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1.
N redistribution patterns and the N composition of vegetative tissues above the peduncle node of wheat ( Triticum aestivum L.) plants with altered reproductive sink strength were evaluated to determine the role of vegetative storage proteins in the temporary storage of excess N destined for export. The degree of leaf senescence symptoms (loss of chlorophyll, total N, and ribulose-1,5-bisphosphate carboxylase/oxygenase) were initially reduced, but the complete senescence of vegetative tissues proceeded even for plants completely lacking reproductive sinks. Plants with 50% less sink strength than control plants with intact spikes redistributed vegetative N to the spike almost as effectively as the control plants. Plants without reproductive sinks exported less N from the flag leaf and had flag leaf blades and peduncle tissues with higher soluble protein and α-NH 2 amino acid levels than control plants. An abundant accumulation of polypeptides in the soluble protein profiles of vegetative tissues was not evident in plants with reduced sink strength. Storage of amino acids apparently accommodates any excess N accumulated by vegetative tissues during tissue reproductive growth. Any significant role of vegetative storage proteins in the N economy of wheat is unlikely. 相似文献
2.
An experiment was conducted to investigate alterations in uptake and assimilation of NO 3− by phosphorus-stressed plants. Young tobacco plants ( Nicotiana tabacum [L.], cv NC 2326) growing in solution culture were deprived of an external phosphorus (P) supply for 12 days. On selected days, plants were exposed to 15NO 3− during the 12 hour light period to determine changes in NO 3− assimilation as the P deficiency progressed. Decreased whole-plant growth was evident after 3 days of P deprivation and became more pronounced with time, but root growth was unaffected until after day 6. Uptake of 15NO 3− per gram root dry weight and translocation of absorbed 15NO 3− out of the root were noticeably restricted in −P plants by day 3, and effects on both increased in severity with time. Whole-plant reduction of 15NO 3− and 15N incorporation into insoluble reduced-N in the shoot decreased after day 3. Although the P limitation was associated with a substantial accumulation of amino acids in the shoot, there was no indication of excessive accumulation of soluble reduced- 15N in the shoot during the 12 hour 15NO 3− exposure periods. The results indicate that alterations in NO 3− transport processes in the root system are the primary initial responses limiting synthesis of shoot protein in P-stressed plants. Elevated amino acid levels evidently are associated with enhanced degradation of protein rather than inhibition of concurrent protein synthesis. 相似文献
3.
It is unclear if the relative content of NO 3− and reduced N in xylem exudate provides an accurate estimate of the percentage reduction of concurrently absorbed NO 3− in the root. Experiments were conducted to determine whether NO 3− and reduced N in xylem exudate of vegetative, nonnodulated soybean plants ( Glycine max [L.] Merr., `Ransom') originated from exogenous recently absorbed 15NO 3− or from endogenous 14N pools. Plants either were decapitated and exposed to 15NO 3− solutions for 2 hours or were decapitated for the final 20 minutes of a 50-minute exposure to 15NO 3− in the dark and in the light. Considerable amounts of 14NO 3− and reduced 14N were transported into the xylem, but almost all of the 15N was present as 15NO 3−. Dissimilar changes in transport of 14NO 3−, reduced 14N and 15NO 3− during the 2 hours of sap collection resulted in large variability over time in the percentage of total N in the exudate which was reduced N. Over a 20-minute period the rate of 15N transport into the xylem of decapitated plants was only 21 to 36% of the 15N delivered to the shoot of intact plants. Based on the proportion of total 15N which was found as reduced 15N in exudate and in intact plants in the dark, it was estimated that 5 to 17% of concurrently absorbed 15NO 3− was reduced in the root. This was much less than the 38 to 59% which would have been predicted from the relative content of total NO 3− and total reduced N in the xylem exudate. 相似文献
4.
An experiment was conducted to investigate the relative changes in NO 3− assimilatory processes which occurred in response to decreasing carbohydrate availability. Young tobacco plants ( Nicotiana tabacum [L.], cv NC 2326) growing in solution culture were exposed to 1.0 millimolar 15NO 3− for 6 hour intervals during a normal 12 hour light period and a subsequent period of darkness lasting 42 hours. Uptake of 15NO 3− decreased to 71 to 83% of the uptake rate in the light during the initial 18 hours of darkness; uptake then decreased sharply over the next 12 hours of darkness to 11 to 17% of the light rate, coincident with depletion of tissue carbohydrate reserves and a marked decline in root respiration. Changes also occurred in endogenous 15NO 3− assimilation processes, which were distinctly different than those in 15NO 3− uptake. During the extended dark period, translocation of absorbed 15N out of the root to the shoot varied rhythmically. The adjustments were independent of 15NO 3− uptake rate and carbohydrate status, but were reciprocally related to rhythmic adjustments in stomatal resistance and, presumably, water movement through the root system. Whole plant reduction of 15NO 3− always was limited more than uptake. The assimilation of 15N into insoluble reduced-N in roots remained a constant proportion of uptake throughout, while assimilation in the shoot declined markedly in the first 18 hours of darkness before stabilizing at a low level. The plants clearly retained a capacity for 15NO 3− reduction and synthesis of insoluble reduced- 15N even when 15NO 3− uptake was severely restricted and minimal carbohydrate reserves remained in the tissue. 相似文献
5.
Nitrogenase-dependent acetylene reduction activity of glasshouse-grown alfalfa ( Medicago sativa L.) decreased rapidly in response both to harvesting (80% shoot removal) and applied NO 3− at 40 and 80 kilograms N per hectare. Acetylene reduction activity of harvested plants grown on 0 kilogram N per hectare began to recover by day 15 as shoot regrowth became significant. In contrast, acetylene reduction activity of all plants treated with 80 kilograms NO 3−-N per hectare and harvested plants treated with 40 kilograms NO 3−-N per hectare remained low for the duration of the experiment. Acetylene reduction of unharvested alfalfa treated with 40 kilograms N per hectare declined to an intermediate level and appeared to recover slightly by day 15. Changes in N 2-fixing capacity were accompanied by similar changes in levels of nodule soluble protein. 相似文献
6.
An experiment was conducted to determine the extent that NO 3− taken up in the dark was assimilated and utilized differently by plants than NO 3− taken up in the light. Vegetative, nonnodulated soybean plants ( Glycine max L. Merrill, `Ransom') were exposed to 15NO 3− throughout light (9 hours) or dark (15 hours) phases of the photoperiod and then returned to solutions containing 14NO 3−, with plants sampled subsequently at each light/dark transition over 3 days. The rates of 15NO 3− absorption were nearly equal in the light and dark (8.42 and 7.93 micromoles per hour, respectively); however, the whole-plant rate of 15NO 3− reduction during the dark uptake period (2.58 micromoles per hour) was 46% of that in the light (5.63 micromoles per hour). The lower rate of reduction in the dark was associated with both substantial retention of absorbed 15NO 3− in roots and decreased efficiency of reduction of 15NO 3− in the shoot. The rate of incorporation of 15N into the insoluble reduced-N fraction of roots in darkness (1.10 micromoles per hour) was somewhat greater than that in the light (0.92 micromoles per hour), despite the lower rate of whole-plant 15NO 3− reduction in darkness. A large portion of the 15NO3− retained in the root in darkness was translocated and incorporated into insoluble reduced-N in the shoot in the following light period, at a rate which was similar to the rate of whole-plant reduction of 15NO3− acquired during the light period. Taking into account reduction of NO3− from all endogenous pools, it was apparent that plant reduction in a given light period (~13.21 micromoles per hour) exceeded considerably the rate of acquisition of exogenous NO3− (8.42 micromoles per hour) during that period. The primary source of substrate for NO3− reduction in the dark was exogenous NO3− being concurrently absorbed. In general, these data support the view that a relatively small portion (<20%) of the whole-plant reduction of NO3− in the light occurred in the root system. 相似文献
7.
Ricinus communis L. plants were grown in nutrient solutions in which N was supplied as NO 3− or NH 4+, the solutions being maintained at pH 5.5. In NO 3−-fed plants excess nutrient anion over cation uptake was equivalent to net OH − efflux, and the total charge from NO 3− and SO 42− reduction equated to the sum of organic anion accumulation plus net OH − efflux. In NH 4+-fed plants a large H + efflux was recorded in close agreement with excess cation over anion uptake. This H + efflux equated to the sum of net cation (NH 4+ minus SO 42−) assimilation plus organic anion accumulation. In vivo nitrate reductase assays revealed that the roots may have the capacity to reduce just under half of the total NO 3− that is taken up and reduced in NO 3−-fed plants. Organic anion concentration in these plants was much higher in the shoots than in the roots. In NH 4+-fed plants absorbed NH 4+ was almost exclusively assimilated in the roots. These plants were considerably lower in organic anions than NO 3−-fed plants, but had equal concentrations in shoots and roots. Xylem and phloem saps were collected from plants exposed to both N sources and analyzed for all major contributing ionic and nitrogenous compounds. The results obtained were used to assist in interpreting the ion uptake, assimilation, and accumulation data in terms of shoot/root pH regulation and cycling of nutrients. 相似文献
8.
In soybean ( Glycine max L. Merr. cv Kingsoy), NO 3− assimilation in leaves resulted in production and transport of malate to roots (B Touraine, N Grignon, C Grignon [1988] Plant Physiol 88: 605-612). This paper examines the significance of this phenomenon for the control of NO 3− uptake by roots. The net NO 3− uptake rate by roots of soybean plants was stimulated by the addition of K-malate to the external solution. It was decreased when phloem translocation was interrupted by hypocotyl girdling, and partially restored by malate addition to the medium, whereas glucose was ineffective. Introduction of K-malate into the transpiration stream using a split root system resulted in an enrichment of the phloem sap translocated back to the roots. This treatment resulted in an increase in both NO 3− uptake and C excretion rates by roots. These results suggest that NO 3− uptake by roots is dependent on the availability of shoot-borne, phloem-translocated malate. Shoot-to-root transport of malate stimulated NO 3− uptake, and excretion of HCO 3− ions was probably released by malate decarboxylation. NO 3− uptake rate increased when the supply of NO 3− to the shoot was increased, and decreased when the activity of nitrate reductase in the shoot was inhibited by WO 42−. We conclude that in situ, NO 3− reduction rate in the shoot may control NO 3− uptake rate in the roots via the translocation rate of malate in the phloem. 相似文献
9.
The aim of this work was to determine which of the two reactions ( i.e. phosphorylation or dephosphorylation) involved in the establishment of the phosphorylated status of the wheat leaf phospho enolpyruvate carboxylase and sucrose phosphate synthase protein responds in vivo to NO 3− uptake and assimilation. Detached mature leaves of wheat ( Triticum aestivum L. cv Fidel) were fed with N-free (low-NO 3− leaves) or 40 m m NO 3− solution (high-NO 3− leaves). The specific inhibition of the enzyme-protein kinase or phosphatase activities was obtained in vivo by addition of mannose or okadaic acid, respectively, in the uptake solution. Mannose at 50 m m, by blocking the kinase reaction, inhibited the processes of NO 3−-dependent phospho enolpyruvate carboxylase activation and sucrose phosphate synthase deactivation. Following the addition of mannose, the deactivation of phospho enolpyruvate carboxylase and the activation of sucrose phosphate synthase, both due to the enzyme-protein dephosphorylation, were at the same rate in low-NO 3− and high-NO 3− leaves, indicating that NO 3− had no effect per se on the enzyme-protein phosphatase activity. Upon treatment with okadaic acid, the higher increase of phospho enolpyruvate carboxylase and decrease of sucrose phosphate synthase activities observed in high NO 3− compared with low NO 3− leaves showed evidence that NO 3− enhanced the protein kinase activity. These results support the concept that NO 3−, or a product of its metabolism, favors the activation of phospho enolpyruvate carboxylase and deactivation of sucrose phosphate synthase in wheat leaves by promoting the light activation of the enzyme-protein kinase(s) without affecting the phosphatase(s). 相似文献
10.
Six genotypes of winter wheat ( Triticum aestivum L.) differing in grain protein concentration were grown on a nutrient solution containing low concentrations of NO 3− (2 millimolar). Total NO 3− uptake varied between genotypes but was not related to grain protein content. An in vivo nitrate reductase assay was used to determine the affinity of the enzyme for NO 3−, and large phenotypic variations were observed. In vivo estimations of the concentration and size of the metabolic pool were variable. However, the three genotypes with the higher ratios of metabolic pool size to leaf total NO 3− concentration were the high protein varieties. It is proposed that a high affinity of nitrate reductase for nitrate might be a biochemical marker for the capacity of the plant to continue assimilating NO 3− for a longer period during the last stage of growth. 相似文献
11.
Ricinus communis L. was used to test the Dijkshoorn-Ben Zioni hypothesis that NO 3− uptake by roots is regulated by NO 3− assimilation in the shoot. The fate of the electronegative charge arising from total assimilated NO 3− (and SO 42−) was followed in its distribution between organic anion accumulation and HCO 3− excretion into the nutrient solution. In plants adequately supplied with NO 3−, HCO 3− excretion accounted for about 47% of the anion charge, reflecting an excess nutrient anion over cation uptake. In vivo nitrate reductase assays revealed that the roots represented the site of about 44% of the total NO 3− reduction in the plants. To trace vascular transport of ionic and nitrogenous constituents within the plant, the composition of both xylem and phloem saps was thoroughly investigated. Detailed dry tissue and sap analyses revealed that only between 19 and 24% of the HCO 3− excretion could be accounted for from oxidative decarboxylation of shoot-borne organic anions produced in the NO 3− reduction process. The results obtained in this investigation may be interpreted as providing direct evidence for a minor importance of phloem transport of cation-organate for the regulation of intracellular pH and electroneutrality, thus practically eliminating the necessity for the Dijkshoorn-Ben Zioni recycling process. 相似文献
12.
The absorption of NO 3− was characterized in six regions of a 7-d-old corn root ( Zea mays L. cv W64A × W182E) growing in a complete nutrient solution. Based on changing rates of 15N accumulation during 15-min time courses, translocation of the concurrently absorbed N through each region of the intact root was calculated and distinguished from direct absorption from the medium. Of the 15N accumulated in the 5-mm root tip after 15 min, less than 15 and 35% had been absorbed directly from the external solution at 0.1 and 10 m m NO 3− concentration of the external solution, respectively. The characterization of the apical portion of the primary root as a sink for concurrently absorbed N was conconfirmed in a pulse-chase experiment that showed an 81% increase of 15N in the 5-mm root tip during a 12-min chase (subsequent to a 6-min labeling period). The lateral roots alone accounted for 60% of root influx and 70% of 15-min whole root 15N accumulation at either 0.1 or 10 m m. NO 3− concentration of the external solution. Because relatively steady rates of 15N accumulation in the shoot were reached after 6 min, the rapidly exchanging pools in lateral roots must have been involved in supplying 15N to the shoot. The laterals and the basal primary root also showed large decreases (24 and 17%) in 15N during the chase experiment, confirming their role in rapid translocation. 相似文献
13.
The role of NO 3− and NO 2− in the induction of nitrite reductase (NiR) activity in detached leaves of 8-day-old barley ( Hordeum vulgare L.) seedlings was investigated. Barley leaves contained 6 to 8 micromoles NO 2−/gram fresh weight × hour of endogenous NiR activity when grown in N-free solutions. Supply of both NO 2− and NO 3− induced the enzyme activity above the endogenous levels (5 and 10 times, respectively at 10 millimolar NO 2− and NO 3− over a 24 hour period). In NO 3−-supplied leaves, NiR induction occurred at an ambient NO 3− concentration of as low as 0.05 millimolar; however, no NiR induction was found in leaves supplied with NO 2− until the ambient NO 2− concentration was 0.5 millimolar. Nitrate accumulated in NO 2−-fed leaves. The amount of NO 3− accumulating in NO 2−-fed leaves induced similar levels of NiR as did equivalent amounts of NO 3− accumulating in NO 3−-fed leaves. Induction of NiR in NO 2−-fed leaves was not seen until NO 3− was detectable (30 nanomoles/gram fresh weight) in the leaves. The internal concentrations of NO 3−, irrespective of N source, were highly correlated with the levels of NiR induced. When the reduction of NO 3− to NO 2− was inhibited by WO 42−, the induction of NiR was inhibited only partially. The results indicate that in barley leaves NiR is induced by NO 3− directly, i.e. without being reduced to NO 2−, and that absorbed NO 2− induces the enzyme activity indirectly after being oxidized to NO 3− within the leaf. 相似文献
14.
The regulation of NO 3− assimilation by xylem flux of NO 3− was studied in illuminated excised leaves of soybean ( Glycine max L. Merr. cv Kingsoy). The supply of exogenous NO 3− at various concentrations via the transpiration stream indicated that the xylem flux of NO 3− was generally rate-limiting for NO 3− reduction. However, NO 3− assimilation rate was maintained within narrow limits as compared with the variations of the xylem flux of NO 3−. This was due to considerable remobilization and assimilation of previously stored endogenous NO 3− at low exogenous NO 3− delivery, and limitation of NO 3− reduction at high xylem flux of NO 3−, leading to a significant accumulation of exogenous NO 3−. The supply of 15NO 3− to the leaves via the xylem confirmed the labile nature of the NO 3− storage pool, since its half-time for exchange was close to 10 hours under steady state conditions. When the xylem flux of 15NO 3− increased, the proportion of the available NO 3− which was reduced decreased similarly from nearly 100% to less than 50% for both endogenous 14NO 3− and exogenous 15NO 3−. This supports the hypothesis that the assimilatory system does not distinguish between endogenous and exogenous NO 3− and that the limitation of NO 3− reduction affected equally the utilization of NO 3− from both sources. It is proposed that, in the soybean leaf, the NO 3− storage pool is particularly involved in the short-term control of NO 3− reduction. The dynamics of this pool results in a buffering of NO 3− reduction against the variations of the exogenous NO 3− delivery. 相似文献
15.
The effects of nitrogen source NO 3− or NH 4+ on nitrogen metabolism during the first 2 weeks of germination of the rice seedling ( Oryza sativa L., var. IR22) grown in nutrient solution containing 40 μg/ml N were studied. Total, soluble protein, and free amino N levels were higher in the NH 4+-grown seedling, particularly during the 1st week of germination. Asparagine accounted for most of the difference in free amino acid level, in both the root and the shoot. Nitrate and nitrite reductase activities were present mainly in the shoot and were higher in the NO 3−-grown seedling, whereas the activity of glutamate dehydrogenase and glutamine synthetase in the root tended to be lower than that of the NH 4+-grown seedling during the 1st week of germination. Glycolate oxidase and catalase activities were present mainly in the shoot. Maximum activity of the above five enzymes occurred 7 to 10 days after germination. Differences in the zymograms of nitrate reductase, glutamate dehydrogenase, and catalase were mainly between shoot and root and not from N source. Nitrite reductase bands were observed only in plants grown in plants grown in NO 3−. 相似文献
16.
Wheat ( Triticum aestivum L.) was grown under CO 2 partial pressures of 36 and 70 Pa with two N-application regimes. Responses of photosynthesis to varying CO 2 partial pressure were fitted to estimate the maximal carboxylation rate and the nonphotorespiratory respiration rate in flag and preceding leaves. The maximal carboxylation rate was proportional to ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) content, and the light-saturated photosynthetic rate at 70 Pa CO 2 was proportional to the thylakoid ATP-synthase content. Potential photosynthetic rates at 70 Pa CO 2 were calculated and compared with the observed values to estimate excess investment in Rubisco. The excess was greater in leaves grown with high N application than in those grown with low N application and declined as the leaves senesced. The fraction of Rubisco that was estimated to be in excess was strongly dependent on leaf N content, increasing from approximately 5% in leaves with 1 g N m −2 to approximately 40% in leaves with 2 g N m −2. Growth at elevated CO 2 usually decreased the excess somewhat but only as a consequence of a general reduction in leaf N, since relationships between the amount of components and N content were unaffected by CO 2. We conclude that there is scope for improving the N-use efficiency of C 3 crop species under elevated CO 2 conditions. 相似文献
17.
Up to 80% of the total nitrate reductase activity (NRA) determined in vivo in different parts of vegetative tobacco plant ( Nicotiana tabacum) was located in the leaves. The NRA reached a peak when a leaf had expanded to 27% of its final weight and 33% of its final area. Thereafter, with advancing expansion and age of the leaf, the activity declined. This pattern of development of NRA during the ontogenesis of leaves was not influenced by raising the supply of NO 3− from 3 to 6 milliequivalent per cubic decimeter in the substrate solution. The concentration of NO 3− in leaves, stem and root was inversely related to NRA at both NO 3− levels. Raising the supply of K + from 1 to 6 milliequivalent per cubic decimeter at either concentration of NO 3− slowed down the development of NRA in the initial stages of expansion, but promoted it subsequently. The peak of the activity which developed in a leaf of 62% of its final area was higher at the higher supply of K +. The higher activity was maintained thereafter in the expanding and in matured and older leaves. It was concluded that NRA and the pattern of its development in expanding leaves is related to the availability of metabolites and their incorporation into enzyme proteins. Both these processes are influenced by: (a) the vertical profile of concentration of K + in the shoot and (b) the concentration of K + in a leaf, which depend upon its supply. 相似文献
18.
We compared growth kinetics of Prorocentrum donghaiense cultures on different nitrogen (N) compounds including nitrate (NO 3
−), ammonium (NH 4
+), urea, glutamic acid (glu), dialanine (diala) and cyanate. P. donghaiense exhibited standard Monod-type growth kinetics over a range of N concentraions (0.5–500 μmol N L −1 for NO 3
− and NH 4
+, 0.5–50 μmol N L −1 for urea, 0.5–100 μmol N L −1 for glu and cyanate, and 0.5–200 μmol N L −1 for diala) for all of the N compounds tested. Cultures grown on glu and urea had the highest maximum growth rates (μ m, 1.51±0.06 d −1 and 1.50±0.05 d −1, respectively). However, cultures grown on cyanate, NO 3
−, and NH 4
+ had lower half saturation constants (K μ, 0.28–0.51 μmol N L −1). N uptake kinetics were measured in NO 3
−-deplete and -replete batch cultures of P. donghaiense. In NO 3
−-deplete batch cultures, P. donghaiense exhibited Michaelis-Menten type uptake kinetics for NO 3
−, NH 4
+, urea and algal amino acids; uptake was saturated at or below 50 μmol N L −1. In NO 3
−-replete batch cultures, NH 4
+, urea, and algal amino acid uptake kinetics were similar to those measured in NO 3
−-deplete batch cultures. Together, our results demonstrate that P. donghaiense can grow well on a variety of N sources, and exhibits similar uptake kinetics under both nutrient replete and deplete conditions. This may be an important factor facilitating their growth during bloom initiation and development in N-enriched estuaries where many algae compete for bioavailable N and the nutrient environment changes as a result of algal growth. 相似文献
19.
The effect of water stress on patterns of nitrate reductase activity in the leaves and nodules and on nitrogen fixation were investigated in Medicago sativa L. plants watered 1 week before drought with or without NO 3−. Nitrogen fixation was decreased by water stress and also inhibited strongly by the presence of NO 3−. During drought, leaf nitrate reductase activity (NRA) decreased significantly particularly in plants watered with NO 3−, while with rewatering, leaf NRA recovery was quite important especially in the NO 3−-watered plants. As water stress progressed, the nodular NRA increased both in plants watered with NO 3− and in those without NO 3− contrary to the behavior of the leaves. Beyond −15.10 5 pascal, nodular NRA began to decrease in plants watered with NO 3−. This phenomenon was not observed in nodules of plants given water only. 相似文献
20.
A more sensitive analytical method for NO 3− was developed based on the conversion of NO 3− to N 2O by a denitrifier that could not reduce N 2O further. The improved detectability resulted from the high sensitivity of the 63Ni electron capture gas chromatographic detector for N 2O and the purification of the nitrogen afforded by the transformation of the N to a gaseous product with a low atmospheric background. The selected denitrifier quantitatively converted NO 3− to N 2O within 10 min. The optimum measurement range was from 0.5 to 50 ppb (50 μg/liter) of NO 3− N, and the detection limit was 0.2 ppb of N. The values measured by the denitrifier method compared well with those measured by the high-pressure liquid chromatographic UV method above 2 ppb of N, which is the detection limit of the latter method. It should be possible to analyze all types of samples for nitrate, except those with inhibiting substances, by this method. To illustrate the use of the denitrifier method, NO 3− concentrations of <2 ppb of NO 3− N were measured in distilled and deionized purified water samples and in anaerobic lake water samples, but were not detected at the surface of the sediment. The denitrifier method was also used to measure the atom% of 15N in NO 3−. This method avoids the incomplete reduction and contamination of the NO 3− -N by the NH 4+ and N 2 pools which can occur by the conventional method of 15NO 3− analysis. N 2O-producing denitrifier strains were also used to measure the apparent Km values for NO 3− use by these organisms. Analysis of N 2O production by use of a progress curve yielded Km values of 1.7 and 1.8 μM NO 3− for the two denitrifier strains studied. 相似文献
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