• Korean Journal of Soil Science and Fertilizer
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• v.45 no.6
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• pp.910-919
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• 2012

The role of inorganic nitrogen assimilation in the production of amino acids, organic acids and soluble sugars is one of the most important biochemical processes in plants, and, in order to achieve normally, nitrate uptake and assimilation is essential. For this reason, the characterization of nitrate assimilation and metabolite composition from leaves, roots and xylem sap of tomato (Solanum lycopersicum) was investigated under different nitrate levels in media. Tomato plants were grown hydroponically in liquid culture under five different nitrate regimes: deficient (0.25 and 0.75 mM $NO_3{^-}$), normal (2.5 mM $NO_3{^-}$) and excessive (5.0 and 10.0 mM $NO_3{^-}$). All samples, leaves, roots and xylem sap, were collected after 7 and 14 days after treatment. The levels of amino acids, soluble sugars and organic acids were significantly decreased by N-deficiency whereas, interestingly, they remained higher in xylem sap as compared with N-normal and -surplus. The N-excessive condition did not exert any significant changes in metabolites composition, and thus their levels were similar with N-normal. The gene expression and enzyme activity of nitrate reductase (NR), nitrite reductase (NIR) and glutamine synthetase (GS) were greatly influenced by nitrate. The data presented here suggest that metabolites, as a signal messenger, existed in xylem sap seem to play a crucial role to acquire nitrate, and, in addition, an increase in ${\alpha}$-ketoglutarate pathway-derived amino acids under N-deficiency may help to better understand plant C/N metabolism.

• Journal of Plant Biology
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• v.34 no.4
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• pp.253-260
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• 1991

Spirodela polyrhiza and Lemna aequinoctialis often occurred at the sites of high ammonium concentration and at the sites of high nitrate concentration, respectively. We investigated the different distribution between two species in relation to the type of nitrogen sources and their concentrations. Our experiments showed that L. aequinoctialis grew faster than S. polyrhiza in nitrate media with lower than 15 mM concentration. The nitrate uptake was also faster in L. aequinoctialis than in S. polyrhiza. However, neither differences in growth nor in uptake patterns between these two species were observed in ammonium media. Glutamine synthetase (GS), glutamate dehydrogenase (GDH) and glutamate synthetase (GOGAT) activities were higher in L. aequinoctialis. In particular, nitrate reductase activity (NRA) in L. aequinoctialis was 12.1 times as high as that in S. polyrhiza. These results showed that the two species responded varyingly to the types of nitrogen sources and their concentrations. Therefore, the difference in geographic distribution between the two species appeared to reflect the interspecific differences in enzyme activities and, subsequently, nitrogen absorption abilities.

• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2005.11a
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• pp.65-70
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• 2005

A growing body of evidence shows that nitric oxide $({\cdot}NO)$ and ${\cdot}NO-derived$ reactive nitrogen species (RNS) act as both plant physiological regulators and stressors. However, very little is known concerning metabolism of RNS in plant cells. In this paper, we explore a plant metabolic basis for RNS, with special emphasis on the possible relationship to nitrogen assimilation, and discuss the potential of the metabolic engineering for plant-biotechnological application.

• The Korean Journal of Ecology
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• v.10 no.4
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• pp.175-182
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• 1987

Soybeans(Glycine max Merr. cv. Kwanggyo), inoculated with Rhizobium japonicum 110 and then sand-cultured with nitrate gradients (0, 1, 3, 10 and 30mM KNO3). were studied on the growth analysis, nitrogen fixation and nitrogen economy during the growing period. The maxium values of total leaf area, biomass and nitrogen quantity were increased 139%, 122% and 161%, respectively with higher concentration of nitrate treatment. Nodulation showed significant linear correlation with leaf area growth for each treatment of nitrate concentration increased. The more nitrate concentration increased, the more distribution ratios of dry matter and nitrogen to nodule decreased, and the more T/R ratios, CGR and N content increased. On the other hand, F/C ratios and RGR showed little changes. The amounts of nitrogen fixation of soybean alloted to 0, 1, 3, 10 and 30mM nitrate treatments were 100, 46, 14, 0.1 and 0.004% for the total nitrogen assimilation, respectively. The nitrogen utility of soybean plant was smaller than that of other plants and ranged from 23 to 30 at varying nitrate gradients.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.4
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• pp.366-371
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• 2011

The sea squirt Halocynthia roretzi is mainly cultured in Tongyeong, Southern coastal area of Korea. This study presents the physiological rates of respiration, excretion, feeding and assimilation efficiency of the sea squirt Halocynthia roretzi to analyze the SFG(scope for growth) and net growth efficiency, determined during 2007. Oxygen consumption and nitrogen excretion rates increased with a rise in temperature during the summer period whereas feeding rates decreased. The O:N ratio was high during winter(October to February). Assimilation efficiency showed an annual average of 75.4% during the experimental period, except during a period of elevated temperature in July to September(average $25^{\circ}C$). Net growth efficiency($K_2$) was 8.7 to 64.2% except for May to September, when temperature increased at the aquaculture farm. SFG was negative from May to September, reflecting high temperatures and low feeding rates during this period; its highest positive values occurred during winter.

• Molecules and Cells
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• v.40 no.3
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• pp.178-185
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• 2017

Nitrogen is one of the most important mineral elements for plant growth. We studied the functional roles of Oryza sativa DNA BINDING WITH ONE FINGER 18 (OsDOF18) in controlling ammonium uptake. The growth of null mutants of OsDOF18 was retarded in a medium containing ammonium as the sole nitrogen source. In contrast, those mutants grew normally in a medium with nitrate as the sole nitrogen source. The gene expression was induced by ammonium but not by nitrate. Uptake of ammonium was lower in osdof18 mutants than in the wild type, while that of nitrate was not affected by the mutation. This indicated that OsDOF18 is involved in regulating ammonium transport. Among the 10 ammonium transporter genes examined here, expression of OsAMT1;1, OsAMT1;3, OsAMT2;1, and OsAMT4;1 was reduced in osdof18 mutants, demonstrating that the ammonium transporter genes function downstream of OsDOF18. Genes for nitrogen assimilation were also affected in the mutants. These results provide evidence that OsDOF18 mediates ammonium transport and nitrogen distribution, which then affects nitrogen use efficiency.

• KSBB Journal
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• v.13 no.4
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• pp.391-398
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• 1998

The effect of culture medium copper availability on the specific growth rate(${\mu}$) and carbon conversion efficiency (CCE) was sutided for an obligatory methanotroph Methylosinus trichosporium OB3b under various combinations of carbon and nitrogen sources. Methane or methanol was used as a carbon source, and nitrate or ammonium was used as a nitrogen source. Medium copper availability determined the intracellular location or kind of methane monooxygenase (MMO), cell-membrane (particulate or pMMO) when copper was present and cytoplasm (soluble or sMMO) when copper was deficient. When methane was used as a carbon source, copper-containing medium exhibited higher ${\mu}$ and CCE than copper-free medium regardless of the kind of nitrogen source. When methanol was used as a carbon source, however, the effect of copper disappeared. Ammonium gave the higher ${\mu}$ and CCE than nitrate for both methane and methanol. Those observation suggest that there exist an important difference in energy utilization efficiency for methane assimilation between sMMO and pMMO.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.36 no.6
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• pp.545-553
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• 1991

To find out the basic data for the possibility of agricultural utilization for GSA (Glutamine Synthetase Activity), the effect of nitrogen on the GSA in wheat leaf discs, the variation of GSA after light treatment and the comparative activity of GS during preservation were studied. The result of this study suggested that GSA could play an important and direct regulatory role in the nitrogen assimilation by wheat. During the growth stage of wheat its integral activity was found to closely match the organic nitrogen content. GS may therefore be the rate limiting enzyme in inorganic N assimilation. Moreover, integral GSA was closely correlated with grain yield and grain nitrogen. GSA could be suitable to utilize as a parameter for super type selection and an indicator for optimum nitrogen fertilization. Throughout the experiment, the contents of NO; were increased by N fertilization so that the NO; content was not attributable to change in the level of GSA. At investigation during dark-light transition of culture, no change in the level of GSA was observed until after 8-14 hours in the light treatment. And the level of GSA in wheat leaf discs during preservation at refrigerated storage $(-20^{\circ}C)$ was stable until 12 weeks, when its leaf discs were sampled with liquid nitrogen.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.1
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• pp.11-19
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• 1999

This experiment was conducted with nine wheat geno-types to choose the wheat which has excellent early vigour. 'Vigour 18' and 'ZL 59A' are excellent in the long coleoptile genotype, while 'Amery' and 'Janz' are excellent in the short coleoptile genotype. Responding to the growth stage and nitrogen level, Vigour 18 is predominant in the long coleoptile genogype, while Janz in the short coleoptile genotype. Responding to sowing density and nitrogen level, the higher the sowing density was, the shorter the leaf area of Vigour 18 and Janz. Also the leaf area turned out to larger in the plot fertilized with high nitrogen than in the plot fertilized with low nitrogen. This is true of leaf weight and root weight. Concerning specific leaf area (SLA) and leaf area ratio (LAR), the higher the sowing density was, the SLA tended to grow larger, while the SLA grew larger in the plot fertilized with low nitrogen, as were found in Vigour 18 and Janz. The roots of long coleoptile genotype, Vigour 18, turned out to grow longest on the plot sown with 3 seeds. While the roots of short coleoptile genotype, Janz, grew longest on the plot sown with 2 seeds. The relative growth rate (RGR) was the same at low N rates and high N rates. The RGR was 0.071 and 0.072 g $g^{-1}d^{-1}$ at low N rates and high N rates. The partitioning of RGR into net assimilation rate (NAR) and LAR showed that the average LAR at low N rates was similar to the LAR at high N rates. Variation within each cultivar in the LAR and NAR was small relative to the difference between them at low N rates and high N rates. Above ground mass was 8.2 mg greater at high N rates than low N rates, whereas leaf area was 0.05 $\textrm{m}^2$$kg^{-l}$ greater at high N rates than low N rates. The NAR was similar at low N rates and high N rates, whereas LAR was greater at high N rates (0.05 $\textrm{m}^2$$kg^{-l}$); variation in SLA was responsible for the variation in NAR and LAR both at low N rates and high N rates. NAR was more closely associated with the reciprocal of SLA.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.38 no.5
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• pp.458-465
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• 1993

Water culture experiments were carried out to elucidate the effects of N availability, temperature and water potential of culture solution on the uptake and assimilation of N and dry matter accumulation by barley seedlings. N assimilation and dry matter accumulation at 3 to 4 leaves stage in barley plants were maximized at about 3.4 % of N concentration in leaf. N assimilation by barley plants increased with increase of nitrate concentration up to 80ppm in the solution. Over this level nitrate began to accumulated in the leaves and stems proportionally to the N availability in culture solution. Nitrate reductase activity increased in parallel with the increase in the concentration of reduced N in leaves. N uptake by barley plants decreased markedly when water potential reduced below -2 bar or when temperature dropped below 5$^{\circ}C$. These results suggest that the basal application rate of N, 60kg per hectare, for the barley crop needs to be re-examined under the concept of N use efficiency with taking into consideration of temperature and soil N availability because about a half of N accumulated in the leaves of barley plant before wintering is known to be lost by winter killing of above-ground part of the plant.