Natural 15N/14N isotope composition in C3 leaves: are enzymatic isotope effects informative for predicting the 15N-abundance in key metabolites?

2011 ◽  
Vol 38 (1) ◽  
pp. 1 ◽  
Author(s):  
Guillaume Tcherkez
Keyword(s):  
Amino Acids ◽  
Nitrogen Isotopes ◽  
Isotope Composition ◽  
Isotope Effects ◽  
Stomatal Closure ◽  
Metabolic Model ◽  
Organic N ◽  
State Equations ◽  
Leaf Level ◽  
15N Abundance

Although nitrogen isotopes are viewed as important tools for understanding plant N acquisition and allocation, the current interpretation of natural 15N-abundances (δ15N values) is often impaired by substantial variability among individuals or between species. Such variability is likely to stem from the fact that 15N-abundance of assimilated N is not preserved during N metabolism and redistribution within the plant; that is, 14N/15N isotope effects associated with N metabolic reactions are certainly responsible for isotopic shifts between organic-N (amino acids) and absorbed inorganic N (nitrate). Therefore, to gain insights into the metabolic origin of 15N-abundance in plants, the present paper reviews enzymatic isotope effects and integrates them into a metabolic model at the leaf level. Using simple steady-state equations which satisfactorily predict the δ15N value of amino acids, it is shown that the sensitivity of δ15N values to both photorespiratory and N-input (reduction by nitrate reductase) rates is quite high. In other words, the variability in δ15N values observed in nature might originate from subtle changes in metabolic fluxes or environment-driven effects, such as stomatal closure that in turn changes v0, the Rubisco-catalysed oxygenation rate.

scholarly journals Nitrogen isotope effects can be used to diagnose N transformations in wastewater anammox systems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Paul M. Magyar ◽  
Damian Hausherr ◽  
Robert Niederdorfer ◽  
Nicolas Stöcklin ◽  
Jing Wei ◽  
...  
Keyword(s):  
Isotope Effect ◽  
Isotope Composition ◽  
Isotope Effects ◽  
Nitrogen Isotope ◽  
Anammox Bacteria ◽  
Ammonium Oxidation ◽  
Experimental Conditions ◽  
N Transformations ◽  
Natural Systems ◽  
Inverse Isotope Effect

AbstractAnaerobic ammonium oxidation (anammox) plays an important role in aquatic systems as a sink of bioavailable nitrogen (N), and in engineered processes by removing ammonium from wastewater. The isotope effects anammox imparts in the N isotope signatures (15N/14N) of ammonium, nitrite, and nitrate can be used to estimate its role in environmental settings, to describe physiological and ecological variations in the anammox process, and possibly to optimize anammox-based wastewater treatment. We measured the stable N-isotope composition of ammonium, nitrite, and nitrate in wastewater cultivations of anammox bacteria. We find that the N isotope enrichment factor 15ε for the reduction of nitrite to N2 is consistent across all experimental conditions (13.5‰ ± 3.7‰), suggesting it reflects the composition of the anammox bacteria community. Values of 15ε for the oxidation of nitrite to nitrate (inverse isotope effect, − 16 to − 43‰) and for the reduction of ammonium to N2 (normal isotope effect, 19–32‰) are more variable, and likely controlled by experimental conditions. We argue that the variations in the isotope effects can be tied to the metabolism and physiology of anammox bacteria, and that the broad range of isotope effects observed for anammox introduces complications for analyzing N-isotope mass balances in natural systems.

scholarly journals Low and contrasting impacts of vegetation CO<sub>2</sub> fertilization on terrestrial runoff over the past three decades: Accounting for above- and below-ground vegetation-CO<sub>2</sub> effects

2020 ◽  
Author(s):  
Yuting Yang ◽  
Tim R. McVicar ◽  
Dawen Yang ◽  
Yongqiang Zhang ◽  
Shilong Piao ◽  
...  
Keyword(s):  
Atmospheric Carbon Dioxide ◽  
Stomatal Closure ◽  
Carbon Dioxide Concentration ◽  
Ground Vegetation ◽  
Positive Trend ◽  
Terrestrial Runoff ◽  
The Past ◽  
Leaf Level ◽  
Below Ground ◽  
Vegetation Water

Abstract. Elevation in atmospheric carbon dioxide concentration (eCO2) affects vegetation water use, with consequent impacts on terrestrial runoff (Q). However, the sign and magnitude of the eCO2 effect on Q is still contentious. This is partly due to the poor understanding of the opposing eCO2-induced water effects at different scales, being water-saving caused by partial stomatal closure at the leaf-level contrasting with increased water-consumption due to increase foliage cover at the canopy level, leading to highly debated findings among existing studies. None of the existing studies implicitly account for eCO2-induced changes to below-ground vegetation functioning. Here we develop an analytical eco-hydrological framework that includes the effects of eCO2 on plant leaf, canopy density, and rooting characteristics to attribute changes in Q and detect the eCO2 signal on Q over the past three decades. Globally, we detect a very small decrease of Q induced by eCO2 during 1982–2010 (−1.69 %). When assessed locally, along the resource availability (α) gradient, a positive trend (p 

scholarly journals The attempt to explain the various reaktions of rape and corn plants on the nitrogen usee in the ammonium or nitrate forms

2013 ◽  
Vol 46 (1) ◽  
pp. 39-49
Author(s):  
Zofia Uziak ◽  
Edward Borowski ◽  
Zbyszek Blamowski
Keyword(s):  
Amino Acids ◽  
Biomass Yield ◽  
Organic N ◽  
Lower Content ◽  
Ammonium Ions ◽  
Total N ◽  
Similar Content ◽  
Free Ammonium ◽  
Corn Plants ◽  
N Fractions

The reaction of the rape and corn plants on the nitrogen applied in the form NO<sub>3</sub><sup>-</sup> or NH<sub>4</sub><sup>+</sup> was studied under the controlled conditions. The ammonium ions with rape markedly lowered the growth rate, the intensity of photosynthesis and biomass yield, with relation to the plants fertilized with nitrates. With corn the effect of both N-forms was similar and positive. The biomass of the rape using NH<sub>4</sub><sup>+</sup>, with relation to the plants fertilized with NO<sub>3</sub><sup>-</sup> showed lower content of total N, and protein N, as well as markedly higher content of amino-acids of primary protein synthesis and their amides and free ammonium ions. Yet, the corn utilizing N-NH<sub>4</sub><sup>+</sup> showed, as compared with the plants fertilized with NO<sub>3</sub><sup>-</sup>, higher content of all studied organic N fractions. with similar content of free ammonium ions. This paper presents the thesis that the cause of the growth inhibition of rape fertilized with ammonium is low, as compared with corn, assimilation of NH<sub>4</sub><sup>+</sup> ions drawn in the roots of this plant.

scholarly journals Anion channel SLAH3 is a regulatory target of chitin receptor-associated kinase PBL27 in microbial stomatal closure

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Yi Liu ◽  
Tobias Maierhofer ◽  
Katarzyna Rybak ◽  
Jan Sklenar ◽  
Andy Breakspear ◽  
...  
Keyword(s):  
Stomatal Closure ◽  
Anion Channel ◽  
Anion Channels ◽  
Slow Type ◽  
Leaf Level ◽  
Short Signal ◽  
Molecular Patterns ◽  
Fungal Immunity ◽  
Anti Fungal ◽  
Full Activation

In plants, antimicrobial immune responses involve the cellular release of anions and are responsible for the closure of stomatal pores. Detection of microbe-associated molecular patterns (MAMPs) by pattern recognition receptors (PRRs) induces currents mediated via slow-type (S-type) anion channels by a yet not understood mechanism. Here, we show that stomatal closure to fungal chitin is conferred by the major PRRs for chitin recognition, LYK5 and CERK1, the receptor-like cytoplasmic kinase PBL27, and the SLAH3 anion channel. PBL27 has the capacity to phosphorylate SLAH3, of which S127 and S189 are required to activate SLAH3. Full activation of the channel entails CERK1, depending on PBL27. Importantly, both S127 and S189 residues of SLAH3 are required for chitin-induced stomatal closure and anti-fungal immunity at the whole leaf level. Our results demonstrate a short signal transduction module from MAMP recognition to anion channel activation, and independent of ABA-induced SLAH3 activation.

scholarly journals Seasonal variations in nitrate isotope composition of three rivers draining into the North Sea

2010 ◽  
Vol 7 (4) ◽  
pp. 6051-6088 ◽  
Author(s):  
A. Deek ◽  
K. Emeis ◽  
U. Struck
Keyword(s):  
Isotopic Composition ◽  
North Sea ◽  
Isotope Composition ◽  
Atmospheric Oxygen ◽  
Isotope Effects ◽  
Nitrate Sources ◽  
Particulate Nitrogen ◽  
Soil Nitrification ◽  
Mean Values ◽  
Δ 15N

Abstract. Nitrate loading of coastal ecosystems by rivers that drain industrialised catchments continues to be a problem in the South Eastern North Sea, in spite of significant mitigation efforts over the last 2 decades. To identify nitrate sources, sinks, and turnover in three German rivers that discharge into the German Bight, we determined δ 15N-NO3- and δ18O- NO3- in nitrate and δ 15N of particulate nitrogen for the period 2006–2009 (biweekly samples). The nitrate loads of Rhine, Weser and Ems varied seasonally in magnitude and δ 15N-NO3- (6.5–21‰), whereas the δ 18O-NO3- (-0.3–5.9‰) and δ 15N-PN (4–14‰) were less variable. Overall temporal patterns in nitrate mass fluxes and isotopic composition suggest that a combination of nitrate delivery from nitrification of soil ammonia in the catchment and assimilation of nitrate in the rivers control the isotopic composition of nitrate. Nitrification in soils as a source is indicated by low δ 18O-NO3- in winter, which traces the δ 18O of river water. Mean values of δ 18O-H2O were between –9.4‰ and –7.3‰; combined in a ratio of 2:1 with the atmospheric oxygen δ 18O of 23.5‰ agrees with the found δ 18O of nitrate in the rivers. Parallel variations of δ 15N-NO3- and δ 18O-NO3- within each individual river are caused by isotope effects associated with nitrate assimilation in the water column, the extent of which is determined by residence time in the river. Assimilation is furthermore to some extent mirrored both by the δ 15N of nitrate and particulate N. Although δ 15-NO3- observed in Rhine, Weser and Ems are reflected in high average δ 15N-PN (between 6‰ and 9‰, both are uncorrelated in the time series due to lateral and temporal mixing of PN. That a larger enrichment was consistently seen in δ 15N-NO3- relative to δ 18O-NO3- is attributed to constant additional diffuse nitrate inputs deriving from soil nitrification in the catchment area. A statistically significant inverse correlation exists between increasing δ 15N-NO3- values and decreasing NO3- concentrations. This inverse relationship – observed in each seasonal cycle – together with a robust relationship between human dominated land use and δ 15N-NO3- values demonstrates a strong influence of human activities and riverine nitrate consumption efficiency on the isotopic composition of riverine nitrate.

Arabidopsis and Lobelia anceps access small peptides as a nitrogen source for growth

2011 ◽  
Vol 38 (10) ◽  
pp. 788 ◽  
Author(s):  
Fiona M. Soper ◽  
Chanyarat Paungfoo-Lonhienne ◽  
Richard Brackin ◽  
Doris Rentsch ◽  
Susanne Schmidt ◽  
...  
Keyword(s):  
Amino Acids ◽  
Nitrogen Source ◽  
Biomass Accumulation ◽  
Organic N ◽  
Amino Acid Residues ◽  
Growth Responses ◽  
Small Peptides ◽  
Inorganic N ◽  
Metabolic Products ◽  
Species Specific

While importance of amino acids as a nitrogen source for plants is increasingly recognised, other organic N sources including small peptides have received less attention. We assessed the capacity of functionally different species, annual and nonmycorrhizal Arabidopsis thaliana (L.) Heynh. (Brassicaceae) and perennial Lobelia anceps L.f. (Campanulaceae), to acquire, metabolise and use small peptides as a N source independent of symbionts. Plants were grown axenically on media supplemented with small peptides (2–4 amino acids), amino acids or inorganic N. In A. thaliana, peptides of up to four amino acid residues sustained growth and supported up to 74% of the maximum biomass accumulation achieved with inorganic N. Peptides also supported growth of L. anceps, but to a lesser extent. Using metabolite analysis, a proportion of the peptides supplied in the medium were detected intact in root and shoot tissue together with their metabolic products. Nitrogen source preferences, growth responses and shoot–root biomass allocation were species-specific and suggest caution in the use of Arabidopsis as the sole plant model. In particular, glycine peptides of increasing length induced effects ranging from complete inhibition to marked stimulation of root growth. This study contributes to emerging evidence that plants can acquire and metabolise organic N beyond amino acids.

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