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  • Nitrate
  • Springer  (51)
  • Frontiers Media  (2)
  • American Chemical Society (ACS)
  • 2015-2019  (3)
  • 1990-1994  (50)
  • 1
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    Leaching losses from Kenyan maize cropland receiving different rates of nitrogen fertilizer (2017)
    Springer
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nutrient Cycling in Agroecosystems 108 (2017): 195–209, doi:10.1007/s10705-017-9852-z.
    Description: Meeting food security requirements in sub-Saharan Africa (SSA) will require increasing fertilizer use to improve crop yields, however excess fertilization can cause environmental and public health problems in surface and groundwater. Determining the threshold of reasonable fertilizer application in SSA requires an understanding of flow dynamics and nutrient transport in under-studied, tropical soils experiencing seasonal rainfall. We estimated leaching flux in Yala, Kenya on a maize field that received from 0 to 200 kg ha−1 of nitrogen (N) fertilizer. Soil pore water concentration measurements during two growing seasons were coupled with results from a numerical fluid flow model to calculate the daily flux of nitrate-nitrogen (NO3−-N). Modeled NO3−-N losses to below 200 cm for 1 year ranged from 40 kg N ha−1 year−1 in the 75 kg N ha−1 year−1 treatment to 81 kg N ha−1 year−1 in the 200 kg N ha−1 treatment. The highest soil pore water NO3−-N concentrations and NO3−-N leaching fluxes occurred on the highest N application plots, however there was a poor correlation between N application rate and NO3−-N leaching for the remaining N application rates. The drought in the second study year resulted in higher pore water NO3−-N concentrations, while NO3−-N leaching was disproportionately smaller than the decrease in precipitation. The lack of a strong correlation between NO3−-N leaching and N application rate, and a large decrease in flux between 120 and 200 cm suggest processes that influence NO3−-N retention in soils below 200 cm will ultimately control NO3−-N leaching at the watershed scale.
    Description: Earth Institute, Columbia University; National Science Foundation IIA-0968211; Bill and Melinda Gates Foundation
    Keywords: Leaching ; Nitrogen fertilizer ; Nitrate ; Numerical modeling ; Sub-Saharan Africa
    Repository Name: Woods Hole Open Access Server
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  • 2
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    Nitrogen limitation of the summer phytoplankton and heterotrophic prokaryote communities in the Chukchi Sea (2018)
    Frontiers Media
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Marine Science 5 (2018): 362, doi:10.3389/fmars.2018.00362.
    Description: Major changes to Arctic marine ecosystems have resulted in longer growing seasons with increased phytoplankton production over larger areas. In the Chukchi Sea, the high productivity fuels intense benthic denitrification creating a nitrogen (N) deficit that is transported through the Arctic to the Atlantic Ocean, where it likely fuels N fixation. Given the rapid pace of environmental change and the potentially globally significant N deficit, we conducted experiments aimed at understanding phytoplankton and microbial N utilization in the Chukchi Sea. Ship-board experiments tested the effect of nitrate (NO3-) additions on both phytoplankton and heterotrophic prokaryote abundance, community composition, photophysiology, carbon fixation and NO3- uptake rates. Results support the critical role of NO3- in limiting summer phytoplankton communities to small cells with low production rates. NO3- additions increased particulate concentrations, abundance of large diatoms, and rates of carbon fixation and NO3- uptake by cells 〉1 μm. Increases in the quantum yield and electron turnover rate of photosystem II in +NO3- treatments suggested that phytoplankton in the ambient dissolved N environment were N starved and unable to build new, or repair damaged, reaction centers. While some increases in heterotrophic prokaryote abundance and production were noted with NO3- amendments, phytoplankton competition or grazers likely dampened these responses. Trends toward a warmer more stratified Chukchi Sea will likely enhance summer oligotrophic conditions and further N starve Chukchi Sea phytoplankton communities.
    Description: Fieldwork and analysis for the ICESCAPE program was supported by Ocean Biology and Biogeochemistry Program of the National Aeronautic and Space Administration under Grant No. NNX10AF42G to KA.
    Keywords: Phytoplankton ; Nitrogen ; Chukchi Sea ; Nitrate ; Nutrient limitation
    Repository Name: Woods Hole Open Access Server
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  • 3
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    Intracellular isotope localization in Ammonia sp. (Foraminifera) of oxygen-depleted environments : results of nitrate and sulfate labeling experiments (2016)
    Frontiers Media
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Microbiology 7 (2016): 163, doi:10.3389/fmicb.2016.00163.
    Description: Some benthic foraminiferal species are reportedly capable of nitrate storage and denitrification, however, little is known about nitrate incorporation and subsequent utilization of nitrate within their cell. In this study, we investigated where and how much 15N or 34S were assimilated into foraminiferal cells or possible endobionts after incubation with isotopically labeled nitrate and sulfate in dysoxic or anoxic conditions. After 2 weeks of incubation, foraminiferal specimens were fixed and prepared for Transmission Electron Microscopy (TEM) and correlative nanometer-scale secondary ion mass spectrometry (NanoSIMS) analyses. TEM observations revealed that there were characteristic ultrastructural features typically near the cell periphery in the youngest two or three chambers of the foraminifera exposed to anoxic conditions. These structures, which are electron dense and ~200–500 nm in diameter and co-occurred with possible endobionts, were labeled with 15N originated from 15N-labeled nitrate under anoxia and were labeled with both 15N and 34S under dysoxia. The labeling with 15N was more apparent in specimens from the dysoxic incubation, suggesting higher foraminiferal activity or increased availability of the label during exposure to oxygen depletion than to anoxia. Our results suggest that the electron dense bodies in Ammonia sp. play a significant role in nitrate incorporation and/or subsequent nitrogen assimilation during exposure to dysoxic to anoxic conditions.
    Description: This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan (Young Scientists B No. 22740340 and Scientific Research C No. 24540504 to HN), an Invitation Fellowship for Research in Japan to JB by Japan Society for the Promotion of Science (JSPS), the Robert W. Morse Chair for Excellence in Oceanography at WHOI to JB, and The Investment in Science Fund at WHOI to JB.
    Keywords: Foraminifer ; Nitrate ; NanoSIMS ; Electron dense body ; Endobionts ; Ultrastructure ; Denitrification
    Repository Name: Woods Hole Open Access Server
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  • 4
    Electronic Resource
    Electronic Resource
    Photocatalytic oxidation of aqueous ammonia (ammonium ion) to nitrite or nitrate at TiO2 particles (1992)
    Springer
    Monatshefte für Chemie 123 (1992), S. 333-339 
    Details
    ISSN: 1434-4475
    Keywords: Ammonia ; Nitrate ; Oxidation ; Photocatalysis ; Titanium(IV) oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wurde die photokatalytische Oxidation von Ammoniak (Ammoniumion) mittels Luft oder reinem Sauerstoff an Titan(IV)oxid-Pulveroberflächen unter Induktion von UV-Licht untersucht. Die experimentellen Bedingungen wurden variiert, wobei der Effekt despH-Wertes, des Spülgases und sowohl die Ammoniak- als auch die Photokatalysator-Konzentration berücksichtigt wurde. Dabei ergab sich, daß das Hauptprodukt der photokatalytischen Oxidation vompH abhängt und entweder Nitrit oder Nitrat ist. Ein Gasdiffusions-Fließinjektions-Analysensystem wurde zur on-line-Kontrolle der Ammoniak-Konzentration verwendet. Off-line-Ionenchromatographie mit UV-Detektion wurde zur Konzentrationsbestimmung für Nitrit und Nitrat herangezogen. Die Verwendung von Photokatalysatoren wie Titanoxid könnte sich als gangbarer Weg erweisen, um Ammoniak (Ammoniumion) entweder zu Nitrit oder zu Nitrat umzusetzen.
    Notes: Summary The photocatalytic oxidation of ammonia (ammonium ion) in the presence of air or pure oxygen at titanium(IV) oxide powder surfaces and induced by UV light was investigated. Experimental conditions were varied and the effect ofpH, sparging gas, as well as the concentration of both ammonia (ammonium ion) and photocatalyst were investigated. It has been established that the principal product of photocatalytic oxidation depends onpH, and is either nitrite or nitrate. A gas-diffusion flow injection analysis system with conductivity detection was used for on-line monitoring of ammonia concentration. In addition, ion-chromatography with UV detection was utilized for offline monitoring of nitrite and nitrate concentrations. The use of a photocatalyst such as TiO2 may prove to be a viable method for conversion of ammonia (ammonium ion) to either nitrite or nitrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00810945
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  • 5
    Electronic Resource
    Electronic Resource
    Assimilation of mineral nitrogen and ion balance in the two partners of ectomycorrhizal symbiosis: Data and hypothesis (1991)
    Springer
    Cellular and molecular life sciences 47 (1991), S. 340-349 
    Details
    ISSN: 1420-9071
    Keywords: Nitrate ; ammonium ; nitrate reductase ; ion balance ; organic acids ; carbon metabolism ; ectomycorrhizal association ; woody plants ; ectomycorrhizal fungi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Assimilation pathways of mineral nitrogen and ion balances of the two partners of ectomycorrhizal symbiosis (fungi and woody plants) are reviewed. Data are presented about the partners both in pure culture and in mycorrhizal association. The two forms of mineral nitrogen, ammonium and nitrate, differ in their mobility in the soil, their transport into the cells, their uptake rates by plants and their assimilation pathways. These metabolic differences are related to differences in adjustment of ion balances and carbon metabolism under conditions of nitrate or ammonium nutrition. The data obtained on the partners of ectomycorrhizal symbiosis are discussed from this point of view and the observations composed with those on herbaceous angiosperms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01972075
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of ammonium and nitrate on the growth of vesicular-arbuscular mycorrhizalErythrina poeppigiana O.I. Cook seedlings (1994)
    Springer
    Biology and fertility of soils 18 (1994), S. 249-254 
    Details
    ISSN: 1432-0789
    Keywords: Ammonium ; Erythrina poeppigiana ; Nitrate ; Va mycorrhiza ; Nutrient uptake ; Glomus spp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Erythrina poeppigiana, a woody tropical plant, was inoculated with vesicular-arbuscular mycorrhizal (VAM) fungiGlomus etunicatum Becker and Gerdeman,G. mosseae Nicol. and Gerd. Gerdeman and Trappe, orG. intraradices Schenk and Smith. Growth, N uptake, and nutrition were evaluated in VAM-inoculated plants and controls fertilized with two levels (3 or 6 mM) of either NH inf4 sup+ -N or NO inf3 sup- -N. The response by the mycorrhizal plants to N fertilization, according to N source and/or level differed significantly from that of the control plants. In general, the growth of the mycorrhizal plants was similar to that of the non-mycorrhizal plants when N was provided as NH inf4 sup+ . When the N source was NO inf3 sup- the control plants grew significantly less than the VAM plants. Inoculation with VAM fungi gave yield increases of 255 and 268% forG. etunicatum-colonized plants, 201 and 164% forG. mosseae-colonized plants and 286 and 218% forG. intraradices-colonized plants fertilized with 3 and 6 mM NO inf3 sup- -N, respectively. The increased growth and acquisition of nutrients by plants fertilized with NO inf3 sup- -N and inoculated with VAM shows that VAM mycelium has a capacity for NO inf3 sup- absorption. The results also showed thatE. poeppigiana seedlings preferred NH inf4 sup+ as an N source.G. etunicatum was the most effective endophyte, not only increasing N, P, Ca, Mg, and Zn uptake in the presence of NO inf3 sup- fertilizer but also P and Mg in the presence of NH inf4 sup+ applications. From these results we conclude that VAM symbiosis affects N metabolism inE. poeppigiana plants and that this species can overcome limitations on the use of NO inf3 sup- -N by the mediation of VAM fungi.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647676
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  • 7
    Electronic Resource
    Electronic Resource
    Turnover of interlayer ammonium in loess-derived soil grown with winter wheat in the Shaanxi Province of China (1990)
    Springer
    Biology and fertility of soils 9 (1990), S. 211-214 
    Details
    ISSN: 1432-0789
    Keywords: Interlayer ammonium ; Nitrogen turnover ; Wheat ; Availability ; Urea ; Nitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The turnover of interlayer NH inf4 sup+ in a loess-derived agricultural soil from the Shaanxi Province in China was studied. The concentration of 15N-labeled interlayer NH inf4 sup+ and total interlayer NH inf4 sup+ (labeled + unlabeled) in a soil grown with winter wheat was significantly higher at the beginning of the season (March) than when the crop was mature (June). In a further experiment with winter wheat it was shown that under field conditions the concentration of interlayer NH inf4 sup+ decreased significantly in the two upper soil layers (0–20 and 20–55 cm) during March and in the deeper soil layer (55–75 cm) during April. When the heading stage of wheat was reached, about 200 kg N ha-1 of interlayer NH inf4 sup+ had been released. During the following growth period (heading until flowering of wheat) the concentration of interlayer NH inf4 sup+ increased significantly in the upper soil layers. Fertilizer application in the form of 70 kg N ha-1 as urea led to a considerable increase in the nitrate concentration in the upper soil layer but had no influence on the level of interlayer NH inf4 sup+ concentration. It is concluded that interlayer NH inf4 sup+ takes part in the N cycle of the soil and that it contributes to the N nutrition of the crop. NH inf4 sup+ originating from the mineralization of soil organic N may be rapidly incorporated into the interlayer of clay minerals and later released, when the N demand of the crop is high.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336227
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  • 8
    Electronic Resource
    Electronic Resource
    Nitrate reduction and nitrate content in ash trees (Fraxinus excelsior L.): distribution between compartments, site comparison and seasonal variation (1992)
    Springer
    Trees 6 (1992), S. 236-240 
    Details
    ISSN: 1432-2285
    Keywords: Fraxinus excelsior L. ; Compartments ; Nitrate reductase ; Nitrate ; Seasonal variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrate reductase activity (NRA), nitrate content and biomass components of leaflets, leaf stalks, old stem, current-year stem and roots of ash trees (Fraxinus excelsior L.) growing in their natural habitats were investigated. In addition, NRA, total nitrogen and nitrate concentration were analyzed in the leaves and roots of ash trees from four different field sites. The highest NRA per gram biomass and also per total compartment biomass was found in the leaflets, even though root biomass was much higher than total leaflet biomass. The highest nitrate concentrations were found in the leaf stalks. Correlations between nitrate availability in the soil and NRA in leaves were not significant due to high variability of the actual soil nitrate concentrations. The seasonal variation in foliar NRA, nitrate concentration and total nitrogen concentration is much smaller in F. excelsior than reported for herbaceous species and is mainly caused by changes in the actual soil nitrate availability and by senescence of the leaves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224342
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  • 9
    Electronic Resource
    Electronic Resource
    Foliar and fine root nitrate reductase activity in seedlings of four forest tree species in relation to nitrogen availability (1993)
    Springer
    Trees 7 (1993), S. 233-236 
    Details
    ISSN: 1432-2285
    Keywords: Nitrate reductase ; Nitrogen deposition ; Forests ; Nitrate ; Seedlings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Seedlings of red maple, white pine, pitch pine and red pine were fertilized with nutrient solutions containing 4 levels of nitrate or ammonium additions. These levels corresponded to approximately 0.5, 1, 2 and 4 times normal availability of nitrogen in northeastern forests. Nitrate reductase (NR) activity was assayed in roots and leaves. Red maples treated with nitrate showed much higher leaf activities and higher ratios of leaf NR activity to root NR activity than any other species. Ammonium additions to red maple and white pine appeared to inhibit NR activity in leaves. With high nitrate additions, NR activity was induced in roots and leaves of pine species, but activity in roots remained much higher than in leaves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202079
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  • 10
    Electronic Resource
    Electronic Resource
    A contribution to understanding the internal nitrogen budget of beech (Fagus sylvatica L.) (1993)
    Springer
    Trees 7 (1993), S. 237-241 
    Details
    ISSN: 1432-2285
    Keywords: Fagus sylvatica ; Nitrate ; Total nitrogen content ; Trunk height gradient ; Seasonal variation ; Xylem sap
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The seasonal variation in the total nitrogen content of the xylem sap of the lower trunk section was investigated for two middle aged beech tree stands in northern Hessen each containing 130 trees. In addition seasonal changes in the percentage of nitrate in the total nitrogen content are described. The median values of the total nitrogen content of the xylem sap during the spring mobilization period reached 175 and 250 mg/l. During the summer about 35% of the total nitrogen in the xylem sap is in the form of nitrate. Finally, the distribution of NO3 in the xylem sap along the trunk height was studied for two sample trees for each of the four seasons (n = 8).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202080
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  • 11
    Electronic Resource
    Electronic Resource
    Nitrate in groundwater and N circulation in eastern Botswana (1994)
    Springer
    Environmental geology 23 (1994), S. 60-64 
    Details
    ISSN: 1432-0495
    Keywords: Groundwater ; Nitrate ; Latrines ; Nitrogen cycling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Nitrate pollution due to deep leaching from pit latrines has caused water supply wells in eastern Botswana to exceed health limits concerning nitrate. It was deduced from the estimated intake of salt and protein by the population that, as an average, about 10 percent of the human nitrogen excretion is leached to the groundwater. This fraction was also found in southern India, where on-the-ground excretion is customary. The nitrogen circulation in general in the savanna ecosystem is not appreciably affected in spite of a large livestock density. Overall nitrate leaching is in the order of 1.5 kg N/ha/y, similar to that in another semiarid area in southern India. However, in India, there seems to be a more diffuse areal leaching from agriculture as well as from villages. Measures to minimize the nitrate leaching could be to plant deep-rooted trees adjacent to pit latrines or to use latrines that separate the urine from the faces for a more near-surface infiltration facilitating plant uptake. Measures to minimize leaching will also lessen the rick for bacterial pollution of the groundwater.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00773140
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  • 12
    Electronic Resource
    Electronic Resource
    Potential nitrate pollution of groundwater in Germany: A supraregional differentiated model (1994)
    Springer
    Environmental geology 24 (1994), S. 1-6 
    Details
    ISSN: 1432-0495
    Keywords: Nitrate ; Groundwater ; Modeling ; Denitrification ; Nitrogen balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Implemented on behalf of the Federal Ministry for Research and Technology (BMFT), a model is developed to trace the nutrient flow of nitrate in the soil and the groundwater on a supraregional scale. Research work is intended to indicate regionally differentiated hazardous potentials and thereby provide a basis for recommending comprehensive measures to protect groundwater in Germany. The adaption of the model to the hydrogeological and agricultural conditions of other states is possible in principle. This article focuses on the hydrogeological model parts. A high nitrate pollution of groundwater can be expected in all regions with intensive agricultural use of the topsoil. In particular, groundwater in solid rock areas is susceptible to nitrate pollution. There a rapid groundwater turnover and thus a short residence time for the groundwater in the aquifer is typical. Oxidizing aquifer conditions usually prevail in solid rock aquifers, preventing nitrate degradation. In many loose rock areas, in contrast, the groundwater has a low flow velocity and a long residence time in the aquifer. Because of a lack of free oxygen, a complete degradation of nitrate can occur, as long as iron sulfide compounds and/or organic carbon are available in the aquifer. A more detailed presentation of the whole research work is given in Wendland et al. (1993).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00768070
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  • 13
    Electronic Resource
    Electronic Resource
    Coaction of light, nitrate and a plastidic factor in controlling nitrite-reductase gene expression in tobacco (1992)
    Springer
    Planta 187 (1992), S. 381-387 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Nitrate ; Nitrate reductase (control) ; Phytochrome ; Nicotiana (nitrite reductase gene expression)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrite reductase (NIR; EC 1.7.7.1) — a key enzyme of nitrate reduction — is known to be induced by nitrate and light. In the present study with tobacco (Nicotiana tabacum L.) seedlings the dependency of NIR gene expression on nitrate, light and a plastidic factor was investigated to establish the nature of the coaction between these controlling factors. A cDNA clone coding for tobacco plastidic NIR was available as a probe. The major results were as follows: (i) The light effect on the appearance of NIR occurred predominantly through phytochrome. However, a specific blue-light effect was also involved. (ii) There was no effect of light on NIR appearance in the absence of nitrate while light exerted a strong effect when nitrate was provided. (iii) Anion-exchange chromatography revealed only a single form of NIR. While experiments involving plastid photooxidation indicated that this NIR is plastidic, a small residual level could not be eliminated by photooxidation. (iv) Northern blot analysis of NIR-transcript levels indicated that a low transcript level existed in the absence of nitrate and light; however, this level appeared to be increased slightly by light (in the absence of nitrate) and by nitrate (in the absence of light). A high transcript level was detected only when light as well as nitrate were provided. A low level was found when the plastids were damaged by photooxidation. It is concluded that plastidic NIR gene expression in tobacco requires positive control by a plastidic factor. Moreover, a synergistic action of phytochrome and nitrate is required to bring about a high transcript level. As found previously with mustard and spinach seedlings, there is no quantitative relationship between the transcript level and the rate of enzyme synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195662
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  • 14
    Electronic Resource
    Electronic Resource
    Respiration and nitrogen fixation of hydroponically cultured Phaseolus vulgaris L. cv. OAC Rico and a supernodulating mutant (1993)
    Springer
    Planta 189 (1993), S. 538-545 
    Details
    ISSN: 1432-2048
    Keywords: Carbohydrate and nitrogen distribution ; Nitrate ; Nitrogenase activity ; Nitrogen fixation ; Respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study was undertaken to determine how carbon utilization of fruit production might affect symbiotic activity in hydroponically cultured white bean (Phaseolus vulgaris L.) cv. Rico and its supernodulating genotype R32-BS15 (abbreviated as RBS15). Total plant biomass production of both genotypes was similar. Nodule dry weight of RBS15 consistently scored approximately twice the amount recorded for Rico, while nodule numbers in the mutant were almost six times as high. Nodule respiration on a per-plant basis and specific respiration was initially (day 37) disproportionally higher in the mutant, reaching up to three times the values recorded for Rico, while plant N2 fixation estimated by 15N dilution was almost identical. This indicates a lower fixation efficiency of RBS15 nodules, which we suggest to be a result of the larger number of smaller nodules with a higher proportion of growth and maintenance respiration per unit nodule mass. During reproductive development, specific respiration of the mutant dropped below that of Rico without a reduction in fixation, indicating a change in relative efficiency of fixation. Continuous removal of fruits from day 37 onwards stimulated respiration of nodules in both genotypes with highest values per plant being documented for RBS15, while specific activity was higher for Rico. The results indicate that symbiotic activity was not detrimentally affected by competition for carbohydrates between fruits and nodules. It appeared that nodules did not possess excess N2-fixation capacity which could be stimulated by additional provision of photosynthate. Hence, the early onset of reproduction during the life cycle of P. vulgaris is unlikely to be responsible for inadequate fixation performance in the field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198217
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  • 15
    Electronic Resource
    Electronic Resource
    Response of a nitrite-reductase 3.1-kilobase upstream regulatory sequence from spinach to nitrate and light in transgenic tobacco (1993)
    Springer
    Planta 189 (1993), S. 440-442 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Nitrate ; Nitrite reductase ; Phytochrome ; Transgenic tobacco ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the present study the question was addressed of whether the nitrite-reductase (NIR-)promoter from spinach (Spinacia oleracea L.), fused to a reporter gene (bacterial β-glucuronidase, GUS) and introduced into tobacco (Nicotiana tabacum L.) responds to nitrate and light in accordance with spinach (donor) or in accordance with tobacco (host). The data obtained at the GUS enzyme level as well as at the transcript level allow an unambiguous answer to this question: GUS gene expression under the control of the NIR-promoter from spinach responds to nitrate and light in accordance with the host (tobacco). Expression of the promoter-less GUS gene was not induced by any treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194443
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  • 16
    Electronic Resource
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    Deletion analysis of a nitrite-reductase promoter from spinach in transgenic tobacco (1994)
    Springer
    Planta 194 (1994), S. 186-192 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Nitrate ; Nitrite-reductase ; Phytochrome ; Transgenic tobacco ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Deletion analysis of the nitrite-reductase (NiR) promoter from spinach (Spinacia oleracea L.) fused to theβ-glucuronidase (GUS) reporter gene and introduced into tobacco (Nicotiana tabacum L., cv. Coker 176) indicates that basic elements required for light- and nitrate-dependent expression of the reporter are located within the promoter sequence -200/+131 relative to the transcription-initiation site. Detailed analysis indicates that positive regulatory elements exist between -200 and-330 as well as between -1450 and -1730, stimulating the level of GUS gene expression under all experimental conditions. Induction/reversion light-pulse experiments show that the promoter sequence -200/+131 suffices for phytochrome-mediated expression of the reporter gene. The observation that the NiR promoter from spinach exhibits full reversibility in transgenic tobacco confirms the previous conclusion that the NiR promoter from spinach fused to a GUS reporter gene and introduced into tobacco responds to nitrate and phytochrome as would be expected for tobacco (host) and not as would be expected for spinach (donor). When the plastids were damaged by photooxidation in the presence of Norflurazon, GUS activity levels were reduced to the same extent for all NiR-promoter/GUS fusions tested, indicating that the promoter region involved in the action of the ‘plastidic factor’ is between -200 and +131. The GUS gene expression under the control of the CaMV-35S promoter is not affected by light, nitrate or the ‘plastidic factor’.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01101677
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    Regulation of transcript level and synthesis of nitrate reductase by phytochrome and nitrate in turions of Spirodela polyrhiza (L.) Schleiden (1992)
    Springer
    Planta 188 (1992), S. 587-593 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Nitrate ; Nitrate reductase ; Phytochrome ; Spirodela ; Turion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Control by light and nitrate of the appearance of nitrate reductase (NR; EC 1.6.6.1) in the turions of Spirodela polyrhiza (L.) Schieiden was investigated during the pre-germination phase, i.e. up to 120 h after the transfer from after-ripening to germination conditions. Turions are particularily suited for this type of coaction study since control of nitrate uptake by light and long-distance transport of nitrate do not play a role. Control of NR gene expression was mainly studied between 72 and 120 h after transfer to germination conditions (phase II of the pre-germination process). It was found that the effect of light on NR appearance is exerted via phytochrome. The light effect on enzyme synthesis was only observed in the presence of nitrate. On the other hand, in darkness, the NR level decreased to almost zero even in the presence of an optimum supply of nitrate. It is concluded that in phase II a coaction of light (phytochrome) and nitrate is required to bring about NR synthesis. However, when nitrate was applied to turions — following a dark incubation without nitrate — the turions responded to nitrate even in darkness with strong NR synthesis. This response was augmented by light. The highest transcript levels were observed in the presence of both factors, light and nitrate. As a single factor, light was more effective in stimulating the transcript level than nitrate. However, no correlation between the transcript level and the rate of enzyme synthesis was observed. This is consistent with the previous conclusion (Schuster et al. 1988, Planta 174, 426–432) that in higher plants control at the transcript level is only coarse and does not determine quantitatively the output at the level of enzyme protein.
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    Deletion analysis of a nitrite-reductase promoter from spinach in transgenic tobacco (1994)
    Springer
    Planta 194 (1994), S. 186-192 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Nitrate ; Nitrite-reductase ; Phytochrome ; Transgenic tobacco ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Deletion analysis of the nitrite-reductase (NiR) promoter from spinach (Spinacia oleracea L.) fused to the β-glucuronidase (GUS) reporter gene and introduced into tobacco (Nicotiana tabacum L., cv. Coker 176) indicates that basic elements required for light- and nitrate-dependent expression of the reporter are located within the promoter sequence -200/+131 relative to the transcription-initiation site. Detailed analysis indicates that positive regulatory elements exist between -200 and-330 as well as between -1450 and -1730, stimulating the level of GUS gene expression under all experimental conditions. Induction/reversion light-pulse experiments show that the promoter sequence -200/+131 suffices for phytochrome-mediated expression of the reporter gene. The observation that the NiR promoter from spinach exhibits full reversibility in transgenic tobacco confirms the previous conclusion that the NiR promoter from spinach fused to a GUS reporter gene and introduced into tobacco responds to nitrate and phytochrome as would be expected for tobacco (host) and not as would be expected for spinach (donor). When the plastids were damaged by photooxidation in the presence of Norflurazon, GUS activity levels were reduced to the same extent for all NiR-promoter/GUS fusions tested, indicating that the promoter region involved in the action of the ‘plastidic factor’ is between -200 and +131. The GUS gene expression under the control of the CaMV-35S promoter is not affected by light, nitrate or the ‘plastidic factor’.
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    Expression of glutamine synthetase during the anaerobic germination of Oryza sativa L. (1994)
    Springer
    Planta 195 (1994), S. 147-149 
    Details
    ISSN: 1432-2048
    Keywords: Anoxia ; Coleoptile ; Glutamine synthetase (isoenzymes) ; Nitrate ; Oryza
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Glutamine synthetase (GS; EC.6.3.1.2.) occurs as cytosolic (GS1) and plastidic (GS2) polypeptides. This paper describes the expression of GS isoenzymes in coleoptile during the anaerobic germination of rice (Oryza sativa L.) and the influence of exogenous nitrate on this. By immunoprecipitation with anti-GS serum, two polypeptides of 41- and 44-kDa were detected of which the former was predominant. After fractionation by ion-exchange chromatography, the 41 and 44 kDa bands were identified as GS1 and GS2, respectively. Northern blot analysis with specific probes showed the presence of mRNA for cytosolic GS but not for the plastidic form. The presence of exogenous nitrate did not alter the activity and expression of GS in the coleoptile. The role of GS during the anaerobic germination of rice seems to induce the re-assimilation of ammonia rather than the assimilation of nitrate.
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    URL: http://dx.doi.org/10.1007/BF00206303
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    Ammonium and nitrate as nitrogen sources in two Eriophorum species (1991)
    Springer
    Oecologia 88 (1991), S. 570-573 
    Details
    ISSN: 1432-1939
    Keywords: Eriophorum scheuchzeri ; Eriophorum vaginatum ; Ammonium ; Nitrate ; Absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We compared ammonium and nitrate nutrition in Eriophorum scheuchzeri and E. vaginatum, two Alaskan sedges that are native to high- and low-fertility sites, respectively. When grown in solution culture, the two species were similar in their kinetics of NH inf4 sup+ NO inf3 sup- absorption: at nitrogen concentrations below 50 μM, net NH inf4 sup+ and NO inf3 sup- were absorbed at similar rates, but at higher concentrations, net uptake of NO inf3 sup- was significantly faster than that of NH inf4 sup+ . The two species also showed similar abilities to assimilate NO inf3 sup- . Growth of E. vaginatum under NO inf3 sup- nutrition was only slightly less than that under NH inf4 sup+ . The observed similarities between these species from contrasting edaphic habitats indicate that factors other than tissue-specific rates of nitrogen acquisition and assimilation may underlie local adaptation to soil N fertility. Moreover, the capacity of these species to exploit NO inf3 sup- as a N source supports the view that NO inf3 sup- availability may be significant even in wet, acidic, arctic soils.
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    URL: http://dx.doi.org/10.1007/BF00317721
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    The ability of several high arctic plant species to utilize nitrate nitrogen under field conditions (1993)
    Springer
    Oecologia 96 (1993), S. 239-245 
    Details
    ISSN: 1432-1939
    Keywords: Arctic plants ; Ammonium ; Nitrate ; Nitrate reductase ; 15N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ability to utilize NO inf3 sup− in seven high arctic plant species from Truelove Lowland, Devon Island, Canada was investigated, using an in vivo assay of maximum potential nitrate reductase (NR) activity and applications of 15N. Plant species were selected on the basis of being characteristic of nutrient-poor and nutrient-rich habitats. In all species leaves were the dominant site of NR activity. Root NR activity was negligible in all species except Saxifraga cernua. NO inf3 sup− availability per se did not appear to limit NR activity of the species typically found on nutrient-poor sites (Dryas integrifolia, Saxifraga oppositifolia, and Salix arctica), or in Cerastium alpinum, as leaf NR activities remained low, even after NO inf3 sup− addition. 15NO inf3 sup− uptake was limited in D. integrifolia and Salix arctica. However, the lack of field induction of NR activity in C. alpinum and Saxifraga oppositifolia was not due to restricted nitrate uptake, as 15NO inf3 sup− labelled NO inf3 sup− entered the roots and shoots of both species. Leaf NR activity rates were low in three of the species typical of nutrient-rich habitats (O. digyna, P. radicatum and Saxifraga cernua), sampled from a site containing low soil NO inf3 sup− . Additions of NO inf3 sup− significantly increased leaf NR activity in these latter species, suggesting that potential NR activity was limited by the availability of NO inf3 sup− . 15N labelled NO inf3 sup− was taken up by O. digyna. P. radicatum and Saxifraga cernua. Although two species (D. integrifolia and Salix arctica) showed little utilization of NO inf3 sup− , we concluded that five of the seven selected high arctic plant species (C. alpinum, O. digyna, P. radicatum, Saxifraga cernua and Saxifraga oppositifolia) do have the potential to utilize NO inf3 sup− as a nitrogen source under field conditions, with the highest potential to utilize NO inf3 sup− occurring in three of the species typically found on fertile habitats.
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    URL: http://dx.doi.org/10.1007/BF00317737
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    Nitrate assimilation in coexisting vascular plants in mire and swamp forest habitats in Central Sweden (1991)
    Springer
    Oecologia 87 (1991), S. 495-499 
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    ISSN: 1432-1939
    Keywords: Assimilation ; Coexisting ; Mire ; Nitrate ; Swamp forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In order to monitor the nitrate assimilation capability of mire plants, in vivo current and maximally induced nitrate reductase activity (NRA) were investigated in 14 species of vascular plants from four different sites in a central Swedish mire. One of the sites was a swamp forest. The plants studied included species with both wide and restricted ecological ranges, and the mire sites selected covered a wide range of plant productivity. At the most productive site, current NRA differed among coexisting species. This differentiation in the use of nitrate as a source of nitrogen suggested the possibility of resource partitioning with regard to nitrogen acquisition. Maximally induced NRA, measured 3 days after an addition of nitrate, was highest at the most productive sites and differed among coexisting species. Plant species characteristic of rich fens had the highest maximally induced NRA. In all species, there was a positive correlation between the ability to assimilate peaks of available nitrate and total leaf nitrogen concentration.
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    Nitrate nutrition ofDeschampsia flexuosa (L.) Trin. in relation to nitrogen deposition in Sweden (1991)
    Springer
    Oecologia 87 (1991), S. 488-494 
    Details
    ISSN: 1432-1939
    Keywords: Deschampsia flexuosa ; Nitrate ; Nitrate reductase ; Nitrogen deposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Current and maximally induced nitrate reductase activity (NRA), total-N, nitrate, K, P, Ca, Mg, Mo and sucrose in leaves ofDeschampsia flexuosa was measured three times during the vegetation period in forests along a deposition gradient (150 km) in south Sweden, in north Sweden where the nitrogen deposition is considerably lower, and at heavily N-fertilized plots. In addition, the interaction between nitrogen nutrition and light was studied along transects from clearings into forest in both south and north Sweden. Plants from sites with high nitrogen deposition had elevated current NRA compared to plants from less polluted sites, indicating high levels of available soil nitrate at the former. Current NRA and total N concentration in grass from sites with high deposition resembled those found at heavily N-fertilized plots. Under such circumstances, the ratio current NRA: maximally induced NRA as well as the concentration of nitrate was high, while the concentration of sucrose was low. This suggests that the grass at these sites was already utilizing a large portion of its capacity to assimilate nitrate. Light was found to play an important role in the assimilation of nitrate; leaf concentration of sucrose was found to be negatively correlated with both nitrate and total N. Consequently, grass growing under dense canopies in south Sweden is not able to dilute N by increasing growth. The diminished capacity of the grass to assimilate nitrate will increase leaching losses of N from forests approaching N saturation.
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    Effects of fire and harvesting on nitrogen transformations and ionic mobility in soils of Eucalyptus regnans forests of south-eastern Australia (1990)
    Springer
    Oecologia 83 (1990), S. 20-26 
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    ISSN: 1432-1939
    Keywords: Immobilization ; Fire ; Leaching ; Nitrate ; Eucalyptus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Effects of fire and forest harvesting on inorganic-N in the soil, on net N-mineralization, and on the leaching of NO inf3 sup- -N and metallic cations were measured in forests of Eucalyptus regnans following a severe wildfire in 1983. E. regnans regenerates profusely by seed after fire, and this study compared unburnt forest with forests burnt at varying intensities (surface fire and crown fire), and with logged and burnt forest (slash fire). Total inorganic-N in soil (0–5 cm) increased with increasing fire intensity to a maximum of 158 μg g-1 in the slash fire plot (compared with 51 μg g-1 in the unburnt forest) over the first 205 days after fire. Total inorganic-N returned to a concentration equal to that in the unburnt forest after 485 days at the slash fire plot, and after only 205 days at the surface fire plot. Studies of net mineralization in situ and of NO inf3 sup- -N in soil solution support the hypothesis that inorganic-N was immobilized in all of the burnt forests; microbial immobilization after fire is identified as a key process in N-conservation, limiting the substrate available for nitrification and thereby limiting the loss of N from the system by leaching. The concentrations of NO inf3 sup- -N and metallic cations in soil solution increased with increasing fire intensity. For the first 318 days after the fire, [NO inf3 sup- -N] in soil solution at 10 cm averaged 0.6 μg ml-1 in the unburnt forest, 9.7 mg l-1 in the surface fire plot, 26 mg l-1 in the crown fire plot, and 70 mg l-1 in the slash fire plot. The concentration of metallic cations in soil solution was significantly correlated with [NO inf3 sup- -N], the observed order of mobility being Ca2+〉Mg2+〉K+〉Na+. Processes which limit the production and persistence of NO inf3 sup- -N in soil solution following disturbance will significantly reduce nutrient losses or redistribution.
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    Die Beziehung zwischen Pharmakokinetik und hämodynamischer Toleranz gegenüber isosorbid-5-Mononitrat (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. S151 
    Details
    ISSN: 1432-1041
    Keywords: Nitrate ; Pharmakokinetik ; Pharmakodynamik ; Nitrattoleranz ; Isosorbid-5-Mononitrat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Zusammenfassung Gesunde männliche Probanden erhielten Isosorbid-5-Mononitrat in einer Darreichungsform mit verzögerter Freisetzung (IS-5-MN; 60 mg pro Tablette) nach drei unterschiedlichen Dosierungsschemata. Dosierungsschema I bestand aus einer Einzeldosis von täglich 60 mg über eine Dauer von 5 Tagen. Dosierungsschema II begann mit einer Dosis von 60 mg, gefolgt von einer Dosis zu 30 mg 12 Std später und danach alle 8 Std. Die letzte Dosis, gegeben am fünften Tage, betrug wiederum 60 mg. Bei Dosierungsschema III folgte auf zunächst 60 mg jeweils 6 Std später eine Gabe von 30 mg. Diese Dosis wurde über eine Dauer von 5 Tagen täglich gegeben. Die peripheren arteriellen und venösen Wirkungen von IS-5-MN wurden während des ersten und des letzten Dosierungsintervalls anhand von Änderungen der Fingerpulskurve, des systolischen Blutdrucks im Stehen, der Herzfrequenz und der venösen Kapazität bestimmt. Die Plasmakonzentrationen von IS-5-MN wurden nach Verabreichung der ersten und der letzten Dosis mehrfach gemessen. Bei der nach Dosierungsschema I durchgeführten Behandlung blieben alle hämodynamischen Effekte, die durch die erste Dosis hervorgerufen worden waren, während der gesamten Studiendauer erhalten. Die maximale Plasmakonzentration betrug 400 ng/ml. Die minimalen Plasmaspiegel lagen unterhalb 100 ng/ml. Bei Dosierungsschema II war die hämodynamische Wirksamkeit von IS-5-MN oder sublingual gegebenem Glyzeroltrinitrat am fünften Behandlungstage vollständig aufgehoben. Die minimalen Plasmakonzentrationen betrugen während der gesamten Studienperiode ungefähr 300 ng/ml. Bei Dosierungsschema III wurden am ersten Tage deutliche hämodynamische Effekte gemessen. Jedoch wurde am fünften Tage eine signifikante Abschwächung dieser Effekte festgestellt, wobei die minimalen Plasmakonzentrationen zwischen 100 und 230 ng/ml lagen. Das Ausmaß der am fünften Tage verbliebenen hämodynamischen Wirkung (gemessen als Fläche unter der Fingerpulskurve) zeigte eine negative Korrelation mit der gemessenen minimalen Plasmakonzentration. Die Aufrechterhaltung von Plasmakonzentrationen von IS-5-MN von mindestens 300 ng/ml führt somit zu einer schnellen Entwicklung einer hämodynamischen Nitrat-Toleranz. Demgegenüber wurde keine Toleranz gesehen, wenn die minimalen Plasmakonzentrationen unter 100 ng/ml absinken konnten. Lagen die minimalen Plasmakonzentrationen zwischen 100 und 230 ng/ml, wurde eine signifikante Verminderung der hämodynamischen Effekte festgestellt. In diesem Konzentrationsbereich stieg das Ausmaß der Wirkungsabschwächung mit ansteigender minimaler Plasmakonzentration von IS-5-MN an.
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    Nitrate: Warum und wie sie heute eingesetzt werden sollten (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. S133 
    Details
    ISSN: 1432-1041
    Keywords: Nitrate ; Nitroglyzerin ; Isosorbid-Dinitrat ; Isosorbid-5-Mononitrat ; Angina pectoris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Zusammenfassung Akute Angina pectoris-Anfälle können durch den Einsatz von Nitraten schnell und wirksam beendet werden. Aber auch in der Prophylaxe bei symptomatischen und asymplomatischen Myokardischämien sind Nitrate überaus effektiv. Bei Patienten mit chronischer stabiler Angina besteht der entscheidende Wirkungsmechanismus der Nitrate in einer Herabsetzung der Vorlast und unterscheidet sich in diesem von Beta-Blokkern oder Kalziumantagonisten. Hierbei werden die Koronararterien nicht nur prä- und poststenotisch, sondern auch in exzentrischen Stenosen erweitert. Bei Patienten mit Endotheldysfunktion scheinen die Nitrate den endothelium-derived relaxing factor physiologisch zu substituieren. Während der letzten Dekade hat es jedoch deutliche Hinweise auf einen klinisch relevanten Verlust der antiischämischen Effekte (≪Nitrattoleranz≫) gegeben. Viele Studien, in denen Isosorbid-Dinitrat oder Isosorbid-5-Mononitrat mindestens dreimal täglich oral gegeben wurde, haben bei Patienten mit Koronararterienerkrankung und/oder Herzinsuffizienz eine Nitrattoleranz zeigen können. Der vollständige Verlust der antiischämischen Wirksamkeit wurde auch nach wiederholter und dauerhafter Pflasteranwendung beschrieben. 1983 haben wir erstmalig gezeigt, daß eine intermittierende Therapie mit einer einmal täglichen Einnahme einer hohen Dosis Isosorbid-Dinitrat mit langsamer Freisetzung erfolgreich eine Toleranzentwicklung verhindern konnte. In gleicher Weise zeigte sich auch keine Toleranz gegenüber Isosorbid-5-Mononitrat bei einmal täglicher Einnahme. Es wird inzwischen allgemein akzeptiert, daß zur Vermeidung einer Toleranzentwicklung ein gewisser Zeitraum mit täglich niedrigen Nitratplasmaspiegeln erforderlich ist. Die minimale Dauer eines pflasterfreien Zeitraums, die zur Vermeidung einer Toleranz erforderlich ist, muß im einzelnen noch untersucht werden. Man kann aber davon ausgehen, daß bei den meisten Patienten hierzu ein Zeitraum von 12 Std ausreicht. Eine einmal tägliche anzuwendende, hohe Dosierung von Isosorbid-Dinitrat oder Isosorbid-5-Mononitrat mit verzögerter Freisetzung besitzt eine verlängerte Wirkungsdauer und vergrößert die Wahrscheinlichkeit einer antiischämischen Wirksamkeit. Hinzu kommt eine verbesserte Patientenmitarbeit bei einer einmal täglichen Dosierung. Diese wichtigen Gründe sprechen dafür, die Anwendung von hochdosierten Nitraten einmal täglich zu empfehlen.
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    Importance of organic nitrogen fractions in sandy soils, obtained by electro-ultrafiltration or CaCl2 extraction, for nitrogen mineralization and nitrogen uptake of rape (1990)
    Springer
    Biology and fertility of soils 10 (1990), S. 97-101 
    Details
    ISSN: 1432-0789
    Keywords: Nitrogen mineralization ; Sandy soils ; Organic-bound nitrogen ; electro-ultrafiltration method CaCl2 method ; Ammonium ; Nitrate ; N uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Sandy soils have low reserves of mineral N in spring. Therefore organic-bound N is the most important pool available for crops. The objective of the present investigation was to study the importance of the organic-bound N extracted by electro-ultrafiltration and by a CaCl2 solution for the supply of N to rape and for N mineralization. Mitscherlich-pot experiments carried out with 12 different sandy soils (Germany) showed a highly significant correlation between the organic N extracted (two fractions) and the N uptake by the rape (electroultrafiltration extract: r=0.76***; CaCl2 extract: r=0.76***). Organic N extracted by both methods before the application of N fertilizer was also significantly correlated with N mineralization (electro-ultrafiltration extract: r=0.75***; CaCl2 extract: r=0.79***). N uptake by the rape and the mineralization of organic N increased with soil pH and decreased with an increasing C:N ratio and an increasing proportion of sand in the soils. Ninety-eight percent of the variation in N uptake by the rape was determined by the differences in net mineralization of organic N. This show that in sandy soils with low mineral N reserves (NO inf3 sup- -N, NH 4 + -N) the organic soil N extracted by electro-ultrafiltration or CaCl2 solutions indicates the variance in plant-available N. Total soil N was not related to the N uptake by plants nor to N mineralization.
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    Influence of pH on the release of NO and N2O from fertilized and unfertilized soil (1990)
    Springer
    Biology and fertility of soils 10 (1990), S. 139-144 
    Details
    ISSN: 1432-0789
    Keywords: Denitrification ; Nitrification ; Chemodenitrification ; Ammonium ; Nitrite ; Nitrate ; Nitric oxide ; Nitrous oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary NO and N2O release rates were measured in an acidic forest soil (pH 4.0) and a slightly alkaline agricultural soil (pH 7.8) after the pH was adjusted to values ranging from pH 4.0 to 7.8. The total release of NO and N2O during 20 h of incubation was determined together with the net changes in the concentrations of NH 4 + , NO 2 − and NO 3 − in the soil. The release of NO and N2O increased after fertilization with NH 4 + and/or NO 3 − ; it strongly decreased with increasing pH in the acidic forest soil; and it increased when the pH of the alkaline agricultural soil was decreased to pH 6.5. However, there was no simple correlation between NO and N2O release or between these compounds and activities such as the NO 2 − accumulation, NO 3 − reduction, or NH 4 + oxidation. We suggest that soil pH exerts complex controls, e.g., on microbial populations or enzyme activities involved in nitrification and denitrification.
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    Determination of N in lignin together with nitrite or nitrate (1990)
    Springer
    Biology and fertility of soils 10 (1990), S. 218-220 
    Details
    ISSN: 1432-0789
    Keywords: Total N determination ; Lignin ; Nitrate ; Nitrite ; Kjeldahl method ; Auto-analyzer ; Persulphate analysis ; Dymock/Devarda method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Various methods were used to determine N in lignin, both directly and in buffered aqueous solutions (pH 7.0 and 5.5) containing lignin and NO 2 \t or lignin and NO 3 ·t . The percentage recovery of N was highly variable, being dependent on the analytical method and on pH. There appeared to be a reaction between lignin and NO 2 ·t or NO 3 ·t during the analytical procedure. The Kjeldahl method achieved a higher recovery of organic N from pure lignin than the persulphate method, but it showed a higher coefficient of variation. In buffered samples containing lignin together with NO 2 ·t or NO 3 ·t , recoveries of NO 2 ·t and NO 3 ·t were considerably lower for the Montgomery and Dymock and the Devarda methods than for the procedure using an auto-analyzer. The former procedures appeared to fix NO x ·t . With the auto-analyzer and the Devarda methods, recovery was increased with increasing pH values. The Kjeldahl method gave very high standard deviations. It proved unreliable for the analysis of organic N in samples containing both lignin and NO x ·t . During the persulphate analysis, significant N losses were calculated, probably because of acid-induced nitrosation or nitration and subsequent volatilization of N during the persulphate analysis itself.
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    Regulation of urease production in soil by microbial assimilation of nitrogen (1992)
    Springer
    Biology and fertility of soils 12 (1992), S. 261-264 
    Details
    ISSN: 1432-0789
    Keywords: Urease production ; Soil microorganisms ; Ammonium ; Nitrate ; Amino acids ; Nitrogen assimilation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Studies of the effects of different forms of N on urease production in soils amended with organic C showed that although microbial activity, as measured by CO2 production, was stimulated by the addition of NH4 + or NO3 - to C-amended soils (200 μmol glucose-C g−1 soil), urease production was repressed by these forms of N. The addition of L-methionine sulfoximine, an inhibitor of inorganic N assimilation by microorganisms, relieved the NH4 + and NO3 - repression of urease production in C-amended soil. The addition of sodium chlorate, an inhibitor of NO3 - reduction to NH4 + by microorganisms, relieved the NO3 - repression of urease production, but did not eliminate the repression associated with NH4 +. These observations indicate that microbial production of urease in C-amended soils is not directly repressed by NH4 + or NO3 -, but by products formed by microbial assimilation of these forms of N. This conclusion is supported by our finding that the biologically active L-isomers of alanine, arginine, asparagine, aspartate, and glutamine, repressed urease production in C-amended soil, whereas the D-isomers of these amino acids had little or no influence on urease production. This work suggests that urease synthesis by soil microorganisms is controlled by the global N regulon.
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    Availability of organic carbon for denitrification of nitrate in subsoils (1992)
    Springer
    Biology and fertility of soils 14 (1992), S. 219-222 
    Details
    ISSN: 1432-0789
    Keywords: Denitrification ; Nitrate ; Subsoils ; Organic carbon ; Denitrifying microorganisms ; Plant residues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Previous work in our laboratory indicated that the slow rate of denitrification in Iowa subsoils is not due to a lack of denitrifying microorganisms, but to a lack of organic C that can be utilized by these microorganisms for reduction of NO 3 − . This conclusion was supported by studies showing that drainage water from tile drains under agricultural research plots contained only trace amounts of organic C and had very little, if any, effect on denitrification in subsoils. Aqueous extracts of surface soils promoted denitrification when added to subsoils, and their ability to do so increased with increase in their organic C content. Amendment of surface soils with corn and soybean residues initially led to a marked increase in the amounts of organic C in aqueous extracts of these soils and in the ability of these extracts to promote denitrification in subsoils, but these effects were short-lived and could not be detected after incubation of residue-treated soils for a few days. We conclude from these observations that water-soluble organic C derived from plant residues is decomposed so rapidly in surface soils that very little of this C is leached into subsoils, and that this largely accounts for the slow rate of denitrification of nitrate in subsoils.
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    Factors affecting the availability of organic carbon for denitrification of nitrate in subsoils (1993)
    Springer
    Biology and fertility of soils 15 (1993), S. 132-136 
    Details
    ISSN: 1432-0789
    Keywords: Denitrification ; Nitrate ; Subsoils ; Organic carbon ; Denitrifying microorganisms ; Freezing ; Drying ; Plants ; Plant residues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Recent work in our laboratory indicated that the slow rate of denitrification in Iowa subsoils is not due to a lack of denitrifying microorganisms, but to a lack of organic C that can be utilized by these microorganisms for reduction of nitrate. To identify factors affecting the availability of leachable organic C in surface soils capable of promoting denitrification in subsoils, we studied the effects of freezing and drying and of plants and plant residues on the amounts of water-soluble organic C in surface soils and the ability of this organic C to promote denitrification in subsoils. We found that aqueous extracts of field-moist, frozen, and air-dried surface soils promoted denitrification in subsoils and that their stimulatory effects on denitrification were highly correlated (r=0.93) with their organic C contents and decreased in the order air-dried soils ≫ frozen soils 〉field-moist soils. But a detailed study of the effect of drying a surface soil to different water tensions indicated that drying of soils under natural conditions is not likely to lead to a substantial increase in their content of water-soluble organic C. Amendment of surface soils with corn or soybean residues led to a marked increase in the amount of organic C in aqueous extracts of the soils and in the ability of these extracts to promote denitrification in subsoils. These effects of plant residues could not be detected after incubation of residue-treated soils for a few days under aerobic conditions, but they increased markedly with an increase in the time of incubation from 1 to 10 days when residue-treated soils were incubated under anaerobic conditions. Analyses for organic acids indicated that this increase was largely due to fermentative production of acetic, propionic, and butyric acids by soil microorganisms. Growth chamber studies showed that growth of corn, soybean, wheat, and sorghum plants on surface soil did not significantly increase the organic C content of leachates of the soil or the ability of these leachates to promote denitrification in subsois. We conclude that plant residues are a major source of the leachable organic C in surface soils that is capable of promoting denitrification in subsoils.
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    A national critical loads framework for atmospheric deposition effects assessment: IV. Model selection, applications, and critical loads mapping (1993)
    Springer
    Environmental management 17 (1993), S. 355-363 
    Details
    ISSN: 1432-1009
    Keywords: Sulfate ; Nitrate ; Critical loads ; Modeling ; Deposition standards
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The critical loads approach is emerging as an attractive means for evaluating the effects of atmospheric deposition on sensitive terrestrial and aquatic ecosystems. Various approaches are available for modeling ecosystem responses to deposition and for estimating critical load values. These approaches include empirical and statistical relationships, steady-state and simple process models, and integrated-effects models. For any given ecosystem, the most technically sophisticated approach will not necessarily be the most appropriate for all applications; identification of the most useful approach depends upon the degree of accuracy needed and upon data and computational requirements, biogeochemical processes being modeled, approaches used for representing model results on regional bases, and desired degree of spatial and temporal resolution. Different approaches are characterized by different levels of uncertainty. If the limitations of individual approaches are known, the user can determine whether an approach provides a reasonable basis for decision making. Several options, including point maps, grid maps, and ecoregional maps, are available for presenting model results in a regional context. These are discussed using hypothetical examples for choosing populations and damage limits.
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    Pharmakologie und klinische Pharmakologie der organischen Nitrate (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. S97 
    Details
    ISSN: 1432-1041
    Keywords: Nitrate ; klinische Pharmakologie ; Angina pectoris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Zusammenfassung In diesem Beitrag sollen gegenwärtige Konzepte und künftige Aspekte pharmakologischer Interventionen bei der Behandlung der koronaren Herzkrankheit zusammengefaßt werden. Vor allem neue Erkenntnisse zur Pathophysiologie der koronaren Herzkrankheit, wie die dynamische Pathogenese koronarer Arteriosklerosen, die mögliche Rolle von Endothelin bei Vasospasmen, sowie neue Aspekte zu Pharmakodynamik und Pharmakokinetik der organischen Nitrate werden diskutiert. Auch wird auf die Rolle des sympatischen Nervensystems als wichtiger Faktor in der Pathophysiologie und der klinischen Pharmakologie bei der Behandlung der Angina pectoris eingegangen.
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    The periplasmic nitrite reductase of Thauera selenatis may catalyze the reduction of selenite to elemental selenium (1993)
    Springer
    Archives of microbiology 160 (1993), S. 241-247 
    Details
    ISSN: 1432-072X
    Keywords: Anaerobic respiration ; Selenate ; Nitrate ; Selenite reduction ; Nitrite reductase ; Selenium (elemental) Thauera selenatis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Thauera selenatis grows anaerobically with selenate, nitrate or nitrite as the terminal electron acceptor; use of selenite as an electron acceptor does not support growth. When grown with selenate, the product was selenite; very little of the selenite was further reduced to elemental selenium. When grown in the presence of both selenate and nitrate both electron acceptors were reduced concomitantly; selenite formed during selenate respiration was further reduced to elemental selenium. Mutants lacking the periplasmic nitrite reductase activity were unable to reduce either nitrite or selenite. Mutants possessing higher activity of nitrite reductase than the wild-type, reduced nitrite and selenite more rapidly than the wild-type. Apparently, the nitrite reductase (or a component of the nitrite respiratory system) is involved in catalyzing the reduction of selenite to elemental selenium while also reducing nitrite. While periplasmic cytochrome C 551 may be a component of the nitrite respiratory system, the level of this cytochrome was essentially the same in mutant and wild-type cells grown under two different growth conditions (i.e. with either selenate or selenate plus nitrate as the terminal electron acceptors). The ability of certain other denitrifying and nitrate respiring bacteria to reduce selenite will also be described.
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    Geobacter metallireducens gen. nov. sp. nov., a microorganism capable of coupling the complete oxidation of organic compounds to the reduction of iron and other metals (1993)
    Springer
    Archives of microbiology 159 (1993), S. 336-344 
    Details
    ISSN: 1432-072X
    Keywords: Iron ; Uranium ; Manganese ; Nitrate ; Anaerobic sediments ; Delta proteobacteria ; Aromatics ; Heavy metals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The gram-negative metal-reducing microorganism, previously known as strain GS-15, was further characterized. This strict anaerobe oxidizes several short-chain fatty acids, alcohols, and monoaromatic compounds with Fe(III) as the sole electron acceptor. Furthermore, acetate is also oxidized with the reduction of Mn (IV), U (VI), and nitrate. In whole cell suspensions, the c-type cytochrome(s) of this organism was oxidized by physiological electron acceptors and also by gold, silver, mercury, and chromate. Menaquinone was recovered in concentrations comparable to those previously found in gram-negative sulfate reducers. Profiles of the phospholipid ester-linked fatty acids indicated that both the anaerobic desaturase and the branched pathways for fatty acid biosynthesis were operative. The organism contained three lipopolysaccharide hydroxy fatty acids which have not been previously reported in microorganisms, but have been observed in anaerobic freshwater sediments. The 16S rRNA sequence indicated that this organism belongs in the delta proteobacteria. Its closest known relative is Desulfuromonas acetoxidans. The name Geobacter metallireducens is proposed.
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    Cell yield (YM) of Thauera selenatis grown anaerobically with acetate plus selenate or nitrate (1993)
    Springer
    Archives of microbiology 160 (1993), S. 295-298 
    Details
    ISSN: 1432-072X
    Keywords: Anaerobic respiration ; Selenate ; Nitrate ; Acetate ; Cell protein yield ; YM ; ATP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Thauera selenatis was grown anaerobically in minimal medium with either selenate or nitrate as the terminal electron acceptor and acetate as the carbon source and electron donor. The molar cell protein yields, YM-protein (selenate) and YM-protein (nitrate), were found to be 7.8 g cell protein/mol selenite formed and 7.5 g cell protein/mol nitrite formed, respectively. These values represent YM values of 57 and 55 g (dry weight)/mol acetate when selenate or nitrate was the electron acceptor, respectively. Based upon a calculated YATP value of 10.0 g (dry weight) cells/mol ATP, for growth on acetate in inorganic salts, growth with selenate as the terminal electron acceptor theoretically yielded 5.7 ATP/acetate oxidized, and 5.5 ATP when nitrate was the terminal electron acceptor. The results support the conclusion that energy is conserved via electron transport phosphorylation when selenate or nitrate reduction are the terminal electron acceptors during anaerobic growth with acetate.
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    Two differentially regulated nitrate reductases required for nitrate-dependent, microaerobic growth of Bradyrhizobium japonicum (1994)
    Springer
    Archives of microbiology 162 (1994), S. 310-315 
    Details
    ISSN: 1432-072X
    Keywords: Bradyrhizobium japonicum ; Nitrate ; Membrane-bound nitrate reductase ; Nitrate reductase mutants ; Microaerobiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Native PAGE of Triton x-100-solubilized membranes from Bradyrhizobium japonicum strain PJ17 grown microaerobically (2% O2, v/v) in defined nitrate-containing medium resolved two catalytically active nitrate reductase (NR) species with apparent molecular masses of 160 kDa (NRI) and 200 kDa (NRII). NRI and NRII were also found in membranes from cells of strain PJ17 that were first grown in defined medium with glutamate and further incubated microaerobically in the presence of 5 mmol/l KNO3. However, only NRI was detected in cell membranes of strain PJ17 when nitrate was omitted from the microaerobic incubation medium. Four mutants unable to grow at low O2 tension in the presence of nitrate were isolated after transposon Tn5 mutagenesis. Membranes from mutants GRF110 and GRF116 showed mainly NRI, while the other two mutants, GRF3 and GRF4, expressed mostly NRII. These results indicate that the ability of B. japonicum PJ17 to grow under microaerobic conditions depends upon the presence of two membrane-bound NR enzymes whose synthesis seem to be independently induced by microaerobiosis (NRI) or by both microaerobiosis and nitrate (NRII).
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    Two differentially regulated nitrate reductases required for nitrate-dependent, microaerobic growth of Bradyrhizobium japonicum (1994)
    Springer
    Archives of microbiology 162 (1994), S. 310-315 
    Details
    ISSN: 1432-072X
    Keywords: Key words     Bradyrhizobium japonicum ; Nitrate ; Membrane-bound nitrate reductase ; Nitrate reductase mutants ; Microaerobiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract      Native PAGE of Triton X-100-solubilized membranes from Bradyrhizobium japonicum strain PJ17 grown microaerobically (2% O2, v/v) in defined nitrate-containing medium resolved two catalytically active nitrate reductase (NR) species with apparent molecular masses of 160 kDa (NRI) and 200 kDa (NRII). NRI and NRII were also found in membranes from cells of strain PJ17 that were first grown in defined medium with glutamate and further incubated microaerobically in the presence of 5 mmol/l KNO3. However, only NRI was detected in cell membranes of strain PJ17 when nitrate was omitted from the microaerobic incubation medium. Four mutants unable to grow at low O2 tension in the presence of nitrate were isolated after transposon Tn5 mutagenesis. Membranes from mutants GRF110 and GRF116 showed mainly NRI, while the other two mutants, GRF3 and GRF4, expressed mostly NRII. These results indicate that the ability of B. japonicum PJ17 to grow under microaerobic conditions depends upon the presence of two membrane-bound NR enzymes whose synthesis seem to be independently induced by microaerobiosis (NRI) or by both microaerobiosis and nitrate (NRII).
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    URL: http://dx.doi.org/10.1007/s002030050143
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    Ammonium and nitrate uptake rates and rhizosphere pH in non-mycorrhizal roots of Norway spruce [Picea abies (L.) Karst.] (1991)
    Springer
    Trees 5 (1991), S. 14-21 
    Details
    ISSN: 1432-2285
    Keywords: Ammonium ; Calcium ; Nitrate ; Picea abies ; Rhizosphere pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Relationships between root zone temperature, concentrations and uptake rates of NH 4 + and NO 3 − were studied in non-mycorrhizal roots of 4-year-old Norway spruce under controlled environmental conditions. Additionally, in a forest stand NH 4 + and NO 3 − uptake rates along the root axis and changes in the rhizosphere pH were measured. In the concentration (Cmin) range of 100–150 μM uptake rates of NH 4 + were 3–4 times higher than those of NO 3 − The preference for NH 4 + uptake was also reflected in the minimum concentration (Cmin) values. Supplying NH4NO3, the rate of NO 3 − uptake was very low until the NH 4 + concentrations had fallen below about 100 μM. The shift from NH 4 + to NO 3 − uptake was correlated with a corresponding shift from net H+ production to net H+ consumption in the external solution. The uptake rates of NH 4 + were correlated with equimolar net production of H+. With NO 3 − nutrition net consumption of H+ was approximately twice as high as uptake rates of NO 3 − In the forest stand the NO 3 − concentration in the soil solution was more than 10 times higher than the NH 4 + concentration (〈100 μM), and the rhizosphere pH of non-mycorrhizal roots considerably higher than the bulk soil pH. The rhizosphere pH increase was particularly evident in apical root zones where the rates of water and NO 3 − uptake and nitrate reductase activity were also higher. The results are summarized in a model of water and nutrient transport to, and uptake by, non-mycorrhizal roots of Norway spruce in a forest stand. Model calculations indicate that delivery to the roots by mass flow may meet most of the plant demand of nitrogen and calcium, and that non-mycorrhizal root tips have the potential to take up most of the delivered nitrate and calcium.
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    Nitrate levels affect the development of the black locust-Rhizobium symbiosis (1991)
    Springer
    Trees 5 (1991), S. 227-231 
    Details
    ISSN: 1432-2285
    Keywords: Robinia pseudoacacia L. ; Nitrate ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Experiments with black locust (Robinia pseudoacacia L.) seedlings grown under strictly controlled laboratory conditions indicated that the availability of nitrate has a marked impact on nitrogen fixation. When nitrate concentrations were very low, both nodulation and seedling growth were impaired, whereas nitrate concentrations high enough to promote plant growth strongly inhibited symbiotic nitrogen fixation. When nitrate was added to the growth medium after infection, nodulation and nitrogen fixation of the seedlings decreased. This effect was even more marked when nitrate was applied before infection with rhizobia. Higher nitrogen concentrations also reduced nodule number and nodule mass when applied simultaneously with the infecting bacteria. The contribution of symbiotic nitrogen fixation to black locust shoot mass by far exceeded its effects on shoot length and root mass. When nitrate availability was very low, specific nitrogen fixation (i. e. nitrogenase activity per nodule wet weight) was improved with increasing nitrogen supply, but rapidly decreased with higher nitrogen concentrations.
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    Nitrate and nitrate reductase in Erythrina caffra seeds: Enhancement of induction by anoxia and possible role in germination (1993)
    Springer
    Planta 189 (1993), S. 298-300 
    Details
    ISSN: 1432-2048
    Keywords: Anoxia ; Erythrina (anaerobic germination) ; Germination (anoxic) ; Nitrate ; Nitrate reductase ; Pisum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nitrate level in seed embryonic axes of Erythrina caffra Thunb. which is capable of anaerobic germination, was about 2.5 times higher than in seed axes of Pisum sativum L. a species incapable of anaerobic germination. Nitrate levels in E. caffra seeds decreased during germination and this was not due to leaching. Both NADH- and NADPH-dependent nitrate reductase (NAR) activities increased during germination. The increase was prevented by cycloheximide. The activity of NADH-NAR (EC 1.6.6.1) was higher than that of NADPH-NAR (EC 1.6.6.3). Both NAR activities were higher in anoxia than in air during germination. The NAR activities in Pisum seeds were very much lower than in Erythrina seeds. Anoxia (N2 or argon) enhanced the induction of NAR by KNO3 in germinated E. caffra axes. The NADH- and NADPH-NAR activities were induced to equally high levels by KNO3 under anoxia. The enhancement was depressed by cycloheximide. It is concluded that nitrate and NAR activity may play a role in the anaerobic germination of E. caffra seeds.
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    Coaction of blue/ultraviolet-A light and light absorbed by phytochrome in controlling the appearance of ferredoxin-dependent glutamate synthase in the Scots pine (Pinus sylvestris L.) seedling (1991)
    Springer
    Planta 183 (1991), S. 374-380 
    Details
    ISSN: 1432-2048
    Keywords: Cryptochrome ; Glutamate synthase (Fd-GOGAT) ; Nitrate ; Photoreceptor (coaction of blue/UV-A light and phytochrome) ; Phytochrome ; Pinus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The appearance of NADH- and ferredoxin (Fd)-dependent glutamate synthases (GOGATs) was investigated in the major organs (roots, hypocotyl and cotyledonary whorl) of the Scots pine seedling. It was found that cytosolic NADH-GOGAT (EC 1.4.1.14) dropped to a low level during the experimental period (from 4 to 12 d after sowing) and was not significantly affected by light. On the other hand, plastidic Fd-GOGAT (EC 1.4.7.1) increased strongly in response to light. Whereas similar amounts of NADH-GOGAT were found in the different organs, Fd-GOGAT was mainly found in the cotyledons even in the presence of nitrate. Protein chromatography revealed only a single Fd-GOGAT peak. No isoforms were detected. Experiments to investigate regulation of the appearance of Fd-GOGAT in the cotyledonary whorl yielded the following results: (i) In darkness, neither nitrate (15 mM KNO3) nor ammonium (15 mM NH4Cl) had an effect on the appearance of Fd-GOGAT. In the light, nitrate stimulated Fd-GOGAT activity by 30% whereas ammonium had no effect. The major controlling factor is light. (ii) The action of long-term white light (100 W · m−2) could be replaced quantitatively by blue light (B, 10 W · m−2). Since the action of long-term far-red light was very weak, operation of the ‘High Irradiance Reaction’ of phytochrome is excluded. On the other hand, light-pulse experiments with dark-grown seedlings showed the involvement of phytochrome. (iii) Red light, operating via phytochrome, could fully replace B, but only up to 10 d after sowing. Thereafter, there was an absolute requirement for B for a further increase in the enzyme level. It appears that the operation of phytochrome was replaced by the operation of cryptochrome (B/UV-A photoreceptor). (iv) However, dichromatic experiments (simultaneous treatment of the seedlings with two light beams to vary the level of the far-red-absorbing form of phytochrome (Pfr) in blue light) showed that B does not affect enzyme appearance if the Pfr level is low. It is concluded that B is required to maintain responsiveness of Fd-GOGAT synthesis to phytochrome (Pfr) beyond 10 d after sowing.
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    Coaction of light, nitrate and a plastidic factor in controlling nitrite-reductase gene expression in spinach (1991)
    Springer
    Planta 184 (1991), S. 74-80 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Nitrate ; Nitrite reductase (control) ; Phytochrome ; Spinacia (nitrite reductasegene expression)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It is well established that nitrite reductase (NIR; EC 1.7.7.1) a key enzyme of nitrate reduction — is “induced” by nitrate and light. In the present study with the spinach (Spinacia oleracea L.) seedling the dependency of NIR appearance on nitrate, light and a ‘plastidic factor’ was investigated to establish the nature of the coaction between these controlling factors. A cDNA clone coding for spinach NIR was available as a probe. The major results we have obtained are the following: (i) The light effect on the appearance of NIR activity occurs through phytochrome. No specific bluelight effect is involved, (ii) Immunotitration data indicate that light affects the appearance of NIR by inducing the de-novo synthesis of the NIR protein, (iii) A multiplicative relationship exists between the action of nitrate and light on NIR appearance. This indicates that the actions of light and nitrate are indeed independent of each other but that both factors operate on the same causal sequence, (iv) Anion-exchange chromatography revealed only a single form of NIR in spinach. Experiments involving plastid photooxidation indicate that this NIR is exclusively plastidic. (v) Northern blot analysis of NIR mRNA showed a strong increase of the steady-state level in the presence of nitrate whereas light had no effect; NIR mRNA was almost undetectable when the plastids were damaged by photooxidation. It is concluded that NIR gene expression in spinach requires positive control by a ‘plastidic factor’. Moreover, nitrate exerts a coarse control at the mRNA level whereas fine tuning of NIR protein synthesis is post-transcriptional and is exerted by light, operating via phytochrome.
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    Appearance of nitrite-reductase mRNA in mustard seedling cotyledons is regulated by phytochrome (1990)
    Springer
    Planta 181 (1990), S. 327-334 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression (control points) ; Nitrate ; Nitrite reductase ; Phytochrome ; Sinapis (phytochrome)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrate reductase (NR, EC 1.6.6.1) and nitrite reductase (NIR, EC 1.7.7.1) are the key enzymes of nitrate reduction. It is well established that the appearance of these enzymes is “induced” by nitrate, and it is generally believed that NR is cytosolic while NIR is plastidic. In mustard (Sinapis alba L.) cotyledons we observed two isoforms of NIR (NIR1 and NIR2) using a chromato-focusing technique. Only one of them (NIR2) disappeared when the plastids were damaged by photooxidation in the presence of Norflurazon. It is concluded that NIR2 is plastidic while NIR1 is extraplastidic and not affected by photooxidation of the plastids. Both isoforms appear to have the same molecular weight (60 kilodaltons, kDa). Two distinct translation products which could be immunoprecipitated with NIR antiserum produced against total NIR from mustard were observed which differed slightly in molecular weight (60 versus 63 kDa). The 63-kDa polypeptide was considered to be the precursor of NIR2. While synthesis of NIR protein depended largely on nitrate, the levels of in-vitro-translatable NIR mRNAs were found to be either independent of nitrate and light (NIR1) or controlled by phytochrome only (NIR2). It appears that phytochrome strongly stimulates the level of mRNA while significant enzyme synthesis (NIR2) takes place only in the presence of relatively large amounts of nitrate. Since an increased enzyme level was strictly correlated with an increase of immunoresponsive NIR protein it is improbable that activation of a precursor plays a role. Rather, it is concluded that, in situ, nitrate controls translation.
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    Photocontrol of nitrite reductase gene expression in the barley seedling (Hordeum vulgare L.) (1993)
    Springer
    Planta 192 (1993), S. 110-117 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Nitrate ; Nitrite reductase (Control) ; Phytochrome ; Hordeum (nitrite reductase gene expression)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrite reductase (NIR, EC 1.7.7.1) — a key enzyme of nitrate assimilation — is known to be induced by nitrate and light. In the present work with barley (Hordeum vulgare L.) seedlings, control of NIR gene expression by light and its dependency on intact plastids was studied. The major results were as follows: (i) It was confirmed that a single isoform of NIR occurs in shoot and root. (ii) Any light-mediated increase of NIR activity is strictly correlated with an increase in cross-reacting material. (iii) Exogenous nitrate is absolutely required for NIR synthesis and the appearance of NIR transcripts. The nitrate effect is saturated at 10 mM. (iv) Light-pulse experiments and long-term light treatments indicate the involvement of phytochrome in the light response. (v) While a small light effect possibly occurs in the root, a strong action of phytochrome was observed in the shoot. (vi) Photooxidative treatments of plastids led to a strong decrease of the NIR level and almost abolished the appearance of NIR transcripts. (vii) With plastids intact, application of nitrate (10 mM) caused the appearance of a considerable transcript level even in darkness. Light treatments in the presence of nitrate stimulated the transcript level further. (viii) Since a correlation between transcript level and rate of NIR increase was found it was concluded that in barley — in contrast to mustard, spinach and tobacco — NIR gene expression is controlled predominantly, if not exclusively, at the level of transcript accumulation.
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  • 47
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    A channel that allows inwardly directed fluxes of anions in protoplasts derived from wheat roots (1994)
    Springer
    Planta 192 (1994), S. 295-305 
    Details
    ISSN: 1432-2048
    Keywords: Chloride channel ; Nitrate ; Potassium channel ; Salinity ; Triticum roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An anion channel that only allows outward current flow (anion influx) has been identified in protoplasts derived from wheat (Triticum aestivum L., Triticum turgidum L.) roots. The anion outward rectifier (anion OR) measured by patch-clamp of whole cells activated very quickly, usually reaching a steady-state level in less than 100 ms and was easily distinguished from the cation outward rectifier (cation OR) which activated more slowly during membrane depolarisation. The anion OR is permeable to NO 3 − and Cl−, moderately permeable to I−, and relatively impermeable to H2PO4/− and ClO4/−. An anomalous mole-fraction effect between ClO4/ − and Cl− was observed on the outward current, indicating that the channel is a multi-ion pore. The anion OR is gated by both voltage and external anion concentration such that it activates near to the equilibrium potential for the permeant anion. It activated at more negative membrane potentials when NO 3 − was substituted for Cl− in the external medium, indicating that the channel may function to allow NO 3 − influx under luxuriant external NO 3 − concentrations. For most experiments, K+ and Cl− were the main cation and anion in solution, and under these conditions it appeared likely that the anion OR functioned in membrane-potential regulation by facilitating a Cl− influx at membrane potentials more positive than the chloride reversal potential (ECl). If ECl was more negative than the K+ reversal potential (EK) then the anion OR dominated but both the anion and cation ORs occurred together when the membrane potential difference (Vm) was positive of both ECl and EK. The cation OR was inhibited by increasing external Cl− concentrations, but the anion OR was not affected by external K+ or Na+ concentration. The anion-transport inhibitors, zinc and phenylglyoxal were ineffective in blocking the anion OR. 4,4′-Di-isothiocyanostilbene-2, 2′-disulfonic acid (DIDS) irreversibly blocked about 34% of the current when applied extracellularly at a concentration of 25 μM, and about 69% at a concentration of 200 μM. However, DIDS (200 μM) also occasionally acted as an irreversible blocker of the cation OR. Perchlorate blocked irreversibly 75% of the current at an external concentration of 10 mM and did not block the cation OR. Whole-cell currents also indicated that the anion OR was insensitive to external pH (pH=5–7) and calcium concentration ([Ca2+]=0.1–10 mM). Increasing intracellular calcium concentration significantly increased the occurrence of the fast outward current in whole cells (P 〈 0.005, X2 test). With approximately 10 nM calcium inside the cell the anion outward current was observed in 64% (n = 45) of cells and with 50 nM calcium inside the cell the anion current was observed in 88% (n = 69) of cells. Single-anion OR channels observed in outside-out patches had a conductance in 300 mM KCl (external) of about 4 pS. When voltage pulses were applied to outside-out patches the average currents were similar to those observed in whole cells. The significance of the anion OR as a likely route for Cl uptake in high salinities is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198563
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  • 48
    Electronic Resource
    Electronic Resource
    Nitrate reductases in hexaploid and tetraploid wheats and Aegilops (1990)
    Springer
    Theoretical and applied genetics 79 (1990), S. 8-12 
    Details
    ISSN: 1432-2242
    Keywords: Constitutive enzyme ; Genome ; Induciblebenzyme ; Nitrate ; Pressure selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nitrate reductase activity (NR activity), protein content (NR protein) and polypeptides were compared in shoots of Triticum aestivum ssp. vulgare (L.) cv Fidel (bread wheat, AABBDD genome), Triticum dicoccum cv Vernal (AABB genome), Aegilops squarrosa var. strangulata (DD genome) and the amphiploid 365 (AABBDD genome), produced by crossing T. dicoccum cv Vernal and Ae. squarrosa var. strangulata. Constitutive NR protein and activity were found in shoots of all seedlings grown without nitrate, with the highest activity in the bread wheat. The inducible NR protein and activity developed upon the addition of nitrate. A 116-K polypeptide was identified as the main component of the NR from the bread wheat, while a faint, sometimes discernable 94-K band appeared on Western blots. Only one NR polypeptide could be identified in Ae. squarrosa —the 94 K. An intermediary situation was observed with the tetraploid T. dicoccum and the amphiploid: The 94-K polypeptide was the only one separated from NR of seedlings grown in the absence of nitrate. The 116-K polypeptide appeared after the addition of nitrate. The intensity of its band on the gel increased with the duration of the nitrate treatment. When comparing Ae. squarrosa and T. dicoccum, the constitutive isozyme (94-K polypeptide) was found in the D as well as in the AB genomes, while the inducible NR (116-K polypeptide) was absent from the D genome. Addition of the D genome into the AB genome slightly reinforced the expression of the inducible form (AB genome expression) in the amphiploid wheat. We postulate that the inducible form of NR in the bread wheat resulted from an evolutionary selection pressure favoured by cultivation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223779
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  • 49
    Electronic Resource
    Electronic Resource
    Nitrate-nitrite levels in commercially processed and home processed beets and spinach (1991)
    Springer
    Plant foods for human nutrition 41 (1991), S. 261-268 
    Details
    ISSN: 1573-9104
    Keywords: Nitrate ; nitrite ; beets ; spinach ; commercial food processing ; home food preservation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrate and nitrite content of commercially processed and home processed beets and spinach samples were analyzed using specific ion electrode and colorimetric methods. The home processed beets were found to be significantly higher in nitrate content than the commercially processed beets. This difference was attributed to differences in processing methods. Pickled and Harvard beets contained significantly lower amounts of nitrate/nitrite on a dry weight basis than the other types of processed beets, evidently due to the diluting effect of added sucrose. Home frozen spinach showed a trend toward lower nitrate content than commercially frozen spinach, although the difference was not significant. Length of storage of home processed beets and spinach did not appear to affect nitrate or nitrite content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02196395
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  • 50
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    Electronic Resource
    Nitrate and vitamin C from fruits and vegetables: Impact of intake variations on nitrate and nitrite excretions of humans (1994)
    Springer
    Plant foods for human nutrition 45 (1994), S. 71-80 
    Details
    ISSN: 1573-9104
    Keywords: Nitrate ; Nitrite ; Ascorbic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The objective of the study was to determine nitrate + nitrite excretions of human subjects fed variable amounts of nitrates and nitrites and vitamin C from fruits and vegetables. During four, randomly-arranged experimental periods of seven days each, the 12 apparently healthy, adult human subjects consumed laboratory controlled, constant, diets which were systematically varied in kinds of fruits and vegetable to provide the four following variations: 414 mg nitrate + nitrite and 23 mg vitamin C, 412 mg nitrate + nitrite and 177 mg vitamin C, 23 mg nitrate + nitrite and 39 mg vitamin C, and 21 mg nitrate + nitrite and 193 mg vitamin C per subject per day, respectively. Subjects made complete collections of urine and stools throughout the study. Regardless of type of experimental diet fed, no nitrates and nitrites were detected in the feces. Urinary excretion of nitrate + nitrite was significantly greater at the higher levels of nitrate + nitrite intake than at the lower intake levels. Increased intake of vitamin C at either level of nitrate + nitrite intake resulted in apparent decreased urinary excretions of nitrite + nitrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01091231
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  • 51
    Electronic Resource
    Electronic Resource
    Effects of sulphur, nitrogen, phosphorus, potassium, and water stress on dietary fibre fractions, starch, amino acids and on the biological value of potato protein (1994)
    Springer
    Plant foods for human nutrition 45 (1994), S. 299-313 
    Details
    ISSN: 1573-9104
    Keywords: Digestible energy ; Lignin ; N-balance in rats ; Nitrate ; Non-starch polysaccharides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In pot experiments with greatly differing rates of N, P, K, and S, and 3 levels of water, dry matter (DM) yields of tubers varied from 28 to 454 g/pot. Especially P-, K- and S-deficiency reduced the starch content of boiled potatoes, from P from 74 to 59% in DM. S-deficiency increased soluble, insoluble and total digestible fibre (TDF) from about 9 to 12.4% TDF in DM of boiled potatoes. Lignin content of fresh potato DM was increased from 0.7 to 2.0 and from 0.8 to 3.7% by P- and K-deficiency. P-deficiency considerably increased arabinose, galactose, and uronic acid, and decreased glucose content. N-application and P-, K- and S-deficiency increased total- and NO3-N concentrations which varied from 1.32 to 3.67% and from 17 to 400 ppm in DM. Water stress slightly decreased total-N content. Increasing N in DM, due to high N-rates or P- or K-deficiency, decreased concentrations in crude protein (CP) of all essential amino acids, whereas aspartic acid (asparagine) increased. S-deficiency caused particularly strong decreases in concentrations of essential amino acids from 1.28 to 0.49, 1.62 to 1.10, 5.24 to 3.68, and 5.59 to 2.57 g/16 g N of cystine, methionine, lysine and leucine, respectively. Glutamic acid (glutamine) content was increased from 15.7 to 27.6 g/16 g N by S-deficiency. Expressed as g amino acid/kg DM, all amino acid concentrations increased with increasing % N in DM. In N-balance trials with rats, increasing crude protein concentrations in DM of boiled potatoes increased the true digestibility (TD) of the protein from 72 to 90 but decreased the biological value (BV) from 89 to 65. S-deficiency caused a further reduction of the BV to 45. Excluding S-deficiency treatments, linear regression equations between CP concentrations and BV and TD gave correlation coefficients r of −0.94*** and 0.82***, respectively. There was close agreement between changes of BV and concentrations of first limiting amino acids (chemical score), with r=0.96***.
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    URL: http://dx.doi.org/10.1007/BF01088079
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  • 52
    Electronic Resource
    Electronic Resource
    Influence of growth conditions on the value of crisphead lettuce (1994)
    Springer
    Plant foods for human nutrition 46 (1994), S. 1-11 
    Details
    ISSN: 1573-9104
    Keywords: Chemical composition ; Cultivar ; Harvest data ; Lactuca sativa L. ; Lettuce ; Nitrate ; Nitrogen ; Plant age ; Tipburn ; Quality ; Vitamin C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The marketable and nutritional quality of crisphead lettuce as affected by nitrogen supply, cultivar, and plant age at harvest was investigated in six plantings during 1989 and 1990. The optimum yield of marketable heads was obtained at a total nitrogen supply of 150 kg N per ha although only small differences were observed to the yield at 100 and 200 kg total N per ha. The total nitrogen supply included the amount of mineral nitrogen within the rhizosphere. The incidence of dry tipburn in older leaves was clearly decreased by an increased nitrogen supply, especially at late planting. The content of nitrate was increased and the content of dry matter and vitamin C decreased with increased nitrogen supply. The vitamin C content was higher for the cultivar ‘Marius’ than for ‘Saladin’. As plants got older, the nutritional quality of crisphead lettuce decreased because the content of nutrients, especially vitamin C, decreased with increased plant age at harvest.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01088455
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  • 53
    Electronic Resource
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    Nitrate distribution and accumulation in an Ustochrept soil profile in a long term fertilizer experiment (1991)
    Springer
    Nutrient cycling in agroecosystems 28 (1991), S. 173-177 
    Details
    ISSN: 1573-0867
    Keywords: Nitrate ; nitrogen rates ; ground water contamination ; NPK fertilizers ; apparent N recovery ; farm yard manure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Distribution and accumulation of NO3—N, down to 210 cm depth, in the soil profile of a long term fertilizer experiment were studied after 16 cycles of cropping (maize-wheat-fodder cowpea). The application of fertilizer N without P and K or in combination with only P resulted in higher NO3—N concentration in the soil profile than the application of N with P and K. With an annual application of 320 kg N ha−1 alone, a peak in NO3—N accumulation occurred at 135 cm soil depth. However, with the application of NPK, no peak in NO3—N distribution was discernible and its content at most of the sampling depths was either less than or equal to N and NP treatments. The annual application of 10 tons farm yard manure (FYM) per ha along with NPK resulted in a relatively lower NO3—N content in the sub soil. The amount of NO3—N accumulation in the soil profile decreased as the cumulative N uptake by the crops increased. Application of fertilizer amounts greater than that of the recommended (100% NPK) resulted in low percent N recoveries in crops and greater NO3—N accumulation in the soil profile.
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    URL: http://dx.doi.org/10.1007/BF01049747
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