• Plant Resources
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• v.8 no.3
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• pp.258-262
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• 2005

In autumn, to determine the optimal planting date and plant density of rapeseed in southern areas of Korea, Yudal variety for autumn sowing, the highest yielding variety was grown under three different planting dates and five different plant densities. Yield components such as plant height, ear length, number of seedling stand per $m^2$, number of branches and pod length were highest at the plots with Sep. 30 of planting date and 30/20 cm drilling of plant density. Yield of seed, oil and 1,000 grains weight were highest at the Sep.30 of planting date and 30/20 cm drilling of plant density. Judging from the results reported above, at optimum planting date and plant density of rapeseed seemed to be Sep.30 of planting date and 30/20cm plant density in autumn sowing.

• Journal of Korean Society of Forest Science
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• v.99 no.5
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• pp.711-719
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• 2010

We investigated physiological responses and phytoextraction ability of Pinus thunbergii in cadmium contaminated soil as part of our efforts in identifying plant materials for the restoration and revegetation of forest soil contaminated by heavy metals. Thirty seedlings (ten per treatment) were assigned to three treatments (control, 0.3 and 0.6 mM $CdSO_4$ solution) at first year experiment. At second year, ten seedlings per treatment treated with Cd during the first year experiment were divided by two groups (no Cd-treated and consecutive Cd-treated group). At first experiment, photosynthetic pigment content, and superoxide dismutase (SOD) and glutathione reductase (GR) activities have significantly reduced by Cd application, and the reduction rate was increased much higher as the rate of Cd application increased. On the other hand, thiol and malondialdehyde (MDA) content were significantly increased at the application of 0.6 mM of Cd. At the second year experiment, a general increase in chlorophyll and carotenoid content was observed with Cd treatment while SOD and GR activities showed a relative reduction compared to the control. Similar to the first year measurement, thiol and MDA contents also increased considerably due to Cd treatment. At harvest, dry matter was significantly reduced by Cd treatment especially at the rate of 0.6 mM Cd, but dry yield of P. thunbergii treated with 0.3 mM Cd was less affected and it was comparable with the control seedling. Cadmium concentration in seedling tissues increased with increasing Cd application rate while Cd uptake was higher in seedlings supplied with 0.3 mM Cd, which could be ascribed to their high dry matter. Overall, our study has demonstrated the unique physiological response of P. thunbergii to Cd-prolonged exposure by showing that the changes in photosynthetic pigment content and antioxidative enzyme activities were dependent on the concentration and duration of treatment. In addition, our results have demonstrated the potential of P. thunbergii to withstand up to 0.3 mM Cd (equivalent to cumulative Cd concentration of 134.4 to 268 mg $kg^{-1}$) without showing growth reduction, hence it might be used for phytoremediation of Cd contaminated areas.

• Horticultural Science & Technology
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• v.30 no.1
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• pp.90-92
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• 2012

A new spray carnation 'Lepus' was released by the National Institute of Horticultural & Herbal Science in 2004. This hybrid was crossed between 'Diamond' and '99257-7 Line' in 2000. The 269 seedling plants were, planted and cultivated in green house. After investigation of the characteristics for four years (from 2001 to 2004), it was finally selected in 2004. 'Lepus' white color with red peak edge is spray type and strong flower stalks. Also, it has medium fragrance, many flowers, and attractive flower arrangement. In particular, flowering was 10 days early and flower stalk was 13cm longer than 'Diamond' (control). In addition, it has medium resistance of Fusarium and the vase life was similar to 'Diamond'.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.27 no.4
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• pp.439-451
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• 1982

In fact, rice cultivation technique from 1962 to 1970 was very slight, but this technique from 1970 to now was remarkably developed in Korea, it was due to development of high fretilizer responsive and lodging resistant variety, Tongil; ie. Ind. ${\times}$ Japonica remote-cross rice variety. The main factors of this development is as follow: Firstly the most farmer (more than 90%) used newly developed seedling growth method; polyethylene film covered protected nursery bed. Secondly date of transplanting (middle or late part. of May) was earlier 10-15days than before 1970. Thirdly new varieties were highly lodging resistant at high fertilizer level $(N-P_2O_5-K_2O:15-9-11 kg/l0a)$. However, this level is 50% increased one than it for Japonica varieties. At forth planting density increased up to 75-80 hills per $3.3m^2$. Added to these factors, farm labor shortage and wage increase due to economic development gave a chance for introduction of transplanting machine to farmer in 1977. It's use increased for 100, 800 ha in 1981. The most of farmers are using herbicides and weed control system dependoing on wood composition has been established and disseminated to farmer.

• Korean Journal of Soil Science and Fertilizer
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• v.34 no.4
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• pp.302-309
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• 2001

The effects of water stress on the development of Alpova dipiophloeus ectomycorrhizas and on the growth of nodulated Alnus rubra Bong seedlings were investigated. Five-day cyclic water stress significantly decreased the ectomycorrhizal development and the seedling growth. However, A. diplophloeus inoculated seedlings did not significantly differ from the non-inoculated seedlings in the growth and physiological activities under both well watered and water stressed conditions. $N_2$-fixation was less sensitive than $CO_2$ fixation to water stress. We conclude that under water stress conditions A. diplophloeus mycorrhizas do not contribute to the fitness of red alder seedlings.

• The Korean Journal of Malacology
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• v.21 no.1
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• pp.65-70
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• 2005

The purpose of this study is to determine the appropriate substrate for larval settlement and spat growth in the purple clam, Saxidomus purpuratus in laboratory culture. Larvae were reared with 3 different types of sediments (mud, sand, and mixed) for 46 days in settlement experiment, and settled spats were further grown in 3 types of sediments for 36 weeks in growth experiment. The density of settled spats in muddy sediments was more than 2 times higher than those in mixed or sandy sediments. But, the average size of settled spats in muddy sediments was smaller than those in mixed or sandy sediments. After 36 weeks of growth period, growth rate decreased as shell length increased. When shell length was less than 2 mm, growth rate in mixed sediments was significantly higher than that in sandy sediments. When shell length was more than 2 mm, there was no significant difference in growth rate among different substrates. Sediment type affected growth rate only when the spats were relatively small (less than 2 mm). Muddy sediments seems better for larval settlement, while mixed sediments is best for spat growth. We suggest the laboratory procedure for enhancing seedling production of S. purpuratus.

• The Plant Pathology Journal
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• v.32 no.1
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• pp.58-64
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• 2016

Bacterial wilt of tomatoes caused by Ralstonia solanacearum is a devastating disease that limits the production of tomato in Korea. The best way to control this disease is using genetically resistant tomato plant. The resistance degree to R. solanacearum was evaluated for 285 tomato accessions conserved in the National Agrobiodiversity Center of Rural Development Administration. These accessions of tomato were originated from 23 countries. Disease severity of tomato accessions was investigated from 7 days to 14 days at an interval of 7 days after inoculation of R. solanacearum under greenhouse conditions. A total of 279 accessions of tomato germplasm were susceptible to R. solanacearum, resulting in wilt and death in 70 to 90% of these plants. Two tomato accessions were moderately resistant to R. solanacearum. Only four accessions showed high resistance against R. solanacearum. No distinct symptom of bacterial wilt appeared on the resistant tomato germplasms for up to 14 days after inoculation of R. solanacearum. Microscopy of resistant tomato stems infected with R. solanacearum revealed limited bacterial spread with thickening of pit membrane and gum production. Therefore, these four resistant tomato germplasms could be used in tomato breeding program against bacterial wilt.

• Journal of Aquaculture
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• v.13 no.4
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• pp.277-284
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• 2000

Rabbitfish hatchlings were given a mixed food of rotifers (Brachionus rotundiformis) and trochophore larvae of oyster. Only the oyster-trochophore larvae were found in the gut of 62-h old fish larvae. The fish larvae, fed on rotifer and ciliate alone did not survive. However, their survival increased to 3.3 % on the 10th day after hatching, when trochophore was supplemented. Corresponding with the accelerated growth, the number of rotifers consumed increased from 11 in a 5-day old fish to 165 in a IS-day old fish. In a field ecosystem containing live diatom, Nannochloropsis oculata, rotifers and copepods, fish larvae were shocked and the oyster's trochophore larvae were fed from 2 to 7 days after hatching. A total of 76,000 seedling were produced after 50 days of hatching with 12.7 % survival. Mean total length and body weight were 65.6 mm and 3.4 g, respectively. Growth of body length (BL), body height (BH), body weight (BW) and head length (HL) as a function of the total length (TL) showed regressional relationships as follows; BL=0.8565 TL+0.0852 ($t^2$=0.9996); BH=0.3207 TL - 0.5052 (($t^2$=0.9641) BW=0.0652 TL2.3508 (($t^2$=0.9925); HL=0.2595 TL - 0.1898 (($t^2$=0.9901)

• Korean journal of applied entomology
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• v.22 no.2 s.55
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• pp.130-137
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• 1983

A wide variety of pathogens are known io be seedborne, carried either as infectious mycelium internally or as contaminants on the seed coat. When seed is infected with a pathogen, the seed nay be rendered nonviable or it may remain viable but produce weak seedling. In some cases, the Infected seedling nay not be severely weakened, but nay serve as a source of primary inoculum within a community of plants. A recent problem nay be the dissemination of seedborne pathogens occurring as a result of the massive movements of seed, as a part of the 'Green revolution' Disease of great danger to agriculture may be introduced with seed from other parts of world. Seed treatment with organic mercury compounds in liquid form had become popular since about 1955. Organic mercury compounds contributed considerably to the increase in production of many crops and vegetables. In 1975, however, the use of organic mercury compound was forbidden because of doubts regarding their residual mammalian toxicity in agricultural products. Benomyl-thiram mixture, thiophanate methyl-;hiram mixture and TCMB have now been registered as seed disinfectants for the use of rice blast, brown spot and Bakanae disease. Oxathiinsthiram mixture has been registered as seed disinfectant for barley and wheat loose smut and leaf stripe of barley. Agricultural techniques have made such rapid progress that the nursery methods changed from the use of paddy nursery to box nursery designed for machine-transplanting. The spread of rice transplanting machines has caused increase of seedborne diseases. Among seedborne diseases, Bakanae disease has remarkably increased and causes much damage recently. In order to counter this trend, seed disinfectants must also be diversified. First, effective non-selective disinfectants need to be developed, and second, appropriate control methods always need to be prepared in parallel with the development of new techniques for cultivation.

• Journal of Biosystems Engineering
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• v.41 no.1
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• pp.21-33
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• 2016

Purpose: In order to ensure that vegetable seedlings (with a soil block around their roots) are planted in an upright orientation after metering in a vegetable transplanter, they need to be dropped freely from a certain height. The walk-behind hand-tractor-powered machines do not have sufficient space to drop the seedlings from that height. In the present work, a hopper-type planting device was developed for the walk-behind hand-tractor-powered vegetable transplanter to ensure that the soil block seedlings are planted in an upright orientation. Methods: Various dimensionless terms were developed based on the dimensional analysis approach, and their effect on the planting of soil block seedlings in an upright orientation (planting efficiency) was studied. The optimum design dimensions of the hopper-type planting device were identified by the Taguchi method of optimization. Results: The ratio of the height of free fall to the sliding distance of the seedling on the surface of the hopper had the highest influence on planting efficiency. The planting efficiency was highest for plants with a height $15{\pm}2cm$. The plant handling Froude number, in interaction with the design of the hopper-type planting device, also significantly affected the planting efficiency. Of the hopper design factors, the length of the slide of the seedlings on the surface of the hopper was most important, and induced sufficient velocity and rotation to cause the seedling to fall in an upright orientation. An evaluation of the performance of the planting device under actual field conditions revealed that the planting efficiency of the developed planting device was more than 97.5%. Conclusions: As the seedlings were fed to the metering device manually, an increase in planting rate increased missed plantings. The planting device can be adopted for any vegetable transplanter in which the seedlings are allowed to drop freely from the metering device.