• KOREAN JOURNAL OF CROP SCIENCE
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• v.64 no.4
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• pp.344-352
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• 2019

Drought stress caused by global climate change is a serious problem for rice cultivation. Increasingly frequent abnormal weather occurrences could include severe drought, which could cause water stress to rice during the seedling stage. This experiment was conducted to clarify the effects of drought during the seedling period on yield and quality of rice. Drought conditions were created in a rain shelter house facility. The drought treatment was conducted at 3, 10, and 20 days after transplanting. Soil water content was measured by a soil moisture sensor during the whole growth stage. In this study, we have chosen 3 rice cultivars which are widely cultivated in Korea: 'Haedamssal' (Early maturing), 'Samkwang' (Medium maturing), and 'Saenuri' (Mid-late maturing). The decrease in yield due to drought treatment was most severe 3 days after transplanting because of the decrease in the number of effective tillers. The decrease in grain quality due to drought treatment was also most severe 3 days after transplanting because of the increased protein content and hardness of the grains. The cultivar 'Haedamssal' was the most severely damaged by water stress, resulting in about a 30% yield loss. Drought conditions diminished the early vigorous growth period and days to heading in early-maturing cultivars. The results show that drought stress affects yield components immediately after transplanting, which is a decisive factor in reducing yield and grain quality. This study can be used as basic data to calculate damage compensation for drought damage on actual rice farms.

• Korean Journal of Environmental Agriculture
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• v.24 no.2
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• pp.159-163
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• 2005

This study was conducted to investigate the effect of simulated acid rain (SAR) on growth and antioxidant system in french marigold (Tagetes patula L.). Plants were subjected to four levels of SAR (pH 5.6, 4.0, 3.0, 2.0) in the growth chambers for 2 weeks. SAR decreased both plant height and plant dry weight of french marigold. As the pH levels decreased from 5.6 to 2.0, the content of MDA highly increased linearly. The ratios of dehydroascorbate/ascorbate and oxidized glutathione/reduced glutathione were significantly increased with decreasing pH levels. The enzyme (superoxide dismutase, ascorbate peroxidase etc.) activities of the plant affected by SAR were increased as the pH decreased. Based on the results, SAR caused oxidative stress in french marigold and resulted in significant reduction in plant growth. Biochemical protection responses might be activated to prevent the plant from damaging effects of oxidative stress generated in SAR.

• Research in Plant Disease
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• v.9 no.3
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• pp.166-169
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• 2003

Occurrence of cercospora leaf spot by Cercospora capsici is assamed to remarkbly cause the yield reduction through the leaf spot, yellowing of leaves and early defoliation in pepper cultivation. To develop resistant cultivar, optimal screening conditions of pepper against cercospora leaf spot were studied. Optimal screening conditions were 3.4 ${\times}$ $10^5$ conidia/ml conidial suspension were sprayed on to the leaves of 30~40 days old pepper seedlings, incubated at 15~$20^{\circ}C$/20~$25^{\circ}C$(day/night) and examined 20 days after inoculation.

• Korean Journal of Environmental Agriculture
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• v.15 no.2
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• pp.207-216
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• 1996

Simulated acid rain(SAR) treatment caused a lethal effect on the newly germinated seedlings of Capsicum annum cv. Komyung even though the germination rate of the seeds was stimulated by the treatment of SAR. Young germinated seedlings were much more sensitive to SAR than the already-grown seedlings. The typical symptom caused by SAR was white spot or lesion on the leaf and appeared readily and severely at the low pH of SAR. Generally, Phytophthora rot was severer in SAR treatments than in control. However, the disease was less severe in lower pH of the SAR treatment than in higher pH. Pathogen inoculation following the SAR treatment increased the disease. The severest Phytophthora rot was observed in the SAR treatment of pH 4.0 or 4.5 regardless of the inoculation time.

• Korean Journal of Environmental Agriculture
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• v.15 no.4
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• pp.448-454
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• 1996

This studies was carried out to know the effects of $ultraviolet-B(280{\sim}320nm)$ irradiation on the initial growth of Tilia amurensis Rupr. seedlings. UV-B irradiation inhibited the hypocotyl elongation, height growth, leaf growth, and chlorophyll formation. The inhibition was dose-dependent, and consequently those growths were more inhibited depending on the increase of UV-B levels. Morphological change such as leaf length/leaf width ratio was also observed in the leaves of irradiated seedlings. UV-B irradiation produced scorching, glazing or chlorosis, and stunting or dwarfing in the first or second leaf of the seedlings.

• Korean Journal Plant Pathology
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• v.10 no.3
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• pp.169-174
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• 1994

A new unidentified pear leaf spot disease presumed to first occur in the late 1970's has recently become prevalent over the pear growing areas, and caused the greatest problem for pear production in Korea. The disease began to develop on pear leaves at mid- to late May, peaked at mid- to late une, but stopped further development until September in cool climate. Leaf lesions are 0.9∼2.5 mm in diam., oval or irregular to rectangular in shape, first appeared reddish purple, later changed to dark brown, and to whitish grey in the late season. Lesions were limited to appear only on the mature, hardened leaves, initially from leaf margin or near the leaf veins, and later scattered over the leaf surface. Individual lesions usually did not enlarge, but often coalesced each other, commonly causing shot holes and eventual early falling. The disease was most severe on the major pear cultivars Niitaka and Okusankichi ranged with 4 to 100% infections in trees, depending on the orchards, but not on the cultivar Chojuro. Damages from the disease included lower fruit weight, and higher acid and less sugar content in fruits, resulting in lowering the overall fruit quality. Etiology of the disease including identification of the causal organism is in a separate paper.

• Korean Journal of Environmental Agriculture
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• v.12 no.2
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• pp.153-161
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• 1993

This study was conducted to compare the resistance and sensitivity of trees with 6 native species exposing to 4 different levels of $SO_2$gas(0.4, 0.7, 1.5 and 3.0 ppm) respectively. The results are summarized as follows : 1. Visible injuries appeared as spots in the region of intervein on the leaves for all the species and the color of the spots changed from light green and/or brown to light brown, dark brown, and/or redish brown. 2. The sensitivity of the species to $SO_2$ was high in the descending order of Zizyphus jujuba, Cataegus pinnatifida, Viburnum sargentii, Weigela subsessilis, Euonymus japonica, and Acer ginnala. 3. The resistance of the species to $SO_2$ was high in the descending order of Acer ginnala, Eunymus japonica Viburnum sargentii, Weigela subsessilis, Zizyphus jujuba, and Crataegus pinnatifida. 4. When the trees were exposed to $SO_2$gas, the contents of chlorophyll a, b, and a+b were consostently lower than those of control, and water soluble sulfur contents in the leaves were higher than those of control. 5. There was no significant correlation between stomatal resistance and the sensitivity(or resistance) of the trees exposed to $SO_2$ gas. 6. In this study, it was concluded that Acer ginnala was more suitable species than the others for landscape in air polluted area because it showed high resistance, low sensitivity, and low stromal resistance to $SO_2$gas exposure.

• Research in Plant Disease
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• v.19 no.4
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• pp.273-280
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• 2013

Tomato spotted wilt virus (TSWV) was occurred at 8 areas including Naju, Suncheon, Younggwang, Youngam, and Shinan in Jeonnam province and the crops of Younggwang were severely damaged by TSWV. The hot pepper (Capsicum annuum), bell pepper (Capsicum annuum v ar. angulosum) and tomato (Solanum lycopersicon) in greenhouse and hot pepper in open field were infected by TSWV. Especially, hot pepper was severely damaged by TSWV infection. The survey data indicated that 1.1-30% in the nursery field at Naju, Suncheon, and Jangheung were infected by TSWV. Plants were infected by TSWV from early June to August. However, TSWV-infected seedlings from nursery fields showed the disease symptoms from May after transplanting. In pepper greenhouses, Frankliniella occidentalis was more dominant insect vector than Frankliniella intonsa. But in open field, the population of insect vector was opposed to greenhouse. In addition, the removal of weeds was able to delay the incidence of TSWV via side-window of greenhouse in Winter. Taken together, the control of weed and insect vector nearby side-window of greenhouse is important to prevent TSWV infection of plants.

• Korean Journal of Environmental Agriculture
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• v.15 no.4
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• pp.419-424
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• 1996

A green house experiment was conducted to investigate the performance of Chinese cabbage and radish and changes in soil chemical properties after application of different amounts of simulated acid rain (SAR). About 10mm of normal water (pH 6.0), 5mm of SAR followed by 5mm of normal water, and 10mm of SAR were applied 24 times at the two-day intervals. The results obtained are summarized as follows : 1. Visible symptoms were dark brown, red brown, or grey brown leaf spots, reduced leaf size, or some times wrinked leaves in both crops. The visible symptoms started after the third application of SAR. The degree of damages was greater as the amounts and the number of times of SAR application increased. 2. Chlorophyll contents of SAR applied leaves decreased as the amounts of SAR application increased. 3. As the amounts of SAR increased, length, diameter, and fresh weight of Chinese cabbage heads and radish roots decreased. 4. In both crops sulfur content increased, while calcium content decreased as the amounts of SAR increased. Contents of N, P, K, and Mg were not significnatly affected by the amounts of SAR. 5. SAR decreased soil pH and exchangeable cations (Ca, Mg, K), while increased soil sulfur content.

• Korean Journal of Environmental Agriculture
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• v.15 no.3
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• pp.341-347
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• 1996

A green-house experiment was conducted to investigate the growth of Chinese cabbage, radish, and soybean and changes in soil chemical properties after application of 5 and 10mm of pH 2.7 simulated acid rain(SAR) followed by 0, 5, and 10mm of pH 6.0 normal water at the three-day intervals 20 times for Chinese cabbage and radish and 42 times for soybean. The results obtained are summarized as follows: 1. Visual damages by SAR were white-yellow leaf spots, dark brown or light green leaf color, and wrinkled leaf margins in all crops. The degree of visual damages was severer at 10mm than at 5mm SAR and it was reduced as the amounts of normal water increased after SAR application. 2. Chlorophyll content was higher at 10mm than at 5mm SAR application and increased as the amounts of normal water increased after SAR application in all crops. 3. Fresh weights of Chinese cabbage heads and radish roots and grain yield of soybean were higher at 10mm than at 5mm SAR, while they increased as the amounts of normal water increased at the same SAR level. 4. Changes in the mineral contents of plants were not consistent, while S content in radish and soybean increased as the amounts of SAR increased. 5. SAR lowered soil pH, while it increased soil N and S contents. Contents of soil organic matter, P, and exchangeable Ca, Mg, and K were not affected by the amounts of SAR.