Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 14 of 14 for “"ammonium uptake"”.
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The effect of organic carbon and nitrogen additions on inorganic nitrogen uptake by phytoplankton and bacteria
… and bacterio- plankton. Strongly preferential uptake of ammonium over nitrate was observed by both the phytoplanktonic and bacterial fractions, with RPINH4 values typically between 1 and 5. The bacterial fraction ( <0.8μm) was found to be responsible for as much as 48-75% of community uptake of …
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Characteristics of Nitrogen- and Iron-Limited Growth in the Diatom Phaeodactylum tricornutum, and in Natural Phytoplankton Populations.
… New Zealand). Although the characteristics of ammonium uptake have been extensively studied in marine phytoplankton, comparatively little information exists on rates of assimilation. In this study, a robust method for measuring the rate of ammonium assimilation after a transient addition of …
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Identification and functional characterisation of a class on non-selective cation channels in Saccharomyces cerevisiae.
… Ca²⁺ and changes in pH. A screen using the toxic ammonium analogue methylammonium (MA⁺) was developed using Saccharomyces cerevisiae strains that have minimal high affinity ammonium uptake capability. An in silico screen was developed and a number of candidate genes were identified as being …
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Analysis of the ammonium assimilation pathways of the human colonic bacterium, bacteroides thetaiotaomicron
… on the nitrogen supply in the feed. Assimilated ammonium accounts for up to 70% of the microbial protein production, which satisfies up to 85% of the host protein requirements. Similar numbers for the human colon have not been determined. However, colonic bacteria are responsible for the …
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Short-term dynamics of nano- and picoplankton in the southern Benguela upwelling system
… of transporter genes for processes like ammonium uptake and nitrite oxidation were found to be good indicators of measured process rates using isotope tracers. This research has highlighted the complex structure of picoplankton and nano-picoplankton communities in a coastal setting, and …
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Does pubescence increase uptake of nutrient deposition on leaves?
… with leaf surface water holding capacity, water uptake and nitrogen absorption from wet deposition for 12 Proteaceae species from the CFR, under controlled conditions; (ii) evaluating the relationship between leaf pubescence and plant height of 39 Proteaceae species from the CFR and (iii) …
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A comparative study of nitrogen uptake and nitrification rates in sub-tropical, polar and upwelling waters
Nitrification is the oxidation of ammonium to nitrate through a two step biological process. Nitrification in the euphotic zone has, in the past, been considered negligible even though quantifying this process correctly is important when linking carbon export to nitrate uptake by phytoplankton. …
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Mixed layer nitrogen cycling in the Southern Ocean: seasonality, kinetics, and biogeochemical implications
… mixed layer – including the production of ammonium and its subsequent removal via phytoplankton uptake and nitrification (i.e., the oxidation of ammonium to nitrite and then nitrate) – remains poorly understood. Following the “new production paradigm”, phytoplankton production fueled by …
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Spatial and Temporal Variability of In-Stream Functioning within a Forested, Headwater Piedmont Watershed
… processing were observed: the release of ammonium and phosphate during the warm - but shaded - growing season; nitrate uptake during autumnal leaf-fall; and a unique spike of nitrate uptake and respiration-induced degradation of labile organic matter during a drought. Consequently, the …
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Mineral nutrition of micropropagated plants
… from the culture medium, a low rate of iron uptake in both species and low tissue phosphate concentrations. Medium pH was significantly affected by the plants and a possible link between medium pH and the relative uptake of nitrate and ammonium was investigated. The rapid initial pH changes …
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Drivers of short-term variability in phytoplankton production in an embayment of the southern Benguela upwelling system: an observational and modelling study
… net primary production (NPP), nitrate and ammonium uptake, and phytoplankton community composition were measured for ten days during the upwelling season at an anchor station in SHB. A period of active upwelling (days 1-5) was followed by one of relaxation (day 6-10), together constituting …
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An investigation of aspects of the nitrogen physiology of Helianthus annuus L
… Ashton nutrient solutions containing either 2 mM ammonium, 2 mM nitrate or 1 mM ammonium+ 1 mM nitrate as the nitrogen supply to determine the effect of these nutrients upon physiological processes within the plant. Nitrate fed plants had a larger root mass than ammonium fed plants whereas …
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Assessing Cow Creek following a riparian restoration
… communities and measurement of nutrient uptake rates following short-term nutrient additions. Characterization of benthic macroinvertebrate communities is a well-established method for monitoring stream water quality, but provides little information on ecosystem function. In contrast, …
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Characterization of ammoniumtransporters in Arabidopsis thaliana
… which include transporters specialized in the uptake of nitrogen and susceptible to a regulation that responds to nitrogen limiting or excess conditions. Although the average NH4+ concentrations of soils are generally 100 to 1000 times lower than those of NO3 – (Marschner, 1995), most plants …