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  • 1
    Electronic Resource
    Electronic Resource
    Determination of Ammonium, Amide, Amino, and Nitrate Nitrogen in Plant Extracts by a Modified Kjeldahl Method. (1964)
    s.l. : American Chemical Society
    Analytical chemistry 36 (1964), S. 439-441 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac60208a067
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  • 2
    Electronic Resource
    Electronic Resource
    Microdetermination of Silicon in Plants (1958)
    s.l. : American Chemical Society
    Analytical chemistry 30 (1958), S. 1011-1014 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac60137a042
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  • 3
    Electronic Resource
    Electronic Resource
    Photorespiration (1970)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Plant Physiology 21 (1970), S. 385-432 
    Details
    ISSN: 0066-4294
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.pp.21.060170.002125
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  • 4
    Electronic Resource
    Electronic Resource
    Oxygen Uptake by Illuminated Maize Leaves (1969)
    [s.l.] : Nature Publishing Group
    Nature 222 (1969), S. 269-271 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. 1. Concurrent uptake of 1802 and release of 16O2 by illuminated, excised maize leaves (0-65 dm2, one side) in a closed compartment of 943 ml. Air temperature was 35 C. Total O2 was 5-77 per cent. The COZ was at compensation level, N2 was used as a ballast to maintain atmospheric pressure, and ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/222269a0
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  • 5
    Electronic Resource
    Electronic Resource
    Nitrogen-stimulated potassium influx into maize roots: differential response of components resistant and sensitive to ambient ammonium (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 11 (1988), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Potassium (86Rb) influx from 200 mmol m −3 KCl into dark grown, decapitated maize seedlings 6 d old) was stimulated by nitrate pretreatment. The stimulus was clearly evident by 6h exposure to nitrate and required 12–24 h for maximal expression. Decay of the nitrate-stimulated potassium influx was more than 50% complete within 3 h after transfer to nitrogen-free solutions. The stimulation of potassium influx was entirely accounted for by an increase in the influx component that was resistant to inhibition by presence of 200 mmol m−3 ambient ammonium. In contrast, the component of potassium influx that was sensitive to inhibition by ambient ammonium was unaffected by nitrate pretreatment. Exposure to the glutamine synthetase inhibitor L-methionine-dl-sulphoximine (MSX) during nitrate pretreatment stimulated the resistant component but the sensitive component was nearly eliminated. Pretreatment with ammonium increased the resistant component of potassium influx within 3 h, i.e. before it was increased by nitrate pretreatment, but the sensitive component was concomitantly restricted. The latter recovered partially during extended pretreatment with ammonium. The data indicate that the resistant component responded positively to increases in tissue ammonium concentrations whereas the sensitive component was unaffected by tissue ammonium except at concentrations in excess of 10μmol g−1. Ammonium influx was also stimulated by nitrate pretreatment and to a greater extent than potassium influx. Presence of MSX with nitrate during pretreatment resulted in a further stimulation in ammonium influx. The parallel increases in root ammonium concentrations with the two pretreatments imply that part of the increase in ammonium influx was a consequnce of increased counter-transport with endogenous ammonium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1988.tb01788.x
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  • 6
    Electronic Resource
    Electronic Resource
    Nitrate Uptake during Recovery from Nitrogen Deficiency (1976)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 36 (1976), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Two-week-old nitrogen-deficient wheat plants attained a high rate of nitrate uptake on the first day of exposure to nutrient solutions supplemented with KNO3. Ammonium uptake from similar solutions supplemented with NH4NO3 was also high during the first day of exposure, but nitrate uptake from this solution was lower than from the KNO3 treatment. During the next two to three days there was a progressive decrease in uptake of both nitrogen ions. A steady increase in uptake then occurred as the plants fully recovered from the nitrogen-deficient state.The transient low nitrate uptake after three or four days of exposure to KNO3 was not due to an excessive accumulation of nitrate in the tissue, nor to a failure in nitrate reduction as indicated by the rate of nitrate accumulation relative to the uptake rate. Nitrogen supplied as 15N-nitrite during the low uptake period was effectively incorporated into organic forms and effectively translocated to the shoots. Failure of the root tissue to increase in soluble carbohydrates during illumination was characteristic of the low uptake period. This contrasted with an increase in root soluble carbohydrates in the light during rapid uptake associated with full recovery from the nitrogen-deficient state. It is concluded that carbohydrate translocation to the root system was insufficient during the intermediate recovery period for optimal nitrate uptake, although it was sufficient for effective reduction and translocation of nitrate and reduced nitrogen.Ammonium uptake from NH4NO3 was restricted during darkness by the third day whereas there was little difference between light and dark periods in nitrate uptake from KNO3 until about the sixth day of recovery. The extent to which ammonium restricted nitrate uptake increased progressively for two or three days following which a lessening influence seemed evident, and the effects were not directly associated with the rate of ammonium uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1976.tb03931.x
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  • 7
    Electronic Resource
    Electronic Resource
    Nitrite Uptake Patterns in Wheat Seedlings as Influenced by Nitrate and Ammonium (1974)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 32 (1974), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Nitrite and nitrate uptake by wheat (Triticum vulgare) from 0.5 mM potassium solutions both showed an apparent induction pattern characterized by a slow initial rate followed by an accelerated rate. The accelerated phase was more rapid for nitrate uptake, was initiated earlier, and was seriously restricted by the presence of equimolar nitrite. The accelerated phase of nitrite uptake was restricted by nitrate to a lesser extent. The two anions seem not to be absorbed by identical mechanisms.Ammonium pretreatments or prior growth with ammonium had relatively little influence on the pattern of nitrite uptake. However, prior growth with nitrate eliminated the slow initial phase and induced development of the accelerated phase of nitrite uptake. A beneficial effect was noted after 3 h nitrate pretreatment and full development had occurred by 12 h nitrate pretreatment. The evidence suggests that a small amount of tissue nitrite, which could be supplied either by absorption or by nitrate reduction, was specifically required for induction of the accelerated phase of nitrite uptake.Cycloheximide (2 μg ml−1) seriously restricted development of the accelerated phase of nitrite uptake, but its effect was not as severe when it was added after the accelerated phase had been induced by prior exposure to nitrite or nitrate. However, translocation of 15N from the absorbed nitrite was sharply decreased under the latter conditions, indicating a difference in sensitivity of the uptake and translocation processes to cycloheximide.Potassium uptake was greater from KNO3 than from KNO2 and in both instances it was enhanced during the early stages of the accelerated phase of anion uptake. Moreover, addition of NaNO3 to KNO2 substantially increased potassium uptake. A coupling between anion and potassium uptake was therefore evident, but the coupling was not obligatory because the accelerated phase of nitrite uptake could occur in absence of rapid potassium uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1974.tb03736.x
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  • 8
    Electronic Resource
    Electronic Resource
    Nitrite Uptake by Nitrogen-Depleted Wheat Seedlings (1974)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 32 (1974), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Intact, 14-day-old nitrogen-depleted wheat (Triticum vulgare cv. Blueboy) seedlings were exposed to solutions of 0.5 mM KNO2, 0.05 mM CaSO4 and 1 mM sodium 2-[N-morpholino]-ethanesulfonate, pH 6.1. Nitrite uptake was determined from depletion of the ambient solution or from incorporation of 15N in the tissue. An initial nitrite uptake shoulder was followed by a relatively slow uptake rate which subsequently increased to a substantially greater rate. This accelerated phase was maintained through 24 h. Nitrite accumulated to a slight extent in the root tissues during the first few hours but declined to low values when the accelerated rate was fully developed, indicating an increase in nitrite reductase activity paralleling the increase in nitrite uptake capacity. About 50% of the nitrogen absorbed as nitrite was translocated to the shoots by 9–12 h.Development of the accelerated nitrite uptake rate was restricted in excised roots, in intact plants kept in darkness, by 400 μg puromycin ml−1 and by 1 mM L-ethionine. When puromycin and L-ethionine were added after the accelerated phase had been initiated, their effects were not as detrimental as when they were added at first exposure to KNO2. The two inhibitors restricted translocation more than uptake. The data indicate an involvement of protein synthesis and a requirement for movement of a substance from shoots to roots for maximal development of the accelerated nitrite uptake phase. A requirement for protein synthesis in the transport of soluble organic nitrogen from roots to shoots is also suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1974.tb03723.x
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  • 9
    Electronic Resource
    Electronic Resource
    Nitrate influx and efflux by intact wheat seedlings: Effects of prior nitrate nutrition (1976)
    Springer
    Planta 132 (1976), S. 149-156 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Wheat (Triticum vulgare L., cv. Blueboy) seedlings, grown with 0.25, 1.0 and 15 mM nitrate in complete nutrient solutions, were transferred 10 days after germination to 1.0 mM K15NO3 (∼99 A% 15N) plus 0.1 mM CaSO4 at pH 6.0. The solutions were replaced periodically over a 6-h period (5 mW cm-2; 23°). Changes in the [15N]- and [14N]nitrate in the solution were determined by nitrate reductase and mass-spectrometric procedures and potassium by flame photometry. Influx of [15N]nitrate was depressed in plants grown at 1.0 mM nitrate relative to those grown at 0.25 mM, but there was no appreciably difference in [14N]nitrate efflux. Prior growth at 15 mM further restricted [15N]nitrate influx which, together with a substantial increase in [14N]nitrate efflux, resulted in no net nitrate uptake during the course of the experiment. Efflux of [14N]nitrate occurred to solutions containing no nitrate but it was significantly enhanced upon exposure to [15N]nitrate in the external solution. Influx of [15N]nitrate was more restricted at 5°, relative to 23°, than was [14N]nitrate efflux. The nitrate concentrations of the root tissue immediately before exposure to the K15NO3 solutions did not give a precise indication of the subsequent [15N]nitrate influx rates nor of the [14N]nitrate efflux rates. Net K+ uptake was related to the magnitude of the net nitrate uptake, not to the initial K+ concentration in the roots. The data are interpreted as indicating that [15N]nitrate influx and [14N]nitrate efflux are largely independent processes, subject to different controls, and that net nitrate uptake provides the driving force for net potassium uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388896
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  • 10
    Electronic Resource
    Electronic Resource
    Partitioning of previously-accumulated nitrate to translocation, reduction, and efflux in corn roots (1983)
    Springer
    Planta 157 (1983), S. 8-14 
    Details
    ISSN: 1432-2048
    Keywords: Zea (NO 3 − partitioning) ; Nitrate translocation, reduction, efflux
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of nitrate uptake, or its absence, on the utilization of nitrate previously accumulated by dark-grown, decpitated maize (Zea mays L., cv. DeKalb XL-45) seedlings was examined. Five-d-old plants that had been pretreated with 50 mM 14NO 3 − for 20 h were exposed for 8 h to nutrient solutions containing either no nitrate or 50 mM 15NO 3 − , 98.7 atom % 15N. The ambient solution, xylem exudate, and plant tissue were analyzed to determine the quantities of previously-accumulated (endogenous) 14NO 3 − that were translocated to the xylem, lost to the solution, or reduced within the tissue during the 8-h period. Energy was continuously available to the roots from the attached endosperm. In the absence of incoming nitrate, appreciable reduction and translocation of the endogenous 14NO 3 − occurred, but efflux of 14NO 3 − to the external solution was minimal. In contrast, during 15NO 3 − uptake, there was considerable efflux of 14NO 3 − as well as translocation of 14NO 3 − to the xylem, but little 14NO 3 − was reduced. Thus there appeared to be an inverse relationship between 14NO 3 − efflux and reduction. The data are tentatively interpreted on the basis of a model which envisages (a) two storage locations within roots, one of which primarily supplies nitrate for translocation and the other of which primarily supplies nitrate for outward passage through plasmalemma, and (b) the majority of nitrate reduction as occurring during or immediately following influx across the plasmalemma, with endogenous 14NO 3 − initially moving outward being recycled inward and thereby being reduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394534
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