Short-term 15N uptake kinetics and nitrogen nutrition of bryophytes in a lowland rainforest, Costa Rica

2008 ◽  
Vol 35 (1) ◽  
pp. 51 ◽  
Author(s):  
Wolfgang Wanek ◽  
Katja Pörtl
Keyword(s):  
Costa Rica ◽  
Nitrogen Nutrition ◽  
Uptake Kinetics ◽  
Short Term ◽  
15N Uptake ◽  
Uptake Rates ◽  
Net Uptake ◽  
Nitrogen Concentrations ◽  
External Sources ◽  
Kinetics Of

Though bryophytes can markedly affect the hydrological and biogeochemical cycles of tropical rainforests, virtually nothing is known on their nutritional requirements. Here, short-term 15N uptake kinetics of NO3–, NH4+ and glycine were studied in nine species of bryophytes in a lowland wet tropical forest, Costa Rica. Net uptake of all three N forms obeyed to saturation (Michaelis-Menten) kinetics between 1 and 500 µmol L–1. Mean Km (Vmax) values ranged between 21 µm (6.6 µmol g–1 DW h–1, nitrate), 94 µm (43.5 µmol g–1 DW h–1, ammonium) and 126 µm (37.6 µmol g–1 DW h–1, glycine). No significant differences were evident between epiphyllous and epiphytic bryophytes. Concentrations of nitrogenous solutes of external sources ranged between 1.7 and 35.9 µm. External nitrogen concentrations and kinetic constants of the bryophyte species allowed estimation of net uptake rates in the field. The mean uptake rates were 1.8 µmol g–1 DW h–1 for nitrate, 3.6 µmol g–1 DW h–1 for ammonium, and 3.4 µmol g–1 DW h–1 for glycine, indicating that amino acids significantly contribute to bryophyte nutrition.

scholarly journals Vanadium Requirements and Uptake Kinetics in the Dinitrogen-Fixing Bacterium Azotobacter vinelandii

2008 ◽  
Vol 74 (5) ◽  
pp. 1478-1484 ◽  
Author(s):  
J. P. Bellenger ◽  
T. Wichard ◽  
A. M. L. Kraepiel
Keyword(s):  
Growth Medium ◽  
Transport System ◽  
Growth Rates ◽  
Radioactive Isotope ◽  
Azotobacter Vinelandii ◽  
Maximum Growth ◽  
Uptake Kinetics ◽  
Soil Bacterium ◽  
Short Term ◽  
Kinetics Of

ABSTRACT Vanadium is a cofactor in the alternative V-nitrogenase that is expressed by some N2-fixing bacteria when Mo is not available. We investigated the V requirements, the kinetics of V uptake, and the production of catechol compounds across a range of concentrations of vanadium in diazotrophic cultures of the soil bacterium Azotobacter vinelandii. In strain CA11.70, a mutant that expresses only the V-nitrogenase, V concentrations in the medium between 10−8 and 10−6 M sustain maximum growth rates; they are limiting below this range and toxic above. A. vinelandii excretes in its growth medium micromolar concentrations of the catechol siderophores azotochelin and protochelin, which bind the vanadate oxoanion. The production of catechols increases when V concentrations become toxic. Short-term uptake experiments with the radioactive isotope 49V show that bacteria take up the V-catechol complexes through a regulated transport system(s), which shuts down at high V concentrations. The modulation of the excretion of catechols and of the uptake of the V-catechol complexes allows A. vinelandii to precisely manage its V homeostasis over a range of V concentrations, from limiting to toxic.

scholarly journals Uptake study of ClONO<sub>2</sub> and BrONO<sub>2</sub> by water droplets

2004 ◽  
Vol 4 (2) ◽  
pp. 1311-1337
Author(s):  
G. Deiber ◽  
Ch. George ◽  
S. Le Calvé ◽  
F. Schweitzer ◽  
Ph. Mirabel
Keyword(s):  
Mass Spectrometer ◽  
Pure Water ◽  
Accommodation Coefficient ◽  
Liquid Composition ◽  
Uptake Kinetics ◽  
Uptake Coefficient ◽  
Uptake Study ◽  
Mass Accommodation Coefficient ◽  
Uptake Rates ◽  
Kinetics Of

Abstract. The uptake kinetics of gaseous ClONO2 and BrONO2 on aqueous surfaces were measured, using the droplet train technique coupled to a mass spectrometer, as a function of temperature and liquid composition (pure water and NaCl or NaBr containing solutions). The uptake kinetics are driven by the reactivity of these gases and, for both compounds, the uptake rates on pure water or on NaCl solutions (0.1 M) are comparable. The uptake coefficient γ of ClONO2 does not depend on the temperature while that of BrONO2 increases slightly when the temperature is raised from 272 to 280 K. For ClONO2 and BrONO2, the uptake rates increase on NaBr-doped droplets, enabling the estimation of the mass accommodation coefficient α. The corresponding values for α are 0.108±0.001 for ClONO2 and 0.063±0.009 for BrONO2. The reactions of ClONO2 and BrONO2 on NaCl solutions lead, respectively to the formation of Cl2 and BrCl. The uptake of ClONO2 on NaBr solutions generates BrCl as primary product, which in turn can react with NaBr to produce Br2. As expected, the only product of BrONO2 reaction on NaBr solution is Br2.

scholarly journals Uptake study of ClONO<sub>2</sub> and BrONO<sub>2</sub> by Halide containing droplets

2004 ◽  
Vol 4 (5) ◽  
pp. 1291-1299 ◽  
Author(s):  
G. Deiber ◽  
Ch. George ◽  
S. Le Calvé ◽  
F. Schweitzer ◽  
Ph. Mirabel
Keyword(s):  
Mass Spectrometer ◽  
Pure Water ◽  
Accommodation Coefficient ◽  
Liquid Composition ◽  
Uptake Kinetics ◽  
Uptake Coefficient ◽  
Uptake Study ◽  
Mass Accommodation Coefficient ◽  
Uptake Rates ◽  
Kinetics Of

Abstract. The uptake kinetics of gaseous ClONO2 and BrONO2 on aqueous surfaces were measured, as a function of temperature and liquid composition (pure water and NaCl or NaBr containing solutions) using the droplet train technique coupled to a mass spectrometer. The uptake kinetics are driven by the reactivity of these gases and, for both compounds, the uptake rates on pure water or on NaCl solutions (0.1M) are comparable. The uptake coefficient γ of ClONO2 does not depend on the temperature while that of BrONO2 increases slightly when the temperature is raised from 272 to 280K. For ClONO2 and BrONO2, the uptake rates increase on NaBr-doped droplets, enabling the estimation of the mass accommodation coefficient α. The corresponding values for α are 0.108±0.033 for ClONO2 and 0.063±0.021 for BrONO2 where the statistical errors correspond to ±2σ. The reactions of ClONO2 and BrONO2 on NaCl solutions lead respectively to the formation of Cl2 and BrCl. The uptake of ClONO2 on NaBr solutions generates BrCl as primary product, which in turn can react with NaBr to produce Br2. As expected, the only product of BrONO2 reaction on NaBr solution is Br2.

scholarly journals Iron Uptake by Toxic and Nontoxic Strains of Microcystis aeruginosa

2011 ◽  
Vol 77 (19) ◽  
pp. 7068-7071 ◽  
Author(s):  
Manabu Fujii ◽  
Andrew L. Rose ◽  
T. David Waite
Keyword(s):  
Microcystis Aeruginosa ◽  
Iron Uptake ◽  
Genetically Engineered ◽  
Uptake Kinetics ◽  
Wild Type ◽  
Short Term ◽  
Content Type ◽  
Uptake Rates ◽  
Fe Uptake

ABSTRACTIron uptake by microcystin-producing and non-microcystin-producing strains ofMicrocystis aeruginosawas investigated through short-term uptake assays. Although strain-specific differences were observed, the siderophore-independent Fe uptake kinetics were essentially similar (e.g., maximum uptake rates of 2.0 to 3.3 amol·cell−1·h−1) for the wild-type toxic strain PCC7806 and a genetically engineered mutant unable to produce microcystin.

Kinetics of Methane-Oxidizing Biofilms for Degradation of Toxic Organics

1988 ◽  
Vol 20 (11-12) ◽  
pp. 167-173 ◽  
Author(s):  
S. E. Strand ◽  
R. M. Seamons ◽  
M. D. Bjelland ◽  
H. D. Stensel
Keyword(s):  
Chlorinated Hydrocarbons ◽  
Enzymatic Oxidation ◽  
Diffusion Kinetics ◽  
Toxic Compound ◽  
Biofilm Model ◽  
Uptake Rates ◽  
Substrate Diffusion ◽  
Toxic Organics ◽  
Competitive Substrate ◽  
Kinetics Of

The kinetics of methane-oxidizing bioreactors for the degradation of toxic organics are modeled. Calculations of the fluxes of methane and toxic chlorinated hydrocarbons were made using a biofilm model. The model simulated the effects of competition by toxics and mediane on their enzymatic oxidation by the methane monooxygenase. Dual-competitive-substrate/diffusion kinetics were used to model biofilm co-metabolism, integrating equations of the following form:where S1 and S2 are the local concentrations of methane and toxic compound, respectively, and r and K are the maximum uptake rates and Monod coefficients, and x is the distance into the biofilm.

Effect of Intraduodenal Starch Infusion on Net Portal Absorption of Amino Acids in Growing steers Fed Lucerne

1994 ◽  
Vol 1994 ◽  
pp. 28-28
Author(s):  
C.J. Seal ◽  
D.S. Parker ◽  
J.C. MacRae ◽  
G.E. Lobley
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Gastrointestinal Tract ◽  
Protein Turnover ◽  
Portal Blood ◽  
Intestinal Lumen ◽  
Short Term ◽  
Net Uptake ◽  
Amino Acid Requirements ◽  
Glucose Availability

Amino acid requirements for energy metabolism and protein turnover within the gastrointestinal tract are substantial and may be met from luminal and arterial pools of amino acids. Several studies have demonstrated that the quantity of amino acids appearing in the portal blood does not balance apparent disappearance from the intestinal lumen and that changing diet or the availability of energy-yielding substrates to the gut tissues may influence the uptake of amino acids into the portal blood (Seal & Reynolds, 1993). For example, increased net absorption of amino acids was observed in animals receiving exogenous intraruminal propionate (Seal & Parker, 1991) and this was accompanied by changes in glucose utilisation by the gut tissues. In contrast, there was no apparent change in net uptake of [l-13C]-leucine into the portal vein of sheep receiving short term intraduodenal infusions of glucose (Piccioli Cappelli et al, 1993). This experiment was designed to further investigate the effects on amino acid absorption of changing glucose availability to the gut with short term (seven hours) or prolonged (three days) exposure to starch infused directly into the duodenum.

Influence of phosphate status on phosphate uptake kinetics of maize (Zea mays) and soybean (Glycine max)

1990 ◽  
Vol 124 (2) ◽  
pp. 175-182 ◽  
Author(s):  
A. Jungk ◽  
C. J. Asher ◽  
D. G. Edwards ◽  
D. Meyer
Keyword(s):  
Zea Mays ◽  
Glycine Max ◽  
Phosphate Uptake ◽  
Uptake Kinetics ◽  
Kinetics Of
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