نتایج جستجو برای: n2 fixation
تعداد نتایج: 70968 فیلتر نتایج به سال:
Dinitrogen (N2) fixation rates were measured during early spring across the different provinces of Mediterranean Sea surface waters. N2 fixation rates, measured using N2 enriched seawater, were lowest in the eastern basin and increased westward with a maximum at the Strait of Gibraltar (0.10 to 2.35 nmol N L−1 d−1, respectively). These rates were 3–7 fold higher than N2 fixation rates measured ...
Nitrogen fixation in waterlogged, soil-straw, and sandday-straw mixtures was measured with the C2H2reduction assay, the I5N-tracer technique, and the Kjeldahl method. The reduction of 6 to 15 moles C2H2 corresponded to the fixation of 1 mole N2. The theoretical ratio is 3 moles C2H2 to 1 mole N2. A ratio of 3 moles C2H2 reduced for each mole of N2 fixed was obtained when samples of sandxlay-str...
Grain legumes convert atmospheric N2 to reactive N through symbiosis with N2-fixing rhizobia. Biological N2 fixation associated with legumes and the subsequent decomposition of legume residues are the primary processes that replenish N removed by harvest in agroecosystems without the addition of fertilizer N (Galloway et al., 1995, Peoples et al., 1995). Therefore, legumes are often included in...
Biological nitrogen (N2) fixation is the primary input of new nitrogen (N) to marine systems, and is important in meeting the N demands of primary producers. In this study, we determined whether restoration of the eelgrass Zostera marina L. in a shallow coastal bay facilitated increasing rates of N2 fixation as the meadows aged. Rates of N2 fixation were measured in a system that had been devoi...
We explored N2 fixation and alkaline phosphatase activity (APA) in periphyton from a N-limited stream ecosystem by coupling measurements of these processes with nutrient diffusion substrata (NDS) experiments. We measured periphyton biomass accumulation (as ash-free dry mass [AFDM] and chlorophyll a [CHLA]), N2 fixation, and APA to evaluate the relative importance of N2 fixation as an N source t...
Specialized prokaryotes performing biological dinitrogen (N2) fixation (“diazotrophs”) provide an important source of fixed nitrogen in oligotrophic marine ecosystems such as tropical and subtropical oceans. In these waters, cyanobacterial photosynthetic diazotrophs are well known to be abundant and active, yet the role and contribution of non-cyanobacterial diazotrophs are currently unclear. T...
Much of the demand for nitrogen (N) in cereal cropping systems is met by using N fertilisers, but the cost of production is increasing and there are also environmental concerns. This has led to a growing interest in exploring other sources of N such as biological N2 fixation. Non-symbiotic N2 fixation (by free-living bacteria in soils or associated with the rhizosphere) has the potential to mee...
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 contami...
Frankia is a representative genus of nitrogen-fixing (N2-fixing) actinobacteria; however, the molecular mechanisms underlying various phenomena such as the differentiation of a N2 fixation-specific structure (vesicle) and the regulation of N2 fixation (nif) genes, have yet to be elucidated in detail. In the present study, we screened hyphal fragments of Frankia casuarinae that were mutagenized ...
Increased belowground labile C inputs under elevated [CO2] could stimulate nonsymbiotic N2 fixation, thereby enhancing growth responses of vegetation to elevated [CO2] on nutrient-poor sites. To test this hypothesis, nonsymbiotic N2 fixation rates in soils planted with 3-year-old Jeffrey pine (Pinus jeffreyi Grev. & Balf.) trees grown under 365 and 700 μL·L–1 atmospheric [CO2] were measured by ...
نمودار تعداد نتایج جستجو در هر سال
با کلیک روی نمودار نتایج را به سال انتشار فیلتر کنید