• Journal of Life Science
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• v.18 no.8
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• pp.1164-1168
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• 2008

We investigated gravitropic responses in the primary root of maize (Zea mays) seedlings which were exposed to salt stress. The maize roots salt-stressed with higher than 100 mM NaCl or KCl started to reveal enhanced gravitropic curvature after 2 hours form the gravi-stimulation. Such a promotion was not caused by sodium phosphate, but invoked by potassium phosphate, indicating the active component is $K^{+}$. Because NaCl increased gravitropic curvature, despite that $Na^{+}$ did not played any role, we evaluated the role for $Cl^{-}$ by comparing the effects of $MgCl_2$ and $MgSO_4$. The enhancement of the curvature only with $MgCl_2$ revealed that $Cl^{-}$ played a role in the gravi-response, indicating the involvement of anion channels. These results suggest that both of $K^{+}$ and $Cl^{-}$ play roles in the regulation of osmosis that is required for cell expansion in gravitropism as well as in nyctinasty and stomatal opening.

• Korean Journal of Environmental Agriculture
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• v.6 no.2
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• pp.22-30
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• 1987

Maize plants, grown on a German soil and a Korean soil which had treated with benzene-ring-labelled $^{14}C-Bentazon$ (5.02mg/kg) immediately before planting (T-0), took up $36.0{\sim}42.8%$ of the radioactivity present during a 21 day growing period. Plants grown on the same soils $(4.79{\sim}4.84mg/kg)$ which had been treated with Bentazon and pre-incubeted for 105days absorbed $8.2{\sim}14.2%$ (T-1) of the radioactivity. Plants grown in soils $(5.56{\sim}7.95mg/kg)$ treated with Bentazon which had been incubated for 105 days and then exhaustively extracted with distilled water and/or 0.01 M $CaCl_2$ to produce non-extractable residues (T-2) took up $1.8{\sim}2.3%$ of the radioactivity. The distribution of the absorbed radioactivity ranged from 2.7 to 9.7% in shoots and from 90.3 to 97.3% in roots. Extraction of maize roots revealed that $39.1{\sim}51.3%$ of the radioactivity was bound in T-0 and $55.7{\sim}63.1%$ was bound in T-1, This suggests hat polar metabolites and parent Bentazon might be present as conjugates.

• Korean Journal of Environmental Agriculture
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• v.14 no.2
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• pp.186-201
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• 1995

In order to elucidate the fate of the residues of the pyrethroid acaricide-insecticide, acrinathrin in soil, maize plants were grown for one month on the specially-made pots filled with two different types of soils containing fresh and one-month-aged residues of [$^{14}C$]acrinathrin, respectively. The mineralization of [$^{14}C$]acrinathrin to $^{14}CO_2$ during the one-month period of aging and of maize cultivation amounted to $23{\sim}24%$ and $24{\sim}33%$, respectively, of the original $^{14}C$ activities. At harvest after one-month growing, the shoots and roots contained less than 0.1% and 1% of the originally applied $^{14}C$ activity, respectively, whereas the $^{14}C$ activity remaining in soil was $65{\sim}80%$ in both soils. Three degradation products with m/z 198(3-phenoxybenzaldehyde), m/z 214(3-phenoxybenzoic acid), and m/z 228(methyl 3-phenoxybenzoate) besides an unknown were identified from acetone extracts of both soils without and with maize plants after treatment of [$^{14}C$]acrinathrin, by autoradiography and GC-MS, and those with m/z 225(3-phenoxybenzaldehyde cyanohydrin) and m/z 198 (3-phenoxybenzaldehyde) from acetone extract of the Soil A treated with 50 ppm acrinathrin and grown with maize plants for 30 days were identified by mass spectrometry. These results suggested that the hydrolytic cleavage of the ester linkage adjacent to the $^{14}C$ with a cyano group, forming 3-phenoxybenzaldehyde cyanohydrin. The removal of hydrogen cyanide therefrom leads to the formation of 3-phenoxybenzaldehyde as one of the major products. The subsequent oxidation of the aldehyde to 3-phenoxybenzoic acid, followed by decarboxylation would evolve $^{14}CO_2$. Solvent extractability of the soils where maize plants were grown for 1 month and/or [$^{14}C$]acrinathrin was aged for 1 month was less than 31% of the original $^{14}C$ activity and over 95% of the total $^{14}C$ activity in soil extracts was distributed in the organic phase. Accordingly, acrinathrin turned out to be degraded rapidly in both soils and be bound to soil constituents as well, not being available to crops.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.80-80
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• 2017

Teosinte is now known as a wild variety of corn. It is distributed in Central and South America. It is believed that teosinte contains genes for resistance to flooding because of the climate characteristics of the collected countries. Recent studies have shown that teosinte has the ability to form adventitious roots, to develop aerenchyma tissues of teosinte, and the resistance to toxic substances under flooding soil condition. Therefore, development of corn cultivars to cope with climate change and the growing corn at paddy field in Korea are required to introduce the characteristics of teosinte. However, in order to utilize teosinte resources, preconditions must be settled such as photoperiodic responsibility. Also if the preconditions are studied together with the metabolic level studies, the possibility of utilization will be even higher.

• Applied Biological Chemistry
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• v.37 no.3
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• pp.148-153
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• 1994

Rice black-streaked dwarf virus (RBSDV), a member of the plant reoviridae fijivirus group, causes a serious damage for rice production in Korea. To characterize the RBSDV genome, virus particles were produced by feeding of planthopper (Laodelphax striatellus F.) carring RBSDV to maize plants for 2 days. In $30{\sim}40$ days after feeding, the viral particles were purified from the infected maize roots by using $10{\sim}40%$ sucrose gradient centrifugation. After treatment of 10% SDS to remove the viral coat proteins, ten viral double-stranded RNAs were resolved in agrose gel electrophoresis. Total dsRNA was then used to synthesize cDNA by reverse transcriptase and a cDNA library was constructed in the ${\lambda}gt11$ vector. The phages that contain RBSDV cDNA fragments were selected by hybridizing with the random-primed probe prepared from RBSDV dsRNAs. After subcloning of several cDNA fragments into the pUC19 plasmid vector, one clone (pRV3) was chosen for sequencing. The pRV3 clone was shown to be located on the RBSDV genome fragment No.3 by RNA gel-blot analysis. Sequence analysis of the clone revealed that the pRV3 contains two partial open reading frames.

• Korean Journal of Soil Science and Fertilizer
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• v.50 no.3
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• pp.135-149
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• 2017

In order to obtain promising rice growth-promoting microbial strains that can be used as substitutes for chemical fertilizers, 172 bacterial strains were isolated from rice roots grown in Korean and Russian soils. Out of them, the strains KR076, KR083, KR181 and RRj228 showed plant growth-promoting activities on maize seedlings. Bacillus megaterium KR076 and Bacillus sp. KR083 showed both nitrogen-fixing and plant growth-promoting activities, while Rhizobium sp. KR181 and Pseudomonas sp. RRj228 appeared to support only plant growth-promotion, but not $N_2$ fixation. Especially, RRj228 showed high growth promoting activity at low concentrations. Inoculation studies with KR083 and RRj228 revealed a high affinity to the Japonica rice variety such as Junambyeo than the Korean Tongil type variety such as Arumbyeo. Both KR083 and RRj228 strains showed rhizoplane and/or endophytic colonization in Japonica and Tongil types rice when soaked with the bacterial suspension of $1.1{\times}10^5cfu\;ml^{-1}$ for six and twelve hours. However, the total bacterial cell numbers were higher in the roots of Japonica variety than in the Tongil type. In inoculation trials with Daesanbyeo rice variety, the seedlings inoculated with KR181 and RRj228 at the rate of $2.0{\times}10^6cfu\;ml^{-1}$ showed yield increment of 35% and 33% (p < 0.01), respectively, so that they contributed to the replacement of chemical fertilizer at half doses of N, $P_2O_5$, and $K_2O$ in pots. In Junambyeo rice seedlings, the strain RRj228, when inoculated with a cell suspension of $1.8{\times}10^6cfu\;ml^{-1}$, promoted 3.4% higher yield at 70% dose than at a full dose level of N $110kg\;ha^{-1}$ in field. These results suggest that the rhizobacteria KR181 and RRj228 are prospective strains for enhancing rice performance.

• Journal of Plant Biology
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• v.24 no.1
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• pp.1-12
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• 1981

Phosphorus dynamics in terms of specific absorption rate, inflow and outflow rates. turnover rate, demand and supply, and utility index of a high yield Zea mays L. cv. Bokgyo field were evaluated using an analysis of successive production structures. The analysis was adopted for measuring quantitative changes in the population by stratified clip technique on every two weeks during the growing season. The seasonal trends of specific absorption rate (2. 4 mg P/g/day in maximum) and specific absorption efficiency (0. 03) closely correlated with that of relative growth rate of the population. The overall inflow and outflow of phosphorus was 3.41 g P/$m^2$/yr showing the maximum inflow of 2.99 g P/$m^2$/month in July. While the maximum phosphorus standing crop was 1.4 g P/$m^2$ showing the maximum turnover rate of 178% in late June. The accumulation of phosphorus along plant height declined monotonically in stems and roots but increased in foliage after heading. The proportions of the total annual demand of phosphorus were 24.4% for leaves, 22.5% for stems, 49.6% for fruits and 3.5% for roots. These demands were met with internal (18.2 %) and external (81.8 %) supplies. The seasonal highest phosphorus utility index was 1,091 in early June, while the average value was 655.

• Journal of Microbiology and Biotechnology
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• v.22 no.4
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• pp.437-447
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• 2012

Natural and beneficial associations between plants and bacteria have demonstrated potential commercial application for several agricultural crops. The sunflower has acquired increasing importance in Brazilian agribusiness owing to its agronomic characteristics such as the tolerance to edaphoclimatic variations, resistance to pests and diseases, and adaptation to the implements commonly used for maize and soybean, as well as the versatility of the products and by-products obtained from its cultivation. A study of the cultivable bacteria associated with two sunflower cultivars, using classical microbiological methods, successfully obtained isolates from different plant tissues (roots, stems, florets, and rhizosphere). Out of 57 plant-growth-promoting isolates obtained, 45 were identified at the genus level and phylogenetically positioned based on 16S rRNA gene sequencing: 42 Bacillus (B. subtilis, B. cereus, B. thuringiensis, B. pumilus, B. megaterium, and Bacillus sp.) and 3 Methylobacterium komagatae. Random amplified polymorphic DNA (RAPD) analysis showed a broad diversity among the Bacillus isolates, which clustered into 2 groups with 75% similarity and 13 subgroups with 85% similarity, suggesting that the genetic distance correlated with the source of isolation. The isolates were also analyzed for certain growth-promoting activities. Auxin synthesis was widely distributed among the isolates, with values ranging from 93.34 to 1653.37 ${\mu}M$ auxin per ${\mu}g$ of protein. The phosphate solubilization index ranged from 1.25 to 3.89, and siderophore index varied from 1.15 to 5.25. From a total of 57 isolates, 3 showed an ability to biologically fix atmospheric nitrogen, and 7 showed antagonism against the pathogen Sclerotinia sclerotiorum. The results of biochemical characterization allowed identification of potential candidates for the development of biofertilizers targeted to the sunflower crop.

• Research in Plant Disease
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• v.15 no.2
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• pp.101-105
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• 2009

The biocontrol agent Serratia plymuthica A21-4 was selected and proved as an excellent inhibitor of Phytophthora blight of pepper through in vitro and in vivo experiments in previous studies. To enhance the colonizing density of S. plymuthica A21-4 on plant root and rhizosphere soil, some soil conditions might effect on the colonization of the bacteria were examined. The results obtained from the study indicated that the soils containing more sand were favorable to root colonization of S. plymuthica A21-4. Organic amendment such as 3% maize straw(w/w) was helpful to colonize the bacteria in root and soil. The soil temperature about $20^{\circ}C$, water content around 40%, and soil pH near to neutral or slightly acidic, were optimum condition for the colonization of S. plymuthica A21-4 in the rhizosphere soil and roots of pepper. In addition, existence of indigenous biotic entities was beneficial to the colonization of S. plymuthica A21-4.

• Korean Journal of Soil Science and Fertilizer
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• v.46 no.2
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• pp.73-80
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• 2013

Due to the fact that possible risk associated with soil-crop-food chain transfer, metal contamination in croplands has become a major topic of wide concern. Accumulation of toxic metals in edible parts of crops grown in contaminated soils has been reported from number of crops including rice, soybean, wheat, maize, and vegetables. Therefore, in order to ensure food safety, measures are needed to be taken in mitigating metal pollution and subsequent uptake by crop plants. Present paper critically reviewed some of the cost effective remediation techniques used in minimizing metal uptake by crops grown in contaminated soils. Liming with different materials such as limestone ($CaCO_3$), burnt lime (CaO), slaked lime [$Ca(OH)_2$], dolomite [$CaMg(CO_3)_2$], and slag ($CaSiO_3$) has been widely used because they could elevate soil pH rendering metals less-bioavailable for plant uptake. Zn fertilization, use of organic amendments, crop rotation and water management are among the other techniques successfully employed in reducing metal uptake by crop plants. However, irrespectively the mitigating measure used, heterogeneous accumulation of metals in different crop species is often reported. The inconsistency might be attributed to the genetic makeup of the crops for selective uptake, their morphological characteristics, position of edible parts on the plants in respect of their distance from roots, crop management practices, the season and to the soil characteristics. However, a sound conclusion in this regard can only be made when more scientific evidence is available on case-specific researches, in particular from long-term field trials which included risks and benefits analysis also for various remediation practices.