N2 fixation as a dominant new N source in the western tropical South Pacific Ocean (OUTPACE cruise)

Science.gov (United States)

Caffin, Mathieu; Moutin, Thierry; Foster, Rachel Ann; Bouruet-Aubertot, Pascale; Michelangelo Doglioli, Andrea; Berthelot, Hugo; Guieu, Cécile; Grosso, Olivier; Helias-Nunige, Sandra; Leblond, Nathalie; Gimenez, Audrey; Petrenko, Anne Alexandra; de Verneil, Alain; Bonnet, Sophie

2018-05-01

We performed nitrogen (N) budgets in the photic layer of three contrasting stations representing different trophic conditions in the western tropical South Pacific (WTSP) Ocean during austral summer conditions (February-March 2015). Using a Lagrangian strategy, we sampled the same water mass for the entire duration of each long-duration (5 days) station, allowing us to consider only vertical exchanges for the budgets. We quantified all major vertical N fluxes both entering (N2 fixation, nitrate turbulent diffusion, atmospheric deposition) and leaving the photic layer (particulate N export). The three stations were characterized by a strong nitracline and contrasted deep chlorophyll maximum depths, which were lower in the oligotrophic Melanesian archipelago (MA, stations LD A and LD B) than in the ultra-oligotrophic waters of the South Pacific Gyre (SPG, station LD C). N2 fixation rates were extremely high at both LD A (593 ± 51 µmol N m-2 d-1) and LD B (706 ± 302 µmol N m-2 d-1), and the diazotroph community was dominated by Trichodesmium. N2 fixation rates were lower (59 ± 16 µmol N m-2 d-1) at LD C, and the diazotroph community was dominated by unicellular N2-fixing cyanobacteria (UCYN). At all stations, N2 fixation was the major source of new N (> 90 %) before atmospheric deposition and upward nitrate fluxes induced by turbulence. N2 fixation contributed circa 13-18 % of primary production in the MA region and 3 % in the SPG water and sustained nearly all new primary production at all stations. The e ratio (e ratio = particulate carbon export / primary production) was maximum at LD A (9.7 %) and was higher than the e ratio in most studied oligotrophic regions (leading to N accumulation in the upper layer appears as a characteristic of the WTSP during the summer season.

Five decades of N2 fixation research in the North Atlantic Ocean

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Mar eBenavides

2015-06-01

Full Text Available Dinitrogen (N2 fixation (the reduction of atmospheric N2 to ammonium by specialized prokaryotic microbes, represents an important input of fixed nitrogen and contributes significantly to primary productivity in the oceans. Marine N2 fixation was discovered in the North Atlantic Ocean (NA in the 1960s. Ever since, the NA has been subject to numerous studies that have looked into the diversity and abundance of N2-fixing microbes (diazotrophs, the spatial and temporal variability of N2 fixation rates, and the range of physical and chemical variables that control them. The NA provides 10-25% of the globally fixed N2, ranking as the third basin with the largest N2 fixation inputs in the world’s oceans. This basin suffers a chronic depletion in phosphorus availability, more aeolian dust deposition than any other basin in the world’s oceans, and significant nutrient inputs from important rivers like the Amazon and the Congo. These characteristics make it unique in comparison with other oceanic basins. After five decades of intensive research, here we present a comprehensive review of our current understanding of diazotrophic activity in the NA from both a geochemical and biological perspective. We discuss the advantages and disadvantages of current methods, future perspectives, and questions which remain to be answered.

Dinitrogen fixation in aphotic oxygenated marine environments

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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.

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...

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

Possibility of high CO{sub 2} fixation rate by coral reef ecosystems

Energy Technology Data Exchange (ETDEWEB)

K. Yamada; Y. Suzuki; B.E. Casareto; H. Komiyama [Shinshu University, Tokida (Japan). Dept. of Fine Materials Engineering

2003-07-01

Previous net rates of CO{sub 2} fixation by coral reef ecosystems have been said to be nearly zero due to a balance between CO{sub 2} fixed by organic carbon production and CO{sub 2} released by both organic carbon decomposition and inorganic carbon formation. But this study, conducted in Bora Bay, Miyako Island, Japan showed net rates of about 7 gC m{sup -2} d{sup -1} inside a coral reef and on a coral reef. It was found by experiment that the photosynthetic rate of coral increased with the increase of the flow rate of seawater. The authors tried to calculate net primary production (= net rates of CO{sub 2} fixation) outside a coral reef with flow rate. A flow rate on the coral reef of the open seaside is much higher than that in a lagoon. As an example, the CO{sub 2} fixation rates at the flow rates of 6 and 30 cm/s are compared. When it is assumed that the length of the whole coral reef facing the ocean is 50,000 km and its width is 100 m, and the flow rate is 30cm/s, the CO{sub 2} fixation rate is calculated to be 6.3 x 10{sup 6} t-C/y (3.5g-C/m{sup 2}d). This value is 2.2 times higher than that at the flow rate of 6 cm/s. This fixation rate is only by the coral itself. It means that the CO{sub 2} fixation rate by coral reef ecosystems can be much higher and the magnitude for worldwide ecosystems can be in the order of 10{sup 6}-10{sup 7} t-C/y. 14 refs., 5 tabs.

Estimation of N2 fixation in winter and spring sown chickpea and in lentil grown under rainfed conditions using 15 N

International Nuclear Information System (INIS)

Kurdali, F.; Khalifa, Kh.; Al-Asfari, F.

1996-03-01

A field experiment was conducted under rainfed conditions to asses N 2 fixation in one cultivar of lentil and in two cultivars of chickpea (Gab 1 for winter and spring sowing, and Baladi for spring sowing). Moreover, the effect of P fertilizer on dry matter production, percentages and amounts of different N sources was studied using 15 N isotope dilution method. Wheat was used as a reference crop. The rate of N 2 fixation affected by several factors such as plant species, cultivar, date of sowing, P-fertilizer and the growing season. The highest amount of N 2 fixation obtained in winter sown chickpea was 126 Kg N ha -1 . Whereas, that of spring sowing for the same cultivar was 30 Kg N ha -1 . For Baladi cultivar, the highest amount of N-fixed was 55 Kg N ha -1 . While it was 104 Kg N ha -1 in lentil. Generally, N 2 -fixation affected positively by P-application. In the first growing season, N 2 -fixation increased from 33 to %58 by P application in spring sown chickpea (Baladi), and from 20 to %35 in spring sown chickpea (Gab 1). Whereas, no significant differences were observed upon P application in winter sown chickpea and in lentil. In the second growing season, P-fertilizer increased the percentage of N 2 fixation from 54 to %64 in winter sown chickpea, and from 45 to %64 in spring sown chickpea (Gab 1), and from 49 to %60 in spring sown chickpea (Baladi). While, in lentil it was from 66 to %72. The rate of N 2 fixation in winter sown chickpea was clearly higher than that of spring sowings. Moreover, this last one absorbed more N from the soil. Our results indicate the importance of winter sown chickpea in terms of N 2 fixation, seed yield and the reduction of soil N-uptake, besides a positive P-fertilizer response, especially when suitable rain fall occurs during the season. Moreover, the importance of these results from agronomical point of view was discussed. (author). 24 refs., 6 figs., 7 tabs

Nodulation, dry matter production and N2 fixation by fababean and chickpea as affected by soil moisture and potassium fertilizer

International Nuclear Information System (INIS)

Kurdali, F.; Al-Ain, F.; Al-Ahamma, M.

2003-01-01

The impact of three rates of K-fertilizer (0, 75, and 150 kg K 2 O/ha)on nodulation, dry matter production and N 2 fixation by fababean (Vicia faba L.) and chickpea (Cirer arietinum L.) was evaluated in a pot experiment. The plants were subjected to three soil moisture regimes (low, 45-50%; moderate, 55-60% and high 75-80% of field capacity). 15 N-isotope dilution method was employed to evaluate N 2 fixation using a non-fixing chickpea genotype as a reference crop. Water restriction drastically affected dry matter production, nodulation and N 2 fixation by both plant species. The negative effect of water stress on %N 2 fixed was more prominent in chickpea (11-58%) than in fababean (68-81%) under low and high % of field capacity, respectively. Plant species differed in their response to K-fertilizer as a mean to enhance growth and overcome the stress conditions. The higher level of K fertilizer increased both dry matter production and total N 2 fixed in fababean, but did not have any impact on chickpea. %N 2 fixed, however, appeared to be unaffected by K fertilizer as a mean of alleviating drought stress in both plant species. Therefore, it appears that, under the experimental conditions, the beneficial effect of potassium on water-stressed fababean resulted from stimulation the growth rather than improving the N 2 -fixation efficiency. However, under well-watered plants, a high requirement of the symbiotic system to potassium is needed to ensure and optimal growth and N 2 -fixation. (author)

Benthic N2 fixation in coral reefs and the potential effects of human-induced environmental change

Science.gov (United States)

Cardini, Ulisse; Bednarz, Vanessa N; Foster, Rachel A; Wild, Christian

2014-01-01

Tropical coral reefs are among the most productive and diverse ecosystems, despite being surrounded by ocean waters where nutrients are in short supply. Benthic dinitrogen (N2) fixation is a significant internal source of “new” nitrogen (N) in reef ecosystems, but related information appears to be sparse. Here, we review the current state (and gaps) of knowledge on N2 fixation associated with coral reef organisms and their ecosystems. By summarizing the existing literature, we show that benthic N2 fixation is an omnipresent process in tropical reef environments. Highest N2 fixation rates are detected in reef-associated cyanobacterial mats and sea grass meadows, clearly showing the significance of these functional groups, if present, to the input of new N in reef ecosystems. Nonetheless, key benthic organisms such as hard corals also importantly contribute to benthic N2 fixation in the reef. Given the usually high coral coverage of healthy reef systems, these results indicate that benthic symbiotic associations may be more important than previously thought. In fact, mutualisms between carbon (C) and N2 fixers have likely evolved that may enable reef communities to mitigate N limitation. We then explore the potential effects of the increasing human interferences on the process of benthic reef N2 fixation via changes in diazotrophic populations, enzymatic activities, or availability of benthic substrates favorable to these microorganisms. Current knowledge indicates positive effects of ocean acidification, warming, and deoxygenation and negative effects of increased ultraviolet radiation on the amount of N fixed in coral reefs. Eutrophication may either boost or suppress N2 fixation, depending on the nutrient becoming limiting. As N2 fixation appears to play a fundamental role in nutrient-limited reef ecosystems, these assumptions need to be expanded and confirmed by future research efforts addressing the knowledge gaps identified in this review. PMID:24967086

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)

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)

Use of 15N in evaluating symbiotic N2 fixation of field-grown soybeans

International Nuclear Information System (INIS)

Ham, G.E.

1978-01-01

Various methods have been used to estimate N 2 fixation by legumes (i.e. Kjeldahl N and the acetylene-ethylene assay). Recently 'Asub(N)' values by the legume and a non-nodulating crop using 15 N-labelled N fertilizer were used to quantitatively estimate the amount of N 2 fixed by legume crops growing under field conditions. The objective of this research was to evaluate Kjeldahl N procedures, the acetylene-ethylene assay and the 'Asub(N)' technique as estimators of N 2 fixation by field-grown soybeans. The 'Asub(N)' value concept provided a reliable estimate of N 2 fixation by soybeans which agreed with acetylene-ethylene measurements made weekly and the values compared favourably with Kjeldahl N measurements. (author)

Co-occurrence of methanogenesis and N{sub 2} fixation in oil sands tailings

Energy Technology Data Exchange (ETDEWEB)

Collins, C.E. Victoria [Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2G7 (Canada); Foght, Julia M. [Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9 (Canada); Siddique, Tariq, E-mail: tariq.siddique@ualberta.ca [Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2G7 (Canada)

2016-09-15

Oil sands tailings ponds in northern Alberta, Canada have been producing biogenic gases via microbial metabolism of hydrocarbons for decades. Persistent methanogenic activity in tailings ponds without any known replenishment of nutrients such as fixed nitrogen (N) persuaded us to investigate whether N{sub 2} fixation or polyacrylamide (PAM; used as a tailings flocculant) could serve as N sources. Cultures comprising mature fine tailings (MFT) plus methanogenic medium supplemented with or deficient in fixed N were incubated under an N{sub 2} headspace. Some cultures were further amended with citrate, which is used in oil sands processing, as a relevant carbon source, and/or with PAM. After an initial delay, N-deficient cultures with or without PAM produced methane (CH{sub 4}) at the same rate as N-containing cultures, indicating a mechanism of overcoming apparent N-deficiency. Acetylene reduction and {sup 15}N{sub 2} incorporation in all N-deficient cultures (with or without PAM) suggested active N{sub 2} fixation concurrently with methanogenesis but inability to use PAM as a N source. 16S rRNA gene pyrosequencing revealed little difference between archaeal populations regardless of N content. However, bacterial sequences in N-deficient cultures showed enrichment of Hyphomicrobiaceae and Clostridium members that might contain N{sub 2}-fixing species. The results are important in understanding long-term production of biogenic greenhouse gases in oil sands tailings. - Highlights: • Methanogenesis in oil sands tailings can occur under nitrogen depleted conditions. • {sup 15}N{sub 2} isotopic analysis reveals that indigenous microbes can fix N{sub 2} for microbial metabolism and methanogenesis. • 16S rRNA gene analysis suggests that members of Hyphomicrobiaceae and Clostridium may be involved in N{sub 2} fixation. • This is the first report that describes co-occurrence of methanogenesis and nitrogen fixation in oil sands tailings.

Studies in Sri Lanka on cowpea: N2 fixation, growth, yield, and effects on cereals

International Nuclear Information System (INIS)

Senaratne, R.; Dayatilake, G.A.; Subasinghe, S.

1998-01-01

The impact of seed inoculation and N-fertilization on nodulation, plant dry-matter production, and seed yield was studied through a series of field experiments with cultivars of cowpea. In some instances there were positive growth responses to applied N, indicating the potential to improve N 2 fixation and yields by combining compatible genotypes and bradyrhizobial strains. Beneficial residual effects on growth of subsequent maize could not be related to N 2 fixation by the preceding cowpea. Although there was no evidence of direct transfer of N from cowpea to intercropped maize, there was greater efficiency of use of N for total crop production during intercropping

Rates of Dinitrogen Fixation and the Abundance of Diazotrophs in North American Coastal Waters Between Cape Hatteras and Georges Bank

Science.gov (United States)

Mulholland, M.R.; Bernhardt, P. W.; Blanco-Garcia, J. L.; Mannino, A.; Hyde, K.; Mondragon, E.; Turk, K.; Moisander, P. H.; Zehr, J. P.

2012-01-01

We coupled dinitrogen (N2) fixation rate estimates with molecular biological methods to determine the activity and abundance of diazotrophs in coastal waters along the temperate North American Mid-Atlantic continental shelf during multiple seasons and cruises. Volumetric rates of N2 fixation were as high as 49.8 nmol N L(sup -1) d(sup -1) and areal rates as high as 837.9 micromol N m(sup -2) d(sup -1) in our study area. Our results suggest that N2 fixation occurs at high rates in coastal shelf waters that were previously thought to be unimportant sites of N2 fixation and so were excluded from calculations of pelagic marine N2 fixation. Unicellular N2-fixing group A cyanobacteria were the most abundant diazotrophs in the Atlantic coastal waters and their abundance was comparable to, or higher than, that measured in oceanic regimes where they were discovered. High rates of N2 fixation and the high abundance of diazotrophs along the North American Mid-Atlantic continental shelf highlight the need to revise marine N budgets to include coastal N2 fixation. Integrating areal rates of N2 fixation over the continental shelf area between Cape Hatteras and Nova Scotia, the estimated N2 fixation in this temperate shelf system is about 0.02 Tmol N yr(sup -1), the amount previously calculated for the entire North Atlantic continental shelf. Additional studies should provide spatially, temporally, and seasonally resolved rate estimates from coastal systems to better constrain N inputs via N2 fixation from the neritic zone.

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.

Measurement of N2 fixation in Sesbania aculeata and Sorghum bicolor L. grown in intercropping system using 15N isotopic dilution technique

International Nuclear Information System (INIS)

Kurdali, F.; Khalifa, K.; Janat, M.

2001-09-01

A field experiment on Sesbania aculeata and Sorghum bicolor grown in mono cropping and in inter cropping systems was conducted under non-saline conditions (soil EC e 0.16, water EC w 1dS/m) to evaluate dry matter production, total N yield, soil N uptake and N 2 -fixation using 15 N isotope dilution method. Three different row ratios of sesbania (ses) and sorghum (sor) were subjected in the inter cropping system (2ses: 1sot; 1ses: 1sor and 1ses: 2sor row ratio). Dry matter yield of sole sorghum was higher than that of sole sesbania, and it was similar to that produced by the inter cropping treatments. However, total N yield of sole sorghum was significantly the lowest, with no differences being obtained between sole sesbania and inter cropping treatments. The LERs of total N yield were, in all cases, higher than 1, reflecting a greater advantage of inter cropping system in terms of land use efficiency. Percentages of N 2 fixation in the inter cropped sesbania were considerably enhanced compared with the pure stand of sesbania. This was mainly attributed to the depletion of soil N resulting from the greater apparent competitiveness of sorghum for soil N, and consequently, a greater dependence of sesbania on N 2 fixation. However, the degree of the intraspecific competition for soil N uptake was affected by the proportion of crops in the mixture, and it was considerably reduced in the 2ses: 1sor row ratio. This was demonstrated when an equal depletion of soil and fertilizer N uptake occurred for both crops. We excluded in all-inter cropping treatments the possibility of N transfer from sesbania to sorghum. Row inter cropping, with crops grown in alternation of two rows of sesbania with one row of sorghum, seemed to be the most adequate row ratio in terms of total N yield, LER, N 2 -fixation and soil N uptake balance of the component crops. (author)

Use of low enriched 15N2 for symbiotic fixation tests

International Nuclear Information System (INIS)

Victoria, R.L.

1975-01-01

Gaseous atmospheres containing 15 N 2 with low enrichment were used to test symbiotic nitrogen fixation in beans (Phaseolus vulgari, L.). The tests of fixation in nodulated roots and the tests of fixation in the whole plant, in which the plants were placed inside a specially constructed growth chamber, gave positive results and suggest that the methodology used can be very helpfull in more detailed studies on symbiotic fixation. Samples of atmospheric air were purified by absorption of O 2 and CO 2 by two methods. The purified N 2 obtained was analysed and the results were compared. Samples of bean plant material were collected in natural conditions and analysed for 15 N natural variation. Several samples were prepared for 15 N isotopic analysis by two methods. The results obtained were compared. All samples were analysed in an Atlas-Varian Ch-4 model mass spectrometer, and the results were given in delta 15 N 0 / 00 variation in relation to a standard gas

Nodulation and N2 fixation effectiveness of Bradyrhizobium strains in symbiosis with Adzuki Bean, Vigna angularis

Directory of Open Access Journals (Sweden)

Dušica Delić

2010-04-01

Full Text Available In pot experiment, one isolate Knj from a Serbian soil, four strains of Bradyrhizobium japonicum and three strains of Bradyrhizobium spp. were examined for the effect on adzuki bean nodulation and effectiveness in symbiotic N2 fixation. All the tested strains produced root nodules in adzuki bean. Strains of B. japonicum showed high potential of N2 fixation, particularly 525 and 542. B. japonicum strains resulted 65-71% shoot dry weight and 99-138% total N content of uninoculated control with full N content (100%. No significant difference was found between the plants inoculated with Bradyrhizobium spp. strains and uninoculated control plants without N (40-42 and 42% shoot dry weight, respectively, which indicated symbiotic N2 fixation inactivity of the Bradyrhizobium spp. strains. Knj strain had the middle position (56% shoot dry weight. These data showed that B. japonicum 525 and 542 strains could be used in further investigations in order to apply them as inoculants in microbiological N fertilizers.

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

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

N2 fixation as a dominant new N source in the western tropical South Pacific Ocean (OUTPACE cruise

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M. Caffin

2018-05-01

Full Text Available We performed nitrogen (N budgets in the photic layer of three contrasting stations representing different trophic conditions in the western tropical South Pacific (WTSP Ocean during austral summer conditions (February–March 2015. Using a Lagrangian strategy, we sampled the same water mass for the entire duration of each long-duration (5 days station, allowing us to consider only vertical exchanges for the budgets. We quantified all major vertical N fluxes both entering (N2 fixation, nitrate turbulent diffusion, atmospheric deposition and leaving the photic layer (particulate N export. The three stations were characterized by a strong nitracline and contrasted deep chlorophyll maximum depths, which were lower in the oligotrophic Melanesian archipelago (MA, stations LD A and LD B than in the ultra-oligotrophic waters of the South Pacific Gyre (SPG, station LD C. N2 fixation rates were extremely high at both LD A (593 ± 51 µmol N m−2 d−1 and LD B (706 ± 302 µmol N m−2 d−1, and the diazotroph community was dominated by Trichodesmium. N2 fixation rates were lower (59 ± 16 µmol N m−2 d−1 at LD C, and the diazotroph community was dominated by unicellular N2-fixing cyanobacteria (UCYN. At all stations, N2 fixation was the major source of new N (> 90 % before atmospheric deposition and upward nitrate fluxes induced by turbulence. N2 fixation contributed circa 13–18 % of primary production in the MA region and 3 % in the SPG water and sustained nearly all new primary production at all stations. The e ratio (e ratio  =  particulate carbon export ∕ primary production was maximum at LD A (9.7 % and was higher than the e ratio in most studied oligotrophic regions (< 5 %, indicating a high efficiency of the WTSP to export carbon relative to primary production. The direct export of diazotrophs assessed by qPCR of the nifH gene in sediment traps represented up to

Measurement of N{sub 2} fixation in Sesbania aculeata and Sorghum bicolor L. grown in intercropping system using {sup 15}N isotopic dilution technique

Energy Technology Data Exchange (ETDEWEB)

Kurdali, F; Khalifa, K; Janat, M [Atomic Energy Commission, Damascus (Syrian Arab Republic). Dept. of Agriculture

2001-09-01

A field experiment on Sesbania aculeata and Sorghum bicolor grown in mono cropping and in inter cropping systems was conducted under non-saline conditions (soil EC{sub e} 0.16, water EC{sub w}1dS/m) to evaluate dry matter production, total N yield, soil N uptake and N{sub 2}-fixation using {sup 15}N isotope dilution method. Three different row ratios of sesbania (ses) and sorghum (sor) were subjected in the inter cropping system (2ses: 1sot; 1ses: 1sor and 1ses: 2sor row ratio). Dry matter yield of sole sorghum was higher than that of sole sesbania, and it was similar to that produced by the inter cropping treatments. However, total N yield of sole sorghum was significantly the lowest, with no differences being obtained between sole sesbania and inter cropping treatments. The LERs of total N yield were, in all cases, higher than 1, reflecting a greater advantage of inter cropping system in terms of land use efficiency. Percentages of N{sub 2} fixation in the inter cropped sesbania were considerably enhanced compared with the pure stand of sesbania. This was mainly attributed to the depletion of soil N resulting from the greater apparent competitiveness of sorghum for soil N, and consequently, a greater dependence of sesbania on N{sub 2} fixation. However, the degree of the intraspecific competition for soil N uptake was affected by the proportion of crops in the mixture, and it was considerably reduced in the 2ses: 1sor row ratio. This was demonstrated when an equal depletion of soil and fertilizer N uptake occurred for both crops. We excluded in all-inter cropping treatments the possibility of N transfer from sesbania to sorghum. Row inter cropping, with crops grown in alternation of two rows of sesbania with one row of sorghum, seemed to be the most adequate row ratio in terms of total N yield, LER, N{sub 2}-fixation and soil N uptake balance of the component crops. (author)

Co-occurrence of methanogenesis and N2 fixation in oil sands tailings.

Science.gov (United States)

Collins, C E Victoria; Foght, Julia M; Siddique, Tariq

2016-09-15

Oil sands tailings ponds in northern Alberta, Canada have been producing biogenic gases via microbial metabolism of hydrocarbons for decades. Persistent methanogenic activity in tailings ponds without any known replenishment of nutrients such as fixed nitrogen (N) persuaded us to investigate whether N2 fixation or polyacrylamide (PAM; used as a tailings flocculant) could serve as N sources. Cultures comprising mature fine tailings (MFT) plus methanogenic medium supplemented with or deficient in fixed N were incubated under an N2 headspace. Some cultures were further amended with citrate, which is used in oil sands processing, as a relevant carbon source, and/or with PAM. After an initial delay, N-deficient cultures with or without PAM produced methane (CH4) at the same rate as N-containing cultures, indicating a mechanism of overcoming apparent N-deficiency. Acetylene reduction and (15)N2 incorporation in all N-deficient cultures (with or without PAM) suggested active N2 fixation concurrently with methanogenesis but inability to use PAM as a N source. 16S rRNA gene pyrosequencing revealed little difference between archaeal populations regardless of N content. However, bacterial sequences in N-deficient cultures showed enrichment of Hyphomicrobiaceae and Clostridium members that might contain N2-fixing species. The results are important in understanding long-term production of biogenic greenhouse gases in oil sands tailings. Copyright © 2016 Elsevier B.V. All rights reserved.

Mesopelagic N2 Fixation Related to Organic Matter Composition in the Solomon and Bismarck Seas (Southwest Pacific.

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Mar Benavides

Full Text Available Dinitrogen (N2 fixation was investigated together with organic matter composition in the mesopelagic zone of the Bismarck (Transect 1 and Solomon (Transect 2 Seas (Southwest Pacific. Transparent exopolymer particles (TEP and the presence of compounds sharing molecular formulae with saturated fatty acids and sugars, as well as dissolved organic matter (DOM compounds containing nitrogen (N and phosphorus (P were higher on Transect 1 than on Transect 2, while oxygen concentrations showed an opposite pattern. N2 fixation rates (up to ~1 nmol N L-1 d-1 were higher in Transect 1 than in Transect 2, and correlated positively with TEP, suggesting a dependence of diazotroph activity on organic matter. The scores of the multivariate ordination of DOM molecular formulae and their relative abundance correlated negatively with bacterial abundances and positively with N2 fixation rates, suggesting an active bacterial exploitation of DOM and its use to sustain diazotrophic activity. Sequences of the nifH gene clustered with Alpha-, Beta-, Gamma- and Deltaproteobacteria, and included representatives from Clusters I, III and IV. A third of the clone library included sequences close to the potentially anaerobic Cluster III, suggesting that N2 fixation was partially supported by presumably particle-attached diazotrophs. Quantitative polymerase chain reaction (qPCR primer-probe sets were designed for three phylotypes and showed low abundances, with a phylotype within Cluster III at up to 103 nifH gene copies L-1. These results provide new insights into the ecology of non-cyanobacterial diazotrophs and suggest that organic matter sustains their activity in the mesopelagic ocean.

Epiphytic Cyanobacteria on Chara vulgaris Are the Main Contributors to N2 Fixation in Rice Fields

Science.gov (United States)

Ariosa, Yoanna; Quesada, Antonio; Aburto, Juan; Carrasco, David; Carreres, Ramón; Leganés, Francisco; Fernández Valiente, Eduardo

2004-01-01

The distribution of nitrogenase activity in the rice-soil system and the possible contribution of epiphytic cyanobacteria on rice plants and other macrophytes to this activity were studied in two locations in the rice fields of Valencia, Spain, in two consecutive crop seasons. The largest proportion of photodependent N2 fixation was associated with the macrophyte Chara vulgaris in both years and at both locations. The nitrogen fixation rate associated with Chara always represented more than 45% of the global nitrogenase activity measured in the rice field. The estimated average N2 fixation rate associated with Chara was 27.53 kg of N ha−1 crop−1. The mean estimated N2 fixation rates for the other parts of the system for all sampling periods were as follows: soil, 4.07 kg of N ha−1 crop−1; submerged parts of rice plants, 3.93 kg of N ha−1 crop−1; and roots, 0.28 kg of N ha−1 crop−1. Micrographic studies revealed the presence of epiphytic cyanobacteria on the surface of Chara. Three-dimensional reconstructions by confocal scanning laser microscopy revealed no cyanobacterial cells inside the Chara structures. Quantification of epiphytic cyanobacteria by image analysis revealed that cyanobacteria were more abundant in nodes than in internodes (on average, cyanobacteria covered 8.4% ± 4.4% and 6.2% ± 5.0% of the surface area in the nodes and internodes, respectively). Epiphytic cyanobacteria were also quantified by using a fluorometer. This made it possible to discriminate which algal groups were the source of chlorophyll a. Chlorophyll a measurements confirmed that cyanobacteria were more abundant in nodes than in internodes (on average, the chlorophyll a concentrations were 17.2 ± 28.0 and 4.0 ± 3.8 μg mg [dry weight] of Chara−1 in the nodes and internodes, respectively). These results indicate that this macrophyte, which is usually considered a weed in the context of rice cultivation, may help maintain soil N fertility in the rice field

Screening with nuclear techniques for yield and N2 fixation in mung bean in Thailand

International Nuclear Information System (INIS)

Boonkerd, N.; Wadisrisuk, P.; Siripin, S.; Murakami, T.; Danso, S.K.A.

1998-01-01

For a farmer to reap benefit from mung bean's (Vigna radiata) capacity to fix N 2 , the crop's requirement for N must come mainly from the atmosphere through symbiotic fixation in the root nodules. The aim of this study was to evaluate recommended mung-bean cultivars and advanced breeding lines, and identify high fixers. Preliminary investigations with the 15 N natural-abundance method indicated its utility for measuring N 2 fixation, and the examination of five recommended cultivars and two advanced breeding lines of mung using the 15 N-dilution method showed diversity in N 2 fixation and yield. More than 400 lines of mung bean were screened in soil in cement containers for growth, nodulation, N accumulation and N 2 fixation at 35 days after planting, with the natural-abundance method used to determine N 2 fixation. Genetic variability was observed for all characteristics. Estimates of fixed N ranged from 0-300 mg N/plant. Whereas some lines obtained N mainly from fixation, recommended cultivars apparently obtained their N mainly from soil. The data are discussed in terms of reliability of the 15 N natural-abundance method

Effects of ultraviolet radiation on photosynthetic performance and N2 fixation in Trichodesmium erythraeum IMS 101

Science.gov (United States)

Cai, Xiaoni; Hutchins, David A.; Fu, Feixue; Gao, Kunshan

2017-10-01

Biological effects of ultraviolet radiation (UVR; 280-400 nm) on marine primary producers are of general concern, as oceanic carbon fixers that contribute to the marine biological CO2 pump are being exposed to increasing UV irradiance due to global change and ozone depletion. We investigated the effects of UV-B (280-320 nm) and UV-A (320-400 nm) on the biogeochemically critical filamentous marine N2-fixing cyanobacterium Trichodesmium (strain IMS101) using a solar simulator as well as under natural solar radiation. Short exposure to UV-B, UV-A, or integrated total UVR significantly reduced the effective quantum yield of photosystem II (PSII) and photosynthetic carbon and N2 fixation rates. Cells acclimated to low light were more sensitive to UV exposure compared to high-light-grown ones, which had more UV-absorbing compounds, most likely mycosporine-like amino acids (MAAs). After acclimation under natural sunlight, the specific growth rate was lower (by up to 44 %), MAA content was higher, and average trichome length was shorter (by up to 22 %) in the full spectrum of solar radiation with UVR, than under a photosynthetically active radiation (PAR) alone treatment (400-700 nm). These results suggest that prior shipboard experiments in UV-opaque containers may have substantially overestimated in situ nitrogen fixation rates by Trichodesmium, and that natural and anthropogenic elevation of UV radiation intensity could significantly inhibit this vital source of new nitrogen to the current and future oligotrophic oceans.

Field evaluation of N2 fixation by mung bean in the Philippines, and residual effects on maize

International Nuclear Information System (INIS)

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

1998-01-01

Seventeen genotypes of mung bean (Vigna radiata) were screened for growth, yield, and symbiotic N 2 fixation during the late-dry (March-May) and early-dry (October-December) seasons of 1992 at the University of the Philippines at Los Banos (UPLB). The 15 N-dilution method was used to determine amounts of N fixed. Soil mineral N availability was higher (average 22 kg N/ha) in the late- than in the early-dry season (9.2 kg N/ha), and, possibly in consequence, vegetative growth was better in the late- than in the early-dry season; however, in contrast, seed yields were better in the latter. Cultivar Pagasa 5 had the highest value (52 kg N/ha) for fixed N in the late-dry season, whereas PAEC 3 had the highest value (70 kg N/ha) in the early-dry season; Accession 2041 had the lowest values in both seasons (33 and 26 kg N/ha, respectively). Genetic variability, albeit slight, was observed for total N fixed, but not for percent N derived from fixation (%Ndfa). Further field work at UPLB and at the Philippine Nuclear Research Institute (PNRI), Quezon City, investigated five mung genotypes, including three from the previous trials, for yield N 2 fixation and residual effects on subsequent maize (Zea mays). Estimates for %Ndfa and for amounts of N fixed ranged from 64 to 87% and 43 to 85 kg N/ha, respectively, at PNRI, and from 37 to 72% and 21 to 85 kg N/ha, respectively, at UPLB. The highest mung-bean seed yields obtained were 1.99 t/ha at PNRI and 0.86 t/ha at UPLB in the two locations. When maize was planted after mung, dry matter, seed yields and total N were consistently higher than when planted after maize or cotton, although most of the differences fell short of statistical significance. The data are discussed in terms of genetic diversity for yield and N 2 fixation in these soils, and potential to exploit mung-fixed N to improve cereal yields

Levels of daily light doses under changed day-night cycles regulate temporal segregation of photosynthesis and N2 Fixation in the cyanobacterium Trichodesmium erythraeum IMS101.

Science.gov (United States)

Cai, Xiaoni; Gao, Kunshan

2015-01-01

While the diazotrophic cyanobacterium Trichodesmium is known to display inverse diurnal performances of photosynthesis and N2 fixation, such a phenomenon has not been well documented under different day-night (L-D) cycles and different levels of light dose exposed to the cells. Here, we show differences in growth, N2 fixation and photosynthetic carbon fixation as well as photochemical performances of Trichodesmium IMS101 grown under 12L:12D, 8L:16D and 16L:8D L-D cycles at 70 μmol photons m-2 s-1 PAR (LL) and 350 μmol photons m-2 s-1 PAR (HL). The specific growth rate was the highest under LL and the lowest under HL under 16L:8D, and it increased under LL and decreased under HL with increased levels of daytime light doses exposed under the different light regimes, respectively. N2 fixation and photosynthetic carbon fixation were affected differentially by changes in the day-night regimes, with the former increasing directly under LL with increased daytime light doses and decreased under HL over growth-saturating light levels. Temporal segregation of N2 fixation from photosynthetic carbon fixation was evidenced under all day-night regimes, showing a time lag between the peak in N2 fixation and dip in carbon fixation. Elongation of light period led to higher N2 fixation rate under LL than under HL, while shortening the light exposure to 8 h delayed the N2 fixation peaking time (at the end of light period) and extended it to night period. Photosynthetic carbon fixation rates and transfer of light photons were always higher under HL than LL, regardless of the day-night cycles. Conclusively, diel performance of N2 fixation possesses functional plasticity, which was regulated by levels of light energy supplies either via changing light levels or length of light exposure.

Bacterial N2-fixation in mangrove ecosystems: insights from a diazotroph-mangrove interaction.

Science.gov (United States)

Alfaro-Espinoza, Gabriela; Ullrich, Matthias S

2015-01-01

Mangrove forests are highly productive ecosystems but represent low nutrient environments. Nitrogen availability is one of the main factors limiting mangrove growth. Diazotrophs have been identified as key organisms that provide nitrogen to these environments. N2-fixation by such organisms was found to be higher in the mangrove roots than in surrounding rhizosphere. Moreover, previous studies showed that mangroves grew better in the presence of N2-fixers indicating a potentially mutualistic relationship. However, the molecular signals and mechanisms that govern these interactions are still poorly understood. Here we present novel insights in the interaction of a diazotroph with a mangrove species to improve our understanding of the molecular and ecophysiological relationship between these two organisms under controlled conditions. Our results showed that Marinobacterium mangrovicola is a versatile organism capable of competing with other organisms to survive for long periods in mangrove soils. N2-fixation by this bacterium was up-regulated in the presence of mangrove roots, indicating a possible beneficial interaction. The increase in N2-fixation was limited to cells of the exponential growth phase suggesting that N2-fixation differs over the bacterial growth cycle. Bacterial transformants harboring a transcriptional nifH::gusA fusion showed that M. mangrovicola successfully colonized mangrove roots and simultaneously conducted N2-fixation. The colonization process was stimulated by the lack of an external carbon source suggesting a possible mutualistic relationship. M. mangrovicola represents an interesting genetically accessible diazotroph, which colonize mangrove roots and exhibit higher N2-fixation in the presence of mangrove roots. Consequently, we propose this microorganism as a tool to study molecular interactions between N2-fixers and mangrove plants and to better understand how changes in the environment could impact these important and relatively unknown

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

Use of low enriched /sup 15/N/sub 2/ for symbiotic fixation tests

Energy Technology Data Exchange (ETDEWEB)

Victoria, R L

1975-01-01

Gaseous atmospheres containing /sup 15/N/sub 2/ with low enrichment were used to test symbiotic nitrogen fixation in beans (Phaseolus vulgari, L.). The tests of fixation in nodulated roots and the tests of fixation in the whole plant, in which the plants were placed inside a specially constructed growth chamber, gave positive results and suggest that the methodology used can be very helpfull in more detailed studies on symbiotic fixation. Samples of atmospheric air were purified by absorption of O/sub 2/ and CO/sub 2/ by two methods. The purified N/sub 2/ obtained was analysed and the results were compared. Samples of bean plant material were collected in natural conditions and analysed for /sup 15/N natural variation. Several samples were prepared for /sup 15/N isotopic analysis by two methods. The results obtained were compared. All samples were analysed in an Atlas-Varian Ch-4 model mass spectrometer, and the results were given in delta /sup 15/N/sub 0///sup 00/ variation in relation to a standard gas.

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

Effects of ultraviolet radiation on photosynthetic performance and N2 fixation in Trichodesmium erythraeum IMS 101

Directory of Open Access Journals (Sweden)

X. Cai

2017-10-01

Full Text Available Biological effects of ultraviolet radiation (UVR; 280–400 nm on marine primary producers are of general concern, as oceanic carbon fixers that contribute to the marine biological CO2 pump are being exposed to increasing UV irradiance due to global change and ozone depletion. We investigated the effects of UV-B (280–320 nm and UV-A (320–400 nm on the biogeochemically critical filamentous marine N2-fixing cyanobacterium Trichodesmium (strain IMS101 using a solar simulator as well as under natural solar radiation. Short exposure to UV-B, UV-A, or integrated total UVR significantly reduced the effective quantum yield of photosystem II (PSII and photosynthetic carbon and N2 fixation rates. Cells acclimated to low light were more sensitive to UV exposure compared to high-light-grown ones, which had more UV-absorbing compounds, most likely mycosporine-like amino acids (MAAs. After acclimation under natural sunlight, the specific growth rate was lower (by up to 44 %, MAA content was higher, and average trichome length was shorter (by up to 22 % in the full spectrum of solar radiation with UVR, than under a photosynthetically active radiation (PAR alone treatment (400–700 nm. These results suggest that prior shipboard experiments in UV-opaque containers may have substantially overestimated in situ nitrogen fixation rates by Trichodesmium, and that natural and anthropogenic elevation of UV radiation intensity could significantly inhibit this vital source of new nitrogen to the current and future oligotrophic oceans.

"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.

Effects of macro nutrient concentration on biological N2 fixation by Azotobacter vinelandii ATCC 12837

International Nuclear Information System (INIS)

Liew Pauline Woan Ying; Nazalan Najimudin; Jong Bor Chyan; Latiffah Noordin; Khairuddin Abdul Rahim; Amir Hamzah Ahmad Ghazali

2010-01-01

The dynamic changes of biological N 2 fixation by Azotobacter vinelandii ATCC 12837 under the influence of various macro nutrients, specifically phosphorus (P) and potassium (K), was investigated. In this attempt, Oryza sativa L. var. MR 219 was used as the model plant. Results obtained showed changes in the biological N 2 fixation activities with different macro nutrient(s) manipulations. The research activity enables optimisation of macro nutrients concentration for optimal/ enhanced biological N 2 fixation by A. vinelandii ATCC 12837. (author)

Co-optimization of diesel fuel biodegradation and N2 fixation through the addition of particulate organic carbon

International Nuclear Information System (INIS)

Piehler, M.; Swistak, J.; Paerl, H.

1995-01-01

Petroleum hydrocarbon pollution in the marine environment is widespread and current bioremedial techniques are often not cost effective for small spills. The formulation of simple and inexpensive bioremedial methods could help reduce the impacts of frequent low volume spills in areas like marinas and ports. Particulate organic carbon (POC) was added to diesel fuel amended samples from inshore marine waters in the form of corn-slash (post-harvest leaves and stems), with and without inorganic nutrients (nitrate and phosphate). Biodegradation of diesel fuel ( 14 C hexadecane mineralization) and N 2 fixation were measured in response to the additions, The addition of POC was necessary for N 2 fixation and diesel fuel biodegradation to co-occur. The effects of diesel fuel and inorganic nutrient additions on N 2 fixation rates were not consistent, with both inhibitory and stimulatory responses to each addition observed. The highest observed diesel fuel biodegradation levels were in response to treatments that included inorganic nutrients. The addition of POC alone increased diesel fuel degradation levels above that observed in the control. In an attempt to determine the effect of the POC on the microbial community, the corn particles were observed microscopically using scanning electron microscopy and light microscopy with tetrazolium salt additions. The corn particles were found to have abundant attached bacterial communities and microscale oxygen concentration gradients occurring on individual particles. The formation of oxygen replete microzones may be essential for the co-occurrence of aerobic diesel fuel biodegradation and oxygen inhibited N2 fixation. Mesocosm experiments are currently underway to further examine the structure and function of this primarily heterotrophic system and to explore the potential contribution of N 2 fixation to the N requirements of diesel fuel biodegradation

Effects of N management on growth, N-2 fixation and yield of soybean

NARCIS (Netherlands)

Gan, YB; Stulen, [No Value; Posthumus, F; van Keulen, H; Kuiper, P

Soybean (Glycine max) is one of the most important food and cash crops in China. Although soybean has the capacity to obtain a large proportion of its N from N-2 fixation, it is common farmer's practice to apply an N top dressing to maximize grain yield. A field experiment was conducted to study the

Bilateral Laparoscopic Totally Extraperitoneal Repair Without Mesh Fixation

OpenAIRE

Dehal, Ahmed; Woodward, Brandon; Johna, Samir; Yamanishi, Frank

2014-01-01

Background and Objectives: Mesh fixation during laparoscopic totally extraperitoneal repair is thought to be necessary to prevent recurrence. However, mesh fixation may increase postoperative chronic pain. This study aimed to describe the experience of a single surgeon at our institution performing this operation. Methods: We performed a retrospective review of the medical records of all patients who underwent bilateral laparoscopic totally extraperitoneal repair without mesh fixation for ing...

Fixation strength of a polyetheretherketone femoral component in total knee arthroplasty.

Science.gov (United States)

de Ruiter, Lennert; Janssen, Dennis; Briscoe, Adam; Verdonschot, Nico

2017-11-01

Introducing polyetheretherketone (PEEK) polymer as a material for femoral components in total knee arthroplasty (TKA) could potentially lead to a reduction of the cemented fixation strength. A PEEK implant is more likely to deform under high loads, rendering geometrical locking features less effective. Fixation strength may be enhanced by adding more undercuts or specific surface treatments. The aim of this study is to measure the initial fixation strength and investigate the associated failure patterns of three different iterations of PEEK-OPTIMA ® implants compared with a Cobalt-Chromium (CoCr) component. Femoral components were cemented onto trabecular bone analogue foam blocks and preconditioned with 86,400 cycles of compressive loading (2600 N-260 N at 1 Hz). They were then extracted while the force was measured and the initial failure mechanism was recorded. Four groups were compared: CoCr, regular PEEK, PEEK with an enhanced cement-bonding surface and the latter with additional surface primer. The mean pull-off forces for the four groups were 3814 N, 688 N, 2525 N and 2552 N, respectively. The initial failure patterns for groups 1, 3 and 4 were the same; posterior condylar foam fracture and cement-bone debonding. Implants from group 2 failed at the cement-implant interface. This study has shown that a PEEK-OPTIMA ® femoral TKA component with enhanced macro- and microtexture is able to replicate the main failure mechanism of a conventional CoCr femoral implant. The fixation strength is lower than for a CoCr implant, but substantially higher than loads occurring under in-vivo conditions. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

Evaluation of isotopic dilution method for measuring N2 fixation in azolla: comparison with other methods

International Nuclear Information System (INIS)

Sah, R.N.; Goyal, S.S.; Rains, D.W.; Paige, D.F.

1989-01-01

An isotopic dilution method that overcomes the drawbacks of commonly used methods for measuring N 2 fixation by aquatic N‐fixers such as Azolla pinnata‐Anabaena azollae association (Azolla) is presented. The method was compared with 15 N2 gas (while maintaining CO 2 ) and the difference methods of measuring N 2 fixation. The isotopic dilution method was used for two conditions: a. For 15 N‐free growth medium, Azolla was pre‐enriched with 15 N, and N 2 fixation was determined by measuring the dilution of 15 N in the tissue. b. For the growth medium containing N, N2 fixation was determined by providing 15 N enriched ammonium sulfate in the growth medium and measuring 15 N to 14 N ratio in the tissue. An airtight chamber, necessary for 15 N 2 gas and acetylene reduction methods, was not representative of the growing environment of Azolla. Temperature in the airtight chamber was far from uniform and CO 2 was rapidly depleted. The isotopic dilution method is simpler, relatively inexpensive, subject to fewer errors and applicable to more diverse conditions, and yet was as accurate as 15 N2‐gas method. (author)

Comparison of cemented and uncemented fixation in total knee arthroplasty.

Science.gov (United States)

Brown, Thomas E; Harper, Benjamin L; Bjorgul, Kristian

2013-05-01

As a result of reading this article, physicians should be able to :1. Understand the rationale behind using uncemented fixation in total knee arthroplasty.2.Discuss the current literature comparing cemented and uncemented total knee arthroplasty3. Describe the value of radiostereographic analysis in assessing implant stability.4. Appreciate the limitations in the available literature advocating 1 mode of fixation in total knee arthroplasty. Total knee arthroplasty performed worldwide uses either cemented, cementless, or hybrid (cementless femur with a cemented tibia) fixation of the components. No recent literature review concerning the outcomes of cemented vs noncemented components has been performed. Noncemented components offer the potential advantage of a biologic interface between the bone and implants, which could demonstrate the greatest advantage in long-term durable fixation in the follow-up of young patients undergoing arthroplasty. Several advances have been made in the backing of the tibial components that have not been available long enough to yield long-term comparative follow-up studies. Short-term radiostereographic analysis studies have yielded differing results. Although long-term, high-quality studies are still needed, material advances in biologic fixation surfaces, such as trabecular metal and hydroxyapatite, may offer promising results for young and active patients undergoing total knee arthroplasty when compared with traditional cemented options. Copyright 2013, SLACK Incorporated.

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.

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

Symbiotic N2-fixation by the cover crop Pueraria phaseoloides as influenced by litter mineralization

DEFF Research Database (Denmark)

Vesterager, J.M.; Østerby, S.; Jensen, E.S.

1995-01-01

The perennial legume Pueraria phaseoloides is widely used as a cover crop in rubber and oil palm plantations. However, very little knowledge exists on the effect of litter mineralization from P. phaseoloides on its symbiotic N-2- fixation. The contribution from symbiotic N-2-fixation (Ndfa...

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

N2-fixation and seedling growth promotion of lodgepole pine by endophytic Paenibacillus polymyxa.

Science.gov (United States)

Anand, Richa; Grayston, Susan; Chanway, Christopher

2013-08-01

We inoculated lodgepole pine (Pinus contorta var. latifolia (Dougl.) Engelm.) with Paenibacillus polymyxa P2b-2R, a diazotrophic bacterium previously isolated from internal stem tissue of a naturally regenerating pine seedling to evaluate biological nitrogen fixation and seedling growth promotion by this microorganism. Seedlings generated from pine seed inoculated with strain P2b-2R were grown for up to 13 months in a N-limited soil mix containing 0.7 mM available N labeled as Ca((15)NO3)2 to facilitate detection of N2-fixation. Strain P2b-2R developed a persistent endophytic population comprising 10(2)-10(6) cfu g(-1) plant tissue inside pine roots, stems, and needles during the experiment. At the end of the growth period, P2b-2R had reduced seedling mortality by 14 % and (15)N foliar N abundance 79 % and doubled foliar N concentration and seedling biomass compared to controls. Our results suggest that N2-fixation by P. polymyxa enhanced growth of pine seedlings and support the hypothesis that plant-associated diazotrophs capable of endophytic colonization can satisfy a significant proportion of the N required by tree seedlings growing under N-limited conditions.

Inducible hydrogenase in cyanobacteria enhances N/sub 2/ fixation. [Nostoc, anabaena

Energy Technology Data Exchange (ETDEWEB)

Tel-Or, E.; Luijk, L.W.; Packer, L.

1977-06-01

Whether hydrogenase is activated or induced, we found no evidence for activation of either consumption or production of H/sub 2/ in aerobically-grown cultures but both of these activities increased 5--20-fold when cultures are grown under H/sub 2/ gas. On the other hand, hydrogenase-catalyzed consumption of H/sub 2/ is stimulated by light and/or light plus CO/sub 2/ in hydrogenase-induced cultures. Nitrogenase activity appears to be induced in cultures grown under H/sub 2/. Studies unambiguously establish that in H/sub 2/-induced cultures hydrogenase manifests a cooperativity with nitrogenase. In the presence of H/sub 2/ the activity of nitrogenase is stimulated 3--5-fold such that rates of about 3 ..mu..mol N/sub 2/ fixed/mg chlorophyll/h are obtained if the method of Peterson and Burris is used to convert acetylene reduction data to equivalents of /sup 15/N/sub 2/ fixation to ammonia.

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

Nonphotosynthetic CO2 fixation by alfalfa (Medicago sativa L.) roots and nodules

International Nuclear Information System (INIS)

Anderson, M.P.; Heichel, G.H.; Vance, C.P.

1987-01-01

The dependence of alfalfa (Medicago sativa L.) root and nodule nonphotosynthetic CO 2 fixation on the supply of currently produced photosynthate and nodule nitrogenase activity was examined a various times after phloem-girdling and exposure of nodules to Ar:O 2 . Phloem-girdling was effected 20 hours and exposure to Ar:O 2 was effected 2 to 3 hours before initiation of experiments. Nodule and root CO 2 fixation rates of phloem-girdled plants were reduced to 38 and 50%, respectively, of those of control plants. Exposure to Ar:O 2 decreased nodule CO 2 fixation rates to 45%, respiration rates to 55%, and nitrogenase activities to 51% of those of the controls. The products of nodule CO 2 fixation were exported through the xylem to the shoot mainly as amino acids within 30 to 60 minutes after exposure to 14 CO 2 . In contrast to nodules, roots exported very little radioactivity, and most of the 14 C was exported as organic acids. The nonphotosynthetic CO 2 fixation rate of roots and nodules averaged 26% of the gross respiration rate, i.e. the sum of net respiration and nonphotosynthetic CO 2 assimilation. Nodules fixed CO 2 at a rate 5.6 times that of roots, but since nodules comprised a small portion of root system mass, roots accounted for 76% of the nodulated roots system CO 2 fixation. The results indicate that nodule CO 2 fixation in alfalfa is associated with N assimilation

N resource of grasses and N2-fixation of alfalfa in mono-culture and mixture

International Nuclear Information System (INIS)

Zhu Shuxiu

1992-01-01

The N behavior in alfalfa and gramineous forage grasses, tall fescue, siberian wild rye, wheat grass and awnless brome were studied in potting and pasture experiments in 1986-1988 by using 15 N isotope dilution technique. Comparison was made between the mixed culture and mono-culture. The % Ndff and %Ndfs of grasses were decreased by 14.19% and 20.76% respectively, while %Ndfa of alfalfa was increased by 20.22% in mixed culture as compared with mono-culture. The 15 N and soil N uptake data revealed that this enhancement was largely due to a lower competitive ability for soil N by alfalfa than by grass in mixed stands, causing the alfalfa to depend more on atmospheric N 2 fixation. 20.62%of N of grasses in mixed culture was from the N 2 -fixation by alfalfa, causing N level in root-sphere of alfalfa decreasing, which was considered to be one of the reasons that %Ndfa increased in mixed culture. N transfer may be carried out by the decomposition of roots and nodules of alfalfa plants

Exploring the Boundaries of N2-Fixation in Cereals and Grasses: A Hypothetical and Experimental Framework

NARCIS (Netherlands)

Giller, K.E.; Merckx, R.

2003-01-01

Despite more than 40 years of research on free-living and endophytic bacteria associated with cereals and grasses, conclusive examples of impacts of non-symbiotic N2-fixation in agriculture are lacking. All available methods for measurement of N2-fixation associated with cereals and grasses have

Measurement of N2 fixation in Sesbania aculeata pers. and Sorghum bicolor L. grown in intercropping system, using sup 1 sup 5 N isotopic dilution technique. 1: Field evaluation under non-saline conditions

International Nuclear Information System (INIS)

Kurdali, F.; Khalifa, K.; Janat, M.

2002-01-01

A field experiment on Sesbania aculeata and Sorghum bicolor grown in mono cropping and in inter cropping systems was conducted under non-saline conditions (soil EC sub e 0.16, water EC sub w 1 ds/m/m) to evaluate dry matter production, total N yield, soil N uptake and N sub 2 -fixation using sup 1 sup 5 N isotope dilution method. Three different row ratios of sesbania (ses) and sorghum (sor) were subjected in the inter cropping system (2 ses: 1 sor; 1 ses: 1 sor and 1 ses: 2 sor row ratio). Dry matter yield of sole sorghum was higher than that of sole sesbania, and it was similar to that produced by the inter cropping treatments. However, total N yield of sole sorghum was significantly the lowest, with no differences being obtained between sole sesbania and inter cropping treatments. The LERs of total N yield were, in all cases, higher than 1, reflecting a greater advantage of inter cropping system in terms of land use efficiency. Percentages of N sub 2 fixation in the inter cropped sesbania were considerably enhanced compared with the pure stand of sesbania. This was mainly attributed to the depletion of soil N resulting from the greater apparent competitiveness of sorghum for soil N, and consequently, a greater dependence of sesbania on N sub 2 fixation. However, the degree of the intraspecific competition for soil N uptake was affected by the proportion of crops in the mixture, and it was considerably reduced in the 2 ses: 1 sor row ratio. This was demonstrated when an equal depletion of soil and fertilizer N uptake occurred for both crops. We excluded in all-inter cropping treatments the possibility of N transfer from sesbania to sorghum. Row inter cropping, with crops grown in alternation of two rows of sesbania with one row of sorghum, seemed to be the most adequate row ratio in terms of total N yield, LER, N sub 2 -fixation and soil N uptake balance of the component crops. (author)

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.

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.

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

Evaluation of yield and N2 fixation of mutant lines of groundnut in Malaysia

International Nuclear Information System (INIS)

Rusli, I.; Harun, A.R.; Rahman, K.A.; Shamsuddin, S.; Rahim, K.A.; Danso, S.K.A.

1998-01-01

The 15 N-dilution technique was used to evaluate N 2 fixation in groundnut (Arachis hypogaea L.) in three field trials of cultivars Matjan and V-13 (parents), their selected mutant lines, and a other local and foreign genotypes. Matjan mutant MJ/40/42 consistently produced the highest pod yields, at above 4 t ha -1 , 14-22% higher yields than the parent. In contrast, none of the V-13 mutants had consistently better yields than the parent. The mutant lines did not show consistent agronomic performance from year to year. Total dry matter yield did not correlate with pod yield, and pod yield did not correlate with amount of N fixed

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.

Free-air CO2 enrichment (FACE) reduces the inhibitory effect of soil nitrate on N2 fixation of Pisum sativum.

Science.gov (United States)

Butterly, Clayton R; Armstrong, Roger; Chen, Deli; Tang, Caixian

2016-01-01

Additional carbohydrate supply resulting from enhanced photosynthesis under predicted future elevated CO2 is likely to increase symbiotic nitrogen (N) fixation in legumes. This study examined the interactive effects of atmospheric CO2 and nitrate (NO3(-)) concentration on the growth, nodulation and N fixation of field pea (Pisum sativum) in a semi-arid cropping system. Field pea was grown for 15 weeks in a Vertosol containing 5, 25, 50 or 90 mg NO3(-)-N kg(-1) under either ambient CO2 (aCO2; 390 ppm) or elevated CO2 (eCO2; 550 ppm) using free-air CO2 enrichment (SoilFACE). Under aCO2, field pea biomass was significantly lower at 5 mg NO3(-)-N kg(-1) than at 90 mg NO3(-)-N kg(-1) soil. However, increasing the soil N level significantly reduced nodulation of lateral roots but not the primary root, and nodules were significantly smaller, with 85% less nodule mass in the 90 NO3(-)-N kg(-1) than in the 5 mg NO3(-)-N kg(-1) treatment, highlighting the inhibitory effects of NO3(-). Field pea grown under eCO2 had greater biomass (approx. 30%) than those grown under aCO2, and was not affected by N level. Overall, the inhibitory effects of NO3(-) on nodulation and nodule mass appeared to be reduced under eCO2 compared with aCO2, although the effects of CO2 on root growth were not significant. Elevated CO2 alleviated the inhibitory effect of soil NO3(-) on nodulation and N2 fixation and is likely to lead to greater total N content of field pea growing under future elevated CO2 environments. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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

Breeding for high N2 fixation in groundnut and soybean in Viet Nam

International Nuclear Information System (INIS)

Nguyen Xuan Hong

1998-01-01

Groundnut (Arachis hypogaea L.) and soybean (Glycine max (L.) Mer.) are grown mainly on two types of soil in Viet Nam: coastal-sandy and upland-degraded soils. These soils are deficient in N, and considering that fertilizer N is not only costly to farmers but also a threat to the environment, it is important to maximize productivity by exploiting the ability of these legumes to fix N 2 symbiotically in their root nodules. We initiated programmes of breeding and selection to combine high N 2 fixation and high grain-yielding capacity. In the spring of 1992, breeding lines of groundnut and soybean were tested under greenhouse conditions for varietal differences in the capacity to fix N 2 using the acetylene reduction assay and the 15 N-dilution technique, with upland rice as reference plants. Varietal differences were found in nitrogenase activity, and percent N derived from fixation (%Ndfa) ranged from 11 to 63% for groundnut and from 9 to 79% for soybean. Field experiments in the autumn-winter season of 1992 again revealed significant varietal differences; %Ndfa ranged from 36 to 56% for groundnut and from 28 to 58% for soybean. Gamma-irradiated seeds of soybean were propagated in bulk from M 1 to M 4 . Five high-yielding mutant lines of both species were selected from the M 5 populations, and N 2 fixation was estimated using the 15 N-dilution technique. The average values for %Ndfa of the mutants were 55 and 57%, significant improvements over the parent-cultivar values of 25 and 29% for soybean and groundnut, respectively

Selection and breeding of grain legumes in Australia for enhanced nodulation and N2 fixation

International Nuclear Information System (INIS)

Herridge, D.F.; Holland, J.F.; Rose, I.A.; Redden, R.J.

1998-01-01

During the period 1980-87, the areas sown to grain legumes in Australia increased dramatically, from 0.25 Mha to 1.65 Mha. These increases occurred in the western and southern cereal belts, but not in the north which N continued to be supplied by the mineralization of soil organic matter. Therefore, there was a need to promote the use of N 2 -fixing legumes in the cereal-dominated northern cropping belt. Certain problems had to be addressed before farmers would accept legumes and change established patterns of cropping. Here we describe our efforts to improve N 2 fixation by soybean, common bean and pigeon pea. Selection and breeding for enhanced N 2 fixation of soybean commenced at Tamworth in 1980 after surveys of commercial crops indicated that nodulation was sometimes inadequate, particularly on new land, and that the levels of fixed-N inputs were variable and often low. Similar programmes were established in 1985 (common bean) and 1988 (pigeon bean). Progress was made in increasing N 2 fixation by these legumes towards obtaining economic yields without fertilizer N and contributing organic N for the benefit of subsequent cereal crops

Biological N2-FIXATION and Mineral N-Fertilization Effects on Soybean (Glicine max L. Merr.) Yield Under Temperate Climate Conditions

Science.gov (United States)

László Phd, M., ,, Dr.

2009-04-01

Summary In a nitrogen fertilization experiment set up on slightly calcareous Ramann sandy- loam brown forest soil studies were made on the effect of nitrogen (N) x Rhizobium japonicum inoculation (I) x variety (V) interactions on soybean yield in Hungary. The agrochemical parameters of the ploughed layer of soil were as follows: humus 1.3%, CaCO3 2.1%, silty clay 27%, pH (H2O) 7.2, pH (KCl) 7.0. The experiment involved 4N x 3I x 3V = combinations in 4 replications, giving a total of 144 plots. The most important results can be summarized as follows: (a.) 0, (b.) 100, (c.) 150 and (d.) 200 kg ha-1 year-1 of nitrogen application (a.) inoculation effect was maximum at 1 kg t-1 Nitrofix, (b.) yields were linearly and inversely related to the rate of Nitrofix, (c.) presence of any amount of Nitrofix has been a negative effect on yield and (d.) Nitrofix 1 kg t-1 was showed the best results. Both biological N2 fixation (BNF) and nitrate (NO3-) utilization by mineral nitrogen fertilizer (MNF) input were essential for maximum soybean yield. Introduction Nitrogen is the most frequently deficient nutrient in crop production therefore, most cropping system require N- inputs (Johnston 2000, Márton 2000, 2001). Many soursces are available for use in supplying N to crops (Kováts et al. 1985). In addition to from N2 fixation by leguminous crops can supply sufficient N for optimum crop production (Wilcox 1987, Kádár & Márton 1999, Márton & Kádár 1998, László & Jose 2001, László et al. 2001). Understanding the behaviour of N in the soil is essential for maximizing agricultural productivity and profitability while reducing the impacts of N fertilization on the environment. Managing the delicate balance in the soil N- supply in order to meet this goals. Nowadays there is an essential need to use nitrogen to achieve both economic yields and to produce enough food. Because the only way for agriculture to keep pace with population (world's population now exceeds 6 billion and

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

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...

N2 Fixation by Grain Legume Varieties as Affected By Rhizobia ...

African Journals Online (AJOL)

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[*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.

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)

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.

15N enrichment of soil NH4+-N as an alternative non-N2-fixing reference for assessing varietal differences in N2 fixation of rice

International Nuclear Information System (INIS)

Shrestha, R.K.; Ladha, J.K.

1996-01-01

A pot experiment in the greenhouse was conducted to assess the usefulness of 15 N enrichment of soil NH 4 + -N as an alternative to a non-fixing reference plant to determine varietal differences in N 2 fixation among rice varieties. Diverse rice genotypes were grown in a 15 N stabilized soil obtained after 6 wk of application under flooded conditions. Atom % 15 N excess of soil NH 4 + -N was decreased exponentially with amount of N mineralized (r=99). Close agreement was observed between the 15 N enrichment of reference rice plant and 15 N enrichment of KCl extractable NH 4 + -N from unplanted pots maintained in the greenhouse. Whole plant atom % 15 N excess was inversely correlated within growth duration. Therefore, it was necessary to calculate Ndfa within growth duration. Ndfa estimated within the growth duration using 15 N enrichment of soil NH 4 + -N and reference rice genotype correlated almost perfectly (r=998). Thus the study demonstrated the potential of using 15 N enrichment of soil NH 4 + -N as a non-N 2 fixing reference for reliable estimate of biological nitrogen fixation by nonlegumes under flooded conditions. (author)

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

Science.gov (United States)

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

The Effects of SO2 on N2-Fixation, Carbon Partitioning, and Yield Components in Snapbean, Phaseolus Vulgaris L.

OpenAIRE

Griffith, Stephen M.

1983-01-01

The primary air pollutant sulfur dioxide has been shown to affect plant biochemistry and physiology, although very little is known about its effects on N2-fixation in legumes. This study was designed to determine if N2-fixation, carbon partitioning , and productivity are affected under short term low level, so2 exposures. Greenhouse grown snapbeans (P has eo lus vulgaris L. cv. Ear l iwax), 29 days from planting, were exposed to 0.0, 0.4, and 0.8 parts per million sulfur dioxide for 4 hour...

Evaluation for dinitrogen fixation of alfalfa in field based on δ15N value

International Nuclear Information System (INIS)

Yao Yunyin; Chen Ming; Zhang Xizhong

1992-12-01

The dinitrogen fixation rate of alfalfa was estimated grown in pot and field experiments. β values (isotope fraction factor) of 7 cultivars of alfalfa (Medicago sativa L.) and white clover (Trifolium repens L.) grown in N-free liquid culture medium were examined. Variations in the δ 15 N values of varieties of alfalfa at growing seasons and forage grasses grown under various conditions were measured. %Ndfa of alfalfa was estimated using the natural 15 N abundance method, 15 N isotope dilution method and total N difference, and their accuracy was compared

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)

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

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...

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.

Equally good fixation of cemented and uncemented cups in total trapeziometacarpal joint prostheses. A randomized clinical RSA study with 2-year follow-up.

Science.gov (United States)

Hansen, Torben Baek; Stilling, Maiken

2013-02-01

Cup failure is a recognized problem in total trapeziometacarpal (TM) joint prostheses; it may be related to poor fixation, which can be revealed by radiostereometric analysis (RSA). We compared the early implant migration of cemented trapezium cups to that of uncemented screw cups. In a prospective, parallel-group, randomized patient-blinded clinical trial, we included 32 hands in 28 patients (5 males) with a mean age of 58 (40-77) years and with Eaton stage-2 or -3 osteoarthritis of the trapeziometacarpal joint. Patients were randomized to surgery with a cemented DLC all-polyethylene cup (C) (n = 16) or an uncemented hydroxyapatite-coated chrome-cobalt Elektra screw cup (UC) (n = 16). Uncemented cups were inserted without threading of the bone. Stereoradiographs for evaluation of cup migration (primary effect size) and DASH and pain scores were obtained during 2 years of follow-up. The 2-year total translation (TT) was similar (p = 0.2): 0.24 mm (SD 0.10) for the C (n = 11) and 0.19 mm (SD 0.16) for the UC (n = 11). Variances were similar (p = 0.4). Judged by RSA, 2 UC cups and 1 C cup became loose (TT > 1 mm). Both UC cups were found to be loose at revision. Grip strength, pain, and DASH scores were similar between groups at all measurement points. Early implant fixation and clinical outcome were equally good with both cup designs. This is the first clinical RSA study on trapezium cups, and the method appears to be clinically useful for detection of loose implants.

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.

Estimating legume N-2 fixation in grass-clover mixtures of a grazed organic cropping system using two N-15 methods

DEFF Research Database (Denmark)

Vinther, F.P.; Jensen, E.S.

2000-01-01

The input of Nitrogen (N) through symbiotic N-2 fixation (SNF) in grass-clover mixtures was determined in an organic cropping. system for grazing during 3 years. The mixture of perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) was established by undersowing in spring...... barley (Hordeum vulgare L.) and maintained subsequently for two production years. Dinitrogen fixation was determined using the N-15 isotope dilution techniques and two labelling procedures. Using either pre-labelling of the soil with immobilisation of the N-15 by addition of a carbon source before...

Measurement of N2 fixation in Sesbania aculeata pers. and Sorghum bicolor L. grown in intercropping system, under saline conditions, using 15N isotopic dilution technique

International Nuclear Information System (INIS)

Kurdali, F.; Khalifa, K.; Janat, M.

2001-09-01

A field experiment was conducted under saline conditions (soil EC e 15, water EC w 8 dS/m/m) to evaluate the performance of sole crops and inter crops of Sesbania aculeata and Sorghum bicolor (1:1 row ratio) in terms of dry matter production, total N yield, soil N uptake and N 2 -fixation using 15 N isotope dilution method. Dry matter yield in sole crop of sesbania was significantly higher that that of sole sorghum; whereas, that of the inter cropping was significantly lower than sole sesbania, but was similar to that produced by sole sorghum. Total nitrogen yield in sole sesbania was four-fold than that accumulated in sole sorghum, whereas, that of mixed cropping was 2.6 fold compared to that of sole sorghum. The LER of total N yield was higher than 1 reflecting a greater advantage of inter cropping system in terms of land use efficiency. The proportion of N derived from N 2 fixation (%Ndfa) in the sesbania was increased from 63 to 79%, for sole and inter cropping system, respectively. There was no evidence of a significant transfer of N from the sesbania to the sorghum. Results on the relative growth of plants on saline soil compared with non-saline soil clearly demonstrated that sesbania was more salt tolerant than the sorghum. soil nitrogen uptake by plants, particularly in sorghum, was adversely affected by salinity. However, amounts of N 2 fixed by sole sesbania grown is saline soil was close or even higher than on non-saline soil. The use of inter cropping systems of legumes and non-legumes could be a promising agricultural approach to reutilize wasted lands, after a careful selection of appropriate tolerant genotypes to prevailing saline conditions. (author)

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.

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

Dinitrogen fixation measurements in some legume crops grown under irrigated condition without bacteria inoculation using 15N

International Nuclear Information System (INIS)

Kurdali, F.; Sharabi, N.D.

1991-01-01

N 2 -fixation in some legume crops: Faba bean Vicia faba, common bean pisum sativum, lentil lens esculenta, chick pea cicer artinum and vetch vicia arvillia grown under irrigated conditions without Rhizobium inoculation was estimated using 15 N-labelled fertilizer method. Barley was used as a reference crop. Significant differences occured in N 2 -fixation capacity among legume crops at flowering and podding stages. The highest percentage of Nitrogen fixed occured in faba bean (88% of total N), while lower values were observed in the other crops: Lentil 84%, vetch 68%, common pea 67% and chick pea 57%. Moreover, amounts of N 2 -fixed were 171, 138, 100, 90 and 13 Kg. N. ha -1 respectively for faba bean, lentil, vetch, common pea and chick pea. This clearly indicates the importance of biological dinitrogen fixation in local legume crops nodulated with indigenous Rhizobium strains regarding to N-soil enrichment. Further investigations must be focused on the selection of both plant species and Rhizobium strains in order to obtain a good symbiotic system. (author). 2 figs

Cell-specific CO2 fixation rates of two distinct groups of plastidic protists in the Atlantic Ocean remain unchanged after nutrient addition.

Science.gov (United States)

Grob, Carolina; Jardillier, Ludwig; Hartmann, Manuela; Ostrowski, Martin; Zubkov, Mikhail V; Scanlan, David J

2015-04-01

To assess the role of open-ocean ecosystems in global CO2 fixation, we investigated how picophytoplankton, which dominate primary production, responded to episodic increases in nutrient availability. Previous experiments have shown nitrogen alone, or in combination with phosphorus or iron, to be the proximate limiting nutrient(s) for total phytoplankton grown over several days. Much less is known about how nutrient upshift affects picophytoplankton CO2 fixation over the duration of the light period. To address this issue, we performed a series of small volume (8-60 ml) - short term (10-11 h) nutrient addition experiments in different regions of the Atlantic Ocean using NH4 Cl, FeCl3 , K medium, dust and nutrient-rich water from 300 m depth. We found no significant nutrient stimulation of group-specific CO2 fixation rates of two taxonomically and size-distinct groups of plastidic protists. The above was true regardless of the region sampled or nutrient added, suggesting that this is a generic phenomenon. Our findings show that at least in the short term (i.e. daylight period), nutrient availability does not limit CO2 fixation by the smallest plastidic protists, while their taxonomic composition does not determine their response to nutrient addition. © 2014 Society for Applied Microbiology and John Wiley & Sons Ltd.

Short-range spatial variability of soil δ15N natural abundance – effects on symbiotic N2-fixation estimates in pea

DEFF Research Database (Denmark)

Holdensen, Lars; Hauggaard-Nielsen, Henrik; Jensen, Erik Steen

2007-01-01

abundance in spring barley and N2-fixing pea was measured within the 0.15-4 m scale at flowering and at maturity. The short-range spatial variability of soil δ15N natural abundance and symbiotic nitrogen fixation were high at both growth stages. Along a 4-m row, the δ15N natural abundance in barley......-abundance are that estimates of symbiotic N2-fixation can be obtained from the natural abundance method if at least half a square meter of crop and reference plants is sampled for the isotopic analysis. In fields with small amounts of representative reference crops (weeds) it might be necessary to sow in reference crop...

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)

Trochanteric Fixation With a Third-Generation Cable-Plate System: An Independent Experience.

Science.gov (United States)

Stewart, Andrew D; Abdelbary, Hesham; Beaulé, Paul E

2017-09-01

Greater trochanteric fracture/nonunion can be a devastating complication with significant functional impact after total hip arthroplasty, and their fixation remains a challenge because of the significant forces being transmitted as well as the poor bone quality often associated with these fractures. The objective of this study is to investigate the rates of reoperation and trochanteric nonunion using a third-generation cable-plate system at one center. Thirty-five patients, mean age 72.9 years (range 46-98 years) with 24 women and 11 men, underwent fixation of their fractured greater trochanter using a third-generation cable-plate system. The indications were: periprosthetic fracture (n = 17), complex primary arthroplasty (n = 5), and complex revision arthroplasty (n = 13). Primary outcomes included rates of reoperation and radiographic union. At a mean follow-up of 2.5 years, trochanteric union rate was 62.9% with nonunion rate of 31.4%, and fibrous union in 5.7%. In regard to quality of initial apposition, only 40% achieved a perfect bone on bone reduction. Ten patients (28.6%) had evidence of wire breakage. Five patients (14.3%) required reoperation and removal of the internal fixation because of lateral hip pain. Fixation of the trochanteric fractures remains a challenge with a relatively high reoperation rate. Poor bone quality and capacity to maintain a stable reduction continue to make this complication after total hip arthroplasty a difficult problem to solve. Copyright © 2017. Published by Elsevier Inc.

Measurement of N{sub 2} fixation in Sesbania aculeata pers. and Sorghum bicolor L. grown in intercropping system, under saline conditions, using {sup 15}N isotopic dilution technique

Energy Technology Data Exchange (ETDEWEB)

Kurdali, F; Khalifa, K; Janat, M [Atomic Energy Commission, Damascus (Syrian Arab Republic). Dept. of Agriculture

2001-09-01

A field experiment was conducted under saline conditions (soil EC{sub e} 15, water EC{sub w} 8 dS/m/m) to evaluate the performance of sole crops and inter crops of Sesbania aculeata and Sorghum bicolor (1:1 row ratio) in terms of dry matter production, total N yield, soil N uptake and N{sub 2}-fixation using {sup 15}N isotope dilution method. Dry matter yield in sole crop of sesbania was significantly higher that that of sole sorghum; whereas, that of the inter cropping was significantly lower than sole sesbania, but was similar to that produced by sole sorghum. Total nitrogen yield in sole sesbania was four-fold than that accumulated in sole sorghum, whereas, that of mixed cropping was 2.6 fold compared to that of sole sorghum. The LER of total N yield was higher than 1 reflecting a greater advantage of inter cropping system in terms of land use efficiency. The proportion of N derived from N{sub 2} fixation (%Ndfa) in the sesbania was increased from 63 to 79%, for sole and inter cropping system, respectively. There was no evidence of a significant transfer of N from the sesbania to the sorghum. Results on the relative growth of plants on saline soil compared with non-saline soil clearly demonstrated that sesbania was more salt tolerant than the sorghum. soil nitrogen uptake by plants, particularly in sorghum, was adversely affected by salinity. However, amounts of N{sub 2} fixed by sole sesbania grown is saline soil was close or even higher than on non-saline soil. The use of inter cropping systems of legumes and non-legumes could be a promising agricultural approach to reutilize wasted lands, after a careful selection of appropriate tolerant genotypes to prevailing saline conditions. (author)

Impact of rhizobial inoculation and reduced N supply on biomass production and biological N2 fixation in common bean grown hydroponically.

Science.gov (United States)

Kontopoulou, Charis-Konstantina; Liasis, Epifanios; Iannetta, Pietro Pm; Tampakaki, Anastasia; Savvas, Dimitrios

2017-10-01

Testing rhizobial inoculation of common bean (Phaseolus vulgaris L.) in hydroponics enables accurate quantification of biological N 2 fixation (BNF) and provides information about the potential of reducing inorganic N fertilizer use. In view of this background, common bean grown on pumice was inoculated with Rhizobium tropici CIAT899 (Rt) and supplied with either full-N (total nitrogen 11.2 mmol L -1 ), 1/3 of full-N or N-free nutrient solution (NS). BNF was quantified at the early pod-filling stage using the 15 N natural abundance method. Full-N supply to Rt-inoculated plants resulted in markedly smaller nodules than less- or zero-N supply, and no BNF. Rt inoculation of full-N-treated plants did not increase biomass and pod yield compared with non-inoculation. Restriction (1/3 of full-N) or omission of inorganic N resulted in successful nodulation and BNF (54.3 and 49.2 kg N ha -1 , corresponding to 58 and 100% of total plant N content respectively) but suppressed dry shoot biomass from 191.7 (full-N, +Rt) to 107.4 and 43.2 g per plant respectively. Nutrient cation uptake was reduced when inorganic N supply was less or omitted. Rt inoculation of hydroponic bean provides no advantage when full-N NS is supplied, while 1/3 of full-N or N-free NS suppresses plant biomass and yield, partly because the restricted NO 3 - supply impairs cation uptake. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Evaluation of chickpea and groundnut for N2 fixation and yield in Bangladesh

International Nuclear Information System (INIS)

Sattar, M.A.; Podder, A.K.; Das, M.L.; Shaikh, M.A.Q.; Danso, S.K.A.

1998-01-01

Field experiments on chickpea and groundnut were variously carried out at four locations in Bangladesh. Generally consistent trends were obtained in terms of positive effects of inoculation with rhizobia, and genotypic diversity for components of N 2 fixation and yield. Inoculation of groundnut increased average nodule number by 77% at Rajshahi, 99% at Mymensingh and 148% at Jamalput. The increases in nodule dry weight, plant dry weight, pod and stover yields due to inoculation ranged from 93 to 146%, 55 to 77%, 43 to 50% and 29 to 80%, respectively. At all three locations, significant differences were found amongst the genotypes for nodulation, dry matter production and yield. Mutant genotype 62-30 was superior for most components, and statistically better than the present variety Dacca-1 for all characteristics investigated. Inoculant application to chickpea resulted in at least a doubling of nodule number at Ishurdi and Mymensingh; on average, there was a three-fold increase in nodule mass as a result of inoculation. Seed-yield increases due to inoculation ranged from 24 to 50%. Inoculated cv. G-97 recorded a seed yield of about 1.5 t/ha at Ishurdi, 47% higher than that produced by Nabin, a variety widely cultivated in Bangladesh. Total-N yield and the amount of N fixed by G-97 with inoculant were also higher than for Hyprosola, which is known for high yield and protein content. In a screening trial at Mymensingh the commercial chickpea Nabin and Hyprosola were consistently inferior to advanced lines produced by mutation breeding. Of 12 mutant groundnut genotypes tested, D1-15KR/62-30 maintained superiority for almost all components. Most of the mutants performed better than the commercial variety Dacca-1. The data show the potential for increasing chickpea and groundnut yields in Bangladesh by improving N 2 fixation via selection of superior genotype in conjunction with compatible rhizobia

Growth and N2-fixation of dhaincha (Sesbania aculata) and sunflower (Helianthus annuus) in an inter cropping system using natural abundances of 15N and 13C

International Nuclear Information System (INIS)

Kurdali, F.

2010-06-01

A field experiment on dhaincha (Sesbania aculata) and sunflower (Helianthus annuus) plants grown in mono cropping and inter cropping systems was conducted to evaluate seed yield , oil content, dry matter production (DM), land equivalent ratio (LER), N- yield, competition for soil N uptake and N 2 -fixation using 13 C and 15 N natural abundance techniques. Three different combinations of sesbania (ses) and sunflower (sun) were investigated in the inter cropping system (1ses:1sun; 1ses:2sun, and 2ses:1sun, row ratio). The results showed that: From productivity standpoint, the 1ses:1sun surpassed the other treatments in terms of N and DM yields and exhibited a similar distribution of total DM and N uptake in the sesbania and sunflower plant species. The 1ses:2sun was next in order in terms of DM and N uptake showing also a similar distribution of total N in both plant species. On the other hand, the 1ses:2sun gave the greatest seed and oil production and together with 1ses:1sun treatment were satisfactory in terms of LER for DM in both species having almost similar values. However, the former treatment was more appropriate than the latter because of its higher LER value for seed and oil yield of sunflower plants. Nevertheless, 2ses:1sun treatment seemed not to be an appropriate treatment due to the divergence of LER values in both species, where sunflower plants had a low value as compared to sesbania. From ecological standpoint, the best treatment was 1ses:2sun which showed the greatest N 2 -fixation. Sesbania plants fixed almost identical amounts of atmospheric N 2 in both the mono cropping and inter cropping systems although the density of these plants in the latter was only 1/3 that of the former system. Moreover, soil N-uptake in the 1ses:2sun was the lowest among other treatments. These results give an advantage to the 1ses:2sun treatment over other treatments in terms of soil N consumption and N 2 fixation to meet sesbania's N requirements. %Δ 13 C in the

Spatial variation of N-2-fixation in field pea (Pisum sativum L.) at the field scale determined by the N-15 natural abundance method

DEFF Research Database (Denmark)

Hauggaard-Nielsen, Henrik; Holdensen, Lars; Wulfsohn, D.

2010-01-01

variability could be explained by the variability in selected abiotic soil properties. All measured soil variables showed substantial variability across the field and the pea dry matter production ranged between 4.9 and 13.8 Mg ha−1 at maturity. The percent of total N derived from the atmosphere (%Ndfa...... dry matter production and N2-fixation. A number of other models were tested, but the best was only able to explain less than 40% of the variance in %Ndfa using seven soil properties. Together with the use of interpolated soil data, high spatial variation of soil 15N natural abundance, a mean increase...

Benthic dinitrogen fixation traversing the oxygen minimum zone off Mauritania (NW Africa)

DEFF Research Database (Denmark)

Gier, Jessica; Löscher, Carolin R.; Dale, Andrew W.

2017-01-01

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...

A single evolutionary innovation drives the deep evolution of symbiotic N2-fixation in angiosperms

Science.gov (United States)

Werner, Gijsbert D. A.; Cornwell, William K.; Sprent, Janet I.; Kattge, Jens; Kiers, E. Toby

2014-01-01

Symbiotic associations occur in every habitat on earth, but we know very little about their evolutionary histories. Current models of trait evolution cannot adequately reconstruct the deep history of symbiotic innovation, because they assume homogenous evolutionary processes across millions of years. Here we use a recently developed, heterogeneous and quantitative phylogenetic framework to study the origin of the symbiosis between angiosperms and nitrogen-fixing (N2) bacterial symbionts housed in nodules. We compile the largest database of global nodulating plant species and reconstruct the symbiosis’ evolution. We identify a single, cryptic evolutionary innovation driving symbiotic N2-fixation evolution, followed by multiple gains and losses of the symbiosis, and the subsequent emergence of ‘stable fixers’ (clades extremely unlikely to lose the symbiosis). Originating over 100 MYA, this innovation suggests deep homology in symbiotic N2-fixation. Identifying cryptic innovations on the tree of life is key to understanding the evolution of complex traits, including symbiotic partnerships. PMID:24912610

Carbon sequestration in soybean crop soils: the role of hydrogen-coupled CO2 fixation

Science.gov (United States)

Graham, A.; Layzell, D. B.; Scott, N. A.; Cen, Y.; Kyser, T. K.

2011-12-01

Conversion of native vegetation to agricultural land in order to support the world's growing population is a key factor contributing to global climate change. However, the extent to which agricultural activities contribute to greenhouse gas emissions compared to carbon storage is difficult to ascertain, especially for legume crops, such as soybeans. Soybean establishment often leads to an increase in N2O emissions because N-fixation leads to increased soil available N during decomposition of the low C:N legume biomass. However, soybean establishment may also reduce net greenhouse gas emissions by increasing soil fertility, plant growth, and soil carbon storage. The mechanism behind increased carbon storage, however, remains unclear. One explanation points to hydrogen coupled CO2 fixation; the process by which nitrogen fixation releases H2 into the soil system, thereby promoting chemoautotrophic carbon fixation by soil microbes. We used 13CO2 as a tracer to track the amount and fate of carbon fixed by hydrogen coupled CO2 fixation during one-year field and laboratory incubations. The objectives of the research are to 1) quantify rates of 13CO2 fixation in soil collected from a field used for long-term soybean production 2) examine the impact of H2 gas concentration on rates of 13CO2 fixation, and 3) measure changes in δ13C signature over time in 3 soil fractions: microbial biomass, light fraction, and acid stable fraction. If this newly-fixed carbon is incorporated into the acid-stable soil C fraction, it has a good chance of contributing to long-term soil C sequestration under soybean production. Soil was collected in the field both adjacent to root nodules (nodule soil) and >3cm away (root soil) and labelled with 13CO2 (1% v/v) in the presence and absence of H2 gas. After a two week labelling period, δ13C signatures already revealed differences in the four treatments of bulk soil: -17.1 for root, -17.6 for nodule, -14.2 for root + H2, and -6.1 for nodule + H2

Do you like what you see? The role of first fixation and total fixation duration in consumer choice

NARCIS (Netherlands)

Laan, van der L.N.; Hooge, I.T.C.; Ridder, de D.T.D.; Viergever, M.A.; Smeets, P.A.M.

2015-01-01

Although there has been recent growing interest in the associations between measures of visual attention and consumer choice, there is still uncertainty about the role of the first fixation in consumer choice and the factors that drive total fixation duration. The study aimed (1) to investigate the

Do you like what you see? : The role of first fixation and total fixation duration in consumer choice

NARCIS (Netherlands)

van der Laan, Laura N.; Hooge, Ignace T C; De Ridder, Denise T D; Viergever, Max A.; Smeets, Paul A M

2015-01-01

Although there has been recent growing interest in the associations between measures of visual attention and consumer choice, there is still uncertainty about the role of the first fixation in consumer choice and the factors that drive total fixation duration. The study aimed (1) to investigate the

The Effect of Land-use Change and Management on Free-living N2 fixation in the Brazilian Atlantic Forest

Science.gov (United States)

De Oliveira Bomfim, B.; Silva, L. C. R.; Horwath, W. R.; Hello, J.; Doane, T. A.

2016-12-01

Globally, primary tropical forests are increasingly disturbed by deforestation, urbanization, agriculture, and cattle ranching. It has been recognized that the resulting (secondary) forests now play a key role in global biogeochemical cycles; however, little is known about alterations in forest function caused by the combination of disturbance and land use change. Fire, deforestation, and forest-to-monocrop conversion are all likely to affect biotic N inputs, yet our understanding of how free-living N2 fixation influences ecosystem response after disturbance remains poorly understood. Our research is assessing the role of asymbiotic (free-living) biological nitrogen fixation (BNF), a microbially-mediated process responsible for providing N inputs across terrestrial ecosystems and modulating the effect of fire and land cover in secondary forest succession. Free-living BNF is being quantified through incubations using stable isotope (15N2 labeling experiment) in different substrates (soil and leaf litter) under contrasting land use and management in the Brazilian Atlantic Forest, the most deforested Biome in Brazil with only 7% of its original cover. Soil and litter samples were collected in primary forests, 12-year secondary forests, Eucalyptus spp. plantations and 10-year Brachiaria brizantha pastures. Preliminary results indicate that free-living BNF rates did not vary significantly between either secondary land use (0.02 to 0.46 µg N2 fixed gDW-1 h-1), but rates were significantly higher in the litter layer (0.32 to 3.8 µg N2 fixed gDW-1 h-1) than in the surface soil (0 - 10 cm and 10 - 30 cm). Free-living BNF in this stretch of the Brazilian Atlantic Forest seems not to be significantly affected by contrasting land use and management.

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.

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

Regulation of nif gene expression and the energetics of N2 fixation over the diel cycle in a hot spring microbial mat.

Science.gov (United States)

Steunou, Anne-Soisig; Jensen, Sheila I; Brecht, Eric; Becraft, Eric D; Bateson, Mary M; Kilian, Oliver; Bhaya, Devaki; Ward, David M; Peters, John W; Grossman, Arthur R; Kühl, Michael

2008-04-01

Nitrogen fixation, a prokaryotic, O2-inhibited process that reduces N2 gas to biomass, is of paramount importance in biogeochemical cycling of nitrogen. We analyzed the levels of nif transcripts of Synechococcus ecotypes, NifH subunit and nitrogenase activity over the diel cycle in the microbial mat of an alkaline hot spring in Yellowstone National Park. The results showed a rise in nif transcripts in the evening, with a subsequent decline over the course of the night. In contrast, immunological data demonstrated that the level of the NifH polypeptide remained stable during the night, and only declined when the mat became oxic in the morning. Nitrogenase activity was low throughout the night; however, it exhibited two peaks, a small one in the evening and a large one in the early morning, when light began to stimulate cyanobacterial photosynthetic activity, but O2 consumption by respiration still exceeded the rate of O2 evolution. Once the irradiance increased to the point at which the mat became oxic, the nitrogenase activity was strongly inhibited. Transcripts for proteins associated with energy-producing metabolisms in the cell also followed diel patterns, with fermentation-related transcripts accumulating at night, photosynthesis- and respiration-related transcripts accumulating during the day and late afternoon, respectively. These results are discussed with respect to the energetics and regulation of N2 fixation in hot spring mats and factors that can markedly influence the extent of N2 fixation over the diel cycle.

CO2 fixation in alfalfa and birdsfoot trefoil root nodules and partitioning of 14C to the plant

International Nuclear Information System (INIS)

Maxwell, C.A.; Vance, C.P.; Heichel, G.H.; Stade, S.

1984-01-01

The objectives of this study were to determine if nonphotosynthetic CO 2 fixation by root nodules contributes carbon for the assimilation of fixed N 2 in alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.) and if assimilation products are partitioned to different plant organs. Effective alfalfa nodules excised from or attached to roots had apparent 14 CO 2 fixation rates of 50 to 80 μg CO 2 kg -1 s -1 (dry weight) at 0.0012 to 0.0038 mole fraction CO 2 . Nodule CO 2 fixation rates increased six- to seven-fold as ambient CO 2 was raised from 0.0038 to 0.0663 mole fraction. Respiration rates of nodules (3 to 4 mg CO 2 kg -1 s -1 ) were 10 to 100-fold higher than 14 CO 2 fixation rates of nodules. Pulse chase experiments with 14 CO 2 combined with nodule and xylem sap analysis demonstrated the initial products of root and nodule CO 2 fixation were organic acids. However, the export of fixed 14 C from effective nodules was primarily in the form of amino acids. In contrast, nodule and/or root fixed 14 C in ineffectively nodulated alfalfa and denodulated effective alfalfa and birdsfoot trefoil was transported primarily as organic acids. Aspartate, asparagine, alanine, glutamate, and glutamine were the most heavily labeled compounds in the amino acid fraction of both effective alfalfa and birdsfoot trefoil nodules exposed to 14 CO 2 . By contrast, asparate, asparagine, and glutamine were the predominantly labeled amino acids in xylem sap collected from nodulated effective roots exposed to 14 CO 2 . The occurrence of nodule CO 2 fixation in alfalfa and birdsfoot trefoil and the export of fixed carbon as asparagine and aspartate to roots and shoots is consistent with a role for CO 2 fixation by nodules in providing carbon skeletons for assimilation and transport of symbiotically fixed N 2

How can increased use of biological N2 fixation in agriculture benefit the environment?

International Nuclear Information System (INIS)

Jensen, Erik Steen; Hauggaard-Nielsen, Henrik

2001-01-01

Asymbiotic, associative or symbiotic biological N 2 fixation (BNF), is a free and renewable resource, which should constitute an integral part of sustainable agro-ecosystems. Yet there has been a rapid increase in use of fertiliser N and a parallel decline in the cultivation of leguminous plants and BNF, especially in the developed world. Fertilisers have boosted crop yields, but intensive agricultural systems have increasingly negative effects on the atmospheric and aquatic environments. BNF, either alone or in combination with fertilisers and animal manures, may prove to be a better solution to supply nitrogen to the cropping systems of the future. This review focuses on the potential benefit of BNF on the environment especially on soil acidification, rhizosphere processes and plant CO 2 fixation. As fertiliser N has supplanted BNF in agriculture the re-substitution of BNF is considered. What is the consequence of fertiliser N production on energy use? The effect of fertiliser use on the release of the greenhouse gas CO 2 is estimated at approximately 1 % of the global anthropogenic emission of CO 2 . The role of BNF on nitrogen cycling, ammonia volatilisation, N 2 O emission and NO 3 leaching suggests that BNF is less likely than fertilisers to cause losses during pre-cropping and cropping. Sometimes however the post-harvest losses may be greater, due to the special qualities of legume residues. Nevertheless, legumes provide other 'ecological services' including improved soil structure, erosion protection and greater biological diversity. (author)

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

Mechanism of CO 2 Fixation by Ir I -X Bonds (X = OH, OR, N, C)

KAUST Repository

Vummaleti, Sai V. C.; Talarico, Giovanni; Nolan, Steven P.; Cavallo, Luigi; Poater, Albert

2015-01-01

Density functional theory calculations have been used to investigate the CO2 fixation mechanism proposed by Nolan et al. for the IrI complex [Ir(cod)(IiPr)(OH)] (1; cod = 1,5-cyclooctadiene; IiPr = 1,3-diisopropylimidazol-2-ylidene) and its derivatives. For 1, our results suggest that CO2 insertion is the rate-limiting step rather than the dimerization step. Additionally, in agreement with the experimental results, our results show that CO2 insertion into the Ir-OR1 (R1 = H, methyl, and phenyl) and Ir-N bonds is kinetically facile, and the calculated activation energies span a range of only 12.0-23.0 kcal/mol. Substantially higher values (35.0-50.0 kcal/mol) are reported for analogous Ir-C bonds. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanism of CO 2 Fixation by Ir I -X Bonds (X = OH, OR, N, C)

KAUST Repository

Vummaleti, Sai V. C.

2015-09-08

Density functional theory calculations have been used to investigate the CO2 fixation mechanism proposed by Nolan et al. for the IrI complex [Ir(cod)(IiPr)(OH)] (1; cod = 1,5-cyclooctadiene; IiPr = 1,3-diisopropylimidazol-2-ylidene) and its derivatives. For 1, our results suggest that CO2 insertion is the rate-limiting step rather than the dimerization step. Additionally, in agreement with the experimental results, our results show that CO2 insertion into the Ir-OR1 (R1 = H, methyl, and phenyl) and Ir-N bonds is kinetically facile, and the calculated activation energies span a range of only 12.0-23.0 kcal/mol. Substantially higher values (35.0-50.0 kcal/mol) are reported for analogous Ir-C bonds. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Biological N2 Fixation by Chickpea in inter cropping System on Sand Soil

International Nuclear Information System (INIS)

Ismail, M. M.; Moursy, A. A. A.; Kotb, E. A.; Farid, I. M.

2012-12-01

A field experiment was carried out at the plant Nutrition and Fertilization Unit, Soils and Water Research Department, Nuclear Research Center, Atomic Energy Authority, Inshas, Egypt on wheat and chickpea inter cropping. The benefits of N 2 fixation by legumes to cereals growing in inter crops or to grasses growing in mixed swards are high clear. in cases the benefit to the N status of cereals has bee seen when they are inter cropped with legumes , where benefit is found ,it is mainly due to sparing of soil N rather than direct transfer from the legume. inter cropped wheat has a high grains yield as compared to those recorded under sole crop. The application of inter cropping system induced an increase of wheat grain yield against the sole system. regardless the cultivation system, the over all means of fertilizer rates indicated (50% MF + 50% OM) treatment was superiority (100% OM) and (75% MF + 25% OM) or those recorded with either un fertilizer when wheat grain yield considered. Comparison heed between organic sources reflected the superiority of under sole cultivation, while chickpea straw was the best under inter cropping. Inter cropped has a high grain N uptake compared to soil system. While totally organic materials had accumulates more N in grain than those of underrated treated control. In the same time, the overall mean indicated the superiority of compost treatment combined with 50% mineral fertilizer under inter cropping system over those of either only organic materials treatment or those combined with 75% mineral fertilizer. Plants treated of chickpea straw and compost, achieved the best value of straw weight. Among the organic manure treatments, chickpea straw and compost seem to be the best ones. Nitrogen derived from air (% Ndfa) shoots and seeds of chickpea plant: In case of cow manure and maize stalk, the best value of nitrogen derived from air was detected followed by compost, while the lowest value was recorded with wheat straw. In general

Pea-barley intercropping for efficient symbiotic N-2-fixation, soil N acquisition and use of other nutrients in European organic cropping systems

DEFF Research Database (Denmark)

Hauggaard-Nielsen, Henrik; Gooding, M.; Ambus, Per

2009-01-01

Complementarity in acquisition of nitrogen (N) from soil and N-2-fixation within pea and barley intercrops was studied in organic field experiments across Western Europe (Denmark, United Kingdom, France, Germany and Italy). Spring pea and barley were sown either as sole crops, at the recommended...... recovery was greater in the pea-barley intercrops than in the sole Crops Suggesting a high degree of complementarity over a wide range of growing conditions. Complementarity was partly attributed to greater soil mineral N acquisition by barley, forcing pea to rely more on N-2-fixation. At all sites......) in Danish and German experiments was 20% higher in the intercrop (P50B50) than in the respective sole crops, possibly influencing general crop yields and thereby competitive ability for other resources. Comparing all sites and seasons, the benefits of organic pea-barley intercropping for N acquisition were...

Stimulation of biological N2-fixation to accelerate the microbial remediation of soil contaminated by petroleum hydrocarbons

International Nuclear Information System (INIS)

Tereshenko, N.N.; Lushnikov, S.V.

2005-01-01

All remediation projects are comprised at least in accelerating the processes of the self-cleaning and self-restoration of biocenose which is led to increasing the functional activity of hydrocarbon-oxidizing microflora (HOM). Some of experts are carefully relate to introducing the commercial cultures of active hydrocarbon-consuming microbes into soils. They are afraid of unpredictable behavior of the cultures in soils. That why the stimulation of metabolic activity of indigenous soil microflora seems to be most preferable. In fact, contamination of soil with low nitrogen capacity by oil spills leads to significant deficient of nitrogen for HOM. Nitrogen content limits the soil self-restoration. Inorganic nitrogen fertilizers are supplied to recover the balance. The study of the microbial destruction of petroleum-hydrocarbons in association with biochemical transformation of nitrogen was carried out in lab and field experiments during 2000-2004. Study showed the activity of HOM correlates with rate of microbial fixing atmospheric nitrogen. Activity of biological N 2 -fixation significantly depends on supplying fertilizers (dose, date and kind). General practice of remediation of hydrocarbon-contaminated soils applies high initial doses of nitrogen-fertilizers (0.5-1 t per ha). Such practice leads to inhibition of N 2 -fixation processes, decreasing rate of oil destruction and loosing nitrogen due to activation of microbial denitrification. In opposition to that, the fractioned and advanced supplying mineral nitrogen fertilizers with aluminosilicate is the cost-effective approach to remediation of hydrocarbon-contaminated soils. Field experiments showed that the approach allows to increase efficiency of treatment up to 70-75% and to decrease operational expenses 2-3 times at least. (authors)

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.

Dinitrogen Fixation Within and Adjacent to Oxygen Deficient Waters of the Eastern Tropical South Pacific Ocean

Science.gov (United States)

Widner, B.; Mulholland, M. R.; Bernhardt, P. W.; Chang, B. X.; Jayakumar, A.

2016-02-01

Recent work suggests that planktonic diazotrophs are geographically more widely distributed than previously thought including relatively warm (14-23oC) aphotic oxygenated pelagic waters and in aphotic waters within oxygen deficient zones. Because the volume of aphotic water in the ocean is large and may increase in the future, if dinitrogen (N2) fixation is widely occurring at sub-euphotic depths, this could result in a dramatic upward revision of global nitrogen (N) inputs via this process. N2 fixation rates were measured during a cruise in the Eastern Tropical South Pacific using stable isotope tracer techniques that account for slow gas dissolution. Results are compared with light, nutrient, and oxygen gradients (and necessarily temperature gradients). In addition, rates of N2 fixation made in vertical profiles within and above oxygen deficient waters are compared with those measured in vertical profiles adjacent to oxygen deficient waters. Results suggest that while rates of N2 fixation were measurable in deeper anoxic waters, volumetric N2 fixation rates were higher in surface waters.

Evaluation of hedgerow trees in alley cropping for phosphorus use efficiency and N{sub 2} fixation in low P soils in moist savanna in Nigeria

Energy Technology Data Exchange (ETDEWEB)

Sanginga, N [International Inst. of Tropical Agriculture, Ibadan (Nigeria); Danso, S K.A. [Joint FAO/IAEA Div. of Nuclear Techniques in Food and Agriculture, Vienna (Austria). Soil Fertility and Crop Production Section; Zapata, F [FAO/IAEA Agriculture and Biotechnology Lab., Seibersdorf (Austria). Soils Science Unit; Bowen, G D [Commonwealth Scientific and Industrial Research Organization, Glen Osmond (Australia). Div. of Soils

1996-07-01

Soils low in P and N are common in the moist savanna climatic zones and consequently growth of hedgerow trees in alley cropping systems might require addition of N and P fertilizers. This is difficult for small scale farmers who have limited access to fertilizers and therefore depend only on limited input cropping systems. Exploiting genetic differences in P use efficiency and using hedgerow trees selected for high N{sub 2} fixation ability can improve tree establishment and growth on N and P-poor soils, restore soil fertility and preserve soil from degradation. Field experiments carried out at Fashola (moist savanna) have shown that large differences in growth and P use efficiency occurred between N{sub 2} fixing trees such as Gliricidia sepium, and non N{sub 2}-fixing trees such as Senna siamea and Senna spectabilis. Provenances or isoline differences in P use efficiency also occurred within species and was also influenced by level of P and period of growth. Differences between species and provenances in P uptake and growth were largely related to differences in physiological P-use efficiency (PPUE), root length and VAM infection rate, especially at low P. In general, nodulation was improved by P application, but varied among provenances. Gliricidia Sepium fixed about 61% of its N from atmospheric N{sub 2} in the pot experiment and 40% in the field. The percentage of N fixed was not affected by rate of P application. Differences in P and N accumulation and use efficiency were also influenced by management practices such as pruning. The distribution of total P followed the same trend as that of dry matter yield, while no significant correlations were found between partitioning of dry matter and total N. Uncut and cut G. Sepium derived 35 and 54% respectively of their N from atmospheric N{sub 2}. About 54% of the fixed N{sub 2} was partitioned to shoots and roots and this was not proportional to the size of these organs relative the whole plant. 17refs,2figs,2tabs.

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.)

Initial organic products of fixation of [13N]dinitrogen by root nodules of soybean (Glycine max)

International Nuclear Information System (INIS)

Meeks, J.C.; Wolk, C.P.; Schilling, N.; Shaffer, P.W.; Avissar, Y.; Chien, W.S.

1978-01-01

When detached soybean Glycine max (L.) Merr. cv. Hark, nodules assimilate ( 13 N)N 2 , the initial organic product of fixation is glutamine; glutamate becomes more highly radioactive than glutamine within 1 minute; 13 N in alanine becomes detectable at 1 minute of fixation and increases rapidly between 1 and 2 minutes. After 15 minutes of fixation, the major 13 N-labeled organic products in both detached and attached nodules are glutamate and alanine, plus, in the case of attached nodules, an unidentified substance, whereas ( 13 N)glutamine comprises only a small fraction of organic 13 N, and very little 13 N is detected in asparagine. The fixation of ( 13 N)N 2 into organic products was inhibited more than 99 percent by C 2 H 2 (10 percent, v/v). The results support the idea that the glutamine synthetase-glutamate synthase pathway is the primary route for assimilation of fixed nitrogen in soybean nodules

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

Seasonal N changes in alnus orientalis and populus nigra and N2 fixation by exotic alder species in Syria

International Nuclear Information System (INIS)

Kurdali, F.

2002-01-01

Two experiments were conducted.The first was to study nodulation and N 2 fixation of several introduced alder species (Alnus glutinosa, A. incana, A. rubra and A. viridis) grown in soil from beneath Alnus orientalis. The second was to determine pattern of N changes in leaves and bark of Alnus orientalis and populus nigra natural stands during two successive years. Results showed that frankia in soil from underneath Alnus orientalis nodulated and fixed nitrogen on roots of local alder as well as on roots of introduced alder species from distant and ecologically diverse localities. However, differences were found among species in the number of nodules formed and amount of nitrogen fixed. Percentages of nitrogen derived from atmosphere (%Ndfa) ranged from 5% in A.viridis to 66% in A. orientalis. Microscopic study of Alnus orientalis nodules showed the presence of vesicles, and frankia belonging to Sp-type. Foliar N concentration was higher in alder than in poplar. Total N concentration in alder leaves remained relatively constant at about 3% during summer, whereas N concentration in poplar decreased sharply in leaves and increased in bark. No substantial increase in N concentration was found in alder bark, and the fallen leaves were rich in nitrogen. During autumn, leaf N concentration in poplar decreased by 43% and 51% for the first and the second year, respectively, whereas N concentrations in bark increased by 71% and 100%. Total N concentrations in alder leaves decreased only by 8-16% while, values in the adjacent bark remained stable. In contrast to poplar, it seems that Alnus orientalis does not exhibit net leaf retranslocation to bark tissues.(author)

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

Quantitative analysis of an engineered CO2-fixing Escherichia coli reveals great potential of heterotrophic CO2 fixation.

Science.gov (United States)

Gong, Fuyu; Liu, Guoxia; Zhai, Xiaoyun; Zhou, Jie; Cai, Zhen; Li, Yin

2015-01-01

Production of fuels from the abundant and wasteful CO2 is a promising approach to reduce carbon emission and consumption of fossil fuels. Autotrophic microbes naturally assimilate CO2 using energy from light, hydrogen, and/or sulfur. However, their slow growth rates call for investigation of the possibility of heterotrophic CO2 fixation. Although preliminary research has suggested that CO2 fixation in heterotrophic microbes is feasible after incorporation of a CO2-fixing bypass into the central carbon metabolic pathway, it remains unclear how much and how efficient that CO2 can be fixed by a heterotrophic microbe. A simple metabolic flux index was developed to indicate the relative strength of the CO2-fixation flux. When two sequential enzymes of the cyanobacterial Calvin cycle were incorporated into an E. coli strain, the flux of the CO2-fixing bypass pathway accounts for 13 % of that of the central carbon metabolic pathway. The value was increased to 17 % when the carbonic anhydrase involved in the cyanobacterial carbon concentrating mechanism was introduced, indicating that low intracellular CO2 concentration is one limiting factor for CO2 fixation in E. coli. The engineered CO2-fixing E. coli with carbonic anhydrase was able to fix CO2 at a rate of 19.6 mg CO2 L(-1) h(-1) or the specific rate of 22.5 mg CO2 g DCW(-1) h(-1). This CO2-fixation rate is comparable with the reported rates of 14 autotrophic cyanobacteria and algae (10.5-147.0 mg CO2 L(-1) h(-1) or the specific rates of 3.5-23.7 mg CO2 g DCW(-1) h(-1)). The ability of CO2 fixation was created and improved in E. coli by incorporating partial cyanobacterial Calvin cycle and carbon concentrating mechanism, respectively. Quantitative analysis revealed that the CO2-fixation rate of this strain is comparable with that of the autotrophic cyanobacteria and algae, demonstrating great potential of heterotrophic CO2 fixation.

The effect of double-row fixation on initial repair strength in rotator cuff repair: a biomechanical study.

Science.gov (United States)

Meier, Steven W; Meier, Jeffrey D

2006-11-01

The purpose of this study was to compare the initial mechanical strength of 3 rotator cuff repair techniques. A total of 30 fresh-frozen cadaveric shoulders were prepared, and full-thickness supraspinatus tears were created. Specimens were randomized and placed into 3 groups: (1) transosseous suture technique (group I: TOS, n = 10, 6F/4M), (2) single-row suture anchor fixation (group II: SRSA, n = 10, 6F/4M), and (3) double-row suture anchor fixation (group III: DRSA, n = 10, 6F/4M). Each specimen underwent cyclic load testing from 5 N to 180 N at a rate of 33 mm/sec. The test was stopped when complete failure (repair site gap of 10 mm) or a total of 5,000 cycles was attained. Group I (TOS) failed at an average of 75.3 +/- 22.49 cycles, and group II (SRSA) at an average of 798.3 +/- 73.28 cycles; group III (DRSA) had no failures because all samples were stopped when 5,000 cycles had been completed. Fixation strength of the DRSA technique proved to be significantly greater than that of SRSA (P row suture anchor fixation was significantly stronger than was single-row repair. Therefore, double-row fixation may be superior to other techniques in that it provides a substantially stronger repair that could lead to improved biologic healing. A high incidence of incomplete healing occurs in rotator cuff repair. Use of double-row fixation may help the clinician to address some deficiencies in current methods by increasing the strength of the repair, potentially leading to improved healing rates.

Relationship between C2H2 reduction, H2 evolution and 15N2 fixation in root nodules of pea (Pisum sativum)

DEFF Research Database (Denmark)

Skøt, Leif

1983-01-01

for N2 reduction, is often stated as the relative efficiency (1-H2/C2H2). This factor varied significantly (P 2 and N2, expressed as the H2/N2 ratio, was independent of plant age, however. This discrepancy and the observation......The quantitative relationship between C2H2 reduction, H2 evolution and 15N2 fixation was investigated in excised root nodules from pea plants (Pisum sativum L. cv. Bodil) grown under controlled conditions. The C2H2/N2 conversion factor varied from 3.31 to 5.12 between the 32nd and the 67th day...... after planting. After correction for H2 evolution in air, the factor (C2H2-H2)/N2 decreased to values near the theoretical value 3, or in one case to a value significantly (P 2 production but used...

Phosphorus requirement for symbiotic N2 fixation: a major challenge for sustainable agro-ecosystems

OpenAIRE

Drevon, Jean-Jacques; Abadie, Josiane; Amenc, Laurie; Bargaz, Adnane; Domergue, Odile; Lazali, Mohamed; Pernot, Catherine

2016-01-01

Low phophorus availability in about 40% of the world’s arable land limits crop yield, most particularly for leguminous crops when their growth depends upon symbiotic N2-fixation (SNF). Therefore, our work aims to increase the phosphorus use efficiency (PUE) for SNF, and its contribution to a more effective coupling between the P and N bio-geochemical cycles. Myo-inositol hexakisphosphate (phytate) constitutes the main source of organic P in soils, but is unavailable to plants. Phytases are th...

/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.

Delta.sup.15 ./sup.N as an indicator of N.sub.2./sub.-fixation by cyanobacterial mats in tropical marshes

Czech Academy of Sciences Publication Activity Database

Rejmánková, E.; Komárková, Jaroslava; Rejmánek, M.

2004-01-01

Roč. 67, č. 3 (2004), s. 353-368 ISSN 0168-2563 Grant - others:UC Davis Faculty(US) Research Grants Institutional research plan: CEZ:AV0Z6017912 Keywords : delta 15N * cyanobacteria * nitrogen fixation * wetlands Subject RIV: CE - Biochemistry Impact factor: 2.125, year: 2004

Evaluation of natural 15N abundance method in estimating symbiotic dinitrogen fixation by leguminous grasses

International Nuclear Information System (INIS)

Yao Yunyin; Cheng Ming; Ma Changlin; Wang Zhidong; Hou Jinqin; Zhang Lihong; Luo Yongyun

1991-01-01

Natural 15 N abundance method was used to estimate contribution of symbiotic dinitrogen fixation by leguminous grasses. With the method the expensive 15 N fertilizer did not need to be applied to the soil and the normal ecosystem was not disturbed. Collecting samples of shoots of leguminous grasses and measuring the content of 15 N in them wee all to do for estimating potential of symbiotically fixed N 2 . Isotopic fractionation associated with N 2 fixation by legumes was studied. Values for 7 cultivars of alfalfa were ranged between 1.0000 ∼ 1.0015 (δ 15 N values were -0.05 ∼ 1.47 per mille); and the values for white clover, mung bean and whitepopinac lead tree were 0.0079, 0.9983 and 1.0018 (δ 15 N values: 2.15, 1.74 and -1.81 per mille) respectively. According to the δ 15 N values of grasses tested, the potential of N 2 fixation for 6 cultivars of alfalfa was estimated. Glory and rambler had higher potential of N 2 fixation; Baoding, Aigonquin and Minto had lower potential, and Peru was the lowest.N 2 fixing activity of alfalfa varied with different periods. The peak was found between June and July. Effects of non-N 2 -fixing references and different methods on estimates of %Ndfa of leguminous grasses were also discussed

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.

Modification of bifunctional epoxy resin using CO2 fixation process and nanoclay

International Nuclear Information System (INIS)

Khoshkish, Morteza; Bouhendi, Hosein; Vafayan, Mehdi

2014-01-01

A bifunctional epoxy resin was modified by using a CO 2 fixation solution process in the presence of tetra n-butyl ammonium bromide (TBAB) as catalyst and the modified treated resin was treated by cloisite 30B as nano additive. The Unmodified epoxy resin (UME), CO 2 fixated modified epoxy resin (CFME), and CFME/clay nano composite (CFMEN), were cured by diethylenetriamine (DETA). A cycloaliphatic compound as a reactive diluent was used to control the viscosity of high viscose CFME. The exfoliation of organoclay in UME and CFME was investigated by X-ray diffraction and activation energy was computed using the advanced integral isoconversional method. The activation energy dependency demonstrated that the mechanism of UME curing did not change in the presence of nanoclay. In contrast, the CO 2 fixation results showed a significant change in the activation energy dependency. The Thermal stability parameters include the initial degradation temperature (IDT), the temperature at the maximum rate of weight loss (T max ), and the decomposition activation energy (E d ) were determined by thermal gravimetry analysis. Dynamic mechanical thermal analysis measurements showed that the presence of organoclay in CFME increases the T g of nano composite in contrast to UME. The fracture roughness of UME, CFME and CFNE were determined by scanning electron microscope. The exfoliated UME/1%clay nanocomposite was confirmed by TEM image. - Highlights: • A new epoxy resin was synthesized using CO 2 fixation reaction. • The synthesized epoxy resin was modified by an organo nano-clay. • CO 2 fixation noticeably changed the curing mechanism. • CO 2 fixation reaction consumes CO 2 which is a harmful greenhouse gas

Woody legume fallow productivity, biological N2-fixation and residual benefits to two successive maize crops in Zimbabwe

NARCIS (Netherlands)

Chikowo, R.; Mapfumo, P.; Nyamugafata, P.; Giller, K.E.

2004-01-01

Three woody legumes were planted as two-year 'improved fallows' to evaluate their residual nitrogen (N) effects on two subsequent maize crops under minimum and conventional tillage management. Maize monoculture and cowpea-maize-maize sequence treatments were included as controls. N-2-fixation was

Forage production and N2 fixation in mixed cropping of saltbush and shrubby medic grown on a salt affected soil

International Nuclear Information System (INIS)

Kurdali, F.

2008-11-01

Two experiments were conducted to evaluate dry matter, nitrogen yield, N 2 fixation (Ndfa) and soil N uptake in saltbush (Atriplex halimus) and shrubby medic (Medicago arborea) grown either solely or in mixture on a salt affected soil, using 15 N tracer techniques. In a pot experiment, the combined dry matter yield of both species was considerably higher than that of solely grown shrubs. The inclusion of saltbush in the mixed cropping system decreased soil N uptake by shrubby medic and enhanced %Ndfa without affecting amounts of N 2 fixed. Under field conditions, estimated values of %Ndfa via δ 15 N natural abundance were relatively similar to those of the pot experiment using 15 N enrichment method. It can be concluded that the use of mixed cropping system of shrubby medic and saltbush could be a promising bio-saline agricultural approach to utilize salt affected soils in terms of forage yield and N 2 -fixation. (Author)

Biological N2 fixation by chickpea in inter cropping system on sand soil

International Nuclear Information System (INIS)

Ismail, M. M.; Moursy, A. A. A.; Kotb, E. A.; Farid, I. M.

2012-12-01

A field experiment was carried out at the plant nutrition and fertilization unit, Soils and Water Research Department, Nuclear Research Center, Atomic Energy Authority, Inshas, Egypt on wheat and chickpea incorporating. The benefits of N 2 fixation by legumes to cereals growing in inter crops or to grasses growing in mixed swards are high clear. In cases the benefit to the N status of cereals has bee seen when they are inter cropped with legumes, where benefit is found, it is mainly due to sparing of soil N rather than direct transfer from the legume. Inter cropped wheat, has a high grains yield as compared to those recorded under sole crop. The application of inter cropping system an increase of wheat grain yield against the sole system, regardless the cultivation system, the over all means of fertilizer rates indicated (50% MF + 50% OM) treatment was superiority (100% OM) and (75% MF + 25% OM) or those recorded with either un fertilizer when wheat grain yield considered. Comparison heed between or gain sources reflected the superiority of compost under sole cultivation, while chickpea straw was the best under inter cropping. Inter cropped has a high grain N uptake compared to soil systems. While totally organic materials had accumulates more N in grains than those of untreated treated control. In the some time, the overall mean indicated the superiority of compost treatment combined with 50% mineral fertilizer under inter cropping system over those of either only organic materials treatment or those combined with 75% mineral fertilizer. Plants treated of chickpea straw and compost, achieved the best value of straw weight. A mong the organic manure treatments, chickpea straw and compost seem to be the best ones. Nitrogen derived from air (%Ndfa) shoots and seeds of chickpea plants: In case of cow manure and maize stalk, the best value of nitrogen derived from air was detected followed by compost, while the lowest value was recorded with wheat straw. In general

Improvement of Chickpea Growth and Biological N Fixation under Water Salinity Stress

International Nuclear Information System (INIS)

Gadalla, A. M.; Galal, Y. G. M.; Hamdy, A.

2004-01-01

This work had been carried out under greenhouse conditions of IAM-Bari, aimed at evaluating the effects of water and soil salinity on growth, yield and nitrogen fixation by chickpea plants inoculated with selected Rhizobium strains. Isotope dilution approach ( 15 N) was applied for quantification of biological N fixation and portions derived from fertilizer and soil (Ndff and Ndfs, respectively). Number of pods was decreased gradually with increasing water salinity levels. High levels of salinity negatively affected shoot, root dry matter, seed yield and N accumulated in shoots and roots. A slight difference in seed N was noticed between fresh water and 9 dS/m treatments. Nitrogen derived from fertilizer by shoots was slightly increased with 3, 6 and 9 dS/m treatments, while they were notably higher than the fresh water control. More than 80% and 70% of N accumulated in shoots and seeds, respectively were derived from fixation. Portions of N 2 -fixed in shoots was decreased with the level of 3 dS/m as compared to the fresh water, then tended to increase with both 6 and 9 dS/m treatments. Stability of %Ndfa with increasing salinity was noticed with seeds-N. Soil-N came next as a fraction of nitrogen demand, where it increased with increasing water salinity levels. Under adverse conditions of salinity, the plants offered some of their N requirements from the other two N sources. Application of the suitable Rhizobium bacteria strains could be profits for both of the plant growth and soil fertility via N 2 fixation. (Authors)

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

Directory of Open Access Journals (Sweden)

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

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.

Significance of Herbaspirillum seropedicae inoculation and/or straw amendment on growth and dinitrogen fixation of wheat using 15N-dilution method.

Science.gov (United States)

el-Komy, H M; Saad, O A; Hetta, A M

2003-01-01

The effect of Herbaspirillum seropedicae inoculation and/or maize straw (0, 5 and 10 Mg/hm2) amendment on the growth and N2 fixation of wheat was determined in pot experiments using 15N-dilution method. Inoculation resulted in accumulation of fixed nitrogen, and % N from atmosphere being 24.6 and 26.5% in wheat shoot and grain, respectively. Straw amendment reduced % Natm to 16.1 and 20.2% at high straw level (10 Mg/hm2). Rational nitrogen fertilization (180 kg N/hm2) completely inhibited N2 fixation by H. seropedicae inoculation. Bacterial inoculation increased dry shoot and grain yield up to 23 and 31%, respectively. The highest levels of shoot and grain dry mass (46.5 and 42.4%) were obtained by N-fertilization in both inoculated and uninoculated plants. Total shoot and grain N-yield increased irrespective of organic matter amendment by inoculation up to 9 and 25%, respectively. N-fertilized plants recorded a maximum increase in N-yield (57 and 51%). H. seropedicae was reisolated from inoculated wheat histosphere after harvesting (90 d from sowing). Neither organic matter nor mineral nitrogen applications had any marked effect on bacterial total counts colonizing wheat histosphere. Moreover, no symptoms of mottled stripe disease were observed on leaves and stems of inoculated plants.

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

Assessment of N2 fixing efficiency of Beijerinckia indica and Azospirillum brasilense in Sorghum (Sorghum bicolor (L.) moench) using 15N tracer

International Nuclear Information System (INIS)

Kanimoli, S.; Marimuthu, P.; Arulmozhiselvan, K.

2010-01-01

For studying the benefits of inoculation of N 2 fixing diazotrophs in the root zone of sorghum crop, a pot culture was conducted on neutral red sandy loam soil with sorghum cv. CO26, using 15 N tracer. At the end of 45 days duration after sowing, Beijerinckia indica inoculation contributed 56.9 per cent N derived from N 2 fixation, out of total N concentration in whole drymatter of sorghum plant. It proved to be the efficient N 2 fixer by contributing N from N 2 fixation to the tune of 17.6 Kg -1 . Accumulation of N derived from N 2 fixation from B. indica was primarily in leaf blade (50.0%) followed by stem (31.8%), leaf sheath (14.0%) and root (4.2%). Inoculation of Azospirillum brasllense accelerated uptake of N from soil and fertilizer N sources compared to B. indica and hence registered low N fixation. (author)

N2-fixation in fababean (vicia faba l.) grown in saline and non saline conditions using 15N tracer technique

International Nuclear Information System (INIS)

Khalifa, Kh.; Kurdali, F.

2002-09-01

A pot experiment was conducted to study the performance of growing fababean and barley under saline conditions, in terms of, dry matter yield, total nitrogen and, percentages and amount of N derived from soil, fertilizer and atmosphere using 15 N isotope dilution method. Three saline treatments were performed: First, plants were grown in saline soil and irrigated with saline water (Ws Ss), Second, Plants were grown in saline soil and irrigated with saline water (Ws Ss); and Third, Plants grown in non saline soil and irrigated with saline water (Ws Sn). Furthermore, a control treatment was performed by using non-saline soil and non-saline water (Wn Sn). The different salinity treatments reduced plant growth and the reduction was more pronounced in fababean than in barley. However, under conditions of either saline soil-soft irrigation water or non saline soil-salty irrigation water, the relative growth reduction did not exceed 50% of the control; whereas, a significant negative effect was obtained when plants were grown under completely saline conditions of both soil and irrigation water. Percentage of N 2 -fixed (% Ndfa) was not negatively affected by saline conditions. However, our results clearly demonstrated that the effect of salinity in fababean was more evident on plant growth than on N 2 -fixing activity. Further studies are needed to obtain more salt tolerant faba bean genotypes in terms of growth and yield. This could be simultaneously improve yield and N 2 -fixation under sever saline conditions. (author)

Dinitrogen fixation by legume shade trees and direct transfer of fixed N to associated cacao in a tropical agroforestry system.

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Nygren, Pekka; Leblanc, Humberto A

2015-02-01

Natural abundance of (15)N (δ (15)N) was determined in bulk soil, rhizospheric soil and vegetation in an organically managed cacao (Theobroma cacao L.) plantation with Inga edulis Mart. legume trees (inga) as the principal shade for studying the nitrogen (N) cycle in the system. Cacao without contact with legumes in an adjacent plantation was used as the reference for N2 fixation and direct N transfer calculations. Bulk and rhizospheric soils contained 72 and 20%, respectively, of whole- system N. No vegetation effect on δ (15)N in rhizospheric soil was detected, probably due to the high native soil N pool. Fine roots of the cacaos associated with inga contained ∼35% of N fixed from the atmosphere (Nf) out of the total N. Leaves of all species had significantly higher δ (15)N than fine roots. Twenty percent of system Nf was found in cacao suggesting direct N transfer from inga via a common mycelial network of mycorrhizal fungi or recycling of N-rich root exudates of inga. Inga had accumulated 98 kg [Nf] ha(-1) during the 14-year history of the plantation. The conservative estimate of current N2 fixation rate was 41 kg [Nf] ha(-1) year(-1) based on inga biomass only and 50 kg [Nf] ha(-1) year(-1) based on inga and associated trees. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Atmospheric dinitrogen fixation in the flooded rhizosphere as determined by the N-15 isotope technique

International Nuclear Information System (INIS)

Yoshida, Tomio; Yoneyama, Tadakatsu.

1980-01-01

Atmospheric nitrogen fixation in the rice rhizosphere was determined under in situ conditions of growing flooded rice using the N-15 isotope method. The whole plant growing in a pot at a reproductive stage was placed in a specially designed glass container and exposed to a 15 N 2 atmosphere. The amounts of total nitrogen fixed in the rice rhizosphere under the experimental conditions were 1366, 592, 878, and 698 μg per pot containing 0.4 kg of soil during 15 N 2 exposure for 7 to 13 days in the four experiments conducted in this study. It was also found that the nitrogen fixed in the rice rhizosphere was translocated into other plant parts. Nineteen to 25% of the total atmospheric nitrogen fixed in the rice rhizosphere was found in the roots, leaves and stems, and ears of the rice plants during the 15 N 2 exposure period. (author)

Discussion on the planting patterns of alfalfa and meadow fescue in mixed culture and evaluation for their contribution from N2 fixation

International Nuclear Information System (INIS)

Yao Yunyin; Zhang Xizhong; Chen Ming

1996-01-01

Effects of planting patterns on dry weight, N yield and dinitrogen fixation in alfalfa-meadow fescue pasture are studied by using split plot design in the field for two successive years. The results show that the pattern of row seeding in mixture (RM) is superior to the pattern of broadcasting in mixture (BM) and intercropping (TC), and advantageous to develop the superiority of legume-grass mixed pasture. The annual average of dry weight for RM, BM and TC is 1535.9 g/m 2 , 1208.8 g/m 2 and 1249.3 g/m 2 respectively. The annual average of N yield of them is 50.83 g(N)/m 2 , 36.65 g(N)/m 2 and 36.86 g(N)/m 2 . The annual average Ndfa is 42.37 g(N)/m 2 , 28.21 g(N)/m 2 and 28.42 g(N)/m 2 , and %Ndfa is 83.4%, 77.0% and 77.1% for RM, BM and TC respectively. The comparison of 15 N isotope dilution method, natural 15 N abundance method and total N difference method to measure %Ndfa of herbage for all the treatments are made

Total fixation of cricoarytenoid joint of a patient with rheumatoid arthritis and Hashimoto thyroiditis.

Science.gov (United States)

Stojanović, Stevan P; Zivić, Ljubica; Stojanović, Jasmina; Belić, Branislav

2010-01-01

The incidence of cricoarytenoid joint fixation in case of rheumatoid arthritis is 17 to 33%. In later stages of rheumatoid arthritis, a gradual fixation of cricoarytenoid joint develops and both halves of the larynx become less movable which calls for endotracheal intubation; while total fixation of this joint demands surgical tracheotomy. Hashimoto thyroiditis can display symptoms which are difficult to distinguish from the ones present in total fixation of cricoarytenoid joint caused by rheumatoid arthritis. A 60-year-old woman in terminal stage of rheumatoid arthritis and Hashimoto thyroiditis, diagnosed after clinical and other examinations. She was treated for strident breathing with surgical tracheotomy. The microscopic examination of the larynx with the use of laryngoscopic pincers suggested the immovability of the right and very limited movability of the left arytenoid cartilage. A computerized endovideostroboscopy showed only passive vertical vibrating movements of the right vocal cord and irregular vibrations of the left vocal cord. Total fixation of the cricoarytenoid joint can be caused by many pathological processes, but so far references have shown no case of rheumatoid arthritis and Hashimoto thyroiditis. In differential diagnostics, one of many examinations is the microscopic examination of the larynx, but it is very important to determine the movability of the arytenoid cartilage with the use of appropriate instruments in total endotracheal anaesthesia while the patient is fully relaxed. Movements in cricoarytenoid joints in patients with Hashimoto thyroiditis and the same conditions are preserved.

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

Internal Versus External Fixation of Charcot Midfoot Deformity Realignment.

Science.gov (United States)

Lee, Daniel J; Schaffer, Joseph; Chen, Tien; Oh, Irvin

2016-07-01

Internal and external fixation techniques have been described for realignment and arthrodesis of Charcot midfoot deformity. There currently is no consensus on the optimal method of surgical reconstruction. This systematic review compared the clinical results of surgical realignment with internal and external fixation, specifically in regard to return to functional ambulation, ulcer occurrence, nonunion, extremity amputation, unplanned further surgery, deep infection, wound healing problems, peri- or intraoperative fractures, and total cases with any complication. A search of multiple databases for all relevant articles published from January 1, 1990, to March 22, 2014, was performed. A logistic regression model evaluated each of the outcomes and its association with the type of fixation method. The odds of returning to functional ambulation were 25% higher for internal fixation (odds ratio [OR], 1.259). Internal fixation had a 42% reduced rate of ulcer occurrence (OR, 0.578). External fixation was 8 times more likely to develop radiographic nonunion than internal fixation (OR, 8.2). Internal fixation resulted in a 1.5-fold increase in extremity amputation (OR, 1.488), a 2-fold increase in deep infection (OR, 2.068), a 3.4-fold increase in wound healing complications (OR, 3.405), and a 1.5-fold increase in the total number of cases experiencing any complication (OR, 1.525). This was associated with a 20% increase in the need for unplanned further surgery with internal fixation (OR, 1.221). Although internal fixation may decrease the risk of nonunion and increase return to functional ambulation, it had a higher rate of overall complications than external fixation for realignment and arthrodesis of Charcot midfoot deformity. [Orthopedics. 2016; 39(4):e595-e601.]. Copyright 2016, SLACK Incorporated.

Free atmospheric CO2 enrichment increased above ground biomass but did not affect symbiotic N2-fixation and soil carbon dynamics in a mixed deciduous stand in Wales

Directory of Open Access Journals (Sweden)

A. R. Smith

2011-02-01

Full Text Available Through increases in net primary production (NPP, elevated CO2 is hypothesized to increase the amount of plant litter entering the soil. The fate of this extra carbon on the forest floor or in mineral soil is currently not clear. Moreover, increased rates of NPP can be maintained only if forests can escape nitrogen limitation. In a Free atmospheric CO2 Enrichment (FACE experiment near Bangor, Wales, 4 ambient and 4 elevated [CO2] plots were planted with patches of Betula pendula, Alnus glutinosa and Fagus sylvatica on a former arable field. After 4 years, biomass averaged for the 3 species was 5497 (se 270 g m−2 in ambient and 6450 (se 130 g m−2 in elevated [CO2] plots, a significant increase of 17% (P = 0.018. During that time, only a shallow L forest floor litter layer had formed due to intensive bioturbation. Total soil C and N contents increased irrespective of treatment and species as a result of afforestation. We could not detect an additional C sink in the soil, nor were soil C stabilization processes affected by elevated [CO2]. We observed a decrease of leaf N content in Betula and Alnus under elevated [CO2], while the soil C/N ratio decreased regardless of CO2 treatment. The ratio of N taken up from the soil and by N2-fixation in Alnus was not affected by elevated [CO2]. We infer that increased nitrogen use efficiency is the mechanism by which increased NPP is sustained under elevated [CO2] at this site.

Effect of N-rate and P sources on BNF in soybean as affected by rhizobium and VAM fungi lnoculants

Energy Technology Data Exchange (ETDEWEB)

Soliman, S; Elghandour, I A [Soil and Water Dept., Atomic Energy Authority, Cairo, (Egypt); Abbady, A K [Soil and Water Inst., Agric. Res. Center, Giza (Egypt)

1995-10-01

Greenhouse experiment was made to investigate the influence of phosphate fertilizers on nitrogen fixation in soybean. The N-15 isotope dilution method was used to quantify N 2-fixed. In this concern, seed of nodulated and on-nodulated soybean plant bacterized with Bradyrhizobium japonicum and noculated without or with mycorrhizas in the presence of super or rock phosphate. Ammonium sulphate labelled fertilizer (5% N-15 a.e) was applied o 15 kg sandy soil of egypt at the rate of 20 and 100 kg N/acre. At re-flowering stage, the highest amount of N derived from air (Ndfa) was 66.3 and 470.2 (mg/pot) equivalent 47.6 and 47.1 of total N assimilated for noculated soybean with Rhizobium and fertilized with super or rock phosphate, respectively. While the contributions from 15 N labelled fertilizer (Ndff) accounted for 11 and 10.8, respectively. Use of mycorrhizas could increase the amount of N 2-fixed in the presence of rhizobia. There appears to be a strong case for improving N 2-fixation in the presence of mycorrhizas especially in sandy soil. 4 tabs.

Effect of N-rate and P sources on BNF in soybean as affected by rhizobium and VAM fungi lnoculants

International Nuclear Information System (INIS)

Soliman, S.; Elghandour, I.A.; Abbady, A.K.

1995-01-01

Greenhouse experiment was made to investigate the influence of phosphate fertilizers on nitrogen fixation in soybean. The N-15 isotope dilution method was used to quantify N 2-fixed. In this concern, seed of nodulated and on-nodulated soybean plant bacterized with Bradyrhizobium japonicum and noculated without or with mycorrhizas in the presence of super or rock phosphate. Ammonium sulphate labelled fertilizer (5% N-15 a.e) was applied o 15 kg sandy soil of egypt at the rate of 20 and 100 kg N/acre. At re-flowering stage, the highest amount of N derived from air (Ndfa) was 66.3 and 470.2 (mg/pot) equivalent 47.6 and 47.1 of total N assimilated for noculated soybean with Rhizobium and fertilized with super or rock phosphate, respectively. While the contributions from 15 N labelled fertilizer (Ndff) accounted for 11 and 10.8, respectively. Use of mycorrhizas could increase the amount of N 2-fixed in the presence of rhizobia. There appears to be a strong case for improving N 2-fixation in the presence of mycorrhizas especially in sandy soil. 4 tabs

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.

Impact of increased ultraviolet-B radiation stress due to stratospheric ozone depletion on N2 fixation in traditional African commercial legumes

International Nuclear Information System (INIS)

Chimphango, S.B.M.; Musil, C.F.; Dakora, F.D.

2004-01-01

Reports of diminished nodule formation and nitroge-nase activity in some Asian tropical legumes exposed to above-ambient levels of ultraviolet-B (UV-B: 280-315nm) radiation have raised concerns as to the impact of stratospheric ozone depletion on generally poorly developed traditional African farming systems confronted by the high cost and limited availability of chemical fertilisers. These rely on N 2 -fixing legumes as the cheapest source of N for maintaining soil fertility and sustainable yields in the intrinsically infertile and heterogeneous African soils. In view of this, we examined the effects of supplemental UV-B radiation approximating 15% and 25% depletions in the total ozone column on N 2 fixation in eight traditional African commercial legume species representing crop, forest, medicinal, ornamental and pasture categories. In all categories examined, except medicinal, supplemental UV-B had no effect on root non-structural carbohydrates, antho-cyanins and flavonoids, known to signal Rhizobiaceae micro-symbionts and promote nodule formation, or on nodule mass, activity and quantities of N fixed in different plant organs and whole plants. In contrast, in the medicinal category Cyclopia maculata (Honeybush) a slow growing commercially important herbal beverage with naturally high flavonoid concentrations, displayed decreased nodule activity and quantities of N fixed in different plant organs and whole plants with increased UV-B. This study's findings conclude negligible impacts of ozone depletion on nitrogen fixation and soil fertility in most traditional African farming systems, these limited to occasional inhibition of nodule induction in some crops. (author)

Effects of Bean-Maize Intercropping,Phosphorus and Manure Additions on N2 fixation and Grain Yield of Phaseolus Vulgaris in the Central Kenya Highlands

International Nuclear Information System (INIS)

Kimani, S.K.; Mwangale, N.; Gathua, K.W.; Delve, R.; Cadisch, G.

1999-01-01

Sole bean and intercropped bean crops were studied for four seasons from 1996-1998. Addition of organic P at the recommended rate of 60 kg P 2 O 5 ha -1 increased bean standing biomass and grain yields during the first season. Cattle manure applied at the rate of 12 t ha -1 (25% moisture content), had a negative effect on bean yield during the first season, possibly due to short-term nutrient immobilisation induced by the high C:N ratio of manure. In subsequent seasons, manure additions resulted in higher grain yields compared to inorganic P. Intercropping bean with maize lowered grain yields by 10-100%. N 2 fixed on beans on average from 55 to 69%. Intercropping thus provides a strategy for a better N resource use where the maize competes efficiently for available soil mineral N and the legume replenishes part of the extracted N via atmospheric N 2 fixation. However, the amounts of N 2 fixed appear not to be enough to replenish whole systems N in grain crops and so additional N 2 are needed. Thus more attention needs to be given to manure management and its long-term impact on soil fertility

Cemented versus uncemented fixation in total hip replacement: a systematic review and meta-analysis of randomized controlled trials

Directory of Open Access Journals (Sweden)

Ali Abdulkarim

2013-03-01

Full Text Available The optimal method of fixation for primary total hip replacements (THR, particularly fixation with or without the use of cement is still controversial. In a systematic review and metaanalysis of all randomized controlled trials comparing cemented versus uncemented THRS available in the published literature, we found that there is no significant difference between cemented and uncemented THRs in terms of implant survival as measured by the revision rate. Better short-term clinical outcome, particularly an improved pain score can be obtained with cemented fixation. However, the results are unclear for the long-term clinical and functional outcome between the two groups. No difference was evident in the mortality and the post operative complication rate. On the other hand, the radiographic findings were variable and do not seem to correlate with clinical findings as differences in the surgical technique and prosthesis design might be associated with the incidence of osteolysis. We concluded in our review that cemented THR is similar if not superior to uncemented THR, and provides better short term clinical outcomes. Further research, improved methodology and longer follow up are necessary to better define specific subgroups of patients in whom the relative benefits of cemented and uncemented implant fixation can be clearly demonstrated.

Cemented versus uncemented fixation in total hip replacement: a systematic review and meta-analysis of randomized controlled trials.

LENUS (Irish Health Repository)

Abdulkarim, Ali

2013-02-22

The optimal method of fixation for primary total hip replacements (THR), particularly fixation with or without the use of cement is still controversial. In a systematic review and metaanalysis of all randomized controlled trials comparing cemented versus uncemented THRS available in the published literature, we found that there is no significant difference between cemented and uncemented THRs in terms of implant survival as measured by the revision rate. Better short-term clinical outcome, particularly an improved pain score can be obtained with cemented fixation. However, the results are unclear for the long-term clinical and functional outcome between the two groups. No difference was evident in the mortality and the post operative complication rate. On the other hand, the radiographic findings were variable and do not seem to correlate with clinical findings as differences in the surgical technique and prosthesis design might be associated with the incidence of osteolysis. We concluded in our review that cemented THR is similar if not superior to uncemented THR, and provides better short term clinical outcomes. Further research, improved methodology and longer follow up are necessary to better define specific subgroups of patients in whom the relative benefits of cemented and uncemented implant fixation can be clearly demonstrated.

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.

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.

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.

A study for the biological CO2 fixation and utilization system

International Nuclear Information System (INIS)

Otsuki, T.

2001-01-01

Increased CO 2 in the atmosphere is such a serious problem for mankind that many research and development approaches are implemented to reduce CO 2 emissions. One is a biological CO 2 fixation using the photosynthetic function of microalgae like Chlorella and Synechocystis sp. The target of the project is to achieve a CO 2 fixation rate of 50 g CO 2 /m 2 ·d, which is 10 times as large as that of the temperate forest. The purpose of this study is to clarify the possibilities of the biological CO 2 fixation system in view of the CO 2 balance, energy balance, and payback period. The amount of CO 2 fixation of the system should be larger than the emission of CO 2 by operating. Furthermore, the energy consumption of the system should also be less than the biochemical energy (enthalpy) of glucose, which is made by photosynthesis. After CO 2 fixation was completed by the microalgae, the biomass must be utilized practically for many markets and the initial investment in the system construction could be regained

Modification of bifunctional epoxy resin using CO{sub 2} fixation process and nanoclay

Energy Technology Data Exchange (ETDEWEB)

Khoshkish, Morteza; Bouhendi, Hosein, E-mail: H.boohendi@ippi.ac.ir; Vafayan, Mehdi

2014-10-15

A bifunctional epoxy resin was modified by using a CO{sub 2} fixation solution process in the presence of tetra n-butyl ammonium bromide (TBAB) as catalyst and the modified treated resin was treated by cloisite 30B as nano additive. The Unmodified epoxy resin (UME), CO{sub 2} fixated modified epoxy resin (CFME), and CFME/clay nano composite (CFMEN), were cured by diethylenetriamine (DETA). A cycloaliphatic compound as a reactive diluent was used to control the viscosity of high viscose CFME. The exfoliation of organoclay in UME and CFME was investigated by X-ray diffraction and activation energy was computed using the advanced integral isoconversional method. The activation energy dependency demonstrated that the mechanism of UME curing did not change in the presence of nanoclay. In contrast, the CO{sub 2} fixation results showed a significant change in the activation energy dependency. The Thermal stability parameters include the initial degradation temperature (IDT), the temperature at the maximum rate of weight loss (T{sub max}), and the decomposition activation energy (E{sub d}) were determined by thermal gravimetry analysis. Dynamic mechanical thermal analysis measurements showed that the presence of organoclay in CFME increases the T{sub g} of nano composite in contrast to UME. The fracture roughness of UME, CFME and CFNE were determined by scanning electron microscope. The exfoliated UME/1%clay nanocomposite was confirmed by TEM image. - Highlights: • A new epoxy resin was synthesized using CO{sub 2} fixation reaction. • The synthesized epoxy resin was modified by an organo nano-clay. • CO{sub 2} fixation noticeably changed the curing mechanism. • CO{sub 2} fixation reaction consumes CO{sub 2} which is a harmful greenhouse gas.

Cortical bone trajectory screw fixation versus traditional pedicle screw fixation for 2-level posterior lumbar interbody fusion: comparison of surgical outcomes for 2-level degenerative lumbar spondylolisthesis.

Science.gov (United States)

Sakaura, Hironobu; Miwa, Toshitada; Yamashita, Tomoya; Kuroda, Yusuke; Ohwada, Tetsuo

2018-01-01

OBJECTIVE The cortical bone trajectory (CBT) screw technique is a new nontraditional pedicle screw (PS) insertion method. However, the biomechanical behavior of multilevel CBT screw/rod fixation remains unclear, and surgical outcomes in patients after 2-level posterior lumbar interbody fusion (PLIF) using CBT screw fixation have not been reported. Thus, the purposes of this study were to examine the clinical and radiological outcomes after 2-level PLIF using CBT screw fixation for 2-level degenerative lumbar spondylolisthesis (DS) and to compare these outcomes with those after 2-level PLIF using traditional PS fixation. METHODS The study included 22 consecutively treated patients who underwent 2-level PLIF with CBT screw fixation for 2-level DS (CBT group, mean follow-up 39 months) and a historical control group of 20 consecutively treated patients who underwent 2-level PLIF using traditional PS fixation for 2-level DS (PS group, mean follow-up 35 months). Clinical symptoms were evaluated using the Japanese Orthopaedic Association (JOA) scoring system. Bony union was assessed by dynamic plain radiographs and CT images. Surgery-related complications, including symptomatic adjacent-segment disease (ASD), were examined. RESULTS The mean operative duration and intraoperative blood loss were 192 minutes and 495 ml in the CBT group and 218 minutes and 612 ml in the PS group, respectively (p 0.05, respectively). The mean JOA score improved significantly from 12.3 points before surgery to 21.1 points (mean recovery rate 54.4%) at the latest follow-up in the CBT group and from 12.8 points before surgery to 20.4 points (mean recovery rate 51.8%) at the latest follow-up in the PS group (p > 0.05). Solid bony union was achieved at 90.9% of segments in the CBT group and 95.0% of segments in the PS group (p > 0.05). Symptomatic ASD developed in 2 patients in the CBT group (9.1%) and 4 patients in the PS group (20.0%, p > 0.05). CONCLUSIONS Two-level PLIF with CBT screw fixation

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

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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

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...

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...

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

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

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)

Variable Nitrogen Fixation in Wild Populus.

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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.

Effect of simulated tillage on microbial autotrophic CO2 fixation in paddy and upland soils

Science.gov (United States)

Ge, Tida; Wu, Xiaohong; Liu, Qiong; Zhu, Zhenke; Yuan, Hongzhao; Wang, Wei; Whiteley, A. S.; Wu, Jinshui

2016-01-01

Tillage is a common agricultural practice affecting soil structure and biogeochemistry. To evaluate how tillage affects soil microbial CO2 fixation, we incubated and continuously labelled samples from two paddy soils and two upland soils subjected to simulated conventional tillage (CT) and no-tillage (NT) treatments. Results showed that CO2 fixation (14C-SOC) in CT soils was significantly higher than in NT soils. We also observed a significant, soil type- and depth-dependent effect of tillage on the incorporation rates of labelled C to the labile carbon pool. Concentrations of labelled C in the carbon pool significantly decreased with soil depth, irrespective of tillage. Additionally, quantitative PCR assays revealed that for most soils, total bacteria and cbbL-carrying bacteria were less abundant in CT versus NT treatments, and tended to decrease in abundance with increasing depth. However, specific CO2 fixation activity was significantly higher in CT than in NT soils, suggesting that the abundance of cbbL-containing bacteria may not always reflect their functional activity. This study highlights the positive effect of tillage on soil microbial CO2 fixation, and the results can be readily applied to the development of sustainable agricultural management. PMID:26795428

Salvage of infected total knee arthroplasty with Ilizarov external fixator

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Venkata Gurava Reddy

2011-01-01

Full Text Available Background: Knee arthrodesis may be the only option of treatment in cases of chronic infected total knee arthroplasty (TKA with concomitant irreparable extensor mechanism disruption, extensive bone loss or severe systemic morbidities. Circular external fixation offers possible progressive adjustment to stimulate the bony fusion and to make corrections in alignment. We evaluated the results of knee arthrodesis with one or two stage circular external fixator for infected TKA. Materials and Methods: 16 cases of femoro-tibial fusion were retrospectively evaluated. Male-to-female ratio was 10:6. Mean age of the patients was 62.2 years. Cierney-Mader classification was used for anatomical and physiological evaluation while the bone stock deficiency was classified into mild, moderate and severe. Surgical technique involved either single or two stage arthrodesis using circular external fixator. Results: Union was achieved in 15 patients (93.75%. The mean duration for union (frame application time in these patients was 28.33 weeks (range 22 to 36 weeks. Analysis showed that in the group with frame application time of less than 28 weeks, the incidence of mild to moderate bone deficiency was 83.33%, while in the frame application time more than 28 weeks group the incidence was 20% (P-value 0.034. Similarly the incidence of Cierney-Mader 4B (Bl, Bs, Bls was found to be 33.33% in the group of frame application time of less than 28 weeks, while it was 90% in the group with frame application time more than 28 weeks (P-value 0.035. Conclusion: Circular external fixator is a safe and reliable method to achieve knee arthrodesis in cases of deep infection following TKA. Severe bone stock deficiency and Cierney- Mader type B host are likely risk factors for prolonged frame application time. We recommend a two-stage procedure especially when there is compromised host or severe bone loss.

Growth and N2-fixation of Dhaincha C-3/Sorghum C-4 and Dhaincha C-3/Sunflower C-3 intercropping systems using the 15N and 13C natural abundance method technique

International Nuclear Information System (INIS)

Kurdali, F.

2007-06-01

A field experiment on dhaincha C 3 (Sesbania aculeata Pers), sunflower C 3 (Helianthus annuus L.) and sorghum C 4 (Sorghum bicolor L.) plants grown in monocropping and intercropping systems was conducted to evaluate seed yield, dry matter production, total N yield, land equivalent ratio (LER), intraspecific competition for soil N uptake, water use efficiency (WUE) and N 2 -fixation using the 15 N natural abundance technique (δ 15 N ). Moreover, carbon isotope discrimination (Δ13 C ) was determined to assess factors responsible for crop performance variability in the different cropping systems. Intercropping of sesbania/sorghum showed greater efficiency over monocropping in producing dry matter, during the entire growth period, as indicated by the LERs (>1); whereas, the efficiency of producing dry matter in the sesbania /sunflower intercropping was similar to that in the monocropping system (LER=1). Moreover, sorghum plants (C 4 ) was more competitive than sesbania (C 3 ) for soil N uptake; whereas, sesbania seemed to be more competitive than its associated sunflower (C 3 ). N uptake in the mixed stand of sesbania/sorghum was improved due to the increase in soil N uptake by the component sorghum and the higher root nodule activity of component sesbania without affecting the amount of N 2 fixed. In both cropping systems, sesbania plants fixed almost the same amount of N 2 (an average of 105 kg N/ha) although the number of rows in the mixed stand was 2/3 of that in the pure stand. This gives an advantage of the intercropping over sole cropping system with regards to N 2 -fixation. 13 C discrimination in plant materials was found to be affected by plant species and the cropping system. Factors affected Δ13 C in plants grown in the mixed stand relative to solely grown crops are discussed.(author)

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.

Genetic Factors in Rhizobium Affecting the Symbiotic Carbon Costs of N2 Fixation and Host Plant Biomass Production

DEFF Research Database (Denmark)

Skøt, L.; Hirsch, P. R.; Witty, J. F.

1986-01-01

The effect of genetic factors in Rhizobium on host plant biomass production and on the carbon costs of N2 fixation in pea root nodules was studied. Nine strains of Rhizobium leguminosarum were constructed, each containing one of three symbiotic plasmids in combination with one of three different ...

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)

Individualized 3D printing navigation template for pedicle screw fixation in upper cervical spine.

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Fei Guo

Full Text Available Pedicle screw fixation in the upper cervical spine is a difficult and high-risk procedure. The screw is difficult to place rapidly and accurately, and can lead to serious injury of spinal cord or vertebral artery. The aim of this study was to design an individualized 3D printing navigation template for pedicle screw fixation in the upper cervical spine.Using CT thin slices data, we employed computer software to design the navigation template for pedicle screw fixation in the upper cervical spine (atlas and axis. The upper cervical spine models and navigation templates were produced by 3D printer with equal proportion, two sets for each case. In one set (Test group, pedicle screws fixation were guided by the navigation template; in the second set (Control group, the screws were fixed under fluoroscopy. According to the degree of pedicle cortex perforation and whether the screw needed to be refitted, the fixation effects were divided into 3 types: Type I, screw is fully located within the vertebral pedicle; Type II, degree of pedicle cortex perforation is 1 mm or with the poor internal fixation stability and in need of renovation. Type I and Type II were acceptable placements; Type III placements were unacceptable.A total of 19 upper cervical spine and 19 navigation templates were printed, and 37 pedicle screws were fixed in each group. Type I screw-placements in the test group totaled 32; Type II totaled 3; and Type III totaled 2; with an acceptable rate of 94.60%. Type I screw placements in the control group totaled 23; Type II totaled 3; and Type III totaled 11, with an acceptable rate of 70.27%. The acceptability rate in test group was higher than the rate in control group. The operation time and fluoroscopic frequency for each screw were decreased, compared with control group.The individualized 3D printing navigation template for pedicle screw fixation is easy and safe, with a high success rate in the upper cervical spine surgery.

Estimation of N2-fixation in cowpea grown in monoculture or in mixture with maize using 15 N

International Nuclear Information System (INIS)

Shammaa, Mouhammad; Kurd Ali, Fawaz

1994-01-01

A pot experiment was carried out under natural climatic conditions to determine the proportion of different nitrogen sources (air, soil, fertilizer) in cowpea and maize grown alone or in mixture using 15 N isotope dilution technique. On average, the proportion of N derived from fixation by cowpea grown in mixed culture was 55% lower than that derived by the sole cropped cowpea (77%). Dry matter produced by one plant of maize grown in mixed culture was twice as much as that produced by a plant grown in mono culture. Moreover, total nitrogen content in one maize plant grown in mixed culture was 213 mg higher than that determined by two plant of maize grown in mono culture (171 mg). However, the amount of nitrogen derived from soil by maize grown in mixed culture was equal or even higher than that taken up by two plants of maize grown in mono culture. This indicates a better utilization of soil N by the maize in mixed culture. This data emphasize the crucial role of interspecific competition in soil N uptake. Data from this study do not support the hypothesis of N transfer from the legume to the cereal because no significant differences were found between mixed and pure maize in terms of 15 N in excess content. (author). 9 refs., 1 tab

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)

A prospective randomised trial comparing mesh types and fixation in totally extraperitoneal inguinal hernia repairs.

Science.gov (United States)

Cristaudo, Adam; Nayak, Arun; Martin, Sarah; Adib, Reza; Martin, Ian

2015-05-01

The totally extraperitoneal (TEP) approach for surgical repair of inguinal hernias has emerged as a popular technique. We conducted a prospective randomised trial to compare patient comfort scores using different mesh types and fixation using this technique. Over a 14 month period, 146 patients underwent 232 TEP inguinal hernia repairs. We compared the comfort scores of patients who underwent these procedures using different types of mesh and fixation. A non-absorbable 15 × 10 cm anatomical mesh fixed with absorbable tacks (Control group) was compared with either a non-absorbable 15 × 10 cm folding slit mesh with absorbable tacks (Group 2), a partially-absorbable 15 × 10 cm mesh with absorbable tacks (Group 3) or a non-absorbable 15 × 10 cm anatomical mesh fixed with 2 ml fibrin sealant (Group 4). Outcomes were compared at 1, 2, 4 and 12 weeks using the Carolina Comfort Scale (CCS) scores. At 1, 2, 4 and 12 weeks, the median global CCS scores were low for all treatment groups. Statistically significant differences were seen only for median CCS scores and subscores with the use of partially-absorbable mesh with absorbable tacks (Group 3) at weeks 2 and 4. However, these were no longer significant at week 12. In this study, the TEP inguinal hernia repair with minimal fixation results in low CCS scores. There were no statistical differences in CCS scores when comparing types of mesh, configuration of the mesh or fixation methods. Copyright © 2015 IJS Publishing Group Limited. Published by Elsevier Ltd. All rights reserved.

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.

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)

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 ...

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

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

Comparing fixation used for calcaneal displacement osteotomies: a look at removal rates and cost.

Science.gov (United States)

Lucas, Douglas E; Simpson, G Alex; Philbin, Terrence M

2015-02-01

The calcaneal displacement osteotomy is a procedure frequently used by foot and ankle surgeons for hindfoot angular deformity. Traditional techniques use compression screw fixation that can result in prominent hardware. While the results of the procedure are generally good, a common concern is the development of plantar heel pain related to prominent hardware. The primary purpose of this study is to retrospectively compare clinical outcomes of 2 fixation methods for the osteotomy. Secondarily a cost analysis will compare implant costs to hardware removal costs. Records were reviewed for patients who had undergone a calcaneal displacement osteotomy fixated with either lag screw or a locked lateral compression plate (LLCP). Neuropathy, previous ipsilateral calcaneus surgery, heel pad trauma, or incomplete radiographic follow-up were exclusionary. Thirty-two patients (19.4%) required hardware removal from the screw fixation group compared to 1 (1.6%) of the LLCP group, which is significant (P cost was remarkably different with screw fixation costing on average $247.12, compared to the LLCP costing $1175.59. Although the LLCP cost was significantly higher, cost savings were identified when the cost of removal and removal rates were included. This study demonstrates that this device provides adequate stabilization for healing in equivalent time to screw fixation. The LLCP required decreased rates of hardware removal with fewer postoperative visits over a shorter period of time. Significant savings were demonstrated in the LLCP group despite the higher implant cost. Therapeutic, Level III, Retrospective Comparative Study. © 2014 The Author(s).

Dinitrogen fixation estimates in Vetch-barley swards using {sup 15} N-methodology

Energy Technology Data Exchange (ETDEWEB)

Kurdali, F; Sharabi, N E [Atomic Energy Commission, P.O.Box 6091, Damascus, (Syrian Arab Republic)

1995-10-01

N 2- fixation in vetch (Vicia Sativa) grown alone and in mixture with barley (hordeum vulgare) in pots was evaluated using {sup 15} N isotope dilution method. Two harvests were made over the growing season. The proportion of the above-ground N, derived from atmospheric N 2 (% Ndfa) in mixed vetch was significantly higher than that of vetch in pure culture for the different harvests. However, this increase was not accompanied with the amount of N 2-fixation. On the other hand, no significant differences were observed in N-content or in N-derived from soil between barley grown in mixture and in monoculture, in spite of the difference in the number of plants between the tow cropping systems. These results indicate a high competing capacity of barley for soil nitrogen in mixed culture. Barley grown together with vetch had lower atom % 15 N excess than barley grown in mono-culture because it may have received some of their N from N-released by the legume in the second herbage but not in the first. Overall, results obtained from this experiment indicate the importance of mixed crops for forage production. Based on these results, further investigation must carried out in the field. 1 fig.

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

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

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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.

Comparison of CO2 Fixation in Wood Used for Residence HOuses in Japan and Korea

OpenAIRE

Choi, Soo Im; Sakai, Masahiro; Jeong, In Soo; Oh, Seung Won; Kang, Hag Mo

2003-01-01

In this study, we have estimated the amount of carbon (C) fixation in wooden materials used for residence house units in Japan and Korea. This type of C fixation might be helpful to prevent the global warming. In year 2000, the amount of C fixation in the wooden materials was approximately 7.3% (150 million C ton) of total forest C accumulation in Japan, whereas in Korea, it was 2.0% (4.3million C ton) of the total forest C accumulation. The reason is that structural types of the house units ...

N fixation and transfer in Maize/Cowpea and Sorghum/Cowpea inter cropping systems as determined by N-15 isotope dilution technique

International Nuclear Information System (INIS)

Dayatilake, G.A.; Subasinghe, S.; Senaratne, R.

2000-01-01

N fixation and transfer in maize/cowpea and sorghum/cowpea intercropping systems, as determined by N-15 dilution technique was studied in two field trials conducted at Bata-atha, in the dry zone of Sri Lanka. Two cvs. of cowpea i.e; Bombay and MI-35 were used in maize/cowpea intercropping system, with following combinations of treatments; maize/Bombay, maize/MI-35, Bombay (monocrop), MI-35 (monocrop) and maize (monocrop). A similar set of treatments was used in sorghum/cowpea intercropping system also. The N-15 atom excess, percentage Ndfa, total amount of N fixed, N yield and the total dry matter production were estimated. Maize/cowpea intercropping resulted in an increase in total dry matter production and total N yield compared to monocrop treatment. However the percentage Ndfa and total N fixed showed a decrease compared to monocrop stand. The percentage Ndfa was 60-65 percent monocrop while the same was 45-50 percent in intercropped treatments

A Randomized Controlled Trial Comparing Suture-Fixation Mucopexy and Doppler-Guided Hemorrhoidal Artery Ligation in Patients with Grade III Hemorrhoids

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Min Zhai

2016-01-01

Full Text Available Background. We aimed to evaluate the effectiveness of a suture-fixation mucopexy procedure by comparing with Doppler-guided hemorrhoidal artery ligation (DGHAL in the management of patients with grade III hemorrhoids. Methods. This was a randomized controlled trial. One hundred patients with grade III hemorrhoids were randomly assigned to receive suture-fixation mucopexy (n=50 or DGHAL (n=50. Outcome assessments were performed at 2 weeks, 12 months, and 24 months. Assessments included resolution of clinical symptoms, postoperative complications, duration of hospitalization, and total costs. Results. At 2 weeks, one (2% patient in suture-fixation group and four (8% patients in DGHAL group had persistent prolapsing hemorrhoids. Postoperative bleeding was observed in two patients (4% in suture-fixation group and one patient in DGHAL group. There was no significant difference in short-term recurrence between groups. Postoperative complications and duration of hospitalization were comparable between the two groups. Rates of recurrence of prolapse or bleeding at 12 months did not differ between groups. However, recurrence of prolapse at 24 months was significantly more common in DGHAL group (19.0% versus 2.3%, p=0.030. Conclusions. Compared with DGHAL, the suture-fixation mucopexy technique had comparable short-term outcomes and favorable long-term outcomes.

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)

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

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)

Individualized 3D printing navigation template for pedicle screw fixation in upper cervical spine.

Science.gov (United States)

Guo, Fei; Dai, Jianhao; Zhang, Junxiang; Ma, Yichuan; Zhu, Guanghui; Shen, Junjie; Niu, Guoqi

2017-01-01

Pedicle screw fixation in the upper cervical spine is a difficult and high-risk procedure. The screw is difficult to place rapidly and accurately, and can lead to serious injury of spinal cord or vertebral artery. The aim of this study was to design an individualized 3D printing navigation template for pedicle screw fixation in the upper cervical spine. Using CT thin slices data, we employed computer software to design the navigation template for pedicle screw fixation in the upper cervical spine (atlas and axis). The upper cervical spine models and navigation templates were produced by 3D printer with equal proportion, two sets for each case. In one set (Test group), pedicle screws fixation were guided by the navigation template; in the second set (Control group), the screws were fixed under fluoroscopy. According to the degree of pedicle cortex perforation and whether the screw needed to be refitted, the fixation effects were divided into 3 types: Type I, screw is fully located within the vertebral pedicle; Type II, degree of pedicle cortex perforation is stability and no need to renovate; Type III, degree of pedicle cortex perforation is >1 mm or with the poor internal fixation stability and in need of renovation. Type I and Type II were acceptable placements; Type III placements were unacceptable. A total of 19 upper cervical spine and 19 navigation templates were printed, and 37 pedicle screws were fixed in each group. Type I screw-placements in the test group totaled 32; Type II totaled 3; and Type III totaled 2; with an acceptable rate of 94.60%. Type I screw placements in the control group totaled 23; Type II totaled 3; and Type III totaled 11, with an acceptable rate of 70.27%. The acceptability rate in test group was higher than the rate in control group. The operation time and fluoroscopic frequency for each screw were decreased, compared with control group. The individualized 3D printing navigation template for pedicle screw fixation is easy and safe

Effect of sheep manure and phosphorus application on growth, yield, and N2 - fixation of inoculated soybean (Glycine max (L.) Merr) grown on Syrian arid soils using the 15N isotopic dilution technique

International Nuclear Information System (INIS)

Khalifa, Kh.; Al-Ain, F.; Al-Shamma'a, M.

2003-10-01

A field experiment was carried out in Syrian arid soils at Deir Al-Hajar research station to study the effect of different rates of sheep manure (0, 20, and 40 ton/ha) and levels of P- fertilizer (0, 40 and 80 kg P 2 O 5 /ha) on dry matter production and N 2 fixation by Soybean [(Glycine max) (SB171 variety)], of which seeds were inoculated by Bradyrhizobium japonicum-FA3 bacterial. Sorghum bicolor L. was employed as a reference crop ti evaluate N 2 -fixation using the 15 N-isotope dilution technique. In general, results indicated that, a positive effects were found to adding Sheep Manure or P-fertilizer on D.M production in different plants parts of soybean (shoots, roots, pods). This effect was more pronounced when adding sheep manure and phosphorus together especially under the optimum M40P80 treatment. Quantity of N-fixed by Soybean responds positively to sole application of Sheep Manure or P-fertilizer. Moreover, the optimum combined treatment showed significant increases in the quantity of nitrogen derived from the atmosphere (Qndfa), which were (3.29, 25.54, 53.49 kg N/ha) in roots, shoots, and pods respectively. P-fertilization resulted in a significant increase in the percentage of nitrogen use efficiency (NUE) with increasing phosphorus levels added to Sorghum plants; However, an adverse effect was noticed for the NUE when using sheep manure solely or in combination with P-fertilizer. (author)

Ball-joint versus single monolateral external fixators for definitive treatment of tibial shaft fractures.

Science.gov (United States)

Beltsios, Michail; Mavrogenis, Andreas F; Savvidou, Olga D; Karamanis, Eirineos; Kokkalis, Zinon T; Papagelopoulos, Panayiotis J

2014-07-01

To compare modular monolateral external fixators with single monolateral external fixators for the treatment of open and complex tibial shaft fractures, to determine the optimal construct for fracture union. A total of 223 tibial shaft fractures in 212 patients were treated with a monolateral external fixator from 2005 to 2011; 112 fractures were treated with a modular external fixator with ball-joints (group A), and 111 fractures were treated with a single external fixator without ball-joints (group B). The mean follow-up was 2.9 years. We retrospectively evaluated the operative time for fracture reduction with the external fixator, pain and range of motion of the knee and ankle joints, time to union, rate of malunion, reoperations and revisions of the external fixators, and complications. The time for fracture reduction was statistically higher in group B; the rate of union was statistically higher in group B; the rate of nonunion was statistically higher in group A; the mean time to union was statistically higher in group A; the rate of reoperations was statistically higher in group A; and the rate of revision of the external fixator was statistically higher in group A. Pain, range of motion of the knee and ankle joints, rates of delayed union, malunion and complications were similar. Although modular external fixators are associated with faster intraoperative fracture reduction with the external fixator, single external fixators are associated with significantly better rates of union and reoperations; the rates of delayed union, malunion and complications are similar.

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.

Comparison of /sup 15/N-aided methods for determining symbiotic dinitrogen fixation

Energy Technology Data Exchange (ETDEWEB)

Rennie, R J [International Atomic Energy Agency, Vienna (Austria). Joint FAO/IAEA Div. of Atomic Energy in Food and Agriculture

1979-01-01

Three methods of calculating the amount of symbiotic dinitrogen fixation in navy beans (Phaseolus vulgaris cv. Sanilac) were compared in a greenhouse experiment. /sup 15/N-isotope dilution procedures yielded the most logical estimation of dinitrogen fixation. The classical difference method was not in agreement. Potential errors of the 'A'-value procedure to calculate dinitrogen fixation are discussed.

The Free-Hand Technique for S2-Alar-Iliac Screw Placement: A Safe and Effective Method for Sacropelvic Fixation in Adult Spinal Deformity.

Science.gov (United States)

Shillingford, Jamal N; Laratta, Joseph L; Tan, Lee A; Sarpong, Nana O; Lin, James D; Fischer, Charla R; Lehman, Ronald A; Kim, Yongjung J; Lenke, Lawrence G

2018-02-21

Spinopelvic fixation is an integral part of achieving solid fusion across the lumbosacral junction, especially in deformity procedures requiring substantial correction or long-segment constructs. Traditional S2-alar-iliac (S2AI) screw-placement techniques utilize fluoroscopy, increasing operative time and radiation exposure to the patient and surgeon. We describe a novel free-hand technique for S2AI screw placement in patients with adult spinal deformity. We reviewed the records of 45 consecutive patients who underwent spinopelvic fixation performed with use of S2AI screws by the senior surgeon and various fellows or residents over a 12-month period (2015 to 2016). In each case, the S2AI screws were placed utilizing a free-hand technique without fluoroscopic or image guidance. Screw position and accuracy were assessed by intraoperative O-arm imaging and analyzed using 3-dimensional interactive manipulation of computed tomography images. A total of 100 screws were placed, 51 by the senior surgeon and 49 by trainees. The mean patient age was 57.4 ± 12.7 years at the time of surgery; 37 (82.2%) of the patients were female. Preoperative diagnoses included adult idiopathic scoliosis (n = 19), adult degenerative scoliosis (n = 15), flatback syndrome (n = 2), fixed sagittal imbalance (n = 6), and distal junctional kyphosis (n = 3). Five (5%) of the screws were placed with moderate to severe cortical breaches, all of which perforated the pelvis posteriorly, with no clinically notable neurovascular or visceral complications. The breach rate did not differ significantly between the senior surgeon and trainees. The free-hand technique for S2AI screw placement, when performed in a standardized manner, was demonstrated to be safe and reliable in constructs requiring spinopelvic fixation. The accuracy of screw placement relies on visible and palpable anatomic landmarks that obviate the need for intraoperative fluoroscopy or image guidance, potentially reducing operative time

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.

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.

Evaluation of options relative to the fixation and disposal of 14C-contaminated CO2 as CaCO3

International Nuclear Information System (INIS)

Croff, A.G.

1976-04-01

A paper study was conducted to determine the best method for fixing the 14 C-contaminated CO 2 resulting from an HTGR fuel block burner as CaCO 3 , and to determine the best methods for disposing of the CaCO 3 thus produced. The fixation method selected was the direct reaction of a Ca(OH) 2 slurry with the CO 2 . The least expensive disposal options which are likely to be acceptable appear to be the shallow-land burial of either drummed CaCO 3 solid (total cost = $18.47/kg heavy metal) or drummed CaCO 3 concreted with cement (total cost = $43.33/kg heavy metal). Neither placing the CO 2 fixation process before the Kr removal process nor separating the bulk of the graphite fuel block from the fuel particles is attractive on both technical and economic grounds. However, reduction of the HTGR fuel nitrogen content appears to be a more attractive method of reducing the 14 C release rate

[Complications of open reduction and internal fixation versus external fixation for unstable distal radius fractures: a meta-analysis].

Science.gov (United States)

Yang, Z; Yuan, Z Z; Ma, J X; Ma, X L

2016-12-20

Objective: To make a systematic assessment of the complications of open reduction and internal fixation versus external fixation for unstable distal radius fractures. Method: A computer-based online search of PubMed, ScienceDirect, EMBASE, BIOSIS, Springer and Cochrane Library were performed.The randomized and controlled trials of open reduction and internal fixation versus external fixation for unstable distal radius fractures were collected.The included trials were screened out strictly based on the criterion of inclusion and exclusion.The quality of included trials was evaluated.RevMan 5.0 was used for data analysis. Result: A total of 17 studies involving 1 402 patients were included.There were 687 patients with open reduction and internal fixation and 715 with external fixation.The results of Meta-analysis indicated that there were statistically significant differences with regard to the postoperatively total complications, infection, malunion, tendon rupture ( I 2 =8%, RR =0.77(95% CI 0.65-0.91, Z =3.10, P 0.05). Conclusion: Postoperative complications are present in both open reduction and internal fixation and external fixation.Compared with external fixation, open reduction and internal fixation is lower in total complications postoperatively, infection and malunion, but external fixation has lower tendon rupture incidence.

Fixation of Light Weight Polypropylene Mesh with n-Butyl-2-cyanocrylate in Pelvic Floor Surgery: Experimental Design Approach in Sheep for Effectiveness Evaluation

Directory of Open Access Journals (Sweden)

Sandra Barbosa

2015-01-01

Full Text Available Objective. The aim of this study was to find a proper experimental design and to evaluate n-butyl-2-cyanoacrylate (Histoacryl as a fixation method for a light-weight and large pore PP mesh (Synthetic PP Mesh-1 using the sheep as an animal model. Methods. Posterior vaginal implantation by means of episiotomy was used to implant 8 ewes which were evaluated macroscopically and histologically at 3 months (n=4 and 6 months (n=4 post-surgery. In previous pilot studies anterior vaginal implantation was evaluated, as well as different synthetic mesh materials, sizes and fixation methods (n=1 to 3 during three weeks. In all cases a clinical evaluation of the animal was performed. Results. A reduction in the mesh size (Synthetic PP Mesh-1 together with precise application of the surgical glue Histoacryl to fix the mesh yielded significantly better histocompatibility results (P<0.01 compared to larger size or other fixation methods. Conclusion. The combination of Synthetic PP Mesh-1 with Histoacryl offered a high degree of graft integration without vaginal ulceration and a minimal foreign body reaction, being the sheep a proper animal model to test these types of medical devices.

Farmers' agronomic and social evaluation of productivity yield and N2-fixation in different cowpea varieties and their subsequent residual N effects on a succeeding maize crop

NARCIS (Netherlands)

Adjei-Nsiah, S.; Kuyper, T.W.; Leeuwis, C.; Abekoe, M.K.; Cobbinah, J.; Sakyi-Dawson, O.; Giller, K.E.

2008-01-01

Cowpea-maize rotations form an important component of the farming systems of smallholder farmers in the forest/savannah transitional agro-ecological zone of Ghana. We evaluated five cowpea varieties for grain yield, N-2-fixation, biomass production, and contribution to productivity of subsequent

Carbon dioxide fixation in isolated Kalanchoe chloroplasts

Energy Technology Data Exchange (ETDEWEB)

Levi, C.; Gibbs, M.

1975-07-01

Chloroplasts isolated from Kalanchoe diagremontiana leaves were capable of photosynthesizing at a rate of 5.4 ..mu..moles of CO/sub 2/ per milligram of chlorophyll per hour. The dark rate of fixation was about 1 percent of the light rate. A high photosynthetic rate was associated with low starch content of the leaves. Ribose 5-phosphate, fructose 1, 6-diphosphate, and dithiothreitol stimulated fixation, whereas phosphoenolpyruvate and azide were inhibitors. The products of CO/sub 2/ fixation were primarily those of the photosynthetic carbon reduction cycle. (auth)

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.

Comparative Effects of Cowpea and Soybean Genotypes on N2 ...

African Journals Online (AJOL)

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ABSTRACT:A field trial was conducted to asses N2 - fixation and N balance in five cultivars each of soybean (TGX 1945 – 1F, ... Key words: Legume genotype, N2 fixation, N balance and Nitrogen Harvest Index (NHI) ..... subsequent maize grain yield in the guinea savanna ... On-farm evaluation of biological nitrogen fixation.

Theoretical implications for the estimation of dinitrogen fixation by large perennial plant species using isotope dilution

Science.gov (United States)

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

1995-01-01

Estimation of symbiotic N2 fixation associated with large perennial plant species, especially trees, poses special problems because the process must be followed over a potentially long period of time to integrate the total amount of fixation. Estimations using isotope dilution methodology have begun to be used for trees in field studies. Because...

Evaluation for dinitrogen fixation of induced wheat nodules by 15N isotope dilution method

International Nuclear Information System (INIS)

Yao Yunyin; Zhen Ming; Chang Xizhong

1993-11-01

The results in pot experiments showed that the treating of 2,4-D and Azorhizobium caulinodans (2,4-D+A) could induce para-nodule formation on wheat roots. Plants treated grew normally. The plant height and dry weight are significantly higher than reference plants which are treated with 2,4-D+azorhizobium sterilized (2,4-D+AS). The nitrogenase activity is detected by ARA method. The N yield of most treated plants, especially in root systems, is higher than reference group that is measured by Kjeldahl method. The atom % 15 N excess in leaf and stem of treated plants measured by 15 N isotope dilution method is lower than that of reference group. Through four years experiments, it shows that para-nodules of wheat treated with 2,4-D+A could fix N 2 from air, but the ability of nitrogen fixation is lower and unstable. Although the nodulation efficiency could reach 100%, not each para-nodule induced can present activity of dinitrogen fixation. The amount of N fixed is 0.05∼18.1 mg/pot (0.01∼3.87 mg/plant). The net %Ndfa is 2.32%∼18.07%. The free-living N 2 fixing activity of azorhizobium is detected by 15 N isotope dilution method. The calculation of %Ndfa of nodulated wheat accurately is also discussed

Nitrogen fixation in denitrified marine waters.

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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.

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

Carbon Dioxide Fixation in Isolated Kalanchoe Chloroplasts 1

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Levi, Carolyn; Gibbs, Martin

1975-01-01

Chloroplasts isolated from Kalanchoe diagremontiana leaves were capable of photosynthesizing at a rate of 5.4 μmoles of CO2 per milligram of chlorophyll per hour. The dark rate of fixation was about 1% of the light rate. A high photosynthetic rate was associated with low starch content of the leaves. Ribose 5-phosphate, fructose 1,6-diphosphate, and dithiothreitol stimulated fixation, whereas phosphoenolpyruvate and azide were inhibitors. The products of CO2 fixation were primarily those of the photosynthetic carbon reduction cycle. PMID:16659249

14CO2 fixation pattern of cyanobacteria

International Nuclear Information System (INIS)

Erdmann, N.; Schiewer, U.

1985-01-01

The 14 CO 2 fixation pattern of three cyanobacteria in the light and dark were studied. Two different chromatographic methods widely used for separating labelled photosynthetic intermediates were compared. After ethanolic extraction, a rather uniform fixation pattern reflecting mainly the β-carboxylation pathway is obtained for all 3 species. Of the intermediates, glucosylglycerol is specific and high citrulline and low malate contents are fairly specific to cyanobacteria. The composition of the 14 CO 2 fixation pattern is hardly affected by changes in temperature or light intensity, but it is severely affected by changes in the water potential of the medium. (author)

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

Global metabolic rewiring for improved CO2 fixation and chemical production in cyanobacteria

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Kanno, Masahiro; Carroll, Austin L.; Atsumi, Shota

2017-03-01

Cyanobacteria have attracted much attention as hosts to recycle CO2 into valuable chemicals. Although cyanobacteria have been engineered to produce various compounds, production efficiencies are too low for commercialization. Here we engineer the carbon metabolism of Synechococcus elongatus PCC 7942 to improve glucose utilization, enhance CO2 fixation and increase chemical production. We introduce modifications in glycolytic pathways and the Calvin Benson cycle to increase carbon flux and redirect it towards carbon fixation. The engineered strain efficiently uses both CO2 and glucose, and produces 12.6 g l-1 of 2,3-butanediol with a rate of 1.1 g l-1 d-1 under continuous light conditions. Removal of native regulation enables carbon fixation and 2,3-butanediol production in the absence of light. This represents a significant step towards industrial viability and an excellent example of carbon metabolism plasticity.

Effect of planting patterns on dinitrogen fixation of alfalfa and transfer of N fixed

International Nuclear Information System (INIS)

Yao Yunyin; Chen Ming; Zhang Xizhong

1993-01-01

Contribution of symbiotic nitrogen fixation of alfalfa grown with different planting patterns was studied in a field experiment. %Ndfa and Ndfa in alfalfa and N transferred from alfalfa in meadow fescue were examined by 2 kinds of 15 N tracer techniques. The superiority of mixed culture of legumes with grasses to monoculture was influenced by planting patterns. Biomass in a mixed culture was related to proportion of alfalfa in it. The proportion of alfalfa was in close relationship not only with ratio of their seeds, but also with planting patterns. Row seeding in mixed seeds was better than broadcasting or intercropping in hay yield, total N yield and %Ndfa and Ndfa. It was also higher than the average of corresponding item of alfalfa and meadow fescue in monoculture each equal area. There was no significantly difference (P 15 N isotope dilution method and natural 1 '5N abundance method. N in meadow fescue transferred from alfalfa could be accurately determined by 15 N isotope diffusion method, but 15 N abundance method gave underestimates, even could not examined N in grasses transferred from associated legumes

Systematics in total (n,2n) cross sections at 14 MeV

Energy Technology Data Exchange (ETDEWEB)

Garg, K C; Khurana, C S [Punjabi Univ., Patiala (India). Nuclear Science Labs.

1976-11-20

The 14-15 MeV (n,2n) cross sections are found to depend mainly on the asymmetry parameter and the Q-value. No shell effects are found to exist in these cross sections. The total (n,2n) cross sections are found to be well predicted by an empirical relation which takes into account the Q-value and the asymmetry parameter in addition to the geometrical cross section.

NanoSIMS Analyses of Mo Indicate Nitrogenase Activity and Help Solve a N and C Fixation Puzzle in a Marine Cyanobacterium

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Pett-Ridge, J.; Weber, P. K.; Finzi, J.; Hutcheon, I. D.; Capone, D. G.

2006-12-01

Diazotrophic cyanobacteria are capable of both CO2 and N2 fixation, yet must separate these two functions because the nitrogenase enzymes used in N2 fixation are strongly inhibited by O2 produced during photosynthesis. Some lineages, such as Anabaena, use specialized cells (heterocysts) to maintain functional segregation. However the mechanism of this segregation is poorly understood in Trichodesmium, a critical component of marine primary production in the tropical and subtropical North Atlantic. While some Trichodesmium studies suggest a temporal segregation of the nitrogen and carbon fixing processes, others indicate nitrogen fixation is spatially isolated in differentiated cells called diazocytes. In order to isolate the intracellular location of N fixation in both species, we used a combination of TEM, SEM and NanoSIMS analysis to map the distribution of C, N and Mo (a critical nitrogenase co-factor) isotopes in intact cells. NanoSIMS is a powerful surface analysis tool which combines nanometer-scale imaging resolution with the high sensitivity of mass spectrometry. Using cells grown in a 13CO^2 and 15N2 enriched atmosphere, our analyses indicate that in Anabaena, heterocysts are consistently enriched in Mo, and Mo accumulation suggests active N fixation (as opposed to N storage). In the non- heterocystous Trichodesmium, Mo is concentrated in sub-regions of individual cells, and is not associated with regions of N storage (cyanophycin granules). We suggest that NanoSIMS mapping of metal enzyme co- factors is a unique method of identifying physiological and morphological characteristics within individual bacterial cells. This combination of NanoSIMS analysis and high resolution microscopy allows isotopic analysis to be linked to morphological features and holds great promise for fine-scale studies of bacteria metabolism.

Quantification of Atmospheric N2 Fixed by Cowpea, Pigeonpea and ...

African Journals Online (AJOL)

at taking advantage of legumes to replenish soil nitrogen (N due to legumes' N2 fixation). Glasshouse pot ... In both cases, maize (Katumani variety) was the non- N2- fixing reference crop. ... Biological N2 fixation is affected by several factors,.

[Comparison of external fixation with or without limited internal fixation for open knee fractures].

Science.gov (United States)

Li, K N; Lan, H; He, Z Y; Wang, X J; Yuan, J; Zhao, P; Mu, J S

2018-03-01

Objective: To explore the characteristics and methods of different fixation methods and prevention of open knee joint fracture. Methods: The data of 86 cases of open knee joint fracture admitted from January 2002 to December 2015 in Department of Orthopaedics, Affiliated Hospital of Chengdu University were analyzed retrospectively.There were 65 males and 21 females aged of 38.6 years. There were 38 cases treated with trans articular external fixation alone, 48 cases were in the trans articular external fixation plus auxiliary limited internal fixation group. All the patients were treated according to the same three stages except for different fixation methods. Observation of external fixation and fracture fixation, fracture healing, wound healing and treatment, treatment and related factors of infection control and knee function recovery. χ(2) test was used to analyze data. Results: Eleven patients had primary wound healing, accounting for 12.8%. Seventy-five patients had two wounds healed, accounting for 87.2%. Only 38 cases of trans articular external fixator group had 31 cases of articular surface reduction, accounting for 81.6%; Five cases of trans articular external fixator assisted limited internal fixation group had 5 cases of poor reduction, accounting for 10.4%; There was significant difference between the two groups (χ(2)=44.132, P external fixation group, a total of 23 cases of patients with infection, accounted for 60.5% of external fixation group; trans articular external fixation assisted limited internal fixation group there were 30 cases of patients with infection, accounting for the assistance of external fixator and limited internal fixation group 62.5%; There was significant difference between the two groups(χ(2)=0.035, P >0.05). Five cases of fracture nonunion cases of serious infection, patients voluntarily underwent amputation. The Lysholm Knee Scale: In the external fixation group, 23 cases were less than 50 points, accounting for 60

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.

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)

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

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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.

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

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)

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.

Stent migration following endoscopic suture fixation of esophageal self-expandable metal stents: a systematic review and meta-analysis.

Science.gov (United States)

Law, Ryan; Prabhu, Anoop; Fujii-Lau, Larissa; Shannon, Carol; Singh, Siddharth

2018-02-01

Covered self-expandable metal stents (SEMS) are utilized for the management of benign and malignant esophageal conditions; however, covered SEMS are prone to migration. Endoscopic suture fixation may mitigate the migration risk of covered esophageal SEMS. Hence, we conducted a systematic review and meta-analysis to evaluate the effectiveness and safety of endoscopic suture fixation for covered esophageal SEMS. Following PRISMA guidelines, we performed a systematic review from 2011 to 2016 to identify studies (case control/case series) reporting the technical success and migration rate of covered esophageal SEMS following endoscopic suture fixation. We searched multiple electronic databases and conference proceedings. We calculated pooled rates (and 95% confidence intervals [CI]) of technical success and stent migration using a random effects model. We identified 14 studies (212 patients) describing covered esophageal SEMS placement with endoscopic suture fixation. When reported, SEMS indications included leak/fistula (n = 75), stricture (n = 65), perforation (n = 10), and achalasia (n = 4). The pooled technical success rate was 96.7% (95% CI 92.3-98.6), without heterogeneity (I 2  = 0%). We identified 29 SEMS migrations at rate of 15.9% (95% CI 11.4-21.6), without heterogeneity (I 2  = 0%). Publication bias was observed, and using the trim-and-fill method, a more conservative estimate for stent migration was 17.0%. Suture-related adverse events were estimated to occur in 3.7% (95% CI 1.6-8.2) of cases. Endoscopic suture fixation of covered esophageal SEMS appears to reduce stent migration when compared to published rates of non-anchored SEMS. However, SEMS migration still occurs in approximately 1 out of 6 cases despite excellent immediate technical success and low risk of suture-related adverse events.

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

Evaluating the impact of atmospheric depositions on springtime dinitrogen fixation in the Cretan Sea (Eastern Mediterranean - A mesocosm approach

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Eyal Rahav

2016-09-01

Full Text Available Large amounts of dust and atmospheric aerosols, originating from surrounding desert areas (e.g., Sahara and Middle East are deposited annually on the surface of the Eastern Mediterranean Sea. These depositions can provide high amounts of micro (such as Fe, Zn, Co and macro nutrients (such as P and N to supplement nutrient-poor surface waters- that typically limit primary productivity and also dinitrogen (N2 fixation in many marine environments. Here, we studied the impact of the atmospheric deposition of dust and aerosols on N2 fixation in the Cretan Sea (Eastern Mediterranean Sea. Mixed polluted aerosols (hereafter A and Saharan dust (hereafter SD were added to nine mesocosms (3-m3 each containing surface mixed layer seawater (~10 m, and N2 fixation was evaluated for 6 days during May 2012 (springtime. The addition of SD triggered a rapid (30 h and robust (2-4 fold increase in N2 fixation rates that remained high for 6 days and contributed 3-8% of the primary productivity. The A addition also resulted in higher N2 fixation rates compared to the unamended control mesocosms, although the responses were less profound (1.5-2 fold and accounted for only 2-4% of the primary productivity. The microbial community responded differently to the two additions. Heterotrophic bacterial N2 fixers dominated the diazotroph community in A and the control mesocosms, while the non-filamentous cyanobacterial group Trichodesmium prevailed in the SD treatment (68% of all the operational taxonomic units, verified by qPCR analyses. Our results indicate that the aerosol source, its route prior to deposition, and its specific chemical composition, can alter the diazotrophic diversity and activity in the Eastern Mediterranean Sea and may thus impact both the N and C dynamics in this impoverished environment.

Incidence of infection after early intramedullary nailing of open tibial shaft fractures stabilized with pinless external fixators

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Kulshrestha Vikas

2008-01-01

Full Text Available Background: A major drawback of conventional fixator system is the penetration of fixator pins into the medullary canal. The pins create a direct link between the medullary cavity and outer environment, leading to higher infection rates on conversion to intramedullary nailing. This disadvantage is overcome by the AO pinless fixator, in which the trocar points are clamped onto the outer cortex without penetrating it. This study was designed to evaluate the role of AO pinless fixators in primary stabilization of open diaphyseal tibial fractures that received staged treatment because of delayed presentation or poor general condition. We also analyzed the rate of infection on early conversion to intramedullary nail. Materials and Methods: This study is a retrospective review of 30 open diaphyseal fractures of tibia, which were managed with primary stabilization with pinless fixator and early exchange nailing. Outcome was evaluated in terms of fracture union and rate of residual infection. The data were compared with that available in the literature. Results: All the cases were followed up for a period of 2 years. The study includes Gustilo type 1 (n=10, 14 Gustilo type 2 (n=14, and type3 (n=6 cases. 6 cases (20% had clamp site infection, 2 cases (6.7% had deep infection, and in 28 cases (93% the fracture healed and consolidated well. Conclusion: This study has highlighted the valuable role of pinless external fixator in the management of open tibial fractures in terms of safety and ease of application as well as the advantage of early conversion to intramedullary implant without the risk of deep infection.

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

Biomechanical comparison of supraacetabular external fixation and anterior pelvic bridge plating.

Science.gov (United States)

Çavuşoğlu, Ali Turgay; Erbay, Fatma Kübra; Özsoy, Mehmet Hakan; Demir, Teyfik

2017-10-01

Unstable pelvic ring injuries are complex and risky injuries due to high morbidity and mortality. Although anterior pelvic external fixator is a suitable method for rapid stabilization of an injured pelvic ring, due to some disadvantages such as high complication rate, nerve damage, and difficulties of patient's mobility and comfort, there has recently been increased searching for alternative methods for stabilization of the pelvic ring. Pubic symphysis zone freely moves in pelvic models. This study aims to evaluate the biomechanical stability of anterior pelvic bridge plating and compare it with supraacetabular external fixators in an untreated unstable pelvic fracture model. Samples were loaded statically with 2-mm/min loading rate in single leg standing position. Maximum load was 2.3 kN. When loading the samples, photographs were taken continuously. Stiffness values were calculated from the load displacement curves. Some reference parameters were described and were measured from unloaded and 2.3-kN-loaded photographs of the test. The mean stiffness values were 491.14 ± 52.22, 478.55 ± 41.44, and 470.25 ± 44.51 N/mm for anterior pelvic bridge plating group, supraacetabular external fixator group, and Control group, respectively. According to the measured parameters from photographs, the mean displacement at the pubic symphysis was 4.7 ± 0.32, 15.8 ± 2.01, and 18.2 ± 0.47 mm for anterior pelvic bridge plating, supraacetabular external fixator, and Control group, respectively. The highest displacement in the pubic symphysis was found in Control group, and minimum displacement was observed in anterior pelvic bridge plating group. When the perpendicular distance between the right and left lower end of ischium was examined, it was observed that displacement was minimum in anterior pelvic bridge plating group compared to other two groups, regarding to the high stability of pubic symphysis. In conclusion, this study revealed

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)

Comparison of skeletal stability after sagittal split ramus osteotomy among mono-cortical plate fixation, bi-cortical plate fixation, and hybrid fixation using absorbable plates and screws.

Science.gov (United States)

Ueki, Koichiro; Moroi, Akinori; Yoshizawa, Kunio; Hotta, Asami; Tsutsui, Takamitsu; Fukaya, Kenichi; Hiraide, Ryota; Takayama, Akihiro; Tsunoda, Tatsuta; Saito, Yuki

2017-02-01

The purpose of this study was to examine skeletal stability and plate breakage after sagittal split ramus osteotomy (SSRO) with the mono-cortical plate fixation, bi-cortical plate fixation, and hybrid fixation techniques using absorbable plates and screws. A total of 76 Japanese patients diagnosed with mandibular prognathism with and without maxillary deformity were divided into 3 groups randomly. A total of 28 patients underwent SSRO with mono-cortical plate fixation, 23 underwent SSRO with bi-cortical plate fixation, and 25 underwent SSRO with hybrid fixation. Skeletal stability and horizontal condylar angle were analyzed by axial, frontal, and lateral cephalograms from before the operation to 1 year postoperatively. Breakage of the plate and screws was observed by 3-dimensional computed tomography (3DCT) immediately after surgery and after 1 year. Although there was a significant difference between the mono-cortical plate fixation group and hybrid fixation group regarding right MeAg in T1 (P = 0.0488) and occlusal plane in T1 (P = 0.0346), there were no significant differences between the groups for the other measurements in each time interval. In 2 cases, namely, 6 sides in the mono-cortical plate fixation group, breakage of the absorbable plate was found by 3DCT. However, there was no breakage in the bi-cortical plate fixation group and hybrid fixation group. This study results suggested that there were no significant differences in the postoperative skeletal stability among the 3 groups, and bi-cortical fixation as well as hybrid fixation was a reliable and useful method to prevent plate breakage even if an absorbable material was used. Copyright © 2016 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Tracing nitrogen accumulation in decaying wood and examining its impact on wood decomposition rate

Science.gov (United States)

Rinne, Katja T.; Rajala, Tiina; Peltoniemi, Krista; Chen, Janet; Smolander, Aino; Mäkipää, Raisa

2016-04-01

Decomposition of dead wood, which is controlled primarily by fungi is important for ecosystem carbon cycle and has potentially a significant role in nitrogen fixation via diazotrophs. Nitrogen content has been found to increase with advancing wood decay in several studies; however, the importance of this increase to decay rate and the sources of external nitrogen remain unclear. Improved knowledge of the temporal dynamics of wood decomposition rate and nitrogen accumulation in wood as well as the drivers of the two processes would be important for carbon and nitrogen models dealing with ecosystem responses to climate change. To tackle these questions we applied several analytical methods on Norway spruce logs from Lapinjärvi, Finland. We incubated wood samples (density classes from I to V, n=49) in different temperatures (from 8.5oC to 41oC, n=7). After a common seven day pre-incubation period at 14.5oC, the bottles were incubated six days in their designated temperature prior to CO2 flux measurements with GC to determine the decomposition rate. N2 fixation was measured with acetylene reduction assay after further 48 hour incubation. In addition, fungal DNA, (MiSeq Illumina) δ15N and N% composition of wood for samples incubated at 14.5oC were determined. Radiocarbon method was applied to obtain age distribution for the density classes. The asymbiotic N2 fixation rate was clearly dependent on the stage of wood decay and increased from stage I to stage IV but was substantially reduced in stage V. CO2 production was highest in the intermediate decay stage (classes II-IV). Both N2 fixation and CO2 production were highly temperature sensitive having optima in temperature 25oC and 31oC, respectively. We calculated the variation of annual levels of respiration and N2 fixation per hectare for the study site, and used the latter data together with the 14C results to determine the amount of N2 accumulated in wood in time. The proportion of total nitrogen in wood

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

Mini-Fragment Fixation Is Equivalent to Bicortical Screw Fixation for Horizontal Medial Malleolus Fractures.

Science.gov (United States)

Wegner, Adam M; Wolinsky, Philip R; Robbins, Michael A; Garcia, Tanya C; Amanatullah, Derek F

2018-05-01

Horizontal fractures of the medial malleolus occur through application of valgus or abduction force through the ankle that creates a tension failure of the medial malleolus. The authors hypothesize that mini-fragment T-plates may offer improved fixation, but the optimal fixation construct for these fractures remains unclear. Forty synthetic distal tibiae with identical osteotomies were randomized into 4 fixation constructs: (1) two parallel unicortical cancellous screws; (2) two parallel bicortical cortical screws; (3) a contoured mini-fragment T-plate with 2 unicortical screws in the fragment and 2 bicortical screws in the shaft; and (4) a contoured mini-fragment T-plate with 2 bicortical screws in the fragment and 2 unicortical screws in the shaft. Specimens were subjected to offset axial tension loading on a servohydraulic testing system and tracked using high-resolution video. Failure was defined as 2 mm of articular displacement. Analysis of variance followed by a Tukey-Kramer post hoc test was used to assess for differences between groups, with significance defined as Pfragment T-plate constructs (239±83 N/mm and 190±37 N/mm) and the bicortical screw construct (240±17 N/mm) were not statistically different. The mean stiffness values of both mini-fragment T-plate constructs and the bicortical screw construct were higher than that of a parallel unicortical screw construct (102±20 N/mm). Contoured T-plate constructs provide stiffer initial fixation than a unicortical cancellous screw construct. The T-plate is biomechanically equivalent to a bicortical screw construct, but may be superior in capturing small fragments of bone. [Orthopedics. 2018; 41(3):e395-e399.]. Copyright 2018, SLACK Incorporated.

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...

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

The complex effects of ocean acidification on the prominent N2-fixing cyanobacterium Trichodesmium.

Science.gov (United States)

Hong, Haizheng; Shen, Rong; Zhang, Futing; Wen, Zuozhu; Chang, Siwei; Lin, Wenfang; Kranz, Sven A; Luo, Ya-Wei; Kao, Shuh-Ji; Morel, François M M; Shi, Dalin

2017-05-05

Acidification of seawater caused by anthropogenic carbon dioxide (CO 2 ) is anticipated to influence the growth of dinitrogen (N 2 )-fixing phytoplankton, which contribute a large fraction of primary production in the tropical and subtropical ocean. We found that growth and N 2 -fixation of the ubiquitous cyanobacterium Trichodesmium decreased under acidified conditions, notwithstanding a beneficial effect of high CO 2 Acidification resulted in low cytosolic pH and reduced N 2 -fixation rates despite elevated nitrogenase concentrations. Low cytosolic pH required increased proton pumping across the thylakoid membrane and elevated adenosine triphosphate production. These requirements were not satisfied under field or experimental iron-limiting conditions, which greatly amplified the negative effect of acidification. Copyright © 2017, American Association for the Advancement of Science.

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)

Photosynthetic CO2 fixation in guard cells (GC)

International Nuclear Information System (INIS)

Gotow, K.; Taylor, S.; Zeiger, E.

1987-01-01

Recent studies indicate that carbon metabolism in GC is modulated by light quality. The fate of 14 CO 2 supplied to highly purified Vicia GC protoplasts irradiated with red light was investigated. The suspension was stirred at 25 0 C and dark-adapted for 5 min. After 5 min. in red light, 4.8 uCi of NaH 14 CO 3 was added (final concentration: 100 uM). Metabolism was quenched after 30 s with boiling ethanol. Anionic compounds were separated by 2D PC and TLC, and quantified. Rates of CO 2 fixation were 5- to 8-fold higher in the light. In the dark, malate and aspartate had 90% of the total label; in the light, 3-PGA, sugar monophosphates (SMP) and sugar diophosphates (SDP) had up to 60% of the label. Phosphates treatment and rechromatography of labelled SDP showed the presence of ribulose, a specific PCRP metabolite. In time-course experiments, labelled 3-PGA was detected within 5 s. With time, the percentage of label in 3-PGA decreased and that in SMP increased. The authors conclude that 3-PGA is a primary carboxylation product of the PCRP in GC and that the activity of the PCRP and PEP-carboxylase is metabolically regulated

Results of application of external fixation with different types of fixators

Directory of Open Access Journals (Sweden)

Grubor Predrag

2012-01-01

Full Text Available Introduction. Extra-focal or external fixation is the method of fracture fixation through the healthy part of the bone using pins or wires. Objective. The aim was to determine which external splints (Ortofix, Mitković, Charnley and Ilizarov had the best biomechanical properties in primary stabilization of spiral, transverse and commutative bone fractures. Methods. To determine the investigation methodology of biomechanical characteristics of the external fixator we used mathematical and computer simulator (software, juvidur physical model and clinical examination. Results. Values of advancing fragments in millimetres obtained by the study of mathematical and computer simulator (software: Charnley - 0.080 mm, Mitković M 20 - 0.785 mm, Ilizarov - 2.245 mm and Ortofix - 1.400 mm. In testing the juvidur model the following values were obtained: the external fixator Mitković M20 - 1.380 mm, Ortofix - 1.470 mm, Ilizarov - 2.410 mm, and Charnley - 2.510 mm. Clinical research of biomechanical characteristics of the effect of vertical force yielded the following results: Mitković M20 - 0.89 mm, Ortofix - 0.14 mm, Charnley - 0.80 mm and Ilizarov - 1.23 mm. Conclusion. When determining the total number of the stability test splints under the effect of vertical force (compression and force effect in antero-posterior, later-lateral plane of cross, spiral and comminuted long bone fractures, the best unified biomechanical stability was shown by the following external fixators: firstly, Mitković M20 (0.93mm, secondly, Charnley fixator (1.14 mm, thirdly, Ortofix (1.22 mm, and fourthly, Ilizarov (1.60 mm.

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

Directory of Open Access Journals (Sweden)

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

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%)