasgroente), and NIHHS (National Institute of Horticultural and Herbal Science in Korea). The concentrations of $NO_{3^-}N$, $Ca^{2+}$, $Mg^{2+}$, and $SO_{4^-}S$ in the recycled nutrient solutions increased but that of $NH_{4^-}N$ decreased gradually in all the treatments. The $PO_{4^-}P$ and $K^+$ concentrations were continuously reduced from the beginning of the harvest to the harvest peak period. There were no significant differences in the concentrations of $NO_{3^-}N$, $NH_{4^-}N$, and $Ca^{2+}$ in the recirculated nutrient solutions among four treatments, while the concentrations of $PO_{4^-}P$ and $K^+$ were lowest and those of $Mg^{2+}$ and $SO_{4^-}S$ were highest in the treatment of Yamasaki's nutrient solution. All growth-related parameters of cucumber plants except for leaf number were not significantly affected by the nutrient solution compositions. Due to its low concentrations of $PO_{4^-}P$ and $K^+$ in the recycled nutrient solution, however, the number and yield of cucumber fruits were lowest in the treatment of Yamasaki's nutrient solution.

• Horticultural Science & Technology
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• v.34 no.2
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• pp.228-235
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• 2016

This study was conducted to determine the yield of cherry tomato (Solanum lycopersicum Mill.) grown at three planting times during the uncultivated period of strawberry. Cherry tomato was planted under condition filled with strawberry dedicated culture medium on a two-story bed with April 20, April 30, and May 10 at 2015. Fruit harvest was completed on July 31. The supply concentration of nutrient solution at the time of transplanting was started as EC $1.2dS{\cdot}m^{-1}$ and it was gradually increased to EC $2.5dS{\cdot}m^{-1}$ after blooming of the first flower cluster. Netherlands PBG solution was supplied for one minute six times per day. The heights of cherry tomato plants planted at earlier were significantly greater than those of tomato plants planted later. The heights of cherry tomato plants grown at the bottom of the bed were greater than those grown in the upper bed. The yield of cherry tomatoes planted on April 20 at the bottom of the bed was greatest with an average of 2,954 g of tomatoes per plant. There were no significant differences in the average weight and sugar content of fruit according to planting times and bed position. The yield of cherry tomato plants planted on April 20 was 18% and 34% higher than that of plants planted on April 30 and May 10. We confirmed to increase the yield of the cherry tomato when early plants planted on two-story bed. These results indicate that farmers can choose the best period of producing cherry tomato during the un-cultivated period of strawberry under two-story bed conditions.

• Journal of Bio-Environment Control
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• v.23 no.2
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• pp.144-147
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• 2014

It was intended to closely examine an effect that a change in the concentration of culture medium had on the potato(Solanum tuberosum L.) plantlet growth in the microponic system so as to mass-produce the virus-free plant of new variety 'Saebong' for potato processing. The adjusted concentration of potato culture medium was 0.2, 0.6, 1.0, 1.4, 1.8, and $14.0dS{\cdot}m^{-1}$. And potato seedling was cut into pieces of 1.5 cm in length, which included 2 growth points and leaves. And each was explanted in glass vial of 50 mL. And experiments were carried out twice for 18 days or 21days. Culture medium of 2ml was put in the container respectively. And 1 mL was added after 10 days. And in terms of cultivation environment, the experiment was carried out at the day length of 16 hours at the temperature of $23{\pm}1^{\circ}C$ under the white LED light of $40{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$. The concentration of culture medium in the experiment I was EC 0.2, 1.0, $14dS{\cdot}m^{-1}$ and was adjusted to 0.6, 1.0, 1.4, $1.8dS{\cdot}m^{-1}$ in the experiment II. The results showed that the survival rate of plantlet was 90% at $0.2dS^2m^{-1}$, 100% at $0.6dS^2m^{-1}$, 100% at $1.0dS^2m^{-1}$. 0% at $1.4dS{\cdot}m^{-1}$, 0% at $1.8dS{\cdot}m^{-1}$. and 0% at $14.0dS{\cdot}m^{-1}$ after 7 days. With regard to the explanted potato seedling, in case of the treatment where the electrical conductivity of culture medium was adjusted to $1.0dS{\cdot}m^{-1}$, root developed 2 days after transplantation. And the plantlet vigorously grew into strong plant that had 7 leaves, length of 5cm, and fresh weight of 0.5 g after 18 days. In case of the treatment where the concentration of culture medium was adjusted to $0.6dS{\cdot}m^{-1}$, the root plantlets developed 4 days after transplantation. And those grew into plant that had 7 leaves and fresh weight of 0.2 g after 21 days. Therefore, we found that it is effective to control potato culture medium by adjusting its electrical conductivity to $0.6{\sim}1.0dS{\cdot}m^{-1}$ for the mass production of virus-free potato seedling in the microponic system.

• Journal of Bio-Environment Control
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• v.26 no.4
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• pp.340-345
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• 2017

Carrot leaves have many nutrients as well as roots, which will increase the demand for carrot leaves in the future. This study was carried out by dividing into two stages: high temperature and low temperature periods, in order to investigate the possibility of cultivation of carrot leaves and the composition and EC of the nutrient solution for growth and quality of carrot leaves. Composition of nutrient solution($NO_3-N:16.0$, $NH_4-N:1.0$, P: 1.0, K: 11.0, Ca: 2.0, Mg: 1.0, $SO_4-S:1.0mM{\cdot}L^{-1}$) developed by analysis of plant. In the high temperature range (From June $29^{th}$ to Sep. $8^{th}$, 2016), the concentration of the developed nutrient solution (JNU) were 1.0, 2.0, 3.0, and $4.0dS{\cdot}m^{-1}$ and the concentration of nutrient solution of Japanese Horticultural Station(JHS) $2.0dS{\cdot}m^{-1}$ was used for comparison. In the low temperature range (From Dec. $31^{st}$, 2015 to Feb. $29^{th}$, 2016), the concentration of the developed nutrient solution 1.0, 2.0, and $3.0dS{\cdot}m^{-1}$ were used. Growth was investigated in root fresh and dry weights, shoot fresh and dry weights, leaf number, and leaf area of carrot. In the high temperature range, the leaf area and shoot fresh and dry weights were good at 1.0 and $2.0dS{\cdot}m^{-1}$. The sugar content of the root was the highest at the EC $2.0dS{\cdot}m^{-1}$, and the chlorophyll content was the highest at the EC $4.0dS{\cdot}m^{-1}$. In the low temperature range, The shoot fresh and dry weights were the highest at EC 1.0 and $2.0dS{\cdot}m^{-1}$. There was no significant difference in sugar content and chlorophyll content. As a result, from the viewpoint of growth and quality of carrot, it is good to cultivate EC 1.0 and $2.0dS{\cdot}m^{-1}$ in high temperature period and low temperature period, but EC $1.0dS{\cdot}m^{-1}$ is economical perspective such as fertilizer input.