Relevant bibliographies by topics / Fixation de N2 [Azote]

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  2. Dissertations / Theses
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Academic literature on the topic 'Fixation de N2 [Azote]'

Author: Grafiati
Published: 4 June 2021
Last updated: 5 February 2022

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Journal articles on the topic "Fixation de N2 [Azote]"

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Ash, C. "Cryptic N2 Fixation." Science 337, no. 6093 (July 26, 2012): 391. http://dx.doi.org/10.1126/science.337.6093.391-a.

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Rao, V. M., Jayshree, Banwari Lal, P. Shailaja, and H. S. Narayana. "N2-fixation (N2-ase activity) inAzospirillum strains." Proceedings / Indian Academy of Sciences 98, no. 6 (December 1988): 483–88. http://dx.doi.org/10.1007/bf03053405.

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Patil, B. S., Q. Wang, V. Hessel, and J. Lang. "Plasma N2-fixation: 1900–2014." Catalysis Today 256 (November 2015): 49–66. http://dx.doi.org/10.1016/j.cattod.2015.05.005.

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Jena, P. K., and V. Rajaramamohan Rao. "Nitrogen fixation as influenced by pesticides and rice straw in paddy soils." Journal of Agricultural Science 108, no. 3 (June 1987): 635–38. http://dx.doi.org/10.1017/s0021859600080059.

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SummaryThe effect of three herbicides and an insecticide combination on nitrogen fixation in three paddy soils was investigated in a laboratory incubation study. The influence of pesticide combination on N2 fixation was evaluated in the presence and absence of rice straw under flooded and non-flooded conditions. In a non-flooded alluvial soil single or combined application of butachlor and carbofuran significantly stimulated N2 fixation. There was no effect on N2 fixation when thiobencarb was applied alone; but with thiobencarb in combination with carbofuran higher N2 fixation occurred. Both oxadiazone and thiobencarb had no effect on N2 fixation under flooded conditions, but in combination with carbofuran the N2 fixation was high. In acid sulphate saline Pokkali soil, rice straw application stimulated N2 fixation; the stimulatory effect of carbofuran either alone or in combination became more pronounced under flooded conditions. N2 fixation was low in a laterite Sukinda soil and the effect of pesticides was not changed by rice straw amendment. A uniform stimulation of N2 fixation occurred in soils when carbofuran was applied either singly or in combination with other herbicides tested. Results indicate that the effect of pesticides on N2 fixation varied with the rice straw application and water regime.
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Zilius, Mindaugas, Irma Vybernaite-Lubiene, Diana Vaiciute, Donata Overlingė, Evelina Grinienė, Anastasija Zaiko, Stefano Bonaglia, et al. "Spatiotemporal patterns of N<sub>2</sub> fixation in coastal waters derived from rate measurements and remote sensing." Biogeosciences 18, no. 5 (March 18, 2021): 1857–71. http://dx.doi.org/10.5194/bg-18-1857-2021.

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Abstract. Coastal lagoons are important sites for nitrogen (N) removal via sediment burial and denitrification. Blooms of heterocystous cyanobacteria may diminish N retention as dinitrogen (N2) fixation offsets atmospheric losses via denitrification. We measured N2 fixation in the Curonian Lagoon, Europe's largest coastal lagoon, to better understand the factors controlling N2 fixation in the context of seasonal changes in phytoplankton community composition and external N inputs. Temporal patterns in N2 fixation were primarily determined by the abundance of heterocystous cyanobacteria, mainly Aphanizomenon flos-aquae, which became abundant after the decline in riverine nitrate inputs associated with snowmelt. Heterocystous cyanobacteria dominated the summer phytoplankton community resulting in strong correlations between chlorophyll a (Chl a) and N2 fixation. We used regression models relating N2 fixation to Chl a, along with remote-sensing-based estimates of Chl a to derive lagoon-scale estimates of N2 fixation. N2 fixation by pelagic cyanobacteria was found to be a significant component of the lagoon's N budget based on comparisons to previously derived fluxes associated with riverine inputs, sediment–water exchange, and losses via denitrification. To our knowledge, this is the first study to derive ecosystem-scale estimates of N2 fixation by combining remote sensing of Chl a with empirical models relating N2 fixation rates to Chl a.
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Knapp, Angela N., Karen L. Casciotti, William M. Berelson, Maria G. Prokopenko, and Douglas G. Capone. "Low rates of nitrogen fixation in eastern tropical South Pacific surface waters." Proceedings of the National Academy of Sciences 113, no. 16 (March 14, 2016): 4398–403. http://dx.doi.org/10.1073/pnas.1515641113.

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An extensive region of the Eastern Tropical South Pacific (ETSP) Ocean has surface waters that are nitrate-poor yet phosphate-rich. It has been proposed that this distribution of surface nutrients provides a geochemical niche favorable for N2 fixation, the primary source of nitrogen to the ocean. Here, we present results from two cruises to the ETSP where rates of N2 fixation and its contribution to export production were determined with a suite of geochemical and biological measurements. N2 fixation was only detectable using nitrogen isotopic mass balances at two of six stations, and rates ranged from 0 to 23 µmol N m−2 d−1 based on sediment trap fluxes. Whereas the fractional importance of N2 fixation did not change, the N2-fixation rates at these two stations were several-fold higher when scaled to other productivity metrics. Regardless of the choice of productivity metric these N2-fixation rates are low compared with other oligotrophic locations, and the nitrogen isotope budgets indicate that N2 fixation supports no more than 20% of export production regionally. Although euphotic zone-integrated short-term N2-fixation rates were higher, up to 100 µmol N m−2 d−1, and detected N2 fixation at all six stations, studies of nitrogenase gene abundance and expression from the same cruises align with the geochemical data and together indicate that N2 fixation is a minor source of new nitrogen to surface waters of the ETSP. This finding is consistent with the hypothesis that, despite a relative abundance of phosphate, iron may limit N2 fixation in the ETSP.
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Chen, Hui, Rong Cai, Janki Patel, Fangyuan Dong, Hsiaonung Chen, and Shelley D. Minteer. "Upgraded Bioelectrocatalytic N2 Fixation: From N2 to Chiral Amine Intermediates." Journal of the American Chemical Society 141, no. 12 (March 5, 2019): 4963–71. http://dx.doi.org/10.1021/jacs.9b00147.

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Konno, U., U. Tsunogai, D. D. Komatsu, S. Daita, F. Nakagawa, A. Tsuda, T. Matsui, Y. J. Eum, and K. Suzuki. "Significance of N<sub>2</sub> fixation in dissolved fractions of organic nitrogen." Biogeosciences Discussions 7, no. 1 (February 1, 2010): 765–86. http://dx.doi.org/10.5194/bgd-7-765-2010.

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Abstract. Using the 15N2 tracer method and high-sensitivity δ15N analytical systems, we determined N2 fixation rates by dividing fractions into particulate organic nitrogen (PON: >0.7 μm) and dissolved organic nitrogen (DON: <0.7 μm). While N2 fixation in the DON fraction had been ignored in previous studies, we found significant N2 fixation signal in the DON fraction in our study. The areal N2 fixation rates estimated from the PON fractions varied from <1–160 μmol N m−2 d−1, and those estimated from the DON fractions ranged from <0.5–54 μmol N m−2 d−1. Thus, N2 fixation in the DON fractions accounted for 50% (ranging from <10% to 84%) of the total N2 fixation rates on an average. The new total N2 fixation flux, which includes fixation in DON fractions, has possibility to double the original estimates; therefore, the revised influx may reduce the imbalance in the global oceanic fixed nitrogen budget.
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Doughton, JA, PG Saffigna, I. Vallis, and RJ Mayer. "Nitrogen fixation in chickpea. II. Comparison of 15N enrichment and 15N natural abundance methods for estimating nitrogen fixation." Australian Journal of Agricultural Research 46, no. 1 (1995): 225. http://dx.doi.org/10.1071/ar9950225.

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The 15N enrichment and 15N natural abundance methods for estimating N2 fixation in chickpea were compared over a range of soil NO3-N levels at crop establishment varying from 10 to 326 kg N/ha (0-120 cm depth). Barley was used as a non-N2 fixing control crop. Both methods estimated reduced N2 fixation as soil NO3-N levels at crop establishment increased. Similar estimates of % N2 fixation were obtained at high values, but at low values the enrichment method gave lower estimates, some of which were negative. The 15N natural abundance method provided realistic estimates of % N2 fixation across all soil N03-N levels at crop establishment. An asymptotic curve described a close ( R2 = 0.95) relationship between these factors. Standard errors of estimates of means for the 15N natural abundance method remained acceptable and relatively stable over the full range of measurements; however, with the 15N enrichment method they became unacceptably large at low values of % N2 fixation. These large errors may have been partly due to legume and control plants assimilating mineral N of differing 15N enrichment. High mineral N levels associated with low values of % N2 fixation were also shown to reduce reliability of N2 fixation values estimated by the 15N enrichment method. These errors caused potentially greater inaccuracy at low values of % N2 fixation than at high values. To compare N2 fixation means statistically, transformations were necessary to stabilize variance and to impart lower weightings to plots with low values of % N2 fixation.
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Bonnet, S., O. Grosso, and T. Moutin. "Planktonic dinitrogen fixation along a longitudinal gradient across the Mediterranean Sea during the stratified period (BOUM cruise)." Biogeosciences 8, no. 8 (August 19, 2011): 2257–67. http://dx.doi.org/10.5194/bg-8-2257-2011.

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Abstract. This study provides extensive data on planktonic N2 fixation rates across the whole Mediterranean Sea. They show that N2 fixation occurs in Mediterranean waters during the stratification period, with a clear decreasing trend from the oligotrophic western basin (10–76 μmol m−2 d−1) to the ultra oligotrophic eastern basin (0–0.4 μmol m−2 d−1). Highest rates are measured in the less oligotrophic western basin, between the surface and 75 m-depth, where 45 to 75 % of N2 fixation are found within the picoplanktonic fraction (<3 μm). While the biogeochemical impact of N2 fixation in the eastern basin seems negligible, N2 fixation is able to sustain up to 35 % of new primary production during the stratified period in the western basin. These data disagree with indirect estimates of N2 fixation based on geochemical tracers and nutrient budgets, which indicates that N2 fixation increases with increasing N:P ratios and decreasing stable N isotopic signature of particulate organic nitrogen and NO3− from west to east. These results finally point out the need to assess N2 fixation at a higher temporal resolution in order to better understand the diazotrophs' dynamic under contrasted biogeochemical conditions.
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Dissertations / Theses on the topic "Fixation de N2 [Azote]"

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Dekaezemacker, Julien. "Etude de la fixation d'azote dans les environnements "déficitaires en azote" : Contribution des diazotrophes unicellulaires et contrôle par la disponibilité nutritive." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4098.

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Ce travail de thèse a pour but d'étudier la fixation d'azote marine dans les environnements riches mais déficitaires en azote (N), comparé au phosphore (P) dans un rapport N:P<16, grâce à l'utilisation d'approches complémentaire en culture in vitro et sur le terrain in situ. La première partie de ce travail a consisté à évaluer la réponse de la fixation d'azote de la cyanobactérie unicellulaire diazotrophe Crocosphaera watsonii face à des concentrations micromolaires en azote inorganique dissous (DIN) supposées inhiber l'activité de fixation d'azote : - suite à un apport sporadique, ou, - après une longue période d'acclimatation. Les résultats de ces études n'ont pas permis d'observer une inhibition des activités de fixation d'azote de cet organisme, laissant supposer que ce processus pourrait être actif dans une zone de l'Océan ayant ces même caractéristiques biogéochimiques : le Sud Est Tropical de l'Océan Pacifique (ETSP). En effet, cette zone est une des trois plus grandes zones de minimum d'oxygène (OMZ) de l'Océan et d'intenses processus de pertes de N (dénitrification et anammox) y ont lieu, résultant en un déficit de N par rapport au P. Des études présumaient que des processus inverses, de gains de N par la fixation d'azote, pourraient y être actifs mais aucune mesure à l'échelle du bassin n'y avait été faite car la fixation d'azote n'était supposée se produire que dans les environnements oligotrophes, comme les gyres subtropicaux. Dans le cadre d'un projet international, des missions océanographiques ont pu avoir lieu dans cette zone en Février 2010 pendant un évènement El Niño et en Mars-Avril 2011 pendant un évènement La Niña
The objectif of these thesis was to study dinitrogen fixation in marine environments rich but deficient of nitrogen (N) compared to phosphorus (P) in a ratio N:P<16, by using complementary approaches in culture in vitro and in the field in situ. The first part of this work was to evaluate the response of nitrogen-fixing unicellular Cyanobacteria Crocosphaera watsonii faced with micromolar concentrations of dissolved inorganic nitrogen (DIN) supposed to inhibit nitrogen fixation activity : - after sporadic input, or, - after a long period of acclimatization. The results of these studies have failed to observe the inhibition of nitrogen fixation activities of this organism, suggesting that this process could be active in an area of the Ocean with these same biogeochemical characteristics : the Eastern Tropical South Pacific (ETSP). Indeed, this area is one of the three largest oxygen minimum zones (OMZ) of the Ocean, where intense processes of N losses (denitrification and anammox) took place, resulting in a deficit of N compared to P. Studies assumed that the inverse process, gain of N by nitrogen fixation, could be active in the ETSP but no measurements across the basin have been performed because nitrogen fixation was assumed to occur only in oligotrophic environments, such as the subtropical gyres. In the framework of an international project, cruises took place in this area in February 2010 during a El Niño event and in March-April 2011 during a La Niña event. Results of these two cruises have confirmed that nitrogen fixation was unexpectedly active with an intensity comparable to those reported in oligotrophic areas
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Ferrand-Roumet, Catherine. "Importance et devenir du CO2 fixé par les racines nodulées de soja (Glycine max L. Merrill) : incidence sur l'estimation du coût carboné de la fixation de N2." Montpellier 2, 1990. http://www.theses.fr/1990MON20196.

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La fixation de co#2 par les racines nodulees de soja a ete mesuree en exposant les systemes racinaires a une atmosphere enrichie en #1#4co#2. Un suivi de l'importance et du devenir du #1#4c incorpore dans les plantes en fonction du temps apres le marquage, a permis d'etudier la dynamique d'utilisation du c fixe, en relation avec l'activite nitrogenase, et ce pour differents stades phenologiques et dans des conditions environnementales variables. Les resultats ont montre qu'une fraction importante du c fixe etait respiree par les racines nodulees et que les quantites de c incorporees dans les tissus (fixation nette), et sa repartition dans les organes, n'etaient pas directement liees a la fixation de n#2. Ceci nous a amene a augurer de l'existence d'une fixation racinaire, dont l'importance relative a ete estimee en comparant la fixation de co#2 de soja denodules et de soja nodules. Il a ete montre que la fixation racinaire contribuait pour plus de 50% a l'activite totale des racines nodulees et qu'il existait une relation entre fixation nodulaire de co#2 et activite nitrogenase. Une specificite des racines et des nodosites pour l'utilisation du c fixe a ete mise en evidence: le c fixe par les racines est principalement exporte vers les tiges; le c fixe par les nodosites est incorpore dans les racines et les nodosites. Dans ces organes une fraction de ce c est respiree; dans les nodosites, cette derniere fraction servirait de substrat respiratoire a la nitrogenase. La fixation de co#2 contribue pour 2,4 a 3,8% a la croissance en c de la plante, selon la periode du cycle, elle permet de recycler 8 a 37% du co#2 respire par les racines nodulees et 23 a 40% du co#2 respire par les nodosites pour leurs besoins de fixation de n#2. Le cout reel de la fixation de n#2, estime par le degagement total de co#2 (co#2 degage a l'exterieur des nodosites + co#2 recycle) est de 3,37
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Fumenia, Alain. "Dynamique spatiale et temporelle de la biomasse organique particulaire synthétisée dans une région océanique fortement influencée par la fixation de diazote atmosphérique (campagne océanographique OUTPACE dans le Pacifique tropical sud-ouest)." Electronic Thesis or Diss., Aix-Marseille, 2020. http://www.theses.fr/2020AIXM0173.

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Dans le Pacifique tropical sud-ouest (WTSP), la dynamique de la matière organique particulaire (MOP) est contrôlée par deux systèmes planctoniques à priori distincts. Dans la couche de mélange, la MOP produite présente un excès d’azote par rapport à la valeur attendue par la stœchiométrie de Redfield, avec un rapport N:P de 19±2. Nos résultats démontrent que l’intense fixation biologique de diazote (N2) mesurée dans cette région est la principale source d’azote nouveau capable de soutenir la production de MOP enrichie en N.Des relations statistiquement significatives ont été observées entre les valeurs de bbp et de NOP (POP) (R²=0.87 et 0.91, respectivement), permettant de définir des proxys optiques (PONopt et POPopt) de la biomasse organique particulaire. Sur toute la période d’étude (3 années), des augmentations significatives de PONopt sont observées uniquement dans l’Archipel Mélanésien et en période stratifiée. Cette production de biomasse autotrophe (et de particules associées) est soutenue que par l’apport d’azote via le processus de fixation de N2.À proximité du fond de la couche euphotique (Z01), dans les eaux de subsurface faiblement éclairées mais suffisamment riches en éléments nutritifs, un maximum de chlorophylle-a (Chla) de subsurface (SCML) est associé en permanence à un maximum de biomasse organique particulaire. Les résultats montrent qu’une production communautaire nette relativement faible mais positive (0.08 ± 0.01 mmol m-3 j-1 en moyenne) dans les couches faiblement éclairées entre Z01 et la profondeur à laquelle le PAR est réduit à 0.1% de sa valeur de surface (Z001)
In the Western Tropical South Pacific (WTSP), the dynamics of the particulate organic matter (POM) derives from two distinct planktonic systems in this oligotrophic region.In the mixed layer, the POM presents an excess of nitrogen with respect to the Redfield stoichiometry, with a N:P ratio of 19 ± 2. In this study, the high rates of biological dinitrogen fixation (N2) measured in this region has been pointed as the main source of new nitrogen, supporting the N-enriched POM production.Statistically significant relationships between bbp and PON (and POP) concentrations were established (R² = 0.87 and 0.91, respectively), allowing to define, for the first time, optical proxies (PONopt and POPopt) of particulate organic biomass. During the stratified periods of the studied period (3 years), significant increases in PONopt are observed only in the Melanesian Archipelago. These recurrent increases of PON concentrations in this area can only be supported by nitrogen input via the N2 fixation process.In the vicinity of the euphotic depth (Z01), a Subsurface Maximum of Chlorophyll-a (Chla) Layer (SCML) is permanently associated with a maximum of particulate organic biomass. By using O2 data collected by the float FA on a seasonal time scale, the calculated Net Community Production (0.08 ± 0.01 mmol m-3 d-1 on average) exhibited a low but positive value within the SCML, in the dimly lit layers between Z01 and the depth in which the measured PAR is reduced to 0.1% of its surface value (Z001)
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Masotti, Italo. "Dynamique des cyanobactéries fixatrices d'azote (Trichodesmium) : du Pacifique Sud-Ouest à l'océan global." Paris 6, 2007. http://www.theses.fr/2007PA066632.

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La fixation d’azote, N2 (N2fix) par les cyanobactéries, avec une introduction d’azote nouveau dans la couche éclairée, contrôlerait dans l’océan le déséquilibre actuel du cycle de l’azote, la productivité des régions les plus pauvres (oligotrophes) et la quantité de CO2 de l’atmosphère pompée par l’océan. Comment varie et quels sont les processus physiques et biogéochimiques qui contrôlent la distribution de cyanobactéries fixatrice d’azote et leur N2fix dans l’océan ? Quel est l’effet de rétroaction de la fixation de N2 sur la productivité et sur la pompe biologique de CO2? Afin de répondre à ces questions, seront évaluées la distribution et la N2fix due à la plus cosmopolite de cyanobactéries : Trichodesmium. En partant d’une étude focalisée dans le Pacifique sud-ouest, les résultats seront étendus à l’océan global. La stratégie est pluridisciplinaire et couple l’acquisition de nouvelles données in situ, in situ simulées, en laboratoire; satellitales (SeaWiFS) et le développement de modèles mathématiques. La N2fix de Trichodesmium est majoritaire dans : les régions oligotrophes de gyres anticycloniques subtropicales de grands bassins, qui associées à de convergences, restent pauvres en nutriments et en métaux et lors de conditions de forte stratification et fort éclairement (l’été et jusqu’à 20m). La fixation de N2 serait en conséquence plutôt contrôlée par la disponibilité lumineuse qui imposent les forts besoins énergétiques de ce mécanisme que par le fer. Se développant sous la forme d’accumulations étendues, ces cyanobactéries apparaissent comme un moteur biologique de fertilisation, qui conduit à la formation des oasis étendues de relative forte biomasse phytoplanctonique et forte séquestration de CO2. La fabrication de ces oasis modifie la vision traditionnelle d’extrême pauvreté et de faible pompage biologique de CO2 des océans oligotrophes.
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Carlsson, Georg. "Input of nitrogen from N2 fixation to northern grasslands /." Umeå : Dept. of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/200576.pdf.

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Griffiths, M. S. H. "Studies on the diurnal pattern of N2 fixation by cyanobacteria." Thesis, Swansea University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637179.

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Nitrogenase activity was observed in-situ at two sites dominated by cyanobacteria: Landimore Marsh, Gower, where the diazotroph was on Oscillatoria sp, and Cathole Cave, Gower where the diazotrophic species were Nostoc sp and Gloeothece sp. These sites were surveyed throughout the course of 12 months. The diurnal patterns of nitrogenase activity observed in-situ at each site were found to be characteristic of the cyanobacteria present, and to be identical to the patterns exhibited by laboratory cultures. No activity was observed at either site during the three coldest months of the year, November, December and January. In-situ, and in the laboratory, low temperatures proved to have a greater effect on nitrogenase activity than daylength or light intensity. Nevertheless, in the laboratory lengths of light period below 8-10h out of 24h were found to limit growth by cyanobacterial cultures, N2-fixing or otherwise. In cultures of Gloeothece or Scytonema maintained under alternating light and darkness N2 fixation in the dark increased markedly as the light intensity during the light period was increased from 5 to 80 uE/m2/s. In addition, these cyanobacteria proved better able to withstand high light intensities under alternating light and darkness than under continuous illumination. In Gloeothece temperatures of 37oC or above were found to be inhibitory to both nitrogenase activity and growth. This inhibition was not observed under anaerobic or microaerobic conditions. It therefore appeared that the inhibition was not due to an effect on nitrogenase itself, but rather to an effect on a mechanism for protecting nitrogenase against O2-inactivation. The patterns of acetylene reduction by cyanobacterial cultures maintained under alternating light and darkness, were unaffected by immobilization in agar cubes, alginate beads, or polyvinyl foam cubes. Furthermore, mixed populations which were unstable in liquid culture, were readily maintained in immobilized cultures.
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Zhao, Lihan. "Genetic modification of nodulation and N2 fixation in soybean / Lihan Zhao." [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18398.pdf.

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Du, C. "Studies of N2 fixation in batch and continuous cultures of Gloeothece." Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636741.

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Continuous cultures of Gloeothece have been established with a dilution rate of 0.015-1. Cell division in continuous cultures grown under alternating light and darkness depended on the length of the light period rather than on light intensity. Patterns of N2 fixation in continuous cultures were different from those in batch cultures when both were grown under alternating 12 hours light of intensity greater than 50 μE/m2/s and 12 hours darkness: continuous cultures fixed N2 mostly during the last half of light period, whilst batch cultures fixed N2 exclusively during the dark phase. In aerobic cultures of Gloeothece, whether N2-fixing or ammonium-grown, the light compensation point responded mainly to the prevailing rate of respiration. In aerobically N2-fixing cultures of Gloeothece, peaks of nitrogenase activity and light compensation point occurred simultaneously. In microaerobically grown N2-fixing cultures of Gloeothece exposed to alternating light and darkness, N2 fixation was exclusively found during the light phase, and was supported by photosynthesis. In vivo inhibition of nitrogenase activity in cultures of Gloeothece by EDTA and heat-shock may be mediated by inhibition of respiration. In aerobic, N2-fixing cultures of Gloeothece, cyanide-sensitive and -insensitive respiration was found: both showed a high rate during the dark phase. However, in ammonium-grown cultures, only cyanide-insensitive respiration was observed. In cyanide-treated N2-fixing and ammonium-grown cultures, the intracellular concentration of O2 did not change throughout a cycle of light and darkness, but in aerobic N2-fixing cultures, the relative intracellular concentration of O2 was close to zero when cultures entered the dark phase.
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Sihachakr, Davina. "Etude de N2/O2 sous pression." Paris 11, 2005. http://www.theses.fr/2005PA112036.

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Le but de cette thèse est d’identifier les paramètres pertinents pour la synthèse de nouveaux matériaux par pression à partir de mélanges de gaz moléculaires. Nous avons choisi un système école : les mélanges N2/O2. Dans une première partie, nous avons déterminé le diagramme de démixtion binaire à 300 K des mélanges N2/O2 sous pression. Une miscibilité totale en phase fluide est observée ainsi qu’une large miscibilité en phase solide. La phase solide présente une grande richesse allotropique. A partir des données de diffraction de rayons X, nous montrons que les structures de ces différentes solutions solides sont dérivées de celles des composants purs. Une dissymétrie du diagramme binaire indique cependant que les interactions N2-O2 sont très similaires de celles de N2-N2, mais sont très dissemblables de celles de O2-O2. Dans une deuxième partie, nous avons observé à partir des phases solides N2/O2, sous irradiation laser Nd :YAG, la synthèse du composé ionique NO+NO3-. Un nouveau type de structure en couche est affiné à partir des données de diffraction X. De plus, nous montrons que cette structure ouverte peut piéger des molécules O2 ce qui constitue une nouvelle classe de ‘clathrate’. Enfin, ce composé peut être récupéré à pression ambiante sous forme amorphe. Dans une dernière partie, nous montrons par des mesures de luminescence que le couplage du laser Nd:YAG avec les molécules O2 en phase condensée se fait par résonance avec la transition électronique de l’état triplet vers l’état singulet. Cet état excité est très réactif ce qui devrait permettre la synthèse d’autres matériaux sous pression à partir des mélanges contenant O2
The aim of this thesis is to identify the relevant parameters for the high-pressure synthesis of new materials from mixtures of molecular gases. We have chosen a model system: N2/O2 mixtures. In the first part of this document, we determined the binary phase diagram of N2/O2 under pressure at 300 K. In the fluid, a total miscibility is observed, and a large miscibility exists in the solid phases. The solid phase presents numerous allotropic forms. From the x-ray diffraction data, we show that the structures of those different solid solutions are related to those of pure components. A dissymmetry of the binary phase diagram however indicates that the N2-O2 interactions are very similar to the N2-N2 ones but are very different from the O2-O2 ones. In the second part of this document, we observed the synthesis of the ionic compound NO+NO3- from N2/O2 solid phases under Nd: YAG laser irradiation. A new type of layered structure is refined from the x-ray data. Moreover, we show that this opened structurecan trap O2 molecules what constitutes a new class of “clathrate”. Finally, this compound can be recovered at ambient pressure as an amorphous. In the last part of this document, we show from a luminescence study that the coupling of the Nd: YAG laser with O2 molecules in condensed phase is a resonant phenomenon with the electronic transition from the triplet state to the singlet state. This excited state is very reactive and the high-pressure synthesis of other materials should be possible from mixtures containing O2 molecules
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10

Bagchi, Rammyani. "Functional Characterization of Mtnip/latd’s Biochemical and Biological Function." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc407822/.

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Symbiotic nitrogen fixation occurs in plants harboring nitrogen-fixing bacteria within the plant tissue. The most widely studied association is between the legumes and rhizobia. In this relationship the plant (legumes) provides the bacteria (rhizobia) with reduced carbon derived from photosynthesis in exchange for reduced atmospheric nitrogen. This allows the plant to survive in soil, which is low in available of nitrogen. Rhizobia infect and enter plant root and reside in organs known as nodules. In the nodules the bacteria fix atmospheric nitrogen. The association between the legume, Medicago truncatula and the bacteria Sinorhizobium meliloti, has been studied in detail. Medicago mutants that have defects in nodulation help us understand the process of nitrogen fixation better. One such mutant is the Mtnip-1. Mtnip-1 plants respond to S. meliloti by producing abnormal nodules in which numerous aberrant infection threads are produced, with very rare rhizobial release into host plant cells. The mutant plant Mtnip-1 has an abnormal defense-like response in root nodules as well as defects in lateral root development. Three alleles of the Mtnip/latd mutants, Mtnip-1, Mtlatd and Mtnip-3 show different degrees of severity in their phenotype. Phylogenetic analysis showed that MtNIP/LATD encodes a protein belonging to the NRT1(PTR) family of nitrate, peptide, dicarboxylate and phytohprmone transporters. Experiments with Mtnip/latd mutants demonstrats a defective nitrate response associated with low (250 μM) external nitrate concentration rather than high (5 mM) nitrate concentration. This suggests that the mutants have defective nitrate transport. To test if MtNIP/LATD was a nitrate transporter, Xenopus laevis oocytes and Arabidopsis thaliana mutant plants Atchl1-5, defective in a major nitrate transporter AtNRT1.1(CHL1), were used as surrogate expression systems. Heterologous expression of MtNIP/LATD in X. laevis oocytes and Atchl1-5 mutant plants conferred on them the ability to take up nitrate from external media with high affinity, thus demonstrating that MtNIP/LATD was a high affinity nitrate transporter. Km for MtNIP/LATD was determined to be approximately160 μM in the X. laevis system and 113 μM in the Arabidopsis Atchl1-5 mutant lines thus supporting the previous observation of MtNIP/LATD being a high affinity nitrate transporter. X. laevis expressing the mutant Mtnip-1 and Mtlatd, were unable to transport nitrate. However X. laevis oocytes, expressing the less severe mutant allele Mtnip-3 were able to transport nitrate suggesting another role of the Mtnip/latd besides high affinity nitrate transport. Experimental evidence suggested that MtNIP/LATD might transport another substrate beside nitrate. MtNIP/LATD levels are regulated by phytohormones. Experiments performed with ABA (abscisic acid), IAA (indole acetic acid) and histidine as substrates in X. laevis system show that the MtNIP/LATD mRNA injected oocytes efflux IAA but do not transport histidine or ABA. When wild type A17 and mutant Mtnip-1 and Mtnip-3 plants, grown in the presence of different sources of nitrogen were screened in herbicide chlorate, a structural analog of nitrate, the A17 and Mtnip-3 mutant showed levels of susceptibility that was different from mutant Mtnip-1 lines. Evidence suggested that the amount of chlorate transported into the plants were regulated by the C:N status of the A17 and Mtnip-3 plants. This regulation was missing in the Mtnip-1 lines thus suggesting a sensor function of MtNIP/LATD gene.
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Books on the topic "Fixation de N2 [Azote]"

1

T, Wheeler C., ed. Nitrogen fixation in plants. Glasgow: Blackie, 1986.

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Dixon, R. O. D. Nitrogen fixation in plants. Glasgow: Blackie, 1986.

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1942-, Cole J. A., and Ferguson S. J. 1949-, eds. The nitrogen and sulphur cycles. Cambridge: Cambridge University Press, 1988.

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Landolfi, Angela, Beatriz Mouriño-Carballido, and Sophie Rabouille, eds. Marine N2 Fixation: Recent Discoveries and Future Challenges. Frontiers Media SA, 2021. http://dx.doi.org/10.3389/978-2-88966-689-8.

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(Editor), W. J. Broughton, and S. Puhler (Editor), eds. Nitrogen Fixation: Volume 4: Molecular Biology. Oxford University Press, USA, 1986.

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R, Smith S., Foundation for Water Research, and Water Research Centre, eds. Symbiotic N2-fixation and microbial activity in soils contaminated with heavy metals resulting from long term sewage application. Swindon: Water Research Centre, 1990.

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Kumar, Amit. Photocatalysis. Edited by Gaurav Sharma. Materials Research Forum LLC, 2021. http://dx.doi.org/10.21741/9781644901359.

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Photocatalysis is important in fighting environmental pollution, such as pharmaceutical effluents, dyes, pesticides and endocrine disruptors. It is also used for the production of clean energy, e.g. by way of hydrogen production from watersplitting, or CO2 conversion into fuels. Further, photocatalytic N2 fixation is promising for achieving sustainable ammonia synthesis. The book discusses new materials and reaction engineering techniques, such as heterojunction formations, composites, ion exchangers, photocatalytic membranes, etc.
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Cole, J. A., and S. J. Ferguson. SSGM 42 The Nitrogen and Sulpher (Society for General Microbiology Symposia). Cambridge University Press, 1988.

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Book chapters on the topic "Fixation de N2 [Azote]"

1

Zehr, Jonathan P., and Douglas G. Capone. "Factors Controlling N2 Fixation." In Marine Nitrogen Fixation, 95–115. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-67746-6_6.

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Zehr, Jonathan P., and Douglas G. Capone. "Fundamentals of N2 Fixation." In Marine Nitrogen Fixation, 9–29. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-67746-6_2.

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Zehr, Jonathan P., and Douglas G. Capone. "N2 Fixation in Ocean Basins." In Marine Nitrogen Fixation, 143–56. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-67746-6_8.

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Eaglesham, Allan R. J., Joan M. Ellis, William R. Evans, Darrell E. Fleischman, Mariangela Hungria, and Ralph W. F. Hardy. "The first photosynthetic N2-fixing Rhizobium: Characteristics." In Nitrogen Fixation, 805–11. Boston, MA: Springer US, 1990. http://dx.doi.org/10.1007/978-1-4684-6432-0_69.

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Speelman, Amy L., and Patrick L. Holland. "Sulfur-Supported Iron Complexes for Understanding N2 Reduction." In Nitrogen Fixation, 197–213. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/3418_2016_4.

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Vagnoli, L., M. C. Margheri, G. Allotta, and R. Materassi. "Morphological and Physiological Characterization of N2-Fixing Symbiotic Cyanobacteria." In Nitrogen Fixation, 571–72. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3486-6_126.

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Zehr, Jonathan P., and Douglas G. Capone. "History of Research on Marine N2 Fixation." In Marine Nitrogen Fixation, 31–41. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-67746-6_3.

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Arp, Daniel J. "H2 cycling in N2 fixation: Past, present, and future outlook." In Nitrogen Fixation, 67–76. Boston, MA: Springer US, 1990. http://dx.doi.org/10.1007/978-1-4684-6432-0_7.

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Ishida, Yutaka, and Hiroyuki Kawaguchi. "Reactivity of Group 5 Element Dinitrogen Complexes and N2-Derived Nitrides." In Nitrogen Fixation, 45–69. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/3418_2016_6.

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Zehr, Jonathan P., and Douglas G. Capone. "Biogeography of N2 Fixation in the Surface Ocean." In Marine Nitrogen Fixation, 117–41. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-67746-6_7.

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Conference papers on the topic "Fixation de N2 [Azote]"

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Ntatsi, Georgia, Christina Vrontani, Maria Vlachou, Eleni Rizopoulou, Christos Fotiadis, Andreas Ropokis, Anastasia Tampakaki, and Dimitrios Savvas. "Impact of different rhizobial strains and reduced N supply on growth and biological N2-fixation in cowpea grown hydroponically." In VII South-Eastern Europe Syposium on Vegetables & Potatoes. University of Maribor Press, 2017. http://dx.doi.org/10.18690/978-961-286-045-5.41.

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