• Journal of Korean Society of Forest Science
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• v.53 no.1
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• pp.37-43
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• 1981

This study was aimed at expanding the tea plant culture in Korea to further north, and the leaf-form and the cold resistance of the tea plants selected form 7 districts(around Korea) were investigated. 1. The length of tea leaf is 5.1cm to 8.4cm, the width of the leaf is 2.3cm to 3.6cm, but the area of tea leaf in Mt. Mudung is $26.88cm^2$ and that is the widest of all. 2. The tooth number of the tea leaf in 43 to 73 but the number of Mt. Borim is remarkably number of all. The tooth number is increased or decreased in proportion to the leaf width and to the leaf length. 3. The lateral vein number is generally 13 to 19. The vein number of Mt. Borim is especially number of all. That is also increased or decreased in proportion to the leaf width and to the leaf length. 4. In general, the number of leaf formation index is 2 to 3, and ablong. 5. In general, those which come upper lands are remarkably small in length and width of the tea leaf and those which come from level lands are large. 6. All kinds of tea plant which is growing in Korea, area, are the same as those imported from China : Thea sinensis Linne var. Bohea. 7. I supposed that the external form of tea plant has a little changed by geography or climate for many a long day, since the tea plant had been transplanted in Mt. Samsin. 8. In the treatment of low temperature and duration of vernalization of their plants, those selected from Mt. Mudung and Mt. Hwaun were the coldest resistance, those from Mt. Samsin and Mt. Borim were medium and those from Mt. Joge and Nursery were cold sensitive. 9. The critical temperature of the tea plant from Mt. Mudung, Mt, Hwaum, Mt, Samsin and Mt. Borim was about $-10^{\circ}C$, and that from Mt. Joga and Nursery was about $-5^{\circ}C$. The critical temperature of frost injury of all tea plants in this experiments was $-15^{\circ}C$. 10. In spite of increasing the vernalization time, the critical temperature was not effected, but the treatments over critical temperature were increased their frost injuries. Based on these results, the coldest resistance, Mt. Mudung tea plant, was considered expanding their culture to further north improvement yields of the tea plants in Korea.

• Korean Journal of Plant Resources
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• v.29 no.4
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• pp.511-518
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• 2016

The subject of this experiment is to supply basic data to inhibit non-productive tillers which are uneconomical for mechanical harvesting and to evaluate optimum planting density and sowing date in central district. Total number of tillers and effective first and second of tillers according to different planting density was higher in 80 ㎝ ridge than 60 ㎝ ridge in proso millet. The wider between plant distance on the ridge, the more increased total number of tillers and effective first and second of tillers. The highest effective tillers (91.7 %) in the first tillers was obtained from the second sowing date (23 May) among different sowing date and next is in the order of 3^rd(13 June, 89.8%) > 1^st(2 May, 85.6%) > 4^th(4 July, 85.2%). The percentage of effective tillers in the second tillers was decreased in the order of 2 May (53.7%), 23 May (40.7%), 13 June (22.2%), 4 July (0%) as the sowing date was delayed. There was no significant difference in days to heading and days to ripening according to different planting density. Although culm length was increased as planting density was increased, whereas number of tillers, stem diameter, ear length, grains per ear and 1000 grain weight was decreased. In the growth and yield characteristics of proso millet according to different sowing date, days to heading and days to ripening, culm length, stem diameter, ear length, grains per ear and yield per 10a were decreased. After the sowing date of 13 June, the reduction of growth and yield characteristics were higher because of excess-moisture injury.

• Horticultural Science & Technology
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• v.34 no.4
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• pp.607-615
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• 2016

This research was conducted to investigate the influence of different kinds of acids added to irrigation water containing high levels of bicarbonate on the growth and daughter plant production during the propagation of 'Seolhyang' strawberry. Fertigation solution was prepared with equal concentrations of essential nutrients as found in Hoagland solution, plus $240mg{\cdot}L^{-1}\;HCO_3{^-}$. The concentrations of $HCO_3{^-}$ in the treatment solution were decreased to $60mg{\cdot}L^{-1}$ by the addition of $HNO_3$, $H_3PO_4$, $H_2SO_4$, $HNO_3+H_3PO_4$, or salicylic acid. The mother plants transplanted to raised beds were treated with a specific treatment solution for 126 days and growth and daughter plant productions were monitored. The fresh weight of mother plants in the -control treatment ($240mg{\cdot}L^{-1}\;HCO_3{^-}$) was significantly lower than those in acid containing treatments. The number of daughter plants produced per mother plant was 13 in the -control treatment, but 19.4, 20.1, 18.6, 22.4, and 18.9 in the treatments of $HNO_3$, $H_3PO_4$, $H_2SO_4$, $HNO_3+H_3PO_4$ and salicylic acid, respectively. The substrate pHs after 126 days of treatment were 8.2 and 7.3 in the -control and salicylic acid treatments, respectively, but 5.5, 5.4, 5.3, and 5.5 in the treatments of $HNO_3$, $H_3PO_4$, $H_2SO_4$, and $HNO_3+H_3PO_4$ treatments, respectively. The tissue Ca and Mg contents of mother plants were significantly higher in +control ($90mg{\cdot}L^{-1}\;HCO_3{^-}$) and various acid blending treatments compared to the -control treatment. By contrast, Ca and Mg contents were not significantly different among treatments with acids. The Fe, Mn, Zn, and Cu contents in plant tissue of -control were also significantly lower than those in all other treatments.

• Korean Journal Plant Pathology
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• v.3 no.3
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• pp.180-186
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• 1987

Cell suspensions of two isolates of Pseudomonas syringae. PS8401 from sweet persimon and PS8402 from tea plant, were active in ice nucleation at -2.5 and $-3.8^{\circ}C$, respectively. Ice nucleation at those temperature was, using micropipette method, detected in suspensions ($10^8$ olony forming unit/ml of distilled water) of cells that had been grown on nutrient agar supplemented with $2.5\%$ glycerol. Using the same method, on the other hand, the freezing temperature of distilled water only was approx. $-21.8^{\circ}C$, and those of various plant saps including corn were lower than $-11.6^{\circ}C$. Corn seedlings sprayed with cell suspensions $(10^8\;cfu/ml)$ of nutrient broth) of PS8401 began to be damaged at $-2^{\circ}C$ and were almost completely damaged at $-4^{\circ}C$, whereas seedlings sprayed with nutrient broth only were not injured until the temperature down to $-9^{\circ}C$. Amounts of frost damage measured 48 hr after application of PS8401 suspensions increased as applied bacterial cell densities were increased. Ice-nucleation activity of the cell suspensions in vitro increased with increasing the number of cells in suspension. The activity also affected by growth-medium composition or growth-temperature. Ice nucleation thus occured at -4.0, -4.4 and $-7.2^{\circ}C$ in suspensions $(10^2\;cfu/ml)$ of PS8401 that had been grown at$25\%$ nutrient agar with $2.5\%$ glycerol, nutrient agar with $2.5\%$ glucose and nutrient agar only, respectively, and occured at -4.0 and $-7.6^{\circ}C$ in suspensions $(10^2\;cfu/ml)$ of PS8401 hat had been grown on nutrient agar with $2.5\%$ glycerol at $15\~25^{\circ}C$ and $30^{\circ}C$, respectively.

• Korean Journal of Environmental Agriculture
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• v.2 no.2
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• pp.98-102
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• 1983

The hydrogen fluoride gas generated from making the cement hardener injured the plants growing at the neighbour field. This investigation was conducted on sample analysis of hydrogen fluoride gas damage plants which included the ratios of destroyed leaves, damage symptoms, and nutrient elements in paddy rice and weeds. The results obtained were as follows; 1) The ratio of destroyed leaves at near HF source was very high reaching about 95% at 100m, 65% at 500m, 5% at 2㎞, respectively. 2) The necrosis was the characteristic symptom of fluoride injury on rice plant and occurred predominantly at the tip and margins of damage leaf. It developed along the tip and margins of leaves with a dull, gray-green, water soaked discoloration. 3) The fluorine content of tip and margins of damaged rice leaves were 1,600 ppm, 3 to 20 times higher than that of center part and it ranged from 130 to 242.5 ppm in weed leaves, but from 10 to 15 ppm in normal weed leaves. 4) The contents of calcium, potassium, silicon, iron and manganese were higher in tip and margins than in the center of rice damage leaves. 5) The Cocculus trilolous. D.C was the most resistant plant to HF gas than any other plant growing in this site, while wild berry and aralia tree belong to most sensitive plant group.

• Korean Journal of Environmental Agriculture
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• v.20 no.2
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• pp.127-132
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• 2001

This study was conducted for ten years to evaluate the effective soil management for preventing the infection of root-knot nematode in the field of continuous cultivation with oriental melon under plastic house in Songju area of kyongbuk province. The content of available phosphate, total nitrogen, organic matter, CEC, and exchangeable base in the soil increased with the increase of continuous cultivation year. Especially salt content in the soil increased form 1.2 to 4.55 mS/cm and the yield of oriental melon dramatically decreased with the continuous cultivation year. The number of root-knot nematode was 91 per $300\;cm^3$ of soil in the field of continuous cultivation for 3 years and showed slight damage on the oriental melon, but it was 518 in the field of $4{\sim}6$ years continuous cultivation and showed that 50% of plants died in August, and the yield of late season was less than 50% compared to normal plant. For the seasonal changes in infection rate of root-knot nematode on oriental melon plant, 15% of the normal plant was infected by nematode in February and increased gradually by $10{\sim}20%$ per month, 60% of plants was infected in July. The density of root-knot nematode nymph was 167 in February and increased to 1,625 in August. The infection rate of nematode was 35%, and the number of nematode was about 54 in nursery soil originated from paddy soil, upland soil, and river sand. There were no relationship between the number of nematode and available phosphate or exchangeable base in the soil of plastichouse where oriental melon plants were grown.

• Korean Journal of Environmental Agriculture
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• v.13 no.1
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• pp.31-38
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• 1994

This study was carried out to investigate the possibility of potential injury to crops which were exposed to precipitation. The rainwater were collected from May to September in 1992 and analyzed its chemical composition. The amounts of chlorophyll and cations in plant were measured, and the morphological structure of epidermis was also investigated by SEM. The results are summarized as follows: 1. The pH of precipitation in Suwon was relatively high even with high level of $SO_4^{2-}$ and monthly pH at May, June, July, August, and September were 4.65, 5.47, 5.32, 5.44 and 4.80, respectively. 2. The amount of ions in rainwater was in the order of $NH_4^+$, $Ca^{2+}$, $Mg^{2+}$ and $H^+$ for cations, and $SO_4^{2-}$, $NO_3^-$ and $Cl^-$ for anions. 3. pH of rain in less than 5mm of precipitation was higher than that in greater than 5mm of precipitation. 4. The amount of chlorophyll was higher in the plant exposed to rain than that in plant intercepted rain during the early portion of growing season, but at the later period, the trend was shown to be reversed. 5. When the sesame plants were exposed to rain at harvesting stage, they contained less amount of CaO, MgO and $Na_2O$ than those with the interception of rain. 6. Scanning electron microphotographs revealed the shringkage in glandular trichomes in the epidermis of sesame leaves when they were exposed to rain.

• Journal of Life Science
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• v.21 no.9
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• pp.1214-1218
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• 2011

We investigated the fruits of Rubus crataegifolius Bge, a plant which has been traditionally used in Korea in phytotherapy, to describe antioxidant materials from plant sources. R. crataegifolius fruits were extracted with methanol and further fractionated into n-hexane, diethyl ether, and ethyl acetate. The antioxidant activity of each fraction and the residue was assessed using a 1,1-diphenyl-2-picrylhydrazyl (DPPH), $H_2O_2$ radical scavenging method, and their cytotoxicity on human primary kerationcyte (HK) was determined by an MTS assay. The R. crataegifolius fruit methanol extract showed strong antioxidant activity (75.04%, 50%) compared with vitamin C (79.9%, 54.1%) by the DPPH, and $H_2O_2$ method, respectively. The measured activity from the subsequent extracts of the methanol extract were 20.3% for n-hexane fraction (HF), 68.8% for diethyl ether fraction (DF), 67.1% for ethyl acetate fraction (EF), and 67.1% for the residue fraction (RE) by DPPH and 2.2% for HF, 1.6% for DF, 10% for EF, and 50% for the RE by $H_2O_2$ assay. An oxidative stress model of HK was established under a suitable concentration (1 mM). The cell viability of the RE treated group increased and the percentage of apoptotic cells decreased at concentrations of 0.005-0.02% RE compared with the $H_2O_2$ treated group. Fruit extracts of the medicinal plant R. crataegifolius showed potent antioxidant activity and the ability to relieve cell damage from $H_2O_2$ induced injury to HK.

• Research in Plant Disease
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• v.21 no.2
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• pp.58-66
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• 2015

This study was conducted to evaluate control efficacy of a fermented food 'Cheonggukjang' against cucumber powdery mildew caused by Sphaerotheca fuliginea in greenhouse. Sterilized Daepung beans were inoculated with the rice straw as natural inoculum and then incubated for 72 hrs at $42^{\circ}C$ in the household cheonggkjang maker. After 72 hrs of cheonggukjang fermentation, white zymogens were grown on the surface of a sterile Daepung beans. The pH of the 72 hrs fermented soybean was not significantly changed and electrical conductivity was found to increase by about 2 times than before fermentation. The population density of soybean zymogen showed a peak of growth at 60 hrs after fermentation and the concentration of zymogen was $8.2{\times}10^7cfu/ml$. Soybean zymogen form of the colony was divided into three kinds of bacteria and a white and a large colony (WL) was predominant bacteria among those up to 60 hrs of fermentation. To control the cucumber powdery mildew, diluted solutions of cheonggukjang was applied from 6.0% to 30.0% on cucumber leaves and they showed injury symptoms on cucumber leaves in more than 15% of them. However, more than 6.0% diluted cheonggukjang solutions showed more than 77.8% control effect of cucumber powdery mildew at 15 days after treatment. The fermented bacteria of Chenggukjang were well established in the cucumber leaf area at 15 days after treatment. The antifungal activity of 10% diluted cheonggukjang solutions was excellent for four species of plant fungal pathogens, Colletotrichum gloeosporioides, Sclerotinia cepivorum, Rhizoctonia sloani and Phytophthora capsici in the dual culture test. Results indicated that foliar application of Cheonggukjang solution could be used for the control of powdery mildews occurring on organically cultivated cucumber.

• Korean journal of applied entomology
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• v.46 no.1 s.145
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• pp.63-69
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• 2007

This study was conducted to examine the problems that would arise in our cropping systems when introducing Gain Threshold (GT) which is an important element in determining Economic Injury Level (EIL). Cain Threshold (GT) can be defined as the amount of damage (=yield loss) to justify management, and calculated by dividing the management costs by the market crop price. GTs for some pests in rice, soybean, and greenhouse vegetable crops cultivation were estimated and also compared with those in foreign countries. GTs and percentage of yield loss equivalent to them were estimated to be 4.6-6.1kg/10a/season and 1.0-1.3% for brown planthopper, white-backed planthopper, rice water weevil, and sheath blight, whereas for rice blast in rice cultivation were 12.7kg/10a/season and 2.7%. In soybean cultivation, the values for bean bug were 6.2 kg/10a/season and 3.6%. GTs and percentage of yield loss estimated for melon thrips, whitefly, and downy mildew in cucumber cultivation were 10.0-12.6kg/10a/week, 1.4-1.7%, and the values for two spotted mite and gray mildew in strawberry cultivation were 3.1-3.5kg/10a/week, 1.3-1.5%, and the values for American leaf minor, whitefly, and gray mold in tomato were 8.4-9.7kg/10a/week, 1.7-1.9%. Overall GTs in our cropping systems were so low compared to those in foreign countries, which meant that the low GTs might yield the low EILs. Therefore, we could suggest that prior to direct introduction of GTs calculated from current cultivation systems in developing EILs it is necessary to seriously consider reasonable values of GTs or the yield loss equivalents to them.