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Sample records for nitrogen fixation island

  1. Nitrogen fixation rates associated with the invasive macroalgae Sargassum horneri around Catalina Island, CA

    Science.gov (United States)

    DeLiberto, A.

    2016-02-01

    Nitrogen fixation is an important process which allows organisms access to biologically unavailable dinitrogen gas. Bacteria, known as diazotrophs use the enzyme nitrogenase to convert N2 to NH3. These bacteria, including certain species of heterotrophic bacteria and cyanobacteria, can be symbiotically associated with marine macroalgae, facilitating nutrient cycling in oligotrophic regions. As many species within the genera Sargassum are associated with nitrogen fixation, this study hypothesized that nitrogenase activity would be associated with the benthic invasive Sargassum horneri on Catalina Island. In the past decade, Sargassum horneri, an invasive from Japan, has spread throughout the waters around Catalina Island. Using the acetylene reduction procedure using flame ionization detection, initial nitrogenase activity of S. horneri sampled from Indian Rock was observed. Nitrogen fixation rates increased with decomposition, particularly in dark/anaerobic treatments, suggesting the presence of heterotrophic bacteria. In addition, acetate additions greatly increase nitrogen fixation rates, once again indicating heterotrophic nitrogen fixing bacteria.

  2. Origin and Evolution of Nitrogen Fixation Genes on Symbiosis Islands and Plasmid in Bradyrhizobium

    Science.gov (United States)

    Okubo, Takashi; Piromyou, Pongdet; Tittabutr, Panlada; Teaumroong, Neung; Minamisawa, Kiwamu

    2016-01-01

    The nitrogen fixation (nif) genes of nodule-forming Bradyrhizobium strains are generally located on symbiosis islands or symbiosis plasmids, suggesting that these genes have been transferred laterally. The nif genes of rhizobial and non-rhizobial Bradyrhizobium strains were compared in order to infer the evolutionary histories of nif genes. Based on all codon positions, the phylogenetic tree of concatenated nifD and nifK sequences showed that nifDK on symbiosis islands formed a different clade from nifDK on non-symbiotic loci (located outside of symbiosis islands and plasmids) with elongated branches; however, these genes were located in close proximity, when only the 1st and 2nd codon positions were analyzed. The guanine (G) and cytosine (C) content of the 3rd codon position of nifDK on symbiosis islands was lower than that on non-symbiotic loci. These results suggest that nif genes on symbiosis islands were derived from the non-symbiotic loci of Bradyrhizobium or closely related strains and have evolved toward a lower GC content with a higher substitution rate than the ancestral state. Meanwhile, nifDK on symbiosis plasmids clustered with nifDK on non-symbiotic loci in the tree representing all codon positions, and the GC content of symbiotic and non-symbiotic loci were similar. These results suggest that nif genes on symbiosis plasmids were derived from the non-symbiotic loci of Bradyrhizobium and have evolved with a similar evolutionary pattern and rate as the ancestral state. PMID:27431195

  3. Enhancing biological nitrogen fixation

    Energy Technology Data Exchange (ETDEWEB)

    Danso, S.K.A.; Eskew, D.L. (Joint FAO/IAEA Div. of Isotope and Radiation Applications of Atomic Energy for Food and Agricultural Development, Vienna (Austria))

    1984-06-01

    Several co-ordinated research programmes (CRPs) conducted by the Soil Fertility, Irrigation and Crop Production Section of the Joint FAO/IAEA Division have concentrated on finding the most efficient way of applying nitrogen fertilizers to various crops, using nitrogen-15 (/sup 15/N) as a tracer. The findings of these studies have been adopted in many countries around the world, resulting in savings of nitrogen fertilizers worth many millions of dollars every year. More recently, the Section's CRPs have focused on enhancing the natural process of biological di-nitrogen fixation. The /sup 15/N isotope technique has proven to be very valuable in studies of the legume-Rhizobium symbiosis, allowing many more experiments than before to be done and yielding much new practical information. The Soils Section is now working to extend the use of the technique to other nitrogen-fixing symbioses.

  4. Eighth international congress on nitrogen fixation

    Energy Technology Data Exchange (ETDEWEB)

    1990-01-01

    This volume contains the proceedings of the Eighth International Congress on Nitrogen Fixation held May 20--26, 1990 in Knoxville, Tennessee. The volume contains abstracts of individual presentations. Sessions were entitled Recent Advances in the Chemistry of Nitrogen Fixation, Plant-microbe Interactions, Limiting Factors of Nitrogen Fixation, Nitrogen Fixation and the Environment, Bacterial Systems, Nitrogen Fixation in Agriculture and Industry, Plant Function, and Nitrogen Fixation and Evolution.

  5. Understanding Nitrogen Fixation

    Energy Technology Data Exchange (ETDEWEB)

    Paul J. Chirik

    2012-05-25

    synthesis of ammonia, NH{sub 3}, from its elements, H{sub 2} and N{sub 2}, via the venerable Haber-Bosch process is one of the most significant technological achievements of the past century. Our research program seeks to discover new transition metal reagents and catalysts to disrupt the strong N {triple_bond} N bond in N{sub 2} and create new, fundamental chemical linkages for the construction of molecules with application as fuels, fertilizers and fine chemicals. With DOE support, our group has discovered a mild method for ammonia synthesis in solution as well as new methods for the construction of nitrogen-carbon bonds directly from N{sub 2}. Ideally these achievements will evolve into more efficient nitrogen fixation schemes that circumvent the high energy demands of industrial ammonia synthesis. Industrially, atmospheric nitrogen enters the synthetic cycle by the well-established Haber-Bosch process whereby N{sub 2} is hydrogenated to ammonia at high temperature and pressure. The commercialization of this reaction represents one of the greatest technological achievements of the 20th century as Haber-Bosch ammonia is responsible for supporting approximately 50% of the world's population and serves as the source of half of the nitrogen in the human body. The extreme reaction conditions required for an economical process have significant energy consequences, consuming 1% of the world's energy supply mostly in the form of pollution-intensive coal. Moreover, industrial H{sub 2} synthesis via the water gas shift reaction and the steam reforming of methane is fossil fuel intensive and produces CO{sub 2} as a byproduct. New synthetic methods that promote this thermodynamically favored transformation ({Delta}G{sup o} = -4.1 kcal/mol) under milder conditions or completely obviate it are therefore desirable. Most nitrogen-containing organic molecules are derived from ammonia (and hence rely on the Haber-Bosch and H{sub 2} synthesis processes) and direct synthesis from

  6. Nitrogen Fixation in Cyanobacteria

    NARCIS (Netherlands)

    Stal, L.J.

    2008-01-01

    Cyanobacteria are oxygenic photosynthetic bacteria that are widespread in marine, freshwater and terrestrial environments and many of them are capable of fixing atmospheric nitrogen. But ironically, nitrogenase, the enzyme that is responsible for the reduction of N2, is extremely sensitive to O2.

  7. Eighth international congress on nitrogen fixation. Final program

    Energy Technology Data Exchange (ETDEWEB)

    1990-12-31

    This volume contains the proceedings of the Eighth International Congress on Nitrogen Fixation held May 20--26, 1990 in Knoxville, Tennessee. The volume contains abstracts of individual presentations. Sessions were entitled Recent Advances in the Chemistry of Nitrogen Fixation, Plant-microbe Interactions, Limiting Factors of Nitrogen Fixation, Nitrogen Fixation and the Environment, Bacterial Systems, Nitrogen Fixation in Agriculture and Industry, Plant Function, and Nitrogen Fixation and Evolution.

  8. Nitrogen fixation in denitrified marine waters.

    Directory of Open Access Journals (Sweden)

    Camila Fernandez

    Full Text Available Nitrogen fixation is an essential process that biologically transforms atmospheric dinitrogen gas to ammonia, therefore compensating for nitrogen losses occurring via denitrification and anammox. Currently, inputs and losses of nitrogen to the ocean resulting from these processes are thought to be spatially separated: nitrogen fixation takes place primarily in open ocean environments (mainly through diazotrophic cyanobacteria, whereas nitrogen losses occur in oxygen-depleted intermediate waters and sediments (mostly via denitrifying and anammox bacteria. Here we report on rates of nitrogen fixation obtained during two oceanographic cruises in 2005 and 2007 in the eastern tropical South Pacific (ETSP, a region characterized by the presence of coastal upwelling and a major permanent oxygen minimum zone (OMZ. Our results show significant rates of nitrogen fixation in the water column; however, integrated rates from the surface down to 120 m varied by ∼30 fold between cruises (7.5±4.6 versus 190±82.3 µmol m(-2 d(-1. Moreover, rates were measured down to 400 m depth in 2007, indicating that the contribution to the integrated rates of the subsurface oxygen-deficient layer was ∼5 times higher (574±294 µmol m(-2 d(-1 than the oxic euphotic layer (48±68 µmol m(-2 d(-1. Concurrent molecular measurements detected the dinitrogenase reductase gene nifH in surface and subsurface waters. Phylogenetic analysis of the nifH sequences showed the presence of a diverse diazotrophic community at the time of the highest measured nitrogen fixation rates. Our results thus demonstrate the occurrence of nitrogen fixation in nutrient-rich coastal upwelling systems and, importantly, within the underlying OMZ. They also suggest that nitrogen fixation is a widespread process that can sporadically provide a supplementary source of fixed nitrogen in these regions.

  9. Nitrogen Fixation in Denitrified Marine Waters

    Science.gov (United States)

    Fernandez, Camila; Farías, Laura; Ulloa, Osvaldo

    2011-01-01

    Nitrogen fixation is an essential process that biologically transforms atmospheric dinitrogen gas to ammonia, therefore compensating for nitrogen losses occurring via denitrification and anammox. Currently, inputs and losses of nitrogen to the ocean resulting from these processes are thought to be spatially separated: nitrogen fixation takes place primarily in open ocean environments (mainly through diazotrophic cyanobacteria), whereas nitrogen losses occur in oxygen-depleted intermediate waters and sediments (mostly via denitrifying and anammox bacteria). Here we report on rates of nitrogen fixation obtained during two oceanographic cruises in 2005 and 2007 in the eastern tropical South Pacific (ETSP), a region characterized by the presence of coastal upwelling and a major permanent oxygen minimum zone (OMZ). Our results show significant rates of nitrogen fixation in the water column; however, integrated rates from the surface down to 120 m varied by ∼30 fold between cruises (7.5±4.6 versus 190±82.3 µmol m−2 d−1). Moreover, rates were measured down to 400 m depth in 2007, indicating that the contribution to the integrated rates of the subsurface oxygen-deficient layer was ∼5 times higher (574±294 µmol m−2 d−1) than the oxic euphotic layer (48±68 µmol m−2 d−1). Concurrent molecular measurements detected the dinitrogenase reductase gene nifH in surface and subsurface waters. Phylogenetic analysis of the nifH sequences showed the presence of a diverse diazotrophic community at the time of the highest measured nitrogen fixation rates. Our results thus demonstrate the occurrence of nitrogen fixation in nutrient-rich coastal upwelling systems and, importantly, within the underlying OMZ. They also suggest that nitrogen fixation is a widespread process that can sporadically provide a supplementary source of fixed nitrogen in these regions. PMID:21687726

  10. Nitrogen supply of crops by biological nitrogen fixation. 2

    International Nuclear Information System (INIS)

    Jensen, E.S.; Andersen, A.J.; Soerensen, H.; Thomsen, J.D.

    1985-02-01

    In the present work the contributions from combined N-sources and symbiotic nitrogen fixation to the nitrogen supply of field-grown peas and field beans were evaluated by means of 15 N fertilizer dilution. The effect of N-fertilizer, supplied at sowing and at different stages of plant development, on nitrogen fixation, yield and protein production in peas, was studied in pot experiments. (author)

  11. Nitrogen fixation in trees - 1

    Energy Technology Data Exchange (ETDEWEB)

    Dobereiner, J.; Gauthier, D.L.; Diem, H.G.; Dommergues, Y.R.; Bonetti, R.; Oliveira, L.A.; Magalhaes, F.M.M.; Faria, S.M. de; Franco, A.A.; Menandro, M.S.

    1984-01-01

    Six papers are presented from the symposium. Dobereiner, J.; Nodulation and nitrogen fixation in leguminous trees, 83-90, (15 ref.), reviews studies on Brazilian species. Gauthier, D.L., Diem, H.G., Dommergues, Y.R., Tropical and subtropical actinorhizal plants, 119-136, (Refs. 50), reports on studies on Casuarinaceae. Bonetti, R., Oliveira, L.A., Magalhaes, F.M.M.; Rhizobium populations and occurrence of VA mycorrhizae in plantations of forest trees, 137-142, (Refs. 15), studies Amazonia stands of Cedrelinga catenaeformis, Calophyllum brasiliense, Dipteryx odorata, D. potiphylla, Carapa guianensis, Goupia glabra, Tabebuia serratifolia, Clarisia racemosa, Pithecellobium racemosum, Vouacapoua pallidior, Eperua bijuga, and Diplotropis species. Nodulation was observed in Cedrelinga catenaeformis and V. pallidior. Faria, S.M. de, Franco, A.A., Menandro, M.S., Jesus, R.M. de, Baitello, J.B.; Aguiar, O.T. de, Doebereiner, J; survey of nodulation in leguminous tree species native to southeastern Brazil, 143-153, (Refs. 7), reports on 119 species, with first reports of nodulation in the genera Bowdichia, Poecilanthe, Melanoxylon, Moldenhaurea (Moldenhawera), and Pseudosamanea. Gaiad, S., Carpanezzi, A.A.; Occurrence of Rhizobium in Leguminosae of silvicultural interest for south Brazil, 155-158, (Refs. 2). Nodulation is reported in Mimosa scabrella, Acacia mearnsii, A. longifolia various trinervis, Enterolobium contortisiliquum, and Erythrina falcata. Magalhaes, L.M.S., Blum, W.E.H., Nodulation and growth of Cedrelinga catanaeformis in experimental stands in the Manaus region - Amazonas, 159-164, (Refs. 5). Results indicate that C. catenaeformis can be used in degraded areas of very low soil fertility.

  12. Methanotrophy induces nitrogen fixation during peatland development

    Science.gov (United States)

    Larmola, Tuula; Leppänen, Sanna M.; Tuittila, Eeva-Stiina; Aarva, Maija; Merilä, Päivi; Fritze, Hannu; Tiirola, Marja

    2014-01-01

    Nitrogen (N) accumulation rates in peatland ecosystems indicate significant biological atmospheric N2 fixation associated with Sphagnum mosses. Here, we show that the linkage between methanotrophic carbon cycling and N2 fixation may constitute an important mechanism in the rapid accumulation of N during the primary succession of peatlands. In our experimental stable isotope enrichment study, previously overlooked methane-induced N2 fixation explained more than one-third of the new N input in the younger peatland stages, where the highest N2 fixation rates and highest methane oxidation activities co-occurred in the water-submerged moss vegetation. PMID:24379382

  13. Molecular nitrogen fixation and nitrogen cycle in nature

    Energy Technology Data Exchange (ETDEWEB)

    Virtanen, A I

    1952-01-01

    The origin of nitrogen oxides in the atmosphere is discussed. Evidently only a small proportion of the nitrate-and nitrite-nitrogen found in the precipitation is formed through electric discharges from molecular nitrogen, photochemical nitrogen fixation being probably of greater importance. Formation of nitrate nitrogen through atmospheric oxidation of nitrous oxide (N/sub 2/O) evaporating from the soil is also considered likely. Determination of nitrogen compounds at different altitudes is indispensable for gaining information of the N/sub 2/-fixation in the atmosphere and, in general, of the origin of nitrogen oxides and their decomposition. International cooperation is needed for this as well as for the quantitative determination of the nitrogen compounds removed from the soil by leaching and brought by waters into the seas.

  14. Nitrogen fixation in Red Sea seagrass meadows

    KAUST Repository

    Abdallah, Malak

    2017-05-01

    Seagrasses are key coastal ecosystems, providing many ecosystem services. Seagrasses increase biodiversity as they provide habitat for a large set of organisms. In addition, their structure provides hiding places to avoid predation. Seagrasses can grow in shallow marine coastal areas, but several factors regulate their growth and distribution. Seagrasses can uptake different kinds of organic and inorganic nutrients through their leaves and roots. Nitrogen and phosphorous are the most important nutrients for seagrass growth. Biological nitrogen fixation is the conversion of atmospheric nitrogen into ammonia by diazotrophic bacteria. This process provides a significant source of nitrogen for seagrass growth. The nitrogen fixation is controlled by the nif genes which are found in diazotrophs. The main goal of the project is to measure nitrogen fixation rates on seagrass sediments, in order to compare among various seagrass species from the Red Sea. Moreover, we will compare the fixing rates of the Vegetated areas with the bare sediments. This project will help to ascertain the role of nitrogen fixing bacteria in the development of seagrass meadows.

  15. 15N in biological nitrogen fixation studies

    International Nuclear Information System (INIS)

    Faust, H.

    1986-05-01

    A bibliography with 298 references on the use of the stable nitrogen isotope 15 N in the research on the biological fixation of dinitrogen is presented. The literature pertaining to this bibliography covers the period from 1975 to the middle of 1985. (author)

  16. Plasma catalysis for nitrogen fixation reactions

    NARCIS (Netherlands)

    Patil, B.S.; Wang, Q.; Hessel, V.; Lang, J.; Stankiewicz, A.; Stefanidis, G.

    2016-01-01

    The preferences for localized chemicals production and changing scenarios of renewable electricity cost gives a renewed boost to plasma-assisted valuable chemicals production. Especially, plasma-assisted nitrogen fixation for fertilizer production has the potential to largely change the energy

  17. Biological Nitrogen Fixation on Legume

    Directory of Open Access Journals (Sweden)

    Armiadi

    2009-03-01

    Full Text Available Nitrogen (N is one of the major limiting factors for crop growth and is required in adequate amount, due to its function as protein and enzyme components. In general, plants need sufficient nitrogen supply at all levels of growth, especially at the beginning of growth phase. Therefore, the availability of less expensive N resources would reduce the production cost. The increasing use of chemical fertilizer would probably disturb soil microorganisms, reduce the physical and chemical characteristics of soil because not all of N based fertilizer applied can be absorbed by the plants. Approximately only 50% can be used by crops, while the rest will be altered by microorganism into unavailable N for crops or else dissappear in the form of gas. Leguminous crops have the capacity to immobilize N2 and convert into the available N if innoculated with Rhizobium. The amount of N2 fixed varies depending on legume species and their environment.

  18. Variable Nitrogen Fixation in Wild Populus.

    Directory of Open Access Journals (Sweden)

    Sharon L Doty

    Full Text Available The microbiome of plants is diverse, and like that of animals, is important for overall health and nutrient acquisition. In legumes and actinorhizal plants, a portion of essential nitrogen (N is obtained through symbiosis with nodule-inhabiting, N2-fixing microorganisms. However, a variety of non-nodulating plant species can also thrive in natural, low-N settings. Some of these species may rely on endophytes, microorganisms that live within plants, to fix N2 gas into usable forms. Here we report the first direct evidence of N2 fixation in the early successional wild tree, Populus trichocarpa, a non-leguminous tree, from its native riparian habitat. In order to measure N2 fixation, surface-sterilized cuttings of wild poplar were assayed using both 15N2 incorporation and the commonly used acetylene reduction assay. The 15N label was incorporated at high levels in a subset of cuttings, suggesting a high level of N-fixation. Similarly, acetylene was reduced to ethylene in some samples. The microbiota of the cuttings was highly variable, both in numbers of cultured bacteria and in genetic diversity. Our results indicated that associative N2-fixation occurred within wild poplar and that a non-uniformity in the distribution of endophytic bacteria may explain the variability in N-fixation activity. These results point to the need for molecular studies to decipher the required microbial consortia and conditions for effective endophytic N2-fixation in trees.

  19. Nitrogen fixation on a coral reef

    Energy Technology Data Exchange (ETDEWEB)

    Mague, T.H.; Holm-Hansen, O.

    1975-06-01

    Benthic, heterocystous blue-green algae (genera Calothrix, Hormothamnion and Nostoc) from Eniwetok Atoll were found to reduce acetylene at rapid rates. Slight acetylene reduction was associated with samples of Rhizoclonium (Chlorophyceae) and Oscillatoria (a cyanophyte lacking heterocysts), but this may have been due to contamination by epiphytes. There was virtually no acetylene reduction by phytoplankton, and nutrient enrichment experiments failed to selectively increase the numbers or activity of N/sub 2/-fixing algae in surface water samples. The Nostoc required light for acetylene reduction. Nitrogen fixation by this species could have supplied up to 11 ..mu..g N/cm/sup 2//day to the ecosystem. (auth)

  20. Nitrogen fixation in four dryland tree species in central Chile

    International Nuclear Information System (INIS)

    Ovalle, C.; Arredondo, S.; Aronson, J.; Longeri, L.; Avendano, J.

    1998-01-01

    Results are presented from a 5-year experiment using 15 N-enriched fertilizer to determine N 2 fixation in four tree species on degraded soils in a Mediterranean-climate region of central Chile in which there are 5 months of drought. Species tested included three slow-growing but long-lived savannah trees native to southers South America, (acacia caven, Prosopic alba and P. chilensis; Mimosoideae), and Tagasaste (Chamaecytisus proliferus ssp. palmensis; Papilonoideae), a fast-growing but medium-lived tree from the Canary Islands. Tagasaste produced four- to twenty-fold more biomass than the other species, but showed declining N 2 fixation and biomass accumulation during the 5th year, corresponding to the juvenile-to-adult developmental transition. Nitrogen content was significantly higher in Tagasaste and Acacia caven than in the other species. The data revealed inter-specific differences in resource allocation and phenology of N 2 fixation rarely detailed for woody plants in dryland regions. (author)

  1. Two isotopic methods for estimation of soybean nitrogen fixation

    International Nuclear Information System (INIS)

    Domenach, A.-M.; Chalamet, Alain; Pachiaudi, Christiane

    1979-01-01

    Measurements of rate of nitrogen symbiotic fixation by Soybean were determined by two different methods: variations in the natural abundance of 15 N in plants; use of 'A' value determined from labelled nitrogen applications to the soil. The results from both methods were in good agreement. Rates of fixed nitrogen were similar when using non nodulated Soybean or Ray-Grass as reference [fr

  2. Two isotopic methods for estimation of soybean nitrogen fixation

    Energy Technology Data Exchange (ETDEWEB)

    Domenach, A M; Chalamet, A; Pachiaudi, C [Lyon-1 Univ., 69 - Villeurbanne (France)

    1979-07-16

    Measurements of rate of nitrogen symbiotic fixation by Soybean were determined by two different methods: variations in the natural abundance of /sup 15/N in plants; use of 'A' value determined from labelled nitrogen applications to the soil. The results from both methods were in good agreement. Rates of fixed nitrogen were similar when using non nodulated Soybean or Ray-Grass as reference.

  3. Plant densities and modulation of symbiotic nitrogen fixation in soybean

    Directory of Open Access Journals (Sweden)

    Marcos Javier de Luca

    2014-06-01

    Full Text Available Soybean nitrogen (N demands can be supplied to a large extent via biological nitrogen fixation, but the mechanisms of source/sink regulating photosynthesis/nitrogen fixation in high yielding cultivars and current crop management arrangements need to be investigated. We investigated the modulation of symbiotic nitrogen fixation in soybean [Glycine max (L. Merrill] at different plant densities. A field trial was performed in southern Brazil with six treatments, including non-inoculated controls without and with N-fertilizer, both at a density of 320,000 plants ha−1, and plants inoculated with Bradyrhizobium elkanii at four densities, ranging from 40,000 to 320,000 plants ha−1. Differences in nodulation, biomass production, N accumulation and partition were observed at stage R5, but not at stage V4, indicating that quantitative and qualitative factors (such as sunlight infrared/red ratio assume increasing importance during the later stages of plant growth. Decreases in density in the inoculated treatments stimulated photosynthesis and nitrogen fixation per plant. Similar yields were obtained at the different plant densities, with decreases only at the very low density level of 40,000 plants ha−1, which was also the only treatment to show differences in seed protein and oil contents. Results confirm a fine tuning of the mechanisms of source/sink, photosynthesis/nitrogen fixation under lower plant densities. Higher photosynthesis and nitrogen fixation rates are capable of sustaining increased plant growth.

  4. Use of 15N methodology to assess biological nitrogen fixation

    International Nuclear Information System (INIS)

    Hardarson, G.

    1990-01-01

    One of the most important characteristics of legumes are their ability in symbiosis with Rhizobium bacteria to fix atmospheric nitrogen for growth. For proper management and a full realization of the benefits of this plant-microbial association, it is necessary to estimate how much nitrogen is fixed under different conditions in the field. It is only after this is known that various factors can be manipulated so as to increase the amount and proportion of N a plant derives from biological fixation. A suitable method for accurately measuring the amount of N crops derive from fixation is therefore an important requirement in any programme aimed at maximizing biological nitrogen fixation. There are several methods available to measure N 2 fixation (Bergersen, 1980) based on (1) increment in N yield and plant growth, (2) nitrogen balance (3) acetylene reduction and (4) the use of isotopes of N. Only isotopic methods will be illustrated here. 20 refs, 2 figs, 9 tabs

  5. Cyanobacteria Occurrence and Nitrogen Fixation Rates in the ...

    African Journals Online (AJOL)

    Keywords: Cyanobacteria, Nitrogen Fixation, Seagrass, Seaweed Farming. Abstract—The .... during every sampling period, using a mercury thermometer and a ..... Capone, D.G. (1993) Determination of nitrogenase activity in aquatic samples ...

  6. Nitrogen fixation rates in the eastern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Ahmed, A.; Gauns, M.; Kurian, S.; Bardhan, P.; Pratihary, A.K.; Naik, H.; Shenoy, D.M.; Naqvi, S.W.A.

    The Arabian Sea experiences bloom of the diazotroph Trichodesmium during certain times of the year when optimal sea surface temperature and oligotrophic condition favour their growth. We measured nitrogen fixation rates in the euphotic zone during...

  7. Improving food and agricultural production. Thailand. Biological nitrogen fixation

    International Nuclear Information System (INIS)

    Bowen, G.D.

    1991-01-01

    The aim of the mission was to assist the counterpart scientists in the analysis and interpretation of data relating to nitrogen fixation studies on grain legumes. The report briefly summarizes the discussions that were held with the counterparts

  8. Nitrogen fixation by legumes in retorted shale

    Energy Technology Data Exchange (ETDEWEB)

    Hersman, L E; Molitoris, E; Klein, D A

    1981-01-01

    A study was made to determine whether retorted shale additions would significantly affect symbiotic N/sub 2/ fixation. Results indicate that small additions of the shale may stimulate plant growth but with higher concentrations plants are stressed, resulting in a decreased biomass and a compensatory effect of an increased number of nodules and N/sub 2/ fixation potential. (JMT)

  9. The importance of regulation of nitrogen fixation

    Science.gov (United States)

    Menge, D. N.

    2012-12-01

    I am not a proponent of including more detail in models simply because it makes them more realistic. More complexity increases the difficulty of model interpretation, so it only makes sense to include complexity if its benefit exceeds its costs. Biological nitrogen (N) fixation (BNF) is one process for which I feel the benefits of including greater complexity far outweigh the costs. I don't think that just because I work on BNF; I work on BNF because I think that. BNF, a microbial process carried out by free-living and symbiotic microbes, is the dominant N input to many ecosystems, the primary mechanism by which N deficiency can feed back to N inputs, and a main mechanism by which N surplus can develop. The dynamics of BNF, therefore, have huge implications for the rate of carbon uptake and the extent of CO2 fertilization, as well as N export to waterways and N2O emissions to the atmosphere. Unfortunately, there are serious deficiencies in our understanding of BNF. One main deficiency in our understanding is the extent to which various symbiotic N fixing organisms respond to imbalanced nutrition. Theory suggests that these responses, which I will call "strategies," have fundamental consequences for N fixer niches and ecosystem-level N and C cycling. Organisms that fix N regardless of whether they need it, a strategy that I will call "obligate," occupy post-disturbance niches and rapidly lead to N surplus. On the contrary, organisms that only fix as much N as they need, a "facultative" strategy, can occupy a wider range of successional niches, do not produce surplus N, and respond more rapidly to increased atmospheric CO2. In this talk I will show new results showing that consideration of these strategies could on its own explain the latitudinal distribution of symbiotic N fixing trees in North America. Specifically, the transition in N-fixing tree abundance from ~10% of basal area south of 35° latitude to ~1% of basal area north of 35° latitude that we observe

  10. Impact of Crab Bioturbation on Nitrogen-Fixation Rates in Red Sea Mangrove Sediment

    KAUST Repository

    Qashqari, Maryam S.

    2017-01-01

    be uptaken by plants. Hence, biological nitrogen fixation increases the input of nitrogen in the mangrove ecosystem. In this project, we focus on measuring the rates of nitrogen fixation on Red Sea mangrove (Avicennia marina) located at Thuwal, Saudi Arabia

  11. Buckminsterfullerenes: a non-metal system for nitrogen fixation.

    Science.gov (United States)

    Nishibayashi, Yoshiaki; Saito, Makoto; Uemura, Sakae; Takekuma, Shin-Ichi; Takekuma, Hideko; Yoshida, Zen-Ichi

    2004-03-18

    In all nitrogen-fixation processes known so far--including the industrial Haber-Bosch process, biological fixation by nitrogenase enzymes and previously described homogeneous synthetic systems--the direct transformation of the stable, inert dinitrogen molecule (N2) into ammonia (NH3) relies on the powerful redox properties of metals. Here we show that nitrogen fixation can also be achieved by using a non-metallic buckminsterfullerene (C60) molecule, in the form of a water-soluble C60:gamma-cyclodextrin (1:2) complex, and light under nitrogen at atmospheric pressure. This metal-free system efficiently fixes nitrogen under mild conditions by making use of the redox properties of the fullerene derivative.

  12. Biome-scale nitrogen fixation strategies selected by climatic constraints on nitrogen cycle.

    Science.gov (United States)

    Sheffer, Efrat; Batterman, Sarah A; Levin, Simon A; Hedin, Lars O

    2015-11-23

    Dinitrogen fixation by plants (in symbiosis with root bacteria) is a major source of new nitrogen for land ecosystems(1). A long-standing puzzle(2) is that trees capable of nitrogen fixation are abundant in nitrogen-rich tropical forests, but absent or restricted to early successional stages in nitrogen-poor extra-tropical forests. This biome-scale pattern presents an evolutionary paradox(3), given that the physiological cost(4) of nitrogen fixation predicts the opposite pattern: fixers should be out-competed by non-fixers in nitrogen-rich conditions, but competitively superior in nitrogen-poor soils. Here we evaluate whether this paradox can be explained by the existence of different fixation strategies in tropical versus extra-tropical trees: facultative fixers (capable of downregulating fixation(5,6) by sanctioning mutualistic bacteria(7)) are common in the tropics, whereas obligate fixers (less able to downregulate fixation) dominate at higher latitudes. Using a game-theoretic approach, we assess the ecological and evolutionary conditions under which these fixation strategies emerge, and examine their dependence on climate-driven differences in the nitrogen cycle. We show that in the tropics, transient soil nitrogen deficits following disturbance and rapid tree growth favour a facultative strategy and the coexistence of fixers and non-fixers. In contrast, sustained nitrogen deficits following disturbance in extra-tropical forests favour an obligate fixation strategy, and cause fixers to be excluded in late successional stages. We conclude that biome-scale differences in the abundance of nitrogen fixers can be explained by the interaction between individual plant strategies and climatic constraints on the nitrogen cycle over evolutionary time.

  13. Photosynthetic and nitrogen fixation capability in several soybean mutant lines

    International Nuclear Information System (INIS)

    Gandanegara, S.; Hendratno, K.

    1987-01-01

    Photosynthetic and nitrogen fixation capability in several soybean mutant lines. A greenhouse experiment has been carried out to study photosynthetic and nitrogen fixation capability of five mutant lines and two soybean varieties. An amount of 330 uCi of 14 CO 2 was fed to the plants including of the non-fixing reference crop (Chippewa non-nodulating isoline). Nitrogen fixation measurements was carried out using 15 N isotope dilution technique according to A-value concept. Results showed that beside variety/mutant lines, plant growth also has important role in photosynthetic and N fixing capability. Better growth and a higher photosynthetic capability in Orba, mutant lines nos. 63 and 65 resulted in a greater amount of N 2 fixed (mg N/plant) than other mutant lines. (author). 12 refs.; 5 figs

  14. Nitrogen fixation, denitrification, and ecosystem nitrogen pools in relation to vegetation development in the Subarctic

    DEFF Research Database (Denmark)

    Sørensen, Pernille Lærkedal; Jonasson, Sven Evert; Michelsen, Anders

    2006-01-01

    Nitrogen (N) fixation, denitrification, and ecosystem pools of nitrogen were measured in three subarctic ecosystem types differing in soil frost-heaving activity and vegetation cover. N2-fixation was measured by the acetylene reduction assay and converted to absolute N ecosystem input by estimates...... of conversion factors between acetylene reduction and 15N incorporation. One aim was to relate nitrogen fluxes and nitrogen pools to the mosaic of ecosystem types of different stability common in areas of soil frost movements. A second aim was to identify abiotic controls on N2-fixation by simultaneous...... measurements of temperature, light, and soil moisture. Nitrogen fixation rate was high with seasonal input estimated at 1.1 g N m2 on frostheaved sorted circles, which was higher than the total plant N content and exceeded estimated annual plant N uptake several-fold but was lower than the microbial N content...

  15. Nitrogen fixation improvement in Faidherbia albida

    International Nuclear Information System (INIS)

    Toure, O.; Dasilva, M.C.; Badji, S.; Dianda, M.; Ndoye, I.; Gueye, M.

    1998-01-01

    A greenhouse experiment investigated growth, N accumulation and N 2 fixation (using the 15 N-dilution method) by Faidherbia albida in comparison with three species of Acacia, with Parkia biglobosa and Tamarindus indica as non-fixing reference plants. Faidherbia albida was mediocre in comparison with A. seyel, therefore seven provenances of the former were examined in a second pot experiment to investigate within-species variability for the same performance components; a provenance from Kabrousse, Senegal, showed particular promise in terms of dry weight and N accumulation, and fixation of N. This promise was confirmed with a 15-month field experiment, but revealed that there is opportunity for further improvement in N 2 -fixing ability. Faidherbia albida is a slow-growing tree, therefore further field experiments with provenance Kabrousse should be longer term in scope. The data indicate that trenching of the 15 N-labelled area may not be necessary. (author)

  16. Nitrogen fixation and nodulation of soybean as affected by rhizobial ...

    African Journals Online (AJOL)

    The study evaluated the efficacy of different adhesives added to rhizobial seed inoculum on soybean nodulation and biological nitrogen fixation in a screen house and under field conditions. The experiment was a 6×3 factorial arranged in Completely Randomized Design and Randomized Complete Block Design for the pot ...

  17. Role of symbiotic nitrogen fixation in the improvement of legume ...

    African Journals Online (AJOL)

    Role of symbiotic nitrogen fixation in the improvement of legume productivity under stressed environments. R Serraj, J Adu-Gyamfi. Abstract. No Abstract. Full Text: EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT · http://dx.doi.org/10.4314/wajae.v6i1.45613.

  18. Cyanobacteria Occurrence and Nitrogen Fixation Rates in the ...

    African Journals Online (AJOL)

    The occurrence and biological nitrogen fixation rates of epiphytic and benthic diazotrophs were studied in seagrass meadows at sites with seaweed farms and at a control site without seaweed farms from two locations, Chwaka Bay and Jambiani, along the east coast of. Zanzibar. Ten species of cyanobacteria were ...

  19. Nitrogen fixation and nitrogenase activity of Azotobacter chroococcum

    NARCIS (Netherlands)

    Brotonegoro, S.

    1974-01-01

    The purpose of the present investigation was to study the effect of some chemical, physical and biological factors on growth, efficiency of nitrogen fixation and nitrogenase activity of Azotobacter chroococcum.

    From biochemical studies with cell-free

  20. Estimates of biological nitrogen fixation by Pterocarpus lucens in a ...

    African Journals Online (AJOL)

    Nitrogen (N2) fixation by Pterocarpus lucens in a natural semi arid ecosystem, in Ferlo, Senegal was estimated using 15N natural abundance (15N) procedure. Other non-fixing trees accompanying P. lucens in the same area were also investigated as control. Results showed an important variation of 15N in leaves between ...

  1. Nodulation and nitrogen fixation in common bean (Phaseolus vulgaris)

    African Journals Online (AJOL)

    Mamadou Gueye

    Nodulation and nitrogen fixation of field grown common bean (Phaseolus vulgaris) as influenced by fungicide seed treatment. Ndeye Fatou Diaw GUENE, Adama DIOUF and Mamadou GUEYE*. MIRCEN/ Laboratoire commun de microbiologie IRD-ISRA-UCAD, BP 1386, DAKAR, Senegal. Accepted 23 June 2003.

  2. Nitrogen fixation and induction of pseudo-nodules in grass

    International Nuclear Information System (INIS)

    Rasul, G.; Hassan, U.; Mehnaz, S.; Malik, K.A.

    1993-01-01

    The rice grown nitrogen depleted saline sols showed higher values for in-situ ARA. Isolations of N/sub 2/ fixing bacteria were carried out on soil Azotobacter was observed in plant rhizosphere. The 2,4-D (0.5 and 1 ppm) with diazo trophic bacteria induced nodule like structure on the wheat roots. The bacteria were found in nodules in the form of micro colonies or bacterial aggregates which were responsible for nitrogen fixation providing optimum 02 concentrations was incorporations /sup 15/N dilution data indicated that 125-46.5% atmosphere N was incorporated in nitrogen pool of inoculated plants. (author)

  3. Nitrogen fixation by legumes in retorted shale

    Energy Technology Data Exchange (ETDEWEB)

    Hersman, L E; Molitoris, E; Klein, D A

    1981-01-01

    Although a soil-shale mixture was employed as the growth medium in this experiment, the results presentd are applicable to the proposed method of disposal mentioned earlier. Under field conditions, when covering the retorted shale with topsoil, some mixing of these materials might occur in the plant root region. In addition, it has been demonstrated that buried shale negatively affects enzyme activities in overburden surface soil. The occurrence of either of those events could affect symbiotic N/sub 2/ fixation in a manner similar to that reported in this paper. Researchers conclude that due to the varied effects of retorted shale on the legumes tested, further evaluation of other legumes may be necessary. Additional research would be required to determine which legumes have potential use for reclamation of retorted shale.

  4. "Cold" Fixation: Reconciliation of Nitrogen Fixation Rates and Diazotroph Assemblages in the Arctic Ocean

    Science.gov (United States)

    Fong, A. A.; Waite, A.; Rost, B.; Richter, K. U.

    2016-02-01

    Measurements of biological nitrogen fixation are typically conducted in oligotrophic subtropical and tropical marine environments where concentrations of fixed inorganic nitrogen are low. To date, only a handful of nitrogen fixation studies have been conducted in high latitude marine environments, but further investigation is needed to resolve the distribution of cold ocean diazotrophic assemblages. Nitrogen fixation rates and nifH gene distributions were measured at seven stations from 5°E to 20°E, north of 81°N in the Arctic Ocean at the onset of summer 2015. Discrete water samples in ice-covered regions were collected from the sea surface to 200 m for 15N2-tracer additions and targeted nifH gene and transcript analyses. Previous work suggests that heterotrophic bacteria dominate diazotrophic communities in the Arctic Ocean. Therefore, additional nifH gene surveys of sinking particles were conducted to test for enrichment on organic matter-rich microenvironments. Together, these measurements aim to reconcile diazotrophic activity with microbial community composition, further elucidating how nitrogen fixers could impact current concepts in polar carbon and nutrient cycling.

  5. Bioelectrocatalyzed Nitrogen Fixation under Standard Conditions

    Science.gov (United States)

    2016-11-07

    containing nitrogenase) more electrochemically accessible . Samples were sonicated at 30% amplitude for either 30 seconds or 5 minutes. Electrodes were...resulted in the attached spreadsheet with VBA macros, ModelNitrogen08.xslm. These data are for the native distribution of species, without any species added...axis. The potential axis is set up in potentialaxiswithpHAlgae.xlsx, where different sheets (tabs) are described here. There is no VBA code in this

  6. Nitrogen fixation by the Azolla-Anabaena azollae symbiosis

    International Nuclear Information System (INIS)

    Becking, J.H.

    1985-01-01

    A concise outline is presented on the main characteristics of the Azolla association in relation to tropical wetland rice cultivation and the nitrogen economy of paddy soils. Due to the presence of a nitrogen fixing cyanobiont occurring in a special leaf cavity of the Azolla leaf, the water fern Azolla can grow in a nitrogen-deficient environment and is able to contribute considerably to the nitrogen status of the soil. An experimental set-up is presented for how the nitrogen-fixing capacity of Azolla plants can be measured in the field by means of the acetylene reduction assay using a rather simple glass vessel. A comparison was made between 15 N 2 fixation by Azolla and acetylene reduction of Azolla plants under identical conditions

  7. Transcriptional Profiling of Nitrogen Fixation in Azotobacter vinelandii▿†

    Science.gov (United States)

    Hamilton, Trinity L.; Ludwig, Marcus; Dixon, Ray; Boyd, Eric S.; Dos Santos, Patricia C.; Setubal, João C.; Bryant, Donald A.; Dean, Dennis R.; Peters, John W.

    2011-01-01

    Most biological nitrogen (N2) fixation results from the activity of a molybdenum-dependent nitrogenase, a complex iron-sulfur enzyme found associated with a diversity of bacteria and some methanogenic archaea. Azotobacter vinelandii, an obligate aerobe, fixes nitrogen via the oxygen-sensitive Mo nitrogenase but is also able to fix nitrogen through the activities of genetically distinct alternative forms of nitrogenase designated the Vnf and Anf systems when Mo is limiting. The Vnf system appears to replace Mo with V, and the Anf system is thought to contain Fe as the only transition metal within the respective active site metallocofactors. Prior genetic analyses suggest that a number of nif-encoded components are involved in the Vnf and Anf systems. Genome-wide transcription profiling of A. vinelandiicultured under nitrogen-fixing conditions under various metal amendments (e.g., Mo or V) revealed the discrete complement of genes associated with each nitrogenase system and the extent of cross talk between the systems. In addition, changes in transcript levels of genes not directly involved in N2fixation provided insight into the integration of central metabolic processes and the oxygen-sensitive process of N2fixation in this obligate aerobe. The results underscored significant differences between Mo-dependent and Mo-independent diazotrophic growth that highlight the significant advantages of diazotrophic growth in the presence of Mo. PMID:21724999

  8. Photosynthate partitioning and nitrogen fixation of alfalfa and birdsfoot trefoil

    International Nuclear Information System (INIS)

    Shieh, W.J.

    1985-01-01

    Nodule mass and number are usually correlated with rates of nitrogen fixation in legumes. Birdsfoot trefoil (Lotus corniculatus L.) with more than twice the nodule number and mass, however, fixes far less nitrogen than alfalfa (Medicago sativa L.) at the same age. In this research, photosynthesis and photosynthate partitioning and utilization in relation to nitrogen fixation of alfalfa and birdsfoot trefoil were examined in order to determine their relationship to nitrogen fixation potential. Photosynthate to nodules was studied using 14 CO 2 labeling techniques. Partitioning patterns were altered by shading and dark depletion treatments. Efficiency of photosynthate utilization was examined by determining turnover of 14 C photosynthate in nodule metabolites and by studying rates of cyanide-resistant and cyanide-sensitive O 2 uptake. Alfalfa nodule activity was greater than trefoil expressed on a hole pot or nodule dry weight basis. Both shading and dark treatments significantly reduced nodule activity as estimated by the acetylene reduction assay. Shoots of both species were found to be the dominant sinks for photosynthate. Percentage 14 C recovered in alfalfa roots was more than twice that of trefoil at 1,2,3,4 and 24 h after labeling. Greater relative specific radioactivity (RSA) in nodules of both species suggests that they were stronger sinks for current photosynthate than roots

  9. Nitrogen fixation in the tissues of ruminant

    International Nuclear Information System (INIS)

    Buttery, P.J.

    1990-01-01

    Protein metabolism in animals is in a constant state of flux, the processes of protein synthesis and protein breakdown acting against each other, and the balance between the two processes causing changes in the mass of protein in a tissue. Reduction in the diet reduces both protein synthesis and protein degradation unless the dietary depletion is severe and prolonged, when there is a marked increase in protein catabolism. The synthesis and degradation of protein can be manipulated by anabolic agents, thus increasing the efficiency of animals. While the use of these agents has met with success in many countries, it remains to be seen whether they will be useful in harsh environments. Lactation and pregnancy put an extra demand on the nitrogen economy of animals. Evidence indicates that the extra amino acids needed for milk production do not come from muscle protein breakdown. Many animals in harsh environments are infected with parasites; intestinal parasites reduce food intake and cause blood loss into the intestines. Associated with this is a general disruption of protein metabolism. In all these studies, isotopic techniques have played a vital role. Few studies have been conducted on nitrogen metabolism in the tissue of ruminants exposed to harsh environments (with one notable exception: rumen function studies, some of which are described elsewhere in the Proceedings of this Seminar). This lack of work on nitrogen metabolism of animals from the harsher environments has often made it necessary to extrapolate data obtained from animals found and maintained in the temperate zones to quite different environments and to animals maintained on quite different dietary regimens. Several examples of the use of isotopes in metabolic studies with animals to yield information of direct or potential relevance to the harsh environments are presented. (author). 23 refs. 1 fig. 6 tabs

  10. Biological nitrogen fixation in non-legume plants.

    Science.gov (United States)

    Santi, Carole; Bogusz, Didier; Franche, Claudine

    2013-05-01

    Nitrogen is an essential nutrient in plant growth. The ability of a plant to supply all or part of its requirements from biological nitrogen fixation (BNF) thanks to interactions with endosymbiotic, associative and endophytic symbionts, confers a great competitive advantage over non-nitrogen-fixing plants. Because BNF in legumes is well documented, this review focuses on BNF in non-legume plants. Despite the phylogenic and ecological diversity among diazotrophic bacteria and their hosts, tightly regulated communication is always necessary between the microorganisms and the host plant to achieve a successful interaction. Ongoing research efforts to improve knowledge of the molecular mechanisms underlying these original relationships and some common strategies leading to a successful relationship between the nitrogen-fixing microorganisms and their hosts are presented. Understanding the molecular mechanism of BNF outside the legume-rhizobium symbiosis could have important agronomic implications and enable the use of N-fertilizers to be reduced or even avoided. Indeed, in the short term, improved understanding could lead to more sustainable exploitation of the biodiversity of nitrogen-fixing organisms and, in the longer term, to the transfer of endosymbiotic nitrogen-fixation capacities to major non-legume crops.

  11. QTL analysis of symbiotic nitrogen fixation in a black bean RIL population

    Science.gov (United States)

    Dry bean (Phaseolus vulgaris L) acquires nitrogen (N) from the atmosphere through symbiotic nitrogen fixation (SNF) but it has a low efficiency to fix nitrogen. The objective of this study is to map the genes controlling nitrogen fixation in common bean. A mapping population consisting of 122 recomb...

  12. Seasonal patterns of periphyton nitrogen fixation in calcareous wetlands

    Science.gov (United States)

    Liao, X.; Inglett, P.

    2011-12-01

    Periphyton mats are an ecologically important component of the Everglades ecosystem and plays various vital ecological functions. However, nitrogen fixation of periphyton, has received little attention throughout much of the Everglades system. The objective of this study was to characterize the seasonal pattern of periphyton N2 fixation in the Hole-in-the-Donut (HID) of Florida Everglades, where farmed marl prairie wetlands have been restored through complete soil removal (CSR) to reduce nutrient levels. Two restored areas (i.e., cleared in 2000 and 2003) and a reference (natural and unfarmed) marl prairie wetland sites were selected in the HID. Seven times of sampling were performed across the wet and dry season during the 2010 and 2011. The annual fixed nitrogen was approximately 0.4gN m-2 yr-1 in the restored sites which was higher in the reference site (~0.2gN m-2 yr-1). All the three sites showed similar seasonal patterns of N2 fixation that is higher values were observed in the wet season; but the peak value was one month later in reference sits (i.e., September) comparing to the restored areas (i.e., July). The peak of periphyton AR rates in the 2000- and 2003-restored areas appeared in July (i.e., wet season) within the range of 20-79 nmols g-1dw h-1 and 31-53nmols g-1dw h-1, respectively. In contrast, the peak of reference site was observed in September with the range of 2-5 nmols g-1dw h-1. Stable N isotopic ratios (i.e., δ15N) also varied with time but didn't show consistent seasonal pattern as nitrogen fixation. N2 fixation positively correlated with periphyton total phosphorus (TP) and negatively correlated with total nitrogen and phosphorus molar ratios (TN:TP), indicating that N2 fixation would be a indicator of nutrient limitation. In general, δ15N was negatively correlated with nitrogenase activity but the correlation became weakened in the wet season, especially in the flooded July and September, which would be explained by other environmental

  13. Screening Prosopis (mesquite) germplasm for biomass production and nitrogen fixation

    Energy Technology Data Exchange (ETDEWEB)

    Felker, P.; Cannell, G.H.; Clark, P.R.; Osborn, J.F.

    1980-01-01

    The nitrogen-fixing trees of the genus Prosopis (mesquite or algaroba) are well adapted to the semi-arid and often saline regions of the world. These trees may produce firewood or pods for livestock food, they may stabilize sand dunes and they may enrich the soil by production of leaf litter supported by nitrogen fixation. A collection of nearly 500 Prosopis accessions representing North and South American and African germplasm has been established. Seventy of these accessions representing 14 taxa are being grown under field conditions where a 30-fold range in biomass productivity among accessions has been estimated. In a greehouse experiment, 13 Prosopis taxa grew on nitrogen-free medium nodulated, and had a 10-fold difference in nitrogen fixation (acetylene reduction). When Prosopis is propagated by seed the resulting trees are extremely variable in growth rate and presence or absence of thorns. Propagation of 6 Prosopis taxa by stem cuttings has been achieved with low success (1 to 10%) in field-grown plants and with higher success (50 to 100%) with young actively growing greenhouse plants.

  14. Nitrogen fixation by free-living organisms in rice soils. Studies with 15N

    International Nuclear Information System (INIS)

    Rao, V.R.; Charyulu, P.B.B.N.; Nayak, D.N.; Ramakrishna, C.

    1979-01-01

    Heterotrophic nitrogen fixation as influenced by water regime, organic matter, combined nitrogen and pesticides was investigated in several Indian rice soils by means of the 15 N 2 tracer technique. Soil submergence accelerated nitrogen fixation. Addition of cellulose to both non-flooded and flooded soils enhanced nitrogen fixation. Under submerged conditions, addition of sucrose, glucose and malate in that order stimulated nitrogen fixation in alluvial soil, while only sucrose enhanced nitrogen fixation in laterite soil. Nitrogen fixation in flooded alluvial and laterite soils decreased with increasing concentration of combined nitrogen. Nitrogen fixation was appreciable in acid sulphate and saline soils under both flooded and non-flooded conditions, despite high salinity and acidity. Application of certain pesticides at rates equivalent to recommended field level greatly influenced nitrogen fixation in flooded rice soils. Additions of benomyl (carbamate fungicide) and carbofuran (methyl carbamate insecticide) to alluvial and laterite soils resulted in significant stimulation of nitrogen fixation. Gamma-BHC stimulated nitrogen fixation only in alluvial soil, with considerable inhibition in a laterite soil. Nitrogen fixation by Azospirillum lipoferum was investigated by 15 N 2 . Large variations in 15 N 2 incorporation by A. lipoferum isolated from the roots of several rice cultivars was observed. Specific lines of rice harbouring A. lipoferum with high nitrogenase activity might be selected. Nitrogen fixed by heterotrophic organisms in a complex system such as soil could not be evaluated precisely. Indigenous nitrogen fixation in a flooded soil would be in the range of 5-10 kg N/ha, increasable 3 to 4-fold by appropriate fertilizers and cultural practices

  15. Seed protein and nitrogen fixation in chickpea mutant variety Hyprosola

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, H E; Gibson, A H; Oram, R N [CSIRO, Division of Plant Industry, Canberra ACT (Australia); Shaikh, M A.Q. [Bangladesh Institute of Nuclear Agriculture, Mymensingh (Bangladesh)

    1989-01-01

    Full text: 'Hyprosola' is a high yielding, high protein mutant cultivar obtained after gamma irradiation from the variety 'Faridpur-1'. The mutant yields 45 % more protein per unit area. The essential amino acid index is unchanged. It is likely that the high nutritional value in 'Hyprosola' seed protein arises from an increase in the albumin:globulin ratio. Nitrogen fixation rates of the mutant during the first 7 weeks of growth were found to be similar to 'Faridpur-1'. Under field conditions, the mutant may be able to nodulate more rapidly and more extensively than the parent variety. (author)

  16. Nitrogen cycling in summer active perennial grass systems in South Australia: Non-symbiotic nitrogen fixation

    NARCIS (Netherlands)

    Gupta, V.V.S.R.; Kroker, S.J.; Hicks, M.; Davoren, W.; Descheemaeker, K.K.E.; Llewellyn, R.

    2014-01-01

    Non-symbiotic nitrogen (N2) fixation by diazotrophic bacteria is a potential source for biological N inputs in non-leguminous crops and pastures. Perennial grasses generally add larger quantities of above- and belowground plant residues to soil, and so can support higher levels of soil biological

  17. Bacterial nitrogen fixation in sand bioreactors treating winery wastewater with a high carbon to nitrogen ratio.

    Science.gov (United States)

    Welz, Pamela J; Ramond, Jean-Baptiste; Braun, Lorenz; Vikram, Surendra; Le Roes-Hill, Marilize

    2018-02-01

    Heterotrophic bacteria proliferate in organic-rich environments and systems containing sufficient essential nutrients. Nitrogen, phosphorus and potassium are the nutrients required in the highest concentrations. The ratio of carbon to nitrogen is an important consideration for wastewater bioremediation because insufficient nitrogen may result in decreased treatment efficiency. It has been shown that during the treatment of effluent from the pulp and paper industry, bacterial nitrogen fixation can supplement the nitrogen requirements of suspended growth systems. This study was conducted using physicochemical analyses and culture-dependent and -independent techniques to ascertain whether nitrogen-fixing bacteria were selected in biological sand filters used to treat synthetic winery wastewater with a high carbon to nitrogen ratio (193:1). The systems performed well, with the influent COD of 1351 mg/L being reduced by 84-89%. It was shown that the nitrogen fixing bacterial population was influenced by the presence of synthetic winery effluent in the surface layers of the biological sand filters, but not in the deeper layers. It was hypothesised that this was due to the greater availability of atmospheric nitrogen at the surface. The numbers of culture-able nitrogen-fixing bacteria, including presumptive Azotobacter spp. exhibited 1-2 log increases at the surface. The results of this study confirm that nitrogen fixation is an important mechanism to be considered during treatment of high carbon to nitrogen wastewater. If biological treatment systems can be operated to stimulate this phenomenon, it may obviate the need for nitrogen addition. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Nitrogen Fixation in the Intertidal Sediments of the Yangtze Estuary: Occurrence and Environmental Implications

    Science.gov (United States)

    Hou, Lijun; Wang, Rong; Yin, Guoyu; Liu, Min; Zheng, Yanling

    2018-03-01

    Nitrogen fixation is a microbial-mediated process converting atmospheric dinitrogen gas to biologically available ammonia or other molecules, and it plays an important role in regulating nitrogen budgets in coastal marine ecosystems. In this study, nitrogen fixation in the intertidal sediments of the Yangtze Estuary was investigated using nitrogen isotope tracing technique. The abundance of nitrogen fixation functional gene (nifH) was also quantified. The measured rates of sediment nitrogen fixation ranged from 0.37 to 7.91 nmol N g-1 hr-1, while the abundance of nifH gene varied from 2.28 × 106 to 1.28 × 108 copies g-1 in the study area. The benthic nitrogen fixation was correlated closely to the abundance of nifH gene and was affected significantly by salinity, pH, and availability of sediment organic carbon and ammonium. It is estimated that sediment nitrogen fixation contributed approximately 9.3% of the total terrigenous inorganic nitrogen transported annually into the Yangtze estuarine and coastal environment. This result implies that the occurrence of benthic nitrogen fixation acts as an important internal source of reactive nitrogen and to some extent exacerbates nitrogen pollution in this aquatic ecosystem.

  19. Deepwater Nitrogen Fixation: Who's Doing it, Where, and Why?

    Science.gov (United States)

    Montoya, J. P.; Weber, S.; Vogts, A.; Voss, M.; Saxton, M.; Joye, S. B.

    2016-02-01

    Nitrogen availability frequently limits marine primary production and N2-fixation plays an important role in supporting biological production in surface waters of many oligotrophic regions. Although subsurface waters typically contain high concentrations of nitrate and other nutrients, measurements from a variety of oceanic settings show measurable, and at times high rates of N2-fixation in deep, dark waters below the mixed layer. We have explored the distribution of N2-fixation throughout the water column of the Gulf of Mexico (GoM) during a series of cruises beginning shortly after the Deepwater Horizon (DWH) spill in 2010 and continuing at roughly annual intervals. These cruises allowed us to sample oligotrophic waters across a range of depths, and to explore the connections between the C and N cycles mediated by release of oil and gas (petrocarbon) from natural seeps as well as anthropogenic sources (e.g., the DWH). We used stable isotope abundances (15N and 13C) in particles and zooplankton in combination with experimental measurements of N2-fixation and CH4 assimilation to assess the contribution of oil- and gas-derived C to the pelagic food web, and the impact of CH4 releases on the pelagic C and N cycles. Our isotopic measurements document the movement of petrocarbon into the pelagic food web, and our experiments revealed that high rates of N2-fixation were widespread in deep water immediately after the DWH incident, and restricted to the vicinity of natural seeps in subsequent years. Unfortunately, these approaches provided no insight into the organisms actually responsible for N2-fixation and CH4-assimilation. We used nano-scale Secondary Ion Mass Spectrometry (nanoSIMS) to image the organisms responsible for these processes, and molecular approaches to explore the diversity of methanotrophs and diazotrophs present in the system. The ability to resolve isotopic distributions on the scale of individual cells is a critical part of bridging the gap between

  20. Symbiotic nitrogen fixation and nitrate uptake by the pea crop

    International Nuclear Information System (INIS)

    Jensen, E.S.

    1986-08-01

    Symbiotic nitrogen fixation and nitrate uptake by pea plants (Pisum sativum L.) were studied in field and pot experiments using the 15 N isotope dilution technique and spring barley as a non-fixing reference crop. Barley, although not ideal, seemed to be a suitable reference for pea in the 15 N-technique. Maximum N 2 fixation activity of 10 kg N fixed per ha per day was reached around the flat pod growth stage, and the activity decreased rapidly during pod-filling. The pea crop fixed between 100 and 250 kg N ha -1 , corresponding to from 45 to 80 per cent of total crop N. The amount of symbiotically fixed N 2 depended on the climatic conditions in the experimental year, the level of soil mineral N and the pea cultivar. Field-grown pea took up 60 to 70 per cent of the N-fertilizer supplied. The supply of 50 kg NO 3 -N ha -1 inhibited the N 2 fixation approximately 15 per cent. Small amounts of fertilizer N, supplied at sowing (starter-N), slightly stimulated the vegetative growth of pea, but the yields of seed dry matter and protein were not significantly influenced. In the present field experiments the environmental conditions, especially the distribution of rainfall during the growth season, seemed to be more important in determining the protein and dry matter yield of the dry pea crop, than the ability of pea to fix nitrogen symbiotically. However, fertilizer N supplied to pot-grown pea plants at the flat pod growth stage or as split applications significantly increased the yield of seed dry matter and protein. (author)

  1. Global transcriptional analysis of nitrogen fixation and ammonium repression in root-associated Pseudomonas stutzeri A1501

    Directory of Open Access Journals (Sweden)

    Lu Wei

    2010-01-01

    Full Text Available Abstract Background Biological nitrogen fixation is highly controlled at the transcriptional level by regulatory networks that respond to the availability of fixed nitrogen. In many diazotrophs, addition of excess ammonium in the growth medium results in immediate repression of nif gene transcription. Although the regulatory cascades that control the transcription of the nif genes in proteobacteria have been well investigated, there are limited data on the kinetics of ammonium-dependent repression of nitrogen fixation. Results Here we report a global transcriptional profiling analysis of nitrogen fixation and ammonium repression in Pseudomonas stutzeri A1501, a root-associated and nitrogen-fixing bacterium. A total of 166 genes, including those coding for the global nitrogen regulation (Ntr and Nif-specific regulatory proteins, were upregulated under nitrogen fixation conditions but rapidly downregulated as early as 10 min after ammonium shock. Among these nitrogen fixation-inducible genes, 95 have orthologs in each of Azoarcus sp. BH72 and Azotobacter vinelandii AvoP. In particular, a 49-kb expression island containing nif and other associated genes was markedly downregulated by ammonium shock. Further functional characterization of pnfA, a new NifA-σ54-dependent gene chromosomally linked to nifHDK, is reported. This gene encodes a protein product with an amino acid sequence similar to that of five hypothetical proteins found only in diazotrophic strains. No noticeable differences in the transcription of nifHDK were detected between the wild type strain and pnfA mutant. However, the mutant strain exhibited a significant decrease in nitrogenase activity under microaerobic conditions and lost its ability to use nitrate as a terminal electron acceptor for the support of nitrogen fixation under anaerobic conditions. Conclusions Based on our results, we conclude that transcriptional regulation of nif gene expression in A1501 is mediated by the nif

  2. New insights into the evolutionary history of biological nitrogen fixation

    Directory of Open Access Journals (Sweden)

    Eric eBoyd

    2013-08-01

    Full Text Available Nitrogenase, which catalyzes the ATP-dependent reduction of dinitrogen (N2 to ammonia (NH3, accounts for roughly half of the bioavailable nitrogen supporting extant life. The fundamental requirement for fixed forms of nitrogen for life on Earth, both at present and in the past, has led to broad and significant interest in the origin and evolution of this fundamental biological process. One key question is whether the limited availability of fixed nitrogen was a factor in life’s origin or whether there were ample sources of fixed nitrogen produced by abiotic processes or delivered through the weathering of bolide impact materials to support this early life. If the latter, the key questions become what were the characteristics of the environment that precipitated the evolution of this oxygen sensitive process, when did this occur, and how was its subsequent evolutionary history impacted by the advent of oxygenic photosynthesis and the rise of oxygen in the Earth’s biosphere. Since the availability of fixed sources of nitrogen capable of supporting early life is difficult to glean from the geologic record, there are limited means to get direct insights into these questions. Indirect insights, however, can be gained by deep phylogenetic studies of nitrogenase structural gene products and additional gene products involved in the biosynthesis of the complex metal-containing prosthetic groups associated with this enzyme complex. Insights gained from such studies, as reviewed herein, challenge traditional models for the evolution of biological nitrogen fixation and provide the basis for the development of new conceptual models that explain the stepwise evolution of this highly complex and life sustaining process.

  3. Distribution of nitrogen fixation and nitrogenase-like sequences amongst microbial genomes

    Science.gov (United States)

    2012-01-01

    Background The metabolic capacity for nitrogen fixation is known to be present in several prokaryotic species scattered across taxonomic groups. Experimental detection of nitrogen fixation in microbes requires species-specific conditions, making it difficult to obtain a comprehensive census of this trait. The recent and rapid increase in the availability of microbial genome sequences affords novel opportunities to re-examine the occurrence and distribution of nitrogen fixation genes. The current practice for computational prediction of nitrogen fixation is to use the presence of the nifH and/or nifD genes. Results Based on a careful comparison of the repertoire of nitrogen fixation genes in known diazotroph species we propose a new criterion for computational prediction of nitrogen fixation: the presence of a minimum set of six genes coding for structural and biosynthetic components, namely NifHDK and NifENB. Using this criterion, we conducted a comprehensive search in fully sequenced genomes and identified 149 diazotrophic species, including 82 known diazotrophs and 67 species not known to fix nitrogen. The taxonomic distribution of nitrogen fixation in Archaea was limited to the Euryarchaeota phylum; within the Bacteria domain we predict that nitrogen fixation occurs in 13 different phyla. Of these, seven phyla had not hitherto been known to contain species capable of nitrogen fixation. Our analyses also identified protein sequences that are similar to nitrogenase in organisms that do not meet the minimum-gene-set criteria. The existence of nitrogenase-like proteins lacking conserved co-factor ligands in both diazotrophs and non-diazotrophs suggests their potential for performing other, as yet unidentified, metabolic functions. Conclusions Our predictions expand the known phylogenetic diversity of nitrogen fixation, and suggest that this trait may be much more common in nature than it is currently thought. The diverse phylogenetic distribution of nitrogenase

  4. Distribution of nitrogen fixation and nitrogenase-like sequences amongst microbial genomes

    Directory of Open Access Journals (Sweden)

    Dos Santos Patricia C

    2012-05-01

    Full Text Available Abstract Background The metabolic capacity for nitrogen fixation is known to be present in several prokaryotic species scattered across taxonomic groups. Experimental detection of nitrogen fixation in microbes requires species-specific conditions, making it difficult to obtain a comprehensive census of this trait. The recent and rapid increase in the availability of microbial genome sequences affords novel opportunities to re-examine the occurrence and distribution of nitrogen fixation genes. The current practice for computational prediction of nitrogen fixation is to use the presence of the nifH and/or nifD genes. Results Based on a careful comparison of the repertoire of nitrogen fixation genes in known diazotroph species we propose a new criterion for computational prediction of nitrogen fixation: the presence of a minimum set of six genes coding for structural and biosynthetic components, namely NifHDK and NifENB. Using this criterion, we conducted a comprehensive search in fully sequenced genomes and identified 149 diazotrophic species, including 82 known diazotrophs and 67 species not known to fix nitrogen. The taxonomic distribution of nitrogen fixation in Archaea was limited to the Euryarchaeota phylum; within the Bacteria domain we predict that nitrogen fixation occurs in 13 different phyla. Of these, seven phyla had not hitherto been known to contain species capable of nitrogen fixation. Our analyses also identified protein sequences that are similar to nitrogenase in organisms that do not meet the minimum-gene-set criteria. The existence of nitrogenase-like proteins lacking conserved co-factor ligands in both diazotrophs and non-diazotrophs suggests their potential for performing other, as yet unidentified, metabolic functions. Conclusions Our predictions expand the known phylogenetic diversity of nitrogen fixation, and suggest that this trait may be much more common in nature than it is currently thought. The diverse phylogenetic

  5. Recent developments in the structural organization and regulation of nitrogen fixation genes in Herbaspirillum seropedicae.

    Science.gov (United States)

    Pedrosa, F O; Benelli, E M; Yates, M G; Wassem, R; Monteiro, R A; Klassen, G; Steffens, M B; Souza, E M; Chubatsu, L S; Rigo, L U

    2001-10-04

    Herbaspirillum seropedicae is a nitrogen-fixing bacterium found in association with economically important gramineae. Regulation of nitrogen fixation involves the transcriptional activator NifA protein. The regulation of NifA protein and its truncated mutant proteins is described and compared with that of other nitrogen fixation bacteria. Nitrogen fixation control in H. seropedicae, of the beta-subgroup of Proteobacteria, has regulatory features in common with Klebsiella pneumoniae, of the gamma-subgroup, at the level of nifA expression and with rhizobia and Azospirillum brasilense, of the alpha-subgroup, at the level of control of NifA by oxygen.

  6. Regulation of Development and Nitrogen Fixation in Anabaena

    Energy Technology Data Exchange (ETDEWEB)

    James W. Golden

    2008-10-17

    The regulation of development and cellular differentiation is important for all multicellular organisms. The nitrogen-fixing filamentous cyanobacterium Anabaena (also Nostoc) sp. PCC 7120 (hereafter Anabaena) provides a model of multicellular microbial development and pattern formation. Anabaena reduces N2 to ammonia in specialized terminally differentiated cells called heterocysts. A one-dimensional developmental pattern of single heterocysts regularly spaced along filaments of photosynthetic vegetative cells is established to form a multicellular organism composed of these two interdependent cell types. This multicellular growth pattern, the distinct phylogeny of cyanobacteria, and the suspected antiquity of heterocyst development make this an important model system. Our long-term goal is to understand the regulatory network required for heterocyst development and nitrogen fixation. This project is focused on two key aspects of heterocyst regulation: one, the mechanism by which HetR controls the initiation of differentiation, and two, the cis and trans acting factors required for expression of the nitrogen-fixation (nif) genes. HetR is thought to be a central regulator of heterocyst development but the partners and mechanisms involved in this regulation are unknown. Our recent results indicate that PatS and other signals that regulate heterocyst pattern cannot interact, directly or indirectly, with a R223W mutant of HetR. We plan to use biochemical and genetic approaches to identify proteins that interact with the HetR protein, which will help reveal the mechanisms underlying its regulation of development. Our second goal is to determine how the nif genes are expressed. It is important to understand the mechanisms controlling nif genes since they represent the culmination of the differentiation process and the essence of heterocyst function. The Anabaena genome lacks the genes required for expression of nif genes present in other organisms such as rpoN (sigma 54

  7. Nitrogen Fixation Aligns with nifH Abundance and Expression in Two Coral Trophic Functional Groups

    KAUST Repository

    Pogoreutz, Claudia

    2017-06-28

    Microbial nitrogen fixation (diazotrophy) is a functional trait widely associated with tropical reef-building (scleractinian) corals. While the integral role of nitrogen fixation in coral nutrient dynamics is recognized, its ecological significance across different coral functional groups remains yet to be evaluated. Here we set out to compare molecular and physiological patterns of diazotrophy (i.e., nifH gene abundance and expression as well as nitrogen fixation rates) in two coral families with contrasting trophic strategies: highly heterotrophic, free-living members of the family Fungiidae (Pleuractis granulosa, Ctenactis echinata), and mostly autotrophic coral holobionts with low heterotrophic capacity (Pocilloporidae: Pocillopora verrucosa, Stylophora pistillata). The Fungiidae exhibited low diazotroph abundance (based on nifH gene copy numbers) and activity (based on nifH gene expression and the absence of detectable nitrogen fixation rates). In contrast, the mostly autotrophic Pocilloporidae exhibited nifH gene copy numbers and gene expression two orders of magnitude higher than in the Fungiidae, which coincided with detectable nitrogen fixation activity. Based on these data, we suggest that nitrogen fixation compensates for the low heterotrophic nitrogen uptake in autotrophic corals. Consequently, the ecological importance of diazotrophy in coral holobionts may be determined by the trophic functional group of the host.

  8. Nitrogen Fixation Aligns with nifH Abundance and Expression in Two Coral Trophic Functional Groups

    KAUST Repository

    Pogoreutz, Claudia; Radecker, Nils; Cardenas, Anny; Gä rdes, Astrid; Wild, Christian; Voolstra, Christian R.

    2017-01-01

    Microbial nitrogen fixation (diazotrophy) is a functional trait widely associated with tropical reef-building (scleractinian) corals. While the integral role of nitrogen fixation in coral nutrient dynamics is recognized, its ecological significance across different coral functional groups remains yet to be evaluated. Here we set out to compare molecular and physiological patterns of diazotrophy (i.e., nifH gene abundance and expression as well as nitrogen fixation rates) in two coral families with contrasting trophic strategies: highly heterotrophic, free-living members of the family Fungiidae (Pleuractis granulosa, Ctenactis echinata), and mostly autotrophic coral holobionts with low heterotrophic capacity (Pocilloporidae: Pocillopora verrucosa, Stylophora pistillata). The Fungiidae exhibited low diazotroph abundance (based on nifH gene copy numbers) and activity (based on nifH gene expression and the absence of detectable nitrogen fixation rates). In contrast, the mostly autotrophic Pocilloporidae exhibited nifH gene copy numbers and gene expression two orders of magnitude higher than in the Fungiidae, which coincided with detectable nitrogen fixation activity. Based on these data, we suggest that nitrogen fixation compensates for the low heterotrophic nitrogen uptake in autotrophic corals. Consequently, the ecological importance of diazotrophy in coral holobionts may be determined by the trophic functional group of the host.

  9. Impact of Crab Bioturbation on Nitrogen-Fixation Rates in Red Sea Mangrove Sediment

    KAUST Repository

    Qashqari, Maryam S.

    2017-05-01

    Mangrove plants are a productive ecosystem that provide several benefits for marine organisms and industry. They are considered to be a food source and habitat for many organisms. However, mangrove growth is limited by nutrient availability. According to some recent studies, the dwarfism of the mangrove plants is due to the limitation of nitrogen in the environment. Biological nitrogen fixation is the process by which atmospheric nitrogen is fixed into ammonium. Then, this fixed nitrogen can be uptaken by plants. Hence, biological nitrogen fixation increases the input of nitrogen in the mangrove ecosystem. In this project, we focus on measuring the rates of nitrogen fixation on Red Sea mangrove (Avicennia marina) located at Thuwal, Saudi Arabia. The nitrogen fixation rates are calculated by the acetylene reduction assay. The experimental setup will allow us to analyze the effect of crab bioturbation on nitrogen fixing rates. This study will help to better understand the nitrogen dynamics in mangrove ecosystems in Saudi Arabia. Furthermore, this study points out the importance of the sediment microbial community in mangrove trees development. Finally, the role of nitrogen fixing bacteria should be taken in account for future restoration activities.

  10. Sugar enrichment provides evidence for a role of nitrogen fixation in coral bleaching

    KAUST Repository

    Pogoreutz, Claudia; Radecker, Nils; Cardenas, Anny; Gä rdes, Astrid; Voolstra, Christian R.; Wild, Christian

    2017-01-01

    The disruption of the coral-algae symbiosis (coral bleaching) due to rising sea surface temperatures has become an unprecedented global threat to coral reefs. Despite decades of research, our ability to manage mass bleaching events remains hampered by an incomplete mechanistic understanding of the processes involved. In this study, we induced a coral bleaching phenotype in the absence of heat and light stress by adding sugars. The sugar addition resulted in coral symbiotic breakdown accompanied by a fourfold increase of coral-associated microbial nitrogen fixation. Concomitantly, increased N:P ratios by the coral host and algal symbionts suggest excess availability of nitrogen and a disruption of the nitrogen limitation within the coral holobiont. As nitrogen fixation is similarly stimulated in ocean warming scenarios, here we propose a refined coral bleaching model integrating the cascading effects of stimulated microbial nitrogen fixation. This model highlights the putative role of nitrogen-fixing microbes in coral holobiont functioning and breakdown.

  11. Sugar enrichment provides evidence for a role of nitrogen fixation in coral bleaching

    KAUST Repository

    Pogoreutz, Claudia

    2017-04-21

    The disruption of the coral-algae symbiosis (coral bleaching) due to rising sea surface temperatures has become an unprecedented global threat to coral reefs. Despite decades of research, our ability to manage mass bleaching events remains hampered by an incomplete mechanistic understanding of the processes involved. In this study, we induced a coral bleaching phenotype in the absence of heat and light stress by adding sugars. The sugar addition resulted in coral symbiotic breakdown accompanied by a fourfold increase of coral-associated microbial nitrogen fixation. Concomitantly, increased N:P ratios by the coral host and algal symbionts suggest excess availability of nitrogen and a disruption of the nitrogen limitation within the coral holobiont. As nitrogen fixation is similarly stimulated in ocean warming scenarios, here we propose a refined coral bleaching model integrating the cascading effects of stimulated microbial nitrogen fixation. This model highlights the putative role of nitrogen-fixing microbes in coral holobiont functioning and breakdown.

  12. Nitrogen fixation and molecular oxygen: comparative genomic reconstruction of transcription regulation in Alphaproteobacteria

    Directory of Open Access Journals (Sweden)

    Olga V Tsoy

    2016-08-01

    Full Text Available Biological nitrogen fixation plays a crucial role in the nitrogen cycle. An ability to fix atmospheric nitrogen, reducing it to ammonium, was described for multiple species of Bacteria and Archaea. Being a complex and sensitive process, nitrogen fixation requires a complicated regulatory system, also, on the level of transcription. The transcriptional regulatory network for nitrogen fixation was extensively studied in several representatives of the class Alphaproteobacteria. This regulatory network includes the activator of nitrogen fixation NifA, working in tandem with the alternative sigma-factor RpoN as well as oxygen-responsive regulatory systems, one-component regulators FnrN/FixK and two-component system FixLJ. Here we used a comparative genomics analysis for in silico study of the transcriptional regulatory network in 50 genomes of Alphaproteobacteria. We extended the known regulons and proposed the scenario for the evolution of the nitrogen fixation transcriptional network. The reconstructed network substantially expands the existing knowledge of transcriptional regulation in nitrogen-fixing microorganisms and can be used for genetic experiments, metabolic reconstruction, and evolutionary analysis.

  13. Manganese toxicity effects on nodulation and nitrogen fixation of beans (Phaseolus vulgaris L. ), in acid soils

    Energy Technology Data Exchange (ETDEWEB)

    Doebereiner, J

    1966-02-01

    Three greenhouse experiments were conducted to study manganese toxicity effects on the nitrogen fixing symbiosis of beans (Phaseolus vulgaris). Addition of 40 ppm of manganese to two acid soils affected nodulation and nitrogen fixation. Dependent on the Rhizobion strain either nodule numbers or efficiency in nitrogen fixation were reduced; the efficiency of one Rhizobium-host combination was more affected than another. Under less severe conditions of manganese toxicity, reduction of nodule numbers or of efficiency in nitrogen fixation could be compensated by an increase of nodule size. In the absence of manganese toxicity nodulation and nitrogen fixation of beans were abundant in a soil with pH 4.4. Naturally occurring manganese toxicity in a gray hydromorphic soil was eliminated by liming. The total nitrogen content of bean plants which were dependent on symbiotic nitrogen fixation decreased linearly with the logarithm of the manganese concentration in the plants. This did not happen when the plants were grown with mineral nitrogen. The role of manganese toxicity in the well known sensitivity to acid soil conditions of certain legumes and the importance of selection of manganese tolerant Rhizobium strains for the inoculation of beans in acid tropical soils, are discussed. 25 references, 1 figure, 6 tables.

  14. Biological nitrogen fixation is not a major contributor to the nitrogen demand of a commercially growth South African sugarcane cultivar

    NARCIS (Netherlands)

    Hoefsloot, G.; Termorshuizen, A.J.; Watt, D.A.; Cramer, M.D.

    2005-01-01

    It has previously been reported that endophytic diazotrophic bacteria contribute significantly to the nitrogen budgets of some graminaceous species. In this study the contribution of biological nitrogen fixation to the N-budget of a South African sugarcane cultivar was evaluated using 15N natural

  15. [Nitrogen fixation potential of biological soil crusts in southeast edge of Tengger Desert, Northwest China].

    Science.gov (United States)

    Zhang, Peng; Li, Xin-Rong; Zhang, Zhi-Shan; Pan, Yan-Xia; Liu, Yan-Mei; Su, Jie-Qiong

    2012-08-01

    Taking three typical types of biological soil crusts (BSCs), i.e., cyanobacterial-algal crust, lichen crust, and moss crust, in the southeast fringe of Tengger Desert as test objects, this paper studied their nitrogen fixation potential, seasonal fluctuation, and responses to the environmental factors from June 2010 to May 2011. During the whole study period, the nitrogenase activity (NA) of the cyanobacterial-algal, lichen, and moss crusts had significant difference, being 14-133, 20-101, and 4-28 micromol x m(-2) x h(-1), respectively, which indicated the critical role of the species composition of BSCs in nitrogen fixation. The NA of the three crust types had similar response characteristics to environmental factors. The NA had less correlation with the precipitation during the study period, but was positively correlated to the spring > summer > winter. The high air temperature in summer and the low air temperature (desert zone had nitrogen fixation capacity throughout the year, and the controlling effects of environmental factors on the nitrogen fixation were hierarchical. Water condition was the key factor affecting the nitrogen fixation rate and duration of the crusts, while under the conditions of sufficient water supply and carbon storage, heat condition dominated the crusts nitrogen fixation rate.

  16. Attempt at estimating the rate of symbiotic fixation of nitrogen in the Lupine by natural isotopic tracing (/sup 15/N)

    Energy Technology Data Exchange (ETDEWEB)

    Amarger, Noelle [INRA Centre de Recherches de Dijon, 21 (France). Lab. de Microbiologie des Sols; Mariotti, Andre; Mariotti, Francoise [Paris-6 Univ., 75 (France)

    1977-06-06

    The rate of nitrogen fixation by a Rhizobium-Leguminous plant pair has been determined by natural isotopic tracing (/sup 15/N). After determining the isotopic fractionation coefficients between atmospheric nitrogen and plant nitrogen on the one hand (epsilon=-0.9) and nitrogen of the substrate and plant nitrogen on the other hand (epsilon=-1.1), the rate of nitrogen fixation by way of mixed nutrition cultures was calculated. The method is more accurate than standard methods.

  17. Stimulation of nitrogen fixation in soddy-podzolic soils with fungi

    Science.gov (United States)

    Kurakov, A. V.; Prokhorov, I. S.; Kostina, N. V.; Makhova, E. G.; Sadykova, V. S.

    2006-09-01

    Stimulation of nitrogen fixation in soddy-podzolic soils is related to the hydrolytic activity of fungi decomposing plant polymers. It was found that the rate of nitrogen fixation upon the simultaneous inoculation of the strains of nitrogen-fixing bacteria Bacillus cereus var. mycoides and the cellulolytic fungus Trichoderma asperellum into a sterile soil enriched with cellulose or Jerusalem artichoke residues is two to four times higher than upon the inoculation of the strains of Bacillus cereus var. mycoides L1 only. The increase in the nitrogen fixation depended on the resistance of the substrates added into the soil to fungal hydrolysis. The biomass of the fungi decomposing plant polymers increased by two-four times. The nitrogen-fixing activity of the soil decreased when the growth of the fungi was inhibited with cycloheximide, which attested to a close correlation between the intensity of the nitrogen fixation and the decomposition of the plant polymers by fungi. The introduction of an antifungal antibiotic, together with starch or with plant residues, significantly (by 60-90%) decreased the rate of nitrogen fixation in the soll.

  18. Hydrologic Control on Bacterial Nitrogen Fixation in the Holocene Black Sea

    Science.gov (United States)

    Fulton, J. M.; Arthur, M. A.; Freeman, K. H.

    2008-12-01

    Stratified oceans of the Phanerozoic Oceanic Anoxic Events apparently were dominated by bacterial nitrogen fixation. Decreased marine N:P nutrient ratios resulting from increased denitrification and decreased phosphate burial efficiency under anoxic waters drove this nutrient regime. This model is upheld by the presence of cyanobacterial hopanoid biomarkers in sedimentary records and δ15N values indicative of nitrogen fixation. However, in the largest modern redox-stratified marine basin, the Black Sea, bacterial nitrogen fixation seems to be only a minor contributor to the nitrogen cycle. In this study, we use geochemical proxies to evaluate the role of bacterial nitrogen fixation during the deposition of the Holocene Black Sea sapropel, starting 7.8 ka. We report compound-specific nitrogen and carbon stable isotope values of pyropheophytin a, a chlorophyll degradation product, and bacteriochlorophyll e produced by green sulfur bacteria. We also present the surprising finding of scytonemin, a pigment produced only by filamentous cyanobacteria exposed to ultraviolet radiation, in certain intervals in these sediments. In the Holocene, nitrogen fixation in the Black Sea is most prominent during times of reduced river water influx. This directly decreases the external flux of nitrate into the surface waters. Reduced freshwater influx also decreases the volume of low salinity water dispersed around the sea by the Rim Current, allowing the chemocline to shoal along the margins. Previous geochemical studies have described this changing chemocline geometry. The exposure of shallow water sediments to anoxic waters further stimulates nitrogen fixation by releasing more phosphorus to the system. Nitrogen fixation is recorded in the sediments as bulk and compound-specific pyropheophytin a δ15N values near 0 ‰ and -5 ‰, respectively. We have also detected scytonemin in two intervals characterized by especially low δ15N values. This compound suggests abundant filamentous

  19. Low temperature delays timing and enhances the cost of nitrogen fixation in the unicellular cyanobacterium Cyanothece

    NARCIS (Netherlands)

    Brauer, V.S.; Stomp, M.; Rosso, C.; van Beusekom, S.A.M.; Emmerich, B.; Stal, L.J.; Huisman, J.

    2013-01-01

    Marine nitrogen-fixing cyanobacteria are largely confined to the tropical and subtropical ocean. It has been argued that their global biogeographical distribution reflects the physiologically feasible temperature range at which they can perform nitrogen fixation. In this study we refine this line of

  20. 15N dilution technique of assessing the contribution of nitrogen fixation to rice plant

    International Nuclear Information System (INIS)

    Ventura, Wilbur; Watanabe, Iwao

    1983-01-01

    An attempt to correlate the positive nitrogen balance in rice-soil system with the 15 N dilution in rice plants was made to see if isotope dilution can be used to assess the contribution of nitrogen fixation to the nitrogen nutrition of rice. 15 N ammonium sulfate and sucrose were added to the moist soil in pots to label biomass nitrogen fraction. The rice-soil system with higher nitrogen gain had lower 15 N content in the rice plants. When the surface of pots was covered with black cloths to suppress photodependent N 2 fixation, no significant nitrogen gain was observed. Significant gain was found in the rice-flooded soil system exposed to light, and the 15 N content of plants decreased in allowing the photodependent N 2 fixation by blue-green algae symbiosis. The contribution of plant nitrogen derived from photodependent N 2 fixation was estimated to be 20-30 % of the positive nitrogen gain in the system by the 15 N dilution technique using the rice-covered soil as reference system. (Mori, K.)

  1. /sup 15/N dilution technique of assessing the contribution of nitrogen fixation to rice plant

    Energy Technology Data Exchange (ETDEWEB)

    Ventura, W; Watanabe, Iwao [International Rice Research Inst., College, Laguna (Phillippines)

    1983-06-01

    An attempt to correlate the positive nitrogen balance in rice-soil system with the /sup 15/N dilution in rice plants was made to see if isotope dilution can be used to assess the contribution of nitrogen fixation to the nitrogen nutrition of rice. /sup 15/N ammonium sulfate and sucrose were added to the moist soil in pots to label biomass nitrogen fraction. The rice-soil system with higher nitrogen gain had lower /sup 15/N content in the rice plants. When the surface of pots was covered with black cloths to suppress photodependent N/sub 2/ fixation, no significant nitrogen gain was observed. Significant gain was found in the rice-flooded soil system exposed to light, and the /sup 15/N content of plants decreased in allowing the photodependent N/sub 2/ fixation by blue-green algae symbiosis. The contribution of plant nitrogen derived from photodependent N/sub 2/ fixation was estimated to be 20-30 % of the positive nitrogen gain in the system by the /sup 15/N dilution technique using the rice-covered soil as reference system.

  2. Transcriptome analysis of two recombinant inbred lines of common bean contrasting for symbiotic nitrogen fixation

    Science.gov (United States)

    Common bean (Phaseolus vulgaris L.) is able to fix atmospheric nitrogen (N2) through symbiotic nitrogen fixation (SNF). Effective utilization of existing variability for SNF in common bean for genetic improvement requires an understanding of underlying genes and molecular mechanisms. The utility of ...

  3. Global changes in transcription orchestrate metabolic differentiation during symbiotic nitrogen fixation in Lotus japonicus

    DEFF Research Database (Denmark)

    Colebatch, Gillian; Desbrosses, Guilhem; Ott, Thomas

    2004-01-01

    Research on legume nodule metabolism has contributed greatly to our knowledge of primary carbon and nitrogen metabolism in plants in general, and in symbiotic nitrogen fixation in particular. However, most previous studies focused on one or a few genes/enzymes involved in selected metabolic...

  4. Effect of vanadium and tungsten on nitrogen fixation and the growth of Medicago sativa

    Energy Technology Data Exchange (ETDEWEB)

    Jha, K K

    1969-01-01

    In sand culture, it was found that vanadium had no stimulatory effect on nitrogen content or the growth of Medicago sativa inoculated with an effective strain of Rhizobium meliloti or supplied with ammonium nitrate. At the level of 500 ppm it reduced the plant growth, the inhibitory effect being particularly severe on the root. On the other hand tungsten increased nitrogen fixation and the dry matter yield of the inoculated plants. The results are suggestive of a direct role of tungsten in symbiotic nitrogen fixation. 4 references, 2 tables.

  5. A mechanistic, globally-applicable model of plant nitrogen uptake, retranslocation and fixation

    Science.gov (United States)

    Fisher, J. B.; Tan, S.; Malhi, Y.; Fisher, R. A.; Sitch, S.; Huntingford, C.

    2008-12-01

    Nitrogen is one of the nutrients that can most limit plant growth, and nitrogen availability may be a controlling factor on biosphere responses to climate change. We developed a plant nitrogen assimilation model based on a) advective transport through the transpiration stream, b) retranslocation whereby carbon is expended to resorb nitrogen from leaves, c) active uptake whereby carbon is expended to acquire soil nitrogen, and d) biological nitrogen fixation whereby carbon is expended for symbiotic nitrogen fixers. The model relies on 9 inputs: 1) net primary productivity (NPP), 2) plant C:N ratio, 3) available soil nitrogen, 4) root biomass, 5) transpiration rate, 6) saturated soil depth,7) leaf nitrogen before senescence, 8) soil temperature, and 9) ability to fix nitrogen. A carbon cost of retranslocation is estimated based on leaf nitrogen and compared to an active uptake carbon cost based on root biomass and available soil nitrogen; for nitrogen fixers both costs are compared to a carbon cost of fixation dependent on soil temperature. The NPP is then allocated to optimize growth while maintaining the C:N ratio. The model outputs are total plant nitrogen uptake, remaining NPP available for growth, carbon respired to the soil and updated available soil nitrogen content. We test and validate the model (called FUN: Fixation and Uptake of Nitrogen) against data from the UK, Germany and Peru, and run the model under simplified scenarios of primary succession and climate change. FUN is suitable for incorporation into a land surface scheme of a General Circulation Model and will be coupled with a soil model and dynamic global vegetation model as part of a land surface model (JULES).

  6. Nitrogen fixation in different chickpea cultivars as affected by iron application N-15 Technique

    Energy Technology Data Exchange (ETDEWEB)

    Gadalla, A M; Soliman, S M; Abdelmonem, M [Soil and Water Dept., Atomic Energy Authority, Cairo, (Egypt)

    1995-10-01

    With development of new cultivars of winter chickpea, it became important to evaluate the potential of these cultivars to fix nitrogen from air, and the effect of different agronomic factors on this important process. Greenhouse experiment was conducted to screen five cultivars of chickpea for N 2- fixation ability as affected by iron application. These cultivars were Giza 1,2,531 and 88 as compared with L 3 which was developed from the genotype NEC 1055 by irradiation. N 2- fixation was estimated using N-15 technique. Plant materials were collected after 55 days from planing. Plants samples were analysed for total N-15 atom excess. Results show that Giza 88 gave the highest dry matter as well as nitrogen fixation. Nitrogen derived from air (NDFA) ranged from 27 to 50% due to variety difference and iron treatment. 1 fig., 3 tabs.

  7. Use of isotopes for increasing biological nitrogen fixation and yield of pastures

    International Nuclear Information System (INIS)

    Yao Yunyin

    1992-05-01

    The N-15 natural abundance and N-15 isotope dilution (ID) methods for measuring dinitrogen fixation and nitrogen transfer in alfalfa and alfalfa intercropped with meadow fescue were compared in three experiments. Although both methods gave essentially the same estimates the precision of the values obtained differed, and values obtained by the isotope dilution method were more precise. Similarly, the N-15 natural abundance method was not very suitable for detecting N transfer from legume to non-legume. Greater amounts of N transfer were detected by the ID method, and with a greater precision. Mixed cropping sometimes gave slight to high increases in % nitrogen fixation compared to alfalfa cropped alone. On the whole alfalfa was found to be a high nitrogen fixer, with fixation values from the second harvest onwards almost always greater than 80% and often close to 100%. 23 refs, 30 tabs

  8. Enhancement of root growth and nitrogen fixation in Trigonella by UV-exclusion from solar radiation.

    Science.gov (United States)

    Sharma, Sonika; Guruprasad, K N

    2012-12-01

    A field experiment was conducted to study the impact of solar UV on root growth and nitrogen fixation in Trigonella foenum-graecum. Plants were grown in iron mesh cages covered with polyester filters that could specifically cut off UV-B (280-315 nm) or UV-A + B (280-400 nm) part of the solar spectrum. The control plants were grown under a polythene filter transmissible to UV. Root biomass, number of nodules and nodule fresh weight were enhanced after exclusion of solar UV. Nitrogenase activity was significantly enhanced by 120% and 80% in the UV-B and UV-A + B excluded plants respectively. Along with nitrogenase there was concomitant increase in leghemoglobin and hemechrome content in the nodules after exclusion of solar UV. These components of sunlight limits nitrogen fixation and their elimination can enhance nitrogen fixation with agricultural advantages like reduction in the use of fertilizers. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  9. Nitrogen fixation in different chickpea cultivars as affected by iron application N-15 Technique

    International Nuclear Information System (INIS)

    Gadalla, A.M.; Soliman, S.M.; Abdelmonem, M.

    1995-01-01

    With development of new cultivars of winter chickpea, it became important to evaluate the potential of these cultivars to fix nitrogen from air, and the effect of different agronomic factors on this important process. Greenhouse experiment was conducted to screen five cultivars of chickpea for N 2- fixation ability as affected by iron application. These cultivars were Giza 1,2,531 and 88 as compared with L 3 which was developed from the genotype NEC 1055 by irradiation. N 2- fixation was estimated using N-15 technique. Plant materials were collected after 55 days from planing. Plants samples were analysed for total N-15 atom excess. Results show that Giza 88 gave the highest dry matter as well as nitrogen fixation. Nitrogen derived from air (NDFA) ranged from 27 to 50% due to variety difference and iron treatment. 1 fig., 3 tabs

  10. Enzymology of biological nitrogen fixation. Final report, May 1, 1987--April 30, 1996

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-05-01

    Biological nitrogen fixation is of central importance in the earth`s nitrogen economy. Fixation of nitrogen is accomplished by a variety of microorganisms, all of them procaryotic. Some operate independently and some function symbiotically or associatively with photosynthesizing plants. Biological nitrogen fixation is accomplished via the reaction: N{sub 2} + 8H{sup +} + 8e{sup {minus}} {yields} 2NH{sub 3} + H{sub 2}. This reaction requires a minimum of 16 ATP under ideal laboratory conditions, so it is obvious that the energy demand of the reaction is very high. When certain nitrogen-fixing organisms are supplied fixed nitrogen (e.g., ammonium) the organisms use the fixed nitrogen and turn off their nitrogenase system, thus conserving energy. When the fixed nitrogen is exhausted, the organism reactivates its nitrogenase. The system is turned off by dinitrogenase reductase ADP-ribosyl transferase (DRAT) and turned back on by dinitrogenase reductase-activating glycohydrolase (DRAG). The authors have investigated the details of how DRAT and DRAG are formed, how they function, and the genetics of their formation and operation.

  11. Breeding for traits supportive of nitrogen fixation in legumes

    International Nuclear Information System (INIS)

    Herridge, David F.

    2001-01-01

    As the potential economic benefits of enhancing dinitrogen (N 2 ) fixation of crop, pasture and forage legumes are substantial, the idea that legume breeding could play a role in enhancing N 2 fixation was advanced more than 50 years ago. Various programmes have sought to genetically improve a wide range of species, from pasture legumes such as red clover (Trifolium pratense) to the crop legumes like soybean (Glycine max) and common bean (Phaseolus vulgaris). In some the selection trait was yield, whilst in others it was high plant reliance on N 2 fixation (%Ndfa). A third strategy was to optimise legume nodulation through specific nodulation traits, e.g. mass, duration, promiscuous and selective nodulation. Plant genetic variation was sought from natural populations or created through mutagenesis. Although methods for assessing single plants and populations of plants for yield and %Ndfa varied over the years, it is now clear that measurements based on either 15 N or xylem solute analysis are the most reliable. Methodological issues as well as poor focus plagued many of the earlier programmes, since enhancing N 2 fixation essentially involves adapting legumes to fix more N when growing in N-poor soils. Programmes in which plant genotypes are inoculated with effective rhizobia and screened under conditions of low soil N maximise the symbiotic potential of the legume. (author)

  12. Management and quantification of nitrogen fixation in Leucaena leucocephala

    International Nuclear Information System (INIS)

    Safo, E.Y.

    1998-01-01

    The effects of pruning and age on N 2 fixation were studied using Leucaena leucocephala isoline K28, with Cassia siamea as the non-N 2 -fixing reference species, at a site of degraded soil fertility typical of much of the farming land in Ghana. The 15 N-dilution method was used to estimate N2 fixation. Cassia siamea consistently produced higher total biomass and total N yields than did L. leucocephala. The mean value for the fraction of N derived from fixation (%Ndfa) was higher for pruned L. leucocephala (36%) than for unpruned trees (18%). There was some underestimation of N 2 fixation as a result of using C. siamea as the reference, and because root N-contents were not determined. Strong, significant linear correlations were observed between foliar and whole-tree (weighted average) percent 15 N atom excess in unpruned L. leucocephala and C. siamea, suggesting that foliar 15 N enrichment can be used to accurately estimate %Ndfa. The results demonstrated that the 15 N-enrichment methodology can provide meaningful estimates of %Ndfa and total N 2 fixed for mixed tree plantations under field conditions, when adequate spacing is provided. (author)

  13. Effects of SO/sub 2/ on photosynthesis and nitrogen fixation

    Energy Technology Data Exchange (ETDEWEB)

    Haellgren, J E; Huss, K

    1975-06-15

    Responses of photosynthesis and nitrogen fixation to NaHSO/sub 3/ (10/sup -5/ to 5 x 10/sup -3/ M) were investigated in the lichen Stereocaulon paschale (L.) Fr. and the blue-green alga Anabaena cylindrica Lemmermann. The treatments were performed in buffered media with varying pH (5.8 to 8.1) and light conditions (0 to 32 W x m/sup -2/). The activities of the intact organisms were investigated, under the same environmental conditions, with /sup 14/C liquid scintillation and acetylene reduction techniques respectively. The nitrogen fixation proved to be more susceptible than photosynthesis, in both organisms, and in all cases treatments at pH 5.8 were more inhibitory than at higher pH-values. Treatment with 5 x 10/sup -4/ M NaHSO/sub 3/ at pH 5.8 caused no reduction of photosynthesis in S. paschale, while the inhibition of nitrogen fixation was 97%. For A. cylindrica the corresponding values were 40% and 75% respectively. Short-time treatments of A. cylindrica showed that the nitrogen fixation was more rapidly affected than photosynthesis. The inhibition of nitrogenase activity and CO/sub 2/-fixation was smaller in the dark and increased at higher light intensities. Both processes showed a good capacity for recovery after removal of the NaHSO/sub 3/ solution. Also the clumping ability of A. cylindrica was disturbed by NaHSO/sub 3/ treatments.

  14. Nitrogen fixation by cyanobacteria stimulates production in Baltic food webs.

    Science.gov (United States)

    Karlson, Agnes M L; Duberg, Jon; Motwani, Nisha H; Hogfors, Hedvig; Klawonn, Isabell; Ploug, Helle; Barthel Svedén, Jennie; Garbaras, Andrius; Sundelin, Brita; Hajdu, Susanna; Larsson, Ulf; Elmgren, Ragnar; Gorokhova, Elena

    2015-06-01

    Filamentous, nitrogen-fixing cyanobacteria form extensive summer blooms in the Baltic Sea. Their ability to fix dissolved N2 allows cyanobacteria to circumvent the general summer nitrogen limitation, while also generating a supply of novel bioavailable nitrogen for the food web. However, the fate of the nitrogen fixed by cyanobacteria remains unresolved, as does its importance for secondary production in the Baltic Sea. Here, we synthesize recent experimental and field studies providing strong empirical evidence that cyanobacterial nitrogen is efficiently assimilated and transferred in Baltic food webs via two major pathways: directly by grazing on fresh or decaying cyanobacteria and indirectly through the uptake by other phytoplankton and microbes of bioavailable nitrogen exuded from cyanobacterial cells. This information is an essential step toward guiding nutrient management to minimize noxious blooms without overly reducing secondary production, and ultimately most probably fish production in the Baltic Sea.

  15. Engineering Pseudomonas protegens Pf-5 for Nitrogen Fixation and its Application to Improve Plant Growth under Nitrogen-Deficient Conditions

    Science.gov (United States)

    Setten, Lorena; Soto, Gabriela; Mozzicafreddo, Matteo; Fox, Ana Romina; Lisi, Christian; Cuccioloni, Massimiliano; Angeletti, Mauro; Pagano, Elba; Díaz-Paleo, Antonio; Ayub, Nicolás Daniel

    2013-01-01

    Nitrogen is the second most critical factor for crop production after water. In this study, the beneficial rhizobacterium Pseudomonas protegens Pf-5 was genetically modified to fix nitrogen using the genes encoding the nitrogenase of Pseudomonas stutzeri A1501 via the X940 cosmid. Pf-5 X940 was able to grow in L medium without nitrogen, displayed high nitrogenase activity and released significant quantities of ammonium to the medium. Pf-5 X940 also showed constitutive expression and enzymatic activity of nitrogenase in ammonium medium or in nitrogen-free medium, suggesting a constitutive nitrogen fixation. Similar to Pseudomonas protegens Pf-5, Pseudomonas putida, Pseudomonas veronii and Pseudomonas taetrolens but not Pseudomonas balearica and Pseudomonas stutzeri transformed with cosmid X940 showed constitutive nitrogenase activity and high ammonium production, suggesting that this phenotype depends on the genome context and that this technology to obtain nitrogen-fixing bacteria is not restricted to Pf-5. Interestingly, inoculation of Arabidopsis, alfalfa, tall fescue and maize with Pf-5 X940 increased the ammonium concentration in soil and plant productivity under nitrogen-deficient conditions. In conclusion, these results open the way to the production of effective recombinant inoculants for nitrogen fixation on a wide range of crops. PMID:23675499

  16. Nitrogen fixation dynamics of two diazotrophic communities in Mono Lake, California

    Science.gov (United States)

    Oremland, R.S.

    1990-01-01

    Two types of diazotrophic microbial communities were found in the littoral zone of alkaline hypersaline Mono Lake, California. One consisted of anaerobic bacteria inhabiting the flocculent surface layers of sediments. Nitrogen fixation (acetylene reduction) by flocculent surface layers occurred under anaerobic conditions, was not stimulated by light or by additions of organic substrates, and was inhibited by O2, nitrate, and ammonia. The second community consisted of a ball-shaped association of a filamentous chlorophyte (Ctenocladus circinnatus) with diazotrophic, nonheterocystous cyanobacteria, as well as anaerobic bacteria (Ctenocladus balls). Nitrogen fixation by Ctenocladus balls was usually, but not always, stimulated by light. Rates of anaerobic dark fixation equaled those in the light under air. Fixation in the light was stimulated by 3-(3,4-dichlorophenyl)-1,1-dimethylurea and by propanil [N-(3,4-dichlorophenyl)propanamide]. 3-(3,4-Dichlorophenyl)-1,1-dimethyl urea-elicited nitrogenase activity was inhibited by ammonia (96%) and nitrate (65%). Fixation was greatest when Ctenocladus balls were incubated anaerobically in the light with sulfide. Dark anaerobic fixation was not stimulated by organic substrates in short-term (4-h) incubations, but was in long-term (67-h) ones. Areal estimates of benthic N2 fixation were measured seasonally, using chambers. Highest rates (~29.3 ??mol of C2H4 m-2 h-1) occurred under normal diel regimens of light and dark. These estimates indicate that benthic N2 fixation has the potential to be a significant nitrogen source in Mono Lake.

  17. Cyanobacterial nitrogen fixation in the ocean: Diversity, regulation and ecology

    NARCIS (Netherlands)

    Stal, L.J.; Zehr, J.P.; Herrero, A.; Flores, E.

    2008-01-01

    Nitrogen is an essential and major component of biomass. While virtually all life depends on combined forms of nitrogen that are usually limited in availability, some prokaryotes, including many groups of cyanobacteria, can use the ubiquitous atmospheric dinitrogen (N2). As photoautotrophic bacteria

  18. Use of 15N dilution method for screening soybean lines with high yield and high nitrogen fixation ability

    International Nuclear Information System (INIS)

    Li Haixian; Li Xinmin; Danso, S.K.A.

    1998-01-01

    15 N dilution method was used for screening soybean lines with high nitrogen fixation ability. Screened lines 1005, 8502, 2096, 943, 1454 and Dongnong-42 have high nitrogen fixation ability with their % Ndfa of about 70%. 1454 and 1555 are both high yield and high nitrogen fixation lines. The ability of nitrogen fixation was not related to the yield, but related to maturing time. The cultivars with different maturing time have different levels of nitrogen fixation ability. The longer the maturing period is, the greater the ability of nitrogen fixation it has. There were ten cultivars or lines used in the test of 1992 and 1994. Although the weather condition were greatly different between the two years the results of seven cultivars or lines were the same, indicating that nitrogen fixation ability of the soybean is stable with years. Using 15 N dilution method to estimate nitrogen fixation ability of soybean is reliable, however, the % Ndfa of lines 8502 and 2096 increased by 19% in 1994, a rainy year, indicating that a change in % Ndfa with a few varieties maybe caused by weather

  19. Effect of combined N applied at low level on the nitrogen fixation by grasses and contribution to nitrogen fertility in soil

    International Nuclear Information System (INIS)

    Yao Yunyin; Chen Ming; Ma Changlin

    1990-01-01

    This paper reports the study on the effect of combined N applied at low level on teh nitrogen fixation by alfalfa in monoculture and mixed culture with meadow fescue, and the effect on the absorption and utilization of indigenous soil nitrogen and nitrogen fertilizer. Amount of nitrogen fixed by alfalfa could be raised and duration of high peak of symbiotic nitrogen fixation activity could be extended when nitrogen fertilizer was applied reasonably. It was especially important for the early pastures or pastures with low supporting nitrogen capacity. Transfer of nitrogen fixed by alfalfa to meadow fescue occured in mixed culture. Nitrogen fixed from alfalfa was uptaken more easily than indigenous nitrogen in soil. Planting alfalfa could raise soil fertility significantly. Meadow fescue may be able to fix nitrogen from the air in some way. When combined N was appropriately applied to soil, on which alfalfa and meadow fescue had been planted, it could promote increasing nitrogen fertility in soil

  20. Functional ecology of free-living nitrogen fixation: A contemporary perspective

    Science.gov (United States)

    Reed, Sasha C.; Cleveland, Cory C.; Townsend, Alan R.

    2011-01-01

    Nitrogen (N) availability is thought to frequently limit terrestrial ecosystem processes, and explicit consideration of N biogeochemistry, including biological N2 fixation, is central to understanding ecosystem responses to environmental change. Yet, the importance of free-living N2 fixation—a process that occurs on a wide variety of substrates, is nearly ubiquitous in terrestrial ecosystems, and may often represent the dominant pathway for acquiring newly available N—is often underappreciated. Here, we draw from studies that investigate free-living N2 fixation from functional, physiological, genetic, and ecological perspectives. We show that recent research and analytical advances have generated a wealth of new information that provides novel insight into the ecology of N2 fixation as well as raises new questions and priorities for future work. These priorities include a need to better integrate free-living N2 fixation into conceptual and analytical evaluations of the N cycle's role in a variety of global change scenarios.

  1. Modeling the impact of iron and phosphorus limitations on nitrogen fixation in the Atlantic Ocean

    Directory of Open Access Journals (Sweden)

    R. R. Hood

    2007-07-01

    Full Text Available The overarching goal of this study is to simulate subsurface N* (sensu, Gruber and Sarmiento, 1997; GS97 anomaly patterns in the North Atlantic Ocean and determine the basin wide rates of N2-fixation that are required to do so. We present results from a new Atlantic implementation of a coupled physical-biogeochemical model that includes an explicit, dynamic representation of N2-fixation with light, nitrogen, phosphorus and iron limitations, and variable stoichiometric ratios. The model is able to reproduce nitrogen, phosphorus and iron concentration variability to first order. The latter is achieved by incorporating iron deposition directly into the model's detrital iron compartment which allows the model to reproduce sharp near surface gradients in dissolved iron concentration off the west coast of Africa and deep dissolved iron concentrations that have been observed in recent observational studies. The model can reproduce the large scale N* anomaly patterns but requires relatively high rates of surface nitrogen fixation to do so (1.8×1012 moles N yr−1 from 10° N–30° N, 3.4×1012 moles N yr−1 from 25° S–65° N. In the model the surface nitrogen fixation rate patterns are not co-located with subsurface gradients in N*. Rather, the fixed nitrogen is advected away from its source prior to generating a subsurface N* anomaly. Changes in the phosphorus remineralization rate (relative to nitrogen linearly determine the surface nitrogen fixation rate because they change the degree of phosphorus limitation, which is the dominant limitation in the Atlantic in the model. Phosphorus remineralization rate must be increased by about a factor of 2 (relative to nitrogen in order to generate subsurface N* anomalies that are comparable to the observations. We conclude that N2-fixation rate estimates for the Atlantic (and globally may need to be revised upward, which

  2. Riverine influence on nitrogen fixation in the upwelling region off Vietnam, South China Sea

    DEFF Research Database (Denmark)

    Voss, Maren; Bombar, Deniz; Loick, Natalie

    2006-01-01

    with the intermonsoon season and find that nitrogen fixation rates are app. 10 times higher during the monsoon season. However, this was not the case in the actual upwelling region - a 40-50 km wide strip along the coast - but further offshore, where the Mekong plume was noticeable. Therefore, we hypothesize...

  3. Arbuscular mycorrhiza stimulates biological nitrogen fixation in two Medicago spp. through omproved phosphorus acquisition

    Czech Academy of Sciences Publication Activity Database

    Püschel, David; Janoušková, Martina; Voříšková, Alena; Gryndlerová, H.; Vosátka, Miroslav; Jansa, J.

    2017-01-01

    Roč. 8, MAR 27 (2017), s. 1-12, č. článku no. 390. ISSN 1664-462X R&D Projects: GA ČR GA15-05466S Institutional support: RVO:67985939 Keywords : arbuscular mycorrhiza * biological nitrogen fixation * phosphorus uptake Subject RIV: EH - Ecology, Behaviour OBOR OECD: Ecology Impact factor: 4.298, year: 2016

  4. Estimation of nitrogen fixation in Leucaena leucocephala using 15N-enrichment methodologies

    Science.gov (United States)

    John A. Parrotta; Dwight D. Baker; Maurice Fried

    1994-01-01

    An estimation of biological nitrogen fixation by Leucaena leucocephala (Lam.) de Wit in monoculture and mixed-species plantations (with Casuarina equisetifolia L. ex J.R. & G. Forst., and Eucalyptus robusta Sm.) was undertaken over a two-year period in Puerto Rico using the 15N-enrichment...

  5. Application of 15N-enrichment methodologies to estimate nitrogen fixation in Casuarina equisetifolia

    Science.gov (United States)

    John A. Parrotta; Dwight D. Baker; Maurice Fried

    1994-01-01

    The 15N-enrichment technique for estimating biological nitrogen fixation in Casuarina equisetifolia J.R. & G. Forst. was evaluated under field conditions in single-species and mixed-species plantings (with a nonfixing reference species, Eucalyptus X robusta J.E. Smith) between...

  6. Regulation of Azorhizobium caulinodans ORS571 nitrogen fixation (NIF/FIX) genes

    NARCIS (Netherlands)

    Stigter, J.

    1994-01-01

    Biological nitrogen fixation is the microbial process by which atmospheric dinitrogen (N 2 ) is reduced to ammonia. In all microbes studied, dinitrogen reduction is catalyzed by a highly conserved enzyme complex, called nitrogenase.

  7. Biochar application rate affects biological nitrogen fixation in red clover conditional on potassium availability

    NARCIS (Netherlands)

    Mia, S.; van Groeningen, J.W.; Van de Voorde, T.F.J.; Oram, N.J.; Bezemer, T.M.; Mommer, Liesje; Jeffery, S.

    2014-01-01

    Increased biological nitrogen fixation (BNF) by legumes has been reported following biochar application to soils, but the mechanisms behind this phenomenon remain poorly elucidated. We investigated the effects of different biochar application rates on BNF in red clover (Trifolium pratense L.). Red

  8. Life cycle assessment of nitrogen fixation process assisted by plasma technology and incorporating renewable energy

    NARCIS (Netherlands)

    Anastasopoulou, A.; Butala, S.D.; Lang, J.; Hessel, V.; Wang, Q.

    2016-01-01

    The importance of nitrogen fixation is evident in every aspect of a human being’s life -from the synthesis of vital for all organisms nutrients and, in turn, the ecosystem conservation to the production of fertilizers, plastics and many other daily usage products. However, increasing concerns about

  9. Industrial applications of plasma, microwave and ultrasound techniques : nitrogen-fixation and hydrogenation reactions

    NARCIS (Netherlands)

    Hessel, V.; Cravotto, G.; Fitzpatrick, P.; Patil, B.S.; Lang, J.; Bonrath, W.

    2013-01-01

    The MAPSYN project (Microwave, Acoustic and Plasma assisted SYNtheses) aims at nitrogen-fixation reactions intensified by plasma catalysis and selective hydrogenations intensified by microwaves, possibly assisted by ultrasound. Energy efficiency is the key motif of the project and the call of the

  10. The effects of nitrogen fixation and plant growth-promoting in rice-diazotroph association

    International Nuclear Information System (INIS)

    Lin Fan; Wang Lu

    1999-05-01

    This is a review of studies on applications of the genetic engineered ammonium-tolerant diazotroph as an inoculum with the effects of nitrogen-fixation, plant growth-promoting and yield-increasing on rice and some crops by using 15 N tracer in mini-plot and field experiments in resent years

  11. Genome-wide association analysis of symbiotic nitrogen fixation in common bean

    Science.gov (United States)

    A genome-wide association study (GWAS) was conducted to explore the genetic basis of variation for symbiotic nitrogen fixation (SNF) and related traits in the Andean diversity panel (ADP) comprised of 259 common bean (Phaseolus vulgaris) genotypes. The ADP was evaluated for SNF and related traits in...

  12. Medicago truncatula copper transporter 1 (MtCOPT1) delivers copper for symbiotic nitrogen fixation.

    Science.gov (United States)

    Senovilla, Marta; Castro-Rodríguez, Rosario; Abreu, Isidro; Escudero, Viviana; Kryvoruchko, Igor; Udvardi, Michael K; Imperial, Juan; González-Guerrero, Manuel

    2018-04-01

    Copper is an essential nutrient for symbiotic nitrogen fixation. This element is delivered by the host plant to the nodule, where membrane copper (Cu) transporter would introduce it into the cell to synthesize cupro-proteins. COPT family members in the model legume Medicago truncatula were identified and their expression determined. Yeast complementation assays, confocal microscopy and phenotypical characterization of a Tnt1 insertional mutant line were carried out in the nodule-specific M. truncatula COPT family member. Medicago truncatula genome encodes eight COPT transporters. MtCOPT1 (Medtr4g019870) is the only nodule-specific COPT gene. It is located in the plasma membrane of the differentiation, interzone and early fixation zones. Loss of MtCOPT1 function results in a Cu-mitigated reduction of biomass production when the plant obtains its nitrogen exclusively from symbiotic nitrogen fixation. Mutation of MtCOPT1 results in diminished nitrogenase activity in nodules, likely an indirect effect from the loss of a Cu-dependent function, such as cytochrome oxidase activity in copt1-1 bacteroids. These data are consistent with a model in which MtCOPT1 transports Cu from the apoplast into nodule cells to provide Cu for essential metabolic processes associated with symbiotic nitrogen fixation. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

  13. Nitrogen fixation in arctic marine sediments: effect of oil and hydrocarbon fractions

    Energy Technology Data Exchange (ETDEWEB)

    Knowles, R; Wishart, C

    1977-06-01

    Nitrogen fixation (acetylene reduction) was measured in grab and core samples of sediments from the Beaufort Sea and Eskimo Lakes, Northwest Territories, Canada. Very low rates (about 25 mg N/m/sup 2/.year) were detected in untreated sediments. Activity was markedly stimulated by the addition of glucose, sucrose, lactose, mannitol and malate but much less so by acetate; negligible activity was supported by N-acetylglucosamine. There was no consistent effect of the presence or absence of oxygen. Nitrogen fixation potentials in glucose-supplemented sediment samples showed large variation between stations, between samples from the same station and between depths within single cores down to 18 cm. Weathered Normal Wells crude oil, hexane, decane, dodecane and hexadecane had no effect, stimulatory or inhibitory, on nitrogen fixation or carbon dioxide evolution. 1,2,4-trimethylbenzene caused complete inhibition of nitrogen fixation but only partial inhibition of CO/sub 2/ evolution. There was no evidence of utilization of any of the hydrocarbons tested during periods of over 30 days under the experimental conditions employed.

  14. Assessment of free-living nitrogen fixing microorganisms for commercial nitrogen fixation. [economic analysis of ammonia production

    Science.gov (United States)

    Stokes, B. O.; Wallace, C. J.

    1978-01-01

    Ammonia production by Klebsiella pneumoniae is not economical with present strains and improving nitrogen fixation to its theoretical limits in this organism is not sufficient to achieve economic viability. Because the value of both the hydrogen produced by this organism and the methane value of the carbon source required greatly exceed the value of the ammonia formed, ammonia (fixed nitrogen) should be considered the by-product. The production of hydrogen by KLEBSIELLA or other anaerobic nitrogen fixers should receive additional study, because the activity of nitrogenase offers a significant improvement in hydrogen production. The production of fixed nitrogen in the form of cell mass by Azotobacter is also uneconomical and the methane value of the carbon substrate exceeds the value of the nitrogen fixed. Parametric studies indicate that as efficiencies approach the theoretical limits the economics may become competitive. The use of nif-derepressed microorganisms, particularly blue-green algae, may have significant potential for in situ fertilization in the environment.

  15. Assessing nitrogen fixation in mixed- and single-species plantations of Eucalyptus globulus and Acacia mearnsii.

    Science.gov (United States)

    Forrester, David I; Schortemeyer, Marcus; Stock, William D; Bauhus, Jürgen; Khanna, Partap K; Cowie, Annette L

    2007-09-01

    Mixtures of Eucalyptus globulus Labill. and Acacia mearnsii de Wildeman are twice as productive as E. globulus monocultures growing on the same site in East Gippsland, Victoria, Australia, possibly because of increased nitrogen (N) availability owing to N(2) fixation by A. mearnsii. To investigate whether N(2) fixation by A. mearnsii could account for the mixed-species growth responses, we assessed N(2) fixation by the accretion method and the (15)N natural abundance method. Nitrogen gained by E. globulus and A. mearnsii mixtures and monocultures was calculated by the accretion method with plant and soil samples collected 10 years after plantation establishment. Nitrogen in biomass and soil confirmed that A. mearnsii influenced N dynamics. Assuming that the differences in soil, forest floor litter and biomass N of plots containing A. mearnsii compared with E. globulus monocultures were due to N(2) fixation, the 10-year annual mean rates of N(2) fixation were 38 and 86 kg ha(-1) year(-1) in 1:1 mixtures and A. mearnsii monocultures, respectively. Nitrogen fixation by A. mearnsii could not be quantified on the basis of the natural abundance of (15)N because such factors as mycorrhization type and fractionation of N isotopes during N cycling within the plant confounded the effect of the N source on the N isotopic signature of plants. This study shows that A. mearnsii fixed significant quantities of N(2) when mixed with E. globulus. A decline in delta(15)N values of E. globulus and A. mearnsii with time, from 2 to 10 years, is further evidence that N(2) was fixed and cycled through the stands. The increased aboveground biomass production of E. globulus trees in mixtures when compared with monocultures can be attributed to increases in N availability.

  16. Abiotic nitrogen fixation on terrestrial planets: reduction of NO to ammonia by FeS.

    Science.gov (United States)

    Summers, David P; Basa, Ranor C B; Khare, Bishun; Rodoni, David

    2012-02-01

    Understanding the abiotic fixation of nitrogen and how such fixation can be a supply of prebiotic nitrogen is critical for understanding both the planetary evolution of, and the potential origin of life on, terrestrial planets. As nitrogen is a biochemically essential element, sources of biochemically accessible nitrogen, especially reduced nitrogen, are critical to prebiotic chemistry and the origin of life. Loss of atmospheric nitrogen can result in loss of the ability to sustain liquid water on a planetary surface, which would impact planetary habitability and hydrological processes that shape the surface. It is known that NO can be photochemically converted through a chain of reactions to form nitrate and nitrite, which can be subsequently reduced to ammonia. Here, we show that NO can also be directly reduced, by FeS, to ammonia. In addition to removing nitrogen from the atmosphere, this reaction is particularly important as a source of reduced nitrogen on an early terrestrial planet. By converting NO directly to ammonia in a single step, ammonia is formed with a higher product yield (~50%) than would be possible through the formation of nitrate/nitrite and subsequent conversion to ammonia. In conjunction with the reduction of NO, there is also a catalytic disproportionation at the mineral surface that converts NO to NO₂ and N₂O. The NO₂ is then converted to ammonia, while the N₂O is released back in the gas phase, which provides an abiotic source of nitrous oxide.

  17. Biological nitrogen (N) fixation - The source of N nutrient to increase yield

    International Nuclear Information System (INIS)

    Heiling, M.; Hardarson, G.

    2006-01-01

    Nitrogen is an essential plant nutrient. It is the nutrient that is most commonly deficient, contributing to reduced agricultural yields throughout the world. Developing countries used more than 85 million metric tones of nitrogenous fertilizer in 2003, worth billions of US dollars. Such fertilizer expenditure can be significantly reduced by incorporating biological nitrogen fixed leguminous crops into a growing rotation. In leguminous crops, a symbiotic relationship between a bacterium called Rhizobium and legumes can provide large amounts of nitrogen to the plant and subsequently to soils where they are grown. In this process the bacteria form nodules on the root system and convert the nitrogen coming from air into molecules that can be absorbed by the plants. Beside their fertilizing properties, legumes are rich in protein and constitute a very important role in the human and animal nutrition. In the Soil Science Unit (SSU) of the FAO/IAEA Agriculture and Biotechnology Laboratory fellows from all over the world receive training in the use of 15 N stable isotope techniques to optimise the nitrogen fixation. Several parameters such as the placement of the nodules on the legume root system, the amount of soil mineral nitrogen and phosphorus fertilizer applied and the temperature have an impact on the amount of nitrogen fixed by the plant. It is therefore important to identify relative importance of these parameters on biological N fixation. The 15 N isotope dilution method is an appropriate technique to test the biological nitrogen fixation in the laboratory first. This useful knowledge can then be communicated to the farmers and can be tested under field conditions

  18. Enhancing the biological nitrogen fixation of leguminous crops ...

    African Journals Online (AJOL)

    Legumes have the ability to establish a symbiotic interaction with soil bacteria, collectively termed as rhizobia. These bacteria can enhance growth and development of associated crops by transferring atmospheric nitrogen into a form that is available for plant growth or by improving nutrient uptake through modulation of ...

  19. Potential for nitrogen fixation in fungus-growing termite symbiosis

    DEFF Research Database (Denmark)

    Sapountzis, Panagiotis; de Verges, Jane; Rousk, Kathrin

    2016-01-01

    Termites host a gut microbiota of diverse and essential symbionts that enable specialization on dead plant material; an abundant, but nutritionally imbalanced food source. To supplement the severe shortage of dietary nitrogen (N), some termite species make use of diazotrophic bacteria to fix atmo...

  20. Quantitative determination of nitrogen biological fixation by the N-15 isotopic method

    International Nuclear Information System (INIS)

    Basantes, Emilio; Trivelin, Paulo; Mui Tsai, Siu

    1993-01-01

    In order to quantify the biological nitrogen fixation (BNF) and to evaluate the mycorrhiza effect in the BNF, an experiment was carried on by applying 1 5 N -ammonium sulphate and mycorrhiza fungi to the soil. The treatments included legumes: mucuna negra(Stizolobium atterrinum Piper et Tracv) and caupi (Vigna unguiculoata L. Walp). Two control plants: non nodulating soybean (Glycine max L.Merril) and rice (Oryza sativa), were used for measuring the fixed N in the legumes by isotope dilution method. Both legumes and control plants assimmilated the same ammounts of nitrogen from the soil and fertilizer. The greater N content in the legumnes was determined as coming from the fixed nitrogen. Rice and non nodulating soybean showed to be good controls for measuring biological nitrogen fixation using isotopic dilution method. The values of fixed nitrogen for legumes calculated using rice as control plant were slightly greater than those with non nodulating soybean, nevertheless there were no significant statistical differences between the values. The mucuna fixed more N than caupi in both mycorrhiza treatments (76.7, 66.6 and 56. 7 per cent of N fixed, respectively). The mycorrhiza increased dry matter yield (13.84 per cent), accumulation of N in the plant(14.85 per cent N) and the biological N fixation (16.06 per cent N-fixed) in caupi

  1. Robust biological nitrogen fixation in a model grass-bacterial association.

    Science.gov (United States)

    Pankievicz, Vânia C S; do Amaral, Fernanda P; Santos, Karina F D N; Agtuca, Beverly; Xu, Youwen; Schueller, Michael J; Arisi, Ana Carolina M; Steffens, Maria B R; de Souza, Emanuel M; Pedrosa, Fábio O; Stacey, Gary; Ferrieri, Richard A

    2015-03-01

    Nitrogen-fixing rhizobacteria can promote plant growth; however, it is controversial whether biological nitrogen fixation (BNF) from associative interaction contributes to growth promotion. The roots of Setaria viridis, a model C4 grass, were effectively colonized by bacterial inoculants resulting in a significant enhancement of growth. Nitrogen-13 tracer studies provided direct evidence for tracer uptake by the host plant and incorporation into protein. Indeed, plants showed robust growth under nitrogen-limiting conditions when inoculated with an ammonium-excreting strain of Azospirillum brasilense. (11)C-labeling experiments showed that patterns in central carbon metabolism and resource allocation exhibited by nitrogen-starved plants were largely reversed by bacterial inoculation, such that they resembled plants grown under nitrogen-sufficient conditions. Adoption of S. viridis as a model should promote research into the mechanisms of associative nitrogen fixation with the ultimate goal of greater adoption of BNF for sustainable crop production. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

  2. Chasing after Non-cyanobacterial Nitrogen Fixation in Marine Pelagic Environments

    Directory of Open Access Journals (Sweden)

    Pia H. Moisander

    2017-09-01

    Full Text Available Traditionally, cyanobacterial activity in oceanic photic layers was considered responsible for the marine pelagic dinitrogen (N2 fixation. Other potentially N2-fixing bacteria and archaea have also been detected in the pelagic water column, however, the activity and importance of these non-cyanobacterial diazotrophs (NCDs remain poorly constrained. In this perspective we summarize the N2 fixation rates from recently published studies on photic and aphotic layers that have been attributed to NCD activity via parallel molecular measurements, and discuss the status, challenges, and data gaps in estimating non-cyanobacterial N2 fixation NCNF in the ocean. Rates attributed to NCNF have generally been near the detection limit thus far (<1 nmol N L−1 d−1. Yet, if considering the large volume of the dark ocean, even low rates of NCNF could make a significant contribution to the new nitrogen input to the ocean. The synthesis here shows that nifH transcription data for NCDs have been reported in only a few studies where N2 fixation rates were detected in the absence of diazotrophic cyanobacteria. In addition, high apparent diversity and regional variability in the NCDs complicate investigations of these communities. Future studies should focus on further investigating impacts of environmental drivers including oxygen, dissolved organic matter, and dissolved inorganic nitrogen on NCNF. Describing the ecology of NCDs and accurately measuring NCNF rates, are critical for a future evaluation of the contribution of NCNF to the marine nitrogen budget.

  3. Breeding food and forge legumes for enhancement of nitrogen fixation: a review

    International Nuclear Information System (INIS)

    Ali, A.; Hussain, S.; Qamar, I.A.; Khan, B.R.

    2000-01-01

    Nitrogen fixation in legume - root nodules requires the functioning of genes present in the Rhizobia that induce nodule-formation. The plant produces the nodules and the energy required for respiration. Genes in both Rhizobium and the plant are responsible for the efficient use of photosynthesis for N/sub 2/ fixation and assimilation of nitrogen. Genes from Rhizobium and legume hosts that are involved in the symbiosis are being identified, isolated and cloned, to facilitate the manipulation of either partner. The amounts of nitrogen fixed by grain-legumes vary appreciably, between and within, species and are also influenced by environment. With few exceptions, most legumes fix insufficient N/sub 2/ to support substantial seed-yields. Deficits between required N and the combined amounts provide by soil and fertilizer help in estimating the improvements in N/sub 2/ fixation which is possible through breeding. Since the symbiosis is a complex process, heritability of traits is weak, and most methods which estimate fixation are destructive, a breeding method that allows selection of replicated families rather than single plants is preferred. (author)

  4. The role of nitrogen fixation in neotropical dry forests: insights from ecosystem modeling and field data

    Science.gov (United States)

    Trierweiler, A.; Xu, X.; Gei, M. G.; Powers, J. S.; Medvigy, D.

    2016-12-01

    Tropical dry forests (TDFs) have immense functional diversity and face multiple resource constraints (both water and nutrients). Legumes are abundant and exhibit a wide diversity of N2-fixing strategies in TDFs. The abundance and diversity of legumes and their interaction with N2-fixing bacteria may strongly control the coupled carbon-nitrogen cycle in the biome and influence whether TDFs will be particularly vulnerable or uniquely adapted to projected global change. However, the importance of N2-fixation in TDFs and the carbon cost of acquiring N through symbiotic relationships are not fully understood. Here, we use models along with field measurements to examine the role of legumes, nitrogen fixation, and plant-symbiont nutrient exchanges in TDFs. We use a new version of the Ecosystem Demography (ED2) model that has been recently parameterized for TDFs. The new version incorporates plant-mycorrhizae interactions and multiple resource constraints (carbon, nitrogen, phosphorus, and water). We represent legumes and other functional groups found in TDFs with a range of resource acquisition strategies. In the model, plants then can dynamically adjust their carbon allocation and nutrient acquisition strategies (e.g. N2-fixing bacteria and mycorrhizal fungi) according to the nutrient limitation status. We test (i) the model's performance against a nutrient gradient of field sites in Costa Rica and (ii) the model's sensitivity to the carbon cost to acquire N through fixation and mycorrhizal relationships. We also report on simulated tree community responses to ongoing field nutrient fertilization experiments. We found that the inclusion of the N2-fixation legume plant functional traits were critical to reproducing community dynamics of Costa Rican field TDF sites and have a large impact on forest biomass. Simulated ecosystem fixation rates matched the magnitude and temporal patterns of field measured fixation. Our results show that symbiotic nitrogen fixation plays an

  5. Evaluation of the symbiotic nitrogen fixation in soybean by labelling of soil organic matter

    International Nuclear Information System (INIS)

    Ruschel, A.P.; Freitas, J.R. de; Vose, P.B.

    1982-01-01

    An experiment was carried out using the isotopic dilution method to evaluate symbiotic nitrogen fixation in soybean grown in soil labelled with 15 N enriched organic matter. Symbiotic N 2 -fixed was 71-76% of total N in the plant. Non nodulated soybean utilized 56-59% N from organic matter and 40% from soil. Roots of nodulated plants had lower NdN 2 than aereal plant parts. The advantage of using labelled organic matter as compared with 15 N-fertilizer addition in evaluating N 2 -fixation is discussed. (Author) [pt

  6. Biological invasion by Myrica faya in Hawaii: Plant demography, nitrogen fixation, ecosystem effects

    International Nuclear Information System (INIS)

    Vitousek, P.M.; Walker, L.R.

    1989-01-01

    Myrica faya, an introduced actinorhizal nitrogen fixer, in invading young volcanic sites in Hawaii Volcanoes National Park. We examined the population biology of the invader and ecosystem-level consequences of its invasion in open-canopied forests resulting from volcanic cinder-fall. Although Myrica faya is nominally dioecious, both males and females produce large amounts of fruit that are utilized by a number of exotic and native birds, particularly the exotic Zosterops japonica. In areas of active colonization, Myrica seed rain under perch trees of the dominant native Metrosideros polymorpha ranged from 6 to 60 seeds m -2 yr -1 ; no seeds were captured in the open. Planted seeds of Myrica also germinated an established better under isolated individuals of Metrosideros than in the open. Diameter growth of Myrica is > 15-fold greater than that of Metrosideros, and the Myrica population is increasing rapidly. Rates of nitrogen fixation were measured using the acetylene reduction assay calibrated with 15 N. Myrica nodules reduced acetylene at between 5 and 20 μmol g -1 h -1 , a rate that extrapolated to nitrogen fixation of 18 kg ha -1 in a densely colonized site. By comparison, all native sources of nitrogen fixation summed to 0.2 kg ha -1 yr -1 , and precipitation added -1 yr -1 . Measurements of litter decomposition and nitrogen release, soil nitrogen mineralization, and plant growth in bioassays all demonstrated that nitrogen fixed by Myrica becomes available to other organisms as well. We conclude that biological invasion by Myrica faya alters ecosystem-level properties in this young volcanic area; at least in this case, the demography and physiology of one species controls characteristics of a whole ecosystem

  7. Nitrogen fixation in rice systems: State of knowledge and future prospects

    International Nuclear Information System (INIS)

    Ladha, J.K.; Reddy, P.M.

    2001-01-01

    Rice is the most important cereal crop. In the next three decades, the world will need to produce about 60% more rice than today's global production to feed the extra billion people. Nitrogen is the major nutrient limiting rice production. Development of fertilizer-responsive varieties in the Green Revolution, coupled with the realization by farmers of the importance of nitrogen, has led to high rates of N fertilizer use on rice. Increased future demand for rice will entail increased application of fertilizer N. Awareness is growing, however, that such an increase in agricultural production needs to be achieved without endangering the environment. To achieve food security through sustainable agriculture, the requirement for fixed nitrogen must increasingly met by biological nitrogen fixation (BNF) rather than by using nitrogen fixed industrially. It is thus imperative to improve existing BNF systems and develop N 2 -fixing non-leguminous crops such as rice. Here we review the potentials and constraints of conventional BNF systems in rice agriculture, as well as the prospects of achieving in planta nitrogen fixation in rice. (author)

  8. Effect of the major components of industrial air pollution on nonsymbiotic nitrogen-fixation activity in soil

    Energy Technology Data Exchange (ETDEWEB)

    Islamov, S S; Chunderova, A I

    1976-01-01

    Industrial pollution of atmosphere inhibits the activity of non-symbiotic nitrogen fixation in soils. The inhibiting effect of polluted air can be explained by the presence of carbon monoxide and nitrogen dioxide in it. Sulfur dioxide does not depress the nitrogenase complex of aerobic and anaerobic nitrogen fixing microorganisms.

  9. Nitrogen fixation in Acacia auriculiformis and Albizia lebbeck and their contributions to crop-productivity improvement

    International Nuclear Information System (INIS)

    Mbaya, N.; Mwange, K.Nk.; Luyindula, N.

    1998-01-01

    Pot and field experiments assessed N 2 fixation by Albizia lebbeck and Acacia auriculiformis and contributions from prunings to yields of corn and hibiscus. Nitrogen fixation in these tree legumes was poor, with less than 50% N derived from fixation (%Ndfa) when grown in pots, but higher (>70%) in field conditions, after inoculation with compatible Bradyrhizobium strains. Prunings from A. lebbeck, as green manure improved growth of maize and hibiscus, inducing greater corn-kernel yields than did urea. Acacia auriculiformis prunings were similarly beneficial when mixed with leaves of A. lebbeck or L. leucocephala. Application of slow- and fast-nutrient-releasing leaves is required to maximize their contributions to crop productivity. (author)

  10. Endophytic nitrogen fixation in sugarcane: Present knowledge and future applications

    International Nuclear Information System (INIS)

    Boddey, Robert M.; Urquiaga, Segundo; Alves, Bruno J.R.; Reis, Veronica

    2001-01-01

    In Brazil the long-term continuous cultivation of sugarcane with low N fertiliser inputs, without apparent depletion of soil-N reserves, led to the suggestion that N 2 -fixing bacteria associated with the plants may be the source of agronomically significant N inputs to this crop. From the 1950s to 1970s, considerable numbers of N 2 -fixing bacteria were found to be associated with the crop, but it was not until the late 1980s that evidence from N balance and 15 N dilution experiments showed that some Brazilian varieties of sugarcane were able to obtain significant contributions from this source. The results of these studies renewed the efforts to search for N 2 -fixing bacteria, but this time the emphasis was on those diazotrophs that infected the interior of the plants. Within a few years several species of such 'endophytic diazotrophs' were discovered including Gluconacetobacter diazotrophicus, Herbaspirillum seropedicae, H. rubrisubalbicans and Burkholderia sp. Work has continued on these endophytes within sugarcane plants, but to date little success has been attained in elucidating which endophyte is responsible for the observed BNF and in what site, or sites, within the cane plants the N 2 fixation mainly occurs. Until such important questions are answered further developments or extension of this novel N 2 -fixing system to other economically important non-legumes (e.g. cereals) will be seriously hindered. As far as application of present knowledge to maximise BNF with sugarcane is concerned, molybdenum is an essential micronutrient. An abundant water supply favours high BNF inputs, and the best medium term strategy to increase BNF would appear to be based on cultivar selection on irrigated N deficient soils fertilised with Mo. (author)

  11. Environmental forcing of nitrogen fixation in the eastern tropical and sub-tropical North Atlantic Ocean.

    Science.gov (United States)

    Rijkenberg, Micha J A; Langlois, Rebecca J; Mills, Matthew M; Patey, Matthew D; Hill, Polly G; Nielsdóttir, Maria C; Compton, Tanya J; Laroche, Julie; Achterberg, Eric P

    2011-01-01

    During the winter of 2006 we measured nifH gene abundances, dinitrogen (N(2)) fixation rates and carbon fixation rates in the eastern tropical and sub-tropical North Atlantic Ocean. The dominant diazotrophic phylotypes were filamentous cyanobacteria, which may include Trichodesmium and Katagnymene, with up to 10(6) L(-1)nifH gene copies, unicellular group A cyanobacteria with up to 10(5) L(-1)nifH gene copies and gamma A proteobacteria with up to 10(4) L(-1)nifH gene copies. N(2) fixation rates were low and ranged between 0.032-1.28 nmol N L(-1) d(-1) with a mean of 0.30 ± 0.29 nmol N L(-1) d(-1) (1σ, n = 65). CO(2)-fixation rates, representing primary production, appeared to be nitrogen limited as suggested by low dissolved inorganic nitrogen to phosphate ratios (DIN:DIP) of about 2 ± 3.2 in surface waters. Nevertheless, N(2) fixation rates contributed only 0.55 ± 0.87% (range 0.03-5.24%) of the N required for primary production. Boosted regression trees analysis (BRT) showed that the distribution of the gamma A proteobacteria and filamentous cyanobacteria nifH genes was mainly predicted by the distribution of Prochlorococcus, Synechococcus, picoeukaryotes and heterotrophic bacteria. In addition, BRT indicated that multiple a-biotic environmental variables including nutrients DIN, dissolved organic nitrogen (DON) and DIP, trace metals like dissolved aluminum (DAl), as a proxy of dust inputs, dissolved iron (DFe) and Fe-binding ligands as well as oxygen and temperature influenced N(2) fixation rates and the distribution of the dominant diazotrophic phylotypes. Our results suggest that lower predicted oxygen concentrations and higher temperatures due to climate warming may increase N(2) fixation rates. However, the balance between a decreased supply of DIP and DFe from deep waters as a result of more pronounced stratification and an enhanced supply of these nutrients with a predicted increase in deposition of Saharan dust may ultimately determine the

  12. Theoretical Investigations of Novel Materials for Nitrogen Fixation

    DEFF Research Database (Denmark)

    Howalt, Jakob Geelmuyden

    This thesis is dedicated to the investigation and design of new catalyst materials for electrochemical ammonia production and especially the properties of the under-coordinated reaction sites on nanoparticles has been studied in great detail. Additionally, a universal transition state relation...... choice of reference systems the transition state scaling relations form a universality class that can be approximated with one single linear relation describing the entire range of reactions over all types of surfaces and nanoclusters. Theoretical studies of producing ammonia electrochemically at ambient...... hydrogen and nitrogen. These scaling relations and free energy corrections are used to establish volcanoes describing the onset potential for electrochemical ammonia production and hence describe the potential determining steps for the electrochemical ammonia production. The competing hydrogen evolution...

  13. Increased genetic variability for symbiotic nitrogen fixation in green gram (Vigna radiata L.)

    International Nuclear Information System (INIS)

    Rosaiah, G.; Kumari, D.S.; Satyanarayana, A.; Seenaiah, P.

    1989-01-01

    Full text: When green gram is planted after rice in Andhra Pradesh, its nitrogen fixation relies upon local rhizobia that have been able to survive the stress of 5-6 months submergence. No rhizobia strain isolated elsewhere was found superior to native rhizobia. Thus improvement of the host may be the only practicable way to improve nitrogen fixation. 15 mutants obtained from gamma irradiated green gram variety 'LGG 127' were tested along with the parent and the cultivar 'Pant Mung 2'. Nodule no. per plant was higher in the mutants. There was also considerable variation in dry weight of nodules per plant and in seed yield. However the number of nodules per plant showed no correlation with seed yield, nodule size may be more relevant. The N content of the shoots at anthesis was positively correlated with dry weight of nodules, seed protein % and seed yield per plant. (author)

  14. Ecology of nitrogen fixation in soils and rhizospheres. Pt. 5

    Energy Technology Data Exchange (ETDEWEB)

    Werner, D.; Stripf, R.; Abramowski, R.; Fiedler, U.

    1980-12-01

    The effects of reduced oxygen concentration on root growth and activities of enzymes of N-metabolism of wheat (Triticum aestivum var. Kolibri) have been studied, for low O/sub 2/ tensions are required for N/sub 2/ fixation by microaerophilic bacteria (e.g. Azospirillum) associated with root systems of grasses. In hydrocultures with oxygen concentrations in the range of 0.2 to 1 mg O/sub 2/ x 1/sup -1/ compared to aerated cultures (8-9 mg O/sub 2/ x 1/sup -1/) root growth was reduced from 10 mg fresh weight x day/sup -1/ x plant/sup -1/ to one tenth 15 to 30 d after sowing. Specific activity of NADH and NADPH dependent glutamate dehydrogenase (E.C. 1.4.1.2 and 1.4.1.4) is reduced by 50% in the cultures with low oxygen concentrations 20 to 30 days after sowing, whereas specific activity of aspartate aminotransferase (E.C. 2.6.1.1) and alanine amino transferase (E.C. 2.6.1.2) is enhanced by a factor of two to three. Specific activity of glutamine synthetase is almost unaffected. Specific activity of glutamate dehydrogenase is lowest in the root tips, medium in young root hair zone and highest in the old root hair zone, glutamine synthetase activity is reverse in the three zones with differences by a factor of 3-5; aspartate aminotransferase is similarly active in the three zones. Nitrate concentration used (100 ..mu..M) for cultivation of the wheat plants was tested with Azospirillum brasilense in pure culture on agar surfaces exposed to air at the same pH (5.8), used for cultivation of the wheat plants. Activiy after a 14 day period (peak activity 70 mmol C/sub 2/H/sub 4/ x mg protein/sup -1/ x h/sup -1/) was not affected, however 1 mM and 5 mM nitrate added reduced the total activity to 50% and 10% respectively.

  15. In Situ Denitrification and Biological Nitrogen Fixation Under Enhanced Atmospheric Reactive Nitrogen Deposition in UK Peatlands

    Science.gov (United States)

    Ullah, Sami; Saiz Val, Ernesto; Sgouridis, Fotis; Peichl, Matthias; Nilsson, Mats

    2017-04-01

    Dinitrogen (N2) and nitrous oxide (N2O) losses due to denitrification and biological N2 fixation (BNF) are the most uncertain components of the nitrogen (N) cycle in peatlands under enhanced atmospheric reactive nitrogen (Nr) deposition. This uncertainty hampers our ability to assess the contribution of denitrification to the removal of biologically fixed and/or atmospherically deposited Nr in peatlands. This uncertainty emanates from the difficulty in measuring in situ soil N2 and N2O production and consumption in peatlands. In situ denitrification and its contribution to total N2O flux was measured monthly between April 2013 and October 2014 in peatlands in two UK catchments. An adapted 15N-Gas Flux method1 with low level addition of 15N tracer (0.03 ± 0.005 kg 15N ha-1) was used to measure denitrification and its contribution to net N2O production (DN2O/TN2O). BNF was measured in situ through incubation of selected sphagnum species under 15N2 gas tracer. Denitrification2 varied temporally and averaged 8 kg N-N2 ha-1 y-1. The contribution of denitrification was about 48% to total N2O flux3 of 0.05 kg N ha-1 y-1. Soil moisture, temperature, ecosystem respiration, pH and mineral N content mainly regulated the flux of N2 and N2O. Preliminary results showed suppression of BNF, which was 1.8 to 7 times lower in peatland mosses exposed to ˜15 to 20 kg N ha-1 y-1 Nr deposition in the UK than in peatland mosses in northern Sweden with background Nr deposition. Overall, the contribution of denitrification to Nr removal in the selected peatlands was ˜50% of the annual Nr deposition rates, making these ecosystems vulnerable to chronic N saturation. These results point to a need for a more comprehensive annual BNF measurement to more accurately account for total Nr input into peatlands and its atmospheric loss due to denitrification. References Sgouridis F, Stott A & Ullah S, 2016. Application of the 15N-Gas Flux method for measuring in situ N2 and N2O fluxes due to

  16. Estimation of nitrogen fixation in Saccharum spp. by 15N dilution method

    International Nuclear Information System (INIS)

    Singh, Mohan

    1994-01-01

    The amount of nitrogen fixed by bacteria associated with the roots of Saccharum spontaneum, S. sinense, and S. barberi has been estimated by 15 N-isotope dilution method using Sclerotachya fusca as a non-fixing control. S. spontaneum produced highest shoot dry weight among the species tested but maximum nitrogen was accumulated by S. barberi. Highest dilution in the 15 N-enrichment was observed in S. spontaneum followed by S. sinense and S. barberi in comparison to the control plant of Sclerotchya fusca. S. spontaneum derived 60 per cent followed by S. sinense 54 per cent and S. barberi 35 per cent of their total nitrogen requirement through fixation of nitrogen by diazotrophic bacteria associated with their roots. (author). 11 refs., 2 tabs

  17. Freshwater mineral nitrogen and essential elements in autotrophs in James Ross Island, West Antarctica

    Directory of Open Access Journals (Sweden)

    Coufalík Pavel

    2016-12-01

    Full Text Available The lakes and watercourses are habitats for various communities of cyanobacteria and algae, which are among the few primary producers in Antarctica. The amount of nutrients in the mineral-poor Antarctic environment is a limiting factor for the growth of freshwater autotrophs in most cases. In this study, the main aim was to assess the availability of mineral nitrogen for microorganisms in cyanobacterial mats in James Ross Island. The nitrate and ammonium ions in water environment were determined as well as the contents of major elements (C, N, P, S, Na, K, Ca, Mg, Al, Fe, Mn in cyanobacterial mats. The molar ratios of C:N, C:P and N:P in mats were in focus. The growth of freshwater autotrophs seems not to be limited by the level of nitrogen, according to the content of available mineral nitrogen in water and the biogeochemical stoichiometry of C:N:P. The source of nutrients in the Ulu Peninsula is not obvious. The nitrogen fixation could enhance the nitrogen content in mats, which was observed in some samples containing the Nostoc sp.

  18. EnviroAtlas - Cultivated biological nitrogen fixation in agricultural lands by 12-digit HUC in the Conterminous United States, 2006

    Data.gov (United States)

    U.S. Environmental Protection Agency — This EnviroAtlas dataset contains data on the mean cultivated biological nitrogen fixation (C-BNF) in cultivated crop and hay/pasture lands per 12-digit Hydrologic...

  19. Biological nitrogen fixation in Crotalaria species estimated using the 15N isotope dilution method

    International Nuclear Information System (INIS)

    Samba, R.T.; Neyra, M.; Gueye, M.; Sylla, S.N.; Ndoye, I.; Dreyfus, B.

    2002-01-01

    Growing in Senegal by using 15 N direct isotope dilution technique. Two non-fixing plants, Senna obtusifolia and Senna occidentalis served as reference plants. The amount of nitrogen fixed two months after planting was obtained using the average of the two reference plants. The atom % 15 N excess in the Crotalaria species was significantly lower than that of the reference plants, indicating that significant nitrogen fixation occurred in the three plants. Significant differences were observed between the Crotalaria species; C. ochroleuca yielded more dry matter weight and total nitrogen than did C. perrottetti and C. retusa. The % nitrogen derived from atmosphere (%Ndfa) in leaves and stems was also higher in C. ochroleuca. There was no significant difference in %Ndfa in the whole plant between the three Crotalaria species (47% to 53%). In contrast, interspecific variability was observed based on the %Ndfa. C. ochroleuca significantly exhibited the higher amount of total nitrogen fixed, equivalent to 83 kg of nitrogen fixed per hectare. Based on these data, it was concluded that C. ochroleuca could be used in multiple cropping systems in Senegal for making more nitrogen available to other plants. (author)

  20. Role of PII proteins in nitrogen fixation control of Herbaspirillum seropedicae strain SmR1

    Directory of Open Access Journals (Sweden)

    Steffens Maria BR

    2011-01-01

    Full Text Available Abstract Background The PII protein family comprises homotrimeric proteins which act as transducers of the cellular nitrogen and carbon status in prokaryotes and plants. In Herbaspirillum seropedicae, two PII-like proteins (GlnB and GlnK, encoded by the genes glnB and glnK, were identified. The glnB gene is monocistronic and its expression is constitutive, while glnK is located in the nlmAglnKamtB operon and is expressed under nitrogen-limiting conditions. Results In order to determine the involvement of the H. seropedicae glnB and glnK gene products in nitrogen fixation, a series of mutant strains were constructed and characterized. The glnK- mutants were deficient in nitrogen fixation and they were complemented by plasmids expressing the GlnK protein or an N-truncated form of NifA. The nitrogenase post-translational control by ammonium was studied and the results showed that the glnK mutant is partially defective in nitrogenase inactivation upon addition of ammonium while the glnB mutant has a wild-type phenotype. Conclusions Our results indicate that GlnK is mainly responsible for NifA activity regulation and ammonium-dependent post-translational regulation of nitrogenase in H. seropedicae.

  1. Role of PII proteins in nitrogen fixation control of Herbaspirillum seropedicae strain SmR1.

    Science.gov (United States)

    Noindorf, Lilian; Bonatto, Ana C; Monteiro, Rose A; Souza, Emanuel M; Rigo, Liu U; Pedrosa, Fabio O; Steffens, Maria B R; Chubatsu, Leda S

    2011-01-11

    The PII protein family comprises homotrimeric proteins which act as transducers of the cellular nitrogen and carbon status in prokaryotes and plants. In Herbaspirillum seropedicae, two PII-like proteins (GlnB and GlnK), encoded by the genes glnB and glnK, were identified. The glnB gene is monocistronic and its expression is constitutive, while glnK is located in the nlmAglnKamtB operon and is expressed under nitrogen-limiting conditions. In order to determine the involvement of the H. seropedicae glnB and glnK gene products in nitrogen fixation, a series of mutant strains were constructed and characterized. The glnK- mutants were deficient in nitrogen fixation and they were complemented by plasmids expressing the GlnK protein or an N-truncated form of NifA. The nitrogenase post-translational control by ammonium was studied and the results showed that the glnK mutant is partially defective in nitrogenase inactivation upon addition of ammonium while the glnB mutant has a wild-type phenotype. Our results indicate that GlnK is mainly responsible for NifA activity regulation and ammonium-dependent post-translational regulation of nitrogenase in H. seropedicae.

  2. Biological nitrogen fixation in common bean and faba bean using N-15 methodology and two reference crops

    International Nuclear Information System (INIS)

    Calvache, Marcelo.

    1989-01-01

    A field was conducted on a Typic ustropepts soil located at 'La Tola', the experimental campus of the Agricultural Sciences Faculty at Tumbaco, Ecuador. The objectives were to quantify faba bean (Vicia faba) and common bean (Phaseolus vulgaris) biological nitrogen fixation, using quinoa (chenopodium quinoa) and maize (Zea mays) as reference crops. The average values were 80 and 70 per cent for faba bean and 42 and 14 per cent for common bean, respectively. It was assumed that nitrogen use eficiency was the same for fixing crops but observed that a crop with high nitrogen use efficiency overestimates legume biological nitrogen fixation. Results suggests that greater caution is needed when selecting reference crops for legumes with nitrogen fixation

  3. Effects of some inorganic elements on nitrogen-fixation in blue-green algae and some ecological aspects of pollution

    Energy Technology Data Exchange (ETDEWEB)

    Henriksson, L.E.; DaSilva, E.J.

    1978-01-01

    Nitrogen-fixation by two species of Nostoc, one of them a lichen phycobiont, was generally stimulated by low concentrations of arsenic, cadmium, nickel, lead, palladium, and zinc. Higher concentrations (0.025 to 0.125 ppM) of arsenic, nickel, and palladium were also stimulatory; however, higher concentrations of cadmium, lead, and zinc tended to inhibit fixation. With the exception of palladium and zinc at low concentrations these six tested elements tended to inhibit nitrogen-fixation in Chlorogloea fritschii and Westiellopsis sp.

  4. Sulphate reduction and nitrogen fixation rates associated with roots, rhizomes and sediments from Zostera noltii and Spartina maritima meadows.

    Science.gov (United States)

    Nielsen, L B; Finster, K; Welsh, D T; Donelly, A; Herbert, R A; de Wit, R; Lomstein, B A

    2001-01-01

    Sulphate reduction rates (SRR) and nitrogen fixation rates (NFR) associated with isolated roots, rhizomes and sediment from the rhizosphere of the marine macrophytes Zostera noltii and Spartina maritima, and the presence and distribution of Bacteria on the roots and rhizomes, were investigated. Between 1% and 3% of the surface area of the roots and rhizomes of both macrophytes were colonized by Bacteria. Bacteria on the surfaces of S. maritima roots and rhizomes were evenly distributed, while the distribution of Bacteria on Z. noltii roots and rhizomes was patchy. Root- and rhizome-associated SRR and NFR were always higher than rates in the bulk sediment. In particular, nitrogen fixation associated with the roots and rhizomes was 41-650-fold higher than in the bulk sediment. Despite the fact that sulphate reduction was elevated on roots and rhizomes compared with bulk sediment, the contribution of plant-associated sulphate reduction to overall sulphate reduction was small (< or =11%). In contrast, nitrogen fixation associated with the roots and rhizomes accounted for 31% and 91% of the nitrogen fixed in the rhizosphere of Z. noltii and S. maritima respectively. In addition, plant-associated nitrogen fixation could supply 37-1,613% of the nitrogen needed by the sulphate-reducing community. Sucrose stimulated nitrogen fixation and sulphate reduction significantly in the root and rhizome compartments of both macrophytes, but not in the bulk sediment.

  5. The use of 15N-labelled dinitrogen in the study of nitrogen fixation by blue-green algae

    International Nuclear Information System (INIS)

    Jones, J.

    1985-01-01

    Prior to the development of the acetylene reduction technique 15 N was used as the main qualitative and quantitative measure of nitrogen fixation by free-living cyanobacteria in a variety of aquatic and terrestrial habitats. Despite its expense and the technical difficulty, 15 N is a major tool in the study of cyanobacteria, for example, incorporation of 15 N 2 is the definitive test for nitrogen fixation; it is used in the determination of the correct ratio of acetylene reduction to nitrogen fixation, in in situ nitrogen fixation assays, in tracing the formation and fate of extra-cellular nitrogen and in measuring the turnover and grazing rates of cyanobacterial intra-cellular nitrogen. These latter studies show that 15 N-labelled extra-cellular nitrogen can serve as nitrogen sources for a variety of bacteria, fungi, algae and higher plants, and that cyanobacteria are graced and digested by a variety of animals. The turnover rates of cyanobacterial 15 N-labelled cells are dependent on the type of cell, species, environmental conditions and the availability of degrading organisms. The breakdown products are rapidly mineralised and used as nitrogen sources by higher plants. (author)

  6. The importance of nodule CO2 fixation for the efficiency of symbiotic nitrogen fixation in pea at vegetative growth and during pod formation.

    Science.gov (United States)

    Fischinger, Stephanie Anastasia; Schulze, Joachim

    2010-05-01

    Nodule CO2 fixation is of pivotal importance for N2 fixation. The process provides malate for bacteroids and oxaloacetate for nitrogen assimilation. The hypothesis of the present paper was that grain legume nodules would adapt to higher plant N demand and more restricted carbon availability at pod formation through increased nodule CO2 fixation and a more efficient N2 fixation. Growth, N2 fixation, and nodule composition during vegetative growth and at pod formation were studied in pea plants (Pisum sativum L.). In parallel experiments, 15N2 and 13CO2 uptake, as well as nodule hydrogen and CO2 release, was measured. Plants at pod formation showed higher growth rates and N2 fixation per plant when compared with vegetative growth. The specific activity of active nodules was about 25% higher at pod formation. The higher nodule activity was accompanied by higher amino acid concentration in nodules and xylem sap with a higher share of asparagine. Nodule 13CO2 fixation was increased at pod formation, both per plant and per 15N2 fixed unit. However, malate concentration in nodules was only 40% of that during vegetative growth and succinate was no longer detectable. The data indicate that increased N2 fixation at pod formation is connected with strongly increased nodule CO2 fixation. While the sugar concentration in nodules at pod formation was not altered, the concentration of organic acids, namely malate and succinate, was significantly lower. It is concluded that strategies to improve the capability of nodules to fix CO2 and form organic acids might prolong intensive N2 fixation into the later stages of pod formation and pod filling in grain legumes.

  7. BMAA Inhibits Nitrogen Fixation in the Cyanobacterium Nostoc sp. PCC 7120

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    Birgitta Bergman

    2013-08-01

    Full Text Available Cyanobacteria produce a range of secondary metabolites, one being the neurotoxic non-protein amino acid β-N-methylamino-L-alanine (BMAA, proposed to be a causative agent of human neurodegeneration. As for most cyanotoxins, the function of BMAA in cyanobacteria is unknown. Here, we examined the effects of BMAA on the physiology of the filamentous nitrogen-fixing cyanobacterium Nostoc sp. PCC 7120. Our data show that exogenously applied BMAA rapidly inhibits nitrogenase activity (acetylene reduction assay, even at micromolar concentrations, and that the inhibition was considerably more severe than that induced by combined nitrogen sources and most other amino acids. BMAA also caused growth arrest and massive cellular glycogen accumulation, as observed by electron microscopy. With nitrogen fixation being a process highly sensitive to oxygen species we propose that the BMAA effects found here may be related to the production of reactive oxygen species, as reported for other organisms.

  8. BMAA Inhibits Nitrogen Fixation in the Cyanobacterium Nostoc sp. PCC 7120

    Science.gov (United States)

    Berntzon, Lotta; Erasmie, Sven; Celepli, Narin; Eriksson, Johan; Rasmussen, Ulla; Bergman, Birgitta

    2013-01-01

    Cyanobacteria produce a range of secondary metabolites, one being the neurotoxic non-protein amino acid β-N-methylamino-L-alanine (BMAA), proposed to be a causative agent of human neurodegeneration. As for most cyanotoxins, the function of BMAA in cyanobacteria is unknown. Here, we examined the effects of BMAA on the physiology of the filamentous nitrogen-fixing cyanobacterium Nostoc sp. PCC 7120. Our data show that exogenously applied BMAA rapidly inhibits nitrogenase activity (acetylene reduction assay), even at micromolar concentrations, and that the inhibition was considerably more severe than that induced by combined nitrogen sources and most other amino acids. BMAA also caused growth arrest and massive cellular glycogen accumulation, as observed by electron microscopy. With nitrogen fixation being a process highly sensitive to oxygen species we propose that the BMAA effects found here may be related to the production of reactive oxygen species, as reported for other organisms. PMID:23966039

  9. Nitrogen Fixation By Sulfate-Reducing Bacteria in Coastal and Deep-Sea Sediments

    Science.gov (United States)

    Bertics, V. J.; Löscher, C.; Salonen, I.; Schmitz-Streit, R.; Lavik, G.; Kuypers, M. M.; Treude, T.

    2011-12-01

    Sulfate-reducing bacteria (SRB) can greatly impact benthic nitrogen (N) cycling, by for instance inhibiting coupled denitrification-nitrification through the production of sulfide or by increasing the availability of fixed N in the sediment via dinitrogen (N2)-fixation. Here, we explored several coastal and deep-sea benthic habitats within the Atlantic Ocean and Baltic Sea, for the occurrence of N2-fixation mediated by SRB. A combination of different methods including microbial rate measurements of N2-fixation and sulfate reduction, geochemical analyses (porewater nutrient profiles, mass spectrometry), and molecular analyses (CARD-FISH, HISH-SIMS, "nested" PCR, and QPCR) were applied to quantify and identify the responsible processes and organisms, respectively. Furthermore, we looked deeper into the question of whether the observed nitrogenase activity was associated with the final incorporation of N into microbial biomass or whether the enzyme activity served another purpose. At the AGU Fall Meeting, we will present and compare data from numerous stations with different water depths, temperatures, and latitudes, as well as differences in key geochemical parameters, such as organic carbon content and oxygen availability. Current metabolic and molecular data indicate that N2-fixation is occurring in many of these benthic environments and that a large part of this activity may linked to SRB.

  10. The cyanobacterial nitrogen fixation paradox in natural waters [version 1; referees: 2 approved

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    Hans Paerl

    2017-03-01

    Full Text Available Nitrogen fixation, the enzymatic conversion of atmospheric N (N2 to ammonia (NH3, is a microbially mediated process by which “new” N is supplied to N-deficient water bodies. Certain bloom-forming cyanobacterial species are capable of conducting N2 fixation; hence, they are able to circumvent N limitation in these waters. However, this anaerobic process is highly sensitive to oxygen, and since cyanobacteria produce oxygen in photosynthesis, they are faced with a paradoxical situation, where one critically important (for supporting growth biochemical process is inhibited by another. N2-fixing cyanobacterial taxa have developed an array of biochemical, morphological, and ecological adaptations to minimize the “oxygen problem”; however, none of these allows N2 fixation to function at a high enough efficiency so that it can supply N needs at the ecosystem scale, where N losses via denitrification, burial, and advection often exceed the inputs of “new” N by N2 fixation. As a result, most marine and freshwater ecosystems exhibit chronic N limitation of primary production. Under conditions of perpetual N limitation, external inputs of N from human sources (agricultural, urban, and industrial play a central role in determining ecosystem fertility and, in the case of N overenrichment, excessive primary production or eutrophication. This points to the importance of controlling external N inputs (in addition to traditional phosphorus controls as a means of ensuring acceptable water quality and safe water supplies. Nitrogen fixation, the enzymatic conversion of atmospheric N2 to ammonia (NH3 is a  microbially-mediated process by which “new” nitrogen is supplied to N-deficient water bodies.  Certain bloom-forming cyanobacterial species are capable of conducting N2 fixation; hence they are able to circumvent nitrogen limitation in these waters. However, this anaerobic process is highly sensitive to oxygen, and since cyanobacteria produce

  11. The value of biodiversity in legume symbiotic nitrogen fixation and nodulation for biofuel and food production.

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    Gresshoff, Peter M; Hayashi, Satomi; Biswas, Bandana; Mirzaei, Saeid; Indrasumunar, Arief; Reid, Dugald; Samuel, Sharon; Tollenaere, Alina; van Hameren, Bethany; Hastwell, April; Scott, Paul; Ferguson, Brett J

    2015-01-01

    Much of modern agriculture is based on immense populations of genetically identical or near-identical varieties, called cultivars. However, advancement of knowledge, and thus experimental utility, is found through biodiversity, whether naturally-found or induced by the experimenter. Globally we are confronted by ever-growing food and energy challenges. Here we demonstrate how such biodiversity from the food legume crop soybean (Glycine max L. Merr) and the bioenergy legume tree Pongamia (Millettia) pinnata is a great value. Legume plants are diverse and are represented by over 18,000 species on this planet. Some, such as soybean, pea and medics are used as food and animal feed crops. Others serve as ornamental (e.g., wisteria), timber (e.g., acacia/wattle) or biofuel (e.g., Pongamia pinnata) resources. Most legumes develop root organs (nodules) after microsymbiont induction that serve as their habitat for biological nitrogen fixation. Through this, nitrogen fertiliser demand is reduced by the efficient symbiosis between soil Rhizobium-type bacteria and the appropriate legume partner. Mechanistic research into the genetics, biochemistry and physiology of legumes is thus strategically essential for future global agriculture. Here we demonstrate how molecular plant science analysis of the genetics of an established food crop (soybean) and an emerging biofuel P. pinnata feedstock contributes to their utility by sustainable production aided by symbiotic nitrogen fixation. Crown Copyright © 2014. Published by Elsevier GmbH. All rights reserved.

  12. Endophytic colonization and in planta nitrogen fixation by a diazotrophic Serratia sp. in rice.

    Science.gov (United States)

    Sandhiya, G S; Sugitha, T C K; Balachandar, D; Kumar, K

    2005-09-01

    Nitrogen fixing endophytic Serratia sp. was isolated from rice and characterized. Re-colonization ability of Serratia sp. in the rice seedlings as endophyte was studied under laboratory condition. For detecting the re-colonization potential in the rice seedlings, Serratia sp. was marked with reporter genes (egfp and Kmr) using transposon mutagenesis. The conjugants were screened for re-colonization ability and presence of nif genes using PCR. Further, the influence of flavonoids and growth hormones on the endophytic colonization and in planta nitrogen fixation of Serratia was also investigated. The flavonoids, quercetin (3 microg/ml) and diadzein (2 microg/ml) significantly increased the re-colonization ability of the endophytic Serratia, whereas the growth hormones like IAA and NAA (5 microg/ml) reduced the endophytic colonization ability of Serratia sp. Similarly, the in planta nitrogen fixation by Serratia sp. in rice was significantly increased due to flavonoids. The inoculation of endophytic diazotrophs increased the plant biomass and biochemical constituents.

  13. Woody encroachment impacts on ecosystem nitrogen cycling: fixation, storage and gas loss

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    Soper, F.; Sparks, J. P.

    2016-12-01

    Woody encroachment is a pervasive land cover change throughout the tropics and subtropics. Encroachment is frequently catalyzed by nitrogen (N)-fixing trees and the resulting N inputs have the potential to alter whole-ecosystem N cycling, accumulation and loss. In the southern US, widespread encroachment by legume Prosopis glandulosa is associated with increased soil total N storage, inorganic N concentrations, and net mineralization and nitrification rates. To better understand the effects of this process on ecosystem N cycling, we investigated patterns of symbiotic N fixation, N accrual and soil N trace gas and N2 emissions during Prosopis encroachment into the southern Rio Grande Plains. Analyses of d15N in foliage, xylem sap and plant-available soil N suggested that N fixation rates vary seasonally, inter-annually and as a function of plant age and abiotic conditions. Applying a small-scale mass balance model to soil N accrual around individual trees (accounting for atmospheric inputs, and gas and hydrologic losses) generated current fixation estimates of 11 kg N ha-1 yr-1, making symbiotic fixation the largest input of N to the ecosystem. However, soil N accrual and increased cycling rates did not translate into increased N gas losses. Two years of field measurements of a complete suite of N trace gases (ammonia, nitrous oxide, nitric oxide and other oxidized N compounds) found no difference in flux between upland Prosopis groves and adjacent unencroached grasslands. Total emissions average 0.56-0.65 kg N ha-1 yr-1, comparable to other southern US grasslands. Lab incubations suggested that N2 losses are likely to be low, with field oxygen conditions not usually conducive to denitrification. Taken together, results suggest that this ecosystem is currently experiencing a period of significant net N accrual, driven by fixation under ongoing encroachment. Given the large scale of woody legume encroachment in the USA, this process is likely to contribute

  14. Nitrogen Fixation by Gliding Arc Plasma: Better Insight by Chemical Kinetics Modelling.

    Science.gov (United States)

    Wang, Weizong; Patil, Bhaskar; Heijkers, Stjin; Hessel, Volker; Bogaerts, Annemie

    2017-05-22

    The conversion of atmospheric nitrogen into valuable compounds, that is, so-called nitrogen fixation, is gaining increased interest, owing to the essential role in the nitrogen cycle of the biosphere. Plasma technology, and more specifically gliding arc plasma, has great potential in this area, but little is known about the underlying mechanisms. Therefore, we developed a detailed chemical kinetics model for a pulsed-power gliding-arc reactor operating at atmospheric pressure for nitrogen oxide synthesis. Experiments are performed to validate the model and reasonable agreement is reached between the calculated and measured NO and NO 2 yields and the corresponding energy efficiency for NO x formation for different N 2 /O 2 ratios, indicating that the model can provide a realistic picture of the plasma chemistry. Therefore, we can use the model to investigate the reaction pathways for the formation and loss of NO x . The results indicate that vibrational excitation of N 2 in the gliding arc contributes significantly to activating the N 2 molecules, and leads to an energy efficient way of NO x production, compared to the thermal process. Based on the underlying chemistry, the model allows us to propose solutions on how to further improve the NO x formation by gliding arc technology. Although the energy efficiency of the gliding-arc-based nitrogen fixation process at the present stage is not comparable to the world-scale Haber-Bosch process, we believe our study helps us to come up with more realistic scenarios of entering a cutting-edge innovation in new business cases for the decentralised production of fertilisers for agriculture, in which low-temperature plasma technology might play an important role. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Effect of soil-moisture stress on nitrogen uptake and fixation by plants

    International Nuclear Information System (INIS)

    Mitrosuhardjo, M.M.

    1983-01-01

    The effect of four levels of soil moisture, namely 25, 30, 35, and 40% (g/g) on nitrogen uptake and fixation by plants was studied in a greenhouse experiment. Soybean and wheat were used in this experiment. Both crops were grown in pots containing 7 kg loamy alluvial soil. Rhizobium japonicum was used as an inoculant for soybean, one week after planting. Nitrogen-15 labelled urea with 10% atom excess was applied to each pot with a dose rate of 70 mg N/pot (20 kg N/ha) two weeks after planting. Soil moisture was regularly controlled with porous-cup mercury tensiometers, and the amount of water consumed by plants was always recorded. Water was applied to each pot with a distribution pipe which was laid down in the centre of the soil depth, horizontally in a circular form, and was connected with a smaller pipe to the soil surface. The result obtained showed that the amount of water consumed by plants grown in a higher level of soil moisture was increased until soil aeration problems arose. A different amount of water consumption between soybean and wheat was observed at least until a certain period of growing time. Fertilizer nitrogen taken up by both crops varied with the different levels of soil moisture. Generally, greater fertilizer nitrogen was taken up by both crops grown in a higher level of soil moisture. The symbiotic fixation of nitrogen was reasonable, although no clarification has been found about the role of the four levels of soil-moisture treatment on it. A similar effect of soil-moisture stress on nodule dry matter and acetylene reduction was found. (author)

  16. Soybean seed treatment with nickel improves biological nitrogen fixation and urease activity

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    José eLavres Junior

    2016-05-01

    Full Text Available Nickel (Ni is an essential micronutrient required for plants’ metabolism due to its role as a structural component of urease and hydrogenase, which in turn perform nitrogen (N metabolism in many legume species. Seed treatment with cobalt, molybdenum and Bradyrhizobium strains has been widely practiced to improve crops. Additionally, seed treatment together with Ni fertilization of soybean might improve the efficiency of biological nitrogen fixation (BNF, boosting grain dry matter yield and N content. The objective of this study was to evaluate the effect of soybean seed treatment with Ni rates (0, 45, 90,135, 180, 360 and 540 mg kg-1 on biological nitrogen fixation (BNF, directly by the 15N natural abundance method (δ15N‰ and by measurement of urease [E.C. 3.5.1.5] activity, as well as indirectly by nitrogenase (N-ase activity [E.C. 1.18.6.1]. Soybean plants (cultivar BMX Potência RR were grown in a sandy soil up to the R7 developmental stage (grain maturity, at which point the nutrient content in the leaves, chlorophyll content, urease and N-ase activities, Ni and N content in the grains, nodulation (at R1 - flowering stage, as well as the contribution of biological nitrogen fixation (δ15N ‰, were evaluated. The proportion of N derived from N2 fixation varied from 77 to 99% using the natural 15N abundance method and non-nodulating Panicum miliaceum and Phalaris canariensis as references. A Ni rate of 45 mg kg-1 increased BNF by 12% compared to the control. The increased N uptake in the grains was closely correlated with chlorophyll content in the leaves, urease and N-ase activities, as well as with nodulation. Grain dry matter yield and aerial part dry matter yield increased, respectively, by 84% and 51% in relation to the control plants at 45 mg kg-1 Ni via seed treatment. Despite, Ni concentration was increased with Ni-seed treatment, Ni rates higher than 135 mg kg-1 promoted negative effects on plant growth and yield. In these

  17. Evaluation of nitrogen fixation rates of soybean and species of rhizobia

    International Nuclear Information System (INIS)

    Ping Shuzhen; You Chongbiao

    1993-01-01

    Using 1 '5N dilution technique the nitrogen fixing rates were estimated from symbiosis between 20 varieties of soybean and 2 species of rhizobia: Bradyrhizobium japonicum and Sinorhizobium fredii. The nodulation status such as size and number of nodules differed among the varieties and species of bacteria. The Ndfa% of these varieties ranged from 40% ∼ 59% for S. fredii, 38% ∼ 62% for B. japonicum and 32% ∼ 56% for inoculant of the mixture of the species, respectively. Among 3 inoculants the B. japonicum is the best one. The variety of soybean, however, plays a significant role in the symbiosis. Therefore, improving the soybean and selecting a good partner for raising the yield and nitrogen fixation are important

  18. Role of nitrogen fixation in the autecology of Polaromonas naphthalenivorans in contaminated sediments.

    Science.gov (United States)

    Hanson, Buck T; Yagi, Jane M; Jeon, Che Ok; Madsen, Eugene M

    2012-06-01

    Polaromonas naphthalenivorans strain CJ2 is a Gram-negative betaproteobacterium that was identified, using stable isotope probing in 2003, as a dominant in situ degrader of naphthalene in coal tar-contaminated sediments. The sequenced genome of strain CJ2 revealed several genes conferring nitrogen fixation within a 65.6 kb region of strain CJ2's chromosome that is absent in the genome of its closest sequenced relative Polaromonas sp. strain JS666. Laboratory growth and nitrogenase assays verified that these genes are functional, providing an alternative source of nitrogen in N-free media when using naphthalene or pyruvate as carbon sources. Knowing this, we investigated if nitrogen-fixation activity could be detected in microcosms containing sediments from the field site where strain CJ2 was isolated. Inducing nitrogen limitation with the addition of glucose or naphthalene stimulated nitrogenase activity in amended sediments, as detected using the acetylene reduction assay. With the use of fluorescence microscopy, we screened the microcosm sediments for the presence of active strain CJ2 cells using a dual-labelling approach. When we examined the carbon-amended microcosm sediments stained with both a strain CJ2-specific fluorescent in situ hybridization probe and a polyclonal fluorescently tagged antibody, we were able to detect dual-labelled active cells. In contrast, in sediments that received no carbon addition (showing no nitrogenase activity), no dual-labelled cells were detected. Furthermore, the naphthalene amendment enhanced the proportion of active strain CJ2 cells in the sediment relative to a glucose amendment. Field experiments performed in sediments where strain CJ2 was isolated showed nitrogenase activity in response to dosing with naphthalene. Dual-label fluorescence staining of these sediments showed a fivefold increase in active strain CJ2 in the sediments dosed with naphthalene over those dosed with deionized water. These experiments show that

  19. A Proteomic Network for Symbiotic Nitrogen Fixation Efficiency in Bradyrhizobium elkanii.

    Science.gov (United States)

    Cooper, Bret; Campbell, Kimberly B; Beard, Hunter S; Garrett, Wesley M; Mowery, Joseph; Bauchan, Gary R; Elia, Patrick

    2018-03-01

    Rhizobia colonize legumes and reduce N 2 to NH 3 in root nodules. The current model is that symbiotic rhizobia bacteroids avoid assimilating this NH 3 . Instead, host legume cells form glutamine from NH 3 , and the nitrogen is returned to the bacteroid as dicarboxylates, peptides, and amino acids. In soybean cells surrounding bacteroids, glutamine also is converted to ureides. One problem for soybean cultivation is inefficiency in symbiotic N 2 fixation, the biochemical basis of which is unknown. Here, the proteomes of bacteroids of Bradyrhizobium elkanii USDA76 isolated from N 2 fixation-efficient Peking and -inefficient Williams 82 soybean nodules were analyzed by mass spectrometry. Nearly half of the encoded bacterial proteins were quantified. Efficient bacteroids produced greater amounts of enzymes to form Nod factors and had increased amounts of signaling proteins, transporters, and enzymes needed to generate ATP to power nitrogenase and to acquire resources. Parallel investigation of nodule proteins revealed that Peking had no significantly greater accumulation of enzymes needed to assimilate NH 3 than Williams 82. Instead, efficient bacteroids had increased amounts of enzymes to produce amino acids, including glutamine, and to form ureide precursors. These results support a model for efficient symbiotic N 2 fixation in soybean where the bacteroid assimilates NH 3 for itself.

  20. Nitrogen fixation in the activated sludge treatment of thermomechanical pulping wastewater: effect of dissolved oxygen.

    Science.gov (United States)

    Slade, A H; Anderson, S M; Evans, B G

    2003-01-01

    N-ViroTech, a novel technology which selects for nitrogen-fixing bacteria as the bacteria primarily responsible for carbon removal, has been developed to treat nutrient limited wastewaters to a high quality without the addition of nitrogen, and only minimal addition of phosphorus. Selection of the operating dissolved oxygen level to maximise nitrogen fixation forms a key component of the technology. Pilot scale activated sludge treatment of a thermomechanical pulping wastewater was carried out in nitrogen-fixing mode over a 15 month period. The effect of dissolved oxygen was studied at three levels: 14% (Phase 1), 5% (Phase 2) and 30% (Phase 3). The plant was operated at an organic loading of 0.7-1.1 kg BOD5/m3/d, a solids retention time of approximately 10 d, a hydraulic retention time of 1.4 d and a F:M ratio of 0.17-0.23 mg BOD5/mg VSS/d. Treatment performance was very stable over the three dissolved oxygen operating levels. The plant achieved 94-96% BOD removal, 82-87% total COD removal, 79-87% soluble COD removal, and >99% total extractives removal. The lowest organic carbon removals were observed during operation at 30% DO but were more likely to be due to phosphorus limitation than operation at high dissolved oxygen, as there was a significant decrease in phosphorus entering the plant during Phase 3. Discharge of dissolved nitrogen, ammonium and oxidised nitrogen were consistently low (1.1-1.6 mg/L DKN, 0.1-0.2 mg/L NH4+-N and 0.0 mg/L oxidised nitrogen). Discharge of dissolved phosphorus was 2.8 mg/L, 0.1 mg/L and 0.6 mg/L DRP in Phases 1, 2 and 3 respectively. It was postulated that a population of polyphosphate accumulating bacteria developed during Phase 1. Operation at low dissolved oxygen during Phase 2 appeared to promote biological phosphorus uptake which may have been affected by raising the dissolved oxygen to 30% in Phase 3. Total nitrogen and phosphorus discharge was dependent on efficient secondary clarification, and improved over the course of

  1. Using synthetic biology to distinguish and overcome regulatory and functional barriers related to nitrogen fixation.

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    Xia Wang

    Full Text Available Biological nitrogen fixation is a complex process requiring multiple genes working in concert. To date, the Klebsiella pneumoniae nif gene cluster, divided into seven operons, is one of the most studied systems. Its nitrogen fixation capacity is subject to complex cascade regulation and physiological limitations. In this report, the entire K. pneumoniae nif gene cluster was reassembled as operon-based BioBrick parts in Escherichia coli. It provided ~100% activity of native K. pneumoniae system. Based on the expression levels of these BioBrick parts, a T7 RNA polymerase-LacI expression system was used to replace the σ(54-dependent promoters located upstream of nif operons. Expression patterns of nif operons were critical for the maximum activity of the recombinant system. By mimicking these expression levels with variable-strength T7-dependent promoters, ~42% of the nitrogenase activity of the σ(54-dependent nif system was achieved in E. coli. When the newly constructed T7-dependent nif system was challenged with different genetic and physiological conditions, it bypassed the original complex regulatory circuits, with minor physiological limitations. Therefore, we have successfully replaced the nif regulatory elements with a simple expression system that may provide the first step for further research of introducing nif genes into eukaryotic organelles, which has considerable potentials in agro-biotechnology.

  2. Heterotrophic N2-fixation contributes to nitrogen economy of a common wetland sedge, Schoenoplectus californicus.

    Science.gov (United States)

    Rejmánková, Eliška; Sirová, Dagmara; Castle, Stephanie T; Bárta, Jiří; Carpenter, Heather

    2018-01-01

    A survey of the ecological variability within 52 populations of Schoenoplectus californicus (C.A. Mey.) Soják across its distributional range revealed that it is commonly found in nitrogen (N) limited areas, but rarely in phosphorus limited soils. We explored the hypothesis that S. californicus supplements its nitrogen demand by bacterial N2-fixation processes associated with its roots and rhizomes. We estimated N2-fixation of diazotrophs associated with plant rhizomes and roots from several locations throughout the species' range and conducted an experiment growing plants in zero, low, and high N additions. Nitrogenase activity in rhizomes and roots was measured using the acetylene reduction assay. The presence of diazotrophs was verified by the detection of the nifH gene. Nitrogenase activity was restricted to rhizomes and roots and it was two orders of magnitude higher in the latter plant organs (81 and 2032 nmol C2H4 g DW-1 d-1, respectively). Correspondingly, 40x more nifH gene copies were found on roots compared to rhizomes. The proportion of the nifH gene copies in total bacterial DNA was positively correlated with the nitrogenase activity. In the experiment, the contribution of fixed N to the plant N content ranged from 13.8% to 32.5% among clones from different locations. These are relatively high values for a non-cultivated plant and justify future research on the link between N-fixing bacteria and S. californicus production.

  3. Systems biology of bacterial nitrogen fixation: High-throughput technology and its integrative description with constraint-based modeling

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    Resendis-Antonio Osbaldo

    2011-07-01

    Full Text Available Abstract Background Bacterial nitrogen fixation is the biological process by which atmospheric nitrogen is uptaken by bacteroids located in plant root nodules and converted into ammonium through the enzymatic activity of nitrogenase. In practice, this biological process serves as a natural form of fertilization and its optimization has significant implications in sustainable agricultural programs. Currently, the advent of high-throughput technology supplies with valuable data that contribute to understanding the metabolic activity during bacterial nitrogen fixation. This undertaking is not trivial, and the development of computational methods useful in accomplishing an integrative, descriptive and predictive framework is a crucial issue to decoding the principles that regulated the metabolic activity of this biological process. Results In this work we present a systems biology description of the metabolic activity in bacterial nitrogen fixation. This was accomplished by an integrative analysis involving high-throughput data and constraint-based modeling to characterize the metabolic activity in Rhizobium etli bacteroids located at the root nodules of Phaseolus vulgaris (bean plant. Proteome and transcriptome technologies led us to identify 415 proteins and 689 up-regulated genes that orchestrate this biological process. Taking into account these data, we: 1 extended the metabolic reconstruction reported for R. etli; 2 simulated the metabolic activity during symbiotic nitrogen fixation; and 3 evaluated the in silico results in terms of bacteria phenotype. Notably, constraint-based modeling simulated nitrogen fixation activity in such a way that 76.83% of the enzymes and 69.48% of the genes were experimentally justified. Finally, to further assess the predictive scope of the computational model, gene deletion analysis was carried out on nine metabolic enzymes. Our model concluded that an altered metabolic activity on these enzymes induced

  4. Pronounced fixation, strong population differentiation and complex population history in the Canary Islands blue tit subspecies complex.

    Science.gov (United States)

    Hansson, Bengt; Ljungqvist, Marcus; Illera, Juan-Carlos; Kvist, Laura

    2014-01-01

    Evolutionary molecular studies of island radiations may lead to insights in the role of vicariance, founder events, population size and drift in the processes of population differentiation. We evaluate the degree of population genetic differentiation and fixation of the Canary Islands blue tit subspecies complex using microsatellite markers and aim to get insights in the population history using coalescence based methods. The Canary Island populations were strongly genetically differentiated and had reduced diversity with pronounced fixation including many private alleles. In population structure models, the relationship between the central island populations (La Gomera, Tenerife and Gran Canaria) and El Hierro was difficult to disentangle whereas the two European populations showed consistent clustering, the two eastern islands (Fuerteventura and Lanzarote) and Morocco weak clustering, and La Palma a consistent unique lineage. Coalescence based models suggested that the European mainland forms an outgroup to the Afrocanarian population, a split between the western island group (La Palma and El Hierro) and the central island group, and recent splits between the three central islands, and between the two eastern islands and Morocco, respectively. It is clear that strong genetic drift and low level of concurrent gene flow among populations have shaped complex allelic patterns of fixation and skewed frequencies over the archipelago. However, understanding the population history remains challenging; in particular, the pattern of extreme divergence with low genetic diversity and yet unique genetic material in the Canary Island system requires an explanation. A potential scenario is population contractions of a historically large and genetically variable Afrocanarian population, with vicariance and drift following in the wake. The suggestion from sequence-based analyses of a Pleistocene extinction of a substantial part of North Africa and a Pleistocene/Holocene eastward

  5. Pronounced fixation, strong population differentiation and complex population history in the Canary Islands blue tit subspecies complex.

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    Bengt Hansson

    Full Text Available Evolutionary molecular studies of island radiations may lead to insights in the role of vicariance, founder events, population size and drift in the processes of population differentiation. We evaluate the degree of population genetic differentiation and fixation of the Canary Islands blue tit subspecies complex using microsatellite markers and aim to get insights in the population history using coalescence based methods. The Canary Island populations were strongly genetically differentiated and had reduced diversity with pronounced fixation including many private alleles. In population structure models, the relationship between the central island populations (La Gomera, Tenerife and Gran Canaria and El Hierro was difficult to disentangle whereas the two European populations showed consistent clustering, the two eastern islands (Fuerteventura and Lanzarote and Morocco weak clustering, and La Palma a consistent unique lineage. Coalescence based models suggested that the European mainland forms an outgroup to the Afrocanarian population, a split between the western island group (La Palma and El Hierro and the central island group, and recent splits between the three central islands, and between the two eastern islands and Morocco, respectively. It is clear that strong genetic drift and low level of concurrent gene flow among populations have shaped complex allelic patterns of fixation and skewed frequencies over the archipelago. However, understanding the population history remains challenging; in particular, the pattern of extreme divergence with low genetic diversity and yet unique genetic material in the Canary Island system requires an explanation. A potential scenario is population contractions of a historically large and genetically variable Afrocanarian population, with vicariance and drift following in the wake. The suggestion from sequence-based analyses of a Pleistocene extinction of a substantial part of North Africa and a Pleistocene

  6. Multivariate analysis and determination of the best indirect selection criteria to genetic improvement the biological nitrogen fixation ability in common bean genotypes (Phaseolus vulgaris L.

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    Golparvar Reza Ahmad

    2012-01-01

    Full Text Available In order to determine the best indirect selection criteria for genetic improvement of biological nitrogen fixation, sixty four common bean genotypes were cultivated in two randomized complete block design. Genotypes were inoculated with bacteria Rhizobium legominosarum biovar Phaseoli isolate L-109 only in one of the experiments. The second experiment was considered as check for the first. Correlation analysis showed positive and highly significant correlation of majority of the traits with percent of nitrogen fixation. Step-wise regression designated that traits percent of total nitrogen of shoot, number of nodule per plant and biological yield accounted for 92.3 percent of variation exist in percent of nitrogen fixation. Path analysis indicated that these traits have direct and positive effect on percent of nitrogen fixation. Hence, these traits are promising indirect selection criteria for genetic improvement of nitrogen fixation capability in common bean genotypes especially in early generations.

  7. Database of diazotrophs in global ocean: abundance, biomass and nitrogen fixation rates

    Directory of Open Access Journals (Sweden)

    Y.-W. Luo

    2012-08-01

    Full Text Available Marine N2 fixing microorganisms, termed diazotrophs, are a key functional group in marine pelagic ecosystems. The biological fixation of dinitrogen (N2 to bioavailable nitrogen provides an important new source of nitrogen for pelagic marine ecosystems and influences primary productivity and organic matter export to the deep ocean. As one of a series of efforts to collect biomass and rates specific to different phytoplankton functional groups, we have constructed a database on diazotrophic organisms in the global pelagic upper ocean by compiling about 12 000 direct field measurements of cyanobacterial diazotroph abundances (based on microscopic cell counts or qPCR assays targeting the nifH genes and N2 fixation rates. Biomass conversion factors are estimated based on cell sizes to convert abundance data to diazotrophic biomass. The database is limited spatially, lacking large regions of the ocean especially in the Indian Ocean. The data are approximately log-normal distributed, and large variances exist in most sub-databases with non-zero values differing 5 to 8 orders of magnitude. Reporting the geometric mean and the range of one geometric standard error below and above the geometric mean, the pelagic N2 fixation rate in the global ocean is estimated to be 62 (52–73 Tg N yr−1 and the pelagic diazotrophic biomass in the global ocean is estimated to be 2.1 (1.4–3.1 Tg C from cell counts and to 89 (43–150 Tg C from nifH-based abundances. Reporting the arithmetic mean and one standard error instead, these three global estimates are 140 ± 9.2 Tg N yr−1, 18 ± 1.8 Tg C and 590 ± 70 Tg C, respectively. Uncertainties related to biomass conversion factors can change the estimate of geometric mean pelagic diazotrophic biomass in the global ocean by about ±70%. It was recently established that the most commonly applied method used to measure N2

  8. CARBON CYCLES, NITROGEN FIXATION AND THE LEGUME-RHIZOBIA SYMBIOSIS AS SOIL CONTAMINANT BIOTEST SYSTEM

    Directory of Open Access Journals (Sweden)

    Dietrich Werner

    2008-06-01

    Full Text Available The major pools and turnover  rates of the global carbon (C cycles are presented and compared to the human production of CO2  from the burning of fossil fuels (e.g. coal and oil and geothermal  fuels (natural  gases, both categorized as non-renewable energy resources which  in amount  reaches around  6.5 Gigatons C per year. These pools that serve as C-holding stallions  are in the atmosphere,  the land plant biomass, the organic soils carbon, the ocean carbon and the lithosphere. In another related case, the present focus in the area of nitrogen  fixation  is discussed with  data on world  production of grain  legumes  compared  to cereals production and nitrogen  fertilizer use. The focus to understand  the molecular  biology of the legume-rhizobia symbiosis as a major contributor to nitrogen  fixation  is in the areas of signal exchange between  host plants and rhizobia  in the rhizophere including  the nod factor signalling, the infection  and nodule compartmentation and the soils stress factors affecting the symbiosis. The use of the Legume-Rhizobia symbiosis as a biotest system for soil contaminants includes data for cadmium,  arsenate, atrazine,  lindane,  fluoranthene, phenantrene and acenaphthene and also results  on the mechanism,  why the symbiotic system is more sensitive  than test systems with plant growth  parameters.

  9. Determination of biological nitrogen fixation capacities of winter and spring lentil varieties by using ''1''5N methodology

    International Nuclear Information System (INIS)

    Akin, A.

    2001-01-01

    In order to determine the biological nitrogen fixation capacities of winter and spring varieties of lentil which have of agronomic importance under the Central Anatolia region, the field experiments (winter and spring) were carried out. In both experiments, the effects of two different iconoclasts and different harvesting times on the biological nitrogen fixation capacities of lentil varieties, were investigated. The field experiments were conducted using by randomized block design as split-split plot for 4 replications. Barley was selected as the reference crop and 20 cm row spacing were used for lentil and barley. Inoculations were done immediately before sowing. 10.0 kg N/ ha for lentil varieties as 10.0 % ''1''5N atom excess and 40.0 kg N/ ha for barley (reference crop) as 2.0 % ''1''5N atom excess ammonium sulphate fertilizer were applied. In addition, 60.0 kgP 2 O 5 / ha were applied as triple superphosphate for all treatments. Plants were harvested at the different growth stages and than plant materials prepared for the analysis. Total nitrogen and % ''1''5N atom excess analysis were done by Kjeldahl method and Emission spectrometer, respectively. The amount of nitrogen fixation capacities of winter and spring lentil varieties were calculated according to the A-Value method (IAEA 1990). The results showed us that the winter varieties of lentil had higher dry matter yields and nitrogen fixation capacities than the spring varieties. Inoculation treatments had no statistically significant effects on the percentage of nitrogen derived from atmosphere (% Ndfa) and the amount of fixed nitrogen (kg N/ ha) for both experiments. In comparison between the harvesting times, the highest amount of fixed nitrogen was found at the pod formation stage for all cultivars. The average amounts of % Ndfa and fixed nitrogen (kg N/ ha) were 75.0 and 70.0 for winter cultivars, 70.0 and 45.0 for spring cultivars, respectively

  10. Direct and indirect costs of dinitrogen fixation in Crocosphaera watsonii WH8501 and possible implications for the nitrogen cycle

    Directory of Open Access Journals (Sweden)

    Tobias eGroßkopf

    2012-07-01

    Full Text Available The recent detection of heterotrophic nitrogen (N2 fixation in deep waters of the southern Californian and Peruvian OMZ questions our current understanding of marine N2 fixation as a process confined to oligotrophic surface waters of the oceans. In experiments with Crocosphaera watsonii WH8501, a marine unicellular diazotrophic (N2-fixing cyanobacterium, we demonstrated that the presence of high nitrate concentrations (up to 800 µM had no inhibitory effect on growth and N2 fixation over a period of two weeks. In contrast, the environmental oxygen concentration significantly influenced rates of N2 fixation and respiration, as well as carbon and nitrogen cellular content of C. watsonii over a 24 hour period. Cells grown under lowered oxygen atmosphere (5% had a higher nitrogenase activity and respired less carbon during the dark cycle than under normal oxygen atmosphere (20%. Respiratory oxygen drawdown during the dark period could be fully explained (104% by energetic needs due to basal metabolism and N2 fixation at low oxygen, while at normal oxygen these two processes could only account for 40% of the measured respiration rate. Our results revealed that under normal oxygen concentration most of the energetic costs during N2 fixation (~60% are not derived from the process of N2 fixation per se but rather from the indirect costs incurred for the removal of intracellular oxygen or by the reversal of oxidative damage (e.g. nitrogenase de novo synthesis. Theoretical calculations suggest a slight energetic advantage of N2 fixation relative to assimilatory nitrate uptake for heterotrophic and phototrophic growth, when oxygen supply is in balance with the oxygen requirement for cellular respiration (i.e. energy generation for basal metabolism and N2 fixation. Taken together our results imply the existence of a niche for diazotrophic organisms inside oxygen minimum zones, which are predicted to further expand in the future ocean.

  11. Methanogens Are Major Contributors to Nitrogen Fixation in Soils of the Florida Everglades.

    Science.gov (United States)

    Bae, Hee-Sung; Morrison, Elise; Chanton, Jeffrey P; Ogram, Andrew

    2018-04-01

    The objective of this study was to investigate the interaction of the nitrogen (N) cycle with methane production in the Florida Everglades, a large freshwater wetland. This study provides an initial analysis of the distribution and expression of N-cycling genes in Water Conservation Area 2A (WCA-2A), a section of the marsh that underwent phosphorus (P) loading for many years due to runoff from upstream agricultural activities. The elevated P resulted in increased primary productivity and an N limitation in P-enriched areas. Results from quantitative real-time PCR (qPCR) analyses indicated that the N cycle in WCA-2A was dominated by nifH and nirK / S , with an increasing trend in copy numbers in P-impacted sites. Many nifH sequences (6 to 44% of the total) and nifH transcript sequences (2 to 49%) clustered with the methanogenic Euryarchaeota , in stark contrast to the proportion of core gene sequences representing Archaea (≤0.27% of SSU rRNA genes) for the WCA-2A microbiota. Notably, archaeal nifH gene transcripts were detected at all sites and comprised a significant proportion of total nifH transcripts obtained from the unimpacted site, indicating that methanogens are actively fixing N 2 Laboratory incubations with soils taken from WCA-2A produced nifH transcripts with the production of methane from H 2 plus CO 2 and acetate as electron donors and carbon sources. Methanogenic N 2 fixation is likely to be an important, although largely unrecognized, route through which fixed nitrogen enters the anoxic soils of the Everglades and may have significant relevance regarding methane production in wetlands. IMPORTANCE Wetlands are the most important natural sources of the greenhouse gas methane, and much of that methane emanates from (sub)tropical peatlands. Primary productivity in these peatlands is frequently limited by the availability of nitrogen or phosphorus; however, the response to nutrient limitations of microbial communities that control biogeochemical cycling

  12. Favoring the unfavored: Selective electrochemical nitrogen fixation using a reticular chemistry approach.

    Science.gov (United States)

    Lee, Hiang Kwee; Koh, Charlynn Sher Lin; Lee, Yih Hong; Liu, Chong; Phang, In Yee; Han, Xuemei; Tsung, Chia-Kuang; Ling, Xing Yi

    2018-03-01

    Electrochemical nitrogen-to-ammonia fixation is emerging as a sustainable strategy to tackle the hydrogen- and energy-intensive operations by Haber-Bosch process for ammonia production. However, current electrochemical nitrogen reduction reaction (NRR) progress is impeded by overwhelming competition from the hydrogen evolution reaction (HER) across all traditional NRR catalysts and the requirement for elevated temperature/pressure. We achieve both excellent NRR selectivity (~90%) and a significant boost to Faradic efficiency by 10 percentage points even at ambient operations by coating a superhydrophobic metal-organic framework (MOF) layer over the NRR electrocatalyst. Our reticular chemistry approach exploits MOF's water-repelling and molecular-concentrating effects to overcome HER-imposed bottlenecks, uncovering the unprecedented electrochemical features of NRR critical for future theoretical studies. By favoring the originally unfavored NRR, we envisage our electrocatalytic design as a starting point for high-performance nitrogen-to-ammonia electroconversion directly from water vapor-abundant air to address increasing global demand of ammonia in (bio)chemical and energy industries.

  13. The influence of woody encroachment on the nitrogen cycle: fixation, storage and gas loss

    Science.gov (United States)

    Soper, F.; Sparks, J. P.

    2015-12-01

    Woody encroachment is a pervasive land cover change throughout the tropics and subtropics. Encroachment is frequently catalyzed by nitrogen (N)-fixing trees and the resulting N inputs potentially alter whole-ecosystem N cycling, accumulation and loss. In the southern US, widespread encroachment by legume Prosopis glandulosa is associated with increased soil total N storage, inorganic N concentrations, and net mineralization and nitrification rates. To better understand the effects of this process on ecosystem N cycling, we investigated patterns of symbiotic N fixation, N accrual and soil N trace gas and N2 emissions during Prosopis encroachment into the southern Rio Grande Plains. Analyses of d15N in foliage, xylem sap and plant-available soil N suggested that N fixation rates increase with tree age and are influenced by abiotic conditions. A model of soil N accrual around individual trees, accounting for atmospheric inputs and gas losses, generates lifetimes N fixation estimates of up to 9 kg for a 100-year-old tree and current rates of 7 kg N ha-1 yr-1. However, these N inputs and increased soil cycling rates do not translate into increased N gas losses. Two years of field measurements of a complete suite of N trace gases (ammonia, nitrous oxide, nitric oxide and other oxidized N compounds) found no difference in flux between upland Prosopis groves and adjacent unencroached grasslands. Total emissions for both land cover types average 0.56-0.65 kg N ha-1 yr-1, comparable to other southern US grasslands. Additional lab experiments suggested that N2 losses are low and that field oxygen conditions are not usually conducive to denitrification. Taken together, results suggest that this ecosystem is currently experiencing a period of net N accrual under ongoing encroachment.

  14. Metabolism of poly-β-hydroxybutyric acid in bacteroids of Rhizobium lupini in connection with nitrogen fixation and photosynthesis

    International Nuclear Information System (INIS)

    Romanov, V.I.; Fedulova, N.G.; Tchermenskaya, I.E.; Shramko, V.I.; Molchanov, M.I.; Kretovich, W.L.

    1980-01-01

    The darkening of lupin plants grown in a sand culture on a nitrogen-free medium at a stage of initial flowering led to a sharply decreased nitrogen fixation intensity which eventually ceased. Decreased intensity of nitrogen fixation in bacteroids was accompanied by an accumulation of poly-β-hydroxybutyric acid (PHB): in the course of 10-20 h (depending upon temperature) its content increased by 2.5-3.0 times. If, following darkening, the plants were once again exposed to light, an abrupt increase of nitrogen fixation intensity was observed and a simultaneous decrease of PHB content. It has been shown that lupin's exposure to light in 14 CO 2 atmosphere lasting 19 h resulted in the latter's incorporation into PHB, bacteroids and into the entire nodule; these processes developed almost in parallel. During the early period of vegetation growth prior to flowering, the PHB content of bacteroids decreased from 13 14 to 3.4% of dry weight, whereas the intensity of nitrogen fixation was raised. Concurrently increase of the activity of some enzymes connected with the PHB metabolism (aceto-acetyl-CoA-reductase, acetyl-CoA acetyl transferase PHB-depolymerase, (CoA-transferase, of 3-ketoacids) occured. The plants' subsequent ageing and reduction of nitrogen fixation intensity led to a noticeable increase of PHB content and a decrease of the above mentioned enzymes' activity. The specific activity of β-hydroxybutyric dehydrogenase involved with PHB catabolism was high and was maintained at a constant level throughout the entire vegetative period. (orig.)

  15. Biological nitrogen fixation: rates, patterns and ecological controls in terrestrial ecosystems

    Science.gov (United States)

    Vitousek, Peter M.; Menge, Duncan N.L.; Reed, Sasha C.; Cleveland, Cory C.

    2013-01-01

    New techniques have identified a wide range of organisms with the capacity to carry out biological nitrogen fixation (BNF)—greatly expanding our appreciation of the diversity and ubiquity of N fixers—but our understanding of the rates and controls of BNF at ecosystem and global scales has not advanced at the same pace. Nevertheless, determining rates and controls of BNF is crucial to placing anthropogenic changes to the N cycle in context, and to understanding, predicting and managing many aspects of global environmental change. Here, we estimate terrestrial BNF for a pre-industrial world by combining information on N fluxes with 15N relative abundance data for terrestrial ecosystems. Our estimate is that pre-industrial N fixation was 58 (range of 40–100) Tg N fixed yr−1; adding conservative assumptions for geological N reduces our best estimate to 44 Tg N yr−1. This approach yields substantially lower estimates than most recent calculations; it suggests that the magnitude of human alternation of the N cycle is substantially larger than has been assumed.

  16. Biological nitrogen fixation in relation to energy forest production. Progress report, 1978-1980

    Energy Technology Data Exchange (ETDEWEB)

    Clarholm, M; Granhall, U

    1981-01-01

    Different pasture legumes, Alnus incana and Myrica gale have been tested in pot experiments and field trials with respect to their use as biological N-fertilizers in relation to energy forest production. So far experiments have been mainly concerned with their establishemnts as on intercrop with Galix at a mire site with ombrotrophic peat and in two clayish arable soils. Laboratory experiments have been made to determine optimal conditions for growth and nitrogen fixation of wild and Alaska lupines in relation to varous soil amendments in the form of lime, ash, NPKMo, and Fe. A pilot experiment of the terrelations between willows and grey alder growing together in peat has been started at Uppsala.

  17. Regional constraints to biological nitrogen fixation in post-fire forest communities

    Science.gov (United States)

    Yelenik, Stephanie; Perakis, Steven S.; Hibbs, David

    2013-01-01

    Biological nitrogen fixation (BNF) is a key ecological process that can restore nitrogen (N) lost in wildfire and shape the pace and pattern of post-fire forest recovery. To date, there is limited information on how climate and soil fertility interact to influence different pathways of BNF in early forest succession. We studied asymbiotic (forest floor and soil) and symbiotic (the shrub Ceanothus integerrimus) BNF rates across six sites in the Klamath National Forest, California, USA. We used combined gradient and experimental phosphorus (P) fertilization studies to explore cross-site variation in BNF rates and then related these rates to abiotic and biotic variables. We estimate that our measured BNF rates 22 years after wildfire (6.1–12.1 kg N·ha-1·yr-1) are unlikely to fully replace wildfire N losses. We found that asymbiotic BNF is P limited, although this is not the case for symbiotic BNF in Ceanothus. In contrast, Ceanothus BNF is largely driven by competition from other vegetation: in high-productivity sites with high potential evapotranspiration (Et), shrub biomass is suppressed as tree biomass increases. Because shrub biomass governed cross-site variation in Ceanothus BNF, this competitive interaction led to lower BNF in sites with high productivity and Et. Overall, these results suggest that the effects of nutrients play a larger role in driving asymbiotic than symbiotic fixation across our post-fire sites. However, because symbiotic BNF is 8–90x greater than asymbiotic BNF, it is interspecific plant competition that governs overall BNF inputs in these forests.

  18. Irradiation Effect on the symbiotic fixation of nitrogen in Bean (Phaseolus vulgaris L)

    International Nuclear Information System (INIS)

    Roveda Hoyos, Gabriel; Rozo Avila, Liliana; Sierra Daza, Soraya

    1997-01-01

    The efficiency of legume - Rhizobium association is determined by biological (plant and bacteria) and environmental factors (soil and climate); for that reason, the best cultivars -Rhizobium strains combinations for each specie of legume must be selected according to the specifics environmental conditions. One of the most important sun light qualities are the irradiance levels to which the plants are exposed, because these levels have a close relation with the photosynthetic process, and also affect the biological nitrogen fixation, which has a high energetic requirements for symbiosis. The propose of this work was to determine the effect of irradiance on the Biological Nitrogen Fixation in common bean seedlings, under two environments conditions 100 and 500 moles m - 2 seg - 1 (IA and IB respectively), an nutrition control. The experimental results suggest that in the case of common bean, the irradiance requirements change depending on the Rhizobium strain that has be used in the symbiotic association. Both inoculated and non-inoculated plants with Rhizobium showed different behavior according to the levels of irradiance under which the plants were exposed. Under the irradiance of 500 moles m 2 seg - 1 (IA) the highest values of weight, area of plants, number and weight of nodules, nitrogen and phosphors content in leaves were founded, however under the lowest irradiance 100 μ moles m 2 seg - 1 (IB), the plants showed the largest root and steam, as a result of increase of bud distance, this behavior is known etiolation. The irradiance levels under which the plants are exposed determine the efficiency of symbiosis. The experimental results showed that the irradiance levels, no only affect the plant growth, but also the strains behavior. These results were easily observed in the treatments where ICA P-12 and ICA P-19 strains were used, for the dry weight of leaves, root and leaves area, number and weight of nodules, and nitrogen content of leaves in the plant. The

  19. The influence of rate and time of nitrate supply on nitrogen fixation and yield in pea (Pisum sativum L.)

    DEFF Research Database (Denmark)

    Jensen, Erik Steen

    1986-01-01

    contributed with 82, 13 and 5% of total plant N, respectively. The supply of low rates of nitrate fertilizer at sowing (“starter N”) increased the vegetative dry matter production, but not the seed yield significantly. Nitrogen fixation was not significantly decreased by the lower rates of nitrate but higher...

  20. Biological nitrogen fixation in three long-term organic and conventional arable crop rotation experiments in Denmark

    DEFF Research Database (Denmark)

    Pandey, Arjun; Li, Fucui; Askegaard, Margrethe

    2017-01-01

    Biological nitrogen (N) fixation (BNF) by legumes in organic cropping systems has been perceived as a strategy to substitute N import from conventional sources. However, the N contribution by legumes varies considerably depending on legumes species, as well as local soil and climatic conditions...

  1. Comparison of two Cellulomonas strains and their interaction with Azospirillum brasilense in degradation of wheat straw and associated nitrogen fixation

    Energy Technology Data Exchange (ETDEWEB)

    Halsall, D.M.; Gibson, A.H.

    1986-04-01

    A mutant strain of Cellulomonas sp. CS1-17 was compared with Cellulomonas gelida 2480 as the cellulolytic component of a mixed culture which was responsible for the breakdown of wheat straw to support asymbiotic nitrogen fixation by Azospirillum brasilense Sp7 (ATCC 29145). Cellulomonas sp. strain CS1-17 was more efficient than was C. gelida in cellulose breakdown at lower oxygen concentrations and, in mixed culture with A. brasilense, it supported higher nitrogenase activity(C/sub 2/H/sub 2/ reduction) and nitrogen fixation with straw as the carbon source. Based on gravimetric determinations of straw breakdown and total N determinations, the efficiency of nitrogen fixation was 72 and 63 mg of N per g of straw utilized for the mixtures containing Cellulomonas sp. and C. gelida, respectively. Both Cellulomonas spp. and Azospirillum spp. exhibited a wide range of pH tolerance. When introduced into sterilized soil, the Cellulomonas sp.-Azospirillum brasilense association was more effective in nitrogen fixation at a pH of 7.0 than at the native soil pH (5.6). This was also true of the indigenous diazotrophic microflora of this soil. The potential implications of this work to the field situation are discussed. 16 references.

  2. Nitrogen fixation (Acetylene reduction) in the sediments of the pluss-see : with special attention to the role of sedimentation

    NARCIS (Netherlands)

    Blauw, T.S.

    1987-01-01

    Sediments of productive lakes are usually rich in organic matter and, except for a thin surficial layer, anaerobic. These conditions seem to be favourable for heterotrophic nitrogen fixation. However, these sediments also contain relatively high ammonium concentrations. Ammonium represses

  3. A Medicago truncatula tobacco retrotransposon insertion mutant collection with defects in nodule development and symbiotic nitrogen fixation.

    Science.gov (United States)

    Pislariu, Catalina I; Murray, Jeremy D; Wen, JiangQi; Cosson, Viviane; Muni, RajaSekhara Reddy Duvvuru; Wang, Mingyi; Benedito, Vagner A; Andriankaja, Andry; Cheng, Xiaofei; Jerez, Ivone Torres; Mondy, Samuel; Zhang, Shulan; Taylor, Mark E; Tadege, Million; Ratet, Pascal; Mysore, Kirankumar S; Chen, Rujin; Udvardi, Michael K

    2012-08-01

    A Tnt1-insertion mutant population of Medicago truncatula ecotype R108 was screened for defects in nodulation and symbiotic nitrogen fixation. Primary screening of 9,300 mutant lines yielded 317 lines with putative defects in nodule development and/or nitrogen fixation. Of these, 230 lines were rescreened, and 156 lines were confirmed with defective symbiotic nitrogen fixation. Mutants were sorted into six distinct phenotypic categories: 72 nonnodulating mutants (Nod-), 51 mutants with totally ineffective nodules (Nod+ Fix-), 17 mutants with partially ineffective nodules (Nod+ Fix+/-), 27 mutants defective in nodule emergence, elongation, and nitrogen fixation (Nod+/- Fix-), one mutant with delayed and reduced nodulation but effective in nitrogen fixation (dNod+/- Fix+), and 11 supernodulating mutants (Nod++Fix+/-). A total of 2,801 flanking sequence tags were generated from the 156 symbiotic mutant lines. Analysis of flanking sequence tags revealed 14 insertion alleles of the following known symbiotic genes: NODULE INCEPTION (NIN), DOESN'T MAKE INFECTIONS3 (DMI3/CCaMK), ERF REQUIRED FOR NODULATION, and SUPERNUMERARY NODULES (SUNN). In parallel, a polymerase chain reaction-based strategy was used to identify Tnt1 insertions in known symbiotic genes, which revealed 25 additional insertion alleles in the following genes: DMI1, DMI2, DMI3, NIN, NODULATION SIGNALING PATHWAY1 (NSP1), NSP2, SUNN, and SICKLE. Thirty-nine Nod- lines were also screened for arbuscular mycorrhizal symbiosis phenotypes, and 30 mutants exhibited defects in arbuscular mycorrhizal symbiosis. Morphological and developmental features of several new symbiotic mutants are reported. The collection of mutants described here is a source of novel alleles of known symbiotic genes and a resource for cloning novel symbiotic genes via Tnt1 tagging.

  4. Evaluation of early nodulation and Nitrogen fixation a number of Bradyrhizobium Japonicum strains to increase nitrogen fixation ability of soybean cultivars ars by using the A-value (N-15) method

    International Nuclear Information System (INIS)

    Piervali-Bieranvand, N.; Teimori, S.; Khorasani, A.

    2004-01-01

    To date significant contribution of atmospheric N fixation to soybean nutrition and growth, is approved. Nevertheless several studies have demonstrated that effectiveness of soybean -rhizobium symbiosis is medium compared with other legumes. The time course study of biological nitrogen fixation in soybean under field conditions has been shown that soybean has limited initial fixation and fixes substantially atmospheric nitrogen just during the reproductive periods (R1 until R 5).So there is the possibility of enhancing nitrogen fixation in soybean during vegetation growth. This could be done by improving inoculation methods or breeding for early nodulation. Hence, the present study was conducted to examine the effect of some Bradyrhizobium japonicum strains on early nodulation and biological nitrogen fixation three soybean cultivars by using a-value method. The experiment, was a factorial on randomized complete block design with three replications under proper glass house condition. Treatments were harvesting times(one , two and three weeks after flowering, respectively.)soybean cultivars(Chippewa, M 112 and clay )and Bradyrhizobium japonicum strains(J 1, J 3 and J 43). Ninety-plastic pots were filled with 1.5 kg of a compound of sand and soil(1:3). Rhizobial inoculation was performed by mixing 10 ml of a suspension(Yeast extract Manitol Broth) containing about 9X10 8 cells per ml to the soil of mixing pots were kept weed-free and watered with demineralized water as well as have received every two weeks 5 ml of a solution containing all the necessary nutrients except nitrogen. For measuring biological nitrogen fixation using a-value approach, two solutions of N-15 enriched ammonium sulfate containing 10.16 and %2 N-15 atom excess in amount of 5 and 25 mg N/Kg soil were mixed with soils in each pot containing fixing and reference plants, respectively. A non-nodulation isoline of soybean C v. M 129 for the all cultivars was used as a reference crop. First harvest was

  5. History on the biological nitrogen fixation research in graminaceous plants: special emphasis on the Brazilian experience.

    Science.gov (United States)

    Baldani, José I; Baldani, Vera L D

    2005-09-01

    This review covers the history on Biological Nitrogen Fixation (BNF) in Graminaceous plants grown in Brazil, and describes research progress made over the last 40 years, most of which was coordinated by Johanna Döbereiner. One notable accomplishment during this period was the discovery of several nitrogen-fixing bacteria such as the rhizospheric (Beijerinckia fluminensis and Azotobacter paspali), associative (Azospirillum lipoferum, A. brasilense, A. amazonense) and the endophytic (Herbaspirillum seropedicae, H. rubrisubalbicans, Gluconacetobacter diazotrophicus, Burkholderia brasilensis and B. tropica). The role of these diazotrophs in association with grasses, mainly with cereal plants, has been studied and a lot of progress has been achieved in the ecological, physiological, biochemical, and genetic aspects. The mechanisms of colonization and infection of the plant tissues are better understood, and the BNF contribution to the soil/plant system has been determined. Inoculation studies with diazotrophs showed that endophytic bacteria have a much higher BNF contribution potential than associative diazotrophs. In addition, it was found that the plant genotype influences the plant/bacteria association. Recent data suggest that more studies should be conducted on the endophytic association to strengthen the BNF potential. The ongoing genome sequencing programs: RIOGENE (Gluconacetobacter diazotrophicus) and GENOPAR (Herbaspirillum seropedicae) reflect the commitment to the BNF study in Brazil and should allow the country to continue in the forefront of research related to the BNF process in Graminaceous plants.

  6. Genotypic differences in yield formation, phosphorus utilization and nitrogen fixation by cowpeas in Sierra Leone

    International Nuclear Information System (INIS)

    Amara, D.S.

    1996-01-01

    Available phosphorus (P) and nitrogen (NP) generally occur in very low amounts in soils of the tropics and subtropics. Under such conditions, most crops would require the addition of N and P fertilizer. This is not possible for small-scale farmers who cannot afford or have limited access to fertilizers, and therefore depend on low-input cropping systems. The selection of cultivars adapted to low soil nutrient conditions would sustain the production levels of subsistence farmers. Experiments were therefore conducted over a five-year period to identify cowpea cultivars with high phosphorus use efficiency and nitrogen fixation. Two of such cultivars-IT86D-1010 and IT86D-719 have been identified. Root morphological characteristics such as root length, root fineness and vesicular-arbuscular mycorrhizae are responsible for high P uptake and use efficiency. Multilocational testing of the cultivars showed that they cannot do well in areas with low rainfall. They have been distributed to farmers through the extension services for large scale production in southern Sierra Leone. (author). 28 refs, 4 figs, 6 tabs

  7. Genotypic differences in yield formation, phosphorus utilization and nitrogen fixation by cowpeas in Sierra Leone

    Energy Technology Data Exchange (ETDEWEB)

    Amara, D S [Sierra Leone Univ., Njala Univ. College, Freetown (Sierra Leone). Dept. of Soil Science; Suale, D S [Institute of Agricultural Research, Freetown (Sierra Leone)

    1996-07-01

    Available phosphorus (P) and nitrogen (NP) generally occur in very low amounts in soils of the tropics and subtropics. Under such conditions, most crops would require the addition of N and P fertilizer. This is not possible for small-scale farmers who cannot afford or have limited access to fertilizers, and therefore depend on low-input cropping systems. The selection of cultivars adapted to low soil nutrient conditions would sustain the production levels of subsistence farmers. Experiments were therefore conducted over a five-year period to identify cowpea cultivars with high phosphorus use efficiency and nitrogen fixation. Two of such cultivars-IT86D-1010 and IT86D-719 have been identified. Root morphological characteristics such as root length, root fineness and vesicular-arbuscular mycorrhizae are responsible for high P uptake and use efficiency. Multilocational testing of the cultivars showed that they cannot do well in areas with low rainfall. They have been distributed to farmers through the extension services for large scale production in southern Sierra Leone. (author). 28 refs, 4 figs, 6 tabs.

  8. Endophytic Colonization and In Planta Nitrogen Fixation by a Herbaspirillum sp. Isolated from Wild Rice Species

    Science.gov (United States)

    Elbeltagy, Adel; Nishioka, Kiyo; Sato, Tadashi; Suzuki, Hisa; Ye, Bin; Hamada, Toru; Isawa, Tsuyoshi; Mitsui, Hisayuki; Minamisawa, Kiwamu

    2001-01-01

    Nitrogen-fixing bacteria were isolated from the stems of wild and cultivated rice on a modified Rennie medium. Based on 16S ribosomal DNA (rDNA) sequences, the diazotrophic isolates were phylogenetically close to four genera: Herbaspirillum, Ideonella, Enterobacter, and Azospirillum. Phenotypic properties and signature sequences of 16S rDNA indicated that three isolates (B65, B501, and B512) belong to the Herbaspirillum genus. To examine whether Herbaspirillum sp. strain B501 isolated from wild rice, Oryza officinalis, endophytically colonizes rice plants, the gfp gene encoding green fluorescent protein (GFP) was introduced into the bacteria. Observations by fluorescence stereomicroscopy showed that the GFP-tagged bacteria colonized shoots and seeds of aseptically grown seedlings of the original wild rice after inoculation of the seeds. Conversely, for cultivated rice Oryza sativa, no GFP fluorescence was observed for shoots and only weak signals were observed for seeds. Observations by fluorescence and electron microscopy revealed that Herbaspirillum sp. strain B501 colonized mainly intercellular spaces in the leaves of wild rice. Colony counts of surface-sterilized rice seedlings inoculated with the GFP-tagged bacteria indicated significantly more bacterial populations inside the original wild rice than in cultivated rice varieties. Moreover, after bacterial inoculation, in planta nitrogen fixation in young seedlings of wild rice, O. officinalis, was detected by the acetylene reduction and 15N2 gas incorporation assays. Therefore, we conclude that Herbaspirillum sp. strain B501 is a diazotrophic endophyte compatible with wild rice, particularly O. officinalis. PMID:11679357

  9. Use of 15N enriched plant material for labelling of soil nitrogen in legume dinitrogen fixation experiments

    International Nuclear Information System (INIS)

    Jensen, E.S.

    1989-06-01

    The soil nitrogen in a field plot was labelled with nitrogen-15 (15N) by incorporating labelled plant material derived from previous experiments. The plot was used the following 3 years for determination of the amount of N2 fixed by different leguminous plants. The atom % 15N excess in grains of cereals grown as reference crops was 0.20, 0.05 and 0.03 in the 3 years, respectively. In the first year the level of enrichment was adequate for estimating symbiotic nitrogen fixation. In the second and third year lack of precision in determination of the 15N/14N ratios of legume N, may have caused an error in estimates of nitrogen fixation. About 23% of the labelled N was taken up by plants during the 3 years of cropping; after 4 years about 44% of the labelled N was found still to be present in the top soil. The labelling of the soil nitrogen with organic bound 15N, compared to adding mineral 15N at sowing, is advantageous because the labelled N is released by mineralization so that the enrichment of the plant available soil N pool become more uniform during the growth season; and high levels of mineral N, which may depress the fixation process, is avoided. (author) 7 tabs., 1 ill., 30 refs

  10. Symbiotic leghemoglobins are crucial for nitrogen fixation in legume root nodules but not for general plant growth and development

    DEFF Research Database (Denmark)

    Ott, Thomas; van Dongen, Joost T; Günther, Catrin

    2005-01-01

    Hemoglobins are ubiquitous in nature and among the best-characterized proteins. Genetics has revealed crucial roles for human hemoglobins, but similar data are lacking for plants. Plants contain symbiotic and nonsymbiotic hemoglobins; the former are thought to be important for symbiotic nitrogen...... fixation (SNF). In legumes, SNF occurs in specialized organs, called nodules, which contain millions of nitrogen-fixing rhizobia, called bacteroids. The induction of nodule-specific plant genes, including those encoding symbiotic leghemoglobins (Lb), accompanies nodule development. Leghemoglobins...... accumulate to millimolar concentrations in the cytoplasm of infected plant cells prior to nitrogen fixation and are thought to buffer free oxygen in the nanomolar range, avoiding inactivation of oxygen-labile nitrogenase while maintaining high oxygen flux for respiration. Although widely accepted...

  11. Evolutionary Dynamics of Nitrogen Fixation in the Legume–Rhizobia Symbiosis

    Science.gov (United States)

    Fujita, Hironori; Aoki, Seishiro; Kawaguchi, Masayoshi

    2014-01-01

    The stabilization of host–symbiont mutualism against the emergence of parasitic individuals is pivotal to the evolution of cooperation. One of the most famous symbioses occurs between legumes and their colonizing rhizobia, in which rhizobia extract nutrients (or benefits) from legume plants while supplying them with nitrogen resources produced by nitrogen fixation (or costs). Natural environments, however, are widely populated by ineffective rhizobia that extract benefits without paying costs and thus proliferate more efficiently than nitrogen-fixing cooperators. How and why this mutualism becomes stabilized and evolutionarily persists has been extensively discussed. To better understand the evolutionary dynamics of this symbiosis system, we construct a simple model based on the continuous snowdrift game with multiple interacting players. We investigate the model using adaptive dynamics and numerical simulations. We find that symbiotic evolution depends on the cost–benefit balance, and that cheaters widely emerge when the cost and benefit are similar in strength. In this scenario, the persistence of the symbiotic system is compatible with the presence of cheaters. This result suggests that the symbiotic relationship is robust to the emergence of cheaters, and may explain the prevalence of cheating rhizobia in nature. In addition, various stabilizing mechanisms, such as partner fidelity feedback, partner choice, and host sanction, can reinforce the symbiotic relationship by affecting the fitness of symbionts in various ways. This result suggests that the symbiotic relationship is cooperatively stabilized by various mechanisms. In addition, mixed nodule populations are thought to encourage cheater emergence, but our model predicts that, in certain situations, cheaters can disappear from such populations. These findings provide a theoretical basis of the evolutionary dynamics of legume–rhizobia symbioses, which is extendable to other single-host, multiple

  12. Nitrogen fixation by free-living microorganisms in tropical rice soils using labelled fertilizer. Part of a coordinated programme on isotope techniques in studies of biological nitrogen fixation for the dual purpose of increasing crop production and decreasing nitrogen fertilizer use to conserve the environment

    International Nuclear Information System (INIS)

    Rao, V.R.

    1981-11-01

    Both acetylene-reduction and 15 N techniques were used to study heterotrophic N fixation in the rhizosphere of rice plants. Soils subjected to flooding in 4 soil types in both greenhouse and the field were found to stimulate greater heterotrophic nitrogen fixation than moist soils. The addition of organic materials, in particular, cellulose and rice straw, in general, enhanced nitrogen fixed by heterotrophic organisms living in the rhizosphere of rice plants. The highest amount of N fixed was 38 kg N/ha, and was obtained in a flooded lateritic soil to which had been added cellulose. Heterotrophic nitrogen fixation was influenced by soil type. In this study, the lowest value for fixed N was recorded in an acid sulphate soil of low pH. The addition of increasing amounts of inorganic nitrogen fertilizer in the form of ammonium sulphate suppressed rhizospheric nitrogen fixation in all soils, but the extent of suppression differed in the different soils. Benomyl fungicide and methyl carbamate insecticide had a stimulatory effect on heterotrophic nitrogen fixation in soils under rice roots. Different rice cultivars stimulated strains of Azospirillum to varying extent, and thus did not fix nitrogen to the same extent. It is thus possible that varieties of rice could be selected on the basis of their ability to support non-symbiotic N fixation in their rhizosphere

  13. Oxygen-Poor Microzones as Potential Sites of Microbial N2 Fixation in Nitrogen-Depleted Aerobic Marine Waters

    Science.gov (United States)

    Paerl, Hans W.; Prufert, Leslie E.

    1987-01-01

    The nitrogen-deficient coastal waters of North Carolina contain suspended bacteria potentially able to fix N2. Bioassays aimed at identifying environmental factors controlling the development and proliferation of N2 fixation showed that dissolved organic carbon (as simple sugars and sugar alcohols) and particulate organic carbon (derived from Spartina alterniflora) additions elicited and enhanced N2 fixation (nitrogenase activity) in these waters. Nitrogenase activity occurred in samples containing flocculent, mucilage-covered bacterial aggregates. Cyanobacterium-bacterium aggregates also revealed N2 fixation. In all cases bacterial N2 fixation occurred in association with surficial microenvironments or microzones. Since nitrogenase is oxygen labile, we hypothesized that the aggregates themselves protected their constituent microbes from O2. Microelectrode O2 profiles revealed that aggregates had lower internal O2 tensions than surrounding waters. Tetrazolium salt (2,3,5-triphenyl-3-tetrazolium chloride) reduction revealed that patchy zones existed both within microbes and extracellularly in the mucilage surrounding microbes where free O2 was excluded. Triphenyltetrazolium chloride reduction also strongly inhibited nitrogenase activity. These findings suggest that N2 fixation is mediated by the availability of the appropriate types of reduced microzones. Organic carbon enrichment appears to serve as an energy and structural source for aggregate formation, both of which were required for eliciting N2 fixation responses of these waters. Images PMID:16347337

  14. Compartmentalized microbial composition, oxygen gradients and nitrogen fixation in the gut of Odontotaenius disjunctus.

    Science.gov (United States)

    Ceja-Navarro, Javier A; Nguyen, Nhu H; Karaoz, Ulas; Gross, Stephanie R; Herman, Donald J; Andersen, Gary L; Bruns, Thomas D; Pett-Ridge, Jennifer; Blackwell, Meredith; Brodie, Eoin L

    2014-01-01

    Coarse woody debris is an important biomass pool in forest ecosystems that numerous groups of insects have evolved to take advantage of. These insects are ecologically important and represent useful natural analogs for biomass to biofuel conversion. Using a range of molecular approaches combined with microelectrode measurements of oxygen, we have characterized the gut microbiome and physiology of Odontotaenius disjunctus, a wood-feeding beetle native to the eastern United States. We hypothesized that morphological and physiological differences among gut regions would correspond to distinct microbial populations and activities. In fact, significantly different communities were found in the foregut (FG), midgut (MG)/posterior hindgut (PHG) and anterior hindgut (AHG), with Actinobacteria and Rhizobiales being more abundant toward the FG and PHG. Conversely, fermentative bacteria such as Bacteroidetes and Clostridia were more abundant in the AHG, and also the sole region where methanogenic Archaea were detected. Although each gut region possessed an anaerobic core, micron-scale profiling identified radial gradients in oxygen concentration in all regions. Nitrogen fixation was confirmed by (15)N2 incorporation, and nitrogenase gene (nifH) expression was greatest in the AHG. Phylogenetic analysis of nifH identified the most abundant transcript as related to Ni-Fe nitrogenase of a Bacteroidetes species, Paludibacter propionicigenes. Overall, we demonstrate not only a compartmentalized microbiome in this beetle digestive tract but also sharp oxygen gradients that may permit aerobic and anaerobic metabolism to occur within the same regions in close proximity. We provide evidence for the microbial fixation of N2 that is important for this beetle to subsist on woody biomass.

  15. A novel endo-hydrogenase activity recycles hydrogen produced by nitrogen fixation.

    Science.gov (United States)

    Ng, Gordon; Tom, Curtis G S; Park, Angela S; Zenad, Lounis; Ludwig, Robert A

    2009-01-01

    Nitrogen (N(2)) fixation also yields hydrogen (H(2)) at 1:1 stoichiometric amounts. In aerobic diazotrophic (able to grow on N(2) as sole N-source) bacteria, orthodox respiratory hupSL-encoded hydrogenase activity, associated with the cell membrane but facing the periplasm (exo-hydrogenase), has nevertheless been presumed responsible for recycling such endogenous hydrogen. As shown here, for Azorhizobium caulinodans diazotrophic cultures open to the atmosphere, exo-hydrogenase activity is of no consequence to hydrogen recycling. In a bioinformatic analysis, a novel seven-gene A. caulinodans hyq cluster encoding an integral-membrane, group-4, Ni,Fe-hydrogenase with homology to respiratory complex I (NADH: quinone dehydrogenase) was identified. By analogy, Hyq hydrogenase is also integral to the cell membrane, but its active site faces the cytoplasm (endo-hydrogenase). An A. caulinodans in-frame hyq operon deletion mutant, constructed by "crossover PCR", showed markedly decreased growth rates in diazotrophic cultures; normal growth was restored with added ammonium--as expected of an H(2)-recycling mutant phenotype. Using A. caulinodans hyq merodiploid strains expressing beta-glucuronidase as promoter-reporter, the hyq operon proved strongly and specifically induced in diazotrophic culture; as well, hyq operon induction required the NIFA transcriptional activator. Therefore, the hyq operon is constituent of the nif regulon. Representative of aerobic N(2)-fixing and H(2)-recycling alpha-proteobacteria, A. caulinodans possesses two respiratory Ni,Fe-hydrogenases: HupSL exo-hydrogenase activity drives exogenous H(2) respiration, and Hyq endo-hydrogenase activity recycles endogenous H(2), specifically that produced by N(2) fixation. To benefit human civilization, H(2) has generated considerable interest as potential renewable energy source as its makings are ubiquitous and its combustion yields no greenhouse gases. As such, the reversible, group-4 Ni,Fe-hydrogenases, such

  16. Genotypic Variation in Phosphorus Use Efficiency for Symbiotic Nitrogen Fixation in Voandzou (Vigna Subterranea)

    Energy Technology Data Exchange (ETDEWEB)

    Andriamananjara, A.; Rabeharisoa, L. [Laboratoire des Radio-isotopes, Universite d' Antananarivo, Antananarivo (Madagascar); Abdou, M. Malam [Laboratoire Banques de genes CERRA / KOLLO, Institut National de Recherche Agronomique du Niger (INRAN), Niamey (Niger); Masse, D. [Institut de Recherche pour le Developpement, UMR Eco and Sols, Montpellier, (France); Amenc, L.; Pernot, C.; Drevon, J. J. [Institut National de la Recherche Agronomique, UMR Eco and Sols, Montpellier (France)

    2013-11-15

    Vigna subterranea, known as voandzou or Bambara groundnut as an African indigenous crop which is often neglected or under-used in African subsistence agriculture. Preliminary research and country perceptions have shown its agronomic and nutritional properties, in particular under atypical climates of arid and tropical areas, and in saline soils. There is a high potential to increase the production by optimizing symbiotic nitrogen fixation (SNF) through effective inoculation even in nitrate-rich environments. In this study, Vigna subterranea inoculated with the reference strain of Bradyrhizobium sp. Vigna CB756 was studied in order to assess the symbiotic fixation potential of different cultivars and landraces of Madagascar, Niger and Mali under low-P and sufficient-P conditions. Six voandzou cultivars inoculated with Bradyrhizobium sp. Vigna CB756, were grown under hydroaeroponic culture for 6 weeks supplied with four phosphorus levels of 15, 30, 75 and 250 {mu}mol plant{sup -1} week{sup -1} in order to establish the response curve of voandzou to P supply, and to induce P deficient and sufficient levels. In another experiment five tolerant cultivars with high SNF and five sensitive cultivars with low SNF were chosen after a preliminary screening of 54 voandzou genotypes, including 50 landraces from Madagascar, Niger and Mali supplied with 2 P levels as P deficient and P sufficient (30 and 75 {mu}mol plant{sup -1} week{sup -1} ) under hydroaeroponic conditions. Genotypic variation in SFN for the high phosphorus use efficiency (PUE) was observed among the 54 cultivars and landraces. Variability was especially related to the nodule and shoot biomass, nodule permeability, nodule respiration and gene phytase expression. Contrasting cultivars and landraces in terms of PUE for SNF were selected for further evaluation under field conditions. (author)

  17. Biological Nitrogen Fixation by Legumes and N Uptake by Coffee Plants

    Directory of Open Access Journals (Sweden)

    Eduardo de Sá Mendonça

    Full Text Available ABSTRACT Green manures are an alternative for substituting or supplementing mineral nitrogen fertilizers. The aim of this study was to quantify biological N fixation (BNF and the N contribution derived from BNF (N-BNF to N levels in leaves of coffee intercropped with legumes grown on four family farms located in the mountainous region of the Atlantic Forest Biome in the state of Minas Gerais, Brazil. The following green manures were evaluated: pinto peanuts (Arachis pintoi, calopo (Calopogonium mucunoides, crotalaria (Crotalaria spectabilis, Brazilian stylo (Stylosanthes guianensis, pigeon pea (Cajanus cajan, lablab beans (Dolichos lablab, and velvet beans (Stizolobium deeringianum, and spontaneous plants. The experimental design was randomized blocks with a 4 × 8 factorial arrangement (four agricultural properties and eight green manures, and four replications. One hundred grams of fresh matter of each green manure plant were dried in an oven to obtain the dry matter. We then performed chemical and biochemical characterizations and determined the levels of 15N and 14N, which were used to quantify BNF through the 15N (δ15N natural abundance technique. The legumes C. mucunoides, S. guianensis, C. cajan, and D. lablab had the highest rates of BNF, at 46.1, 45.9, 44.4, and 42.9 %, respectively. C. cajan was the legume that contributed the largest amount of N (44.42 kg ha-1 via BNF.C. cajan, C. spectabilis, and C. mucunoides transferred 55.8, 48.8, and 48.1 %, respectively, of the N from biological fixation to the coffee plants. The use of legumes intercropped with coffee plants is important in supplying N, as well as in transferring N derived from BNF to nutrition of the coffee plants.

  18. Genotypic Variation in Phosphorus Use Efficiency for Symbiotic Nitrogen Fixation in Cowpea (Vigna Unguiculata)

    Energy Technology Data Exchange (ETDEWEB)

    Andriamananjara, A. [LRI-SRA, Laboratoire des Radio-isotopes, Universite d' Antananarivo, Antananarivo (Madagascar); Abdou, M. Malam [Laboratoire Banques de genes CERRA / KOLLO, Institut National de Recherche Agronomique du Niger (INRAN), Niamey (Niger); Pernot, C.; Drevon, J. J. [Institut National de la Recherche Agronomique, UMR Eco and Sols, Montpellier (France)

    2013-11-15

    Cowpea (Vigna unguiculata L. Walp) is an important food legume. In Africa, it is mostly cultivated under such environmental constraints as drought and pest, and nutrient deficiency. In particular low soil phosphorus strongly limits crop production for the poor farmers with limited access to P fertilizers. Therefore breeding cowpea for the tolerance to P deficiency is considered as an alternative to increase the productivity of traditional cowpea-cereal cropping systems in soils with low P availability. This paper reports cowpea genotypic-variation in P use efficiency for symbiotic nitrogen fixation as a contribution to select tolerant cowpea lines under P deficiency. Eighty cowpea cultivars inoculated with the reference strain of Bradyrhizobium sp. Vigna CB756 were pre-screened as a single replicate under hydroaeroponic culture for 6 weeks under P deficiency versus P sufficiency, namely 15 vs 30 {mu}mol plant{sup -1} week{sup -1}. Large variability in nodule number per plant, and in shoot growth as a function of nodule mass, was observed among the diversity of cowpea lines. From this pre-screening experiment, the 40 cowpea lines showing the highest SNF-potential, i.e. high nodulation linked with high N{sub 2}-dependent growth under P sufficiency, and the most contrasting tolerance to P deficiency, i.e. highest vs lowest N{sub 2}-dependent growth under P deficiency, were grown again in glasshouse hydroaeroponics with 6 replicates. As an illustration of the most contrasting lines, the nodulation was decreased under P deficiency by less than 20% for IT82E-18 whereas by more than 80% for IT95K-1105-5 or SUVITA 2. The variations in nodulation were correlated with variations in growth with mean value of additional growth per unit increase in nodule biomass of 23 g shoot DW g-1 nodule DW under P sufficiency, showing 3 lines showing exceptionally high potential for symbiotic nitrogen fixation, versus 28 g shoot DW g{sup -1} nodule DW showing large variation among lines

  19. The interactive effects of temperature and moisture on nitrogen fixation in two temperate-arctic mosses

    DEFF Research Database (Denmark)

    Rousk, Kathrin; Pedersen, Pia Agerlund; Dyrnum, Kristine

    2017-01-01

    fixation in mosses under controlled conditions have rarely been investigated separately, rendering the interactive effects of the two climatic factors on N2 fixation unknown. Here, we tested the interactive effects of temperature and moisture on N2 fixation in the two most dominant moss species...

  20. Potential for Nitrogen Fixation and Nitrification in the Granite-Hosted Subsurface at Henderson Mine, CO

    Science.gov (United States)

    Swanner, Elizabeth D.; Templeton, Alexis S.

    2011-01-01

    The existence of life in the deep terrestrial subsurface is established, yet few studies have investigated the origin of nitrogen that supports deep life. Previously, 16S rRNA gene surveys cataloged a diverse microbial community in subsurface fluids draining from boreholes 3000 feet deep at Henderson Mine, CO, USA (Sahl et al., 2008). The prior characterization of the fluid chemistry and microbial community forms the basis for the further investigation here of the source of NH4+. The reported fluid chemistry included N2, NH4+ (5–112 μM), NO2− (27–48 μM), and NO3− (17–72 μM). In this study, the correlation between low NH4+ concentrations in dominantly meteoric fluids and higher NH4+ in rock-reacted fluids is used to hypothesize that NH4+ is sourced from NH4+-bearing biotite. However, biotite samples from the host rocks and ore-body minerals were analyzed by Fourier transform infrared (FTIR) microscopy and none-contained NH4+. However, the nitrogenase-encoding gene nifH was successfully amplified from DNA of the fluid sample with high NH4+, suggesting that subsurface microbes have the capability to fix N2. If so, unregulated nitrogen fixation may account for the relatively high NH4+ concentrations in the fluids. Additionally, the amoA and nxrB genes for archaeal ammonium monooxygenase and nitrite oxidoreductase, respectively, were amplified from the high NH4+ fluid DNA, while bacterial amoA genes were not. Putative nitrifying organisms are closely related to ammonium-oxidizing Crenarchaeota and nitrite-oxidizing Nitrospira detected in other subsurface sites based upon 16S rRNA sequence analysis. Thermodynamic calculations underscore the importance of NH4+ as an energy source in a subsurface nitrification pathway. These results suggest that the subsurface microbial community at Henderson is adapted to the low nutrient and energy environment by their capability of fixing nitrogen, and that fixed nitrogen may support subsurface biomass via

  1. Comparative sequence analysis of nitrogen fixation-related genes in six legumes

    Directory of Open Access Journals (Sweden)

    Dong Hyun eKim

    2013-08-01

    Full Text Available Legumes play an important role as food and forage crops in international agriculture especially in developing countries. Legumes have a unique biological process called nitrogen fixation (NF by which they convert atmospheric nitrogen to ammonia. Although legume genomes have undergone polyploidization, duplication and divergence, NF-related genes, because of their essential functional role for legumes, might have remained conserved. To understand the relationship of divergence and evolutionary processes in legumes, this study analyzes orthologs and paralogs for selected 20 NF-related genes by using comparative genomic approaches in six legumes i.e. Medicago truncatula (Mt, Cicer arietinum, Lotus japonicus, Cajanus cajan (Cc, Phaseolus vulgaris (Pv and Glycine max (Gm. Subsequently, sequence distances, numbers of synonymous substitutions per synonymous site (Ks and nonsynonymous substitutions per nonsynonymous site (Ka between orthologs and paralogs were calculated and compared across legumes. These analyses suggest the closest relationship between Gm and Cc and the farthest distance between Mt and Pv in 6 legumes. Ks proportional plots clearly showed ancient genome duplication in all legumes, whole genome duplication event in Gm and also speciation pattern in different legumes. This study also reported some interesting observations e.g. no peak at Ks 0.4 in Gm-Gm, location of two independent genes next to each other in Mt and low Ks values for outparalogs for three genes as compared to other 12 genes. In summary, this study underlines the importance of NF-related genes and provides important insights in genome organization and evolutionary aspects of six legume species analyzed.

  2. An Amorphous Noble-Metal-Free Electrocatalyst that Enables Nitrogen Fixation under Ambient Conditions.

    Science.gov (United States)

    Lv, Chade; Yan, Chunshuang; Chen, Gang; Ding, Yu; Sun, Jingxue; Zhou, Yansong; Yu, Guihua

    2018-02-23

    N 2 fixation by the electrocatalytic nitrogen reduction reaction (NRR) under ambient conditions is regarded as a potential approach to achieve NH 3 production, which still heavily relies on the Haber-Bosch process at the cost of huge energy and massive production of CO 2 . A noble-metal-free Bi 4 V 2 O 11 /CeO 2 hybrid with an amorphous phase (BVC-A) is used as the cathode for electrocatalytic NRR. The amorphous Bi 4 V 2 O 11 contains significant defects, which play a role as active sites. The CeO 2 not only serves as a trigger to induce the amorphous structure, but also establishes band alignment with Bi 4 V 2 O 11 for rapid interfacial charge transfer. Remarkably, BVC-A shows outstanding electrocatalytic NRR performance with high average yield (NH 3 : 23.21 μg h -1  mg -1 cat. , Faradaic efficiency: 10.16 %) under ambient conditions, which is superior to the Bi 4 V 2 O 11 /CeO 2 hybrid with crystalline phase (BVC-C) counterpart. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Biological fixation and nitrogen transfer by three legume species in mango and soursop organic orchards

    International Nuclear Information System (INIS)

    Paulino, Gleicia Miranda; Barroso, Deborah Guerra

    2009-01-01

    The objective of this work was to evaluate the biological nitrogen fixation (BNF) and the N transfer derived from BNF of the legume species - Gliricidia sepium (gliricidia), Crotalaria juncea (sunnhemp) and Cajanus cajan (pigeon pea) - for an intercropped organic orchard with mango and soursop, through the 15 N natural abundance method. The following inter cropping systems were evaluated: mango and soursop with gliricidia; mango and soursop with sunnhemp; mango and soursop with pigeon pea; and mango and soursop as control. Gliricidia showed the highest BNF potential (80%) , followed by sunnhemp (64.5%) and pigeon pea (45%). After two sunnhemp prunes, 149.5 kg ha -1 of N per year were supplied, with 96.5 kg derived from BNF. After three annual prunes, gliricidia supplied 56.4 and 80.3 kg ha -1 of N per year, with 45 and 64 kg derived from BNF, in two consecutive years. The quantity of N supplied to the system was higher than the mango and soursop requirements. Variations in the natural abundance of 15 N were found only in soursop leaves. Gliricidia and sunnhemp were prominent in N transfer, with approximately 22.5 and 40% respectively. Green manuring using gliricidia permits fractioning of the N supply, which is an advantage in N obtention by the fruit trees (author)

  4. Biological nitrogen fixation in the oxygen-minimum region of the eastern tropical North Pacific ocean.

    Science.gov (United States)

    Jayakumar, Amal; Chang, Bonnie X; Widner, Brittany; Bernhardt, Peter; Mulholland, Margaret R; Ward, Bess B

    2017-10-01

    Biological nitrogen fixation (BNF) was investigated above and within the oxygen-depleted waters of the oxygen-minimum zone of the Eastern Tropical North Pacific Ocean. BNF rates were estimated using an isotope tracer method that overcame the uncertainty of the conventional bubble method by directly measuring the tracer enrichment during the incubations. Highest rates of BNF (~4 nM day -1 ) occurred in coastal surface waters and lowest detectable rates (~0.2 nM day -1 ) were found in the anoxic region of offshore stations. BNF was not detectable in most samples from oxygen-depleted waters. The composition of the N 2 -fixing assemblage was investigated by sequencing of nifH genes. The diazotrophic assemblage in surface waters contained mainly Proteobacterial sequences (Cluster I nifH), while both Proteobacterial sequences and sequences with high identities to those of anaerobic microbes characterized as Clusters III and IV type nifH sequences were found in the anoxic waters. Our results indicate modest input of N through BNF in oxygen-depleted zones mainly due to the activity of proteobacterial diazotrophs.

  5. Purification and binding analysis of the nitrogen fixation regulatory NifA protein from Azospirillum brasilense

    Directory of Open Access Journals (Sweden)

    L.M.P. Passaglia

    1998-11-01

    Full Text Available NifA protein activates transcription of nitrogen fixation operons by the alternative sigma54 holoenzyme form of RNA polymerase. This protein binds to a well-defined upstream activator sequence (UAS located at the -200/-100 position of nif promoters with the consensus motif TGT-N10-ACA. NifA of Azospirillum brasilense was purified in the form of a glutathione-S-transferase (GST-NifA fusion protein and proteolytic release of GST yielded inactive and partially soluble NifA. However, the purified NifA was able to induce the production of specific anti-A. brasilense NifA-antiserum that recognized NifA from A. brasilense but not from K. pneumoniae. Both GST-NifA and NifA expressed from the E. coli tac promoter are able to activate transcription from the nifHDK promoter but only in an A. brasilense background. In order to investigate the mechanism that regulates NifA binding capacity we have used E. coli total protein extracts expressing A. brasilense nifA in mobility shift assays. DNA fragments carrying the two overlapping, wild-type or mutated UAS motifs present in the nifH promoter region revealed a retarded band of related size. These data show that the binding activity present in the C-terminal domain of A. brasilense NifA protein is still functional even in the presence of oxygen.

  6. Crystallization of a flavodoxin involved in nitrogen fixation in Rhodobacter capsulatus

    Energy Technology Data Exchange (ETDEWEB)

    Pérez-Dorado, Inmaculada [Grupo de Cristalografía Macromolecular y Biología Estructural, Instituto de Química-Física Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain); Bortolotti, Ana; Cortez, Néstor [Instituto de Biología Molecular y Celular de Rosario (Universidad Nacional de Rosario y CONICET), Suipacha 531, S2002LRK Rosario (Argentina); Hermoso, Juan A., E-mail: xjuan@iqfr.csic.es [Grupo de Cristalografía Macromolecular y Biología Estructural, Instituto de Química-Física Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain)

    2008-05-01

    The flavodoxin NifF from R. capsulatus, a candidate for nitrogenase reduction during nitrogen fixation, has been crystallized using the hanging-drop vapour-diffusion method. Preliminary X-ray data processing at 2.17 Å resolution allowed determination of the crystal system and unit-cell parameters. Flavodoxins are small electron-transfer proteins that contain one molecule of noncovalently bound flavin mononucleotide (FMN). The flavodoxin NifF from the photosynthetic bacterium Rhodobacter capsulatus is reduced by one electron from ferredoxin/flavodoxin:NADP(H) reductase and was postulated to be an electron donor to nitrogenase in vivo. NifF was cloned and overexpressed in Escherichia coli, purified and concentrated for crystallization using the hanging-drop vapour-diffusion method at 291 K. Crystals grew from a mixture of PEG 3350 and PEG 400 at pH 5.5 and belong to the tetragonal space group P4{sub 1}2{sub 1}2, with unit-cell parameters a = b = 66.49, c = 121.32 Å. X-ray data sets have been collected to 2.17 Å resolution.

  7. Crystallization of a flavodoxin involved in nitrogen fixation in Rhodobacter capsulatus

    International Nuclear Information System (INIS)

    Pérez-Dorado, Inmaculada; Bortolotti, Ana; Cortez, Néstor; Hermoso, Juan A.

    2008-01-01

    The flavodoxin NifF from R. capsulatus, a candidate for nitrogenase reduction during nitrogen fixation, has been crystallized using the hanging-drop vapour-diffusion method. Preliminary X-ray data processing at 2.17 Å resolution allowed determination of the crystal system and unit-cell parameters. Flavodoxins are small electron-transfer proteins that contain one molecule of noncovalently bound flavin mononucleotide (FMN). The flavodoxin NifF from the photosynthetic bacterium Rhodobacter capsulatus is reduced by one electron from ferredoxin/flavodoxin:NADP(H) reductase and was postulated to be an electron donor to nitrogenase in vivo. NifF was cloned and overexpressed in Escherichia coli, purified and concentrated for crystallization using the hanging-drop vapour-diffusion method at 291 K. Crystals grew from a mixture of PEG 3350 and PEG 400 at pH 5.5 and belong to the tetragonal space group P4 1 2 1 2, with unit-cell parameters a = b = 66.49, c = 121.32 Å. X-ray data sets have been collected to 2.17 Å resolution

  8. Influence of arbuscular mycorrhizae on biomass production and nitrogen fixation of berseem clover plants subjected to water stress.

    Directory of Open Access Journals (Sweden)

    Sergio Saia

    Full Text Available Several studies, performed mainly in pots, have shown that arbuscular mycorrhizal symbiosis can mitigate the negative effects of water stress on plant growth. No information is available about the effects of arbuscular mycorrhizal symbiosis on berseem clover growth and nitrogen (N fixation under conditions of water shortage. A field experiment was conducted in a hilly area of inner Sicily, Italy, to determine whether symbiosis with AM fungi can mitigate the detrimental effects of drought stress (which in the Mediterranean often occurs during the late period of the growing season on forage yield and symbiotic N2 fixation of berseem clover. Soil was either left under water stress (i.e., rain-fed conditions or the crop was well-watered. Mycorrhization treatments consisted of inoculation of berseem clover seeds with arbuscular mycorrhizal spores or suppression of arbuscular mycorrhizal symbiosis by means of fungicide treatments. Nitrogen biological fixation was assessed using the 15N-isotope dilution technique. Arbuscular mycorrhizal symbiosis was able to mitigate the negative effect of water stress on berseem clover grown in a typical semiarid Mediterranean environment. In fact, under water stress conditions, arbuscular mycorrhizal symbiosis resulted in increases in total biomass, N content, and N fixation, whereas no effect of crop mycorrhization was observed in the well-watered treatment.

  9. Effect of saline water on growth, yield and N2 fixation by faba bean and lentil plants using nitrogen-15

    International Nuclear Information System (INIS)

    Gadalla, A.M.; Galal, Y.G.M.; Elakel, E.A.; Ismail, H.; Hamdy, A.

    2003-01-01

    This work had been carried out under greenhouse conditions through joint research project between international agronomic mediterranean (IAM, Bari), italy and soils and water dept., Egyptian atomic energy authority. The aim of this dy was to assess the effect of saline water irrigation on growth, yield and nitrogen fixation (% Ndfa) by faba bean and lentil plants inoculated with selected rhizobium strains. Four saline irrigation water levels (fresh water, 3.6 and ds/m) were used. 20 kg N/ha as ammonium sulfate contained 10% N-15 atom excess was applied for quantification of biological N-fixation N-portions derived from fertilizer (Ndff). Results showed that high levels of salinity negatively affected seed yield and N accumulated in tissue of faba bean. Similar trend was noticed with dry matter of lentil while shoot-N was increased at 6 and 9 ds/m. Both leguminous crops were mainly dependent on N 2 fixation as an important source of nitrogen nutrition. Under adverse conditions salinity, the plants gained some of their N requirements from the other two N sources (Ndff and Ndfs). Application of the suitable Rhizobium bacteria strains could be beneficial for both the plant growth and soil fertility via N 2 fixation

  10. Influence of arbuscular mycorrhizae on biomass production and nitrogen fixation of berseem clover plants subjected to water stress.

    Science.gov (United States)

    Saia, Sergio; Amato, Gaetano; Frenda, Alfonso Salvatore; Giambalvo, Dario; Ruisi, Paolo

    2014-01-01

    Several studies, performed mainly in pots, have shown that arbuscular mycorrhizal symbiosis can mitigate the negative effects of water stress on plant growth. No information is available about the effects of arbuscular mycorrhizal symbiosis on berseem clover growth and nitrogen (N) fixation under conditions of water shortage. A field experiment was conducted in a hilly area of inner Sicily, Italy, to determine whether symbiosis with AM fungi can mitigate the detrimental effects of drought stress (which in the Mediterranean often occurs during the late period of the growing season) on forage yield and symbiotic N2 fixation of berseem clover. Soil was either left under water stress (i.e., rain-fed conditions) or the crop was well-watered. Mycorrhization treatments consisted of inoculation of berseem clover seeds with arbuscular mycorrhizal spores or suppression of arbuscular mycorrhizal symbiosis by means of fungicide treatments. Nitrogen biological fixation was assessed using the 15N-isotope dilution technique. Arbuscular mycorrhizal symbiosis was able to mitigate the negative effect of water stress on berseem clover grown in a typical semiarid Mediterranean environment. In fact, under water stress conditions, arbuscular mycorrhizal symbiosis resulted in increases in total biomass, N content, and N fixation, whereas no effect of crop mycorrhization was observed in the well-watered treatment.

  11. Nitrogen fixation in peanut nodules during dark periods and detopped conditions with special reference to lipid bodies

    International Nuclear Information System (INIS)

    Siddique, A.M.; Bal, A.K.

    1991-01-01

    The peanut plant (Arachis hypogaea L.), unlike other known legumes, can sustain nitrogen fixation when prolonged periods of darkness or detopping curtail the supply of photosynthate to the nodule. This ability to withstand photosynthate stress is attributed to the presence of lipid bodies in infected nodule cells. In both dark-treated and detopped plants, the lipid bodies show a gradual decrease in numbers, suggesting their utilization as a source of energy and carbon for nitrogen fixation. Lipolytic activity can be localized in the lipid bodies, and the existence of β-oxidation pathway and glyoxylate cycle is shown by the release of 14 CO 2 from 14 C lineoleoyl coenzyme A by the nodule homogenate

  12. Agrobacterium rhizogenes transformed soybean roots differ in their nodulation and nitrogen fixation response to genistein and salt stress.

    Science.gov (United States)

    Dolatabadian, Aria; Modarres Sanavy, Seyed Ali Mohammad; Ghanati, Faezeh; Gresshoff, Peter M

    2013-07-01

    We evaluated response differences of normal and transformed (so-called 'hairy') roots of soybean (Glycine max L. (Merr.), cv L17) to the Nod-factor inducing isoflavone genistein and salinity by quantifying growth, nodulation, nitrogen fixation and biochemical changes. Composite soybean plants were generated using Agrobacterium rhizogenes-mediated transformation of non-nodulating mutant nod139 (GmNFR5α minus) with complementing A. rhizogenes K599 carrying the wild-type GmNFR5α gene under control of the constitutive CaMV 35S promoter. We used genetic complementation for nodulation ability as only nodulated roots were scored. After hairy root emergence, primary roots were removed and composite plants were inoculated with Bradyrhizobium japonicum (strain CB1809) pre-induced with 10 μM genistein and watered with NaCl (0, 25, 50 and 100 mM). There were significant differences between hairy roots and natural roots in their responses to salt stress and genistein application. In addition, there were noticeable nodulation and nitrogen fixation differences. Composite plants had better growth, more root volume and chlorophyll as well as more nodules and higher nitrogenase activity (acetylene reduction) compared with natural roots. Decreased lipid peroxidation, proline accumulation and catalase/peroxidase activities were found in 'hairy' roots under salinity stress. Genistein significantly increased nodulation and nitrogen fixation and improved roots and shoot growth. Although genistein alleviated lipid peroxidation under salinity stress, it had no significant effect on the activity of antioxidant enzymes. In general, composite plants were more competitive in growth, nodulation and nitrogen fixation than normal non-transgenic even under salinity stress conditions.

  13. MtZIP6 is a novel metal transporter required for symbiotic nitrogen fixation in nodules of Medicago truncatula plants

    OpenAIRE

    Saez Somolinos, Ángela; Imperial Ródenas, Juan; Gonzalez Guerrero, Manuel

    2015-01-01

    Symbiotic nitrogen fixation (SNF) carried out by the interaction rhizobia-legumes takes place in legume root nodules. Many of the enzymes involved in SNF are metalloproteins that obtain their metal cofactor from the host plant. Metals reach the nodule through the vasculature, where they are released in the apoplast on the infection/differentiation zone (zone II) of the nodule (Rodriguez-Haas et al., 2013). From there, these oligonutrients have to cross a number of membranes to be used for met...

  14. Growth-promoting Sphingomonas paucimobilis ZJSH1 associated with Dendrobium officinale through phytohormone production and nitrogen fixation

    Science.gov (United States)

    Yang, Suijuan; Zhang, Xinghai; Cao, Zhaoyun; Zhao, Kaipeng; Wang, Sai; Chen, Mingxue; Hu, Xiufang

    2014-01-01

    Growth-promoting Sphingomonas paucimobilis ZJSH1, associated with Dendrobium officinale, a traditional Chinese medicinal plant, was characterized. At 90 days post-inoculation, strain ZJSH1 significantly promoted the growth of D. officinale seedlings, with increases of stems by 8.6% and fresh weight by 7.5%. Interestingly, the polysaccharide content extracted from the inoculated seedlings was 0.6% higher than that of the control. Similar growth promotion was observed with the transplants inoculated with strain ZJSH1. The mechanism of growth promotion was attributed to a combination of phytohormones and nitrogen fixation. Strain ZJSH1 was found using the Kjeldahl method to have a nitrogen fixation activity of 1.15 mg l−1, which was confirmed by sequencing of the nifH gene. Using high-performance liquid chromatography-mass spectrometry, strain ZJSH1 was found to produce various phytohormones, including salicylic acid (SA), indole-3-acetic acid (IAA), Zeatin and abscisic acid (ABA). The growth curve showed that strain ZJSH1 grew well in the seedlings, especially in the roots. Accordingly, much higher contents of SA, ABA, IAA and c-ZR were detected in the inoculated seedlings, which may play roles as both phytohormones and ‘Systemic Acquired Resistance’ drivers. Nitrogen fixation and secretion of plant growth regulators (SA, IAA, Zeatin and ABA) endow S. paucimobilis ZJSH1 with growth-promoting properties, which provides a potential for application in the commercial growth of D. officinale. PMID:25142808

  15. EnviroAtlas - Biological nitrogen fixation in natural/semi-natural ecosystems by 12-digit HUC for the Conterminous United States, 2006

    Data.gov (United States)

    U.S. Environmental Protection Agency — This EnviroAtlas dataset contains data on the mean biological nitrogen fixation in natural/semi-natural ecosystems per 12-digit Hydrologic Unit (HUC) in 2006....

  16. A novel endo-hydrogenase activity recycles hydrogen produced by nitrogen fixation.

    Directory of Open Access Journals (Sweden)

    Gordon Ng

    Full Text Available BACKGROUND: Nitrogen (N(2 fixation also yields hydrogen (H(2 at 1:1 stoichiometric amounts. In aerobic diazotrophic (able to grow on N(2 as sole N-source bacteria, orthodox respiratory hupSL-encoded hydrogenase activity, associated with the cell membrane but facing the periplasm (exo-hydrogenase, has nevertheless been presumed responsible for recycling such endogenous hydrogen. METHODS AND FINDINGS: As shown here, for Azorhizobium caulinodans diazotrophic cultures open to the atmosphere, exo-hydrogenase activity is of no consequence to hydrogen recycling. In a bioinformatic analysis, a novel seven-gene A. caulinodans hyq cluster encoding an integral-membrane, group-4, Ni,Fe-hydrogenase with homology to respiratory complex I (NADH: quinone dehydrogenase was identified. By analogy, Hyq hydrogenase is also integral to the cell membrane, but its active site faces the cytoplasm (endo-hydrogenase. An A. caulinodans in-frame hyq operon deletion mutant, constructed by "crossover PCR", showed markedly decreased growth rates in diazotrophic cultures; normal growth was restored with added ammonium--as expected of an H(2-recycling mutant phenotype. Using A. caulinodans hyq merodiploid strains expressing beta-glucuronidase as promoter-reporter, the hyq operon proved strongly and specifically induced in diazotrophic culture; as well, hyq operon induction required the NIFA transcriptional activator. Therefore, the hyq operon is constituent of the nif regulon. CONCLUSIONS: Representative of aerobic N(2-fixing and H(2-recycling alpha-proteobacteria, A. caulinodans possesses two respiratory Ni,Fe-hydrogenases: HupSL exo-hydrogenase activity drives exogenous H(2 respiration, and Hyq endo-hydrogenase activity recycles endogenous H(2, specifically that produced by N(2 fixation. To benefit human civilization, H(2 has generated considerable interest as potential renewable energy source as its makings are ubiquitous and its combustion yields no greenhouse gases. As

  17. Yield and biological nitrogen fixation of cowpea varieties in the semi-arid region of Brazil

    International Nuclear Information System (INIS)

    Santiago de Freitas, Ana Dolores; Fernandes Silva, Acácia; Valadares de Sá Barretto Sampaio, Everardo

    2012-01-01

    Cowpea is an important crop in small properties of the Brazilian semi-arid region, where it is cultivated without fertilizer application. In spite of the fundamental role played by biological Nitrogen fixation (BNF), little is known of the symbiosis between cowpea varieties and native rhizobia or recommended rhizobia strains. A field experiment was conducted aiming to estimate BNF and productivities of local varieties, in association with two previously described bradyrhizobial inoculant strains and native rhizobia (no inoculation). The plants received 20 kg ha −1 of enriched 15 N fertilizer to allow the use of the isotopic dilution method. After harvest (80 days) straw and grain biomass was determined. The varieties differed in grain and straw productivity and in N and N derived from atmosphere (%Ndfa). Corujinha had the highest grain productivity (1147 kg ha −1 ), followed by Sempre Verde (920 kg ha −1 ), Azul (912 kg ha −1 ) and Cariri (889 kg ha −1 ). Costela de Vaca had the highest straw productivity (2258 kg ha −1 ), highest N content in the straw (28 g ha −1 ) and highest BNF (79 %Ndfa, corresponding to 45 kg ha −1 of N for total aboveground biomass and 39 kg ha −1 for the straw), but the lowest grain productivity (381 kg ha −1 ) and the lowest harvest index (0.14). The inoculations did not significantly alter productivities, N contents or %Ndfa but there was a tendency of lower grain productivities in the non-inoculated plants, which was reflected in lower total and biologically fixed N quantities, indicating that the native strains may be slightly less efficient. -- Highlights: ► We estimate N fixation and productivities of local cowpea varieties in Brazil. ► Plants were inoculated or not with two recommended rhizobia strains. ► All local varieties had high proportions of their N derived from the air (%Ndfa). ► They differed in BNF in grain and straw productivity. ► Inoculation did not alter productivities or %Ndfa but

  18. The value of symbiotic nitrogen fixation by grain legumes in comparison to the cost of nitrogen fertilizer used in developing countries

    International Nuclear Information System (INIS)

    Hardarson, G.; Bunning, S.; Montanez, A.; Roy, R.; MacMillan, A.

    2001-01-01

    A great challenge lies in devising more sustainable farming systems without compromising food production levels and food security. Obviously, increasing productivity is necessary to accommodate growth in the global population. World wide, the environmental factors that most severely restrict plant growth are the availability of water and nitrogen. The challenges in developing countries are to find ways of meeting this additional nitrogen demand without concomitant degrading natural productivity. Widespread adoption of biological nitrogen fixation (BNF) would contribute to this goal. BNF, together with adequate N management in the ecosystem, appears to be the most promising alternative to increasing the use of inorganic fertiliser nitrogen. BNF technologies represent economic, sustainable and environmentally friendly means of ensuring the nitrogen requirement of an agro-ecosystem. Here we investigate the value of BNF by grain legumes and compares it to the cost of nitrogen fertilizer used in developing countries. Our data show that major grain legumes fix approximately 11.1 million metric tons of nitrogen per annum in developing countries. If this N was supplied by inorganic fertiliser one would have to apply at least double that amount to achieve the same yields, and this would cost approximately 6.7 billion US dollars. As the eight major grain legumes grown in developing countries contribute 30 - 40% of the annual N requirement the contribution of BNF is of great economic and environmental importance. (author)

  19. Nitrite fixation by humic substances: Nitrogen-15 nuclear magnetic resonance evidence for potential intermediates in chemodenitrification

    Science.gov (United States)

    Thorn, K.A.; Mikita, M.A.

    2000-01-01

    Studies have suggested that NO2/-, produced during nitrification and denitrification, can become incorporated into soil organic matter and, in one of the processes associated with chemodenitrification, react with organic matter to form trace N gases, including N2O. To gain an understanding of the nitrosation chemistry on a molecular level, soil and aquatic humic substances were reacted with 15N-labeled NaNO2, and analyzed by liquid phase 15N and 13C nuclear magnetic resonance (NMR). The International Humic Substances Society (IHSS) Pahokee peat and peat humic acid were also reacted with Na15NO2 and analyzed by solid-state 15N NMR. In Suwannee River, Armadale, and Laurentian fulvic acids, phenolic rings and activated methylene groups underwent nitrosation to form nitrosophenols (quinone monoximes) and ketoximes, respectively. The oximes underwent Beckmann rearrangements to 2??amides, and Beckmann fragmentations to nitriles. The nitriles in turn underwent hydrolysis to 1??amides. Peaks tentatively identified as imine, indophenol, or azoxybenzene nitrogens were clearly present in spectra of samples nitrosated at pH 6 but diminished at pH 3. The 15N NMR spectrum of the peat humic acid exhibited peaks corresponding with N-nitroso groups in addition to nitrosophenols, ketoximes, and secondary Beckmann reaction products. Formation of N-nitroso groups was more significant in the whole peat compared with the peat humic acid. Carbon-13 NMR analyses also indicated the occurrence of nitrosative demethoxylation in peat and soil humic acids. Reaction of 15N-NH3 fixated fulvic acid with unlabeled NO2/- resulted in nitrosative deamination of aminohydroquinone N, suggesting a previously unrecognized pathway for production of N2 gas in soils fertilized with NH3.Studies have suggested that NO2-, produced during nitrification and denitrification, can become incorporated into soil organic matter and, in one of the processes associated with chemodenitrification, react with organic

  20. Long-term warming and litter addition affects nitrogen fixation in a subarctic heath

    DEFF Research Database (Denmark)

    Sørensen, Pernille Lærkedal; Michelsen, Anders

    2011-01-01

    the measurements. We analyzed N fixation rates on both whole-ecosystem level and specifically on two moss species: Sphagnum warnstorfii and Hylocomium splendens. The whole-ecosystem N fixation of the warmed plots almost tripled compared with the control plots. However, in the Sphagnum and Hylocomium mosses we...

  1. Determination of symbiotic nitrogen fixation by labelling the soil atmosphere with sup(15)N sub(2) at low isotope enrichment

    International Nuclear Information System (INIS)

    Trivelin, P.C.O.

    1982-01-01

    A direct method to determine the total symbiotic nitrogen fixation during the leguminous plants cycles has been, developed, by labelling the soil atmosphere with sup(15)N sub(2) at low isotope enrichment, of about 1 atom % excess. The soil explored by the root system of leguminous plants was confined by means of a chamber in the field and by sealed pots in greenhouse experiments in order to maintain the soil air labelled with sup(15)N sub(2). The average sup(15)N concentration in the soil atmosphere, necessary to calculate dinitrogen fixation, was obtained by integration of the exponential functions of isotope dilution. Those functions were obtained by periodic sampling and analysis of the N sub(2) in the soil atmosphere. The field experiment with labelled atmosphere was carried out from the 22 sup(nd) to the 31 sup(st) day of the bean crop cycle and 5.5 mg N/plant (24% of total plant N) was derived from fixation. In pot experiments, under greenhouse conditions, integrated determination of fixation was made in Phaseolus beans (from the 19 sup(th) to the 67 sup(th) day from planting) and in soybeans (from the 24 sup(th) to the 70 sup(th) day from planting). The soil atmosphere was labelled with sup(15)N sub(2) in both cases. Average fixation obtained for Phaseolus beans was 80 mg N/plant (65% of total plant N) and for soybeans 265 mg N/plant (71% of total plant N). Evaluation of the basic concept of the isotope dilution method to determine nitrogen fixation in pots experiments, as proposed by Fried and Middelboe (1977) has also been made in the present paper. Simultaneous determinations of fixation in soybeans, using the isotope dilution method of Fried and Middelboe, natural variation of the sup(15)N/ sup(14)N ratios, and total-N differences, indicated the same results for pot experiments, harvested at the end of the plant cycle. (author)

  2. Comparisons between three nitrogen fertilizers (nitric, ammoniacal and uric) in an andic soil of the Comoro Islands. Studies in a controlled medium with nitrogen 15

    International Nuclear Information System (INIS)

    Egoumenides, C.; Pichot, J.; Haribou, A.

    1980-01-01

    The fixation rate (nitrogen in the plant + nitrogen remaining in the soil) was measured for nitrogen from three different labelled fertilizers: calcium nitrate, ammonium sulfate and urea. This experiment, which was realized in pots with and without cultures led to the following observations: the same fixation rates occur for all fertilizers, which are greater when cultures are employed then when they are not employed (86% ans 72% respectively); the utilization rate of nitrogen fertilizers by plants is significantly higher with the nitric form of fertilizer than with the two other forms (73% and 63% respectively). With cultures, the nitrogen nonutilized by the plant is found in nitrogen organic forms of the soil. On the other hand, in the case of bare soil, the reorganization of nitrogen fertilizers (above all nitric fertilizers) is found to be highly limited, the greatest proportion of the fertilizer's nitrogen remaining in the mineral form [fr

  3. Elevated Atmospheric CO2 and Warming Stimulates Growth and Nitrogen Fixation in a Common Forest Floor Cyanobacterium under Axenic Conditions

    Directory of Open Access Journals (Sweden)

    Zoë Lindo

    2017-03-01

    Full Text Available The predominant input of available nitrogen (N in boreal forest ecosystems originates from moss-associated cyanobacteria, which fix unavailable atmospheric N2, contribute to the soil N pool, and thereby support forest productivity. Alongside climate warming, increases in atmospheric CO2 concentrations are expected in Canada’s boreal region over the next century, yet little is known about the combined effects of these factors on N fixation by forest floor cyanobacteria. Here we assess changes in N fixation in a common forest floor, moss-associated cyanobacterium, Nostoc punctiforme Hariot, under elevated CO2 conditions over 30 days and warming combined with elevated CO2 over 90 days. We measured rates of growth and changes in the number of specialized N2 fixing heterocyst cells, as well as the overall N fixing activity of the cultures. Elevated CO2 stimulated growth and N fixation overall, but this result was influenced by the growth stage of the cyanobacteria, which in turn was influenced by our temperature treatments. Taken together, climate change factors of warming and elevated CO2 are expected to stimulate N2 fixation by moss-associated cyanobacteria in boreal forest systems.

  4. Measurement of nitrogen fixation in beam (Phaseolus vulgaris L.) cv. carioca, using a 15N2 low enrichment method

    International Nuclear Information System (INIS)

    Trivelin, P.C.O.; Matsui, E.; Saito, S.M.T.; Libardi, P.L.; Salati, E.

    1984-01-01

    A experimental work under field conditions to develop a method to measure atmospheric N 2 -fixation by leguminous plants, using a low enrichment 15 N 2 technique, is carried out. The experiment was developed using a N 2 -fixation measuring chamber on Terra Roxa Estruturada. The beam plants had their aereal part under normal conditions and the rooting system confined, through which a mixture of Ar, O 2 and N 2 labelled with 15 N (1.9% atom excess) was circulated from the 22nd to the 31st day from planting. Samples of the gaseous Ar, O 2 and N 2 mixture were analysed by mass spectrometry to determine 15 N concentrations and O 2 and CO 2 contents. The N 2 -fixed was measured by determination of total-N and isotopic concentration of nitrogen in the plants. (M.A.C.) [pt

  5. New, national bottom-up estimate for tree-based biological nitrogen fixation in the US

    Science.gov (United States)

    Nitrogen is a limiting nutrient in many ecosystems, but is also a chief pollutant from human activity. Quantifying human impacts on the nitrogen cycle and investigating natural ecosystem nitrogen cycling both require an understanding of the magnitude of nitrogen inputs from biolo...

  6. Growth and Nitrogen Fixation in Silicon and/or Potassium Fed Chickpeas Grown under Drought and Well Watered Conditions

    Directory of Open Access Journals (Sweden)

    Fawaz Kurdali

    2013-08-01

    Full Text Available A pot experiment was conducted to study the effects of silicon (Si and/or potassium (K on plant growth, nitrogen uptake and N2-fixation in water stressed (FC1 and well watered (FC2 chickpea plants using 15N and 13C isotopes. Three fertilizer rates of Si (Si50, Si100 and Si200 and one fertilizer rate of K were used. For most of the growth parameters, it was found that Si either alone or in combination with K was more effective to alleviate water stress than K alone. Increasing soil water level from FC1 to FC2 often had a positive impact on values of almost all studied parameters. The Si100K+ (FC1 and Si50K+ (FC2 treatments gave high enough amounts of N2-fixation, higher dry matter production and greater nitrogen yield. The percent increments of total N2-fixed in the above mentioned treatments were 51 and 47% over their controls, respectively. On the other hand, increasing leave’s dry matter in response to the solely added Si (Si50K- and Si100K- is associated with lower Δ13C under both watering regimes. This may indicate that Si fertilization had a beneficial effect on water use efficiency (WUE. Hence, Δ13C could be an adequate indicator of WUE in response to the exogenous supply of silicon to chickpea plants. Our results highlight that Si is not only involved in amelioration of growth and in maintaining of water status but it can be also considered an important element for the symbiotic performance of chickpea plants. It can be concluded that the synergistic effect of silicon and potassium fertilization with adequate irrigation improves growth and nitrogen fixation in chickpea plants.

  7. Fertilizer nitrogen fixation in plants and its transmutation in soils in case of annual application

    International Nuclear Information System (INIS)

    Shilova, E.I.; Smirnov, P.M.; Khon, N.I.

    1974-01-01

    Using certain combinations of 15 N labeled and unlabeled nitrogen-containing fertilizers data were obtained for direct determination of nitrogen balance in the year of fertilization and subsequently. Annual and total (for 3 years) increment in utilization of soil nitrogen resulting from repeated fertilization was also determined. Coefficient of nitrogen utilization by barley decreased over the 3-year period after additional application of ammonium sulfate while biological immobilization of nitrogen tended to increase. Application of straw during the first year of the experiment did not significantly affect the nitrogen balance in the following years. The total coefficient of nitrogen utilization for the 2 to 3-year period was higher than that of the first year while biological immobilization was relatively lower. Additional utilization of soil nitrogen as compared to the control was the same over the whole 3-year period; additional mobilization (annual and total) was relatively higher due to lower removal of soil nitrogen in the subsequent years. Utilization of previously immobilized nitrogen was higher in the case of repeated fertilization than without application of nitrogen fertilizers. The content of newly immobilized nitrogen during 3 years in the hydrolyzable undistilable fraction (nitrogen of bounded amino acids) was relatively lower and this was accompanied by the growth of hydrolyzable distilable and unhydrolyzable nitrogen

  8. History on the biological nitrogen fixation research in graminaceous plants: special emphasis on the Brazilian experience

    Directory of Open Access Journals (Sweden)

    José I. Baldani

    2005-09-01

    Full Text Available This review covers the history on Biological Nitrogen Fixation (BNF in Graminaceous plants grown in Brazil, and describes research progress made over the last 40 years, most of whichwas coordinated by Johanna Döbereiner. One notable accomplishment during this period was the discovery of several nitrogen-fixing bacteria such as the rhizospheric (Beijerinckia fluminensis and Azotobacter paspali, associative (Azospirillum lipoferum, A. brasilense, A. amazonense and the endophytic (Herbaspirillum seropedicae, H. rubrisubalbicans, Gluconacetobacter diazotrophicus, Burkholderia brasilensis and B. tropica. The role of these diazotrophs in association with grasses, mainly with cereal plants, has been studied and a lot of progress has been achieved in the ecological, physiological, biochemical, and genetic aspects. The mechanisms of colonization and infection of the plant tissues are better understood, and the BNF contribution to the soil/plant system has been determined. Inoculation studies with diazotrophs showed that endophytic bacteria have a much higher BNF contribution potential than associative diazotrophs. In addition, it was found that the plant genotype influences the plant/bacteria association. Recent data suggest that more studies should be conducted on the endophytic association to strengthen the BNF potential. The ongoing genome sequencing programs: RIOGENE (Gluconacetobacter diazotrophicus and GENOPAR (Herbaspirillum seropedicae reflect the commitment to the BNF study in Brazil and should allow the country to continue in the forefront of research related to the BNF process in Graminaceous plants.A presente revisão aborda a história da Fixação Biológica de Nitrogênio (FBN em Gramíneas no Brasil, procurando mostrar a evolução da pesquisa na área iniciada a mais de 40 anos sob a liderança da pesquisadora Johanna Döbereiner. Um aspecto marcante deste período foi a descoberta de diversas bactérias fixadoras de nitrogênio atmosf

  9. Soil-N tagging - a method for measurement of biological nitrogen fixation in cereal-legume intercropping system

    International Nuclear Information System (INIS)

    Patra, D.D.; Subbiah, B.V.; Sachdev, M.S.

    1985-01-01

    The quantitative estimates of atmospheric dinitrogen fixed by the legume crop and transferred to the associated cereal in cereal-legume intercropping system of maize-cowpea and wheat-gram using soil and fertilizer nitrogen labelling with 15 N have been reported. The estimates of N-fixation have been compared with the similar data from A-value method. Under field conditions sole cropped cowpea fixed 53.7 per cent of its total N uptake while as intercrop with maize fixed 43.5 per cent. Maize crop got 27.6 per cent of its total N uptake by transference of the nitrogen fixed by the intercropped cowpea. In the wheat-gram intercropping system the corresponding values under greenhouse conditions were 35.0, 44.8 and 20.2 per cent, respectively. (author)

  10. Utilisation of CO2, fixation of nitrogen and exhaust gas cleaning in electric discharge with electrode catalysis

    International Nuclear Information System (INIS)

    Marcela, M.; Imrich, M.; Mario, J.

    2001-01-01

    The method reported here provides a contribution to CO 2 utilisation, nitrogen fixation and combustion exhaust cleaning using synergetic effect of electric discharge with heterogeneous catalysis on electrodes. The efficiency of CO 2 removal is about 40-65%. The process of CO 2 removal is always accompanied by NO x , VOC, SX and other component removal and is connected with O 2 formation. The final product of process is powder with fractal microstructure, low specific weight, water insoluble suitable for use as nitrogen containing fertilizer. The main component (95%) of solid product is amorphous condensate of amino acids with about 5% of metal organic compound with catalytic properties. The condensate has character of statistical proteinoid. Its creation seems to play important role during formation of life in pre-biotic Earth

  11. The use of the 15N isotope dilution technique to estimate the contribution of associated biological nitrogen fixation to the nitrogen nutrition of Paspalum notatum cv. batatais

    International Nuclear Information System (INIS)

    Boddey, R.M.; Doebereiner, Johanna

    1983-01-01

    This paper reports the results of a field experiment to investigate the use of the 15 N-dilution technique to measure the contribution of biological N 2 fixation to the N nutrition of the batatais cultivar of Paspalum notatum. The pensacola cultivar of this grass supports little associated N 2 fixation as evidenced by the low associated C 2 H 2 reduction activity and was thus used as a nonfixing control plant. The grasses were grown in 60-cm diameter concrete cylinders sunk into the soil, and the effects of four different addition rates of labelled nitrogen (NH 4 ) 2 SO 4 , were investigated. The data from seven harvests clearly demonstrated that there was a significant input of plant associated N 2 fixation to the nutrition of the batatais cultivar amounting to approximately 20 kg N ha -1 year -1 . Problems associated with the conduct of such isotope dilution experiments are discussed including the importance of using nonfixing control plants of similar growth habit, the advantages and disadvantages of growing the plants in cylinders as opposed to field plots, and the various methods of application of labelled N fertilizer

  12. The effect of vesicular-arbuscular mycorrhiza isolated from Syrian soil on alfalfa growth and nitrogen fixation in saline soil

    International Nuclear Information System (INIS)

    El Atrash, F

    2001-01-01

    The influence of vesicular - arbuscular Mycorrhiza fungi (VAM) on symbiotic fixation of N 2 n alfalfa plants has been observed. Beneficial effects of study the effect of VAM or phosphorous fertilization on alfalfa (Medicago sativa L,) yields, umber of nodules and N 2 fixation by N 15 isotope dilution at different salinity levels. This experiment was realized in green house conditions, using soil of 2.3 dsm -1 conductivity mixed with sand (5: 2V) for alfalfa plants growing at various levels of phosphorus, or infected by Mycorrhiza fungi. Different conductivities (13.18, 22.2, 28.8, 43.5 dsm -1 ) were applied on these treatment by increasing concentrations of Nacl, CaCl 2 and MgCl 2 and MgCl 2 by salinity soil irrigation. Ten days after planting, soil was enriched with 2 ppm of (NH 4 15 ) 2 SO 4 . Plant were grown under greenhouse condition for ten weeks. Our results confirmed that increased salinity reduced nitrogen - fixation and the number of nodules. The negative effect with increasing salinity was less in Mycorrhiza plants than in plants fertilized with various levels of phosphorus, and only the higher levels of salinity reduced significantly, the percentage of Mycorrhiza colonization, However, at all levels of salinity, VAM stimulated plant growth and nutrient uptake. (author)

  13. The influence of phosphorus deficiency on growth and nitrogen fixation of white clover plants

    OpenAIRE

    Høgh-Jensen, Dr Henning; Schjoerring, Dr Jan K.; Soussana, Dr Jean-Francois

    2002-01-01

    The effects of P deficiency on growth, N2‐fixation and photosynthesis in white clover (Trifolium repens L.) plants were investigated using three contrasting relative addition rates of P, or following abrupt withdrawal of the P supply. Responses to a constant below‐optimum P supply rate consisted of a decline in N2‐fixation per unit root weight and a small reduction in the efficiency with which electrons were allocated to the reduction of N2 in nodules. Abrupt removal of P arrested nodule grow...

  14. Nitrogen fixation and effects of pruning on Gliricidia sepium and Leucaena leucocephala

    International Nuclear Information System (INIS)

    Liyanage, M.S. de

    1998-01-01

    This 7-year study examined genetic variability in N 2 fixation by Gliricidia sepium and the N 2 -fixing capacity in G. sepium and Leucaena leucocephala as influenced by frequency of pruning, age, and shade from coconut. The 15 N-dilution method was used with the non-nodulating tree legume Senna siamea as the non-fixing reference. There were significant differences in total dry matter, N yield and N 2 -fixation capacity among four G. sepium provenances. Gliricidia had higher values than Leucaena for dry matter, N yield, and amount of N fixed; %Ndfa was comparable in both species (47-55%). A substantial amount (18%) of fixed N 2 was present in the roots of both species. In a long-term study aimed at comparing the effect of pruning practices and age of trees, G. sepium grown under coconut outperformed L. leucocephala in terms of dry matter, N yield and amounts of N 2 fixation. Coconut saplings supplied with G. sepium and L. leucocephala prunings as green manure grew better than those supplied with S. siamea; the fraction of coconut-sapling N obtained from Gliricidia and Leucaena was 40 and 36%, respectively. These results suggest that G. sepium, which demonstrated a high potential for biomass production and N 2 fixation, is appropriate for interplanting with coconut palms. Also, S. Siamea was found to be a suitable reference species. (author)

  15. Incorporation of nitrogen from N2 fixation into amino acids of zooplankton

    DEFF Research Database (Denmark)

    Loick-Wilde, Natalie; Dutz, Jörg; Miltner, Anja

    2012-01-01

    quantified the direct incorporation of 15N tracer from N2-fixing N. spumigena (diazotroph nitrogen) and ammonium-utilizing R. salina into the amino acid nitrogen (AA-N) of zooplankton using complementary gas chromatography– combustion–isotope ratio mass spectrometry, gas chromatography–mass spectrometry...... consistently low in E. affinis when exposed to N. spumigena, suggesting that these animals were reluctant to feed on N. spumigena. Essential isoleucine received most of the diazotroph nitrogen in field zooplankton, while nonessential amino acids received most 15N tracer in E. affinis. N. spumigena was clearly...... an important amino acid nitrogen source for Baltic Sea zooplankton...

  16. Symbiotic Nitrogen Fixation in Alfalfa (Medicago Sativa L.) by Sinorhizobium Meliloti at Al-Qassim Regions, Saudi Arabia

    International Nuclear Information System (INIS)

    Al-Barakah, F. N.; Mridha, M. A. U.

    2016-01-01

    The nodulation status in alfalfa (Medicago sativa L.) plants by Sinorhizobium meliloti under Saudi field condition was assessed in some selected farms in four seasons for two years. In the present study, we also monitored the introduced S. meliloti strains activity under Saudi soil conditions. The samples were collected at regular seasonal intervals from the selected farms. The total number of nodules, morphology of the nodules and the effectiveness of N/sub 2/-fixation was assessed. In general, it was revealed that soils in the selected areas in Saudi Arabia have sufficient bacteria of the proper types to nodulate the alfalfa plants. These nodules are high in number, small in size and white in color. The nodules obtained from most of the selected farms are ineffective for nitrogen fixation. Inoculation of alfalfa seeds with imported S. meliloti strains failed to fix the atmospheric nitrogen sufficiently and also the growth improvement of alfalfa plants. There was a wide variation in the occurrence of number of nodules among the four seasons in two years. It was also observed that summer season severely affected the nodulation making it nearly zero. This low number of nodules exerts a very slow recovery of nodule formation in the next year. The introduced strains were always over competing with the native strains but they did not survive because of hot and dry summer. Nitrogenase activity of the nodules collected from both the inoculated and non-inoculated farms were always very low in all the collected samples, which indicates that the ability of fixing nitrogen by S. meliloti strains in alfalfa under Saudi soils conditions is very low. (author)

  17. Basin scale variability of active diazotrophs and nitrogen fixation in the North Pacific, from the tropics to the subarctic Bering Sea

    Science.gov (United States)

    Shiozaki, Takuhei; Bombar, Deniz; Riemann, Lasse; Hashihama, Fuminori; Takeda, Shigenobu; Yamaguchi, Tamaha; Ehama, Makoto; Hamasaki, Koji; Furuya, Ken

    2017-06-01

    Nitrogen-fixing microorganisms (diazotrophs) provide biologically available nitrogen to plankton communities and thereby greatly influence the productivity in many marine regions. Various cyanobacterial groups have traditionally been considered the major oceanic diazotrophs, but later noncyanobacterial and presumably heterotrophic diazotrophs were also found to be widespread and potentially important in nitrogen fixation. However, the distribution and activity of different diazotroph groups is still poorly constrained for most oceanic ecosystems. Here we examined diazotroph community structure and activity along a 7500 km south-north transect between the central equatorial Pacific and the Bering Sea. Nitrogen fixation contributed up to 84% of new production in the upper waters of the subtropical gyre, where the diazotroph community included the gammaproteobacterium γ-24774A11 and highly active cyanobacterial phylotypes (>50% of total nifH transcript abundance). Nitrogen fixation was sometimes detectable down to 150 m depth and extended horizontally to the edge of the gyre at around 35°N. Nitrogen fixation was even detected far north on the Bering Sea shelf. In the Alaskan Coastal Waters on the Bering Sea shelf, low nitrate together with high dissolved iron concentrations seemed to foster diazotroph growth, including a prominent role of UCYN-A2, which was abundant near the surface (1.2×105 nifH gene copies L-1). Our study provides evidence for nitrogen fixation in the Bering Sea and suggests a clear contrast in the composition of diazotrophs between the tropical/subtropical gyre and the separate waters in the cold northern regions of the North Pacific.

  18. Appraisal of the nitrogen-15 natural-abundance method for quantifying dinitrogen fixation

    International Nuclear Information System (INIS)

    Bremer, E.; van Kessel, C.

    1990-01-01

    Several investigators have questioned the use of the 15 N natural-abundance method of estimating N 2 fixation because of variability in soil δ 15 N and small differences between the δ 15 N of soil N and atmospheric N. Investigations were conducted to compare the 15 N natural-abundance and 15 N-isotope-dilution methods for estimating N 2 fixation of field-grown pea (Pisum sativum L.) and lentil (Lens culinaris Medik.). Spatial variability was assessed at three sites by determining the δ 15 N of non-N 2 -fixing plants. Seasonal variation in δ 15 N for spring and winter wheat (Triticum aestivum L.), flax (Linum usitatissimum L.), barley (Hordeum vulgare L.), rape (Brassica napus L.) and lentil was determined at one site. Comparisons between δ 15 N and 15 N-enriched isotope-dilution methods for estimating N 2 fixation by lentil were conducted at several sites over a 3-yr period. Variability in δ 15 N of the reference plant was site dependent: the δ 15 N ranged from 2.8 to 9.3 at the first site, 3.4 to 8.8 at the second site, and 3.5 to 6.2 at the third site. The average δ 15 N of four of the five non-N 2 -fixing plants increased from 5.4 at 42 d after planting to 6.9 at the final harvest. The fifth non-N 2 -fixing plant, rape, accumulated most of its N during the first 42 d after planting, and its δ 15 N value declined from 8.1 at 42 d after planting to 7.3 at the final harvest. Estimates of N 2 fixation were not significantly different in 18 out of 21 comparisons; in two comparisons in the δ 15 N method and in one comparison the 15 N-enriched method provided higher estimates of N 2 fixation. Overall, both methods appeared to provide equally reliable estimates of N 2 fixation for lentil

  19. The role of symbiotic nitrogen fixation in nitrogen availability, competition and plant invasion into the sagebrush steppe

    Science.gov (United States)

    Erin M. Goergen

    2009-01-01

    In the semi-arid sagebrush steppe of the Northeastern Sierra Nevada, resources are both spatially and temporally variable, arguably making resource availability a primary factor determining invasion success. N fixing plant species, primarily native legumes, are often relatively abundant in sagebrush steppe and can contribute to ecosystem nitrogen budgets. ...

  20. Comparison of inoculant and indigenous rhizobial dinitrogen fixation in cowpeas by direct nitrogen-15 analyses

    International Nuclear Information System (INIS)

    ElHassan, G.A.; Focht, D.D.

    1986-01-01

    Soil that contained 15 N enriched organic matter (0.461 % 15 N) was used to determine competitiveness of six strains at different logarithmic inoculum densities against indigenous rhizobia and against a previous surviving inoculant (strain P132). Analyses of N content of plant tissues by direct 15 N technique showed that cowpeas (Vigna unguiculata L. Walp.) were capable of deriving 60 to 98% of shoot N from N 2 fixation. The two fast-growing strains (176A26 and 176A28) were poorer competitors and fixed less N 2 compared to the other slow-growing strains. Inoculum density had no effect upon yield response of cowpeas, but inoculation with strains P132, 401, and 22A1 effected greater seed yield, shoot dry matter, total N, and percentage of N derived from fixation (86-98%) than other strains and the uninoculated control (60-73%). By contrast, N 2 fixation and yield parameters in inoculated cowpeas were not significantly different from inoculated controls that contained residual P132 from a previous inoculum study. The higher hydrogen uptake (Hup) efficiency of nodules containing residual P132 (98 ± 2%) facilitated presumptive identification of P132 (100% ± 0 Hup efficiency axenically) as the surviving and infecting inoculant strain since nodules infected by indigenous rhizobia had lower Hup efficiencies (88 ± 2%)

  1. Quantification of root associated nitrogen fixation in kallar grass as estimated by sup/15/nitrogen isotope dilution

    International Nuclear Information System (INIS)

    Malik, K.A.; Zafar, Y.

    1985-01-01

    Present investigations were made by using sup/15/N isotope dilution technique to quantitatively estimate BNF in Kallar grass when grown under controlled conditions in nutrient solution and inoculated with N sub/2/-fixing bacteria. Azospirillum brasilense and two isolates from the rhizosphere of kallar grass were used as inoculant. After harvest acetylen reduction of roots, total yield, total N and sup/15/ N analysis were made. Total-N in inoculated treatments was 2-3 times higher than in control and so were the fresh and dry weight yields. The estimates based on isotopic dilution indicated that 50-70 percent N in the plant was derived from BNF in case of inoculated treatment. The results based on N balance gave relatively lower values of 40-60 percent of total N derived from fixation. The data revealed that in Kallar grass a substantial amount of plant N is derived from BNF. (orig./A.B.)

  2. Use of 15N-isotope dilution for quantification of nitrogen fixation in Saccharum SPP

    International Nuclear Information System (INIS)

    Singh, M.; Singh, G.B.; Joshi, B.B.

    1994-01-01

    The objectives of present study were to quantify and compare the amount of nitrogen fixed by diazotrophes associated with roots of Saccharum spontaneum, S. barberi and S. sinense using Sclerotachya fusca as a non-fixing control. 5 refs

  3. Nitrogen fixation by Gliricidia sepium: decomposition of its leaves in soil and effects on sweet-corn yields

    International Nuclear Information System (INIS)

    Zaharah, A.R.; Sharifuddin, H.A.H.; Anular, R.; Bah, A.R.; Mwange, K.Nk.; Kathuli, P.; Juma, P.

    1998-01-01

    Nitrogen fixation by Gliricidia sepium subjected to three pruning regimes (one, two or four cuts per year) was measured using the 15 N-dilution technique with Cassia siamea as the reference species. Over a 4-year period, estimates of the fraction of N derived from fixation, generally 2 fixer. Gliricidia sepium leaves were placed in litter-bags, buried in an ultisol and sampled at intervals over 70 days. The half-life for dry matter was 17 days, and about 60% of the N was lost within 10 days; K and Ca were the most rapidly released nutrients, with half-lives of only 1 and 3 days, respectively. The N contributions from G. sepium leaves and roots to alley-cropped sweet corn were quantified by the 15 N-dilution technique over three growing seasons. The application of leaves with roots resulted in increased N uptake and dry matter yield in corn. Below-ground competition between hedgerow and corn, assessed using 32 P with the third crop, occurred under conditions of low nutrient-availability. The data imply that there is no advantage of the cut-and-carry system over permanent hedgerows, provided that prunings are applied at the time of nutrient demand in the crop. (author)

  4. Cellulose decomposition and associated nitrogen fixation by mixed cultures of Cellulomonas gelida and Azospirillum species or Bacillus macerans

    Energy Technology Data Exchange (ETDEWEB)

    Halsall, D.M.; Gibson, A.H.

    1985-10-01

    Mixed cultures of Cellulomonas gelida plus Azospirillum lipoferum or Azospirillum brasilense and C. gelida plus Bacillus macerans were shown to degrade cellulose and straw and to utilize the energy-yielding products to fix atmospheric nitrogen. This cooperative process was followed over 30 days in sand-based cultures in which the breakdown of 20% of the cellulose and 28 to 30% of the straw resulted in the fixation of 12 to 14.6 mg of N per g of cellulose and 17 to 19 mg of N per g of straw consumed. Cellulomonas species have certain advantages over aerobic cellulose-degrading fungi in being able to degrade cellulose at oxygen concentrations as low as 1% O/sub 2/ (vol/vol) which would allow a close association between cellulose-degrading and microaerobic diazotrophic microorganisms. Cultures inoculated with initially different proportions of A. brasilense and C. gelida all reached a stable ratio of approximately 1 Azospirillum/3 Cellulomonas cells.

  5. Effect of light on N2 fixation and net nitrogen release of Trichodesmium in a field study

    Science.gov (United States)

    Lu, Yangyang; Wen, Zuozhu; Shi, Dalin; Chen, Mingming; Zhang, Yao; Bonnet, Sophie; Li, Yuhang; Tian, Jiwei; Kao, Shuh-Ji

    2018-01-01

    Dinitrogen fixation (NF) by marine cyanobacteria is an important pathway to replenish the oceanic bioavailable nitrogen inventory. Light is the key to modulating NF; however, field studies investigating the light response curve (NF-I curve) of NF rate and the effect of light on diazotroph-derived nitrogen (DDN) net release are relatively sparse in the literature, hampering prediction using models. A dissolution method was applied using uncontaminated 15N2 gas to examine how the light changes may influence the NF intensity and DDN net release in the oligotrophic ocean. Experiments were conducted at stations with diazotrophs dominated by filamentous cyanobacterium Trichodesmium spp. in the western Pacific and the South China Sea. The effect of light on carbon fixation (CF) was measured in parallel using the 13C tracer method specifically for a station characterized by Trichodesmium bloom. Both NF-I and CF-I curves showed a Ik (light saturation coefficient) range of 193 to 315 µE m-2 s-1, with light saturation at around 400 µE m-2 s-1. The proportion of DDN net release ranged from ˜ 6 to ˜ 50 %, suggesting an increasing trend as the light intensity decreased. At the Trichodesmium bloom station, we found that the CF / NF ratio was light-dependent and the ratio started to increase as light was lower than the carbon compensation point of 200 µE m-2 s-1. Under low-light stress, Trichodesmium physiologically preferred to allocate more energy for CF to alleviate the intensive carbon consumption by respiration; thus, there is a metabolism tradeoff between CF and NF pathways. Results showed that short-term ( energy associated with the variation in light intensity would be helpful for prediction of the global biogeochemical cycle of N by models involving Trichodesmium blooms.

  6. Growth and nitrogen fixation of legumes at increased salinity under field conditions: implications for the use of green manures in saline environments

    NARCIS (Netherlands)

    Bruning, B.; van Logtestijn, R.S.P; Broekman, R.A.; de Vos, A.C.; Parra González, A.; Rozema, J.

    2015-01-01

    The use of legumes as green manure can potentially increase crop productivity in saline environments and thus contribute to the sustainability of agricultural systems. Here, we present results from a field experiment conducted in the Netherlands that addressed the efficiency of nitrogen (N) fixation

  7. Metabolic adaptation, a specialized leaf organ structure and vascular responses to diurnal N2 fixation by nostoc azollae sustain the astonishing productivity of azolla ferns without nitrogen fertilizer

    NARCIS (Netherlands)

    Brouwer, Paul; Bräutigam, Andrea; Buijs, Valerie A.; Tazelaar, Anne O.E.; van der Werf, Adrie; Schlüter, Urte; Reichart, Gert-Jan; Bolger, Anthony; Usadel, Björn; Weber, Andreas P.M.; Schluepmann, Henriette

    2017-01-01

    Sustainable agriculture demands reduced input of man-made nitrogen (N) fertilizer, yet N2 fixation limits the productivity of crops with heterotrophic diazotrophic bacterial symbionts. We investigated floating ferns from the genus Azolla that host phototrophic diazotrophic Nostoc azollae in leaf

  8. New Perspectives on Nitrogen Fixation Measurements Using 15N2 Gas

    Directory of Open Access Journals (Sweden)

    Nicola Wannicke

    2018-04-01

    Full Text Available Recently, the method widely used to determine 15N2 fixation rates in marine and freshwater environments was found to underestimate rates because the dissolution of the added 15N2 gas bubble in seawater takes longer than theoretically calculated. As a solution to the potential underestimate of rate measurements, the usage of the enriched water method was proposed to provide constant 15N2 enrichment. Still, the superiority of enriched water method over the previously used bubble injection remains inconclusive. To clarify this issue, we performed laboratory based experiments and implemented the results into an error analysis of 15N2 fixation rates. Moreover, we conducted a literature search on the comparison of the two methods to calculate a mean effect size using a meta-analysis approach. Our results indicate that the error potentially introduced by an equilibrium phase of the 15N2 gas is −72% at maximum for experiments with very short incubation times of 1 h. In contrast, the underestimation was negligible for incubations lasting 12–24 h (error is −0.2%. Our meta-analysis indicates that 84% of the measurements in the two groups will overlap and there is a 61% chance that a sample picked at random from the enriched water group will have a higher value than one picked at random from the bubble group. Overall, the underestimation of N2 fixation rates when using the bubble method relative to the enriched water method is highly dependent on incubation time and other experimental conditions and cannot be generalized.

  9. Nitrogen fixation in legume trees: Measurement based on 15N techniques

    International Nuclear Information System (INIS)

    Sisworo, E.L.; Rasyid, H.; Sisworo, H.W.; Solahuddin, S.; Wemay, J.

    2000-01-01

    A field experiment has been conducted to measure the N2-fixation in six legume trees, namely Gliricidia sepium(F1), Sesbania sesban(F2), Caliandra tetragona(F3), Flemengia conges-7ta(F4), Acacia mangium(F5), and Leucena leucocephala (F6), using 15N techniques, e.g. the isotope dilution method. For this technique a reference tress, that is a non N2--fixing trees has to be used. In this experiment three reference trees were planted, but only one was used, which above ground growth was equal to the legyme trees. The reference tree chosen was Eucalyptus alba (R1). Data obtained from this experiment show that in general the legume trees have growth then the reference trees expressed, in dray weight of various plant parts and plants and total-N uptake (TN). At harvest some of the legume and reference tree have reached a 2.5 m height. The percentage of N2-fixation(%-fix) ranges from 50-70%. The highest %N-Fix was shown by Leucena leucocephala (F6) (70%N-Fix). High %N-Fix does not necessarily mean hgh N-Fix uptake(gn/tree)too. The N-Fix appears to be determined by the TN (gn/tree). The highest N-Fix was contributed by the leaves, which also has the highest percentage of total -N(%TN) compare to the other plant parts, i.e. roots, stem, and branches

  10. A Medicago truncatula Tobacco Retrotransposon Insertion Mutant Collection with Defects in Nodule Development and Symbiotic Nitrogen Fixation1[W][OA

    Science.gov (United States)

    Pislariu, Catalina I.; D. Murray, Jeremy; Wen, JiangQi; Cosson, Viviane; Muni, RajaSekhara Reddy Duvvuru; Wang, Mingyi; A. Benedito, Vagner; Andriankaja, Andry; Cheng, Xiaofei; Jerez, Ivone Torres; Mondy, Samuel; Zhang, Shulan; Taylor, Mark E.; Tadege, Million; Ratet, Pascal; Mysore, Kirankumar S.; Chen, Rujin; Udvardi, Michael K.

    2012-01-01

    A Tnt1-insertion mutant population of Medicago truncatula ecotype R108 was screened for defects in nodulation and symbiotic nitrogen fixation. Primary screening of 9,300 mutant lines yielded 317 lines with putative defects in nodule development and/or nitrogen fixation. Of these, 230 lines were rescreened, and 156 lines were confirmed with defective symbiotic nitrogen fixation. Mutants were sorted into six distinct phenotypic categories: 72 nonnodulating mutants (Nod−), 51 mutants with totally ineffective nodules (Nod+ Fix−), 17 mutants with partially ineffective nodules (Nod+ Fix+/−), 27 mutants defective in nodule emergence, elongation, and nitrogen fixation (Nod+/− Fix−), one mutant with delayed and reduced nodulation but effective in nitrogen fixation (dNod+/− Fix+), and 11 supernodulating mutants (Nod++Fix+/−). A total of 2,801 flanking sequence tags were generated from the 156 symbiotic mutant lines. Analysis of flanking sequence tags revealed 14 insertion alleles of the following known symbiotic genes: NODULE INCEPTION (NIN), DOESN’T MAKE INFECTIONS3 (DMI3/CCaMK), ERF REQUIRED FOR NODULATION, and SUPERNUMERARY NODULES (SUNN). In parallel, a polymerase chain reaction-based strategy was used to identify Tnt1 insertions in known symbiotic genes, which revealed 25 additional insertion alleles in the following genes: DMI1, DMI2, DMI3, NIN, NODULATION SIGNALING PATHWAY1 (NSP1), NSP2, SUNN, and SICKLE. Thirty-nine Nod− lines were also screened for arbuscular mycorrhizal symbiosis phenotypes, and 30 mutants exhibited defects in arbuscular mycorrhizal symbiosis. Morphological and developmental features of several new symbiotic mutants are reported. The collection of mutants described here is a source of novel alleles of known symbiotic genes and a resource for cloning novel symbiotic genes via Tnt1 tagging. PMID:22679222

  11. A proteomic network for symbiotic nitrogen fixation efficiency in Bradyrhizobium elkanii

    Science.gov (United States)

    Rhizobia bacteroids colonize legumes and reduce N2 to NH3 in root nodules. The current model is that bacteroids avoid assimilating this NH3. Instead, the legume forms glutamine from it, the nitrogen of which is returned to the bacteroid as leucine, isoleucine, valine, dicarboxylates, and peptides. I...

  12. Evaluation of dwarf mutant of cowpea (Vigna Unguiculata L. Walp.) developed through gamma irradiation for nitrogen fixation characters

    International Nuclear Information System (INIS)

    Anjana, G.; Thimmaiah, S.K.

    2002-01-01

    A dwarf mutant developed through gamma-irradiation and mutation breeding of its parent cowpea variety, namely KBC-1 has been characterized for nitrogen-fixation characters such as root nodule acetylene reduction activity (ARA) and legthemoglobin content at different days after sowing (DAS). Significant variations in these characters were noticed among the varieties and for interactions between the varieties and DAS. The ARA was nearly one-and-a half fold higher in the mutant at both 30 (12.69 μmoles)C 2 H 4 formed/h/g fr.wt. of nodules) and 50 DAS (6.74 μmoles) over its parent (9.20 and 4.46 μmoles at 30 and 50 DAS, respectively). Further, the ARA in the mutant decreased linearly with an increase in the DAS. The leghemoglobin (Lb) content was also higher in the mutant over the parent at all the DAS. However, it decreased linearly with an increase in the DAS in both the mutant and the parent. The highest leghemoglobin content was noticed at 30 DAS in both mutant (2.1 mg/g fr. wt. of nodules) and the parent (1.45 mg/g). Thus, the dwarf cowpea mutant was found to be associated with higher nitrogen-fixing ability which could be exploited in future breeding programmes. (author)

  13. Spatially robust estimates of biological nitrogen (N) fixation imply substantial human alteration of the tropical N cycle.

    Science.gov (United States)

    Sullivan, Benjamin W; Smith, W Kolby; Townsend, Alan R; Nasto, Megan K; Reed, Sasha C; Chazdon, Robin L; Cleveland, Cory C

    2014-06-03

    Biological nitrogen fixation (BNF) is the largest natural source of exogenous nitrogen (N) to unmanaged ecosystems and also the primary baseline against which anthropogenic changes to the N cycle are measured. Rates of BNF in tropical rainforest are thought to be among the highest on Earth, but they are notoriously difficult to quantify and are based on little empirical data. We adapted a sampling strategy from community ecology to generate spatial estimates of symbiotic and free-living BNF in secondary and primary forest sites that span a typical range of tropical forest legume abundance. Although total BNF was higher in secondary than primary forest, overall rates were roughly five times lower than previous estimates for the tropical forest biome. We found strong correlations between symbiotic BNF and legume abundance, but we also show that spatially free-living BNF often exceeds symbiotic inputs. Our results suggest that BNF in tropical forest has been overestimated, and our data are consistent with a recent top-down estimate of global BNF that implied but did not measure low tropical BNF rates. Finally, comparing tropical BNF within the historical area of tropical rainforest with current anthropogenic N inputs indicates that humans have already at least doubled reactive N inputs to the tropical forest biome, a far greater change than previously thought. Because N inputs are increasing faster in the tropics than anywhere on Earth, both the proportion and the effects of human N enrichment are likely to grow in the future.

  14. Spatially robust estimates of biological nitrogen (N) fixation imply substantial human alteration of the tropical N cycle

    Science.gov (United States)

    Sullivan, Benjamin W.; Smith, William K.; Townsend, Alan R.; Nasto, Megan K.; Reed, Sasha C.; Chazdon, Robin L.; Cleveland, Cory C.

    2014-01-01

    Biological nitrogen fixation (BNF) is the largest natural source of exogenous nitrogen (N) to unmanaged ecosystems and also the primary baseline against which anthropogenic changes to the N cycle are measured. Rates of BNF in tropical rainforest are thought to be among the highest on Earth, but they are notoriously difficult to quantify and are based on little empirical data. We adapted a sampling strategy from community ecology to generate spatial estimates of symbiotic and free-living BNF in secondary and primary forest sites that span a typical range of tropical forest legume abundance. Although total BNF was higher in secondary than primary forest, overall rates were roughly five times lower than previous estimates for the tropical forest biome. We found strong correlations between symbiotic BNF and legume abundance, but we also show that spatially free-living BNF often exceeds symbiotic inputs. Our results suggest that BNF in tropical forest has been overestimated, and our data are consistent with a recent top-down estimate of global BNF that implied but did not measure low tropical BNF rates. Finally, comparing tropical BNF within the historical area of tropical rainforest with current anthropogenic N inputs indicates that humans have already at least doubled reactive N inputs to the tropical forest biome, a far greater change than previously thought. Because N inputs are increasing faster in the tropics than anywhere on Earth, both the proportion and the effects of human N enrichment are likely to grow in the future.

  15. Facultative anoxygenic photosynthesis in cyanobacteria driven by arsenite and sulfide with evidence for the support of nitrogen fixation

    Science.gov (United States)

    Wolfe-Simon, F.; Hoeft, S. E.; Baesman, S. M.; Oremland, R. S.

    2010-12-01

    The rise in atmospheric oxygen (O2) over geologic time is attributed to the evolution and widespread proliferation of oxygenic photosynthesis in cyanobacteria. However, cyanobacteria maintain a metabolic flexibility that may not always result in O2 release. In the environment, cyanobacteria may use a variety of alternative electron donors rather than water that are known to be used by other anoxygenic phototrophs (eg. purple sulfur bacteria) including reduced forms of sulfur, iron, nitrogen, and arsenic. Recent evidence suggests cyanobacteria actively take advantage of at least a few of these alternatives. We used a classical Winogradsky approach to enrich for cyanobacteria from the high salinity, elevated pH and arsenic-enriched waters of Mono Lake (CA). Experiments, optimized for cyanobacteria, revealed light-dependent, anaerobic arsenite-oxidation in sub-cultured sediment-free enrichments dominated by a filamentous cyanobacteria. We isolated and identified the dominant member of this enrichment to be a member of the Oscillatoriales by 16S rDNA. Addition of 1 mM arsenite induced facultative anoxygenic photosynthesis under continuous and circadian light. This isolate also oxidized sulfide under the same light-based conditions. Aerobic conditions elicited no arsenite oxidation in the light or dark and the isolate grew as a typical cyanobacterium using oxygenic photosynthesis. Under near-infrared light (700 nm) there was a direct correlation of enhanced growth with an increase in the rate arsenite or sulfide oxidation suggesting the use of photosystem I. Additionally, to test the wide-spread nature of this metabolism in the Oscillatoriales, we followed similar arsenite- and sulfide-driven facultative anoxygenic photosynthesis as well as nitrogen fixation (C2H2 reduction) in the axenic isolate Oscillatoria sp. CCMP 1731. Future characterization includes axenic isolation of the Mono Lake Oscillatoria sp. as well as the arsenite oxidase responsible for electron

  16. Characteristics of nitrogen fixation of mixed diazotrophs associated with rice plant

    International Nuclear Information System (INIS)

    Ling Fan; Wang Zhengfang; Wang Yaodong; Song Wei

    1997-01-01

    Characteristics of N 2 fixation of diazotrophs associated with rice plant in paddy soils in Nanjing was studied by 15 N tracing technique. The results showed that amount of N fixed by rice plant was 1.03 kg/666.7 m 2 and the rate of fixed N was 6.7%. The maximum N fixed was occurred during jointing-complete heading stage. The daily average amount of N fixed reached to 24.31 mg/m 2 ·day. The fixed N of jointing-complete heading stage was 40.9% of that whole rice growth stage. The amount of fixed N during jointing-maturing stage was over 70% of whole rice growth stage. The economic benefits for fertilizer saving was 13.3 kg/666.7 m 2 of ammonium sulphate. The yield of rice grain was increased by 4.14% after inoculation with the mixed diazotrophs

  17. Interactions between Nitrogen Fixation and Methane Cycling in Northern Minnesota Peat Bogs

    Science.gov (United States)

    Warren, M. J.; Gaby, J. C.; Lin, X.; Morton, P. L.; Kostka, J. E.; Glass, J. B.

    2014-12-01

    Peatlands cover only 3% of the Earth's surface, yet store a third of soil carbon. Increasing global temperatures have the potential to change peatlands from a net sink to a net source of atmospheric carbon. N is a limiting nutrient in oligotrophic Sphagnum-dominated peatlands and biological N2 fixation likely supplies a significant but unknown fraction of N inputs. Moreover, environmental controls on diazotrophic community composition in N-limited peatlands are poorly constrained. Thus, improved understanding of feedbacks between the CH4 and N cycles is critical for predicting future changes to CH4 flux from peat bogs. We coupled measurements of N2 fixation activity measured by the acetylene (C2H2) reduction assay (ARA) with molecular analyses of expression and diversity of nifH genes encoding the molybdenum (Mo)-containing nitrogenase from two peat bogs in the Marcell Experimental Forest, Minnesota, USA. The top 10 cm of peat was sampled from the high CH4 flux S1 bog and the low CH4 flux Zim bog in April and June 2014. Despite similar N concentrations in the top 10 cm of both bogs (0.5-1.0 μM NO2-+NO3- and 2-3 μM NH4+), the S1 bog displayed variable ARA activity (1-100 nmol C2H4 h-1 g-1) whereas the Zim bog had consistently low ARA activity (Methylocella was the dominant diazotroph in the S1 bog based on high throughput next generation sequencing of nifH cDNA amplicons. Given previous reports of C2H2 inhibition of methanotrophy, we measured CH4 consumption in the presence or absence of 1% C2H2. Preliminary results suggest minimal effect of C2H2 on CH4 oxidation. Future measurements of 15N2 incorporation coupled to molecular analysis will elucidate whether methanotroph diazotrophy was suppressed by C2H2 in ARA incubations.

  18. Effects of sulfur dioxide on nitrogen fixation, carbon partitioning, and yield components in snapbean

    International Nuclear Information System (INIS)

    Griffith, S.M.; Campbell, W.F.

    1987-01-01

    The air pollutant SO 2 is known to affect plant biochemistry and physiology, although very little is known about its effects on N 2 -fixation in legumes. This study sought to determine if N 2 -fixation, C partitioning, and plant productivity of snapbean (Phaseolus vulgaris L.) were affected under short-term, low-level SO 2 exposures. Plants were exposed, 29 d after planting (7 d before anthesis), to 0, 18, and 36 μmol SO 2 m -3 for 4 h d -1 for 5 d in a fumigation chamber. On the last day of SO 2 treatment, plants were also exposed to 14 CO 2 to determine changes in C partitioning patterns. At these concentrations, there was no visible damage to plant tissue and no significant changes in dry weight or yield components. Only the 36 μmol SO 2 m -3 treatment reduced C 2 H 2 reduction rates, but recovery to near control rates occurred within 24 h after SO 2 removal. Leaves of plants treated with 18 μmol SO 2 m -3 exported more of their total assimilated 14 C than control plants, while those treated with 36 μmol SO 2 m -3 retained greater amounts. Retention of 14 C at the 36 μmol SO 2 m -3 level may account for the inhibition of C 2 H 2 -reduction because of less photosynthate arriving at the root nodules. These data suggest that SO 2 levels that do not cause visible injury may interfere with C metabolism and transport in snapbean

  19. Project in determination of crystal structure of nitrogen fixation proteins from azospirilum brasiliense and herbaspirilum seropedicae by synchrotron x-ray diffraction

    International Nuclear Information System (INIS)

    Barbosa, Valma M.; Leggs, Luciana A.; Delboni, Luis F.; Chubatsu, LedaS.; Souza, Emanuel M.; Machado, Hidevaldo B.; Yates, Geoffrey M.; Pedrosa, Fabio O.

    1996-01-01

    Full text. Biological nitrogen fixation is essential for maintaining the nitrogen cycle on earth and of high importance for Brazilian agriculture. The nitrogenase enzyme system, which provides the biochemical machinery for nitrogen fixation, consists of two component metalloproteins, the molybdenumiron (Mo Fe) protein and the iron (Fe) protein. Nitrogen fixation is a very energy-intensive process, requiring around 16 moles of ATP for each mol of N 2 fixed (reduced). As a consequence, synthesis and activity of nitrogenase is tighty regulated at two levels: general and specific. The general level regulation is mediated by the ntr (nitrogen regulation) system. Two gene products are involved: the ntrB gene product (NtrB) is responsible for the activation of the ntrC gene product (NtrC) by phosphorylating a conserved Asp54, which activates the expression of the nifA gene. The nif specific control system is mediated by the NifA protein, which binds to a DNA specific sequence (UAS, Upstream Activator Sequence) and activates nif promoter transcriptions by RNA polymerase- α54 , following ATP hydrolysis. The aim of this project is to solve the crystal structure of dinitrogenase reductase (iron protein) and dinitrogenase (molybdenum-iron protein) from Azospirilim brasiliense and the regulatory proteins NifA from Herbaspirillum seropedicae and NtrC Azospirillum brasiliense. The three dimensional structure of the proteins involved in this project will allow a better understanding of the mechanism of biological nitrogen fixation. To this end, the data collection will probably be done at the LNLS facilities which will be available in the near future. (author)

  20. Project in determination of crystal structure of nitrogen fixation proteins from azospirilum brasiliense and herbaspirilum seropedicae by synchrotron x-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Barbosa, Valma M.; Leggs, Luciana A.; Delboni, Luis F.; Chubatsu, LedaS.; Souza, Emanuel M.; Machado, Hidevaldo B.; Yates, Geoffrey M.; Pedrosa, Fabio O. [Parana Univ., Curitiba, PR (Brazil). Dept. de Bioquimica

    1996-12-31

    Full text. Biological nitrogen fixation is essential for maintaining the nitrogen cycle on earth and of high importance for Brazilian agriculture. The nitrogenase enzyme system, which provides the biochemical machinery for nitrogen fixation, consists of two component metalloproteins, the molybdenumiron (Mo Fe) protein and the iron (Fe) protein. Nitrogen fixation is a very energy-intensive process, requiring around 16 moles of ATP for each mol of N{sub 2} fixed (reduced). As a consequence, synthesis and activity of nitrogenase is tighty regulated at two levels: general and specific. The general level regulation is mediated by the ntr (nitrogen regulation) system. Two gene products are involved: the ntrB gene product (NtrB) is responsible for the activation of the ntrC gene product (NtrC) by phosphorylating a conserved Asp54, which activates the expression of the nifA gene. The nif specific control system is mediated by the NifA protein, which binds to a DNA specific sequence (UAS, Upstream Activator Sequence) and activates nif promoter transcriptions by RNA polymerase-{sup {alpha}54}, following ATP hydrolysis. The aim of this project is to solve the crystal structure of dinitrogenase reductase (iron protein) and dinitrogenase (molybdenum-iron protein) from Azospirilim brasiliense and the regulatory proteins NifA from Herbaspirillum seropedicae and NtrC Azospirillum brasiliense. The three dimensional structure of the proteins involved in this project will allow a better understanding of the mechanism of biological nitrogen fixation. To this end, the data collection will probably be done at the LNLS facilities which will be available in the near future. (author)

  1. Metabolic features involved in drought stress tolerance mechanisms in peanut nodules and their contribution to biological nitrogen fixation.

    Science.gov (United States)

    Furlan, Ana Laura; Bianucci, Eliana; Castro, Stella; Dietz, Karl-Josef

    2017-10-01

    Legumes belong to the most important crops worldwide. They increase soil fertility due their ability to establish symbiotic associations with soil microorganisms, known as rhizobia, capable of fixing nitrogen from the atmosphere. However, they are frequently exposed to abiotic stress conditions in particular drought. Such adverse conditions impair the biological nitrogen fixation (BNF) and depend largely on the legume. Therefore, two peanut cultivars with contrasting tolerance to drought, namely the more tolerant EC-98 and the sensitive Granoleico, were investigated to elucidate the relative contribution of BNF to the tolerance to drought. The tolerant cultivar EC-98 sustained growth and BNF similar to the control condition despite the reduced water potential and photosynthesis, suggesting the functioning of distinct metabolic pathways that contributed to enhance the tolerance. The biochemical and metabolomics approaches revealed that nodules from the tolerant cultivar accumulated trehalose, proline and gamma-aminobutyric acid (GABA), metabolites with known function in protecting against drought stress. The amide metabolism was severely affected in nodules from the sensitive cultivar Granoleico as revealed by the low content of asparagine and glutamine in the drought stressed plants. The sensitive cultivar upon rehydration was unable to re-establish a metabolism similar to well-watered plants. This was evidenced by the low level of metabolites and, transcripts and specific activities of enzymes from the carbon (sucrose synthase) and nitrogen (glutamine synthetase) metabolism which decreased below the values of control plants. Therefore, the increased content of metabolites with protective functions under drought stress likely is crucial for the full restoration upon rehydration. Smaller changes of drought stress-related metabolites in nodule are another trait that contributes to the effective control of BNF in the tolerant peanut cultivar (EC-98). Copyright © 2017

  2. Trends in nitrogen isotope ratios of juvenile winter flounder reflect changing nitrogen inputs to Rhode Island, USA estuarine systems.

    Science.gov (United States)

    Pruell, Richard J; Taplin, Bryan K; Miller, Kenneth M

    2017-05-15

    Nitrogen isotope ratios (δ 15 N) in juvenile winter flounder, Pseudopleuronectes americanus, were used to examine changes in nitrogen inputs to several Rhode Island, USA estuarine systems. Fish were collected over two three-year periods with a ten-year interval between sampling periods (2002-2004 and 2012-2014). During that interval numerous changes to nutrient management practices were initiated in the watersheds of these estuarine systems including the upgrade of several major wastewater treatment facilities that discharge to Narragansett Bay, which significantly reduced nitrogen inputs. Following these reductions, the δ 15 N values of flounder in several of the systems decreased as expected; however, isotope ratios in fish from upper Narragansett Bay significantly increased. We believe that low δ 15 N values measured in 2002-2004 were related to concentration-dependent fractionation at this location. Increased δ 15 N values measured between 2012 and 2014 may indicate reduced fractionation or that changes in wastewater treatment processes altered the nitrogen isotopic ratios of the effluents. Published by Elsevier Ltd.

  3. Nitrogen Fixation by Photochemistry in the Atmosphere of Titan and Implications for Prebiotic Chemistry

    Science.gov (United States)

    Balucani, Nadia

    The observation of N-containing organic molecules and the composition of the haze aerosols, as determined by the Aerosol Collector and Pyrolyser (ACP) on-board Huygens, are clear indications that some chemistry involving nitrogen active forms and hydrocarbons is operative in the upper atmosphere of Titan. Neutral-neutral reactions involving the first electronically excited state of atomic nitrogen, N(2D), and small hydrocarbons have the right prerequisites to be among the most significant pathways to formation of nitriles, imines and other simple N-containing organic molecules. The closed-shell products methanimine, ethanimine, ketenimine, 2H-azirine and the radical products CH3N, HCCN and CH2NCH can be the intermediate molecular species that, via addition reactions, polymerization and copolymerization form the N-rich organic aerosols of Titan as well as tholins in bulk reactors simulating Titan's atmosphere.

  4. Arbuscular Mycorrhiza Stimulates Biological Nitrogen Fixation in Two Medicago spp. through Improved Phosphorus Acquisition

    Czech Academy of Sciences Publication Activity Database

    Püschel, David; Janoušková, M.; Voříšková, A.; Gryndlerová, Hana; Vosátka, M.; Jansa, Jan

    2017-01-01

    Roč. 8, MAR 27 (2017), s. 1-12, č. článku 390. ISSN 1664-462X R&D Projects: GA ČR GA15-05466S; GA MŠk(CZ) LK11224 Institutional support: RVO:61388971 Keywords : arbuscular mycorrhiza * nitrogen acquisition * phosphorus uptake Subject RIV: EE - Microbiology, Virology OBOR OECD: Microbiology Impact factor: 4.298, year: 2016

  5. Phosphorus Use Efficiency for Symbiotic Fixation Nitrogen in Voandzou (Vigna Subterranea) Using Isotopic Exchange Method in Rhizotron

    Energy Technology Data Exchange (ETDEWEB)

    Andriamananjara, A.; Rabeharisoa, L. [Laboratoire des Radio-isotopes, Universite d' Antananarivo, Antananarivo (Madagascar); Masse, D. [Institut de Recherche pour le Developpement, UMR Eco and Sols, Montpellier, (France); Amenc, L.; Pernot, C.; Drevon, J. J. [Institut National de la Recherche Agronomique, UMR Eco and Sols, Montpellier, (France); Morel, C. [INRA-ENITA, Villenave d' Ornon (France)

    2013-11-15

    Low bioavailability of nitrogen and phosphorus is one of the main constraints in the acid soils with high P-fixing capacity. Plants adapt to low nutrient availability through various biological and physico-chemical mechanisms. Since genetic variation of N{sub 2} fixation exists in numerous legume species, optimization of symbiotic nitrogen fixation (SNF) under P deficiency could be a way to the replenishment of soil fertility in tropical soils. As the genetic potential of crops like Vigna subterranea (Bambara groundnut or voandzou) is little studied, although its agronomic potential is interesting for the farmers of Africa, a physiological study through legume screening for N{sub 2} fixation was performed with 54 cultivars from Madagascar, Niger and Mali, inoculated with the reference strain of Bradyrhizobium sp. Vigna CB756 in hydroponic culture under P deficiency and sufficiency (30 and 75 {mu}mol KH{sub 2}PO{sub 4} plant{sup -1} week {sup -1}, respectively), corresponding respectively to 28 and 70 mg P kg{sup -1} of soil. Large variability of nodulation and plant biomass was found among cultivars. These two parameters were generally correlated and the slope of the plant biomass regression as a function of nodulation was considered as an indicator of the efficiency in use of the rhizobial symbiosis. For the two cultivars most tolerant to P deficiency, V1 and V4 from Madagascar, the increase in use efficiency of the rhizobial symbiosis under P deficiency was linked with an increase in nodulated root O{sub 2} consumption linked to N{sub 2} fixation, and in phytase gene expression observed on the nodule sections by in situ RT- PCR. As the complexity of P compartments makes it difficult to assess the P bioavailability in the plant rhizosphere, an isotopic {sup 32}P exchange method was carried out in a rhizotron in order to assess the direct effect of the roots on P mobilization in rhizosphere soil, comparing V1 and V4 with 28 or 70 mg P kg{sup -1} of soil. Throughout

  6. Nitrogen fixation in Leucaena leucocephala and effects of pruning s on cereal yields

    International Nuclear Information System (INIS)

    Bekunda, M.

    1998-01-01

    Leucaena leucocephala was interplanted with reference tree species, Cassia siamea and Cassia spectabilis, and estimates of percent N derived from N 2 fixation (%Ndfa) were made, by the isotope-dilution method, at 4, 6, 14, 20 and 30 months after transplanting. The %Ndfa values were low and variable throughout the growth period, except after thinning at 14 months when there was a five-fold increase. The two non-fixing reference species outperformed the N 2 -fixing Leucaena in above-ground vegetative production, and provided different fixed-N estimates. Prunings from the L. leucocephala and C. Siamea trees were applied separately to soil as green manure. Maize was planted to test the effects of the Leucaena green manure on soil fertility, and millet was the test crop for the Cassia. Whether surface-applied or incorporated, the prunings significantly improved yields, which were generally similar among rates and methods of application. The proportions of cereal N obtained from prunings ranged from 8 to 33%, with no cereal-yield correlation. The data indicate that multipurpose tree prunings are of potential use to farmers as organic sources of nutrients, even at relatively low application rates, without need for incorporation into the soil. (author)

  7. Effect of organic fertiliser residues from rice production on nitrogen fixation of soya (Glycine max L. Merrill, Chiang Mai 60 variety

    Directory of Open Access Journals (Sweden)

    Nattida Luangmaka

    2013-09-01

    Full Text Available A field study was undertaken on the residual effect of organic fertilisers applied to the preceding rice cropping on nitrogen fixation of soya in a rice-soya cropping system. The experiment was conducted on a farmer’s lowland paddy in Mae Rim district, Chiang Mai province, Thailand. Organic fertiliser treatments assigned were: 1 control (no fertiliser, 2 animal manure of cattle (AM, 3 compost (CP, 4 azolla (AZ, 5 AM + CP, 6 AM + AZ, 7 CP + AZ and 8 AM + CP + AZ. Soya seeds were planted without rhizobial inoculation in December 2011, four months after the application of organic fertilisers. Nodule weight, total shoot nitrogen accumulation and relative ureide index at various growth stages were recorded as the indices of nitrogen fixation. Results of the study demonstrate that the residues from the application the organic fertilisers of narrow C/N ratios during the land preparation for rice cropping four months before soya cultivation promoted nitrogen fixation by native rhizobia.

  8. Response of fodder legumes berseem (trifolium alexandrinum, L) shaftal (trifolium resupinatum L) and lucerne (medicago sative, L) to sulphur fertilization for nodulatin, forage yield and nitrogen fixation

    International Nuclear Information System (INIS)

    Idris, M.; Zeb, A.; Iqbal, M.M.

    2001-01-01

    The effect of sulphur fertilization (10, 20 mg/kg soil) applied as ground elemental sulphur (98% S) on the forage yield and biological nitrogen fixation of three fodder legumes (Lucerne, Shaftal and Berseem) was studied under pot culture condition. Basal dozes of nitrogen (N), phosphorus (P/sub 2/O/sub 5) and potash (K/sub 2/O) at 10, 40, 20 mg /kg soil were applied to each pot. The result revealed that the application of sulphur did not cause any significant improvement in the nontidal response of Lucerne, Shaftal and berseem. Dry matter yield of forage in four cuts, however was improved significantly in the range of 16.0 to 57.0% for Lucerne, 9.0 to 53.0% for shaftal and 15.0 to 81.0% for berseem by sulphur fertilizations. Biological nitrogen fixation in shoots as revealed by shoot N yield difference exhibited a significant increase by 20.0 to 62.0% for Lucerne, 13.0 to 59.0% for shaftal and 25.0 to 89.0% for berseem in 4 cuts, while in roots biological nitrogen fixation exhibited a significant increase by 5.0 to 25.0% for Lucerne, 11.0 to 41.0 percent for shaftal and 21.0 to 38.0 percent for berseem as result of sulphur fertilization. (author)

  9. Nitrogen-Dependent Carbon Fixation by Picoplankton In Culture and in the Mississippi River

    Energy Technology Data Exchange (ETDEWEB)

    Aubrey Smith; Marguerite W. Coomes; Thomas E. Smith

    2005-04-30

    The pepc gene, which encodes phosphoenolpyruvate carboxylase (PEPC), of the marine cyanobacterium Synechococcus PCC 7002, was isolated and sequenced. PEPC is an anaplerotic enzyme, but it may also contribute to overall CO2 fixation through β-carboxylation reactions. A consensus sequence generated by aligning the pepc genes of Anabaena variabilis, Anacystis nidulans and Synechocystis PCC 6803 was used to design two sets of primers that were used to amplify segments of Synechococcus PCC 7002 pepc. In order to isolate the gene, the sequence of the PCR product was used to search for the pepc nucleotide sequence from the publicly available genome of Synechococcus PCC 7002. At the time, the genome for this organism had not been completed although sequences of a significant number of its fragments are available in public databases. Thus, the major challenge was to find the pepc gene among those fragments and to complete gaps as necessary. Even though the search did not yield the complete gene, PCR primers were designed to amplify a DNA fragment using a high fidelity thermostable DNA polymerase. An open reading frame (ORF) consisting of 2988 base pairs coding for 995 amino acids was found in the 3066 bp PCR product. The pepc gene had a GC content of 52% and the deduced protein had a calculated molecular mass of 114,049 Da. The amino acid sequence was closely related to that of PEPC from other cyanobacteria, exhibiting 59-61% identity. The sequence differed significantly from plant and E. coli PEPC with only 30% homology. However, comparing the Synechococcus PCC 7002 sequence to the recently resolved E. coli PEPC revealed that most of the essential domains and amino acids involved in PEPC activity were shared by both proteins. The recombinant Synechococcus PCC 7002 PEPC was expressed in E. coli.

  10. Biological Nitrogen Fixation Efficiency in Brazilian Common Bean Genotypes as Measured by {sup 15}N Methodology

    Energy Technology Data Exchange (ETDEWEB)

    Franzini, V. I.; Mendes, F. L. [Brazilian Agricultural Research Corporation, EMBRAPA-Amazonia Oriental, Belem, PA (Brazil); Muraoka, T.; Trevisam, A. R. [Center for Nuclear Energy in Agriculture, University of Sao Paulo, Piracicaba, SP (Brazil); Adu-Gyamfi, J. J. [Soil and Water Management and Crop Nutrition Laboratory, International Atomic Energy Agency, Seibersdorf (Austria)

    2013-11-15

    Common bean (Phaseolus vulgaris L.) represents the main source of protein for the Brazilian and other Latin-American populations. Unlike soybean, which is very efficient in fixing atmospheric N{sub 2} symbiotically, common bean does not dispense with the need for N fertilizer application, as the biologically fixed N (BNF) seems incapable to supplement the total N required by the crop. A experiment under controlled conditions was conducted in Piracicaba, Brazil, to assess N{sub 2} fixation of 25 genotypes of common bean (Phaseolus vulgaris L.). BNF was measured by {sup 15}N isotope dilution using a non-N{sub 2} fixing bean genotype as a reference crop. The common bean genotypes were grown in low (2.2 mg N kg{sup -1} soil) or high N content soil (200 mg N kg{sup -1} soil), through N fertilizer application, as urea-{sup 15}N (31.20 and 1.4 atom % {sup 15}N, respectively). The bean seeds were inoculated with Rhizobium tropici CIAT 899 strain and the plants were harvested at grain maturity stage. The contribution of BNF was on average 75% of total plant N content, and there were differences in N fixing capacity among the bean genotypes. The most efficient genotypes were Horizonte, Roxo 90, Grafite, Apore and Vereda, when grown in high N soil. None of the genotypes grown in low N soil was efficient in producing grains compared to those grown in high N soil, and therefore the BNF was not able to supply the total N demand of the bean crop. (author)

  11. Pleiotropic effect of his gene mutations on nitrogen fixation in Klebsiella pneumoniae

    DEFF Research Database (Denmark)

    Jensen, Jens Stougaard; Kennedy, C

    1982-01-01

    retained a Nif plate phenotype. A hisA mutation had a similar but more dramatic effect. At low concentrations of histidine the hisA mutant strain had only 5% of the nitrogenase activity found at high histidine concentration or in a his strain, and was also Nif on low histidine agar plates. Addition...... of adenine restored nitrogenase activity in the hisA but not the hisB, hisC, or hisD mutants. Low levels of intracellular ATP, a consequence of hisG enzyme activity, correlated with loss of nitrogen-fixing ability in the hisA mutant which failed to sustain nif gene expression under these conditions....... Synthesis of other major cell proteins was relatively unaffected indicating that nif gene expression is selectively regulated by the energy status of the organism....

  12. Successful correction of tibial bone deformity through multiple surgical procedures, liquid nitrogen-pretreated bone tumor autograft, three-dimensional external fixation, and internal fixation in a patient with primary osteosarcoma: a case report.

    Science.gov (United States)

    Takeuchi, Akihiko; Yamamoto, Norio; Shirai, Toshiharu; Nishida, Hideji; Hayashi, Katsuhiro; Watanabe, Koji; Miwa, Shinji; Tsuchiya, Hiroyuki

    2015-12-07

    In a previous report, we described a method of reconstruction using tumor-bearing autograft treated by liquid nitrogen for malignant bone tumor. Here we present the first case of bone deformity correction following a tumor-bearing frozen autograft via three-dimensional computerized reconstruction after multiple surgeries. A 16-year-old female student presented with pain in the left lower leg and was diagnosed with a low-grade central tibial osteosarcoma. Surgical bone reconstruction was performed using a tumor-bearing frozen autograft. Bone union was achieved at 7 months after the first surgical procedure. However, local tumor recurrence and lung metastases occurred 2 years later, at which time a second surgical procedure was performed. Five years later, the patient developed a 19° varus deformity and underwent a third surgical procedure, during which an osteotomy was performed using the Taylor Spatial Frame three-dimensional external fixation technique. A fourth corrective surgical procedure was performed in which internal fixation was achieved with a locking plate. Two years later, and 10 years after the initial diagnosis of tibial osteosarcoma, the bone deformity was completely corrected, and the patient's limb function was good. We present the first report in which a bone deformity due to a primary osteosarcoma was corrected using a tumor-bearing frozen autograft, followed by multiple corrective surgical procedures that included osteotomy, three-dimensional external fixation, and internal fixation.

  13. Radiation application for upgrading of bioresources - Development of antifungal and-or nitrogen fixative microbes

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki Sung; Kim, Soo Ki; Lee, Sung Ho; Lee, Jung Suk [Paichai University, Taejon (Korea)

    1999-04-01

    (1) In this study, the antifungal bacterial eight strains were isolated from various environment located in Chung-cheong area, Korea. These isolates were identified the genera Bacillus sp, Pseudomonas sp. through morphological, physiological and biochemical analysis. Especially, strain KL2143, 2367 were identified as Bacillus subtilis (KL2143/KL2367) and strain KL2326, KL2314 identified as Pseudomonas aurantiaca have never been reported internationally. Considering antifungal(AF) spectrum of strain KL2143 show the broad range of AF activity on a number of pathogenic fungi. Therefore, strain KL2143 was selected with the strong candidate of antifungal bacteria on every purpose and usage related with our research goal. (2) Optimal conditions for the production of antifungal material were analyzed under various environmental conditions (carbon source, nitrogen source, phosphate concentration, pH, temperature, amino acids, vitamins). Growth rates were different according to carbon and nitrogen source, antifungal material production yield were not different, however. Product of antifungal material according to phosphate is proportional to concentration; the higher in high concentration and the low in lower concentration. And productivity of antifungal material is was generally high in the range 30 - 37 deg C at pH7 and in case of adding vitamin B12, lysine and aginine to medium it was enhanced. (3) Moreover, bio-degradability upon agricultural substance and organic substances by AF bacteria was strikingly effective. (4) AF stains were screened and selected from this research can be used in the microbial biocides as well as multifunctional bio-controllers in order to remove plant pathogenic fungi and to clarify the polluted environment. Due to their excellent degradation capability for agricultural and/or organic substances, they also can be used to improve soil quality, to ferment compost and to clean up the environment. (5) Establishment of a new technology for the

  14. The Mekong River plume fuels nitrogen fixation and determines phytoplankton species distribution in the South China Sea during low- and high-discharge season

    DEFF Research Database (Denmark)

    Grosse, Julia; Bombar, Deniz; Doan, Hai Nhu

    2010-01-01

    ) for the adjacent sea and creates different salinity and nutrient gradients over different seasons. River water (salinity 0), mesohaline waters (salinity 14-32), a transition zone with salinities between 32 and 33.5, and marine waters (salinity above 33.5) were sampled at different spatial resolutions in both......The influence of the Mekong River (South China Sea) on N2 fixation and phytoplankton distribution was investigated during the lowest- and highest-discharge seasons (April 2007 and September 2008, respectively). The river plays an essential role in providing nutrients (nitrate, phosphate, silicate...... cruises. High N2 fixation rates were measured during both seasons, with rates of up to 5.05 nmol N L-1 h -1 in surface waters under nitrogen-replete conditions, increasing to 22.77 nmol N L-1 h-1 in nitrogen-limited waters. Asymbiotic diatoms were found only close to the river mouth, and symbiotic diatoms...

  15. Soil microbial population and nitrogen fixation in peanut under fly ash and sewage sludge

    International Nuclear Information System (INIS)

    Sarkar, S.; Khan, A.R.

    2002-06-01

    such as C, N, S, and P in the biosphere (Wong and Wong, 1986). Addition of such wastes to agricultural lands is likely to alter the nutrient cycling processes particularly for leguminous crops, where nodulation, N 2 fixation and N uptake is mainly governed by a group of microorganisms (McGrath et al., 1988). It is therefore imperative to study the effect of different doses and combination of wastes on changes in microbial population and its impact on overall performance of a crop. The objective of this study is thus, to investigate the implications of industrial wastes (Fly Ash) and urban sewage sludge (treated City Waste) application at different rates and frequencies of application on the total soil microbial population, Rhizobium population, nodulation, N-uptake, N-accumulation and yield of peanut crop in lateritic sandy loam soil of eastern India

  16. Comparative Analysis of the Combined Effects of Different Water and Phosphate Levels on Growth and Biological Nitrogen Fixation of Nine Cowpea Varieties

    OpenAIRE

    Jemo, Martin; Sulieman, Saad; Bekkaoui, Faouzi; Olomide, Oluwatosin A. K.; Hashem, Abeer; Abd_Allah, Elsayed Fathi; Alqarawi, Abdulaziz A.; Tran, Lam-Son Phan

    2017-01-01

    Water deficit and phosphate (Pi) deficiency adversely affect growth and biological nitrogen fixation (BNF) of legume crops. In this study, we examined the impact of interaction between soil water conditions and available soil-Pi levels on growth, nodule development and BNF potential of nine cowpea varieties grown on dry savanna soils. In our experimental design, soils with different available soil-Pi levels, i.e., low, moderate, and high soil-Pi levels, collected from various farming fields w...

  17. The use of nuclear techniques in the management of nitrogen fixation by trees to enhance fertility of fragile tropical soils. Results of a co-ordinated research project

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-11-01

    The Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture initiated in 1990 a Co-ordinated Research Project on The Use of Nuclear or Related Techniques in Management of Nitrogen Fixation by Trees for Enhancing Soil Fertility and Soil Conservation in Fragile Tropical Soils. This document contains nine papers referring to the results of the project. A separate abstract was prepared for each paper Refs, figs, tabs

  18. The use of nuclear techniques in the management of nitrogen fixation by trees to enhance fertility of fragile tropical soils. Results of a co-ordinated research project

    International Nuclear Information System (INIS)

    1998-11-01

    The Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture initiated in 1990 a Co-ordinated Research Project on The Use of Nuclear or Related Techniques in Management of Nitrogen Fixation by Trees for Enhancing Soil Fertility and Soil Conservation in Fragile Tropical Soils. This document contains nine papers referring to the results of the project. A separate abstract was prepared for each paper

  19. Improving yield and nitrogen fixation of grain legumes in the tropics and sub-tropics of Asia. Results of a co-ordinated research programme

    International Nuclear Information System (INIS)

    1998-07-01

    The Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture initiated a Co-ordinated Research Project on The Use of Isotopes in Studies to Improve Yield and N 2 Fixation of Grain Legumes with the Aim of Increasing Food Production and Saving N-fertilizer in the Tropics and Sub-Tropics of Asia that was operational from 1990 to 1995. This Project was underpinned by extensive experience in the use of 15 N-labelled fertilizer in quantifying N 2 fixation by food and pasture legumes; the isotope-dilution technique, recognized as the most accurate mode of quantifying fixation, was developed at the IAEA and has been used profitably for over 20 years in co-ordinated research projects that were focused on aspects relevant to the sustainability of agriculture in developing countries in which food security is most under threat. This effort to improve N 2 fixation by food legumes in Asia, and in so doing to increase productivity of cereal-based farming systems as a whole, was timely in terms of regional needs. It was complemented by an overlapping Co-ordinated Research Project entitled ''The Use of Nuclear and Related Techniques in Management of Nitrogen Fixation by trees for Enhancing Soil Fertility and Soil Conservation in Fragile Tropical Soils''. The project involved scientists from Australia, Bangladesh, China, India, Malaysia, Pakistan the Philippines, Sri Lanka, Thailand and Viet Nam

  20. Available nitrogen: A time-based study of manipulated resource islands

    Science.gov (United States)

    Stubbs, Michelle M.; Pyke, David A.

    2005-01-01

    Spatial and temporal heterogeneity of available nitrogen are critical determinants of the distribution and abundance of plants and animals in ecosystems. Evidence for the resource island theory suggests that soils below tree and shrub canopies contain higher amounts of resources, including available nitrogen, than are present in interspace areas. Disturbances, such as prescribed fire and tree removal, are common management practices in shrub-woodland ecosystems, but it is not known if these practices affect resource islands. We examined temporal variation in resource islands of available nitrogen and their retention after fire and woody plant removal. From August 1997 to October 1998, soil nitrate (NO3−) and ammonium (NH4+) were measured monthly from canopy and interspace plots within four juniper-sagebrush sites along a precipitation gradient in central Oregon, USA. At each site, soil samples were collected from untreated plots, plots in which woody plants were removed, and those treated with prescribed fire in fall 1997. In burned treatments, canopy concentrations were significantly higher than interspace concentrations throughout the measurement period. Canopy NO3− and NH4+ concentrations were significantly higher on burned vs. unburned treatments for four months after fire. After woody plant removal, NO3− and NH4+ concentrations did not differ from the controls. Untreated control areas had higher NO3− and NH4+ concentrations under juniper canopies for nearly all months. Wetter sites had smaller differences between canopy and interspace concentrations through time than did the two drier sites. In relation to NO3− and NH4+ in this ecosystem, resource islands appear to be more ephemeral in wetter sites, and more pronounced following fire disturbances than in controls or those treated by woody plant removal.

  1. Stable symbiotic nitrogen fixation under water-deficit field conditions by a stress-tolerant alfalfa microsymbiont and its complete genome sequence.

    Science.gov (United States)

    Jozefkowicz, Cintia; Brambilla, Silvina; Frare, Romina; Stritzler, Margarita; Piccinetti, Carlos; Puente, Mariana; Berini, Carolina Andrea; Pérez, Pedro Reyes; Soto, Gabriela; Ayub, Nicolás

    2017-12-10

    We here characterized the stress-tolerant alfalfa microsymbiont Sinorhizobium meliloti B401. B401-treated plants showed high nitrogen fixation rates under humid and semiarid environments. The production of glycine betaine in isolated bacteroids positively correlated with low precipitation levels, suggesting that this compound acts as a critical osmoprotectant under field conditions. Genome analysis revealed that strain B401 contains alternative pathways for the biosynthesis and uptake of glycine betaine and its precursors. Such genomic information will offer substantial insight into the environmental physiology of this biotechnologically valuable nitrogen-fixing bacterium. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Symbiotic N fixation and fertilizer nitrogen use efficiency in legume-cereal intercropping systems

    International Nuclear Information System (INIS)

    Jena, D.; Misra, C.

    1990-01-01

    On a lateritic soil at Bhubaneswar short duration rice, finger millet, maize, groundnut, pigeon pea, black gram were grown alone or as intercrop in microplots (1mx1m). Thirty days after germination, 15 N tagged urea (3% a.e.) solutions was applied to all the treatments so as to provide 40 kg N ha -1 for the cereals, 10 kg n ha -1 for the legumes and 20 kg N ha -1 for cereal plus legumes. The results show the fertilizer efficiency values to be nearly 62 to 69 per cent for rice, 53 per cent for maize and 22 percent for finger millet. These values were 12 to 17 per cent for pigeon pea, 18 percent for black gram and 23 percent for groundnut. Averaged over the cropping system and fertilizer doses, the nitrogen fixed by legumes, viz,pigeon-pea, black gram and groundnut were 16.3, 15.5 and 17.5 kg ha -1 , respectively, within 60 days of crop growth. Horse gram grown as a sequence crop during the dry season (after the harvest of wet season crops) using the residual soil water and nutrients appears to utilize the residual 15 N better when it follows the non-legumes compared with that when it follows the legumes. (author). 5 refs., 5 tabs

  3. Interactions between nitrogen fixation and osmoregulation in the methanogenic archaeon Methanosarcina barkeri 227

    Energy Technology Data Exchange (ETDEWEB)

    Brabban, A.D.; Orcutt, E.N.; Zinder, S.H. [Cornell Univ., Ithaca, NY (United States). Section of Microbiology

    1999-03-01

    The nitrogenase enzyme complex of Methanosarcina barkeri 227 was found to be more sensitive to NaCl than previously studied molybdenum nitrogenases are, with total inhibition of activity occurring at 190 mM NaCl, compared with >600 mM NaCl for Azotobacter vinelandii and Clostridium pasteurianum nitrogenases. Na{sup +} and K{sup +} had equivalent effects, whereas Mg{sup 2+} was more inhibitory than either monovalent cation, even on a per-charge basis. The anion Cl{sup {minus}} was more inhibitory than acetate was. Because M. barkeri 227 is a facultative halophile, the authors examined the effects of external salt on growth and diazotrophy and found that inhibition of growth was not greater with N{sub 2} than with NH{sub 4}{sup +}. Cells grown with N{sub 2} and cells grown with NH{sub 4}{sup +} produced equal concentrations of {alpha}-glutamate at low salt concentrations and equal concentrations of N{sup {var_epsilon}}-acetyl-{beta}-lysine at NaCl concentrations greater than 500 mM. Despite the high energetic cost of fixing nitrogen for these osmolytes, the authors obtained no evidence that there is a shift towards nonnitrogenous osmolytes during diazotrophic growth. In vitro nitrogenase enzyme assays showed that at a low concentration potassium glutamate enhanced activity but at higher concentrations this compound inhibited activity; 50% inhibition occurred at a potassium glutamate concentration of approximately 400 mM.

  4. Novel European free-living, non-diazotrophic Bradyrhizobium isolates from contrasting soils that lack nodulation and nitrogen fixation genes - a genome comparison

    Science.gov (United States)

    Jones, Frances Patricia; Clark, Ian M.; King, Robert; Shaw, Liz J.; Woodward, Martin J.; Hirsch, Penny R.

    2016-05-01

    The slow-growing genus Bradyrhizobium is biologically important in soils, with different representatives found to perform a range of biochemical functions including photosynthesis, induction of root nodules and symbiotic nitrogen fixation and denitrification. Consequently, the role of the genus in soil ecology and biogeochemical transformations is of agricultural and environmental significance. Some isolates of Bradyrhizobium have been shown to be non-symbiotic and do not possess the ability to form nodules. Here we present the genome and gene annotations of two such free-living Bradyrhizobium isolates, named G22 and BF49, from soils with differing long-term management regimes (grassland and bare fallow respectively) in addition to carbon metabolism analysis. These Bradyrhizobium isolates are the first to be isolated and sequenced from European soil and are the first free-living Bradyrhizobium isolates, lacking both nodulation and nitrogen fixation genes, to have their genomes sequenced and assembled from cultured samples. The G22 and BF49 genomes are distinctly different with respect to size and number of genes; the grassland isolate also contains a plasmid. There are also a number of functional differences between these isolates and other published genomes, suggesting that this ubiquitous genus is extremely heterogeneous and has roles within the community not including symbiotic nitrogen fixation.

  5. Nitrogen fixation associated with development and localization of mixed populations of Cellulomonas species and Azospirillium brasilense grown on cellulose or wheat straw

    Energy Technology Data Exchange (ETDEWEB)

    Halsall, D.M.; Goodchild, D.J.

    1986-04-01

    Mixed cultures of Cellulomonas sp. and Azospirillum brasilense were grown with straw or cellulose as the carbon source under conditions favoring the fixation of atmospheric nitrogen. Rapid increases in cell numbers, up to 10/sup 9/ cells per g of substrate, were evident after 4 and 5 days of incubation at 30 degrees C for cellulose and straw, respectively. Nitrogen fixation (detected by acetylene reduction measured on parallel cultures) commenced after 2 and 4 days of incubation for straw and cellulose, respectively, and continued for the duration of the experiment. Pure cultures of Cellulomonas sp. showed an increase in cell numbers, but CO/sub 2/ production was low, and acetylene reduction was not detected on either cellulose or straw. Pure cultures of A. brasilense on cellulose showed an inital increase in cell numbers (10/sup 7/ cells per g of substrate) over 4 days, followed by a decline presumably caused by the exhaustion of available carbon substrate. On straw, A. brasilense increased to 10/sup 9/ cells per g of substrate over 5 days and then declined slowly; this growth was accompanied by acetylene reduction. Scanning electron micrographs of straw incubated with a mixture under the above conditions for 8 days showed cells of both species in close proximity to each other. Evidence was furnished that the close spatial relatioship of cells from the two species facilitated the mutally beneficial association between them and thus increased the efficiency with which the products of straw breakdown were used for nitrogen fixation. 17 references.

  6. Radiation application for upgrading of bioresources - Development of antifungal and/or nitrogen fixative microbes

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki Sung; Ko, Dong Kyu; Han, Gab Jin [Paichai University, Taejon (Korea)

    2000-04-01

    (1) In this study, the antifungal bacteria six strains were isolated from various environment located in Chung-cheong area, Korea. These isolates were identified the genera Bacillus sp, Pseudomonas sp. through morphological, physiological and biochemical analysis. Strains KL3362 and KL3397 were identified as Pseudomonas aurantiaca and Alcaligenes faecalis, respectively. Considering antifungal(AF) spectrum, strain KL3303, 3334, and 3341 show the broad range, KL3362 and KL3397 the narrow range of AF activity on a number of pathogenic fungi. Therefore, strains KL3341 and KL3362 were selected as the strong candidate of antifungal bacteria on every purpose and usage related with our research goal. (2) KL3341 producing-antifungal substances were consisted of five different kinds of low molecular weight polypeptides (3) Optimal conditions for the production of antifungal substances were analyzed under various environmental conditions. Growth rates were different according to carbon and nitrogen source, antifungal substance production yields were not different, however. Product of antifungal substances according t phosphate is proportional to the concentration. And productivity of antifungal substances was generally high in the range 30 {approx} 37 deg. C at pH 7. In case of adding vitamin B1 or lysine to medium, the antifungal activity was enhanced. (4) Mutants with enhanced antifungal activities were constructed by radiation of {gamma}-ray. (5) AF strains were screened and selected from this research can be used in the microbial biocides as well as multifunctional bio-controllers in order to remove plant pathogenic fungi and to clarify the polluted environment. Due to their excellent degradation capability for agricultural and/or organic substances, they also can be used to improve soil quality, to ferment compost and to clean up the environment. 35 refs., 17 figs., 15 tabs. (Author)

  7. Nitrogen removal process optimization in New York City WPCPS: a case study of Wards Island WPCP.

    Science.gov (United States)

    Ramalingam, K; Fillos, J; Musabyimana, M; Deur, A; Beckmann, K

    2009-01-01

    The New York City Department of Environmental Protection has been engaged in a continuous process to develop a nitrogen removal program to reduce the nitrogen mass discharge from its water pollution control plants, (WPCPs), from 49,158 kg/d to 20,105 kg/d by the year 2017 as recommended by the Long Island Sound Study. As part of the process, a comprehensive research effort was undertaken involving bench, pilot and full scale studies to identify the most effective way to upgrade and optimize the existing WPCPs. Aeration tank 13 (AT-13) at the Wards Island WPCP was particularly attractive as a full-scale research facility because its aeration tank with its dedicated final settling tanks and RAS pumps could be isolated from the remaining treatment facilities. The nitrogen removal performance of AT-13, which, at the time, was operated as a "basic step feed BNR Facility", was evaluated and concurrently nitrification kinetic parameters were measured using in-situ bench scale experiments. Additional bench scale experiments provided denitrification rates using different sources of carbon and measurement of the maximum specific growth rate of nitrifying bacteria. The combined findings were then used to upgrade AT-13 to a "full" BNR facility with carbon and alkalinity addition. This paper will focus on the combined bench and full scale results that were the basis for the consequent upgrade.

  8. Elevated CO2 Increases Nitrogen Fixation at the Reproductive Phase Contributing to Various Yield Responses of Soybean Cultivars

    Directory of Open Access Journals (Sweden)

    Yansheng Li

    2017-09-01

    Full Text Available Nitrogen deficiency limits crop performance under elevated CO2 (eCO2, depending on the ability of plant N uptake. However, the dynamics and redistribution of N2 fixation, and fertilizer and soil N use in legumes under eCO2 have been little studied. Such an investigation is essential to improve the adaptability of legumes to climate change. We took advantage of genotype-specific responses of soybean to increased CO2 to test which N-uptake phenotypes are most strongly related to enhanced yield. Eight soybean cultivars were grown in open-top chambers with either 390 ppm (aCO2 or 550 ppm CO2 (eCO2. The plants were supplied with 100 mg N kg−1 soil as 15N-labeled calcium nitrate, and harvested at the initial seed-filling (R5 and full-mature (R8 stages. Increased yield in response to eCO2 correlated highly (r = 0.95 with an increase in symbiotically fixed N during the R5 to R8 stage. In contrast, eCO2 only led to small increases in the uptake of fertilizer-derived and soil-derived N during R5 to R8, and these increases did not correlate with enhanced yield. Elevated CO2 also decreased the proportion of seed N redistributed from shoot to seeds, and this decrease strongly correlated with increased yield. Moreover, the total N uptake was associated with increases in fixed-N per nodule in response to eCO2, but not with changes in nodule biomass, nodule density, or root length.

  9. Characteristic of riverine dissolved inorganic nitrogen export in subtropic high-standing island, Taiwan

    Science.gov (United States)

    Lee, Li-Chin; Huang, -Chuan, Jr.; Lee, Tsung-Yu; Shih, Yu-Ting

    2015-04-01

    Extreme increase of anthropogenic nitrogen (e.g. fertilizer and excretion) has altered the nitrogen cycling and terrestrial ecosystems. Taiwan located between eastern Asia and Oceania is the hotspot of global riverine DIN (dissolved inorganic nitrogen, including NH4, NO3, and NO2) export, but rarely documented comprehensively. Totally 50 catchments, covering 2/3 of this island, with different anthropogenic activities are involved in this study. The monthly sampling for NH4 and seasonal sampling for NO3 and NO2 supplemented with daily discharge are used to estimate the riverine DIN export. Meanwhile, the landscape characteristics, land-use, and population density are also used to discriminate the characteristics of riverine DIN export. Results showed that the observed riverine DIN concentration and yield vary from 17.7-603.5 μM and 575.0-15588.9 kg-N km-2 yr-1 corresponding to the increase of anthropogenic activities. The arithmetic mean of DIN concentration and yield are 126.7μM and 3594.7 kg-N km-2 yr-1, respectively. The unexpected high yields can attribute to abundant precipitation, heavy fertilizer application, and high population. For concentration variation, no significant variation can be found in the pristine and agriculture-dominated catchments, whereas the strong dilution effect in the wet season is characterized in the intensively-disturbed catchments. Although there are some seasonal variations in concentration, the yields in wet season are almost doubled than that in dry season indicating the strong control of streamflow. For speciation, NH4 is the dominant species in intensively-disturbed catchment, but NO3 dominates the DIN composition for the pristine and agriculture-dominated catchments. Our result can provide a strong basis for supplementary estimation for regional to global study and DIN export control which is the aim of the Kampala Declaration on global nitrogen management. Keywords: dissolved inorganic nitrogen, anthropogenic nitrogen

  10. Nitrogen fixation by mung bean (Vigna radiata L.) under field conditions in the Philippines as quantified by 15N isotope dilution

    International Nuclear Information System (INIS)

    Rosales, C.M.; Rivera, F.; Hautia, R.A.; Del Rosario, E.

    1995-05-01

    Nitrogen fixation by five mung bean genotypes (Vigna radiata L.) was estimated using two reference crops at two locations in the Philippines. The percentage of N derived from fixation and the amount of N-fixed ranged from 64 to 87% and 43 to 85 kg N/ha respectively at one location and from 36.6 to 72% and 21 to 85 kg N/ha at another location using cotton as reference crop. Maize was not a good reference crop. The highest mung bean seed yields obtained were 1.99 t/ha and 0.86 t/ha in the two locations. As to residual benefits, corn dry matter seeds yield were higher when grown following N 2 -fixing mung bean than after non-fixing corn or cotton. (author). 25 refs., 1 fig., 5 tabs

  11. Assessing the effects of iron enrichment across holobiont compartments reveals reduced microbial nitrogen fixation in the Red Sea coral Pocillopora verrucosa

    KAUST Repository

    Radecker, Nils; Pogoreutz, Claudia; Ziegler, Maren; Ashok, Ananya; Barreto, Marcelle M.; Chaidez, Veronica; Grupstra, Carsten G. B.; Ng, Yi Mei; Perna, Gabriela; Aranda, Manuel; Voolstra, Christian R.

    2017-01-01

    The productivity of coral reefs in oligotrophic tropical waters is sustained by an efficient uptake and recycling of nutrients. In reef-building corals, the engineers of these ecosystems, this nutrient recycling is facilitated by a constant exchange of nutrients between the animal host and endosymbiotic photosynthetic dinoflagellates (zooxanthellae), bacteria, and other microbes. Due to the complex interactions in this so-called coral holobiont, it has proven difficult to understand the environmental limitations of productivity in corals. Among others, the micronutrient iron has been proposed to limit primary productivity due to its essential role in photosynthesis and bacterial processes. Here, we tested the effect of iron enrichment on the physiology of the coral Pocillopora verrucosa from the central Red Sea during a 12-day experiment. Contrary to previous reports, we did not see an increase in zooxanthellae population density or gross photosynthesis. Conversely, respiration rates were significantly increased, and microbial nitrogen fixation was significantly decreased. Taken together, our data suggest that iron is not a limiting factor of primary productivity in Red Sea corals. Rather, increased metabolic demands in response to iron enrichment, as evidenced by increased respiration rates, may reduce carbon (i.e., energy) availability in the coral holobiont, resulting in reduced microbial nitrogen fixation. This decrease in nitrogen supply in turn may exacerbate the limitation of other nutrients, creating a negative feedback loop. Thereby, our results highlight that the effects of iron enrichment appear to be strongly dependent on local environmental conditions and ultimately may depend on the availability of other nutrients.

  12. Assessing the effects of iron enrichment across holobiont compartments reveals reduced microbial nitrogen fixation in the Red Sea coral Pocillopora verrucosa

    KAUST Repository

    Radecker, Nils

    2017-07-31

    The productivity of coral reefs in oligotrophic tropical waters is sustained by an efficient uptake and recycling of nutrients. In reef-building corals, the engineers of these ecosystems, this nutrient recycling is facilitated by a constant exchange of nutrients between the animal host and endosymbiotic photosynthetic dinoflagellates (zooxanthellae), bacteria, and other microbes. Due to the complex interactions in this so-called coral holobiont, it has proven difficult to understand the environmental limitations of productivity in corals. Among others, the micronutrient iron has been proposed to limit primary productivity due to its essential role in photosynthesis and bacterial processes. Here, we tested the effect of iron enrichment on the physiology of the coral Pocillopora verrucosa from the central Red Sea during a 12-day experiment. Contrary to previous reports, we did not see an increase in zooxanthellae population density or gross photosynthesis. Conversely, respiration rates were significantly increased, and microbial nitrogen fixation was significantly decreased. Taken together, our data suggest that iron is not a limiting factor of primary productivity in Red Sea corals. Rather, increased metabolic demands in response to iron enrichment, as evidenced by increased respiration rates, may reduce carbon (i.e., energy) availability in the coral holobiont, resulting in reduced microbial nitrogen fixation. This decrease in nitrogen supply in turn may exacerbate the limitation of other nutrients, creating a negative feedback loop. Thereby, our results highlight that the effects of iron enrichment appear to be strongly dependent on local environmental conditions and ultimately may depend on the availability of other nutrients.

  13. Temporal and spatial variability of biological nitrogen fixation off the upwelling system of central Chile (35-38.5°S)

    Science.gov (United States)

    Fernandez, Camila; González, Maria Lorena; Muñoz, Claudia; Molina, Veronica; Farias, Laura

    2015-05-01

    Although N2 fixation could represent a supplementary source of bioavailable nitrogen in coastal upwelling areas and underlying oxygen minimum zones (OMZs), the limited data available prevent assessing its variability and biogeochemical significance. Here we report the most extensive N2 fixation data set gathered to date in the upwelling area off central Chile (36°S). It covers interannual to high frequency time scales in an area of about 82,500 km2 in the eastern South Pacific (ESP). Because heterotrophic N2 fixation may be regulated by DOM availability in the ESP, we conducted experiments at different oxygen conditions and included DOM amendments in order to test diazotrophic activity. Rates in the euphotic zone showed strong temporal variability which resulted in values reaching 0.5 nmol L-1 d-1 in 2006 (average 0.32 ± 0.17 nmol L-1 d-1) and up to 126.8 nmol L-1 d-1 (average 24.75 ± 37.9 nmol L-1 d-1) in 2011. N2 fixation in subsurface suboxic conditions (1.5 ± 1.16 nmol L-1 d-1) also occurred mainly during late summer and autumn while virtually absent in winter. The diversity of diazotrophs was dominated by heterotrophs, with higher richness in surface compared to OMZ waters. Rates in oxygen depleted conditions could exceed values obtained in the euphotic layer, but rates were not dependent on the availability of dissolved organic matter. N2 fixation also showed a positive correlation with total chlorophyll and the C:N ratio of phytoplankton, but not to the P excess compared to N. We conclude that the diazotrophic community responds to the composition of phytoplankton rather than the extent of N deficiency and the availability of bulk DOM in this system.

  14. A Comparative Nitrogen Balance and Productivity Analysis of Legume and Non-legume Supported Cropping Systems: The Potential Role of Biological Nitrogen Fixation.

    Science.gov (United States)

    Iannetta, Pietro P M; Young, Mark; Bachinger, Johann; Bergkvist, Göran; Doltra, Jordi; Lopez-Bellido, Rafael J; Monti, Michele; Pappa, Valentini A; Reckling, Moritz; Topp, Cairistiona F E; Walker, Robin L; Rees, Robert M; Watson, Christine A; James, Euan K; Squire, Geoffrey R; Begg, Graham S

    2016-01-01

    The potential of biological nitrogen fixation (BNF) to provide sufficient N for production has encouraged re-appraisal of cropping systems that deploy legumes. It has been argued that legume-derived N can maintain productivity as an alternative to the application of mineral fertilizer, although few studies have systematically evaluated the effect of optimizing the balance between legumes and non N-fixing crops to optimize production. In addition, the shortage, or even absence in some regions, of measurements of BNF in crops and forages severely limits the ability to design and evaluate new legume-based agroecosystems. To provide an indication of the magnitude of BNF in European agriculture, a soil-surface N-balance approach was applied to historical data from 8 experimental cropping systems that compared legume and non-legume crop types (e.g., grains, forages and intercrops) across pedoclimatic regions of Europe. Mean BNF for different legume types ranged from 32 to 115 kg ha -1 annually. Output in terms of total biomass (grain, forage, etc.) was 30% greater in non-legumes, which used N to produce dry matter more efficiently than legumes, whereas output of N was greater from legumes. When examined over the crop sequence, the contribution of BNF to the N-balance increased to reach a maximum when the legume fraction was around 0.5 (legume crops were present in half the years). BNF was lower when the legume fraction increased to 0.6-0.8, not because of any feature of the legume, but because the cropping systems in this range were dominated by mixtures of legume and non-legume forages to which inorganic N as fertilizer was normally applied. Forage (e.g., grass and clover), as opposed to grain crops in this range maintained high outputs of biomass and N. In conclusion, BNF through grain and forage legumes has the potential to generate major benefit in terms of reducing or dispensing with the need for mineral N without loss of total output.

  15. A comparative nitrogen balance and productivity analysis of legume and non-legume supported cropping systems: the potential role of biological nitrogen fixation

    Directory of Open Access Journals (Sweden)

    Pietro P M Iannetta

    2016-11-01

    Full Text Available The potential of biological nitrogen fixation (BNF to provide sufficient N for production have encouraged re-appraisal of cropping systems that deploy legumes. It has been argued that legume-derived N can maintain productivity as an alternative to the application of mineral fertiliser, although few studies have systematically evaluated the effect of optimising the balance between legumes and non N-fixing crops to optimise production. In addition, the shortage, or even absence in some regions, of measurements of BNF in crops and forages severely limits the ability to design and evaluate new, legume–based agroecosystems. To provide an indication of the magnitude of BNF in European agriculture, a soil-surface N-balance approach was applied to historical data from 8 experimental cropping systems that compared legume and non-legume crop types (e.g. grains, forages and intercrops across pedoclimatic regions of Europe. Mean BNF for different legume types ranged from 32-115 kg ha-1 annually. Output in terms of total biomass (grain, forage, etc. was 30% greater in non-legumes, which used N to produce dry matter more efficiently than legumes, whereas output of N was greater from legumes. When examined over the crop sequence, the contribution of BNF to the N-balance increased to reach a maximum when the legume fraction was around 0.5 (legume crops were present in half the years. BNF was lower when the legume fraction increased to 0.6-0.8, not because of any feature of the legume, but because the cropping systems in this range were dominated by mixtures of legume and non-legume forages to which inorganic N as fertiliser was normally applied. Forage (e.g. grass and clover, as opposed to grain crops in this range maintained high outputs of biomass and N. In conclusion, BNF through grain and forage legumes have the potential to generate major benefit in terms of reducing or dispensing with the need for mineral N without loss of total output.

  16. Biological fixation of nitrogen in three tropical feed crops leguminous and its transfer to Brachiaria humidicola in association

    International Nuclear Information System (INIS)

    Gil, Jose Luis; Guenni, Orlando; Espinoza, Yusmary

    1997-01-01

    In Cojedes State drained savannas an experiment was carried out with the purpose of: a) to determine the biological fixation of nitrogen (BFN) in three tropical feed crops leguminous (Centrosema pubescens Cp, Stylosanthes hamata Sh and Pueraria phaseoloides, Pp) cultivated in monoculture and associated with the gramineous Brachiaria humidicola (Bh); b) to evaluate the transfer potential of N fixed to the air to the companion gramineous. To calculate the proportion of N biologically fixed, the technique of isotopic dilution was used with N 1 5. The fertilizer (enriched ammonium sulphate to 10% with N 1 5) was added during the rainy season in two regrowth periods. In each case, the aerial biomass was determined after 90 days of growth, being analyzed the total content of N and N 1 5 in the foliage. In both periods of evaluation, the association Bh / Cp was stabler, with a proportion of the leguminous in the mixture 20-30%. As monoculture, Bh had the biggest production of aerial biomass (972 gm -2 ) among all the treatments for the first period of evaluation (middle rainy season). The total production of dry matter (DM) in association, was modified between 574 (Bh/Cp) and 807 gm -2 (Bh/Sh). The production DM for the second period of evaluation (end rainy season) followed the same tendency, being observed, however, a general decrease in the yields due to the beginning of drought. The content of N in the leguminous was always higher than in Bh. Nevertheless, Bh in association reached an accumulation bigger than N (14 gm -2 ) due to its higher rate of growth. The leguminous alone had a significant proportion of N (47-69%) derivated of the BFN. Cp was the one that showed higher values of BFN (51-69%). Likewise, one observes a high proportion (57-76%) of element starting from the BFN when the leguminous were cultivated in association. In this sense one doesn't observe a clear transfer of N from the leguminous to the gramineous, since the contents of N 1 5 in Bh they were

  17. Economics of the production of liquid fuel and fertilizer by the fixation of atmospheric carbon and nitrogen using nuclear power

    International Nuclear Information System (INIS)

    Baron, S.; Steinberg, M.

    1975-01-01

    The economics of using reactor power during off-peak period for the production of H 2 and fixation of C to produce methanol and the fixation of N 2 for the production of NH 3 are reviewed to show that it is economically feasible with the current prices of fossil fuels. The incremental energy costs for synthesis processes are summarized. Methanol and ammonia production and economics are analyzed. An additional economic advantage would be the possible production of single cell protein

  18. Tricalcium phosphate solubilization and nitrogen fixation by newly isolated Aneurinibacillus aneurinilyticus CKMV1 from rhizosphere of Valeriana jatamansi and its growth promotional effect

    Directory of Open Access Journals (Sweden)

    Anjali Chauhan

    Full Text Available Abstract Aneurinibacillus aneurinilyticus strain CKMV1 was isolated from rhizosphere of Valeriana jatamansi and possessed multiple plant growth promoting traits like production of phosphate solubilization (260 mg/L, nitrogen fixation (202.91 nmol ethylene mL-1 h-1, indole-3-acetic acid (IAA (8.1 µg/mL, siderophores (61.60%, HCN (hydrogen cyanide production and antifungal activity. We investigated the ability of isolate CKMV1 to solubilize insoluble P via mechanism of organic acid production. High-performance liquid chromatography (HPLC study showed that isolate CKMV1 produced mainly gluconic (1.34% and oxalic acids. However, genetic evidences for nitrogen fixation and phosphate solubilization by organic acid production have been reported first time for A. aneurinilyticus strain CKMV1. A unique combination of glucose dehydrogenase (gdh gene and pyrroloquinoline quinone synthase (pqq gene, a cofactor of gdh involved in phosphate solubilization has been elucidated. Nitrogenase (nif H gene for nitrogen fixation was reported from A. aneurinilyticus. It was notable that isolate CKMV1 exhibited highest antifungal against Sclerotium rolfsii (93.58% followed by Fusarium oxysporum (64.3%, Dematophora necatrix (52.71%, Rhizoctonia solani (91.58%, Alternaria sp. (71.08% and Phytophthora sp. (71.37%. Remarkable increase was observed in seed germination (27.07%, shoot length (42.33%, root length (52.6%, shoot dry weight (62.01% and root dry weight (45.7% along with NPK (0.74, 0.36, 1.82% content of tomato under net house condition. Isolate CKMV1 possessed traits related to plant growth promotion, therefore, could be a potential candidate for the development of biofertiliser or biocontrol agent and this is the first study to include the Aneurinibacillus as PGPR.

  19. Tricalcium phosphate solubilization and nitrogen fixation by newly isolated Aneurinibacillus aneurinilyticus CKMV1 from rhizosphere of Valeriana jatamansi and its growth promotional effect.

    Science.gov (United States)

    Chauhan, Anjali; Guleria, Shiwani; Balgir, Praveen P; Walia, Abhishek; Mahajan, Rishi; Mehta, Preeti; Shirkot, Chand Karan

    Aneurinibacillus aneurinilyticus strain CKMV1 was isolated from rhizosphere of Valeriana jatamansi and possessed multiple plant growth promoting traits like production of phosphate solubilization (260mg/L), nitrogen fixation (202.91nmolethylenemL -1 h -1 ), indole-3-acetic acid (IAA) (8.1μg/mL), siderophores (61.60%), HCN (hydrogen cyanide) production and antifungal activity. We investigated the ability of isolate CKMV1 to solubilize insoluble P via mechanism of organic acid production. High-performance liquid chromatography (HPLC) study showed that isolate CKMV1 produced mainly gluconic (1.34%) and oxalic acids. However, genetic evidences for nitrogen fixation and phosphate solubilization by organic acid production have been reported first time for A. aneurinilyticus strain CKMV1. A unique combination of glucose dehydrogenase (gdh) gene and pyrroloquinoline quinone synthase (pqq) gene, a cofactor of gdh involved in phosphate solubilization has been elucidated. Nitrogenase (nif H) gene for nitrogen fixation was reported from A. aneurinilyticus. It was notable that isolate CKMV1 exhibited highest antifungal against Sclerotium rolfsii (93.58%) followed by Fusarium oxysporum (64.3%), Dematophora necatrix (52.71%), Rhizoctonia solani (91.58%), Alternaria sp. (71.08%) and Phytophthora sp. (71.37%). Remarkable increase was observed in seed germination (27.07%), shoot length (42.33%), root length (52.6%), shoot dry weight (62.01%) and root dry weight (45.7%) along with NPK (0.74, 0.36, 1.82%) content of tomato under net house condition. Isolate CKMV1 possessed traits related to plant growth promotion, therefore, could be a potential candidate for the development of biofertiliser or biocontrol agent and this is the first study to include the Aneurinibacillus as PGPR. Copyright © 2016 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

  20. Constraining the Exchange of Carbon and Nitrogen in Eastern Long Island Sound

    Science.gov (United States)

    Byrd, A.; Warren, J. K.; Vlahos, P.; Whitney, M. M.

    2017-12-01

    Long Island Sound (LIS) is an urban estuary on the US east coast that undergoes seasonal hypoxia in its western and central regions. Currently, the budgets of both carbon and nitrogen in LIS remain unbalanced, despite their importance to the efficient and strategic management of the health of coastal and aquatic ecosystems. In this study, we evaluated the exchange values of C and N at the mouth of LIS (the Race), in order to constrain export through this important boundary. Discreet water samples were collected during four 15 km transects over the Race at five stations and three depths each station to resolve the temporal variability over a complete tidal cycle, in order to assess both net flux and variations across the tidal period. By evaluating both the particulate and dissolved pools of carbon (POC, PIC, DOC, DIC) and nitrogen (PON, DON, DIN) during the spring, summer and winter (high and low flow conditions) and pairing these measurements with physical data, we were able to identify a variety of forcing and export regimes. Preliminary results indicate the importance of spatial and tidal variability on flux estimates and show little or no export (and sometimes import) of nitrogen and significant export of organic carbon.

  1. Transcriptional profiling of nitrogen fixation and the role of NifA in the diazotrophic endophyte Azoarcus sp. strain BH72.

    Directory of Open Access Journals (Sweden)

    Abhijit Sarkar

    Full Text Available BACKGROUND: The model endophyte Azoarcus sp. strain BH72 is known to contribute fixed nitrogen to its host Kallar grass and also expresses nitrogenase genes endophytically in rice seedlings. Availability of nitrogen is a signal regulating the transcription of nitrogenase genes. Therefore, we analysed global transcription in response to differences in the nitrogen source. METHODOLOGY/PRINCIPAL FINDINGS: A DNA microarray, comprising 70-mer oligonucleotides representing 3989 open reading frames of the genome of strain BH72, was used for transcriptome studies. Transcription profiles of cells grown microaerobically on N2 versus ammonium were compared. Expression of 7.2% of the genes was significantly up-regulated, and 5.8% down-regulated upon N2 fixation, respectively. A parallel genome-wide prediction of σ(54-type promoter elements mapped to the upstream region of 38 sequences of which 36 were modulated under the N2 response. In addition to modulation of genes related to N2 fixation, the expressions of gene clusters that might be related to plant-microbe interaction and of several transcription factors were significantly enhanced. While comparing under N2-fixation conditions the transcriptome of wild type with a nifLA(- insertion mutant, NifA being the essential transcriptional activator for nif genes, 24.5% of the genome was found to be affected in expression. A genome-wide prediction of 29 NifA binding sequences matched to 25 of the target genes whose expression was differential during microarray analysis, some of which were putatively negatively regulated by NifA. For selected genes, differential expression was corroborated by real time RT-PCR studies. CONCLUSION/SIGNIFICANCE: Our data suggest that life under conditions of nitrogen fixation is an important part of the lifestyle of strain BH72 in roots, as a wide range of genes far beyond the nif regulon is modulated. Moreover, the NifA regulon in strain BH72 appears to encompass a wider range of

  2. Loss of the nodule-specific cysteine rich peptide, NCR169, abolishes symbiotic nitrogen fixation in the Medicago truncatula dnf7 mutant.

    Science.gov (United States)

    Horváth, Beatrix; Domonkos, Ágota; Kereszt, Attila; Szűcs, Attila; Ábrahám, Edit; Ayaydin, Ferhan; Bóka, Károly; Chen, Yuhui; Chen, Rujin; Murray, Jeremy D; Udvardi, Michael K; Kondorosi, Éva; Kaló, Péter

    2015-12-08

    Host compatible rhizobia induce the formation of legume root nodules, symbiotic organs within which intracellular bacteria are present in plant-derived membrane compartments termed symbiosomes. In Medicago truncatula nodules, the Sinorhizobium microsymbionts undergo an irreversible differentiation process leading to the development of elongated polyploid noncultivable nitrogen fixing bacteroids that convert atmospheric dinitrogen into ammonia. This terminal differentiation is directed by the host plant and involves hundreds of nodule specific cysteine-rich peptides (NCRs). Except for certain in vitro activities of cationic peptides, the functional roles of individual NCR peptides in planta are not known. In this study, we demonstrate that the inability of M. truncatula dnf7 mutants to fix nitrogen is due to inactivation of a single NCR peptide, NCR169. In the absence of NCR169, bacterial differentiation was impaired and was associated with early senescence of the symbiotic cells. Introduction of the NCR169 gene into the dnf7-2/NCR169 deletion mutant restored symbiotic nitrogen fixation. Replacement of any of the cysteine residues in the NCR169 peptide with serine rendered it incapable of complementation, demonstrating an absolute requirement for all cysteines in planta. NCR169 was induced in the cell layers in which bacteroid elongation was most pronounced, and high expression persisted throughout the nitrogen-fixing nodule zone. Our results provide evidence for an essential role of NCR169 in the differentiation and persistence of nitrogen fixing bacteroids in M. truncatula.

  3. Isotopes in biological dinitrogen fixation

    Energy Technology Data Exchange (ETDEWEB)

    1978-10-01

    Nineteen papers were presented at the conference. Some topics discussed are as follows: biochemistry and genetics of dinitrogen fixation; genetics of the Rhizobium-legume symbiosis and of the nitrogen-fixing bacteria; studies on nonsymbiotic dinitrogen fixation in grass-bacteria associations and blue--green algae; use of /sup 15/N and /sup 13/N for the assay of dinitrogen fixation; effects of management practices on dinitrogen fixation; economy of C and N in nitrogen-fixing legumes; and survey of international and national programs on dinitrogen fixation. (HLW)

  4. Regulation of respiration and the oxygen diffusion barrier in soybean protect symbiotic nitrogen fixation from chilling-induced inhibition and shoots from premature senescence.

    Science.gov (United States)

    van Heerden, Philippus D R; Kiddle, Guy; Pellny, Till K; Mokwala, Phatlane W; Jordaan, Anine; Strauss, Abram J; de Beer, Misha; Schlüter, Urte; Kunert, Karl J; Foyer, Christine H

    2008-09-01

    Symbiotic nitrogen fixation is sensitive to dark chilling (7 degrees C-15 degrees C)-induced inhibition in soybean (Glycine max). To characterize the mechanisms that cause the stress-induced loss of nodule function, we examined nodule structure, carbon-nitrogen interactions, and respiration in two soybean genotypes that differ in chilling sensitivity: PAN809 (PAN), which is chilling sensitive, and Highveld Top (HT), which is more chilling resistant. Nodule numbers were unaffected by dark chilling, as was the abundance of the nitrogenase and leghemoglobin proteins. However, dark chilling decreased nodule respiration rates, nitrogenase activities, and NifH and NifK mRNAs and increased nodule starch, sucrose, and glucose in both genotypes. Ureide and fructose contents decreased only in PAN nodules. While the chilling-induced decreases in nodule respiration persisted in PAN even after return to optimal temperatures, respiration started to recover in HT by the end of the chilling period. The area of the intercellular spaces in the nodule cortex and infected zone was greatly decreased in HT after three nights of chilling, an acclimatory response that was absent from PAN. These data show that HT nodules are able to regulate both respiration and the area of the intercellular spaces during chilling and in this way control the oxygen diffusion barrier, which is a key component of the nodule stress response. We conclude that chilling-induced loss of symbiotic nitrogen fixation in PAN is caused by the inhibition of respiration coupled to the failure to regulate the oxygen diffusion barrier effectively. The resultant limitations on nitrogen availability contribute to the greater chilling-induced inhibition of photosynthesis in PAN than in HT.

  5. Metabolic Adaptation, a Specialized Leaf Organ Structure and Vascular Responses to Diurnal N2 Fixation by Nostoc azollae Sustain the Astonishing Productivity of Azolla Ferns without Nitrogen Fertilizer.

    Science.gov (United States)

    Brouwer, Paul; Bräutigam, Andrea; Buijs, Valerie A; Tazelaar, Anne O E; van der Werf, Adrie; Schlüter, Urte; Reichart, Gert-Jan; Bolger, Anthony; Usadel, Björn; Weber, Andreas P M; Schluepmann, Henriette

    2017-01-01

    Sustainable agriculture demands reduced input of man-made nitrogen (N) fertilizer, yet N 2 fixation limits the productivity of crops with heterotrophic diazotrophic bacterial symbionts. We investigated floating ferns from the genus Azolla that host phototrophic diazotrophic Nostoc azollae in leaf pockets and belong to the fastest growing plants. Experimental production reported here demonstrated N-fertilizer independent production of nitrogen-rich biomass with an annual yield potential per ha of 1200 kg -1 N fixed and 35 t dry biomass. 15 N 2 fixation peaked at noon, reaching 0.4 mg N g -1 dry weight h -1 . Azolla ferns therefore merit consideration as protein crops in spite of the fact that little is known about the fern's physiology to enable domestication. To gain an understanding of their nitrogen physiology, analyses of fern diel transcript profiles under differing nitrogen fertilizer regimes were combined with microscopic observations. Results established that the ferns adapted to the phototrophic N 2 -fixing symbionts N. azollae by (1) adjusting metabolically to nightly absence of N supply using responses ancestral to ferns and seed plants; (2) developing a specialized xylem-rich vasculature surrounding the leaf-pocket organ; (3) responding to N-supply by controlling transcripts of genes mediating nutrient transport, allocation and vasculature development. Unlike other non-seed plants, the Azolla fern clock is shown to contain both the morning and evening loops; the evening loop is known to control rhythmic gene expression in the vasculature of seed plants and therefore may have evolved along with the vasculature in the ancestor of ferns and seed plants.

  6. Enzyme Production and Nitrogen Fixation by Free, Immobilized and Coimmobilized Inoculants of Trichoderma harzianum and Azospirillum brasilense and Their Possible Role in Growth Promotion of Tomato

    Directory of Open Access Journals (Sweden)

    Momein H. El-Katatny

    2010-01-01

    Full Text Available A plant growth-promoting rhizobacterium (Azospirillum brasilense strain Az and a biocontrol fungus (Trichoderma harzianum strain T24 have been evaluated for their individual and combined production of hydrolytic enzymes, nitrogen fixation and their possible role in growth promotion of tomato seedlings. The studied organisms were inoculated as free or calcium alginate-encapsulated cells. All freshly prepared macrobeads showed high encapsulation capacity (EC/% of inocula compared with dry macrobeads. Results of enzyme production did not exhibit consistent pattern of the effect of encapsulation process on enzyme production. Beads entrapping bacterial and/or fungal cells were used successfully in 3 repeated cycles in the presence of fresh sterile culture medium in each growth cycle. Enzyme production by immobilized bacterial and/or fungal cells increased as the growth cycles were repeated. Co-culturing of A. brasilense with T. harzianum (free or immobilized in semisolid nitrogen deficient medium (N-free medium enabled A. brasilense to fix nitrogen on pectin, chitin and carboxymethyl cellulose. The activity of nitrogen fixation by A. brasilense in the case of single and combined cultures with Trichoderma (using dry encapsulated beads into the sterile soil increased with the addition of carbon source. Most of inoculations with free or alginate macrobead formulations of T. harzianum and/or A. brasilense showed significant increase in the growth parameters of tomato seedlings. The root system grew more profusely in the case of all seeds treated with A. brasilense. The growth parameters of Az/T24-treated seeds using dry coimmobilized macrobeads were higher than those of the untreated control. Moreover, the effect was improved significantly in soil enriched with different C sources. Enhanced tomato seedling growth after the co-inoculation could be due to the synergistic effect of both Trichoderma and Azospirillum. Finally, co-inoculation with Azospirillum

  7. The Contamination of Commercial 15N2 Gas Stocks with 15N–Labeled Nitrate and Ammonium and Consequences for Nitrogen Fixation Measurements

    Science.gov (United States)

    Dabundo, Richard; Lehmann, Moritz F.; Treibergs, Lija; Tobias, Craig R.; Altabet, Mark A.; Moisander, Pia H.; Granger, Julie

    2014-01-01

    We report on the contamination of commercial 15-nitrogen (15N) N2 gas stocks with 15N-enriched ammonium, nitrate and/or nitrite, and nitrous oxide. 15N2 gas is used to estimate N2 fixation rates from incubations of environmental samples by monitoring the incorporation of isotopically labeled 15N2 into organic matter. However, the microbial assimilation of bioavailable 15N-labeled N2 gas contaminants, nitrate, nitrite, and ammonium, is liable to lead to the inflation or false detection of N2 fixation rates. 15N2 gas procured from three major suppliers was analyzed for the presence of these 15N-contaminants. Substantial concentrations of 15N-contaminants were detected in four Sigma-Aldrich 15N2 lecture bottles from two discrete batch syntheses. Per mole of 15N2 gas, 34 to 1900 µmoles of 15N-ammonium, 1.8 to 420 µmoles of 15N-nitrate/nitrite, and ≥21 µmoles of 15N-nitrous oxide were detected. One 15N2 lecture bottle from Campro Scientific contained ≥11 µmoles of 15N-nitrous oxide per mole of 15N2 gas, and no detected 15N-nitrate/nitrite at the given experimental 15N2 tracer dilutions. Two Cambridge Isotopes lecture bottles from discrete batch syntheses contained ≥0.81 µmoles 15N-nitrous oxide per mole 15N2, and trace concentrations of 15N-ammonium and 15N-nitrate/nitrite. 15N2 gas equilibrated cultures of the green algae Dunaliella tertiolecta confirmed that the 15N-contaminants are assimilable. A finite-differencing model parameterized using oceanic field conditions typical of N2 fixation assays suggests that the degree of detected 15N-ammonium contamination could yield inferred N2 fixation rates ranging from undetectable, detected in field assays. These results indicate that past reports of N2 fixation should be interpreted with caution, and demonstrate that the purity of commercial 15N2 gas must be ensured prior to use in future N2 fixation rate determinations. PMID:25329300

  8. The contamination of commercial 15N2 gas stocks with 15N-labeled nitrate and ammonium and consequences for nitrogen fixation measurements.

    Science.gov (United States)

    Dabundo, Richard; Lehmann, Moritz F; Treibergs, Lija; Tobias, Craig R; Altabet, Mark A; Moisander, Pia H; Granger, Julie

    2014-01-01

    We report on the contamination of commercial 15-nitrogen (15N) N2 gas stocks with 15N-enriched ammonium, nitrate and/or nitrite, and nitrous oxide. 15N2 gas is used to estimate N2 fixation rates from incubations of environmental samples by monitoring the incorporation of isotopically labeled 15N2 into organic matter. However, the microbial assimilation of bioavailable 15N-labeled N2 gas contaminants, nitrate, nitrite, and ammonium, is liable to lead to the inflation or false detection of N2 fixation rates. 15N2 gas procured from three major suppliers was analyzed for the presence of these 15N-contaminants. Substantial concentrations of 15N-contaminants were detected in four Sigma-Aldrich 15N2 lecture bottles from two discrete batch syntheses. Per mole of 15N2 gas, 34 to 1900 µmoles of 15N-ammonium, 1.8 to 420 µmoles of 15N-nitrate/nitrite, and ≥21 µmoles of 15N-nitrous oxide were detected. One 15N2 lecture bottle from Campro Scientific contained ≥11 µmoles of 15N-nitrous oxide per mole of 15N2 gas, and no detected 15N-nitrate/nitrite at the given experimental 15N2 tracer dilutions. Two Cambridge Isotopes lecture bottles from discrete batch syntheses contained ≥0.81 µmoles 15N-nitrous oxide per mole 15N2, and trace concentrations of 15N-ammonium and 15N-nitrate/nitrite. 15N2 gas equilibrated cultures of the green algae Dunaliella tertiolecta confirmed that the 15N-contaminants are assimilable. A finite-differencing model parameterized using oceanic field conditions typical of N2 fixation assays suggests that the degree of detected 15N-ammonium contamination could yield inferred N2 fixation rates ranging from undetectable, detected in field assays. These results indicate that past reports of N2 fixation should be interpreted with caution, and demonstrate that the purity of commercial 15N2 gas must be ensured prior to use in future N2 fixation rate determinations.

  9. The Micro-RNA172c-APETALA2-1 Node as a Key Regulator of the Common Bean-Rhizobium etli Nitrogen Fixation Symbiosis1[OPEN

    Science.gov (United States)

    Nova-Franco, Bárbara; Íñiguez, Luis P.; Valdés-López, Oswaldo; Leija, Alfonso; Fuentes, Sara I.; Ramírez, Mario; Paul, Sujay

    2015-01-01

    Micro-RNAs are recognized as important posttranscriptional regulators in plants. The relevance of micro-RNAs as regulators of the legume-rhizobia nitrogen-fixing symbiosis is emerging. The objective of this work was to functionally characterize the role of micro-RNA172 (miR172) and its conserved target APETALA2 (AP2) transcription factor in the common bean (Phaseolus vulgaris)-Rhizobium etli symbiosis. Our expression analysis revealed that mature miR172c increased upon rhizobial infection and continued increasing during nodule development, reaching its maximum in mature nodules and decaying in senescent nodules. The expression of AP2-1 target showed a negative correlation with miR172c expression. A drastic decrease in miR172c and high AP2-1 mRNA levels were observed in ineffective nodules. Phenotypic analysis of composite bean plants with transgenic roots overexpressing miR172c or a mutated AP2-1 insensitive to miR172c cleavage demonstrated the pivotal regulatory role of the miR172 node in the common bean-rhizobia symbiosis. Increased miR172 resulted in improved root growth, increased rhizobial infection, increased expression of early nodulation and autoregulation of nodulation genes, and improved nodulation and nitrogen fixation. In addition, these plants showed decreased sensitivity to nitrate inhibition of nodulation. Through transcriptome analysis, we identified 114 common bean genes that coexpressed with AP2-1 and proposed these as being targets for transcriptional activation by AP2-1. Several of these genes are related to nodule senescence, and we propose that they have to be silenced, through miR172c-induced AP2-1 cleavage, in active mature nodules. Our work sets the basis for exploring the miR172-mediated improvement of symbiotic nitrogen fixation in common bean, the most important grain legume for human consumption. PMID:25739700

  10. Effects of elevated carbon dioxide concentration on growth and nitrogen fixation in Alnus glutinosa in a long-term field experiment

    Energy Technology Data Exchange (ETDEWEB)

    Temperton, V. M.; Jackson, G.; Barton, C. V. M.; Jarvis, P. G. [Edinburgh Univ., Inst. of Ecology and Resource Management, Edinburgh (United Kingdom); Grayston, S. J. [Macaulay Land Use Research Inst., Plant-Soil Interaction Group, Aberdeen (United Kingdom)

    2003-10-01

    Total biomass, relative growth rate, net assimilation rate, leaf area and net photosynthetic rate of nitrogen-fixing were measured in common alder trees, grown for three years in open-top chambers in the presence of either ambient or elevated atmospheric carbon dioxide, and in two soil nitrogen regimes: i.e. full nutrient solution or no fertilizer. The objective was to clarify the relationship between elevated carbon dioxide and the rate of nitrogen fixation of nodulated trees growing under field conditions. Results showed that growth in elevated carbon dioxide stimulated net photosynthesis and total biomass accumulation. However, relative growth rate was not significantly affected by elevated carbon dioxide. Leaf area and leaf phosphorus concentration were also unaffected. Nodule mass on roots of unfertilized trees exposed to elevated carbon dioxide increased, compared with fertilized trees exposed to ambient carbon dioxide levels. Since neither in the fertilized, nor the unfertilized trees was there any evidence of effects on growth, biomass and photosynthesis that could be attributed to the interaction of fertilizer and elevated carbon dioxide interaction, it was concluded that both types exhibit similar carbon dioxide-induced growth and photosynthetic enhancements. 40 refs., 5 tabs., 3 figs.

  11. Effects of elevated carbon dioxide concentration on growth and nitrogen fixation in Alnus glutinosa in a long-term field experiment

    International Nuclear Information System (INIS)

    Temperton, V. M.; Jackson, G.; Barton, C. V. M.; Jarvis, P. G.; Grayston, S. J.

    2003-01-01

    Total biomass, relative growth rate, net assimilation rate, leaf area and net photosynthetic rate of nitrogen-fixing were measured in common alder trees, grown for three years in open-top chambers in the presence of either ambient or elevated atmospheric carbon dioxide, and in two soil nitrogen regimes: i.e. full nutrient solution or no fertilizer. The objective was to clarify the relationship between elevated carbon dioxide and the rate of nitrogen fixation of nodulated trees growing under field conditions. Results showed that growth in elevated carbon dioxide stimulated net photosynthesis and total biomass accumulation. However, relative growth rate was not significantly affected by elevated carbon dioxide. Leaf area and leaf phosphorus concentration were also unaffected. Nodule mass on roots of unfertilized trees exposed to elevated carbon dioxide increased, compared with fertilized trees exposed to ambient carbon dioxide levels. Since neither in the fertilized, nor the unfertilized trees was there any evidence of effects on growth, biomass and photosynthesis that could be attributed to the interaction of fertilizer and elevated carbon dioxide interaction, it was concluded that both types exhibit similar carbon dioxide-induced growth and photosynthetic enhancements. 40 refs., 5 tabs., 3 figs

  12. The Effects of Mineral Nitrogen on the Fixation of Atmospheric Nitrogen by Vicia Faba L; Vliyanie mineral'nogo azota na fiksatsiyu atmosfernogo azota u Vicia Faba L.

    Energy Technology Data Exchange (ETDEWEB)

    Mouhova, G.; Apltauer, J. [Central' nyj Issledovatel' Skij Institut Rastenievodstva, Praga, CHSSR (Czech Republic)

    1968-07-01

    From 1964 to 1966 a systematic research vas carried out at the Central Research Institute for Plant Production in Prague - Ruzyne, aimed at examining the effect of gradually increased levels of nitrogen and various forms of nitrogen in nitrogen fertilizers on the yield, nitrogen content and the nodulation of the roots of horse bean (Vicia faba LQ. By means of {sup 15}N, the proportion of the total nitrogen content of the plant derived from the fertilizer as well as the total utilization of the nitrogen fertilizer by the plant were determined. The experiments were carried out in a series of greenhouse pot tests using a brown soil type, with ammonium sulphate and potassium nitrate as the nitrogen sources. Gradually-increased-levels of nitrogen in ammonium sulphate (0, 5.2, 26.2, 52.5 and 105.0 mgN/kg of soil) applied to the horse bean did not exert any substantial effect on the yield of fresh aerial parts of the horse bean, when harvested at the flowering period. The nitrogen content of tissues of the fertilized plants differed from the control plants (without nitrogen addition) only at the highest nitrogen level (2.7% compared to 3.4% N). The proportion of nitrogen absorbed from the nitrogen fertilizer by whole plant, increased almost as a linear function of nitrogen supplied. Thus the whole plant consumed 51 to 57% of the nitrogen from the first two fertilizer levels, and 64 to 69% from the last two levels of fertilizer, the 52.5-mg and 105-mg levels. In comparing nitrogen supplied as potassium nitrate with nitrogen in ammonium sulphate, at a level of 26.2 mg N/kg of soil, no difference of yield and of percentage nitrogen content in the aerial part of horse bean was found between the plants grown with the nitrogen fertilizers and control plants. The isotopical analysis of nitrogen showed that in the aerial part of horse bean plant the percentage proportion of nitrogen deriving from the fertilizer was higher when potassium nitrate was used (10.8%), than in case of

  13. A comparative study on phyllosphere nitrogen fixation by newly isolated Corynebacterium sp. & Flavobacterium sp. and their potentialities as biofertilizer.

    Science.gov (United States)

    Giri, S; Pati, B R

    2004-01-01

    A number of nitrogen fixing bacteria has been isolated from forest phyllosphere on the basis of nitrogenase activity. Among them two best isolates are selected and identified as Corynebacterium sp. AN1 & Flavobacterium sp. TK2 able to reduce 88 and 132 n mol of acetylene (10(8)cells(-1)h(-1)) respectively. They were grown in large amount and sprayed on the phyllosphere of maize plants as a substitute for nitrogenous fertilizer. Marked improvements in growth and total nitrogen content of the plant have been observed by the application of these nitrogen-fixing bacteria. An average 30-37% increase in yield was obtained, which is nearer to chemical fertilizer treatment. Comparatively better effect was obtained by application of Flavobacterium sp.

  14. Formation and maintenance of high-nitrate, low pH layers in the eastern Indian Ocean and the role of nitrogen fixation

    Directory of Open Access Journals (Sweden)

    A. M. Waite

    2013-08-01

    Full Text Available We investigated the biogeochemistry of low dissolved oxygen high-nitrate (LDOHN layers forming against the backdrop of several interleaving regional water masses in the eastern Indian Ocean, off northwest Australia adjacent to Ningaloo Reef. These water masses, including the forming Leeuwin Current, have been shown directly to impact the ecological function of Ningaloo Reef and other iconic coastal habitats downstream. Our results indicate that LDOHN layers are formed from multiple subduction events of the Eastern Gyral Current beneath the Leeuwin Current (LC; the LC originates from both the Indonesian Throughflow and tropical Indian Ocean. Density differences of up to 0.025 kg m−3 between the Eastern Gyral Current and the Leeuwin Current produce sharp gradients that can trap high concentrations of particles (measured as low transmission along the density interfaces. The oxidation of the trapped particulate matter results in local depletion of dissolved oxygen and regeneration of dissolved nitrate (nitrification. We document an associated increase in total dissolved carbon dioxide, which lowers the seawater pH by 0.04 units. Based on isotopic measurements (δ15N and δ18O of dissolved nitrate, we determine that ~ 40–100% of the nitrate found in LDOHN layers is likely to originate from nitrogen fixation, and that, regionally, the importance of N-fixation in contributing to LDOHN layers is likely to be highest at the surface and offshore.

  15. Exploring symbiotic nitrogen fixation and assimilation in pea root nodules by in vivo 15N nuclear magnetic resonance spectroscopy and liquid chromatography-mass spectrometry

    DEFF Research Database (Denmark)

    Scharff, A.M.; Egsgaard, H.; Hansen, P.E.

    2003-01-01

    Nitrogen (N) fixation and assimilation in pea (Pisum sativum) root nodules were studied by in vivo N-15 nuclear magnetic resonance (NMR) by exposing detached nodules to N-15, via a perfusion medium, while recording a time course of spectra. In vivo P-31 NMR spectroscopy was used to monitor...... the physiological state of the metabolically active nodules. The nodules were extracted after the NMR studies and analyzed for total soluble amino acid pools and N-15 labeling of individual amino acids by liquid chromatography-mass spectrometry. A substantial pool of free ammonium was observed by N-15 NMR...... labeling of Asn was observed by liquid chromatography-mass spectrometry, which is consistent with the generally accepted role of Asn as the end product of primary N assimilation in pea nodules. However, the Asn N-15 amino signal was absent in in vivo N-15 NMR spectra, which could be because...

  16. Role of Nitrogenase and Ferredoxin in the Mechanism of Bioelectrocatalytic Nitrogen Fixation by the Cyanobacteria Anabaena variabilis SA-1 Mutant Immobilized on Indium Tin Oxide (ITO) Electrodes

    International Nuclear Information System (INIS)

    Knoche, Krysti L.; Aoyama, Erika; Hasan, Kamrul; Minteer, Shelley D.

    2017-01-01

    Current ammonia production methods are costly and environmentally detrimental. Biological nitrogen fixation has implications for low cost, environmentally friendly ammonia production. It has been shown that electrochemical stimulation increases the ammonia output of the cyanobacteria SA-1 mutant of Anabaena variabilis, but the mechanism of bioelectrocatalysis has been unknown. Here, the mechanism of electrostimulated biological ammonia production is investigated by immobilization of the cyanobacteria with polyvinylamine on indium tin oxide (ITO) coated polyethylene. Cyclic voltammetry is performed in the absence and presence of various substrates and with nitrogenase repressed and nitrogenase derepressed cells to study mechanism, and cyclic voltammetry and UV–vis spectroscopy are used to identify redox moieties in the spent electrolyte. A bioelectrocatalytic signal is observed for nitrogenase derepressed A. variabilis SA-1 in the presence of N_2 and light. Results indicate that the redox protein ferredoxin mediates electron transfer between nitrogenase and the electrode to stimulate ammonia production.

  17. On the Relationship Between Hydrogen Saturation in the Tropical Atlantic Ocean and Nitrogen Fixation by the Symbiotic Diazotroph UCYN-A

    Science.gov (United States)

    Moore, R. M.; Grefe, I.; Zorz, J.; Shan, S.; Thompson, K.; Ratten, J.; LaRoche, J.

    2018-04-01

    Dissolved hydrogen measurements were made at high resolution in surface waters along a tropical north Atlantic transect between Guadeloupe and Cape Verde in 2015 (Meteor 116). Parallel water samples acquired to assess the relative abundance of the nifH gene from several types of diazotrophs, indicated that Trichodesmium and UCYN-A were dominant in this region. We show that a high degree of correlation exists between the hydrogen saturations and UCYN-A nifH abundance, and a weak correlation with Trichodesmium. The findings suggest that nitrogen fixation by UCYN-A is a major contributor to hydrogen supersaturations in this region of the ocean. The ratio of hydrogen released to nitrogen fixed has not been determined for this symbiont, but the indications are that it may be high in comparison with the small number of diazotrophs for which the ratio has been measured in laboratory cultures. We speculate that this would be consistent with the diazotroph being an exosymbiont on its haptophyte host. Our high resolution measurements of hydrogen concentrations are capable of illustrating the time and space scales of inferred activity of diazotrophs in near real-time in a way that cannot be achieved by biological sampling and rate measurements requiring incubations with 15N2. Direct measurement of high resolution spatial variability would be relatively challenging through collection and analysis of biological samples by qPCR, and extremely challenging by 15N-uptake techniques, neither of which methods yields real-time data. Nonetheless, determination of fixation rates still firmly depends on the established procedure of incubations in the presence of 15N2.

  18. The use of N-15 in the measurement of symbiotic nitrogen fixation by legumes under field condition

    International Nuclear Information System (INIS)

    Impithuksa, Viroj

    1982-01-01

    The amount of N fixation by legume crop in field condition by using 15 N can determine by the addition of labelled 15 N fertilizer into the soil and measuring the amount of labelled 15 N, soil N, and fixed N taken up by legume crop. This requires a standard crop (reference crop) as a control to determine labelled 15 N and soil N taken up by this crop. In case the same rate of labelled 15 N fertilizer is added to the legume crop and a standard crop

  19. Influence of heterogeneous ammonium availability on bacterial community structure and the expression of nitrogen fixation and ammonium transporter genes during in situ bioremediation of uranium-contaminated groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Mouser, P.J.; N' Guessan, A.L.; Elifantz, H.; Holmes, D.E.; Williams, K.H.; Wilkins, M.J.; Long, P.E.; Lovley, D.R.

    2009-04-01

    The impact of ammonium availability on microbial community structure and the physiological status and activity of Geobacter species during in situ bioremediation of uranium-contaminated groundwater was evaluated. Ammonium concentrations varied by as much as two orders of magnitude (<4 to 400 {micro}M) across the study site. Analysis of 16S rRNA gene sequences suggested that ammonium influenced the composition of the microbial community prior to acetate addition with Rhodoferax species predominating over Geobacter species at the site with the highest ammonium, and Dechloromonas species dominating at sites with lowest ammonium. However, once acetate was added, and dissimilatory metal reduction was stimulated, Geobacter species became the predominant organisms at all locations. Rates of U(VI) reduction appeared to be more related to the concentration of acetate that was delivered to each location rather than the amount of ammonium available in the groundwater. In situ mRNA transcript abundance of the nitrogen fixation gene, nifD, and the ammonium importer gene, amtB, in Geobacter species indicated that ammonium was the primary source of nitrogen during in situ uranium reduction, and that the abundance of amtB transcripts was inversely correlated to ammonium levels across all sites examined. These results suggest that nifD and amtB expression by subsurface Geobacter species are closely regulated in response to ammonium availability to ensure an adequate supply of nitrogen while conserving cell resources. Thus, quantifying nifD and amtB expression appears to be a useful approach for monitoring the nitrogen-related physiological status of Geobacter species in subsurface environments during bioremediation. This study also emphasizes the need for more detailed analysis of geochemical/physiological interactions at the field scale, in order to adequately model subsurface microbial processes.

  20. Dark CO/sub 2/ fixation in leaves of tomato plants grown with ammonium and nitrate as nitrogen sources

    Energy Technology Data Exchange (ETDEWEB)

    Ikeda, M; Yamada, Y [Kyushu Univ., Fukuoka (Japan). Dept. of Agricultural Chemistry

    1981-01-01

    The dark (non-photosynthetic) CO/sub 2/ fixation was studied in the leaves of ammonium-fed and nitrate-fed tomato plants. The ability to fix /sup 14/CO/sub 2/ in the dark of ammonium-fed plants was remarkably lower as compared with nitrate-fed plants, supporting the previous finding that the synthesis of C/sub 4/-compounds from C/sub 3/-compounds was reduced in the leaves of ammonium-fed plants. There was no difference in the activity of PEP carboxylase in extracts prepared from the leaves between both the plants during an early period of the treatment. However, the enzyme activity began to decrease rapidly in ammonium-fed plants 4 days after the treatment. By long-term treatments, the enzyme activity in ammonium-fed plants became half as high as that of nitrate-fed plants. The decreased PEP carboxylase activity in ammonium-fed plants was not associated with the presence of NH/sub 4/-N and the absence of NO/sub 3/-N in the leaf extract, and was not restored by the addition of the leaf extract from nitrate-fed plants. It is concluded that the decreased rate of synthesis of C/sub 4/-compounds from C/sub 3/-compounds in ammonium-fed plants is closely associated with a decrease in the dark fixation involving PEP carboxylase.

  1. Unicellular cyanobacteria with a new mode of life: the lack of photosynthetic oxygen evolution allows nitrogen fixation to proceed.

    Science.gov (United States)

    Bothe, Hermann; Tripp, H James; Zehr, Jonathan P

    2010-10-01

    Some unicellular N(2)-fixing cyanobacteria have recently been found to lack a functional photosystem II of photosynthesis. Such organisms, provisionally termed UCYN-A, of the oceanic picoplanktion are major contributors to the global marine N-input by N(2)-fixation. Since their photosystem II is inactive, they can perform N(2)-fixation during the day. UCYN-A organisms cannot be cultivated as yet. Their genomic analysis indicates that they lack genes coding for enzymes of the Calvin cycle, the tricarboxylic acid cycle and for the biosynthesis of several amino acids. The carbon source in the ocean that allows them to thrive in such high abundance has not been identified. Their genomic analysis implies that they metabolize organic carbon by a new mode of life. These unicellular N(2)-fixing cyanobacteria of the oceanic picoplankton are evolutionarily related to spheroid bodies present in diatoms of the family Epithemiaceae, such as Rhopalodia gibba. More recently, spheroid bodies were ultimately proven to be related to cyanobacteria and to express nitrogenase. They have been reported to be completely inactive in all photosynthetic reactions despite the presence of thylakoids. Sequence data show that R. gibba and its spheroid bodies are an evolutionarily young symbiosis that might serve as a model system to unravel early events in the evolution of chloroplasts. The cell metabolism of UCYN-A and the spheroid bodies may be related to that of the acetate photoassimilating green alga Chlamydobotrys.

  2. Dark CO2 fixation in leaves of tomato plants grown with ammonium and nitrate at nitrogen sources

    International Nuclear Information System (INIS)

    Ikeda, M.; Yamada, Y.

    1981-01-01

    The dark (non-photosynthetic) CO 2 fixation was studied in the leaves of ammonium-fed and nitrate-fed tomato plants. The ability to fix 14 CO 2 in the dark of ammonium-fed plants was remarkably lower as compared with nitrate-fed plants, supporting the previous finding that the synthesis of C 4 -compounds from C 3 -compounds was reduced in the leaves of ammonium-fed plants. There was no difference in the activity of PEP carboxylase in extracts prepared from the leaves between both the plants during an early period of the treatment. However, the enzyme activity began to decrease rapidly in ammonium-fed plants 4 days after the treatment. By long-term treatments, the enzyme activity in ammonium-fed plants became half as high as that of nitrate-fed plants. The decreased PEP carboxylase activity in ammonium-fed plants was not associated with the presence of NH 4 -N and the absence of NO 3 -N in the leaf extract, and was not restored by the addition of the leaf extract from nitrate-fed plants. It is concluded that the decreased rate of synthesis of C 4 -compounds from C 3 -compounds in ammonium-fed plants is closely associated with a decrease in the dark fixation involving PEP carboxylase. (orig.)

  3. Nitrogen fixation in seedlings of sabia and leucena grown in the caatinga soils under different vegetation covers

    International Nuclear Information System (INIS)

    Santana, Augusto Cesar de Arruda; Nascimento, Luciana Remigio Santos; Silva, Arthur Jorge da; Freitas, Ana Dolores Santiago de

    2013-01-01

    The aim of this study was to evaluate the efficiency differences of populations forming bacteria in legume nodules (BNL) in areas under different vegetation cover in semi-arid Pernambuco state, Brazil, using the methodology of the natural abundance of 15 N to estimate the amount of N fixed symbiotically. The highest levels of nitrogen was found in plants of leucena, and the sabia had levels that did not differ from reference species. The analysis by the technique of 15N showed that in all areas the leucena and the sabia showed signs of 15N different of the average signal of the control plants. The largest nitrogen accumulation was observed for leucena in the Caatinga and Capoeira. The sabia got greater accumulation of N from the Caatinga. The areas of Capoeira and Caatinga has showed the native populations of rhizobia with greater ability to fix nitrogen for the leucena

  4. Effects of seagulls on ecosystem respiration, soil nitrogen and vegetation cover on a pristine volcanic island, Surtsey, Iceland

    Science.gov (United States)

    Sigurdsson, B. D.; Magnusson, B.

    2010-03-01

    When Surtsey rose from the North Atlantic Ocean south of Iceland in 1963, it became a unique natural laboratory on how organisms colonize volcanic islands and form ecosystems with contrasting structures and functions. In July, 2004, ecosystem respiration rate (Re), soil properties and surface cover of vascular plants were measured in 21 permanent research plots distributed among the juvenile communities of the island. The plots were divided into two main groups, inside and outside a seagull (Larus spp.) colony established on the island. Vegetation cover of the plots was strongly related to the density of gull nests. Occurrence of nests and increased vegetation cover also coincided with significant increases in Re, soil carbon, nitrogen and C:N ratio, and with significant reductions in soil pH and soil temperatures. Temperature sensitivity (Q10 value) of Re was determined as 5.3. When compared at constant temperature the Re was found to be 59 times higher within the seagull colony, similar to the highest fluxes measured in drained wetlands or agricultural fields in Iceland. The amount of soil nitrogen, mainly brought onto the island by the seagulls, was the critical factor that most influenced ecosystem fluxes and vegetation development on Surtsey. The present study shows how ecosystem activity can be enhanced by colonization of animals that transfer resources from a nearby ecosystem.

  5. Effects of seagulls on ecosystem respiration, soil nitrogen and vegetation cover on a pristine volcanic island, Surtsey, Iceland

    Directory of Open Access Journals (Sweden)

    B. D. Sigurdsson

    2010-03-01

    Full Text Available When Surtsey rose from the North Atlantic Ocean south of Iceland in 1963, it became a unique natural laboratory on how organisms colonize volcanic islands and form ecosystems with contrasting structures and functions. In July, 2004, ecosystem respiration rate (Re, soil properties and surface cover of vascular plants were measured in 21 permanent research plots distributed among the juvenile communities of the island. The plots were divided into two main groups, inside and outside a seagull (Larus spp. colony established on the island. Vegetation cover of the plots was strongly related to the density of gull nests. Occurrence of nests and increased vegetation cover also coincided with significant increases in Re, soil carbon, nitrogen and C:N ratio, and with significant reductions in soil pH and soil temperatures. Temperature sensitivity (Q10 value of Re was determined as 5.3. When compared at constant temperature the Re was found to be 59 times higher within the seagull colony, similar to the highest fluxes measured in drained wetlands or agricultural fields in Iceland. The amount of soil nitrogen, mainly brought onto the island by the seagulls, was the critical factor that most influenced ecosystem fluxes and vegetation development on Surtsey. The present study shows how ecosystem activity can be enhanced by colonization of animals that transfer resources from a nearby ecosystem.

  6. Isotopic studies on nitrogen fixation and nitrogen cycling in blue-green algae and azolla. Final report for the period 1985-1989

    Energy Technology Data Exchange (ETDEWEB)

    Kauser, A M; Sikander, A [Nuclear Inst. for Agriculture and Biology, Faisalabad (Pakistan)

    1990-12-31

    Under the IAEA coordination project, a series of field and pot experiments have been conducted to demonstrate the various aspects of Azolla technology as a contribution of nitrogen to the nutrition of agricultural crops, especially rice. This final report summarizes the previous experiments and gives details on the last experiments. 1 fig., 7 tabs.

  7. Isotopic studies on nitrogen fixation and nitrogen cycling in blue-green algae and azolla. Final report for the period 1985-1989

    International Nuclear Information System (INIS)

    Kauser, A.M.; Sikander, A.

    1989-01-01

    Under the IAEA coordination project, a series of field and pot experiments have been conducted to demonstrate the various aspects of Azolla technology as a contribution of nitrogen to the nutrition of agricultural crops, especially rice. This final report summarizes the previous experiments and gives details on the last experiments. 1 fig., 7 tabs

  8. Effects of boron nutrition and water stress on nitrogen fixation, seed δ15N and δ13C dynamics, and seed composition in soybean cultivars differing in maturities.

    Science.gov (United States)

    Bellaloui, Nacer; Mengistu, Alemu

    2015-01-01

    Therefore, the objective of the current research was to investigate the effects of foliar B nutrition on seed protein, oil, fatty acids, and sugars under water stress conditions. A repeated greenhouse experiment was conducted using different maturity group (MG) cultivars. Plants were well-watered with no foliar B (W - B), well-watered with foliar B (W + B), water-stressed with no foliar B (WS - B), and water-stressed with foliar B (WS + B). Foliar B was applied at rate of 0.45 kg · ha(-1) and was applied twice at flowering and at seed-fill stages. The results showed that seed protein, sucrose, fructose, and glucose were higher in W + B treatment than in W - B, WS + B, and WS - B. The increase in protein in W + B resulted in lower seed oil, and the increase of oleic in WS - B or WS + B resulted in lower linolenic acid. Foliar B resulted in higher nitrogen fixation and water stress resulted in seed δ (15)N and δ (13)C alteration. Increased stachyose indicated possible physiological and metabolic changes in carbon and nitrogen pathways and their sources under water stress. This research is beneficial to growers for fertilizer management and seed quality and to breeders to use (15)N/(14)N and (13)C/(12)C ratios and stachyose to select for drought tolerance soybean.

  9. MtCAS31 Aids Symbiotic Nitrogen Fixation by Protecting the Leghemoglobin MtLb120-1 Under Drought Stress in Medicago truncatula

    Directory of Open Access Journals (Sweden)

    Xin Li

    2018-05-01

    Full Text Available Symbiotic nitrogen fixation (SNF in legume root nodules injects millions of tons of nitrogen into agricultural lands and provides ammonia to non-legume crops under N-deficient conditions. During plant growth and development, environmental stresses, such as drought, salt, cold, and heat stress are unavoidable. This raises an interesting question as to how the legumes cope with the environmental stress along with SNF. Under drought stress, dehydrin proteins are accumulated, which function as protein protector and osmotic substances. In this study, we found that the dehydrin MtCAS31 (cold-acclimation-specific 31 functions in SNF in Medicago truncatula during drought stress. We found that MtCAS31 is expressed in nodules and interacts with leghemoglobin MtLb120-1. The interaction between the two proteins protects MtLb120-1 from denaturation under thermal stress in vivo. Compared to wild type, cas31 mutants display a lower nitrogenase activity, a lower ATP/ADP ratio, higher expression of nodule senescence genes and higher accumulation of amyloplasts under dehydration conditions. The results suggested that MtCAS31 protects MtLb120-1 from the damage of drought stress. We identified a new function for dehydrins in SNF under drought stress, which enriches the understanding of the molecular mechanism of dehydrins.

  10. Effects of Boron Nutrition and Water Stress on Nitrogen Fixation, Seed δ15N and δ13C Dynamics, and Seed Composition in Soybean Cultivars Differing in Maturities

    Directory of Open Access Journals (Sweden)

    Nacer Bellaloui

    2015-01-01

    Full Text Available Therefore, the objective of the current research was to investigate the effects of foliar B nutrition on seed protein, oil, fatty acids, and sugars under water stress conditions. A repeated greenhouse experiment was conducted using different maturity group (MG cultivars. Plants were well-watered with no foliar B (W − B, well-watered with foliar B (W + B, water-stressed with no foliar B (WS − B, and water-stressed with foliar B (WS + B. Foliar B was applied at rate of 0.45 kg·ha−1 and was applied twice at flowering and at seed-fill stages. The results showed that seed protein, sucrose, fructose, and glucose were higher in W + B treatment than in W − B, WS + B, and WS − B. The increase in protein in W + B resulted in lower seed oil, and the increase of oleic in WS − B or WS + B resulted in lower linolenic acid. Foliar B resulted in higher nitrogen fixation and water stress resulted in seed δ15N and δ13C alteration. Increased stachyose indicated possible physiological and metabolic changes in carbon and nitrogen pathways and their sources under water stress. This research is beneficial to growers for fertilizer management and seed quality and to breeders to use 15N/14N and 13C/12C ratios and stachyose to select for drought tolerance soybean.

  11. The micro-RNA72c-APETALA2-1 node as a key regulator of the common bean-Rhizobium etli nitrogen fixation symbiosis.

    Science.gov (United States)

    Nova-Franco, Bárbara; Íñiguez, Luis P; Valdés-López, Oswaldo; Alvarado-Affantranger, Xochitl; Leija, Alfonso; Fuentes, Sara I; Ramírez, Mario; Paul, Sujay; Reyes, José L; Girard, Lourdes; Hernández, Georgina

    2015-05-01

    Micro-RNAs are recognized as important posttranscriptional regulators in plants. The relevance of micro-RNAs as regulators of the legume-rhizobia nitrogen-fixing symbiosis is emerging. The objective of this work was to functionally characterize the role of micro-RNA172 (miR172) and its conserved target APETALA2 (AP2) transcription factor in the common bean (Phaseolus vulgaris)-Rhizobium etli symbiosis. Our expression analysis revealed that mature miR172c increased upon rhizobial infection and continued increasing during nodule development, reaching its maximum in mature nodules and decaying in senescent nodules. The expression of AP2-1 target showed a negative correlation with miR172c expression. A drastic decrease in miR172c and high AP2-1 mRNA levels were observed in ineffective nodules. Phenotypic analysis of composite bean plants with transgenic roots overexpressing miR172c or a mutated AP2-1 insensitive to miR172c cleavage demonstrated the pivotal regulatory role of the miR172 node in the common bean-rhizobia symbiosis. Increased miR172 resulted in improved root growth, increased rhizobial infection, increased expression of early nodulation and autoregulation of nodulation genes, and improved nodulation and nitrogen fixation. In addition, these plants showed decreased sensitivity to nitrate inhibition of nodulation. Through transcriptome analysis, we identified 114 common bean genes that coexpressed with AP2-1 and proposed these as being targets for transcriptional activation by AP2-1. Several of these genes are related to nodule senescence, and we propose that they have to be silenced, through miR172c-induced AP2-1 cleavage, in active mature nodules. Our work sets the basis for exploring the miR172-mediated improvement of symbiotic nitrogen fixation in common bean, the most important grain legume for human consumption. © 2015 American Society of Plant Biologists. All Rights Reserved.

  12. [INFLUENCE OF AZOSPIRILLUM BRASILENSE 10/1 ON ASSOCIATIVE NITROGEN FIXATION AND INTRAVARIETAL POLYMORPHISM OF SPRING TRITICALE].

    Science.gov (United States)

    Patika, V P; Nadkernichna, O V; Shahovnina, O O

    2015-01-01

    It is shown, that the perspective Ukrainian sorts of spring triticale characterizes by considerable polymorphism by associative N2-fixing ability in root zone of plants. Application of active strain Azospirillum brasilense 10/1 promotes the decline of variability of this sign within the limits of sort, increase potential nitrogen activity is on the average in 3,2-4,7 times and also distributing normalizations in the selections of the inoculated plants.

  13. A Study on soybean cultivar and rhizobium strain interaction related to biological nitrogen fixation in different soils

    International Nuclear Information System (INIS)

    Pirvali Biranvand, N.

    1999-01-01

    Since, symbiotic effectiveness is affected by three important factors such as bacteria genotype, plant cultivar and environmental conditions (e.g. soil properties). In this research, simple and interaction effects of the first two factors about symbiosis of three soybean cultivar, which are most commonly cultivated soybean, with several commercial strain of bacteria with three different soils is investigated. For this purpose five Bradyrhizobium japonicum commercial strains (Rhizoking, Helinitro, Goldoat, Biodoz and CB 1809) were taken from soil and water rea search institute. Based on assurance of bacteria strains purity and ineffectiveness with cultivars, for comparison of strains symbiotic effectiveness with soybean cultivars and the best strain selection performed a factorial experiment with RCBD in 24 treatments and 4 replication. The seeds of soybean cultivars were cultivated in Growth chamber under Leonard jar system. The treatment used were 3 levels of soybean cultivar, 5 levels of Bradyrhizobium strains and 3 levels of Nitrogen (0, 35 and 70 PPM). Plants were fed with Brought on and Dil worth solution (1970) for 75 days. Then, plants were harvested and dried. Selective parameters were analysed by MSTATC program. The results indicated that, all bacteria stains were highly effective as far as symbiotic effectiveness is concerned. Eventually Rhizoking, Gold coat and Helinitro stains selected for soybean inoculation. Provided for pot culture, two soil samples from soybean original planting area (in the subregion of Gorgan and Sari cities) and another sample from Karaj countryside were taken with moderate, high and zero symbiont indigenous bacteria levels respectively. For study of interaction and simple effects of Bacteria strain and soybean cultivar in each soil; a factorial experiment with RCBD in 4 replication performed. Factors were contained soybean cultivar (three levels) and three Bacteria strain with a blank treatment for inoculation. In this respect

  14. Dependence of wheat and rice respiration on tissue nitrogen and the corresponding net carbon fixation efficiency under different rates of nitrogen application

    Science.gov (United States)

    Sun, Wenjuan; Huang, Yao; Chen, Shutao; Zou, Jianwen; Zheng, Xunhua

    2007-02-01

    To quantitatively address the role of tissue N in crop respiration under various agricultural practices, and to consequently evaluate the impact of synthetic fertilizer N application on biomass production and respiration, and hence net carbon fixation efficiency ( E ncf), pot and field experiments were carried out for an annual rotation of a rice-wheat cropping system from 2001 to 2003. The treatments of the pot experiments included fertilizer N application, sowing date and planting density. Different rates of N application were tested in the field experiments. Static opaque chambers were used for sampling the gas. The respiration as CO2 emission was detected by a gas chromatograph. A successive biomass clipping method was employed to determine the crop autotrophic respiration coefficient ( R a). Results from the pot experiments revealed a linear relationship between R a and tissue N content as R a = 4.74N-1.45 ( R 2 = 0.85, P < 0.001). Measurements and calculations from the field experiments indicated that fertilizer N application promoted not only biomass production but also increased the respiration of crops. A further investigation showed that the increase of carbon loss in terms of respiration owing to fertilizer N application exceeded that of net carbon gain in terms of aboveground biomass when fertilizer N was applied over a certain rate. Consequently, the E ncf declined as the N application rate increased.

  15. Efficient Visible Light Nitrogen Fixation with BiOBr Nanosheets of Oxygen Vacancies on the Exposed {001} Facets.

    Science.gov (United States)

    Li, Hao; Shang, Jian; Ai, Zhihui; Zhang, Lizhi

    2015-05-20

    Even though the well-established Haber-Bosch process has been the major artificial way to "fertilize" the earth, its energy-intensive nature has been motivating people to learn from nitrogenase, which can fix atmospheric N2 to NH3 in vivo under mild conditions with its precisely arranged proteins. Here we demonstrate that efficient fixation of N2 to NH3 can proceed under room temperature and atmospheric pressure in water using visible light illuminated BiOBr nanosheets of oxygen vacancies in the absence of any organic scavengers and precious-metal cocatalysts. The designed catalytic oxygen vacancies of BiOBr nanosheets on the exposed {001} facets, with the availability of localized electrons for π-back-donation, have the ability to activate the adsorbed N2, which can thus be efficiently reduced to NH3 by the interfacial electrons transferred from the excited BiOBr nanosheets. This study might open up a new vista to fix atmospheric N2 to NH3 through the less energy-demanding photochemical process.

  16. [Characteristics of 'salt island' and 'fertile island' for Tamarix chinensis and soil carbon, nitrogen and phosphorus ecological stoichiometry in saline-alkali land].

    Science.gov (United States)

    Zhang, Li-hua; Chen, Xiao-bing

    2015-03-01

    To clarify the nutrient characteristics of 'salt island' and 'fertile island' effects in saline-alkali soil, the native Tamarix chinensis of the Yellow River Delta (YRD) was selected to measure its soil pH, electrical conductivity (EC), organic carbon (SOC), total nitrogen (N), total phosphorus (P) and their stoichiometry characteristics at different soil depths. The results showed that soil pH and EC increased with the increasing soil depth. Soil EC and P in the 0-20 cm layer decreased and increased from canopied area to interspace, respectively. SOC, N, N/P and C/P in the 20-40 cm soil layer decreased, and C/N increased from the shrub center to interspace. SOC and N contents between island and interspace both decreased but P content decreased firstly and then increased with the increasing soil depth. Soil pH correlated positively with EC. In addition, pH and EC correlated negatively with C, N, P contents and their ecological stoichiometry.

  17. NifH and NifD phylogenies: an evolutionary basis for understanding nitrogen fixation capabilities of methanotrophic bacteria.

    Science.gov (United States)

    Dedysh, Svetlana N; Ricke, Peter; Liesack, Werner

    2004-05-01

    The ability to utilize dinitrogen as a nitrogen source is an important phenotypic trait in most currently known methanotrophic bacteria (MB). This trait is especially important for acidophilic MB, which inhabit acidic oligotrophic environments, highly depleted in available nitrogen compounds. Phylogenetically, acidophilic MB are most closely related to heterotrophic dinitrogen-fixing bacteria of the genus BEIJERINCKIA: To further explore the phylogenetic linkage between these metabolically different organisms, the sequences of nifH and nifD gene fragments from acidophilic MB of the genera Methylocella and Methylocapsa, and from representatives of Beijerinckia, were determined. For reference, nifH and nifD sequences were also obtained from some type II MB of the alphaproteobacterial Methylosinus/Methylocystis group and from gammaproteobacterial type I MB. The trees constructed for the inferred amino acid sequences of nifH and nifD were highly congruent. The phylogenetic relationships among MB in the NifH and NifD trees also agreed well with the corresponding 16S rRNA-based phylogeny, except for two distinctive features. First, different methods used for phylogenetic analysis grouped the NifH and NifD sequences of strains of the gammaproteobacterial MB Methylococcus capsulatus within a clade mainly characterized by Alphaproteobacteria, including acidophilic MB and type II MB of the Methylosinus/Methylocystis group. From this and other genomic data from Methylococcus capsulatus Bath, it is proposed that an ancient event of lateral gene transfer was responsible for this aberrant branching. Second, the identity values of NifH and NifD sequences between Methylocapsa acidiphila B2 and representatives of Beijerinckia were clearly higher (98.5 and 96.6 %, respectively) than would be expected from their 16S rRNA-based relationships. Possibly, these two bacteria originated from a common acidophilic dinitrogen-fixing ancestor, and were subject to similar evolutionary pressure

  18. Comparative nitrogen fixation, native arbuscular mycorrhiza formation and biomass production potentials of some grain legumes species grown in the field in the Guinea Savannah zone of Ghana

    International Nuclear Information System (INIS)

    Ahiabor, B.D.K.; Fosu, M.; Tibo, I.; Sumaila, I.

    2007-01-01

    An on-station trial was conducted in the experimental field of Savannah Agricultural Research Institute at Nyankpala in the Northern Region of Ghana to assess the nitrogen fixation, native arbuscular mycorrhizal formation and biomass production potentials of cowpea (Vigna unguiculata), devil-bean (Crotalaria retusa), Mucuna pruriens var. utilis (black and white types) and Canavalia ensiformis with maize (Dorke SR) as the reference crop using the total nitrogen difference (TND) method. Plants were fertilized with 40 kg P/ha and 30 kg K/ha at 2 weeks after planting and grown for 55 days after which they were harvested. The harvested biomass (separated into roots, stems and leaves) of each crop was oven-dried at 70 0 C for 48 h to a constant weight. Cowpea and devil-bean produced approximately 5 and 6 t/ha biomass whereas Mucuna and Canavalia yielded about 2 t/ha biomass each. Although cowpea had the least number of arbuscular mycorrhiza fungal (AMF) spores in its rhizosphere, its roots were the most heavily colonized (34%) and M. pruriens recording below 5% colonization. Apart from C. ensiformis, the test legumes derived over 50% of their total accumulated N from the atmosphere with cowpea being the most efficient (90% Ndfa). Both N and P accumulations were significantly higher in cowpea than the other legumes due to increased N concentration and dry matter accumulation, respectively. In all the legumes, there was a direct positive correlation between the extent of mycorrhiza formation, biological N fixation and total N uptake. It could, therefore, be concluded that the extensive mycorrhiza formation in cowpea and its high N 2 -fixing potential resulted in a high shoot N and P uptake leading to a comparatively better growth enhancement. Cowpea could, therefore, be the grain legume for consideration in the selection of a suitable legume pre-crop to cereals for the amelioration of the low fertility of the degraded soils of the Guinea savannah zone of Ghana, and also as

  19. Nitrogen

    Science.gov (United States)

    Apodaca, Lori E.

    2013-01-01

    The article presents an overview of the nitrogen chemical market as of July 2013, including the production of ammonia compounds. Industrial uses for ammonia include fertilizers, explosives, and plastics. Other topics include industrial capacity of U.S. ammonia producers CF Industries Holdings Inc., Koch Nitrogen Co., PCS Nitrogen, Inc., and Agrium Inc., the impact of natural gas prices on the nitrogen industry, and demand for corn crops for ethanol production.

  20. Role of biological nitrogen fixation in legume based cropping systems; a case study of West Africa farming systems

    International Nuclear Information System (INIS)

    Sanginga, N.

    2001-01-01

    Nitrogen (N) has been gradually depleted from West African soils and now poses serious threats to food production. Many ways of increasing N supply (e.g. judicious use of inorganic fertilizers and nitrogen-fixing plants) have been tried in West African farming systems. Herbaceous and woody legumes commonly contribute 40-70 kg N ha -l season. This represents about 30% of the total N applied as residues. Nevertheless and despite repeated demonstrations of the usefulness of green manures in enhancing soil fertility, their practices and adoption are still limited. Promiscuous soya beans are being used to develop sustainable cropping systems in the moist savannah. Reliable estimates of N 2 fixed by soya beans and their residual N benefits to subsequent cereal crops in the savannah zone of southern Guinea have only infrequently been made. The actual amounts measured varied between 38 and 126 kg N ha -l assuming that only seeds of soya beans are removed from the plots, the net N accrual of soil nitrogen ranges between minus 8 kg N ha -l and plus 47 kg N ha -l depending on the soyabean cultivar. Residual soyabean N values of 10-24 kg N ha -l (14-36% of the total N in maize) were obtained in a soyabean-maize rotation. Although cereal yields following legume cultivation have been attributed to greater N accumulation, our data show that the relative increase in maize N was smaller than the relative increase in dry-matter yield. Hence, the increased yields of maize following soy beans are not entirely due to the carry-over of N from soyabean residues (as well as to conservation of soil N) but to other rotational effects as well. It is thus clear that the N benefit of grain legumes to non-legumes is small compared to the level of N fertilizer use in more intensive cereal production systems but is nevertheless significant in the context of the low amounts of input in subsistence farming. (author)

  1. Effects of tillage and cropping systems on yield and nitrogen fixation of cowpea intercropped with maize in northen Guinea savanna zone of Ghana

    International Nuclear Information System (INIS)

    Kombiok, J.M.; Safo, E.Y; Quansah, C.

    2006-01-01

    Published information is scanty on the response of crops in mixed cropping systems to the various tillage systems practised by farmers in the northern savanna zone of Ghana. A field experiment assessed the yield and nitrogen (N) fixation of cowpea (Vigna unguiculata (L.) Walp) intercropped with maize (Zea mays L.) on four different tillage systems at Nyankpala in the Northern Region of Ghana. The experiment was laid in a split-plot design with four replications. The main factor was tillage systems comprising conventional (Con), bullock plough (BP), hand hoe (HH) and zero tillage (ZT). The sub-factor was cropping systems (CRPSYT) which consisted of sole maize, sole cowpea, maize/cowpea inter-row cropping system, and bare fallow in 2000. The last named was replaced by maize/cowpea intra-row cropping system in 2001. The results showed that Con and BP, which produced over 10 cm plough depth, significantly reduced soil bulk density that favoured significant (P I). The LERs ranged from 1.43 to 1.79 in 2000, and from 1.23 to 1.24 in 2001 for Con and ZT, respectively. These indicate 33 and 52 percent mean increases in productivity of cowpea and maize, respectively, over their pure stands across the 2 years. However, grain yields of both crops from the inter- and intra-row cropping systems were not different. (au)

  2. The involvement of the nif-associated ferredoxin-like genes fdxA and fdxN of Herbaspirillum seropedicae in nitrogen fixation.

    Science.gov (United States)

    Souza, André L F; Invitti, Adriana L; Rego, Fabiane G M; Monteiro, Rose A; Klassen, Giseli; Souza, Emanuel M; Chubatsu, Leda S; Pedrosa, Fábio O; Rigo, Liu U

    2010-02-01

    The pathway of electron transport to nitrogenase in the endophytic beta-Proteobacterium Herbaspirillum seropedicae has not been characterized. We have generated mutants in two nif-associated genes encoding putative ferredoxins, fdxA and fdxN. The fdxA gene is part of the operon nifHDKENXorf1orf2fdxAnifQmodABC and is transcribed from the nifH promoter, as revealed by lacZ gene fusion. The fdxN gene is probably cotranscribed with the nifB gene. Mutational analysis suggests that the FdxA protein is essential for maximum nitrogenase activity, since the nitrogenase activity of the fdxA mutant strain was reduced to about 30% of that of the wild-type strain. In addition, the fdxA mutation had no effect on the nitrogenase switch-off in response to ammonium. Nitrogenase activity of a mutant strain lacking the fdxN gene was completely abolished. This phenotype was reverted by complementation with fdxN expressed under lacZ promoter control. The results suggest that the products of both the fdxA and fdxN genes are probably involved in electron transfer during nitrogen fixation.

  3. The year-wise nodulation behavior and biological nitrogen fixation parameters of chickpea (cicer aritinum, L) at some selected sites in the southern zone of Pakistan during 1995-98

    International Nuclear Information System (INIS)

    Idris, M.

    2000-01-01

    Study was carried out during 1995-98 to know the location and year-wise nodulation response (number and weight of nodules/plant) and the related biological nitrogen fixation parameters (dry matter yield, n concentration and yield/plant) of the crop at some selected sites ( Peshawar, Kohat, Krak, Bannu and D. I. Khan ) under the agro climatic conditions prevailing in the southern zones of NWFP-Pakistan. The crop was found to be profusely nodulating under the agro climatic conditions prevailing at all sites except at Barani-Agricultural Research station (bars) Kohat, where the nodulation of the crop almost remained inclined to be nil. The nodulation behavior and biological nitrogen fixation parameters of chickpea during 1995-98 in the southern zone of NWFP- Pakistan has been described. (author)

  4. Evaluation of the biological nitrogen fixation (N2) contribution in several forage legumes and the transfer of N to associated grasses

    International Nuclear Information System (INIS)

    Vargas, M.S.V.

    1991-12-01

    The objective of experiment 1 was to compare two different techniques for labelling the soil mineral nitrogen with 15 N, for studies to quantify the contribution of biological nitrogen fixation (BNF) to forage legumes using the 15 N isotope dilution technique. The two techniques for labelling the soil were: incorporation a 15 N labelled organic compost (slow release treatment), and split applications of 15 N labelled ammonium sulphate. The evaluation of the techniques was through the quantification of BNF in the Itaguai Hybrid of Centrosema using two non-Na- fixing control plants (P. maximum K K-16 and Sorghum bicolor). The objective of experiment 2 was to quantify the contribution of BNF to forage legumes and the transfer of fixed nitrogen to associated grasses in mixed swards again using the 15 N isotope dilution technique. This study was conducted on a red podzolic soil (Typic Hapludult), with 7 forage legumes and 3 grasses in monoculture, and 3 mixed swards of Brachiaria brizantha with the Centrosema hybrid, Galactia striata and Desmodium ovalifolium, respectively, with varying ratios of grass to legume (4:1 to 1:4). In order to quantify the BNF contributions to the legumes and the transfer of fixed N to the B. brizantha, the plots were amended 8 times with doses of 0.01 g 15 N m -2 of 15 N labelled ammonium sulphate (12.5 atom % 15 N) each 14 days, giving a total of 0.08 g 15 N m -2 of 15 N during the 97 days of the experiment. In monoculture the different forage legumes obtained the equivalent of between 43 and 100 kg N ha -1 from BNF. Stylosanthes guianensis showed the greatest contributions from BNF at 100 Kg N ha -1 . In mixed swards with Brachiaria brizantha the proportion of N derived from BNF in the three legumes studied (Centrosema hybrid, G. striata and D. ovalifolium) was significantly greater than when they were grown in monoculture. (author). 197 refs, 9 figs, 19 tabs

  5. Bacteriohopanepolyols record stratification, nitrogen fixation and other biogeochemical perturbations in Holocene sediments of the central Baltic Sea

    Directory of Open Access Journals (Sweden)

    M. Blumenberg

    2013-04-01

    Full Text Available The Baltic Sea, one of the world's largest brackish-marine basins, established after deglaciation of Scandinavia about 17 000 to 15 000 yr ago. In the changeable history of the Baltic Sea, the initial freshwater system was connected to the North Sea about 8000 yr ago and the modern brackish-marine setting (Littorina Sea was established. Today, a relatively stable stratification has developed in the water column of the deep basins due to salinity differences. Stratification is only occasionally interrupted by mixing events, and it controls nutrient availability and growth of specifically adapted microorganisms and algae. We studied bacteriohopanepolyols (BHPs, lipids of specific bacterial groups, in a sediment core from the central Baltic Sea (Gotland Deep and found considerable differences between the distinct stages of the Baltic Sea's history. Some individual BHP structures indicate contributions from as yet unknown redoxcline-specific bacteria (bacteriohopanetetrol isomer, methanotrophic bacteria (35-aminobacteriohopanetetrol, cyanobacteria (bacteriohopanetetrol cyclitol ether isomer and from soil bacteria (adenosylhopane through allochthonous input after the Littorina transgression, whereas the origin of other BHPs in the core has still to be identified. Notably high BHP abundances were observed in the deposits of the brackish-marine Littorina phase, particularly in laminated sediment layers. Because these sediments record periods of stable water column stratification, bacteria specifically adapted to these conditions may account for the high portions of BHPs. An additional and/or accompanying source may be nitrogen-fixing (cyanobacteria, which is indicated by a positive correlation of BHP abundances with Corg and δ15N.

  6. COMPARISON OF GENKENSIA DEMISSA (DILLWYN) POPULATIONS IN RHODE ISLAND FRINGE MARSHES WITH VARYING NITROGEN LOADS

    Science.gov (United States)

    Increased residential development in coastal watersheds has led to increases in anthropogenic nitrogen inputs into estuaries. Sessile bivalves are good candidate organisms to examine animal condition in nutrient-enriched areas because they contribute significantly to energy flow...

  7. Regulators of nonsulfur purple phototrophic bacteria and the interactive control of CO2 assimilation, nitrogen fixation, hydrogen metabolism and energy generation.

    Science.gov (United States)

    Dubbs, James M; Tabita, F Robert

    2004-06-01

    For the metabolically diverse nonsulfur purple phototrophic bacteria, maintaining redox homeostasis requires balancing the activities of energy supplying and energy-utilizing pathways, often in the face of drastic changes in environmental conditions. These organisms, members of the class Alphaproteobacteria, primarily use CO2 as an electron sink to achieve redox homeostasis. After noting the consequences of inactivating the capacity for CO2 reduction through the Calvin-Benson-Bassham (CBB) pathway, it was shown that the molecular control of many additional important biological processes catalyzed by nonsulfur purple bacteria is linked to expression of the CBB genes. Several regulator proteins are involved, with the two component Reg/Prr regulatory system playing a major role in maintaining redox poise in these organisms. Reg/Prr was shown to be a global regulator involved in the coordinate control of a number of metabolic processes including CO2 assimilation, nitrogen fixation, hydrogen metabolism and energy-generation pathways. Accumulating evidence suggests that the Reg/Prr system senses the oxidation/reduction state of the cell by monitoring a signal associated with electron transport. The response regulator RegA/PrrA activates or represses gene expression through direct interaction with target gene promoters where it often works in concert with other regulators that can be either global or specific. For the key CO2 reduction pathway, which clearly triggers whether other redox balancing mechanisms are employed, the ability to activate or inactivate the specific regulator CbbR is of paramount importance. From these studies, it is apparent that a detailed understanding of how diverse regulatory elements integrate and control metabolism will eventually be achieved.

  8. Comparative Analysis of the Combined Effects of Different Water and Phosphate Levels on Growth and Biological Nitrogen Fixation of Nine Cowpea Varieties.

    Science.gov (United States)

    Jemo, Martin; Sulieman, Saad; Bekkaoui, Faouzi; Olomide, Oluwatosin A K; Hashem, Abeer; Abd Allah, Elsayed Fathi; Alqarawi, Abdulaziz A; Tran, Lam-Son Phan

    2017-01-01

    Water deficit and phosphate (Pi) deficiency adversely affect growth and biological nitrogen fixation (BNF) of legume crops. In this study, we examined the impact of interaction between soil water conditions and available soil-Pi levels on growth, nodule development and BNF potential of nine cowpea varieties grown on dry savanna soils. In our experimental design, soils with different available soil-Pi levels, i.e., low, moderate, and high soil-Pi levels, collected from various farming fields were used to grow nine cowpea varieties under well-watered and water-deficit conditions. Significant and severe water deficit-damaging effects on BNF, nodulation, growth, levels of plant-nitrogen (N) and -phosphorus (P), as well as shoot relative water content and chlorophyll content of cowpea plants were observed. Under well-watered and high available soil-Pi conditions, cowpea varieties IT07K-304-9 and Dan'Ila exhibited significantly higher BNF potential and dry biomass, as well as plant-N and -P contents compared with other tested ones. Significant genotypic variations among the cowpeas were recorded under low available soil-Pi and water-deficit conditions in terms of the BNF potential. Principal component (PC) analysis revealed that varieties IT04K-339-1, IT07K-188-49, IT07K-304-9, and IT04K-405-5 were associated with PC1, which was better explained by performance for nodulation, plant biomass, plant-N, plant-P, and BNF potential under the combined stress of water deficit and Pi deficiency, thereby offering prospects for development of varieties with high growth and BNF traits that are adaptive to such stress conditions in the region. On another hand, variety Dan'Ila was significantly related to PC2 that was highly explained by the plant shoot/root ratio and chlorophyll content, suggesting the existence of physiological and morphological adjustments to cope with water deficit and Pi deficiency for this particular variety. Additionally, increases in soil-Pi availability led

  9. Comparative Analysis of the Combined Effects of Different Water and Phosphate Levels on Growth and Biological Nitrogen Fixation of Nine Cowpea Varieties

    Science.gov (United States)

    Jemo, Martin; Sulieman, Saad; Bekkaoui, Faouzi; Olomide, Oluwatosin A. K.; Hashem, Abeer; Abd_Allah, Elsayed Fathi; Alqarawi, Abdulaziz A.; Tran, Lam-Son Phan

    2017-01-01

    Water deficit and phosphate (Pi) deficiency adversely affect growth and biological nitrogen fixation (BNF) of legume crops. In this study, we examined the impact of interaction between soil water conditions and available soil-Pi levels on growth, nodule development and BNF potential of nine cowpea varieties grown on dry savanna soils. In our experimental design, soils with different available soil-Pi levels, i.e., low, moderate, and high soil-Pi levels, collected from various farming fields were used to grow nine cowpea varieties under well-watered and water-deficit conditions. Significant and severe water deficit-damaging effects on BNF, nodulation, growth, levels of plant-nitrogen (N) and -phosphorus (P), as well as shoot relative water content and chlorophyll content of cowpea plants were observed. Under well-watered and high available soil-Pi conditions, cowpea varieties IT07K-304-9 and Dan'Ila exhibited significantly higher BNF potential and dry biomass, as well as plant-N and -P contents compared with other tested ones. Significant genotypic variations among the cowpeas were recorded under low available soil-Pi and water-deficit conditions in terms of the BNF potential. Principal component (PC) analysis revealed that varieties IT04K-339-1, IT07K-188-49, IT07K-304-9, and IT04K-405-5 were associated with PC1, which was better explained by performance for nodulation, plant biomass, plant-N, plant-P, and BNF potential under the combined stress of water deficit and Pi deficiency, thereby offering prospects for development of varieties with high growth and BNF traits that are adaptive to such stress conditions in the region. On another hand, variety Dan'Ila was significantly related to PC2 that was highly explained by the plant shoot/root ratio and chlorophyll content, suggesting the existence of physiological and morphological adjustments to cope with water deficit and Pi deficiency for this particular variety. Additionally, increases in soil-Pi availability led

  10. Comparative Analysis of the Combined Effects of Different Water and Phosphate Levels on Growth and Biological Nitrogen Fixation of Nine Cowpea Varieties

    Directory of Open Access Journals (Sweden)

    Martin Jemo

    2017-12-01

    Full Text Available Water deficit and phosphate (Pi deficiency adversely affect growth and biological nitrogen fixation (BNF of legume crops. In this study, we examined the impact of interaction between soil water conditions and available soil-Pi levels on growth, nodule development and BNF potential of nine cowpea varieties grown on dry savanna soils. In our experimental design, soils with different available soil-Pi levels, i.e., low, moderate, and high soil-Pi levels, collected from various farming fields were used to grow nine cowpea varieties under well-watered and water-deficit conditions. Significant and severe water deficit-damaging effects on BNF, nodulation, growth, levels of plant-nitrogen (N and -phosphorus (P, as well as shoot relative water content and chlorophyll content of cowpea plants were observed. Under well-watered and high available soil-Pi conditions, cowpea varieties IT07K-304-9 and Dan'Ila exhibited significantly higher BNF potential and dry biomass, as well as plant-N and -P contents compared with other tested ones. Significant genotypic variations among the cowpeas were recorded under low available soil-Pi and water-deficit conditions in terms of the BNF potential. Principal component (PC analysis revealed that varieties IT04K-339-1, IT07K-188-49, IT07K-304-9, and IT04K-405-5 were associated with PC1, which was better explained by performance for nodulation, plant biomass, plant-N, plant-P, and BNF potential under the combined stress of water deficit and Pi deficiency, thereby offering prospects for development of varieties with high growth and BNF traits that are adaptive to such stress conditions in the region. On another hand, variety Dan'Ila was significantly related to PC2 that was highly explained by the plant shoot/root ratio and chlorophyll content, suggesting the existence of physiological and morphological adjustments to cope with water deficit and Pi deficiency for this particular variety. Additionally, increases in soil

  11. Effect of 59Fe and 65Zn on plant weight and chemical composition of common bean (Phaseolus vulgaris L.) cv. carioca and on atmospheric nitrogen fixation in three soils

    International Nuclear Information System (INIS)

    Suhet, A.R.

    1976-09-01

    A study is made of the effects of iron and zinc on yield and chemical composition of common bean (phaseolus vulgaris L.) and on atmospheric nitrogen fixation in three soils, classified as Terra Roxa Estruturada (TRE), Latossol Vermelho Escuro (LVE) and Podzolico Vermelho Amarelo (PVA). The coefficient of utilization of these micronutrients by this crop and their distribution in the aerial part and in the roots were also assessed. There was no influence of treatments of iron and zinc on yield of aerial parts and also on the weight and number of modules. There was significative effect of treatments on nitrogen, potassium, calcium, magnesium and zinc contents in aerial parts and on nitrogen, calcium and zinc contents in the root. (A.R.) [pt

  12. Uptake rate of nitrogen from soil and fertilizer, and N derived from symbiotic fixation in cowpea (Vigna unguiculata (L.) Walp.) and common bean (Phaseolus vulgaris L.) determined using the 15N isotope

    International Nuclear Information System (INIS)

    Brito, Marciano de Medeiros Pereira; Muraoka, Takashi; Silva, Edson Cabral da

    2009-01-01

    Common bean (Phaseolus vulgaris L.) and cowpea (Vigna unguiculata (L.) Walp.) are among the main sources of plant protein for a large part of the world population, mainly that of low income, and nitrogen is the main constituent of these proteins. The objectives of this study were to evaluate, through the 15 N-dilution technique and using rice and non-nodulating soybean as control plants, the relative contributions of nitrogen sources (symbiotically fixed N, soil native N and fertilizer N) on the growth of common bean and cowpea and to compare the isotopic technique (ID) with the difference methods (DM) for the evaluation of symbiotic N 2 fixation. The study was carried out in a greenhouse of the Center for Nuclear Energy in Agriculture - CENA/USP, Sao Paulo State, Brazil, using 5 kg pots with a Typic Haplustox (Dystrophic Red-Yellow Latosol). The experiment was arranged in completely randomized blocks, with 16 treatments and three replications, in an 8 x 2 factorial design. The treatments were eight sampling times: 7, 24, 31, 38, 47, 58, 68 and 78 days after sowing (DAS) and two crops: common bean and cowpea. An N rate of 10 mg kg -1 soil was used, as urea, enriched with an excess of 10 % of 15 N atoms. Symbiotic N fixation supplied the bean and cowpea plants with the greatest amount of accumulated N, followed, in decreasing order, by soil and fertilizer. The highest rate of N symbiotic fixation was observed at the pre-flowering growth stage of the bean and cowpea plants. After the initial growth stage, 24 DAS, rice and non nodulating soybean were appropriate control plants to evaluate symbiotic N fixation. There was a good agreement between ID and DM, except in the initial growth stage of the crops. (author)

  13. Enzymology of biological nitrogen fixation

    Energy Technology Data Exchange (ETDEWEB)

    Burris, R.H.

    1992-01-01

    Two genes involved in the regulation of nitrogenase activity, draT and draG, were cloned and found to be contiguous on the Azospirillum brasilense chromosome. The nifH gene, encoding dinitrogenase reductase, is near to draT with an intervening gap of 1.9 kb. The organization of these genes in Azospirillum lipoferum and Rhodosprillum rubrum is similar, but nifH and draT are separated by only 400 bp in the organisms. A. brasilense draTG is very similar to draTG in R. rubrum with 91.8% similarity and 85.3% identity at the amino acid level. Apparently A. brasilense uses the normal ATG initiation codon for draT, and draG. The genes for A. brasilense were able to restore function to appropriate mutants of R. rubrum. The heterologous expression of A. brasilense draTG in R. rubrum was not fully normal, as it responded more slowly to darkness and more quickly to ammonia than wild type cells. Our mutational analysis of the draTG region of A. brasilense confirms the function of these genes in the regulation of nitrogenase activity, but it also revealed minor but demonstrable differences in the control systems of R. rubrum and A. brasilense.

  14. Nitrogen-isotope ratios of nitrate in ground water under fertilized fields, Long Island, New York

    Science.gov (United States)

    Flipse, W.J.; Bonner, F.T.

    1985-01-01

    Ground-water samples from two heavily fertilized sites in Suffolk County, New York, were collected through the 1978 growing season and analyzed for nitrate-N concentrations and nitrogen-isotope ratios. Six wells were at a potato farm; six were on a golf course. The purpose of this study was to determine whether the 15N/14N ratios (??15N values) of fertilizer are increased during transit from land surface to ground water to an extent which would preclude use of this ratio to distinguish agricultural from animal sources of nitrate in ground water. Ground water at both sites contained a greater proportion of 15N than the fertilizers being applied. At the potato farm, the average ??15N value of the fertilizers was 0.2???; the average ??15N value of the ground-water nitrate was 6.2???. At the golf course, the average ??15N value of the fertilizers was -5.9???, and that of ground-water nitrate was 6.5???. The higher ??15N values of ground-water nitrate are probably caused by isotopic fractionation during the volatile loss of ammonia from nitrogen applied in reduced forms (NH4+ and organic-N). The ??15N values of most ground-water samples from both areas were less than 10???, the upper limit of the range characteristic of agricultural sources of nitrate; these sources include both fertilizer nitrate and nitrate derived from increased mineralization of soil nitrogen through cultivation. Previous studies have shown that the ??15N values of nitrate derived from human or animal waste generally exceed 10???. The nitrogen-isotope ratios of fertilizer-derived nitrate were not altered to an extent that would make them indistinguishable from animal-waste-derived nitrates in ground water.Ground-water samples from two heavily fertilized sites in Suffolk County, New York, were collected through the 1978 growing season and analyzed for nitrate-N concentrations and nitrogen-isotope ratios. Six wells were at a potato farm; six were on a golf course. The purpose of this study was to

  15. Comparison of greenhouse gas emissions from rice paddy fields under different nitrogen fertilization loads in Chongming Island, Eastern China

    International Nuclear Information System (INIS)

    Zhang, Xianxian; Yin, Shan; Li, Yinsheng; Zhuang, Honglei; Li, Changsheng

    2014-01-01

    Rice is one of the major crops of southern China and Southeast Asia. Rice paddies are one of the largest agricultural greenhouse gas (GHG) sources in this region because of the application of large quantities of nitrogen (N) fertilizers to the plants. In particular, the production of methane (CH 4 ) is a concern. Investigating a reasonable amount of fertilizers to apply to plants is essential to maintaining high yields while reducing GHG emissions. In this study, three levels of fertilizer application [high (300 kg N/ha), moderate (210 kg N/ha), and low (150 kg N/ha)] were designed to examine the effects of variation in N fertilizer application rate on carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) emissions from the paddy fields in Chongming Island, Shanghai, China. The high level (300 kg N/ha) represented the typical practice adopted by the local farmers in the area. Maximum amounts of CH 4 and N 2 O fluxes were observed upon high-level fertilizer application in the plots. Cumulative N 2 O emissions of 23.09, 40.10, and 71.08 mg N 2 O/m 2 were observed over the growing season in 2011 under the low-, moderate-, and high-level applications plots, respectively. The field data also indicated that soil temperatures at 5 and 10 cm soil depths significantly affected soil respiration; the relationship between Rs and soil temperature in this study could be described by an exponential model. Our study showed that reducing the high rate of fertilizer application is a feasible way of attenuating the global-warming potential while maintaining the optimum yield for the studied paddy fields. - Highlights: • In Chongming Island, Shanghai, GHG emissions were measured under different nitrogen fertilizer rates from the paddy. • Low nitrogen fertilizer application reduced CH 4 and N 2 O emissions. • The study showed that 210 kg N/ha was the suitable fertilizer application rate

  16. Comparison of greenhouse gas emissions from rice paddy fields under different nitrogen fertilization loads in Chongming Island, Eastern China

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xianxian [School of Agriculture and Biology, Shanghai Jiao Tong University, Dongchuan Rd. 800, Shanghai 200240 (China); Research Centre for Low Carbon Agriculture, Shanghai Jiao Tong University, Dongchuan Rd. 800, Shanghai 200240 (China); Key Laboratory for Urban Agriculture (South), Ministry of Agriculture, PR China, Dongchuan Rd. 800, Shanghai 200240 (China); Yin, Shan, E-mail: yinshan@sjtu.edu.cn [School of Agriculture and Biology, Shanghai Jiao Tong University, Dongchuan Rd. 800, Shanghai 200240 (China); Research Centre for Low Carbon Agriculture, Shanghai Jiao Tong University, Dongchuan Rd. 800, Shanghai 200240 (China); Key Laboratory for Urban Agriculture (South), Ministry of Agriculture, PR China, Dongchuan Rd. 800, Shanghai 200240 (China); Li, Yinsheng [School of Agriculture and Biology, Shanghai Jiao Tong University, Dongchuan Rd. 800, Shanghai 200240 (China); Research Centre for Low Carbon Agriculture, Shanghai Jiao Tong University, Dongchuan Rd. 800, Shanghai 200240 (China); Zhuang, Honglei [School of Agriculture and Biology, Shanghai Jiao Tong University, Dongchuan Rd. 800, Shanghai 200240 (China); Research Centre for Low Carbon Agriculture, Shanghai Jiao Tong University, Dongchuan Rd. 800, Shanghai 200240 (China); Key Laboratory for Urban Agriculture (South), Ministry of Agriculture, PR China, Dongchuan Rd. 800, Shanghai 200240 (China); Li, Changsheng [School of Agriculture and Biology, Shanghai Jiao Tong University, Dongchuan Rd. 800, Shanghai 200240 (China); Research Centre for Low Carbon Agriculture, Shanghai Jiao Tong University, Dongchuan Rd. 800, Shanghai 200240 (China); Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Morse Hall, College Road, NH 03824-3525 (United States); and others

    2014-02-01

    Rice is one of the major crops of southern China and Southeast Asia. Rice paddies are one of the largest agricultural greenhouse gas (GHG) sources in this region because of the application of large quantities of nitrogen (N) fertilizers to the plants. In particular, the production of methane (CH{sub 4}) is a concern. Investigating a reasonable amount of fertilizers to apply to plants is essential to maintaining high yields while reducing GHG emissions. In this study, three levels of fertilizer application [high (300 kg N/ha), moderate (210 kg N/ha), and low (150 kg N/ha)] were designed to examine the effects of variation in N fertilizer application rate on carbon dioxide (CO{sub 2}), methane (CH{sub 4}), and nitrous oxide (N{sub 2}O) emissions from the paddy fields in Chongming Island, Shanghai, China. The high level (300 kg N/ha) represented the typical practice adopted by the local farmers in the area. Maximum amounts of CH{sub 4} and N{sub 2}O fluxes were observed upon high-level fertilizer application in the plots. Cumulative N{sub 2}O emissions of 23.09, 40.10, and 71.08 mg N{sub 2}O/m{sup 2} were observed over the growing season in 2011 under the low-, moderate-, and high-level applications plots, respectively. The field data also indicated that soil temperatures at 5 and 10 cm soil depths significantly affected soil respiration; the relationship between Rs and soil temperature in this study could be described by an exponential model. Our study showed that reducing the high rate of fertilizer application is a feasible way of attenuating the global-warming potential while maintaining the optimum yield for the studied paddy fields. - Highlights: • In Chongming Island, Shanghai, GHG emissions were measured under different nitrogen fertilizer rates from the paddy. • Low nitrogen fertilizer application reduced CH{sub 4} and N{sub 2}O emissions. • The study showed that 210 kg N/ha was the suitable fertilizer application rate.

  17. Effect of tillage and crop residues management on mungbean (vigna radiata (L.) wilczek) crop yield, nitrogen fixation and water use efficiency in rainfed areas

    International Nuclear Information System (INIS)

    Mohammad, W.; Shehzadi, S.; Shah, S.M.; Shah, Z.

    2010-01-01

    A field experiment was conducted to study the effect of crop residues and tillage practices on BNF, WUE and yield of mungbean (Vigna radiata (L.) Wilczek) under semi arid rainfed conditions at the Livestock Research Station, Surezai, Peshawar in North West Frontier Province (NWFP) of Pakistan. The experiment comprised of two tillage i) conventional tillage (T1) and ii) no-tillage (T0) and two residues i) wheat crop residues retained (+) and ii) wheat crop residues removed (-) treatments. Basal doses of N at the rate of 20: P at the rate of 60 kg ha-1 were applied to mungbean at sowing time in the form of urea and single super phosphate respectively. Labelled urea having 5% 15N atom excess was applied at the rate of 20 kg N ha-1 as aqueous solution in micro plots (1m2) in each treatment plot to assess BNF by mungbean. Similarly, maize and sorghum were grown as reference crops and were fertilized with 15N labelled urea as aqueous solution having 1% 15N atom excess at the rate of 90 kg N ha/sup -1/. The results obtained showed that mungbean yield (grain/straw) and WUE were improved in notillage treatment as compared to tillage treatment. Maximum mungbean grain yield (1224 kg ha/sup -1/) and WUE (6.61kg ha/sup -1 mm/sup -1/) were obtained in no-tillage (+ residues) treatment. The N concentration in mungbean straw and grain was not significantly influenced by tillage or crop residue treatments. The amount of fertilizer-N taken up by straw and grain of mungbean was higher under no-tillage with residues-retained treatment but the differences were not significant. The major proportion of N (60.03 to 76.51%) was derived by mungbean crop from atmospheric N2 fixation, the remaining (19.6 to 35.91%) was taken up from the soil and a small proportion (3.89 to 5.89%) was derived from the applied fertilizer in different treatments. The maximum amount of N fixed by mungbean (82.59 kg ha/sup -1/) was derived in no-tillage with wheat residue-retained treatment. By using sorghum as

  18. Nitrogen

    Science.gov (United States)

    Apodaca, L.E.

    2010-01-01

    Ammonia was produced by 13 companies at 23 plants in 16 states during 2009. Sixty percent of all U.S. ammonia production capacity was centered in Louisiana. Oklahoma and Texas because of those states' large reserves of natural gas, the dominant domestic feedstock. In 2009, U.S. producers operated at about 83 percent of their rated capacity (excluding plants that were idle for the entire year). Five companies — Koch Nitrogen Co.; Terra Industries Inc.; CF Industries Inc.; PCS Nitrogen Inc. and Agrium Inc., in descending order — accounted for 80 percent of the total U.S. ammonia production capacity. U.S. production was estimated to be 7.7 Mt (8.5 million st) of nitrogen (N) content in 2009 compared with 7.85 Mt (8.65 million st) of N content in 2008. Apparent consumption was estimated to have decreased to 12.1 Mt (13.3 million st) of N, a 10-percent decrease from 2008. The United States was the world's fourth-ranked ammonia producer and consumer following China, India and Russia. Urea, ammonium nitrate, ammonium phosphates, nitric acid and ammonium sulfate were the major derivatives of ammonia in the United States, in descending order of importance.

  19. The spatial variability of nitrogen and phosphorus concentration in a sand aquifer influenced by onsite sewage treatment and disposal systems: a case study on St. George Island, Florida.

    Science.gov (United States)

    Corbet, D Reide; Dillon, Kevin; Burnett, William; Schaefer, Geoff

    2002-01-01

    Groundwater from a shallow freshwater lens on St. George Island, a barrier island located in the Panhandle of Florida, eventually discharges into Apalachicola Bay or the Gulf of Mexico. Nutrient concentrations in groundwaters were monitored downfield from three onsite sewage treatment and disposal systems (OSTDS) on the island. Estimates of natural groundwater nutrient concentrations were obtained from an adjacent uninhabited island. Silicate, which was significantly higher in the imported drinking water relative to the surficial aquifer on St. George Island (12.2+/-1.9 mg Si l(-1) and 2.9+/-0.2 mg Si l(-1), respectively), was used as a natural conservative tracer. Our observations showed that nitrogen concentrations were attenuated to a greater extent than that of phosphorus relative to the conservative tracer. At the current setback distance (23 m), both nitrogen and phosphate concentrations are still elevated above natural levels by as much as 2 and 7 times, respectively. Increasing the setback distance to 50 m and raising the drainfields 1 m above the ground surface could reduce nutrient levels to natural concentrations (1.1+/-0.1 mg N l(-1), 0.20+/-0.02 mg P l(-1)).

  20. Submarine groundwater discharge driven nitrogen fluxes to Long Island Sound, NY: Terrestrial vs. marine sources

    Science.gov (United States)

    Tamborski, J. J.; Cochran, J. K.; Bokuniewicz, H. J.

    2017-12-01

    Bottom-waters in Smithtown Bay (Long Island Sound, NY) are subject to hypoxic conditions every summer despite limited nutrient inputs from waste-water and riverine sources, while modeling estimates of groundwater inputs are thought to be insignificant. Terrestrial and marine fluxes of submarine groundwater discharge (SGD) were quantified to Smithtown Bay using mass balances of 222Rn, 224Ra, 226Ra and 228Ra during the spring and summer of 2014/2015, in order to track this seasonal transition period. Intertidal pore waters from a coastal bluff (terrestrial SGD) and from a barrier beach (marine SGD) displayed substantial differences in N concentrations and sources, traced using a multi-isotope approach (222Rn, Ra, δ15N-NO3-, δ18O-NO3-). NO3- in terrestrial SGD did not display any seasonality and was derived from residential septic systems and fertilizer. Marine SGD N concentrations varied month-to-month because of mixing between oxic seawater and hypoxic saline pore waters; N concentrations were greatest during the summer, when NO3- was derived from the remineralization of organic matter. Short-lived 222Rn and 224Ra SGD fluxes were used to determine remineralized N loads along tidal recirculation flow paths, while long-lived 228Ra was used to trace inputs of anthropogenic N in terrestrial SGD. 228Ra-derived terrestrial N load estimates were between 20 and 55% lower than 224Ra-derived estimates (excluding spring 2014); 228Ra may be a more appropriate tracer of terrestrial SGD N loads. Terrestrial SGD NO3- (derived from 228Ra) to Smithtown Bay varied from (1.40-12.8) ∗ 106 mol N y-1, with comparable marine SGD NO3- fluxes of (1.70-6.79) ∗ 106 mol N y-1 derived from 222Rn and 224Ra. Remineralized N loads were greater during the summer compared with spring, and these may be an important driver toward the onset of seasonal hypoxic conditions in Smithtown Bay and western Long Island Sound. Seawater recirculation through the coastal aquifer can rival the N load from

  1. Accumulation of nitrogen and organic matter during primary succession of Leymus arenarius dunes on the volcanic island Surtsey, Iceland

    Science.gov (United States)

    Stefansdottir, G.; Aradottir, A. L.; Sigurdsson, B. D.

    2014-05-01

    The volcanic island of Surtsey has been a natural laboratory where the primary succession of flora and fauna has been monitored, since it emerged from the N-Atlantic Ocean in 1963. We quantified the accumulation rates of nitrogen (N) and soil organic matter (SOM) in a 37 year long chronosequence of Leymus arenarius dunes in order to illuminate the spatiotemporal patterns in their build-up in primary succession. The Leymus dune area, volume and height grew exponentially over time. Aboveground plant biomass, cover or number of shoots per unit area did not change significantly with time, but root biomass accumulated with time, giving a root-shoot ratio of 19. The dunes accumulated on average 6.6 kg N ha-1 year-1, which was 3.5 times more than is received annually by atmospheric deposition. The extensive root system of Leymus seems to effectively retain and accumulate large part of the annual N deposition, not only deposition directly on the dunes but also from the adjacent unvegetated areas. SOM per unit area increased exponentially with dune age, but the accumulation of roots, aboveground biomass and SOM was more strongly linked to soil N than time: 1 g m-2 increase in soil N led on the average to 6 kg C m-2 increase in biomass and SOM. The Leymus dunes, where most of the N has been accumulated, will therefore probably act as hot-spots for further primary succession of flora and fauna on the tephra sands of Surtsey.

  2. Marine subsidies of island communities in the Gulf of California: evidence from stable carbon and nitrogen isotopes

    International Nuclear Information System (INIS)

    Anderson, W.B.; Polis, G.A.

    1998-01-01

    Coastal sites support larger (2 to > 100 x) populations of many consumers than inland sites on islands in the Gulf of California. Previous data suggested that subsidies of energy and nutrients from the ocean allowed large coastal populations. Stable carbon and nitrogen isotopes are frequently used to analyse diet composition of organisms: they are particularly useful to distinguish between diet sources with distinct isotopic signatures, such as marine and terrestrial diets. We analyzed the 13 C and 15 N concentrations of coastal versus inland spiders and scorpions to test the hypothesis that coastal individuals exhibited more strongly marine-based diets than inland individuals. Coastal spiders and scorpions were significantly more enriched in 13 C and 15 N than inland spiders and scorpions, suggesting that the coastal individuals consumed more marine-based foods than their inland counterparts. These patterns existed in both drought years and wet El Nino years. However, the marine influence was stronger in drought years when terrestrial productivity was nearly non-existent, than in wet years when terrestrial productivity increased by an order of magnitude. (au)

  3. Natural abundances of 15Nitrogen and 13Carbon indicative of growth and N2 fixation in potassium fed lentil grown under water stress

    International Nuclear Information System (INIS)

    Kurdali, F.; Alshmmaa, M.

    2010-01-01

    Dual natural abundance analysis of 15 N and 13 C isotopes in lentil plants subjected to different soil moisture levels and rates of potassium fertilizer (K) were determined to assess crop performance variability in terms of growth and N 2 -fixation (Ndfa). δ 15 N values in lentils ranged from +0.67 to +1.36%; whereas, those of the N 2 -fixed and reference plant were -0.45 and +2.94%, respectively. Consequently, the Ndfa% ranged from 45 and 65% of total plant N uptake. Water stress reduced Δ 13 C values. However, K fertilization enhanced whole plant Δ 13 C along with dry matter yield and N 2 -fixation. The water stressed plants amended with K fertilizer seemed to be the best treatment because of its highest pod yield, high N balance and N 2 -fixation with low consumption of irrigation water. This illustrates the ecological and economical importance of K fertilizer in alleviating water stress occurring during the post-flowering period of lentil. (author)

  4. Overwinter changes in urea nitrogen:creatinine and cortisol:creatinine ratios in urine from Banks Island Peary caribou

    Directory of Open Access Journals (Sweden)

    Nicholas C. Larter

    2000-04-01

    Full Text Available Over 200 snow urine samples were collected from Banks Island Peary caribou between March 1993 and May 1998. Most (n = 146 samples were collected during 3 time periods in 5 successive years: early winter (3 November-3 December, mid-winter (9 February-1 March, and late-winter (23 April-2 May. We determined the ratios of urea nitrogen:creatinine (U:C and cortisol:creatinine (C:C for each sample. U:C ratios had significant year, time, and year x time interaction effects. Mid-winter ratios were higher than early or late-winter ratios. U:C ratios ranged from 0.53 to 19.05 mg/mg, and were lowest in 1997-98. Five calf caribou sacrificed in February 1994 had significantly (P<0.02 higher U:C ratios than other caribou in mid-winter. Three adult male and 2 calf caribou sacrificed in November 1993 had U:C ratios similar to other caribou in early winter. Sacrificed caribou were in similar condition to animals that have been harvested for subsistent use in other years, not overly fat nor in an advanced state of starvation. U:C ratios for Peary caribou range from 10 to ca. 100-fold higher than those reported for barren-ground caribou; ratios > 60-fold higher than those indicative of prolonged undernutrition in barren-ground caribou were common. This difference is likely because the winter diet of Peary caribou has a higher crude protein content than that of barren-ground caribou. C:C ratios had significant year and year x time interaction effects, and were highest in 1996-97 and 1997-98. C:C ratios of sacrificed caribou were similar to those of other animals during early and mid-winter. C:C ratios for Peary caribou ranged from 0.0120 ug/mg to 0.2678 ug/mg; ratios indicative of morbidity in mule deer were common. C:C and U:C ratios from the same individuals were not correlated (R = -0.073. Monitoring U:C ratios of Banks Island Peary caribou may provide useful management information.

  5. Symbiosis revisited : Phosphorus and acid buffering stimulate N2 fixation but not Sphagnum growth

    NARCIS (Netherlands)

    Van Den Elzen, Eva; Kox, Martine A R; Harpenslager, Sarah F.; Hensgens, Geert; Fritz, Christian; Jetten, Mike S M; Ettwig, Katharina F.; Lamers, Leon P M

    2017-01-01

    In pristine Sphagnum-dominated peatlands, (di)nitrogen (N2) fixing (diazotrophic) microbial communities associated with Sphagnum mosses contribute substantially to the total nitrogen input, increasing carbon sequestration. The rates of symbiotic nitrogen fixation reported for Sphagnum peatlands,

  6. Symbiotic nitrogen fixation and yield of Pachyrhizus Erosus (L) urban cultivars and Pachyrhizus Ahipa (WEDD) parodi landraces as affected by flower pruning

    DEFF Research Database (Denmark)

    Castellanos, J.Z.; Zapata, F.; Badillo, V.

    1997-01-01

    biomass without N fertiliser application. In some climatic regions P. erosus is reproductively pruned in order to obtain economic yields, but little is known about how the pruning influences the capacity of these tuber legumes to fix nitrogen. Two experiments were carried out to investigate the effect...

  7. Simple approach for the preparation of 15-15N2-enriched water for nitrogen fixation assessments: Evaluation, application and recommendations

    Directory of Open Access Journals (Sweden)

    Isabell eKlawonn

    2015-08-01

    Full Text Available Recent findings revealed that the commonly used 15N2 tracer assay for the determination of dinitrogen (N2 fixation can underestimate the activity of aquatic N2-fixing organisms. Therefore, a modification to the method using pre-prepared 15-15N2-enriched water was proposed. Here, we present a rigorous assessment and outline a simple procedure for the preparation of 15-15N2-enriched water. We recommend to fill sterile-filtered water into serum bottles and to add 15-15N2 gas to the water in amounts exceeding the standard N2 solubility, followed by vigorous agitation (vortex mixing ≥5 min. Optionally, water can be degassed at low-pressure (≥950 mbar for ten minutes prior to the 15-15N2 gas addition to indirectly facilitate the 15-15N2 dissolution. This preparation of 15-15N2-enriched water can be done within one hour using standard laboratory equipment. The final 15N-atom% excess was 5% after replacing 2–5% of the incubation volume with 15-15N2-enriched water. Notably, the addition of 15-15N2-enriched water can alter levels of trace elements in the incubation water due to the contact of 15-15N2-enriched water with glass, plastic and rubber ware during its preparation. In our tests, levels of trace elements (Fe, P, Mn, Mo, Cu, Zn increased by up to 0.1 nmol L-1 in the final incubation volume, which may bias rate measurements in regions where N2 fixation is limited by trace elements. For these regions, we tested an alternative way to enrich water with 15-15N2. The 15-15N2 was injected as a bubble directly to the incubation water, followed by gentle shaking. Immediately thereafter, the bubble was replaced with water to stop the 15-15N2 equilibration. This method achieved a 15N-atom excess of 6.6±1.7% when adding 2 mL 15-15N2 per liter of incubation water. The herein presented methodological tests offer guidelines for the 15N2 tracer assay and thus, are crucial to circumvent methodological draw-backs for future N2 fixation assessments.

  8. Elevated CO2 concentration around alfalfa nodules increases N2 fixation

    OpenAIRE

    Fischinger, Stephanie A.; Hristozkova, Marieta; Mainassara, Zaman-Allah; Schulze, Joachim

    2009-01-01

    Nodule CO2 fixation via PEPC provides malate for bacteroids and oxaloacetate for N assimilation. The process is therefore of central importance for efficient nitrogen fixation. Nodule CO2 fixation is known to depend on external CO2 concentration. The hypothesis of the present paper was that nitrogen fixation in alfalfa plants is enhanced when the nodules are exposed to elevated CO2 concentrations. Therefore nodulated plants of alfalfa were grown in a hydroponic system that allowed separate ae...

  9. Ecosystem respiration, vegetation development and soil nitrogen in relation to breeding density of seagulls on a pristine volcanic island, Surtsey, Iceland

    Science.gov (United States)

    Sigurdsson, B. D.; Magnusson, B.

    2009-08-01

    Since its birth in 1963 by volcanic eruption in the North Atlantic Ocean off Iceland, Surtsey has been a unique natural laboratory on how organisms colonize volcanic islands and form ecosystems with contrasting structure and function. In July, 2004, ecosystem respiration rate, soil properties and surface cover of vascular plants were measured on 21 plots distributed among the main plant communities found 40 years after the primary succession started. The plots could be divided into two groups, inside and outside seagull (Larus sp.) colonies found on the island. Vegetation cover of the plots was strongly related to the density of seagull nests within and around them. The occurrence of seagull nests and increased vegetation also coincided with significant increase in ecosystem respiration, soil carbon and nitrogen, and with significantly lower soil pH and soil temperatures. The ecosystem respiration was high inside the gull colonies, similar to the highest fluxes measured in drained wetlands or agricultural fields in Iceland. The most important factor for vegetation succession and ecosystem function on Surtsey seems to be the amount of nitrogen, which was mainly brought in by the seagulls.

  10. Adição de cromo hexavalente no crescimento, nodulação e absorção de nutrientes em soja Hexavalent chromium effects on soybeans growth, nitrogen fixation and nutrients absorption

    Directory of Open Access Journals (Sweden)

    Danilo Dufech Castilhos

    2001-12-01

    Full Text Available Foram avaliados os efeitos de doses crescentes de Cr6+ sobre a produção de matéria seca, absorção de nutrientes e fixação biológica de nitrogênio em plantas de soja. Antes da semeadura, as sementes foram tratadas com inóculo turfoso contendo Bradyrhizobium japonicum. As plantas foram cultivadas durante 40 dias em vasos "Leonard" que continha areia na parte superior e solução nutritiva sem nitrogênio na parte inferior. Os tratamentos constaram das seguintes doses de Cr6+ (K2Cr2O7 na solução nutritiva: 0, 5, 10, 20 e 40mg -1. Foi constatado que concentrações de Cr6+ maiores que 5mg -1 diminuíram a produção de matéria seca da parte aérea e radicular da soja, o número e peso de nódulos secos de Bradyrhizobium, como também a fixação biológica de nitrogênio e a absorção de P, K, Ca e Mg. Teores de Cr na parte aérea de plantas de soja superiores a 3,4mg Kg-1 podem ser considerados fitotóxicos.This study was carried out to evaluate the effect of hexavalent chromium on dry matter production, nutrient uptake and nitrogen fixation in soybeans (Glycine max The seeds were inoculated with comercial strains of Bradyrhizobium japonicum (SEMIA 587 and 5019 and the plants were grown in "Leonard Jars" containing washed sand in the upper portion and nutrient solution (without N in the lower. Five Cr6+ concentrations were used: 0, 5, 10, 20 e 40mg -1 in the nutrient solution. Concentrations of Cr6+ above 5mg -1 decreased plants and nodules dry matter production, number of nodules, nitrogen fixation and P, K, Ca e Mg uptake. Chromium concentrations in soybean tops above 3,4mg kg-1 were considered phytotoxic.

  11. Dinitrogen fixation by blue-green algae from paddy fields

    International Nuclear Information System (INIS)

    Thomas, Joseph

    1977-01-01

    Recent work using radioactive nitrogen on the blue-green algae of paddy fields has been reviewed. These algae fix dinitrogen and photoassimilate carbon evolving oxygen, thereby augmenting nitrogen and carbon status of the soil and also providing oxygen to the water-logged rice paddies. Further studies using radioactive isotopes 13 N, 24 Na and 22 Na on their nitrogen fixation, nitrogen assimilation pathways; regulation of nitrogenase, heterocysts production and sporulation and sodium transport and metabolism have been carried out and reported. The field application of blue green algae for N 2 fixation was found to increase the status of soil nitrogen and yield of paddy. (M.G.B.)

  12. Catalytic Proton Coupled Electron Transfer from Metal Hydrides to Titanocene Amides, Hydrazides and Imides: Determination of Thermodynamic Parameters Relevant to Nitrogen Fixation.

    Science.gov (United States)

    Pappas, Iraklis; Chirik, Paul J

    2016-10-03

    The hydrogenolysis of titanium-nitrogen bonds in a series of bis(cyclopentadienyl) titanium amides, hydrazides and imides by proton coupled electron transfer (PCET) is described. Twelve different N-H bond dissociation free energies (BDFEs) among the various nitrogen-containing ligands were measured or calculated, and effects of metal oxidation state and N-ligand substituent were determined. Two metal hydride complexes, (η 5 -C 5 Me 5 )(py-Ph)Rh-H (py-Ph = 2-pyridylphenyl, [Rh]-H) and (η 5 -C 5 R 5 )(CO) 3 Cr-H ([Cr] R -H, R= H, Me) were evaluated for formal H atom transfer reactivity and were selected due to their relatively weak M-H bond strengths yet ability to activate and cleave molecular hydrogen. Despite comparable M-H BDFEs, disparate reactivity between the two compounds was observed and was traced to the vastly different acidities of the M-H bonds and overall redox potentials of the molecules. With [Rh]-H, catalytic syntheses of ammonia, silylamine and N,N-dimethylhydrazine have been accomplished from the corresponding titanium(IV) complex using H 2 as the stoichiometric H atom source. The data presented in this study provides the thermochemical foundation for the synthesis of NH 3 by proton coupled electron transfer at a well-defined transition metal center.

  13. Fixação do nitrogênio do ar pelas bactérias que vivem em simbiose com as raízes da centrosema Fixation of the atmospheric nitrogen by bacteria which live symbiotically on centrosema

    Directory of Open Access Journals (Sweden)

    J. Casado Montojos

    1963-01-01

    Full Text Available Continuando a série de trabalhos sôbre a quantidade de nitrogênio atmosférico fixada por bactérias que vivem em simbiose com raízes de leguminosas, são relatados os resultados encontrados em centrosema (Centrosema pubescens Benth. Foram utilizados vasos de Mitscherlich, com terra-roxa-misturada. A colheita das plantas foi efetuada por ocasião do florescimento. A parte aérea foi pesada para cálculo da quantidade de massa verde produzida, e, em seguida, juntamente com as raízes, sêca a 60°C até pêso constante. Determinaram-se os teores de nitrogênio na parte aérea e subterrânea das plantas, assim como da terra dos vasos. Os resultados mostraram elevada capacidade de fixação simbiótica de nitrogênio pela centrosema correspondente a cêrca de 204 quilogramas de nitrogênio por hectare.Following a series of research work with the purpose of verifying the amount of atmospheric nitrogen fixed by symbiotic bacteria, the authors report in this paper the results on their research with the leguminous plant Centrosema pubescens Benth. This experiment was conducted in Mitscherlich pots containing terra-roxa-misturada obtained from a 20 cm deep layer of soil taken from the Central Experiment Station "Theodureto de Camargo", in Campinas. The plants were cut in the blooming period, as this is the proper season for turning over green manure crops. The aerial portion of the plants was weighed so as to determine the total production of green matter and then it was dried together with the roots at 60°C. Thus, nitrogen of the total plant was determined and the same analysis was done at the end of the experiment for the soil removed from the pots. According to the results of this experiment, it was found that 204 kilograms of nitrogen per hectare were fixed, showing therefore that centrosema has a high capacity of symbiotic nitrogen fixation.

  14. Environmental impacts of coastal fish farming; Carbon and Nitrogen budgets for trout farming in Kaldbacksfjord, Faroe Islands

    DEFF Research Database (Denmark)

    Nordi, Gunnvor A; Glud, Ronnie N.; Gaard, Eilif

    2011-01-01

    Flow of organic carbon (OC) and nitrogen through a sea cage trout farm was calculated on the basis of detailed studies of the farming operation, water circulation, OC and nutrient transport and recycling processes in sediment. A third of the OC and nitrogen provided by fish food was incorporated......% of nitrogen derived from fish food settled on the seabed, where it was either mineralized or accumulated in the sediment. Based on transect measurements of diagenetic activity, the farm footprint was found to cover an area similar to 10 times the farm area. OC mineralization in the sediment increased linearly...

  15. In-situ Monitoring of Plant-microbe Communication to Understand the Influence of Soil Properties on Symbiotic Biological Nitrogen Fixation

    Science.gov (United States)

    Webster, T.; Del Valle, I.; Cheng, H. Y.; Silberg, J. J.; Masiello, C. A.; Lehmann, J.

    2016-12-01

    Plant-microbe signaling is important for many symbiotic and pathogenic interactions. While this signaling often occurs in soils, very little research has evaluated the role that the soil mineral and organic matter matrix plays in plant-microbe communication. One hurdle to these studies is the lack of simple tools for evaluating how soil mineral phases and organic matter influence the availability of plant-produced flavonoids that initiate the symbiosis between nitrogen-fixing bacteria and legumes. Because of their range of hydrophobic and electrostatic properties, flavonoids represent an informative class of signaling molecules. In this presentation, we will describe studies examining the bioavailable concentrations of flavonoids in soils using traditional techniques, such as high-pressure liquid chromatography and fluorescent microbial biosensors. Additionally, we will describe our progress developing a Rhizobium leguminosarum reporter that can be deployed into soils to report on flavonoid levels. This new microbial reporter is designed so that Rhizobium only generates a volatile gas signal when it encounters a defined concentration of flavonoids. By monitoring the output of this biosensor using gas chromatography-mass spectrometry during real time during soil incubations, we are working to establish the impact of soil organic matter, pH, and mineral phases on the reception of these signaling molecules. We expect that the findings from these studies will be useful for recommending soil management strategies that can enhance the communication between legumes and nitrogen fixing bacteria. This research highlights the importance of studying the role of soil as a mediator of plant-microbe communication.

  16. Biological fixation and nitrogen transfer by three legume species in mango and soursop organic orchards;Fixacao biologica e transferencia de nitrogenio por leguminosas em pomar organico de mangueira e gravioleira

    Energy Technology Data Exchange (ETDEWEB)

    Paulino, Gleicia Miranda; Barroso, Deborah Guerra, E-mail: gleiciamiranda@yahoo.com.b, E-mail: deborah@uenf.b [Universidade Estadual do Norte Fluminense (UENF), Campos dos Goytacazes, RJ (Brazil). Dept. de Fitotecnia; Alves, Bruno Jose Rodrigues; Urquiaga, Segundo; Espindola, Jose Antonio Azevedo, E-mail: bruno@cnpab.embrapa.b, E-mail: urquiaga@cnpab.embrapa.b, E-mail: jose@cnpab.embrapa.b [EMBRAPA Agrobiologia, Seropedica, RJ (Brazil)

    2009-12-15

    The objective of this work was to evaluate the biological nitrogen fixation (BNF) and the N transfer derived from BNF of the legume species - Gliricidia sepium (gliricidia), Crotalaria juncea (sunnhemp) and Cajanus cajan (pigeon pea) - for an intercropped organic orchard with mango and soursop, through the {sup 15}N natural abundance method. The following inter cropping systems were evaluated: mango and soursop with gliricidia; mango and soursop with sunnhemp; mango and soursop with pigeon pea; and mango and soursop as control. Gliricidia showed the highest BNF potential (80%) , followed by sunnhemp (64.5%) and pigeon pea (45%). After two sunnhemp prunes, 149.5 kg ha{sup -1} of N per year were supplied, with 96.5 kg derived from BNF. After three annual prunes, gliricidia supplied 56.4 and 80.3 kg ha{sup -1} of N per year, with 45 and 64 kg derived from BNF, in two consecutive years. The quantity of N supplied to the system was higher than the mango and soursop requirements. Variations in the natural abundance of {sup 15}N were found only in soursop leaves. Gliricidia and sunnhemp were prominent in N transfer, with approximately 22.5 and 40% respectively. Green manuring using gliricidia permits fractioning of the N supply, which is an advantage in N obtention by the fruit trees (author)

  17. Nitrogenated compounds' biofiltration under alternative bacterium fixation substrates Biofiltración de compuestos nitrogenados bajo medios de fijación bacteriana alternativos

    Directory of Open Access Journals (Sweden)

    Carlos Carroza

    2012-09-01

    Full Text Available This study compares the behavior of nitrification (NH4+, NO2- and NO3-, and performance, in terms of the surface TAN conversion rate (STR, volumetric TAN conversion rate (VTR and removal percentage of TAN (PTR among three fixation media of nitrifying bacteria (two alternatives (S1, S2 and one commercial (Co. The experiment was performed in two tests of 42 days each. Three isolated biofiltration systems were built for the experience, to which were added media colonized by bacteria as a "seed" to start the process of nitrification. Ammonium chloride (NH4Cl was attached as source of ammonium in reconditioned freshwater, also gradually adding inorganic carbon (HCO3- to maintain moderate water hardness. The average results for both tests indicate that the substrates S1 and S2 show a statistically similar behavior to the substrate Co (P > 0.05 during the first 33 days (until steady state. For the second test in terms of performance, STR values were 0.40, 0.39, 0.39 g TAN m-2 d-1 recorded for S2 and Co respectively; in terms of PRN, values were 92(3 9־/ and 93% for S1, S2 and Co, respectively. Regarding VTR, values of 72.31, 114.94, and 39.02 g TAN m-3 d-1 were recorded for S2 and Co respectively. Statistical analysis provided that for STR and PRN, no significant differences, were found. But for VTR, statistically significant differences between means were evaluated, registering for the S2 media the highest value of VTR.Se compara el comportamiento del proceso de nitrificación (NH4+, NO2- y NO3-, y el rendimiento, en términos de la tasa superficial de conversión de NAT, tasa volumétrica de conversión de NAT y porcentaje de remoción de NAT (PRN entre tres medios de fijación de bacterias nitrificantes, dos alternativos (S1, S2 y uno comercial (Co. La experiencia se realizó en dos pruebas de 42 días cada una. Se construyeron tres sistemas aislados para la experiencia, a los cuales se adicionaron medios colonizados por bacterias a modo de

  18. Assessment of nitrogen and phosphorus flows in agricultural and urban systems in a small island under limited data availability

    NARCIS (Netherlands)

    Firmansyah, I.; Spiller, M.; Ruijter, De F.J.; Carsjens, G.J.; Zeeman, G.

    2017-01-01

    Nitrogen (N) and phosphorus (P) are two essential macronutrients required in agricultural production. The
    major share of this production relies on chemical fertilizer that requires energy and relies on limited resources
    (P). Since these nutrients are lost to the environment, there is a need

  19. CSF coccidioides complement fixation

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/003526.htm CSF coccidioides complement fixation test To use the sharing features on this page, please enable JavaScript. CSF coccidioides complement fixation is a test that checks ...

  20. Intrascleral IOL Fixation.

    Science.gov (United States)

    Jacob, Soosan

    2017-01-01

    Intrascleral sutureless intraocular lens (IOL) fixation utilizes direct haptic fixation within the sclera in eyes with deficient capsular support. This has advantages of long-term stability, good control of tilt and decentration, and lesser pseudophakodonesis. This review summarizes various techniques for intrascleral haptic fixation, results, complications, adaptations in special situations, modifications of the technique, combination surgeries, and intrascleral capsular bag fixation techniques (glued capsular hook). Copyright 2017 Asia-Pacific Academy of Ophthalmology.

  1. Dinitrogen fixation in aphotic oxygenated marine environments

    Directory of Open Access Journals (Sweden)

    Eyal eRahav

    2013-08-01

    Full Text Available We measured N2 fixation rates from oceanic zones that have traditionally been ignored as sources of biological N2 fixation; the aphotic, fully oxygenated, nitrate (NO3--rich, waters of the oligotrophic Levantine Basin (LB and the Gulf of Aqaba (GA. N2 fixation rates measured from pelagic aphotic waters to depths up to 720 m, during the mixed and stratified periods, ranged from 0.01 nmol N L-1 d-1 to 0.38 nmol N L-1 d-1. N2 fixation rates correlated significantly with bacterial productivity and heterotrophic diazotrophs were identified from aphotic as well as photic depths. Dissolved free amino acid amendments to whole water from the GA enhanced bacterial productivity by 2to 3.5 and N2 fixation rates by ~ 2 fold in samples collected from aphotic depths while in amendments to water from photic depths bacterial productivity increased 2 to 6 fold while N2 fixation rates increased by a factor of 2 to 4 illustrating that both BP an heterotrophic N2 fixation are carbon limited. Experimental manipulations of aphotic waters from the LB demonstrated a significant positive correlation between transparent exopolymeric particles (TEP concentration and N2 fixation rates. This suggests that sinking organic material and high carbon (C: nitrogen (N micro-environments (such as TEP-based aggregates or marine snow could support high heterotrophic N2 fixation rates in oxygenated surface waters and in the aphotic zones. Indeed, our calculations show that aphotic N2 fixation accounted for 37 to 75 % of the total daily integrated N2 fixation rates at both locations in the Mediterranean and Red Seas with rates equal or greater to those measured from the photic layers. Moreover, our results indicate that that while N2 fixation may be limited in the surface waters, aphotic, pelagic N2 fixation may contribute significantly to new N inputs in other oligotrophic basins, yet it is currently not included in regional or global N budgets.

  2. Symbiotic N fixation of several soybean varieties and mutants

    International Nuclear Information System (INIS)

    Soertini, G.; Hendratno

    1988-01-01

    Symbiotic N fixation of several soybean varieties and mutants. Research activities comprising of three experiments were carried out to screen several soybean varieties and mutants for symbiotic N fixation potential. The first two experiments involved screening of seven rhizobium strains/isolate for effective N fixation. Depending on the medium used, plant response to strains was different. In sterile medium, rhizobium strain USDA 136, 142 and TAL 102 showed a high nitrogen fixation potential. In soil only rhizobium strain USDA 110 had better performance and proved to be competitive to the native strains. Nitrogen-15 dilution method was used to screen nitrogen fixing ability of several soybean varieties and mutants. Guntur variety showed a better response to high dose of N fertilizer without disturbance in its fixing ability. This variety then was considered good to be introduced in the cropping system. (author). 8 refs

  3. Nitrogen fixation by groundnut and velvet bean and residual benefit to a subsequent maize crop Fixação de nitrogênio por amendoim e mucuna e benefício residual para uma cultura de milho

    Directory of Open Access Journals (Sweden)

    Ambate Okito

    2004-12-01

    Full Text Available Chemical fertilisers are rarely avaiable to poor farmers, for whom the nitrogen (N is often the most limiting element for cereal grain production. The objective of this study was to quantify the contribution of biological nitrogen fixation (BNF to groundnut (Arachis hypogaea and velvet bean (Mucuna pruriens crops using the 15N natural abundance (delta15N technique and to determine their residual effect and that of a natural fallow, on growth and N accumulation by two rustic maize varieties. The contribution of BNF calculated from delta15N data was 40.9, 59.6 and 30.9 kg ha-1, for groundnut, velvet bean and the natural fallow, respectively. The only legume grain harvested was from the groundnut, which yielded approximately 1.000 kg ha-1. The subsequent maize varieties ("Sol de Manhã" and "Caiana Sobralha" yielded between 1.958 and 2.971 kg ha-1, and were higher after velvet bean for both maize varieties and "Sol da Manhã" groundnut, followed by "Caiana" after groundnut and, finally, the natural fallow. For a small-holder producer the most attractive system is the groundnut followed by maize, as, in this treatment, both groundnut and maize grain harvest are possible. However, a simple N balance calculation indicated that the groundnut-maize sequence would, in the long term, deplete soil N reserves, while the velvet bean-maize sequence would lead to a build up of soil nitrogen.Fertilizantes químicos raramente estão disponíveis aos agricultores com poucos recursos econômicos, e assim o N é, freqüentemente, um elemento mais limitante para a produção de grãos. O objetivo deste trabalho foi quantificar a contribuição da fixação biológica de nitrogênio (FBN às culturas de amendoim (Arachis hypogaea e mucuna (Mucuna pruriens, por meio da técnica de abundância natural de 15N e determinar o efeito residual das leguminosas e do pousio sobre o crescimento e acumulação de N em duas variedades de milho. A contribuição da FBN calculada a

  4. Nitrogen on Mars: Insights from Curiosity

    Science.gov (United States)

    Stern, J. C.; Sutter, B.; Jackson, W. A.; Navarro-Gonzalez, Rafael; McKay, Chrisopher P.; Ming, W.; Archer, P. Douglas; Glavin, D. P.; Fairen, A. G.; Mahaffy, Paul R.

    2017-01-01

    Recent detection of nitrate on Mars indicates that nitrogen fixation processes occurred in early martian history. Data collected by the Sample Analysis at Mars (SAM) instrument on the Curiosity Rover can be integrated with Mars analog work in order to better understand the fixation and mobility of nitrogen on Mars, and thus its availability to putative biology. In particular, the relationship between nitrate and other soluble salts may help reveal the timing of nitrogen fixation and post-depositional behavior of nitrate on Mars. In addition, in situ measurements of nitrogen abundance and isotopic composition may be used to model atmospheric conditions on early Mars.

  5. Efficiency of nitrogen fertilizers for rice

    OpenAIRE

    Roger, Pierre-Armand; Grant, I.F.; Reddy, P.M.; Watanabe, I.

    1987-01-01

    The photosynthetic biomass that develops in the floodwater of wetland rice fields affects nitrogen dynamics in the ecosystem. This review summarizes available data on the nature, productivity, and composition of the photosynthetic aquatic biomass, and its major activities regarding the nitrogen cycle, i.e., nitrogen fixation by free living blue-green algae and #Azolla$, nitrogen trapping, nitrogen accumulation at the soil surface, its effect on nitrogen losses by ammonia volatilization, nitro...

  6. Nitrogen fixation in Red Sea seagrass meadows

    KAUST Repository

    Abdallah, Malak

    2017-01-01

    Seagrasses are key coastal ecosystems, providing many ecosystem services. Seagrasses increase biodiversity as they provide habitat for a large set of organisms. In addition, their structure provides hiding places to avoid predation. Seagrasses can

  7. Enzymology of biological nitrogen fixation. Annual report

    Energy Technology Data Exchange (ETDEWEB)

    Burris, R.H.

    1992-05-01

    Two genes involved in the regulation of nitrogenase activity, draT and draG, were cloned and found to be contiguous on the Azospirillum brasilense chromosome. The nifH gene, encoding dinitrogenase reductase, is near to draT with an intervening gap of 1.9 kb. The organization of these genes in Azospirillum lipoferum and Rhodosprillum rubrum is similar, but nifH and draT are separated by only 400 bp in the organisms. A. brasilense draTG is very similar to draTG in R. rubrum with 91.8% similarity and 85.3% identity at the amino acid level. Apparently A. brasilense uses the normal ATG initiation codon for draT, and draG. The genes for A. brasilense were able to restore function to appropriate mutants of R. rubrum. The heterologous expression of A. brasilense draTG in R. rubrum was not fully normal, as it responded more slowly to darkness and more quickly to ammonia than wild type cells. Our mutational analysis of the draTG region of A. brasilense confirms the function of these genes in the regulation of nitrogenase activity, but it also revealed minor but demonstrable differences in the control systems of R. rubrum and A. brasilense.

  8. Effects of elevated carbon dioxide concentration on growth and N2 fixation of young Robinia pseudoacacia

    International Nuclear Information System (INIS)

    Feng, Z; Flessa, H.; Dyckmans, J.

    2004-01-01

    The effects of elevated carbon dioxide concentration on carbon and nitrogen uptake and nitrogen source partitioning were determined in one year-old locust trees using a dual 13 C and 15 N continuous labelling experiment. Elevated carbon dioxide increased the fraction of new carbon in total carbon, but it did not alter carbon partitioning among plant compartments. Elevated carbon dioxide also increased the fraction of new nitrogen in total nitrogen. This was coupled with a shift in nitrogen source partitioning toward nitrogen fixation. Soil nitrogen uptake was not affected, but nitrogen fixation was markedly increased by elevated carbon dioxide treatment. The increased nitrogen fixation tended to decrease the C/N ratio in the presence of elevated carbon dioxide. Total dry mass of root nodules doubled in response to elevated carbon dioxide, however, this effect was not considered significant because of the great variability in root nodule formation. Overall, it was concluded that the growth of locust trees in an elevated carbon dioxide environment will not primarily be limited by nitrogen availability, giving the R. pseudoacacia species a competitive advantage over non-nitrogen-fixing tree species. It was also suggested that the increase in nitrogen fixation observed in response to elevated carbon dioxide treatment may play a key role in the growth response of forest ecosystems to elevated carbon dioxide by improving nitrogen availability for non-nitrogen-fixing trees. 51 refs., 1 tab., 4 figs

  9. Effects of seabird nitrogen input on biomass and carbon accumulation after 50 years of primary succession on a young volcanic island, Surtsey

    Science.gov (United States)

    Leblans, N. I. W.; Sigurdsson, B. D.; Roefs, P.; Thuys, R.; Magnússon, B.; Janssens, I. A.

    2014-11-01

    What happens during primary succession after the first colonizers have occupied a pristine surface largely depends on how they ameliorate living conditions for other species. For vascular plants the onset of soil development and associated increase in nutrient (mainly nitrogen; N) and water availability is especially important. Here, we report the relationship between N accumulation and biomass and ecosystem carbon (C) stocks in a 50-year-old volcanic island, Surtsey, Iceland, where N stocks are still exceptionally low. However, a 28-year-old seagull colony on the island provided nutrient-enriched areas, which enabled us to assess the relationship between N stock and biomass and ecosystem C stocks across a much larger range in N stock. Further, we compared areas on shallow and deep tephra sands as we expected that deep-rooted systems would be more efficient in retaining N. The sparsely vegetated area outside the colony had accumulated 0.7 kg N ha-1 yr-1, which was ca. 50-60% of the estimated N input rate from wet deposition. This approximates values for systems under low N input and bare dune habitats. The seagulls have added, on average, 47 kg N ha-1 yr-1, which induced a shift from belowground to aboveground in ecosystem N and C stocks and doubled the ecosystem N-use efficiency, determined as the ratio of biomass and C storage per unit N input. Soil depth did not significantly affect total N stocks, which suggests a high N retention potential. Both total ecosystem biomass and C stocks were strongly correlated with N stock inside the colony, which indicated the important role of N during the first steps of primary succession. Inside the colony, the ecosystem biomass C stocks (17-27 ton C ha-1) had reached normal values for grasslands, while the soil organic carbon (SOC) stocks (4-10 ton C ha-1 were only a fraction of normal grassland values. Thus, it will take a long time until the SOC stock reaches equilibrium with the current primary production, during which

  10. Guide to radiation fixatives

    International Nuclear Information System (INIS)

    Tawil, J.J.; Bold, F.C.

    1983-11-01

    This report identifies and then characterizes a variety of substances available in the market place for potential effectiveness as a fixative on radiologically contaminated surfaces. The substances include both generic chemicals and proprietary products. In selecting a fixative for a particular application, several attributes of the fixative may be relevant to the choice. These attributes include: toxicity, durability, and cleanliness and removability. In addition to the attributes of the fixative, one should also take into account certain characteristics of the site to be treated. These characteristics relate to climate, nature of the surface, use to which the treated surface will be put, subsequent cleanup operations, and type of neighboring surfaces. Finally, costs and potential environmental effects may influence the decision. A variety of fixatives are evaluated with respect to these various attributes and summarized in a reference table

  11. Nitrogen fixation in soybean treated with nitrogen dioxide and molybdenum

    International Nuclear Information System (INIS)

    Gupta, G.; Narayanan, R.

    1992-01-01

    Soybean plants were treated with Mo (0.0 or 2.0 mg kg -1 , soil dry wt.) and exposed to NO 2 (0.0, 0.05, or 0.1 μmol mol -1 ) at flowering stage. Specific root nodule activity (SNA), chlorophyll-a (Ch-a), chlorophyll-b (Ch-b), leaf N, number of pods, seeds per pod, weight of seeds, and shoot dry weight were measured. Compared with control, SNA did not change on the addition of 2 mg Mo to the soil, but increased by 65% on exposure to 0.1 μmol -1 NO 2 and by 106% on treatment with both NO 2 and Mo. Both Ch-a and Ch-b increased significantly on exposure to 0.1 μmol -1 NO 2 and 2 mg MO was almost the same as with 0.1 μmol mol -1 NO 2 alone. Leaf-N increased by 46% on exposure to NO 2 but did not change on the addition of Mo. Pod number, seed number and weight, and shoot dry weights showed significantly higher values on exposure to 0.1 μmol mol -1 NO 2 and 2 mg Mo

  12. [Assimilation of biological nitrogen by European beaver].

    Science.gov (United States)

    Vecherskiĭ, M V; Naumova, E I; Kostina, N V; Umarov, M M

    2009-01-01

    Nitrogenase activity, the abundance of diazotrophic bacteria, the structure and functional characteristics of the complex of microorganisms, and the content of nitrogen and carbon were determined in the contents of the gastrointestinal tract of the European beaver. A high nitrogen-fixing activity in the large intestine correlated with an increase in nitrogen content in the chyme upon its transfer over the gastrointestinal tract. It is assumed that microbial nitrogen fixation plays a major role in nitrogen nutrition of the European beaver.

  13. CO2 fixation by coral reefs. Sangosho ni yoru nisanka tanso no kotei

    Energy Technology Data Exchange (ETDEWEB)

    Kayane, H [Geological Survey of Japan, Tsukuba (Japan)

    1993-05-01

    In order for a coral reef to be a CO2 absorbing source, a condition would have to be satisfied that, with respect to production of organic carbon through photosynthesis, a total production by coral reef organism association is large, and the ratio of the total production to a total consumption is more than one. A requirement that the ratio of inorganic carbon production through calcification be 1.5 or more must also be met. Measurements have been carried out at coral fields off the Ishigaki Island by the Geological Research Center. The measurement results revealed that production is high for both of organic carbon and inorganic carbon, surplus organic carbon is produced, and CO2 is absorbed into the coral reefs. It was also found by measuring the stable isotope ratio of nitrogen in coral reef organisms that nitrogen required for the production in the coral reefs is supplied from the atmosphere through nitrogen fixation. The paper adds a description that CaCO3 deposition in the coral reefs has peaked in 5000 years to 6000 years ago, and it is in a ceiling-hit condition now. 25 refs., 3 figs.

  14. Symbiosis revisited: phosphorus and acid buffering stimulate N2 fixation but not Sphagnum growth

    Science.gov (United States)

    van den Elzen, Eva; Kox, Martine A. R.; Harpenslager, Sarah F.; Hensgens, Geert; Fritz, Christian; Jetten, Mike S. M.; Ettwig, Katharina F.; Lamers, Leon P. M.

    2017-03-01

    In pristine Sphagnum-dominated peatlands, (di)nitrogen (N2) fixing (diazotrophic) microbial communities associated with Sphagnum mosses contribute substantially to the total nitrogen input, increasing carbon sequestration. The rates of symbiotic nitrogen fixation reported for Sphagnum peatlands, are, however, highly variable, and experimental work on regulating factors that can mechanistically explain this variation is largely lacking. For two common fen species (Sphagnum palustre and S. squarrosum) from a high nitrogen deposition area (25 kg N ha-1 yr-1), we found that diazotrophic activity (as measured by 15 - 15N2 labeling) was still present at a rate of 40 nmol N gDW-1 h-1. This was surprising, given that nitrogen fixation is a costly process. We tested the effects of phosphorus availability and buffering capacity by bicarbonate-rich water, mimicking a field situation in fens with stronger groundwater or surface water influence, as potential regulators of nitrogen fixation rates and Sphagnum performance. We expected that the addition of phosphorus, being a limiting nutrient, would stimulate both diazotrophic activity and Sphagnum growth. We indeed found that nitrogen fixation rates were doubled. Plant performance, in contrast, did not increase. Raised bicarbonate levels also enhanced nitrogen fixation, but had a strong negative impact on Sphagnum performance. These results explain the higher nitrogen fixation rates reported for minerotrophic and more nutrient-rich peatlands. In addition, nitrogen fixation was found to strongly depend on light, with rates 10 times higher in light conditions suggesting high reliance on phototrophic organisms for carbon. The contrasting effects of phosphorus and bicarbonate on Sphagnum spp. and their diazotrophic communities reveal strong differences in the optimal niche for both partners with respect to conditions and resources. This suggests a trade-off for the symbiosis of nitrogen fixing microorganisms with their Sphagnum

  15. The nitrogen cycle.

    Science.gov (United States)

    Stein, Lisa Y; Klotz, Martin G

    2016-02-08

    Nitrogen is the fourth most abundant element in cellular biomass, and it comprises the majority of Earth's atmosphere. The interchange between inert dinitrogen gas (N2) in the extant atmosphere and 'reactive nitrogen' (those nitrogen compounds that support, or are products of, cellular metabolism and growth) is entirely controlled by microbial activities. This was not the case, however, in the primordial atmosphere, when abiotic reactions likely played a significant role in the inter-transformation of nitrogen oxides. Although such abiotic reactions are still important, the extant nitrogen cycle is driven by reductive fixation of dinitrogen and an enzyme inventory that facilitates dinitrogen-producing reactions. Prior to the advent of the Haber-Bosch process (the industrial fixation of N2 into ammonia, NH3) in 1909, nearly all of the reactive nitrogen in the biosphere was generated and recycled by microorganisms. Although the Haber-Bosch process more than quadrupled the productivity of agricultural crops, chemical fertilizers and other anthropogenic sources of fixed nitrogen now far exceed natural contributions, leading to unprecedented environmental degradation. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. N2 Fixation by Grain Legume Varieties as Affected By Rhizobia ...

    African Journals Online (AJOL)

    acer

    [*Author of Correspondence: hyakubu2009@g-mail.com]. 229. ABSTRACT: ... Yusuf et al, (2006) reported that cowpea fixed. 16-34kgN/ha and ... fixation of legume crops (Michiels et al.,. 1994). ..... Robert, M.B. (1995). ... nitrogen fixation), John.

  17. Biological oceanography, biogeochemical cycles, and pelagic ecosystem functioning of the east-central South Pacific Gyre: focus on Easter Island and Salas y Gómez Island

    Directory of Open Access Journals (Sweden)

    Peter von Dassow

    2014-10-01

    Full Text Available The Exclusive Economic Zone of Chile defined by Easter Island and Salas y Gómez Island is in the South Pacific Sub-tropical Gyre (SPSG, putting it at the center of the most oligotrophic and biomass poor waters in the world. Only 10 biological oceanographic expeditions have entered this zone in 105 years (19052010. We review key aspects of the plankton ecosystem and biogeochemical function relevant for the understanding of and conservation planning for marine environments. Plankton production is limited by lack of dissolved inorganic fixed nitrogen, not phosphorous. Higher organic nitrogen levels might be biologically unavailable. Short-term experiments suggested iron is not limiting, yet iron still likely limits nitrogen fixation, and thus production, at longer time scales, as the presence of nitrogen-fixers is exceptionally low compared to other ocean gyres. Plankton function is dominated by the smallest unicellular organisms, picoplankton (<3 μm in diameter. The SPSG represents a center of high biodiversity for picoplankton, as well as heterotrophic organisms such as tinntinids, siphonophores, and possibly amphipods, although data for key zooplankton, such as copepods, are lacking. Many groups exhibit negative relationships between diversity and total plankton biomass. High diversity might result from dispersal from a very large metacommunity and minimal competition within functional groups. Whether an island-mass effect causes a real or apparent increase in plankton biomass around Easter Island must be confirmed by high-resolution sampling in situ. Long-term threats to the planktonic ecosystem may include climate change-enhanced ocean stratification and plastic marine debris accumulation. Finally, priorities for future research are highlighted.

  18. N-2 fixation by non-heterocystous cyanobacteria

    NARCIS (Netherlands)

    Bergman, B.; Gallon, J.R.; Rai, A.N.; Stal, L.J.

    1997-01-01

    Many, though not all, non-heterocystous cyanobacteria can fix N-2. However, very few strains can fix N-2 aerobically. Nevertheless, these organisms may make a substantial contribution to the global nitrogen cycle. In this general review, N-2 fixation by laboratory cultures and natural populations of

  19. Flexible fixation and fracture healing

    DEFF Research Database (Denmark)

    Schmal, Hagen; Strohm, Peter C; Jaeger, Martin

    2011-01-01

    , noncomminuted fractures. External fixation uses external bars for stabilization, whereas internal fixation is realized by subcutaneous placement of locking plates. Both of these "biologic" osteosynthesis methods allow a minimally invasive approach and do not compromise fracture hematoma and periosteal blood...

  20. Nitrogen fixation in seedlings of sabia and leucena grown in the caatinga soils under different vegetation covers; Fixacao de nitrogenio em mudas de sabia e leucena cultivadas em solos da caatinga sob diferentes coberturas vegetais

    Energy Technology Data Exchange (ETDEWEB)

    Santana, Augusto Cesar de Arruda; Nascimento, Luciana Remigio Santos; Silva, Arthur Jorge da; Freitas, Ana Dolores Santiago de, E-mail: augusto.arruda26@yahoo.com.br, E-mail: lucaremigio@yahoo.com.br, E-mail: arthur.floresta.jorge@gmail.com, E-mail: ana.freitas@depa.ufrpe.br [Universidade Federal Rural de Pernambuco (UFRPE), Recife, PE (Brazil). Departamento de Agronomia

    2013-07-01

    The aim of this study was to evaluate the efficiency differences of populations forming bacteria in legume nodules (BNL) in areas under different vegetation cover in semi-arid Pernambuco state, Brazil, using the methodology of the natural abundance of {sup 15}N to estimate the amount of N fixed symbiotically. The highest levels of nitrogen was found in plants of leucena, and the sabia had levels that did not differ from reference species. The analysis by the technique of 15N showed that in all areas the leucena and the sabia showed signs of 15N different of the average signal of the control plants. The largest nitrogen accumulation was observed for leucena in the Caatinga and Capoeira. The sabia got greater accumulation of N from the Caatinga. The areas of Capoeira and Caatinga has showed the native populations of rhizobia with greater ability to fix nitrogen for the leucena.

  1. Sacroiliac Screw Fixation

    NARCIS (Netherlands)

    E.W. van den Bosch

    2003-01-01

    textabstractThe aim of this thesis is to evaluate three major aspects of the use of sacroiliac screws in patients with unstable pelvic ring fractures: the optimal technique for sacroiliac screw fixation, the reliability of peroperative fluoroscopy and the late results. We focused on the questions

  2. Effect of phosphorus level on nitrogen accumulation and yield in soybean

    International Nuclear Information System (INIS)

    You Yubo; Wu Dongmei; Gong Zhenping; Ma Chunmei

    2012-01-01

    In this paper, the 15 N labeling with sand culture was conducted to study effects of phosphorus level on nitrogen accumulation, nodule nitrogen fixation and yield of soybean plants. Results showed that nitrogen accumulation, fixation and yield of soybean plants all presented a single peak curve with improvement of phosphorus nutrition level, with the peak value of phosphorus concentration in nutrient solution of 31 mg/L. When phosphorus concentration of nutrient solution was 11 mg/L, no obvious promotion was found on the ratio of nodule nitrogen fixation when increasing phosphorus concentration again, However, when phosphorus concentration of nutrient solution was 21 mg/L, increasing phosphorus concentration again had no obvious promotion on soybean plant nitrogen accumulation, nodule nitrogen fixation accumulation and yield, indicating that effect of phosphorus nutrition level on nitrogen fixation was lower than that on yield formation level. (authors)

  3. Uptake rate of nitrogen from soil and fertilizer, and N derived from symbiotic fixation in cowpea (Vigna unguiculata (L.) Walp.) and common bean (Phaseolus vulgaris L.) determined using the {sup 15}N isotope; Marcha de absorcao do nitrogenio do solo, do fertilizante e da fixacao simbiotica em feijao-caupi (Vigna unguiculata (L.) Walp.) e feijao-comum (Phaseolus vulgaris L.) determinada com uso de {sup 15}N

    Energy Technology Data Exchange (ETDEWEB)

    Brito, Marciano de Medeiros Pereira; Muraoka, Takashi; Silva, Edson Cabral da [Centro de Energia Nuclear na Agricultura (CENA/USP), Piracicaba SP (Brazil)], e-mail: marcianobrito@hotmail.com, e-mail: muraoka@cena.usp.br, e-mail: ecsilva@cena.usp.br

    2009-07-15

    Common bean (Phaseolus vulgaris L.) and cowpea (Vigna unguiculata (L.) Walp.) are among the main sources of plant protein for a large part of the world population, mainly that of low income, and nitrogen is the main constituent of these proteins. The objectives of this study were to evaluate, through the {sup 15}N-dilution technique and using rice and non-nodulating soybean as control plants, the relative contributions of nitrogen sources (symbiotically fixed N, soil native N and fertilizer N) on the growth of common bean and cowpea and to compare the isotopic technique (ID) with the difference methods (DM) for the evaluation of symbiotic N{sub 2} fixation. The study was carried out in a greenhouse of the Center for Nuclear Energy in Agriculture - CENA/USP, Sao Paulo State, Brazil, using 5 kg pots with a Typic Haplustox (Dystrophic Red-Yellow Latosol). The experiment was arranged in completely randomized blocks, with 16 treatments and three replications, in an 8 x 2 factorial design. The treatments were eight sampling times: 7, 24, 31, 38, 47, 58, 68 and 78 days after sowing (DAS) and two crops: common bean and cowpea. An N rate of 10 mg kg{sup -1} soil was used, as urea, enriched with an excess of 10 % of {sup 15}N atoms. Symbiotic N fixation supplied the bean and cowpea plants with the greatest amount of accumulated N, followed, in decreasing order, by soil and fertilizer. The highest rate of N symbiotic fixation was observed at the pre-flowering growth stage of the bean and cowpea plants. After the initial growth stage, 24 DAS, rice and non nodulating soybean were appropriate control plants to evaluate symbiotic N fixation. There was a good agreement between ID and DM, except in the initial growth stage of the crops. (author)

  4. Heat Islands

    Science.gov (United States)

    EPA's Heat Island Effect Site provides information on heat islands, their impacts, mitigation strategies, related research, a directory of heat island reduction initiatives in U.S. communities, and EPA's Heat Island Reduction Program.

  5. Island biogeography

    DEFF Research Database (Denmark)

    Whittaker, Robert James; Fernández-Palacios, José María; Matthews, Thomas J.

    2017-01-01

    Islands provide classic model biological systems. We review how growing appreciation of geoenvironmental dynamics of marine islands has led to advances in island biogeographic theory accommodating both evolutionary and ecological phenomena. Recognition of distinct island geodynamics permits gener...

  6. Efectos del fósforo y carbono lábiles en la fijación no simbiótica de N2 en hojarasca de bosques siempreverdes manejados y no manejados de la Isla de Chiloé, Chile Effects of labile phosphorous and carbón on non-symbiotic N2 fixation in logged and unlogged evergreen forests in Chiloé Island, Chile

    Directory of Open Access Journals (Sweden)

    SANDRA E PÉREZ

    2008-06-01

    experimentalmente. El manejo de bosque afectó la composición florística de la hojarasca, pero no hubo diferencias su relación C/N, ni en los contenidos de N o P totales.Nitrogen input to evergreen températe forests of Chiloé Island, Chile occurs predominantly via non-symbiotic fixation (NSF. Because this is a bacterial-mediated process (diazotrophs, in addition to environmental factors (e.g., temperature and moisture, phosphorous availability and energy supply from carbón in the substrate may influence the rates of N fixation. Our hypothesis is that if both phosphorous and carbón are limiting NSF, this limitation would be greater in logged forests, where additions of labile P and C would stimulate microbial activity. Our objectives are to assess the effects of inorganic phosphorus and labile carbón (as glucose additions (0 mmol P/L, 0.645 mmol P/L, 3.23 mmol P/L y 6.45 mmol P/L and 0 mmol P/L, 23.3 mmol C/L, 46.6 mmol C/L y 70 mmol C/L, respectively on the rates of NSF measured in the litter layer of each forest in laboratory assays, under controlled temperature and moisture and using homogeneous litter samples. We studied lowland evergreen rainforests (100-200 m of altitude, located in the Chonchi district, in Chiloé Island. Two forest stands were logged, subjected to industrial and non-industrial selective logging, and the third stand was unlogged (control. The NSF of nitrogen was assessed by the acetylene reduction assay. Two-way ANOVAs showed that phosphorous addition had no effect on acetylene reduction rates (ARR in the litter of logged or unlogged forests, but the addition of labile carbón in the form of glucose negatively affected ARR when applied at the máximum level to the litter of unlogged forest. In all treatments the factor forest accounted for the differences in ARR, which was higher in unlogged forest. These differences were not explained by any of the variables experimentally manipulated in this study. The main difference among forests was floristic

  7. INFLUENCE OF LEGUME RESIDUE AND NITROGEN FERTILIZER ...

    African Journals Online (AJOL)

    USER

    to search for more arable land with reduction in fallow period and decline in fertility ... The stalks are used as feed, fuel, thatch making and in roofing houses. ... soil nitrogen content can be a practicable alternative to reduce the use of chemical .... significance of legume in nitrogen fixation and its inclusion to cropping system.

  8. Cycling of grain legume residue nitrogen

    DEFF Research Database (Denmark)

    Jensen, E.S.

    1995-01-01

    Symbiotic nitrogen fixation by legumes is the main input of nitrogen in ecological agriculture. The cycling of N-15-labelled mature pea (Pisum sativum L.) residues was studied during three years in small field plots and lysimeters. The residual organic labelled N declined rapidly during the initial...... management methods in order to conserve grain legume residue N sources within the soil-plant system....

  9. Anaerobic Nitrogen Fixers on Mars

    Science.gov (United States)

    Lewis, B. G.

    2000-07-01

    The conversion of atmospheric nitrogen gas to the protein of living systems is an amazing process of nature. The first step in the process is biological nitrogen fixation, the transformation of N2 to NH3. The phenomenon is crucial for feeding the billions of our species on Earth. On Mars, the same process may allow us to discover how life can adapt to a hostile environment, and render it habitable. Hostile environments also exist on Earth. For example, nothing grows in coal refuse piles due to the oxidation of pyrite and marcasite to sulfuric acid. Yet, when the acidity is neutralized, alfalfa and soybean plants develop root nodules typical of symbiotic nitrogen fixation with Rhizobium species possibly living in the pyritic material. When split open, these nodules exhibited the pinkish color of leghemoglobin, a protein in the nodule protecting the active nitrogen-fixing enzyme nitrogenase against the toxic effects of oxygen. Although we have not yet obtained direct evidence of nitrogenase activity in these nodules (reduction of acetylene to ethylene, for example), these findings suggested the possibility that nitrogen fixation was taking place in this hostile, non-soil material. This immediately raises the possibility that freeliving anaerobic bacteria which fix atmospheric nitrogen on Earth, could do the same on Mars.

  10. CARBON DIOXIDE FIXATION.

    Energy Technology Data Exchange (ETDEWEB)

    FUJITA,E.

    2000-01-12

    Solar carbon dioxide fixation offers the possibility of a renewable source of chemicals and fuels in the future. Its realization rests on future advances in the efficiency of solar energy collection and development of suitable catalysts for CO{sub 2} conversion. Recent achievements in the efficiency of solar energy conversion and in catalysis suggest that this approach holds a great deal of promise for contributing to future needs for fuels and chemicals.

  11. Environmental impacts of coastal farming: carbon and nitrogen budgets for trout farming activity in Kaldbaksfjørđur (Faroe Islands)

    DEFF Research Database (Denmark)

    Nordi, Gunnvør a; Glud, Ronnie N.; Gaard, Eilif

    2011-01-01

    Flow of organic carbon (OC) and nitrogen through a sea cage trout farm was calculated on the basis of detailed studies of the farming operation, water circulation, OC and nutrient transport and recycling processes in sediment. A third of the OC and nitrogen provided by fish food was incorporated...... derived from fish food settled on the seabed, where it was either mineralized or accumulated in the sediment. Based on transect measurements of diagenetic activity, the farm footprint was found to cover an area ~10 times the farm area. OC mineralization in the sediment increased linearly with increasing...

  12. Climate change affects key nitrogen-fixing bacterial populations on coral reefs

    NARCIS (Netherlands)

    Santos, Henrique F.; Carmo, Flavia L.; Duarte, Gustavo; Dini-Andreote, Francisco; Castro, Clovis B.; Rosado, Alexandre S.; van Elsas, Jan Dirk; Peixoto, Raquel S.

    2014-01-01

    Coral reefs are at serious risk due to events associated with global climate change. Elevated ocean temperatures have unpredictable consequences for the ocean's biogeochemical cycles. The nitrogen cycle is driven by complex microbial transformations, including nitrogen fixation. This study

  13. Climate change affects key nitrogen-fixing bacterial populations on coral reefs

    NARCIS (Netherlands)

    Santos, Henrique F.; Carmo, Flavia L.; Duarte, Gustavo; Dini-Andreote, Francisco; Castro, Clovis B.; Rosado, Alexandre S.; van Elsas, Jan Dirk; Peixoto, Raquel S.

    Coral reefs are at serious risk due to events associated with global climate change. Elevated ocean temperatures have unpredictable consequences for the ocean's biogeochemical cycles. The nitrogen cycle is driven by complex microbial transformations, including nitrogen fixation. This study

  14. Fixation distance and fixation duration to vertical road signs.

    Science.gov (United States)

    Costa, Marco; Simone, Andrea; Vignali, Valeria; Lantieri, Claudio; Palena, Nicola

    2018-05-01

    The distance of first-fixation to vertical road signs was assessed in 22 participants while driving a route of 8.34 km. Fixations to road signs were recorded by a mobile eye-movement-tracking device synchronized to GPS and kinematic data. The route included 75 road signs. First-fixation distance and fixation duration distributions were positively skewed. Median distance of first-fixation was 51 m. Median fixation duration was 137 ms with a modal value of 66 ms. First-fixation distance was linearly related to speed and fixation duration. Road signs were gazed at a much closer distance than their visibility distance. In a second study a staircase procedure was used to test the presentation-time threshold that lead to a 75% accuracy in road sign identification. The threshold was 35 ms, showing that short fixations to a road signs could lead to a correct identification. Copyright © 2018 Elsevier Ltd. All rights reserved.

  15. Present situation concerning studies on associative n-fixation in sugarcane, 'Saccharum officinarum' L

    International Nuclear Information System (INIS)

    Ruschel, A.P.; Vose, P.B.

    1977-01-01

    High nitrogenase activity in sugarcane has been confirmed, using 15 N procedure, which indicated rapid translocation of the fixed nitrogen to the plant tissue. It is observed that there are differences in variety concerning nitrogenase activity in the rhizosphere of sugarcane. Basic calculations and an evaluation of possible biological N-fixation with 15 N suggest that possibly as much as 25-30% of the plant nitrogen may be derived from biological fixation. Both eight and electron microscope studies suggest that there are bacteria inside healthy roots and if such a root is surface sterilized and placed ou nitrogen-free media then bacteria stream from the cut surface [pt

  16. Use of nitrogen-15 in soil-plant studies

    International Nuclear Information System (INIS)

    Sachdev, M.S.; Sachdev, P.; Subbiah, B.V.

    1996-01-01

    In this paper an overview of the selected work carried out in the country and elsewhere on the fertilizer nitrogen use efficiency, fate and balance-sheet, soil and fertilizer nitrogen transformations and biological nitrogen fixation using 15 N is given. 129 refs., 4 tabs

  17. Lipids as paleomarkers to constrain the marine nitrogen cycle

    NARCIS (Netherlands)

    Rush, Darci; Sinninghe Damsté, Jaap S

    Global climate is, in part, regulated by the effect of microbial processes on biogeochemical cycling. The nitrogen cycle, in particular, is driven by microorganisms responsible for the fixation and loss of nitrogen, and the reduction-oxidation transformations of bio-available nitrogen. Within marine

  18. Lipids as paleomarkers to constrain the marine nitrogen cycle

    NARCIS (Netherlands)

    Rush, D.; Sinninghe Damsté, J.S.

    2017-01-01

    Global climate is, in part, regulated by the effect of microbial processes on biogeochemical cycling. The nitrogen cycle, in particular, is driven by microorganisms responsible for the fixation and loss of nitrogen, and the reduction-oxidation transformations of bio-available nitrogen. Within marine

  19. [Effects of reduced nitrogen application and soybean intercropping on nitrogen balance of sugarcane field].

    Science.gov (United States)

    Liu, Yu; Zhang, Ying; Yang, Wen-ting; Li, Zhi-xian; Guan, Ao-mei

    2015-03-01

    A four-year (2010-2013) field experiment was carried out to explore the effects of three planting patterns (sugarcane, soybean monoculture and sugarcane-soybean 1:2 intercropping) with two nitrogen input levels (300 and 525 kg . hm-2) on soybean nitrogen fixation, sugarcane and soybean nitrogen accumulation, and ammonia volatilization and nitrogen leaching in sugarcane field. The results showed that the soybean nitrogen fixation efficiency (NFE) of sugarcane-soybean inter-cropping was lower than that of soybean monoculture. There was no significant difference in NFE among the treatments with the two nitrogen application rates. The nitrogen application rate and inter-cropping did not remarkably affect nitrogen accumulation of sugarcane and soybean. The ammonia volatilization of the reduced nitrogen input treatment was significantly lower than that of the conventional nitrogen input treatment. Furthermore, there was no significant difference in nitrogen leaching at different nitrogen input levels and among different planting patterns. The sugarcane field nitrogen balance analysis indicated that the nitrogen application rate dominated the nitrogen budget of sugarcane field. During the four-year experiment, all treatments leaved a nitrogen surplus (from 73.10 to 400.03 kg . hm-2) , except a nitrogen deficit of 66.22 kg . hm-2 in 2011 in the treatment of sugarcane monoculture with the reduced nitrogen application. The excessive nitrogen surplus might increase the risk of nitrogen pollution in the field. In conclusion, sugarcane-soybean intercropping with reduced nitrogen application is feasible to practice in consideration of enriching the soil fertility, reducing nitrogen pollution and saving production cost in sugarcane field.

  20. A seasonal and spatial comparison of metals, and stable carbon and nitrogen isotopes, in Chincoteague Bay and the marsh deposits of Assateague Island and the adjacent vicinity, Maryland and Virginia

    Science.gov (United States)

    Ellis, Alisha M.; Smith, Christopher G.

    2017-11-28

    After Hurricane Sandy, scientists from the U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center conducted a seasonal collection of estuarine, marsh, and sandy overwash surface sediments from Chincoteague Bay, Tom’s Cove, and the surrounding Assateague Island and Delmarva Peninsula in March–April and October 2014. Surplus surface sediment was analyzed for metals, percent carbon and nitrogen, δ13C, and δ15N as part of a complementary U.S. Geological Survey Coastal and Marine Geology Program Sea-level and Storm Impacts on Estuarine Environments and Shorelines project study. The geochemical subsample analyzed for metals and stable isotopes at each site may be used for comparison with past data sets, to create a modern baseline of the natural distribution of the area, to understand seasonal variability as it relates to the health of the local environment, and to assess marsh-to-bay interactions. The use of metals, stable carbon, and stable nitrogen isotopes allows for a more cohesive snapshot of factors influencing the environment and could aid in tracking environmental change.This report serves as an archive for chemical data derived from the surface sediment. Data are available for a seasonal comparison between the March–April 2014 and October 2014 sampling trips. Downloadable data are available as Microsoft Excel spreadsheets. These additional files include formal Federal Geographic Data Committee metadata (data downloads).

  1. Enzymology and ecology of the nitrogen cycle.

    Science.gov (United States)

    Martínez-Espinosa, Rosa María; Cole, Jeffrey A; Richardson, David J; Watmough, Nicholas J

    2011-01-01

    The nitrogen cycle describes the processes through which nitrogen is converted between its various chemical forms. These transformations involve both biological and abiotic redox processes. The principal processes involved in the nitrogen cycle are nitrogen fixation, nitrification, nitrate assimilation, respiratory reduction of nitrate to ammonia, anaerobic ammonia oxidation (anammox) and denitrification. All of these are carried out by micro-organisms, including bacteria, archaea and some specialized fungi. In the present article, we provide a brief introduction to both the biochemical and ecological aspects of these processes and consider how human activity over the last 100 years has changed the historic balance of the global nitrogen cycle.

  2. Stable carbon and nitrogen isotopic compositions of ambient aerosols collected from Okinawa Island in the western North Pacific Rim, an outflow region of Asian dusts and pollutants

    Science.gov (United States)

    Kunwar, Bhagawati; Kawamura, Kimitaka; Zhu, Chunmao

    2016-04-01

    Stable carbon (δ13C) and nitrogen (δ15N) isotope ratios were measured for total carbon (TC) and nitrogen (TN), respectively, in aerosol (TSP) samples collected at Cape Hedo, Okinawa, an outflow region of Asian pollutants, during 2009-2010. The averaged δ13C and δ15N ratios are -22.2‰ and +12.5‰, respectively. The δ13C values are similar in both spring (-22.5‰) and winter (-22.5‰), suggesting the similar sources and/or source regions. We found that δ13C from Okinawa aerosols are ca. 2‰ higher than those reported from Chinese megacities probably due to photochemical aging of organic aerosols. A strong correlation (r = 0.81) was found between nss-Ca and TSP, suggesting that springtime aerosols are influenced from Asian dusts. However, carbonates in the Asian dusts were titrated with acidic species such as sulfuric acid and oxalic acid during atmospheric transport although two samples suggested the presence of remaining carbonate. No correlations were found between δ13C and tracer compounds (levoglucosan, elemental carbon, oxalic acid, and Na+). During winter and spring, coal burning is significant source in China. Based on isotopic mass balance, contribution of coal burning origin particles to total aerosol carbon was estimated as ca. 97% in winter, which is probably associated with the high emissions in China. Contribution of NO3- to TN was on average 45% whereas that of NH4+ was 18%. These results suggest that vehicular exhaust is an important source of TN in Okinawa aerosols. Concentration of water-soluble organic nitrogen (WSON) is higher in summer, suggesting that WSON is more emitted from the ocean in warmer season whereas inorganic nitrogen is more emitted in winter and spring from pollution sources in the Asian continent.

  3. Effects of water and nitrogen availability on nitrogen contribution by the legume, Lupinus argenteus Pursh

    Science.gov (United States)

    Erin Goergen; Jeanne C. Chambers; Robert Blank

    2009-01-01

    Nitrogen-fixing species contribute to ecosystem nitrogen budgets, but background resource levels influence nodulation, fixation, and plant growth. We conducted a greenhouse experiment to examine the separate and interacting effects of water and N availability on biomass production, tissue N concentration, nodulation, nodule activity, and rhizodeposition of ...

  4. Is the distribution of nitrogen-fixing cyanobacteria in the oceans related to temperature?

    NARCIS (Netherlands)

    Stal, L.J.

    2009-01-01

    Approximately 50% of the global natural fixation of nitrogen occurs in the oceans supporting a considerable part of the new primary production. Virtually all nitrogen fixation in the ocean occurs in the tropics and subtropics where the surface water temperature is 25°C or higher. It is attributed

  5. Fixation Time for Evolutionary Graphs

    Science.gov (United States)

    Nie, Pu-Yan; Zhang, Pei-Ai

    Evolutionary graph theory (EGT) is recently proposed by Lieberman et al. in 2005. EGT is successful for explaining biological evolution and some social phenomena. It is extremely important to consider the time of fixation for EGT in many practical problems, including evolutionary theory and the evolution of cooperation. This study characterizes the time to asymptotically reach fixation.

  6. Nitrogen-use-efficiency: a biologically meaningful definition?

    NARCIS (Netherlands)

    Berendse, F.; Aerts, R.

    1987-01-01

    A parameter to measure the efficiency of nitrogen use should include 1) the mean residence time of the N in the plant, ie the period during which the absorbed N can be used for C-fixation; and 2) the instantaneous rate of C-fixation per unit of N in the plant. It is essential to distinguish between

  7. Complement fixation test to C burnetii

    Science.gov (United States)

    ... complement fixation test; Coxiella burnetii - complement fixation test; C burnetii - complement fixation test ... a specific foreign substance ( antigen ), in this case, C burnetii . Antibodies defend the body against bacteria, viruses, ...

  8. Unusual radioresistance of nitrogen-fixing cultures of Anabaena ...

    Indian Academy of Sciences (India)

    Prakash

    Atlas R M 2004 Handbook of microbiological media; third edition. (Florida: CRC Press) ... nitrogen-fixation, and nodularin production by two Baltic sea cyanobacteria ... Sharma A 1998 Mycotoxins: risk evaluation and management in radiation ...

  9. Evaluation of the biological nitrogen fixation (N{sub 2}) contribution in several forage legumes and the transfer of N to associated grasses; Avaliacao da contribuicao da fixacao biologica de N{sub 2} em varias leguminosas forrageiras e transferencia de N para uma graminea consorciada

    Energy Technology Data Exchange (ETDEWEB)

    Vargas, M S.V.

    1991-12-01

    The objective of experiment 1 was to compare two different techniques for labelling the soil mineral nitrogen with {sup 15} N, for studies to quantify the contribution of biological nitrogen fixation (BNF) to forage legumes using the {sup 15} N isotope dilution technique. The two techniques for labelling the soil were: incorporation a {sup 15} N labelled organic compost (slow release treatment), and split applications of {sup 15} N labelled ammonium sulphate. The evaluation of the techniques was through the quantification of BNF in the Itaguai Hybrid of Centrosema using two non-Na- fixing control plants (P. maximum K K-16 and Sorghum bicolor). The objective of experiment 2 was to quantify the contribution of BNF to forage legumes and the transfer of fixed nitrogen to associated grasses in mixed swards again using the {sup 15} N isotope dilution technique. This study was conducted on a red podzolic soil (Typic Hapludult), with 7 forage legumes and 3 grasses in monoculture, and 3 mixed swards of Brachiaria brizantha with the Centrosema hybrid, Galactia striata and Desmodium ovalifolium, respectively, with varying ratios of grass to legume (4:1 to 1:4). In order to quantify the BNF contributions to the legumes and the transfer of fixed N to the B. brizantha, the plots were amended 8 times with doses of 0.01 g {sup 15} N m{sup -2} of {sup 15} N labelled ammonium sulphate (12.5 atom % {sup 15} N) each 14 days, giving a total of 0.08 g {sup 15} N m{sup -2} of {sup 15} N during the 97 days of the experiment. In monoculture the different forage legumes obtained the equivalent of between 43 and 100 kg N ha{sup -1} from BNF. Stylosanthes guianensis showed the greatest contributions from BNF at 100 Kg N ha{sup -1}. In mixed swards with Brachiaria brizantha the proportion of N derived from BNF in the three legumes studied (Centrosema hybrid, G. striata and D. ovalifolium) was significantly greater than when they were grown in monoculture. (author). 197 refs, 9 figs, 19 tabs.

  10. The marine nitrogen cycle: recent discoveries, uncertainties and the potential relevance of climate change

    NARCIS (Netherlands)

    Voss, M.; Bange, H.W.; Dippner, J.W.; Middelburg, J.J.; Montoya, J.P.; Ward, B.

    2013-01-01

    The ocean’s nitrogen cycle is driven by complex microbial transformations, including nitrogen fixation, assimilation, nitrification, anammox and denitrification. Dinitrogen is the most abundant form of nitrogen in sea water but only accessible by nitrogen-fixing microbes. Denitrification and

  11. 76 FR 29180 - Approval and Promulgation of Air Quality Implementation Plans; Pennsylvania; Control of Nitrogen...

    Science.gov (United States)

    2011-05-20

    ... Promulgation of Air Quality Implementation Plans; Pennsylvania; Control of Nitrogen Oxides Emissions From... Pennsylvania. This revision pertains to the control of nitrogen oxide (NO X ) emissions from Portland cement... oxidation of chemically-bound nitrogen in the fuel and by thermal fixation of nitrogen in the combustion air...

  12. Nitrogen-fixing bacteria in Mediterranean seagrass (Posidonia oceanica) roots

    KAUST Repository

    Garcias Bonet, Neus

    2016-03-09

    Biological nitrogen fixation by diazotrophic bacteria in seagrass rhizosphere and leaf epiphytic community is an important source of nitrogen required for plant growth. However, the presence of endophytic diazotrophs remains unclear in seagrass tissues. Here, we assess the presence, diversity and taxonomy of nitrogen-fixing bacteria within surface-sterilized roots of Posidonia oceanica. Moreover, we analyze the nitrogen isotopic signature of seagrass tissues in order to notice atmospheric nitrogen fixation. We detected nitrogen-fixing bacteria by nifH gene amplification in 13 out of the 78 roots sampled, corresponding to 9 locations out of 26 meadows. We detected two different types of bacterial nifH sequences associated with P. oceanica roots, which were closely related to sequences previously isolated from the rhizosphere of a salt marsh cord grass and a putative anaerobe. Nitrogen content of seagrass tissues showed low isotopic signatures in all the sampled meadows, pointing out the atmospheric origin of the assimilated nitrogen by seagrasses. However, this was not related with the presence of endophytic nitrogen fixers, suggesting the nitrogen fixation occurring in rhizosphere and in the epiphytic community could be an important source of nitrogen for P. oceanica. The low diversity of nitrogen-fixing bacteria reported here suggests species-specific relationships between diazotrophs and P. oceanica, revealing possible symbiotic interactions that could play a major role in nitrogen acquisition by seagrasses in oligotrophic environments where they form lush meadows.

  13. Evaluation of the biological nitrogen fixation contribution in sugarcane plants originated from seeds and inoculated with nitrogen-fixing endophytes Avaliação da contribuição da fixação biológica de nitrogênio em cana-de-açúcar originada de sementes e inoculada com endófitos fixadores de nitrogênio

    Directory of Open Access Journals (Sweden)

    Erineudo de Lima Canuto

    2003-11-01

    Full Text Available The inoculation technique with endophytic diazotrophic bacteria in sugarcane has been shown as an alternative practice to plant growth promotion. The aim of this work was to evaluate the biological nitrogen fixation (BNF contribution by different strains of Herbaspirillum seropedicae and Gluconacetobacter diazotrophicus in sugarcane plant inoculated from seeds. The seeds were planted in pots filled with non-sterile soil, inoculated with the bacterial strains and grown 10 months outside of the greenhouse. The BNF contribution of the inoculated bacteria varied depending on the plant species used as a control. The highest BNF contribution as well as the highest populations of reisolated bacteria was observed with inoculation of H. seropedicae strains. The roots appeared to be the preferential tissues for the establishment of the inoculated species.A técnica de inoculação com bactérias diazotróficas endofíticas na cana-de-açúcar apresenta-se como uma prática alternativa para promover o crescimento vegetal menos dependente da adubação nitrogenada. Este trabalho teve como objetivo avaliar a contribuição da fixação biológica de nitrogênio (FBN por diferentes estirpes de Herbaspirillum seropedicae e Gluconacetobacter diazotrophicus inoculadas em plantas de cana-de-açúcar originadas de semente. As sementes foram plantadas em vasos com solo não estéril, inoculadas com as diferentes bactérias e mantidas por 10 meses ao ar livre. As maiores contribuições da FBN ocorreram com a inoculação de estirpes Herbaspirillum seropedicae, e dependeram da espécie vegetal utilizada como testemunha. As raízes apresentaram-se como o órgão vegetal preferencial para o estabelecimento das espécies inoculadas.

  14. Fixação do nitrogênio do ar pelas bactérias que vivem associadas às raízes do feijão de porco e do feijão baiano Nitrogen fixation by bacteria in association with sword bean and cowpea

    Directory of Open Access Journals (Sweden)

    Hermano Gargantini

    1960-01-01

    .5 and the base saturation of the sail to 70%. The fertilizer applications for N, P2O5,. and K2O were 2.0 g, 2.2 g and 3.0 g respectively, as solutions of NH4NO3, K2HP0(4 and KCl. Harvesting was done at the beginning of blooming-time by cutting the plants even with the ground. Later, both the aerial parts, as well as the roots, were weighed fresh and after drying at 60° C. Nitrogen determination by the Kjeldahl method of these two fractions, aerial parts and roots, were mode after drying. The soil from those pots without nitrogen fertilizer were submitted to the same analysis for comparison with the initial level of this element in the soil. The data obtained indicate that the two leguminous plants showed a good nitrogen fixation capacity and that the feijão baiano was more effective. The amounts of nitrogen fixed in pots that received the best treatments corresponded to 48.5 kg per hectare for the sword bean and 73.0 kg for the "feijão baiano". From this point of view both leguminous plants were satisfactory to be employed as green manure.

  15. Canary Islands

    Science.gov (United States)

    1992-01-01

    This easterly looking view shows the seven major volcanic islands of the Canary Island chain (28.0N, 16.5W) and offers a unique view of the islands that have become a frequent vacation spot for Europeans. The northwest coastline of Africa, (Morocco and Western Sahara), is visible in the background. Frequently, these islands create an impact on local weather (cloud formations) and ocean currents (island wakes) as seen in this photo.

  16. REVISION ANKLE SYNDESMOSIS FIXATION - FUNCTIONAL OUTCOME AFTER TIGHTROPE ® FIXATION

    Directory of Open Access Journals (Sweden)

    Sendhilvelan Rajagopalan

    2016-07-01

    Full Text Available BACKGROUND Syndesmotic disruptions are often seen in ankle fractures. Malreduction of these fractures can result in arthritis and instability. A proportion of these patients with malreduction require revision fixation. This study presents the results of revision fixation in such patients, using the Ankle TightRope ® (Arthrex system. METHODS Between January 2000 to December 2009, 124 patients who underwent ankle fracture fixations with syndesmotic stabilisation were analysed. Out of 124 patients, 8 patients were diagnosed with failure of primary stabilisation (based on radiological and clinical criteria and subjected to revision fixation using the Ankle TightRope ® (Arthrex system. Followup was done at periodic time intervals of 3, 6 and 12 months. Both clinical and radiological assessment was performed. Complications and duration of hospital stay was recorded. Functional evaluation was performed using the American Orthopaedic Foot and Ankle Society (AOFAS scoring system. RESULTS Five patients had good results, one satisfactory and two had poor outcomes. CONCLUSIONS Ankle TightRope ® fixation is an alternative method of stabilisation in patients who require revision syndesmosis fixation. Further studies are required to evaluate this method of revision stabilisation as compared to screws.

  17. Avaliação da atividade de microrganismos do solo em diferentes sistemas de manejo de soja Evaluation of nitrogen fixation and soil microorganisms in soybean under conventional and minimal cultivation regimes

    Directory of Open Access Journals (Sweden)

    O.M. de Castro

    1993-09-01

    experiment that consisted of continuous soybean or corn-soybean rotations as summer crops, with oats or Crotalaria juncea as winter crops. Treatments totaled eight cropping system regimes includig the coventional and minimal cultivation. Soil from a nearby natural forest was used as control. There were six replicate pots for each treatment, three of which were additionally inoculated with K japonicum inoculum when soybeans were sown. Plants were harvested at flowering and shoot dry matter and nitrogen concentration were determined, as well as nodule number, nodule weight and percent mycorrhizal colonization of roots. Soil samples from each field treatment that had been kept in the refrigerator were evaluated to determine the total number of bacteria, fungi, cellulolytic microorganisms and nitrifying bacteria. Soybeans grown in soil from minimal cultivation plots and from crop rotations demonstrated significantly greater nodulation and larger cellulolytic populations. Other microbial groups were not highly affected. Percent mycorrhizal infection of roots was extremely low in all treatments, probably due to the high available phosphate levels in all soils.

  18. Isotopes of carbon, nitrogen and oxygen reveal contributions of submarine groundwater and septic systems discharges to algal bloom in Boracay Island

    International Nuclear Information System (INIS)

    Sucgang, Raymond; Pabroa, Preciosa Corazon; Mendoza, Norman; Racho, Joseph Michael; Bautista, Angel; Morco, Ryan; Petrache, Christina; Castaneda, Soledad; Dela Rosa, Alumanda

    2014-01-01

    The study showed that critical areas in Boracay island were contaminated by coliform bacteria and blue green algae (cyanobacteria). The distribution of tritium, 18 O, 15 N and 13 C in seawater, biota and sediments in the inter tidal zone, helped to identify sites with septic sewage outflows and submarine groundwater discharge, SGD. Nitrates (from 0.0 to 2.3 parts per million, ppm) and nutrients were discovered in seawater, particularly in four identified sites in the bathing zone. Point sources of infiltrating plumes were exposed by anomalies in tritium and 18 O in sea water. Septic and canal outflows as well as land based run-offs and submarine groundwater discharge were the identified causes of nutrient enrichments in sites with eminent algal bloom. The isotope composition implied that algae acquire nutrients from septic contamination, while a number of corals assimilate inorganic fertilizer nutrients from land-based plumes and SGD. The elements identified in sediments and corals were related to the natural mineral matrix of calcareous beach zone materials, however, sporadic spikes of lead, chromium and zinc were detected in particular sites at certain depths. These element spikes proxy processes linked to anthropogenic pollution and or organic matter decomposition in the sediment-water interfaces. The practicality of applying isotope-based techniques in conjunction with other chemical methods for the tracking down of the sources of nutrient contamination in polluted systems in demonstrated by the study.(author)

  19. Efeito de linuron e oryzalin no crescimento da planta, na fixação simbiótica do nitrogênio e na produtividade da soja Effect of linuron and oryzalin on growth, symbiotic nitrogen fixation and yield of soybeans

    Directory of Open Access Journals (Sweden)

    Maria do Carmo S. S. Novo

    1996-01-01

    oryzalin (1.875 and 3.75 kg/ha on plant growth, nodulation, nitrogen fixation and yield of soybean [Glycine max (L. Merril.] cv IAC - 11. The soil type used was a Red Latosol. Beside herbicide treatments there were two controls: one not inoculated and another inoculated with Bradyrhizobium japonicum strain SMS-463 (=29W. All herbicide treatments were inoculated. The experiment was arranged in a split plot randomized block design with four replicates. Samples were taken at 28, 42, 56, 70, 84 and 98 days after sowing (DAS and herbicide application in the first year and at 28, 42, 56, 70, 84 and 105 DAS in the second year. In both years, root, shoot and nodule dry weight were evaluated, as well as grain productivity. In the second year, nitrogenase activity was also evaluated. Generally, there wasn't a positive response of seed inoculation on plant growth and nodulation; but nitrogenase activity was improved by seed inocutalion. In the first year of application, the use of herbicides enhanced plant growth but nitrogen fixation decreased, mainly with the highest rates of both herbicides. Nitrogenase activity was lower with both herbicides, and was more affected by oryzalin. No effect of treatments were observed on soybean grain yield.

  20. Crescimento, nutrição e fixação biológica de nitrogênio em plantios mistos de eucalipto e leguminosas arbóreas Growth, nutrition and biological fixation of nitrogen in mixed-species plantations of eucalypt with leguminous trees

    Directory of Open Access Journals (Sweden)

    Selma Regina de Freitas Coelho

    2007-06-01

    Full Text Available O objetivo deste trabalho foi avaliar o crescimento inicial da parte aérea e do sistema radicular, a nutrição mineral e a fixação biológica de N2 (FBN em plantios consorciados de Eucalyptus grandis e leguminosas arbóreas. O delineamento experimental foi o de blocos ao acaso com três repetições e sete tratamentos por bloco. Nas linhas de plantio, entre as plantas de E. grandis, foram plantadas, intercaladamente, leguminosas arbóreas nativas de matas brasileiras - Peltophorum dubium, Inga sp., Mimosa scabrella, Acacia polyphylla, Mimosa caesalpiniaefolia - e uma leguminosa exótica, Acacia mangium. Realizou-se, também, o plantio puro de E. grandis. Mimosa scabrella e A. mangium foram as leguminosas com maior crescimento. Eucalyptus grandis consorciado com M. scabrella cresceu menos, no entanto foi o povoamento com maior acumulação de biomassa. As densidades de raízes finas (DRF do E. grandis foram 6 a 20 vezes maiores que as DRF das leguminosas na camada superficial do solo (0-10 cm 24 meses após plantio. A DRF de M. scabrella e de M. caesalpiniaefolia foi maior na camada 30-50 cm e menor na camada 10-30 cm. Os valores de delta15N da M. scabrella indicam que 90% do N acumulado em seus tecidos é oriundo da FBN.The objective of this work was to assess interactions between species on the above and belowground growth, nitrogen uptake and biological nitrogen fixation (BNF in mixed stands of Eucalyptus grandis and native leguminous N2-fixing trees. A complete randomized block design was installed with seven treatments and three blocks. Within the lines of the E. grandis seedlings, native leguminous N2-fixing trees - Peltophorum dubium, Inga sp., Mimosa scabrella, Acacia polyphylla, Mimosa caesalpiniaefolia - and one exotic leguminous plant, Acacia mangium, were intercropped. E. grandis was also solely planted. Mimosa scabrella and A. mangium were the legume trees that presented the highest growth. Although E. grandis showed a lower

  1. Key role of symbiotic dinitrogen fixation in tropical forest secondary succession

    Science.gov (United States)

    Batterman, Sarah A.; Hedin, Lars O.; van Breugel, Michiel; Ransijn, Johannes; Craven, Dylan J.; Hall, Jefferson S.

    2013-10-01

    Forests contribute a significant portion of the land carbon sink, but their ability to sequester CO2 may be constrained by nitrogen, a major plant-limiting nutrient. Many tropical forests possess tree species capable of fixing atmospheric dinitrogen (N2), but it is unclear whether this functional group can supply the nitrogen needed as forests recover from disturbance or previous land use, or expand in response to rising CO2 (refs 6, 8). Here we identify a powerful feedback mechanism in which N2 fixation can overcome ecosystem-scale deficiencies in nitrogen that emerge during periods of rapid biomass accumulation in tropical forests. Over a 300-year chronosequence in Panama, N2-fixing tree species accumulated carbon up to nine times faster per individual than their non-fixing neighbours (greatest difference in youngest forests), and showed species-specific differences in the amount and timing of fixation. As a result of fast growth and high fixation, fixers provided a large fraction of the nitrogen needed to support net forest growth (50,000kg carbon per hectare) in the first 12years. A key element of ecosystem functional diversity was ensured by the presence of different N2-fixing tree species across the entire forest age sequence. These findings show that symbiotic N2 fixation can have a central role in nitrogen cycling during tropical forest stand development, with potentially important implications for the ability of tropical forests to sequester CO2.

  2. Key role of symbiotic dinitrogen fixation in tropical forest secondary succession.

    Science.gov (United States)

    Batterman, Sarah A; Hedin, Lars O; van Breugel, Michiel; Ransijn, Johannes; Craven, Dylan J; Hall, Jefferson S

    2013-10-10

    Forests contribute a significant portion of the land carbon sink, but their ability to sequester CO2 may be constrained by nitrogen, a major plant-limiting nutrient. Many tropical forests possess tree species capable of fixing atmospheric dinitrogen (N2), but it is unclear whether this functional group can supply the nitrogen needed as forests recover from disturbance or previous land use, or expand in response to rising CO2 (refs 6, 8). Here we identify a powerful feedback mechanism in which N2 fixation can overcome ecosystem-scale deficiencies in nitrogen that emerge during periods of rapid biomass accumulation in tropical forests. Over a 300-year chronosequence in Panama, N2-fixing tree species accumulated carbon up to nine times faster per individual than their non-fixing neighbours (greatest difference in youngest forests), and showed species-specific differences in the amount and timing of fixation. As a result of fast growth and high fixation, fixers provided a large fraction of the nitrogen needed to support net forest growth (50,000 kg carbon per hectare) in the first 12 years. A key element of ecosystem functional diversity was ensured by the presence of different N2-fixing tree species across the entire forest age sequence. These findings show that symbiotic N2 fixation can have a central role in nitrogen cycling during tropical forest stand development, with potentially important implications for the ability of tropical forests to sequester CO2.

  3. Permanganate Fixation of Plant Cells

    Science.gov (United States)

    Mollenhauer, Hilton H.

    1959-01-01

    In an evaluation of procedures explored to circumvent some of the problems of osmium tetroxide-fixation and methacrylate embedding of plant materials, excised segments of root tips of Zea mays were fixed for electron microscopy in potassium permanganate in the following treatment variations: unbuffered and veronal-acetate buffered solutions of 0.6, 2.0, and 5.0 per cent KMnO4 at pH 5.0, 6.0, 6.7, and 7.5, and temperatures of 2–4°C. and 22°C. After fixation the segments were dehydrated, embedded in epoxy resin, sectioned, and observed or photographed. The cells of the central region of the rootcap are described. The fixation procedures employing unbuffered solutions containing 2.0 to 5.0 per cent KMnO4 at a temperature of 22°C. gave particularly good preservation of cell structure and all membrane systems. Similar results were obtained using a solution containing 2.0 per cent KMnO4, buffered with veronal-acetate to pH 6.0, and a fixation time of 2 hours at 22°C. The fixation procedure utilizing veronal-acetate buffered, 0.6 per cent KMnO4 at 2–4°C. and pH 6.7 also gave relatively good preservation of most cellular constituents. However, preservation of the plasma membrane was not so good, nor was the intensity of staining so great, as that with the group of fixatives containing greater concentrations of KMnO4. The other fixation procedures did not give satisfactory preservation of fine structure. A comparison is made of cell structures as fixed in KMnO4 or OsO4. PMID:14423414

  4. EFFECT OF BLUE GREEN ALGAE ON SOIL NITROGEN

    African Journals Online (AJOL)

    Yagya Prasad Paudel

    2012-07-31

    Jul 31, 2012 ... associated with soil dessication at the end of the cultivation cycle and algal growth ... blue-green algae (BGA) on soil nitrogen was carried out from June to December 2005. .... Nitrogen fixation by free living Micro-organisms.

  5. External fixation of "intertrochanteric" fractures.

    Science.gov (United States)

    Gani, Naseem Ul; Kangoo, Khursheed Ahmed; Bashir, Arshad; Muzaffer, Rahil; Bhat, Mohammad Farooq; Farooq, Munir; Badoo, Abdul Rashid; Dar, Imtiyaz Hussian; Wani, Mudassir Maqbool

    2009-10-10

    In developing countries, due to limited availability of modern anesthesia and overcrowding of the hospitals with patients who need surgery, high-risk patients with "intertrochanteric" fractures remain unsuita ble for open reduction and internal fixation.The aim of this study was to analyze the results of external fixation of "intertrochanteric" fractures in high-risk geriatric patients in a developing country.The results of 62 ambulatory high-risk geriatric patients with a mean age of 70 years (range 58-90 years) with "intertrochanteric" fractures, in whom external fixation was performed, are reported.Eight patients died during follow-up due to medical causes unrelated to the surgical procedure. So only 54 patients were available for final assessment. Procedure is simple, performed under local anesthesia, requires less time for surgery and is associated with less blood loss. Good fixation and early ambulation was achieved in most of the patients. Average time to union was 14 weeks. Thirty-one patients developed superficial pin tract infection and 28 patients had average shortening of 15 mm due to impaction and varus angulation. Functional outcome was assessed using Judet's point system. Good to excellent results were achieved in 44 patients.This study demonstrated that external fixation of "intertrochantric" fractures performed under local anesthesia offers significant advantage in ambulatory high-risk geriatric patients especially in a developing country.

  6. Termites create spatial structure and govern ecosystem function by affecting N2 fixation in an East African savanna.

    Science.gov (United States)

    Fox-Dobbs, Kena; Doak, Daniel F; Brody, Alison K; Palmer, Todd M

    2010-05-01

    The mechanisms by which even the clearest of keystone or dominant species exert community-wide effects are only partially understood in most ecosystems. This is especially true when a species or guild influences community-wide interactions via changes in the abiotic landscape. Using stable isotope analyses, we show that subterranean termites in an East African savanna strongly influence a key ecosystem process: atmospheric nitrogen fixation by a monodominant tree species and its bacterial symbionts. Specifically, we applied the 15N natural abundance method in combination with other biogeochemical analyses to assess levels of nitrogen fixation by Acacia drepanolobium and its effects on co-occurring grasses and forbs in areas near and far from mounds and where ungulates were or were not excluded. We find that termites exert far stronger effects than do herbivores on nitrogen fixation. The percentage of nitrogen derived from fixation in Acacia drepanolobium trees is higher (55-80%) away from mounds vs. near mounds (40-50%). Mound soils have higher levels of plant available nitrogen, and Acacia drepanolobium may preferentially utilize soil-based nitrogen sources in lieu of fixed nitrogen when these sources are readily available near termite mounds. At the scale of the landscape, our models predict that termite/soil derived nitrogen sources influence >50% of the Acacia drepanolobium trees in our system. Further, the spatial extent of these effects combine with the spacing of termite mounds to create highly regular patterning in nitrogen fixation rates, resulting in marked habitat heterogeneity in an otherwise uniform landscape. In summary, we show that termite-associated effects on nitrogen processes are not only stronger than those of more apparent large herbivores in the same system, but also occur in a highly regular spatial pattern, potentially adding to their importance as drivers of community and ecosystem structure.

  7. Optimising carbon and nitrogen sources for Azotobacter ...

    African Journals Online (AJOL)

    user

    2011-04-11

    Apr 11, 2011 ... Edificio Manuel Ancizar, Universidad Nacional de Colombia, Bogotá, D.C., Colombia. ..... 0,04. 0,06. 0,08. 0,10. Run 9 Run 10 Run 13 Run 14. A cetylen e red u ctio n. (n m .... Biological nitrogen fixation in the tropics: Social.

  8. Determinação da fixação biológica de nitrogênio no amendoim forrageiro (Arachis spp. por intermédio da abundância natural de 15N Determination of biological nitrogen fixation by the forage groundnut (Arachis spp. using the 15N natural abundance technique

    Directory of Open Access Journals (Sweden)

    Cesar Heraclides Behling Miranda

    2003-12-01

    Full Text Available Quantificou-se a fixação biológica de nitrogênio (FBN em cinco acessos de Arachis pintoi (BRA31534, BRA31828, BRA31796, BRA15121 e BRA30333 e dois de A. repens (BRA31801 e BRA31861. Os mesmos foram estabelecidos em um solo Latosolo Vermelho Escuro sujeito a inundação estacional, sendo a FBN estimada segundo a técnica da abundância natural do isótopo 15N (d15N. Estolões dos acessos foram plantados em novembro de 1999, em parcelas de 2,0 m x 2,0 m, com quatro repetições, distribuídas em blocos ao acaso. A massa verde das plantas acima de cinco centímetros do solo foi colhida em janeiro de 2000 e seca em estufa a 65ºC até peso constante, sendo posteriormente pesada e moída para análise dos conteúdos em N e d15N, em espectrômetro de massa. Verificaram-se diferenças significativas entre os genótipos quanto à produção de matéria seca (MS e N total, sobressaindo-se BRA31534 e BRA31828, com produções de 4,2 t/ha e conteúdos totais de N de 102 e 110 kg/ha, respectivamente. Os acessos BRA30333 e BRA31861 produziram apenas 2,6 t de MS/ha, com 59 e 65 kg/ha de N total, respectivamente. As taxas de FBN dos acessos testados, medidas por comparação dos seus teores de d15N com os de plantas não fixadoras crescendo na mesma área, variaram de 36% (BRA15121 a 90% (BRA31828 do N total das plantas, equivalente a 26 e 99 kg de N/ha, respectivamente. Verificou-se correlação positiva e significativa (r = 0,92, pThe biological nitrogen fixation (BNF of five Arachis pintoi (BRA31534, BRA31828, BRA31796, BRA15121 E BRA30333 and two A. repens (BRA31801 e BRA31861 accessions, grown in a Dark Red Latosol prone to seasonal flooding was evaluated using the 15N natural abundance method (d15N. Stolons of each accession were planted in November 1999, in plots of 2.0 m by 2.0 m, with four replications allotted to randomized blocks. Plant mass above five cm was harvested in January 2000. There were significant differences among the tested

  9. Mineral commodity profiles: nitrogen

    Science.gov (United States)

    Kramer, Deborah A.

    2004-01-01

    Overview -- Nitrogen (N) is an essential element of life and a part of all animal and plant proteins. As a part of the DNA and RNA molecules, nitrogen is an essential constituent of each individual's genetic blueprint. As an essential element in the chlorophyll molecule, nitrogen is vital to a plant's ability to photosynthesize. Some crop plants, such as alfalfa, peas, peanuts, and soybeans, can convert atmospheric nitrogen into a usable form by a process referred to as 'fixation.' Most of the nitrogen that is available for crop production, however, comes from decomposing animal and plant waste or from commercially produced fertilizers. Commercial fertilizers contain nitrogen in the form of ammonium and/or nitrate or in a form that is quickly converted to the ammonium or nitrate form once the fertilizer is applied to the soil. Ammonia is generally the source of nitrogen in fertilizers. Anhydrous ammonia is commercially produced by reacting nitrogen with hydrogen under high temperatures and pressures. The source of nitrogen is the atmosphere, which is almost 80 percent nitrogen. Hydrogen is derived from a variety of raw materials, which include water, and crude oil, coal, and natural gas hydrocarbons. Nitrogen-based fertilizers are produced from ammonia feedstocks through a variety of chemical processes. Small quantities of nitrates are produced from mineral resources principally in Chile. In 2002, anhydrous ammonia and other nitrogen materials were produced in more than 70 countries. Global ammonia production was 108 million metric tons (Mt) of contained nitrogen. With 28 percent of this total, China was the largest producer of ammonia. Asia contributed 46 percent of total world ammonia production, and countries of the former U.S.S.R. represented 13 percent. North America also produced 13 percent of the total; Western Europe, 9 percent; the Middle East, 7 percent; Central America and South America, 5 percent; Eastern Europe, 3 percent; and Africa and Oceania

  10. Nitrogen studies for achieving the whole-year harvest

    International Nuclear Information System (INIS)

    Boven, G.D.; Danso, K.A.

    1987-01-01

    The IAEA activity in solving the problems related to recovery of productivity of soils subjected to erosion in tropical regions using nitrogen-fixator plants which include pasture bean crops and trees, is considered. The IAEA activity covers development of appropriate methods of changing fixed nitrogen in perennial plants, determination of practical ways of increasing nitrogen fixation and development of reliable and high-productivity systems of bean-herb pastures. The main attention is paid to methods of farming and selection. Favourable effect of forest planting on recovery and preservation of soil productivity and important role of isotopic and nuclear methods (using 15 N) in care for trees and nitrogen fixation improvement are underlined

  11. Optimising biological N2 fixation by legumes in farming systems

    International Nuclear Information System (INIS)

    Hardarson, Gudni; Atkins, Craig

    2001-01-01

    Whether grown as pulses for grain, as green manure, as pastures or as the tree components of agro-forestry systems, the value of leguminous crops lies in their ability to fix atmospheric N 2 , so reducing the use of expensive fertiliser N and enhancing soil fertility. N 2 fixing legumes provide the basis for developing sustainable farming systems that incorporate integrated nutrient management. By exploiting the stable nitrogen isotope 15 N, it has been possible to reliably measure rates of N 2 fixation in a wide range of agro-ecological field situations involving many leguminous species. The accumulated data demonstrate that there is a wealth of genetic diversity among legumes and their Rhizobium symbionts which can be used to enhance N 2 fixation. Practical agronomic and microbiological means to maximise N inputs by legumes have also been identified. (author)

  12. Nitrogen fixation and growth response of Alnus Rubra following fertiliztion with urea or biosolids Fixação de nitrogênio e crescimento de Alnus Rubra fertilização com uréia ou biosólidos

    Directory of Open Access Journals (Sweden)

    Linda S. Gaulke

    2006-08-01

    Full Text Available Nitrogen fertilization of forests using biosolids offers a potentially environmentally friendly means to accelerate tree growth. This field study was designed to analyze the effects of nitrogen fertilization on the symbiotic, nitrogen (N-fixing relationship between Alnus rubra Bong. (red alder and Frankia. Anaerobically digested, class B biosolids and synthetic urea (46% N were applied at rates of 140, 280 and 560 kg ha-1 available N to a well-drained, sandy, glacial outwash soil in the Indianola series (mixed, mesic Dystric Xeropsamments. Plots were planted with A. rubra seedlings. At the end of each of two growing seasons trees were harvested and analyzed for the rate of N fixation (as acetylene reduction activity, biomass and foliar N. At year 1, there was no N fixation for trees grown with urea amendments, but control (17 µmol C2H4 g-1 hr-1 and biosolids (26-45 µmol C2H4 g-1 hr-1 trees were fixing N. At the end of year 2, all trees in all treatments were fixing N (7 µmol C2H4 g-1 hr-1, 4-16 µmol C2H4 g-1 hr-1, and 20-29 µmol C2H4 g-1 hr-1 for control, urea and biosolids respectively. Trees grown with biosolids amendments were larger overall (year 1 shoot biomass 10 g, 5 g, and 23 g for control, urea, and biosolids respectively, year 2 shoot biomass 50 g, 51 g, and 190 g for control, urea, and biosolids respectively with higher concentrations of foliar N for both years of the study (year 1 foliar N 26 g kg-1, 27 g kg-1, and 40 g kg-1 for control, urea, and biosolids respectively, year 2 foliar N 17 g kg-1, 19 g kg-1, and 23 g kg-1 for control, urea, and biosolids respectively. Trees grown with urea amendments appeared to use the urea N over Frankia supplied N, whereas the biosolids trees appeared to be able to use both N in biosolids and N from Frankia. The results from this study indicated that the greater growth of A. rubra may have been responsible for the observed higher N demand. Biosolids may have supplied other nutrients to the

  13. Nitrogen fixation in lichens is important for improved rock weathering

    Indian Academy of Sciences (India)

    MADU

    Upon colonization of the land surface, microorganisms would face, among other problems, low concentrations of many nutrients in available water. They are known to utilize a variety of methods to extract nutrients from mineral surfaces, among which the most prevalent may be the secretion of organic acids (Robert and ...

  14. The Relationship Between Iron and Nitrogen Fixation in Trichodesmium spp.

    Science.gov (United States)

    2009-06-01

    Genes essential to iron transport in the cyanobacterium Synechocystis sp. strain PCC 6803. J Bacteriol 183: 2779-2784. Keren, N., Aurora , R., and...where surface salinity measurements indicate that we were sampling in the Amazon River plume. At E21, the surface salinity measured by the CTD was 32.5

  15. Nitrogen fixation of Acacia mangium Willd. from two seed sources ...

    African Journals Online (AJOL)

    These consisted of bulk seedlots collected from seed orchards in Sumatra, one based on natural provenances from the Cairns region, Queensland, Australia, and the other on the Muting natural provenance, Papua, Indonesia. The seedlots were grown under contrasting P supply (application rates of 0 and 100 kg ha−1) on ...

  16. Symbiotic nitrogen fixation in legumes: Perspectives for saline agriculture

    NARCIS (Netherlands)

    Bruning, B.; Rozema, J.

    2013-01-01

    Saline agriculture provides a solution for at least two environmental and social problems. It allows us to return to agricultural production areas that have been lost as a consequence of salinization and it can save valuable fresh water by using brackish or salt water to irrigate arable lands. Sea

  17. Nitrogen fixation in lichens is important for improved rock weathering

    Indian Academy of Sciences (India)

    MADU

    1996), suggesting that fungal acid production is altered in the lichen. Weathering .... 5019 biofilm, (vii) S. recemosum + B. elkanii SEMIA 5019 biofilm, and (viii) the .... chemical factors in soil mineral wethering; in Interactions of soil minerals with ...

  18. Effect of Phosphorus Fertilizer on Nitrogen Fixation by Some Grain ...

    African Journals Online (AJOL)

    acer

    Sahelian region of North-eastern Nigeria, low phosphorus content of the soil may restrict rhizobia population ... kgNha-1 in northern Guinea savanna zone of ... significant difference between treatments were ..... communities of southern Borno.

  19. Comparison of Outcomes of Operatively Treated Bicondylar Tibial Plateau Fractures by External Fixation and Internal Fixation

    Directory of Open Access Journals (Sweden)

    CC Chan

    2012-03-01

    Full Text Available The outcome of bicondylar tibial plateau fractures treated with either external fixation (35 patients or internal fixation (24 patients was reviewed. Outcome measures included the Rasmussen score, clinical complications, development of osteoarthritis and the requirement for total knee replacement (TKR. Twenty-two (92% anatomical reductions were achieved in the internal fixation group compared to 27 (77% in the external fixation group. Infective complications were more common in the external fixation group (9 patients, 26% due to pin tract infection. There were no deep infections in the internal fixation group. The mean Rasmussen score was not significantly different (mean score 32 in external fixation and 29 in internal fixation between the two groups and the incidence of osteoarthritis was the same in both groups. Four patients in the external fixation group underwent a TKR compared to 5 patients in the internal fixation group. Bicondylar tibial plateau fractures have similar outcomes following external or internal fixation.

  20. Field evaluation of N2 fixation by seventeen mung bean genotypes in the Philippines

    International Nuclear Information System (INIS)

    Rosales, C.M.; Rivera, F.; Hautia, R.A.; Del Rosario, E.

    1994-12-01

    Seventeen mung bean genotypes were screened for biological nitrogen fixation (BNF) during the late dry (March-May) and early dry (October-December) seasons of 1992 in the Philippines. The 15 N isotope dilution method was used to measure N 2 fixation. Performances were quantified based on both indirect and direct measurements of N 2 fixation. Genetic variation was observed among varieties tested for some BNF characteristic. However, genetic variability for percent N derived from fixation (%Ndfa) was not evident. PAEC 3 mutant, Taiwan Green, Acc 687 and Pagasa 7 were the best performers. Whereas Acc 2041 consistently performed poorly for most of the BNF characters tested. (author). 14 refs., 1 fig., 2 tabs

  1. Present Status of Nitrogen Fixation by Reactor Radiation; Etat Actuel des Recherches sur l'oxydation directe de l'azote sous irradiation dans des reacteurs; Sovremennoe sostoyani opytov po okisleniyu azota izlucheniem iz reaktorov; Estado actual de las investigaciones sobre fijacion del nitrogeno por irradiacion en reactores

    Energy Technology Data Exchange (ETDEWEB)

    Harteck, P; Dondes, S [Rensselaer Polytechnic Institute, Troy, NY (United States)

    1960-07-15

    Investigations in nitrogen fixation by reactor radiation which have been carried out at Rensselear and Brookhaven National Laboratory for a number of years, have used the fission recoil energy directly as ionizing radiation by means of the dispersion of U{sup 235} in glass fibers about five microns in diameter. The effects of temperature, pressure and nitrogen-oxygen ratio on the G-value for nitrogen fixation have been determined and reported in the literature. A brief summary of this work is given. The above work has been done in static systems; more recent work has involved both static and flow systems. In static systems, major emphasis has been placed on the effect of radiation intensity especially at the kinetic radiation equilibrium. It has been found that the production of N0{sub 2} and N{sub 2}0 in 4:1 and 2:1 nitrogen-oxygen mixtures proceeds to the point of total oxygen consumption. A flow (cycling) system is now operating in a loop in the Brookhaven reactor. Data are presented on the effects of temperature, pressure, mixture ratio and radiation intensity which may be applied to the design of a future chemonuclear reactor. The present system is operating at 10 atmospheres and 150{sup o}C. The temperature is a function of the fission energy released in the glass fibers and the heat resistance of the loop. Another loop to operate at 50 - 75 atmospheres and 600{sup o}C is under construction. These loops make possible the evaluation of the characteristics of a continuous system, including the behaviour of the fission products released in the gas stream. The complicated kinetics of nitrogen oxidation are outlined in three stages: initial reactions in the systems, reactions after some fixed nitrogen has been produced, and finally the kinetics at radiation equilibrium. The conditions for the formation of N{sub 2}0{sub 3}, N{sub 2}0{sub 4} and O{sub 3} are considered, together with their effects and the overall process. (author) [French] Des recherches sur l

  2. Tropical Dominance of N2 Fixation in the North Atlantic Ocean

    Science.gov (United States)

    Marconi, Dario; Sigman, Daniel M.; Casciotti, Karen L.; Campbell, Ethan C.; Alexandra Weigand, M.; Fawcett, Sarah E.; Knapp, Angela N.; Rafter, Patrick A.; Ward, Bess B.; Haug, Gerald H.

    2017-10-01

    To investigate the controls on N2 fixation and the role of the Atlantic in the global ocean's fixed nitrogen (N) budget, Atlantic N2 fixation is calculated by combining meridional nitrate fluxes across World Ocean Circulation Experiment sections with observed nitrate 15N/14N differences between northward and southward transported nitrate. N2 fixation inputs of 27.1 ± 4.3 Tg N/yr and 3.0 ± 0.5 Tg N/yr are estimated north of 11°S and 24°N, respectively. That is, 90% of the N2 fixation in the Atlantic north of 11°S occurs south of 24°N in a region with upwelling that imports phosphorus (P) in excess of N relative to phytoplankton requirements. This suggests that, under the modern iron-rich conditions of the equatorial and North Atlantic, N2 fixation occurs predominantly in response to P-bearing, N-poor conditions. We estimate a N2 fixation rate of 30.5 ± 4.9 Tg N/yr north of 30°S, implying only 3 Tg N/yr between 30° and 11°S, despite evidence of P-bearing, N-poor surface waters in this region as well; this is consistent with iron limitation of N2 fixation in the South Atlantic. Since the ocean flows through the Atlantic surface in Pacific basins.

  3. Fixação biológica de nitrogênio e teores foliares de nutrientes na soja em função de doses de molibdênio e gesso agrícola Biological nitrogen fixation and leaf nutrient concentration on soybean as a function of molybdenum and gypsum levels

    Directory of Open Access Journals (Sweden)

    Evandro Gelain

    2011-04-01

    Full Text Available A competitividade econômica da soja brasileira no mercado mundial se deve, em grande parte, aos benefícios da fixação biológica do nitrogênio na cultura. O trabalho foi conduzido a campo, sob sistema plantio direto, em condição de sequeiro, no Município de Maracaju-MS, com o objetivo de avaliar a nodulação, o crescimento, nutrição mineral e produtividade de grãos da soja submetida a diferentes doses de gesso agrícola e molibdênio. Foi utilizado o delineamento experimental de blocos ao acaso, com cinco repetições e esquema de parcelas subdivididas, sendo as parcelas representadas por quatro doses de gesso agrícola (0, 1.000, 2.000 e 3.000 kg ha-1 e as subparcelas, por quatro doses de molibdênio (0, 20, 40 e 60 g ha-1. Não houve efeito da interação gesso x Mo sobre a produtividade da soja. O gesso agrícola não influencia no teor foliar de N e na produtividade. O Mo proporciona incrementos na produtividade e no teor de proteínas dos grãos.The economic competitiveness of Brazilian soybeans on the world market occurs, in large part, due to the benefits of biological nitrogen fixation in this crop. The field experiment was carried out in Maracaju, Mato Grosso do Sul State, Brazil, under no-tillage system, in rainfed condition. The aim was to evaluate nodulation, growth, mineral nutrition and grain yield of soybeans under different doses of gypsum and molybdenum. The experimental design used was a randomized block with five replicates and arranged in a split-plot squeme, with the plot represented by four doses of gypsum (0, 1.000, 2.000 and 3.000 kg ha-1 and the subplots by four doses of molybdenum (0, 20, 40 and 60 g ha-1. There were no interaction effects of Mo x gypsum for grain yield. Gypsum has no influence in the N leaf content and grain yield. Mo increases grain yield and protein levels in the grain.

  4. Incorporating nitrogen fixing cyanobacteria in the global biogeochemical model HAMOCC

    Science.gov (United States)

    Paulsen, Hanna; Ilyina, Tatiana; Six, Katharina

    2015-04-01

    Nitrogen fixation by marine diazotrophs plays a fundamental role in the oceanic nitrogen and carbon cycle as it provides a major source of 'new' nitrogen to the euphotic zone that supports biological carbon export and sequestration. Since most global biogeochemical models include nitrogen fixation only diagnostically, they are not able to capture its spatial pattern sufficiently. Here we present the incorporation of an explicit, dynamic representation of diazotrophic cyanobacteria and the corresponding nitrogen fixation in the global ocean biogeochemical model HAMOCC (Hamburg Ocean Carbon Cycle model), which is part of the Max Planck Institute for Meteorology Earth system model (MPI-ESM). The parameterization of the diazotrophic growth is thereby based on available knowledge about the cyanobacterium Trichodesmium spp., which is considered as the most significant pelagic nitrogen fixer. Evaluation against observations shows that the model successfully reproduces the main spatial distribution of cyanobacteria and nitrogen fixation, covering large parts of the tropical and subtropical oceans. Besides the role of cyanobacteria in marine biogeochemical cycles, their capacity to form extensive surface blooms induces a number of bio-physical feedback mechanisms in the Earth system. The processes driving these interactions, which are related to the alteration of heat absorption, surface albedo and momentum input by wind, are incorporated in the biogeochemical and physical model of the MPI-ESM in order to investigate their impacts on a global scale. First preliminary results will be shown.

  5. N2-fixation by freshly isolated Nostoc from coralloid roots of the cycad Macrozamia riedlei (Fisch. ex Gaud.) Gardn

    International Nuclear Information System (INIS)

    Lindblad, P.; Atkins, C.A.; Pate, J.S.

    1991-01-01

    Nitrogenase (EC 1.7.99.2) activity (acetylene reduction) and nitrogen fixation ( 15 N 2 fixation) were measured in cyanobacteria freshly isolated from the coralloid roots of Macrozamia riedlei (Fisch. ex Gaud.) Gardn. The data indicate that cyanobacteria within cycad coralloid roots are differentiated specifically for symbiotic functioning in a microaerobic environment. Specializations include a high heterocyst frequency, enhanced permeability to O 2 , and a direct dependence on the cycad for substrates to support nitrogenase activity

  6. Plant, Microbiome, and Biogeochemistry: Quantifying moss-associated N fixation in Alaska

    Science.gov (United States)

    Stuart, J.; Mack, M. C.; Holland Moritz, H.; Fierer, N.; McDaniels, S.; Lewis, L.

    2017-12-01

    The future carbon (C) sequestration potential of the Arctic and boreal zones, currently the largest terrestrial C sink globally, is linked to nitrogen (N) cycling and N availability vis-a-vis C accumulation and plant species composition. Pristine environments in Alaska have low anthropogenic N deposition (<1 kg N ha-1 yr-1), and the main source of new N to these ecosystems is through previously overlooked N-fixation from microbial communities on mosses. Despite the importance of moss associated N-fixation, the relationship between moss species, microbial communities, and fixation rates remains ambiguous. In the summer of 2016, the fixation rates of 20 moss species from sites around both Fairbanks and Toolik Lake were quantified using 15N2 incubations. Subsequently, the microbial community and moss genome of the samples were also analyzed by collaborators. The most striking result is that all sampled moss genera fixed N, including well-studied feather mosses such as Hylocomium splendens and Pleurozium schreberi as well as less common but ecologically relevant mosses such as Aulacomnium spp., Dicranum spp., Ptilium crista-castrensis, and Tomentypnum nitens. Across all samples, preliminary fixation rates ranged from 0.004-19.994 µg N g-1 moss d-1. Depending upon percent cover, moss-associated N fixation is the largest input of new N to the ecosystem. Given this, linking variation in N-fixation rates to microbial and moss community structures can be helpful in predicting future trends of C and N cycling in northern latitudes. Vegetation changes, alterations in downstream biogeochemical N processes, and anthropogenic N deposition could all interact with or alter moss associated N-fixation, thereby changing ecosystem N inputs. Further elucidation of the species level signal in N-fixation rates and microbial community will augment our knowledge of N cycling in northern latitudes, both current and future.

  7. Benthic Dinitrogen Fixation Traversing the Oxygen Minimum Zone Off Mauritania (NW Africa

    Directory of Open Access Journals (Sweden)

    Jessica Gier

    2017-12-01

    Full Text Available Despite its potential to provide new nitrogen (N to the environment, knowledge on benthic dinitrogen (N2 fixation remains relatively sparse, and its contribution to the marine N budget is regarded as minor. Benthic N2 fixation is often observed in organic-rich sediments coupled to heterotrophic metabolisms, such as sulfate reduction. In the present study, benthic N2 fixation together with sulfate reduction and other heterotrophic metabolisms were investigated at six station between 47 and 1,108 m water depth along the 18°N transect traversing the highly productive upwelling region known as Mauritanian oxygen minimum zone (OMZ. Bottom water oxygen concentrations ranged between 30 and 138 μM. Benthic N2 fixation determined by the acetylene reduction assay was detected at all stations with highest rates (0.15 mmol m−2 d−1 on the shelf (47 and 90 m water depth and lowest rates (0.08 mmol m−2 d−1 below 412 m water depth. The biogeochemical data suggest that part of the N2 fixation could be linked to sulfate- and iron-reducing bacteria. Molecular analysis of the key functional marker gene for N2 fixation, nifH, confirmed the presence of sulfate- and iron-reducing diazotrophs. High N2 fixation further coincided with bioirrigation activity caused by burrowing macrofauna, both of which showed high rates at the shelf sites and low rates in deeper waters. However, statistical analyses proved that none of these processes and environmental variables were significantly correlated with benthic diazotrophy, which lead to the conclusion that either the key parameter controlling benthic N2 fixation in Mauritanian sediments remains unidentified or that a more complex interaction of control mechanisms exists. N2 fixation rates in Mauritanian sediments were 2.7 times lower than those from the anoxic Peruvian OMZ.

  8. Marshall Islands

    OpenAIRE

    World Bank

    2015-01-01

    This note aims to build understanding of the existing disaster risk financing and insurance (DRFI) tools in use in The Marshall Islands and to identify gaps where potential engagement could further develop financial resilience. The likelihood that a hazardous event will have a significant impact on the Marshall Islands has risen with the increasing levels of population and assets in the urban ...

  9. The fIXationof nitrogen in urea ammoniated wheat straw by means ...

    African Journals Online (AJOL)

    The fixation of nitrogen in urea ammoniated wheat straw by means of different acids was investigated in two laboratory trials and in a voluntary-intake trial with adult SA Mutton Merino wethers. Results from the laboratory trials showed hydrochloric and sulphuric acid to be superior to phosphoric and acetic acid as fixation ...

  10. Toward nitrogen neutral biofuel production.

    Science.gov (United States)

    Huo, Yi-Xin; Wernick, David G; Liao, James C

    2012-06-01

    Environmental concerns and an increasing global energy demand have spurred scientific research and political action to deliver large-scale production of liquid biofuels. Current biofuel processes and developing approaches have focused on closing the carbon cycle by biological fixation of atmospheric carbon dioxide and conversion of biomass to fuels. To date, these processes have relied on fertilizer produced by the energy-intensive Haber-Bosch process, and have not addressed the global nitrogen cycle and its environmental implications. Recent developments to convert protein to fuel and ammonia may begin to address these problems. In this scheme, recycling ammonia to either plant or algal feedstocks reduces the demand for synthetic fertilizer supplementation. Further development of this technology will realize its advantages of high carbon fixation rates, inexpensive and simple feedstock processing, in addition to reduced fertilizer requirements. Copyright © 2011 Elsevier Ltd. All rights reserved.

  11. Distribution and Magnitude of Dinitrogen Fixation in the Eastern Tropical North Pacific Oxygen Deficient Zone.

    Science.gov (United States)

    Selden, C.; Mulholland, M. R.; Widner, B.; Bernhardt, P. W.; Macías Tapia, A.; Jayakumar, A.

    2016-12-01

    The Eastern Tropical North Pacific Ocean (ETNP) hosts one of the world's three major open ocean oxygen deficient zones (ODZs). Hotspots for fixed nitrogen (N) loss processes, ODZs have classically been discounted as areas of significant dinitrogen (N2) fixation, the microbe-mediated reduction of N2 to ammonium (NH4+), which has historically been ascribed primarily to euphotic, nutrient-deplete tropical waters. Challenging this paradigm, active expression of nifH (the dinitrogen reductase structural gene) has recently been documented in the ETNP, Eastern Tropical South Pacific, and Arabian Sea ODZs, implying a closer coupling of fixed nitrogen input and loss processes than previously thought. Here, we report rates of N­2 fixation measured in the ETNP ODZ along vertical gradients of oxygen, light, and dissolved N concentrations. Detailed vertical profiles of N2 fixation rates and dissolved N concentrations made within the ODZ were compared with similar profiles from oxic waters outside the ODZ. In addition, different organic carbon sources were investigated as potential rate-limiting factors for N2 fixation in sub-euphotic waters. By establishing the magnitude and distribution of N­2 fixation in the ETNP ODZ, this study contributes to current understanding of N cycling in anoxic and aphotic waters, and serves to elucidate nuances in the global N budget, enabling more accurate biogeochemical modeling. Understanding these processes in present day ODZs is crucial for predicting how ongoing anthropogenic intensification of coastal ODZs will alter biogeochemical cycles in the future.

  12. Anterior fixation of the axis.

    Science.gov (United States)

    Traynelis, Vincent C; Fontes, Ricardo B V

    2010-09-01

    Although anterior fixation of the axis is not commonly performed, plate fixation of C2 is an important technique for treating select upper cervical traumatic injuries and is also useful in the surgical management of spondylosis. To report the technique and outcomes of C2 anterior plate fixation for a series of patients in which the majority presented with symptomatic degenerative spondylosis. Forty-six consecutive patients underwent single or multilevel fusions over a 7-year period; 30 of these had advanced degenerative disease manifested by myelopathy or deformity. Exposure was achieved with rostral extension of the standard anterior cervical exposure via careful soft tissue dissection, mobilization of the superior thyroid artery, and the use of a table-mounted retractor. It was not necessary to remove the submandibular gland, section the digastric muscle, or make additional skin incisions. Screws were placed an average of 4.6 mm (+/- 2.3 mm) from the inferior C2 endplate with a mean sagittal trajectory of 15.7 degrees (+/- 7.6 degrees). Short- and long-term procedure-related mortality was 4.4%, and perioperative morbidity was 8.9%. Patients remained intubated an average of 2.5 days following surgery. Dysphagia was initially reported by 15.2% of patients but resolved by the 8th postoperative week in all patients. Arthrodesis was achieved in all patients available for long-term follow-up. Multilevel fusions were not associated with longer hospitalization or morbidity. Anterior plate fixation of the axis for degenerative disease can be accomplished with acceptable morbidity employing an extension of the standard anterolateral route.

  13. Metagenomic profiling of a microbial assemblage associated with the California mussel: a node in networks of carbon and nitrogen cycling.

    Directory of Open Access Journals (Sweden)

    Catherine A Pfister

    2010-05-01

    Full Text Available Mussels are conspicuous and often abundant members of rocky shores and may constitute an important site for the nitrogen cycle due to their feeding and excretion activities. We used shotgun metagenomics of the microbial community associated with the surface of mussels (Mytilus californianus on Tatoosh Island in Washington state to test whether there is a nitrogen-based microbial assemblage associated with mussels. Analyses of both tidepool mussels and those on emergent benches revealed a diverse community of Bacteria and Archaea with approximately 31 million bp from 6 mussels in each habitat. Using MG-RAST, between 22.5-25.6% were identifiable using the SEED non-redundant database for proteins. Of those fragments that were identifiable through MG-RAST, the composition was dominated by Cyanobacteria and Alpha- and Gamma-proteobacteria. Microbial composition was highly similar between the tidepool and emergent bench mussels, suggesting similar functions across these different microhabitats. One percent of the proteins identified in each sample were related to nitrogen cycling. When normalized to protein discovery rate, the high diversity and abundance of enzymes related to the nitrogen cycle in mussel-associated microbes is as great or greater than that described for other marine metagenomes. In some instances, the nitrogen-utilizing profile of this assemblage was more concordant with soil metagenomes in the Midwestern U.S. than for open ocean system. Carbon fixation and Calvin cycle enzymes further represented 0.65 and 1.26% of all proteins and their abundance was comparable to a number of open ocean marine metagenomes. In sum, the diversity and abundance of nitrogen and carbon cycle related enzymes in the microbes occupying the shells of Mytilus californianus suggest these mussels provide a node for microbial populations and thus biogeochemical processes.

  14. Smaller Fixation Target Size Is Associated with More Stable Fixation and Less Variance in Threshold Sensitivity.

    Directory of Open Access Journals (Sweden)

    Kazunori Hirasawa

    Full Text Available The aims of this randomized observational case control study were to quantify fixation behavior during standard automated perimetry (SAP with different fixation targets and to evaluate the relationship between fixation behavior and threshold variability at each test point in healthy young participants experienced with perimetry. SAP was performed on the right eyes of 29 participants using the Octopus 900 perimeter, program 32, dynamic strategy. The fixation targets of Point, Cross, and Ring were used for SAP. Fixation behavior was recorded using a wearable eye-tracking glass. All participants underwent SAP twice with each fixation target in a random fashion. Fixation behavior was quantified by calculating the bivariate contour ellipse area (BCEA and the frequency of deviation from the fixation target. The BCEAs (deg2 of Point, Cross, and Ring targets were 1.11, 1.46, and 2.02, respectively. In all cases, BCEA increased significantly with increasing fixation target size (p < 0.05. The logarithmic value of BCEA demonstrated the same tendency (p < 0.05. A positive correlation was identified between fixation behavior and threshold variability for the Point and Cross targets (ρ = 0.413-0.534, p < 0.05. Fixation behavior increased with increasing fixation target size. Moreover, a larger fixation behavior tended to be associated with a higher threshold variability. A small fixation target is recommended during the visual field test.

  15. Effect of Chernobyl radionuclides accumulation on the photosynthetic processes and nitrogen metabolism of Lupines Luteus L

    International Nuclear Information System (INIS)

    Zabolotnyj, A.I.; Goncharova, N.V.; Domash, V.I.; Sheverdov, V.V.; Akadehmiya Navuk Belarusi, Minsk

    1995-01-01

    The 134 Cs, 137 Cs and chlorophyll content activity of photochemical reaction in chloroplasts and symbiotic nitrogen fixation in root modules, activity of neutral protease, BAPAse and trypsin inhibitors were investigated for seeds to yellow lupine (Lupines luteus L). The level of radioactive contamination induced a tendency to change the activity of photosynthetic reaction and nitrogen fixation, significant changes in a set of trypsin inhibitors were found in nature lupine seeds

  16. Variações qualitativas e quantitativas na microbiota do solo e na fixação biológica do nitrogênio sob diferentes manejos com soja Qualitative and quantitative changes in soil microbiota and biological nitrogen fixation under different soybean managements

    Directory of Open Access Journals (Sweden)

    Alan Alves Pereira

    2007-12-01

    Eutrudox, in Londrina, PR, Brazil. Treatments were a combination of a crop sequence (S (soybean/wheat and a crop rotation (R (lupin/maize/black oat/soybean/wheat/soybean/wheat/soybean, either under conventional tillage (CT or no-tillage (NT. Evaluations were performed when all systems were under the soybean cropping season, at full flowering. Amounts of microbial biomass carbon and nitrogen (MB-C and MB-N, respectively were 114 and 157 % higher in NT than in CT. Furthermore, the metabolic quotient (qCO2 was lower under NT, indicating higher metabolic efficiency of the soil microbes. These parameters were not affected by the crop sequence/rotation. Genetic diversity of the total soil bacterial community was higher under NT and lower in the CT system with crop sequence. Regarding the biological N2 fixation, it was found that plant biomass, total N and fraction of N-ureides in shoots, as well as nodule efficiency, were higher under NT. Genetic diversity of rhizobia was affected mainly by crop management and was higher under crop rotation, probably due to the greater number of plant species. However, crop rotation decreased the efficiency of the biological N2 fixation process, which may be related to more abundant N in the soil or to a lower selection pressure for efficient rhizobia. For soil microbes with specific functions, e.g., rhizobia, genetic diversity may therefore differ from functionality.

  17. Nitrogen fixation and growth response of Alnus rubra amended with low and high metal content biosolids Crescimento e fixação de nitrogênio por Alnus rubra cultivado sob fertilização com biosólidos com altos e baixos teores de metais

    Directory of Open Access Journals (Sweden)

    Linda S. Gaulke

    2006-08-01

    Full Text Available Forest application of biosolids offers a potential environmentally friendly alternative to landfilling. This two-year investigation was designed to analyze the effects of elevated soil metal concentration resulting from the land application of biosolids on the symbiotic, nitrogen (N fixing relationship between Alnus rubra Bong. (red alder and Frankia. High metal biosolids and a modern-day composted biosolid applied at high loading rates of 250, 500, and 1000 Mg ha-1, were used to represent a worst-case scenario for metal contamination. The high metal biosolids were obtained before the current regulations were formulated and had been lagooned prior to use in this study. Total cadmium (Cd, lead (Pb and zinc (Zn in the high metal biosolids were 45, 958, and 2623 mg kg-1 respectively. These metal concentrations are above current regulatory limits in the US. The compost was made using biosolids that are currently produced and had Cd, Pb and Zn of 0.8, 20 and 160 mg kg-1 respectively. Trees were harvested and analyzed for rate of N fixation (as measured by acetylene reduction activity, biomass, and foliar metals. Soils were analyzed for available N, total carbon and N, pH and total Cd, Pb and Zn. Rates of N fixation were not affected by soil amendment. In year 2, shoot biomass of trees grown in both the compost and high metal amendments were higher than the control. Shoot biomass increased with increasing amount of compost amendments, but decreased with increasing amount of high metal amendments. There was no relationship between soil metal concentration and plant biomass. Foliar Cd and Pb were below detection for all trees and foliar Zn increased with increasing amount of both compost and high metal amendment, with concentrations of 249 mg kg-1 for trees grown in the compost amendment and 279 mg kg-1 for the high metal amendment. The results from this study indicate that the growth of A. rubra benefited from both types of biosolids used in the study

  18. Fixação biológica e transferência de nitrogênio por leguminosas em pomar orgânico de mangueira e gravioleira Biological fixation and nitrogen transfer by three legume species in mango and soursop organic orchards

    Directory of Open Access Journals (Sweden)

    Gleicia Miranda Paulino

    2009-12-01

    Full Text Available O objetivo deste trabalho foi avaliar a fixação biológica de nitrogênio (FBN e a transferência do N derivado da FBN das espécies leguminosas - gliricídia (Gliricidia sepium, crotalária (Crotalaria juncea e feijão-guandu anão (Cajanus cajan - para um pomar orgânico de mangueira e gravioleira, pelo método da abundância natural de N. Foram avaliados os seguintes sistemas de cultivos consorciados: mangueira e gravioleira com gliricídia; mangueira e gravioleira com crotalária; mangueira e gravioleira com feijão-guandu; e a testemunha mangueira e gravioleira. Agliricídia apresentou maior potencial de FBN (80%, seguida da crotalária (64,5% e feijão-guandu (45%. Em dois cortes, a crotalária forneceu 149,5 kg ha-1 por ano de N, com 96,5kg derivados da FBN. A gliricídia com três podas anuais forneceu 56,4 e 80,3 kg ha-1 por ano de N, com 45 e 64 kg derivados da FBN, em dois anos consecutivos. A quantidade de N fornecida foi superior à demandada pela mangueira e gravioleira. Variações na abundância natural de 15N foram detectadas somente na gravioleira. Gliricídia e crotalária destacaram-se na transferência de N, com cerca de 22,5 e 40% do N fixado, respectivamente. A adubação verde com gliricídia possibilita o parcelamento do N, com melhor aproveitamento pelas espécies frutíferas.The objective of this work was to evaluate the biological nitrogen fixation (BNF and the N transfer derived from BNF of the legume species - Gliricidia sepium (gliricidia, Crotalaria juncea (sunnhemp and Cajanus cajan (pigeon pea - for an intercropped organic orchard with mango and soursop, through the 15N natural abundance method. The following intercropping systems were evaluated: mango and soursop with gliricidia; mango and soursop with sunnhemp; mango and soursop with pigeon pea; and mango and soursop as control. Gliricidia showed the highest BNF potential (80% , followed by sunnhemp (64.5% and pigeon pea (45%. After two sunnhemp prunes, 149

  19. Environmental and biogeochemical controls on N2 fixation in ombrotrophic peatlands

    Science.gov (United States)

    Zivkovic, T.; Moore, T. R.

    2017-12-01

    Northern peatlands have low atmospheric nitrogen (N) inputs and acquire N mostly via biological, microbially-driven N2-fixation. Little is known about rates and controls on N2-fixation in ombrotrophic bogs. We conducted two studies to test environmental and biogeochemical controls on N2-fixation. First, we used acetylene reduction assay (ARA) calibrated with 15N2 tracer to measure N2-fixation rates in three species of Sphagnum mosses along a hydrological gradient (beaver pond, hollow and hummock in bog margin and in bog) at Mer Bleue bog from June-October 2013 and May - November 2014. We tested the following controls: moisture availability, temperature, and PAR. The largest ARA rates throughout both seasons occurred in the pond in floating Sphagnum cuspidatum mats (50.3 ± 12.9 μmol m-2 d-1 Mean ± SE), which were up to 2.5 times larger than the rates found in the driest hummock site. There was a significant seasonal peak in both years in July and early August that coincided with the peak of the air temperature. In fact, 45% of the variance of N2 fixation rates over the two field seasons was explained by rain events, water table fluctuations and the surface peat temperature (multiple regression analysis, n = 539). Our results highlight the potential impact of climate change, namely negative effects due to potential droughts and positive effect of warming, on N2 fixation patterns in ombrotrophic peatlands. Secondly, we tested stoichiometric controls (Sphagnum tissue N and phosphorous (P) ratio) of N2-fixation. In a controlled environment, we selected eight study sites along a latitudinal gradient from temperate, boreal to subarctic zone in eastern Canada. We found that decreasing N:P ratio corresponded to increasing N2-fixation. N:P explained 65% of the variance in N2-fixation in hollows but only 20% in hummocks. Changes in neither N or P concentration alone explained the increase in N2-fixation better than N:P ratio. We interpret that the difference between

  20. Virtual Nitrogen Losses from Organic Food Production

    Science.gov (United States)

    Cattell Noll, L.; Galloway, J. N.; Leach, A. M.; Seufert, V.; Atwell, B.; Shade, J.

    2015-12-01

    Reactive nitrogen (Nr) is necessary for crop and animal production, but when it is lost to the environment, it creates a cascade of detrimental environmental impacts. The nitrogen challenge is to maximize the food production benefits of Nr, while minimizing losses to the environment. The first nitrogen footprint tool was created in 2012 to help consumers learn about the Nr losses to the environment that result from an individual's lifestyle choices. The nitrogen lost during food production was estimated with virtual nitrogen factors (VNFs) that quantify the amount of nitrogen lost to the environment per unit nitrogen consumed. Alternative agricultural systems, such as USDA certified organic farms, utilize practices that diverge from conventional production. In order to evaluate the potential sustainability of these alternative agricultural systems, our team calculated VNFs that reflect organic production. Initial data indicate that VNFs for organic grains and organic starchy roots are comparable to, but slightly higher than conventional (+10% and +20% respectively). In contrast, the VNF for organic vegetables is significantly higher (+90%) and the VNF for organic legumes is significantly lower (-90%). Initial data on organic meat production shows that organic poultry and organic pigmeat are comparable to conventional production (both <5% difference), but that the organic beef VNF is significantly higher (+30%). These data show that in some cases organic and conventional production are comparable in terms of nitrogen efficiency. However, since conventional production relies heavily on the creation of new reactive nitrogen (Haber-Bosch, biological nitrogen fixation) and organic production primarily utilizes already existing reactive nitrogen (manure, crop residue, compost), the data also show that organic production contributes less new reactive nitrogen to the environment than conventional production (approximately 70% less). Therefore, we conclude that on a local

  1. Comparison of inhibition of N2 fixation and ureide accumulation under water deficit in four common bean genotypes of contrasting drought tolerance.

    Science.gov (United States)

    Coleto, I; Pineda, M; Rodiño, A P; De Ron, A M; Alamillo, J M

    2014-05-01

    Drought is the principal constraint on world production of legume crops. There is considerable variability among genotypes in sensitivity of nitrogen fixation to drought, which has been related to accumulation of ureides in soybean. The aim of this study was to search for genotypic differences in drought sensitivity and ureide accumulation in common bean (Phaseolus vulgaris) germplasm that may be useful in the improvement of tolerance to water deficit in common bean. Changes in response to water deficit of nitrogen fixation rates, ureide content and the expression and activity of key enzymes for ureide metabolism were measured in four P. vulgaris genotypes differing in drought tolerance. A variable degree of drought-induced nitrogen fixation inhibition was found among the bean genotypes. In addition to inhibition of nitrogen fixation, there was accumulation of ureides in stems and leaves of sensitive and tolerant genotypes, although this was higher in the leaves of the most sensitive ones. In contrast, there was no accumulation of ureides in the nodules or roots of stressed plants. In addition, the level of ureides in the most sensitive genotype increased after inhibition of nitrogen fixation, suggesting that ureides originate in vegetative tissues as a response to water stress, probably mediated by the induction of allantoinase. Variability of drought-induced inhibition of nitrogen fixation among the P. vulgaris genotypes was accompanied by subsequent accumulation of ureides in stems and leaves, but not in nodules. The results indicate that shoot ureide accumulation after prolonged exposure to drought could not be the cause of inhibition of nitrogen fixation, as has been suggested in soybean. Instead, ureides seem to be produced as part of a general response to stress, and therefore higher accumulation might correspond to higher sensitivity to the stressful conditions.

  2. The marine nitrogen cycle: recent discoveries, uncertainties and the potential relevance of climate change

    OpenAIRE

    Voss, Maren; Bange, Hermann W.; Dippner, Joachim W.; Middelburg, Jack J.; Montoya, Joseph P.; Ward, Bess

    2013-01-01

    The ocean's nitrogen cycle is driven by complex microbial transformations, including nitrogen fixation, assimilation, nitrification, anammox and denitrification. Dinitrogen is the most abundant form of nitrogen in sea water but only accessible by nitrogen-fixing microbes. Denitrification and nitrification are both regulated by oxygen concentrations and potentially produce nitrous oxide (N2O), a climate-relevant atmospheric trace gas. The world's oceans, including the coastal areas and upwelli...

  3. Genome analysis of the freshwater planktonic Vulcanococcus limneticus sp. nov. reveals horizontal transfer of nitrogenase operon and alternative pathways of nitrogen utilization.

    Science.gov (United States)

    Di Cesare, Andrea; Cabello-Yeves, Pedro J; Chrismas, Nathan A M; Sánchez-Baracaldo, Patricia; Salcher, Michaela M; Callieri, Cristiana

    2018-04-16

    Many cyanobacteria are capable of fixing atmospheric nitrogen, playing a crucial role in biogeochemical cycling. Little is known about freshwater unicellular cyanobacteria Synechococcus spp. at the genomic level, despite being recognised of considerable ecological importance in aquatic ecosystems. So far, it has not been shown whether these unicellular picocyanobacteria have the potential for nitrogen fixation. Here, we present the draft-genome of the new pink-pigmented Synechococcus-like strain Vulcanococcus limneticus. sp. nov., isolated from the volcanic Lake Albano (Central Italy). The novel species Vulcanococcus limneticus sp. nov. falls inside the sub-cluster 5.2, close to the estuarine/marine strains in a maximum-likelihood phylogenetic tree generated with 259 marker genes with representatives from marine, brackish, euryhaline and freshwater habitats. V.limneticus sp. nov. possesses a complete nitrogenase and nif operon. In an experimental setup under nitrogen limiting and non-limiting conditions, growth was observed in both cases. However, the nitrogenase genes (nifHDK) were not transcribed, i.e., V.limneticus sp. nov. did not fix nitrogen, but instead degraded the phycobilisomes to produce sufficient amounts of ammonia. Moreover, the strain encoded many other pathways to incorporate ammonia, nitrate and sulphate, which are energetically less expensive for the cell than fixing nitrogen. The association of the nif operon to a genomic island, the relatively high amount of mobile genetic elements (52 transposases) and the lower observed GC content of V.limneticus sp. nov. nif operon (60.54%) compared to the average of the strain (68.35%) support the theory that this planktonic strain may have obtained, at some point of its evolution, the nif operon by horizontal gene transfer (HGT) from a filamentous or heterocystous cyanobacterium. In this study, we describe the novel species Vulcanococcus limneticus sp. nov., which possesses a complete nif operon for

  4. Overcoming fixation with repeated memory suppression.

    Science.gov (United States)

    Angello, Genna; Storm, Benjamin C; Smith, Steven M

    2015-01-01

    Fixation (blocks to memories or ideas) can be alleviated not only by encouraging productive work towards a solution, but, as the present experiments show, by reducing counterproductive work. Two experiments examined relief from fixation in a word-fragment completion task. Blockers, orthographically similar negative primes (e.g., ANALOGY), blocked solutions to word fragments (e.g., A_L_ _GY) in both experiments. After priming, but before the fragment completion test, participants repeatedly suppressed half of the blockers using the Think/No-Think paradigm, which results in memory inhibition. Inhibiting blockers did not alleviate fixation in Experiment 1 when conscious recollection of negative primes was not encouraged on the fragment completion test. In Experiment 2, however, when participants were encouraged to remember negative primes at fragment completion, relief from fixation was observed. Repeated suppression may nullify fixation effects, and promote creative thinking, particularly when fixation is caused by conscious recollection of counterproductive information.

  5. Polymeric media for tritium fixation. Supplement I

    International Nuclear Information System (INIS)

    Franz, J.A.; Burger, L.L.

    1976-01-01

    Procedures for the fixation of tritium as TH or THO in two different polymeric media are described. The complete procedure for THO fixation in a polyureylene-polyurethane polumer, including polymer molding procedures and leach tests is presented. The catalytic tritiation of polystyrene under very mild conditions using a rhodium catalyst is also described. Thermal stabilities and cost estimates for the polymers examined under this program are discussed. Organic polymers were found to have at