Nitrogen uptake by tropical orchids
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Cymbidium
Dendrobium
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Aims Nitrogen is very important for improving the yield and quality of peanut. Nitrate reductase (NR), glutamine synthetase (GS) and glutamate dehydrogenase (GDH) are the main enzymes of nitrogen metabolism that would be affected by nitrogen level. Our objective was to study the effects of nitrogen level on soluble protein content, free amino acid content and correlating enzyme activities of nitrogen metabolism in peanut. Methods We carried out a field experiment of two cultivars under four nitrogen levels (0, 45, 90 and 180 N kg·hm–2) and investigated the soluble protein content and free amino acid content in leaf, stem, root and pod of peanut, as well as the activities of the nitrate reductase (NR), glutamine synthetase (GS) and glutamate dehydrogenase (GDH) in these organs. Important findings With the nitrogen application, the soluble protein content and free amino acid content were increased, and the activities of the nitrate reductase (NR), glutamine synthetase (GS) and glutamate dehydrogenase (GDH) also increased. When excessive nitrogen was used, the NR activity and kernel protein content were increased, while the activities of GS and GDH were decreased. Soluble protein content, free amino acid content, NR, GS and GDH along with the growth periods were not affected by nitrogen level, but with suitable nitrogen the activities of NR and GS in different organs could be increased. Also, nitrogen level affected GDH activities in leaf and kernel, with lower effect on the GDH activities in stalk and root. In conclusion, nitrogen level could affect the correlating enzyme activities of nitrogen metabolism in peanut, which resulted in changes of soluble protein content and free amino acid content in organs. The best nitrogen level for peanut was 90 N kg·hm–2.
Glutamate synthase
Nitrogen Cycle
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Using Jin Xing 6007 as rootstock and Nong Da 202 as scion,grafted plants were made to compare the differences in dry leaf weight,some key enzyme activities of nitrogen metabolism(nitrate reductase,glutamine synthetase)and the contents of chlorophyll between grafted and non-grafted tobacco seedlings grown in pot with the different amount of nitrogen.The results showed that nitrate reductase activities,glutamine synthetase activities and the contents of chlorophyll in leaves of grafted seedlings were significantly higher than those of non-grafted seedlings under two different amount of nitrogen.Nitrate reductase activities,glutamine synthetase activities and the contents of chlorophyll of grafted and non-grafted plants were decreasing with the decreasing nitrogen level,they were also decreasing when tobacco leaves were turning to mature.The speed of decreasing in grafted seedlings was slower than that in non-grafted seedlings.These results indicated that higher nitrate reductase activities,glutamine synthetase activities and the contents of chlorophyll might be resulted from the stronger nitrogen efficiency in grafted tobacco seedlings.
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Glufosinate
Medicago sativa
Glutamate synthase
Specific activity
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Glutamate synthase
Nitrogen Assimilation
Nitrogen Cycle
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Cymbidium
Dendrobium
Orchidaceae
Flor
Cut flowers
Vase life
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After flowering, the activities of nitrate reductase (NR) and glutamine synthetase (GS) in different organs of wheat were recorded, especially in flag leaf, their activities were highest. The activities of NR and GS in flag leaf and root gradually reduced after anthesis, but in husks and grains first raised, then reduced.
Anthesis
Flag (linear algebra)
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Glutamate synthase
Nitrogen Assimilation
Asparagine synthetase
Assimilation (phonology)
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Abstract Young wheat (C3) and maize (C4) plants were exposed to near-ambient concentrations of ozone in open-top chambers in order to investigate the possible effects of ozone on nitrogen metabolism. Nitrogen was supplied to the plants by adding 15N-labelled tracer substances via the soil substrate. Enzyme activities (NADH nitrate reductase, nitrite reductase, glutamine synthetase and NADH glutamate dehydrogenase) and the incorporation of 15N were determined. The findings show that nitrogen metabolism was affected by O3, however, there were distinct differences between the two species. In plants treated with O3, NADH nitrate reductase activity in maize leaves was reduced, while NR activity in wheat leaves only slightly declined. Only minor changes were observed with respect to the activities of nitrite reductase, glutamine synthetase and NADH glutamate dehydrogenase. Feeding experiments using 15NO3 − showed that the incorporation of nitrate nitrogen in wheat plants exposed to ozone remains virtually unchanged, whereas in maize plants reduced incorporation rates were observed for nitrate nitrogen. The incorporation of ammonium nitrogen was distinctly increased in wheat and maize by the impact of ozone. When investigating pigment contents, reduced levels of chlorophyll a and b and carotenoids were observed, whereas the pigment content of wheat leaves remained unchanged. These results indicate that young maize plants are more susceptible than wheat plants to short-term ozone exposure. Key Words: Glutamate dehydrogenaseglutamine synthetasenitrate reductasenitrite reductasenitrogen 15ozonestable isotopes Triticum aestivum Zea mays
Glutamate synthase
Nitrogen Assimilation
Nitrogen Cycle
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The patterns of nitrate reduction, nitrate accumulation, and glutamine synthetase activity as a function of leaf development were studied in glasshouse-grown sorghum (Sorghum vulgare L. var. Dourado) seedlings. Leaf nitrate reductase activity increased during early leaf development and reached a maximum at full leaf expansion which was followed by a decline with leaf maturation. Leaf nitrate content closely paralleled the pattern of nitrate reductase activity for each individual leaf along the canopy. Glutamine synthetase activity increased during early leaf development but then remained constant until senescence. Etiolated leaves from nitrate-grown plants had minimal levels of nitrate reductase activity which increased markedly upon illumination. Glutamine synthetase activity was already high in those leaves and increased only slightly during greening. Crude preparations of glutamine synthetase were insensitive to cyanide and both the biosynthetic and transferase assays were enhanced by cysteine. The relatively high activities of glutamine synthetase throughout leaf development and greening indicate that this enzyme does not limit the assimilation of nitrate into amino acids and plays a role in the assimilation of ammonia from sources other than NO 3 − reduction.
Nitrogen Assimilation
Etiolation
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Glutamate synthase
Nitrogen Assimilation
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