Nitrate Transport Research Articles

Physiological Responses of Cigar Tobacco Crop to Nitrogen Deficiency and Genome-Wide Characterization of the NtNPF Family Genes.

Tobacco prefers nitrate as a nitrogen (N) source. However, little is known about the molecular components responsible for nitrate uptake and the physiological responses of cigar tobacco to N deficiency. In this study, a total of 117 nitrate transporter 1 (NRT1) and peptide transporter (PTR) family (NPF) genes were comprehensively identified and systematically characterized in the whole tobacco genome. The NtNPF members showed significant genetic diversity within and across subfamilies but showed conservation between subfamilies. The NtNPF genes are dispersed unevenly across the chromosomes. The phylogenetic analysis revealed that eight subfamilies of NtNPF genes are tightly grouped with their orthologues in Arabidopsis. The promoter regions of the NtNPF genes had extensive cis-regulatory elements. Twelve core NtNPF genes, which were strongly induced by N limitation, were identified based on the RNA-seq data. Furthermore, N deprivation severely impaired plant growth of two cigar tobaccos, and CX26 may be more sensitive to N deficiency than CX14. Moreover, 12 hub genes respond differently to N deficiency between the two cultivars, indicating the vital roles in regulating N uptake and transport in cigar tobacco. The findings here contribute towards a better knowledge of the NtNPF genes and lay the foundation for further functional analysis of cigar tobacco.

The cassava (Manihot-esculenta Crantz)'s nitrate transporter NPF4.5, expressed in seedling roots, involved in nitrate flux and osmotic stress

AtNPF4.5/AIT2, which was predicted to be a low-affinity transporter capable for nitrate uptake, was screened by ABA receptor complex in Arabidopsis ten years ago. However, the molecular and biochemical characterizations of AtNPF4.5 in plants remained largely unclear. In this study, the function of a plasma-membrane-localized and root-specifically-expressed gene MeNPF4.5 (Manihot-esculenta NITRATE TRANSPORTER 1 PTR FAMILY4.5), an ortholog of the Arabidopsis thaliana NPF4.5, was investigated in cassava roots as a nitrate efflux transporter on low nitrate medium and an influx transporter following exposure to high concentration of external nitrates. Moreover, RNA interference (RNAi) of MeNPF4.5 reduced the nitrate efflux capacity but the overexpressing cassava seedlings increased the ability of efflux from the elongation to the mature zone of root under low nitrate treatments. Besides, MeNPF4.5-RNAi expression reduced the nitrate influx capacity but enhanced nitrate absorption in parts of overexpressing plants from the meristem, elongation to mature zone of roots under high nitrate conditions. Furthermore, MeNPF4.5-RNAi seedlings survived owing to roots that could grow normally, but the MeNPF4.5-over-expressors showed adverse growth under 7% PEG6000 stress, suggesting that MeNPF4.5 negatively regulated the osmotic stress and was involved in nitrate flux through cassava seedlings.

Multi-tracer approach to understand nitrate contamination and groundwater-surface water interactions in the Mediterranean coastal area of Guerbes-Senhadja, Algeria

Implementing sustainable groundwater resources management in coastal areas is challenging due to the negative impacts of anthropogenic stressors and various interactions between groundwater and surface water. This study focuses on nitrate contamination and transport via groundwater-surface water exchange in a Mediterranean coastal area (Guerbes-Senhadja region, Algeria) that is heavily affected by anthropogenic activities. A multi-tracer approach, integrating hydrogeochemical and isotopic tracers (δ2HH2O, δ18OH2O, 3H, δ15NNO3 and δ18ONO3), is combined with a Bayesian isotope mixing model (MixSIAR) to (i) elucidate the nitrate sources and their apportionments in water systems, and (ii) describe potential interactions between groundwater and surface water. Results from nitrate isotopic composition and the MixSIAR model show that nitrate concentrations mainly originate from sewage and manure sources. Nitrate derived from the sewage is attributed to urban and rural wastewater discharge, whereas nitrate derived from the manure is related to animal manure used to fertilise agricultural areas. High apportionments of nitrate-based atmospheric precipitation are identified in groundwater and surface water; a finding that is specific to this study. The multi-origin stresses combined with evidence of interactions between surface water and groundwater contribute to negatively impacting large parts of the study coastal area. The outcomes of this study are expected to contribute to sustainable management of coastal ecosystems by drawing more attention towards groundwater use and protection. Furthermore, this study may improve scientists' ability to predict the behavior of anthropogenically impacted coastal ecosystems and help decision-makers elsewhere to prepare suitable environmental strategies for other coastal ecosystems currently undergoing an early stage of groundwater resources deterioration.

Genome-wide identification and characterization of NPF family reveals NtNPF6.13 involving in salt stress in Nicotiana tabacum.

Proteins of the Nitrate Transporter 1/Peptide Transporter (NPF) family transport a diverse variety of substrates, such as nitrate, peptides, hormones and chloride. In this study, a systematic analysis of the tobacco (Nicotiana tabacum) NPF family was performed in the cultivated ‘K326’. In total, 143 NtNPF genes were identified and phylogenetically classified into eight subfamilies, NPF1 to NPF8, based on the classification of NPF families in other plant species. The chromosomal locations and structures of the NtNPF genes were analyzed. The expression profiles of NtNPF genes under NaCl stress were analyzed to screen the possible NPF genes involving in chloride regulation in tobacco. Most NtNPF6 genes responded to salt stress in the roots and leaves. The expression of NtNPF6.13 was significantly down-regulated after salt stress for 12h. The chloride content was reduced in the roots of ntnpf6.13 mutant. These findings support the participation of NtNPF6.13 in chloride uptake. Several other NtNPF genes that play potential roles in chloride metabolism of tobacco require further study.

Histone methyltransferases SDG33 and SDG34 regulate organ-specific nitrogen responses in tomato.

Histone posttranslational modifications shape the chromatin landscape of the plant genome and affect gene expression in response to developmental and environmental cues. To date, the role of histone modifications in regulating plant responses to environmental nutrient availability, especially in agriculturally important species, remains largely unknown. We describe the functions of two histone lysine methyltransferases, SET Domain Group 33 (SDG33) and SDG34, in mediating nitrogen (N) responses of shoots and roots in tomato. By comparing the transcriptomes of CRISPR edited tomato lines sdg33 and sdg34 with wild-type plants under N-supplied and N-starved conditions, we uncovered that SDG33 and SDG34 regulate overlapping yet distinct downstream gene targets. In response to N level changes, both SDG33 and SDG34 mediate gene regulation in an organ-specific manner: in roots, SDG33 and SDG34 regulate a gene network including Nitrate Transporter 1.1 (NRT1.1) and Small Auxin Up-regulated RNA (SAUR) genes. In agreement with this, mutations in sdg33 or sdg34 abolish the root growth response triggered by an N-supply; In shoots, SDG33 and SDG34 affect the expression of photosynthesis genes and photosynthetic parameters in response to N. Our analysis thus revealed that SDG33 and SDG34 regulate N-responsive gene expression and physiological changes in an organ-specific manner, thus presenting previously unknown candidate genes as targets for selection and engineering to improve N uptake and usage in crop plants.

Effect of topographic slope on the export of nitrate in humid catchments: a 3D model study

Abstract. Excess export of nitrate to streams affects ecosystem structure and functions and has been an environmental issue attracting worldwide attention. The dynamics of catchment-scale solute export from diffuse nitrogen sources can be explained by the changes of dominant flow paths, as solute attenuation (including the degradation of nitrate) is linked to the age composition of outflow. Previous data-driven studies suggested that catchment topographic slope has strong impacts on the age composition of streamflow and consequently on in-stream solute concentrations. However, the impacts have not been systematically assessed in terms of solute mass fluxes and solute concentration levels, particularly in humid catchments with strong seasonality in meteorological forcing. To fill this gap, we modeled the groundwater flow and nitrate transport for a small agricultural catchment in Central Germany. We used the fully coupled surface and subsurface numerical simulator HydroGeoSphere (HGS) to model groundwater and overland flow and nitrate transport. We computed the water ages using numerical tracer experiments. To represent various topographic slopes, we additionally simulated 10 synthetic catchments generated by modifying the topographic slope from the real-world scenario. Results suggest a negative correlation between the young streamflow fraction and the topographic slope. This correlation is more pronounced in flat landscapes with slopes <1:60. Flatter landscapes tend to retain more N mass in the soil (including mass degraded in soil) and export less N mass to the stream, due to reduced leaching and increased degradation. The mean in-stream nitrate concentration shows a decreasing trend in response to a decreasing topographic slope, suggesting that a large young streamflow fraction is not sufficient for high in-stream concentrations. Our results improve the understanding of nitrate export in response to topographic slope in a temperate humid climate, with important implications for the management of stream water quality.

Nitrate transport velocity data in the global unsaturated zones

Nitrate pollution in groundwater, which is an international problem, threatens human health and the environment. It could take decades for nitrate to transport in the groundwater system. When understanding the impacts of this nitrate legacy on water quality, the nitrate transport velocity (vN) in the unsaturated zone (USZ) is of great significance. Although some local USZ vN data measured or simulated are available, there has been no such a dataset at the global scale. Here, we present a Global-scale unsaturated zone Nitrate transport Velocity dataset (GNV) generated from a Nitrate Time Bomb (NTB) model using global permeability and porosity and global average annual groundwater recharge data. To evaluate GNV, a baseline dataset of USZ vN was created using locally measured data and global lithological data. The results show that 94.50% of GNV match the baseline USZ vN dataset. This dataset will largely contribute to research advancement in the nitrate legacy in the groundwater system, provide evidence for managing nitrate water pollution, and promote international and interdisciplinary collaborations.

Unravelling Mass Transport Effects in Electrochemical Nitrate Reduction on Titanium

Nitrate is a prevalent waterborne pollutant that threatens the health of humans and aquatic systems. By selectively producing ammonia, electrochemical nitrate reduction reaction (NO3RR) can directly transform nitrate pollutants into widely used commodity chemicals and fertilizers, thus balancing the nitrogen cycle while reducing energy consumption from the traditional Haber-Bosch process.Although research efforts to date have primarily focused on the development of efficient nitrate reduction catalysts, the electrolyte environment has been found to substantially influence NO3RR activity and selectivity. Specifically, the composition of the first ten nanometers of electrolyte away from the electrode surface dictates the immediate environment within which reactions take place. As has been demonstrated in the electrochemical CO2 reduction reaction, this interfacial reaction microenvironment comprised of near-surface electrolyte and electrocatalyst influences reaction activity and selectivity. In electrochemical NO3RR, where an anionic species reacts at a negatively charged electrode, the reaction rate can often be limited by the mass transport of the reactant nitrate. Additionally, mass transport phenomena define the electrolyte side of the reaction microenvironment by influencing other interfacial properties (i.e., electric potential, pH and ion concentrations). Therefore, we investigated the influence of mass transport phenomena on NO3RR activity and selectivity.In this study, we used a membrane-separated flow cell as a representative and translatable reactor and titanium foil as a common ammonia-selective NO3RR electrode. By varying the electrolyte flow rate, we controlled the mass transport phenomena in the flow cell and empirically determined the diffusion layer thickness. We found that NO3RR activity generally increased with increasing electrolyte flow rate, as predicted from the decreasing diffusion layer thickness, whereas NH3 selectivity slightly decreased, showing an activity-selectivity trade-off.To unravel the origins of the experimentally observed mass transport effects, simulations using the 1D generalized modified Poisson-Nernst-Planck (GMPNP) model were conducted to spatially resolve interfacial properties. Interfacial cation concentration and pH were the two properties that changed most significantly with electrolyte flow rate. Informed by simulation results, we controlled the bulk electrolyte composition to modify the interfacial cation concentration and pH and examine their impacts on NO3RR activity and selectivity. Nitrate removal rate decreased by half when the bulk cation concentration was lowered to 1/100 of the original bulk concentration but the product distribution was similar. Meanwhile, in phosphate buffered electrolytes with different bulk pH values, NH3 selectivity decreased as bulk pH increased, with NO3RR activity remaining largely unchanged. Therefore, we attributed the influence of mass transport on NO3RR selectivity to changes in the interfacial pH during reaction, likely as the result of the varying NO3RR activity under different flow rates. By comparing the nitrogen species product distribution in different electrolytes, we inferred that the interfacial pH increased rapidly to basic in non-buffered systems regardless of their bulk pH.In summary, we systematically investigated the underexplored effects of mass transport on NO3RR and found that it influenced the reaction activity and selectivity by influencing interfacial properties. This study underscores the importance of scrutinizing the interfacial electrolyte environment in electrocatalyst development and provides insight to optimize NH3 production by engineering the bulk electrolyte.

Nitrate transport in a fracture-skin-matrix system under non-isothermal conditions.

Subsurface leaching of agricultural runoff has been identified to pose a serious hazard to the soil-water ecosystem and human health, mostly due to the associated contamination with nitrate. Our understanding of the nature of contaminant spread in the vadose and aquifer zones has been improved from recent mechanistic models on the flow and transport of contaminants through fractured porous media. The present study aims to explore the impacts of skin formation in a fracture-matrix aquifer system onto the nitrogen species transport under non-isothermal settings using numerical modeling. A finite-difference scheme was employed to capture the nitrogen concentration profile and kinetics of transformation by solving the derived partial differential equations. The results show evidence of an additional mass transfer from fracture to skin so as to reduce the migration of nitrogen species (NO3-N and N2) at the fracture-matrix interface thereby reducing the peak concentration of N2 by nearly 1.5 times in fracture after denitrification. Although the thermal conductivity of the rock matrix has a direct impact on the temperature distribution in fracture-skin-matrix profiles, the presence of skin has a cooling effect for a high-temperature influent (45°C), which also deteriorates the propagation of organic N2 and NO3-N, within the fracture. An increase in the temperature coefficient of skin has resulted in an apparent reduction in nitrogen species migration, indicating the thermo-chemical feasibility of an intermediate skin favoring the mass transfer processes. The findings of this study can be extended toward realistic estimation of groundwater contamination risks and for the design of biological filters for in situ remediation.

Characterizing Groundwater Chemistry and Recharge in the Critical Zone of an Agricultural Claypan Watershed

AbstractSoils with low permeability horizons (e.g., claypans) are vulnerable to loss of nutrients through surface runoff along with preferential flow paths through the restrictive horizon to deeper aquifers. Partitioning between these hydrologic pathways is important to determine transport processes and develop strategies that mitigate stream contamination. Our objective was to investigate controls on groundwater chemistry and recharge pathways using natural geochemical tracers in the Goodwater Creek Experimental Watershed in Missouri, U.S. Groundwater samples were collected during 2011–2017 from 32 piezometers ranging from 0.13 to 16 m deep along with stream water and precipitation. Diagnostic tools of mixing models indicated that chemistry of perched water directly above the claypan and shallow groundwater immediately below was controlled primarily by chemical equilibrium. Five solutes behaved conservatively in most deep piezometers (>5 m), reflecting mixing of two end members and the lack of significant denitrification processes. End member mixing analysis showed that the deeper groundwater originated primarily from groundwater at similar depths, often upslope or from strata directly above, with small contributions from perched water, highlighting the importance of both horizontal and vertical preferential recharge pathways. Vertical pathways are likely dictated by soil heterogeneity throughout the critical zone and do not occur synchronously with precipitation events or simultaneously over all piezometer locations. The complex recharge pathways provide stochastic conduits for nitrate transport to deeper aquifers where legacy stores accumulate, presenting a significant challenge for water quality management in watersheds with restrictive soil horizons and spatially and temporally heterogeneous preferential flow pathways, including the Mississippi River Basin.

Lotus japonicus NLP1 and NLP4 transcription factors have different roles in the regulation of nitrate transporter family gene expression.

Root nodule symbiosis is promoted in nitrogen-deficient environments, whereas host plants cease the symbiosis if they can obtain enough nitrogen from their surrounding soil. In Lotus japonicus, recent reports indicate that two NODULE INCEPTION (NIN)-LIKE PROTEIN (NLP) transcription factors, LjNLP1 and LjNLP4, play important roles in the regulation of gene expression and nodulation in response to nitrate. To characterize the redundant and unique roles of LjNLP1 and LjNLP4 in more detail, we reanalyzed our previous transcriptome data using Ljnlp1 and Ljnlp4 mutants. Although downstream genes of LjNLP1 and LjNLP4 mostly overlapped, we found that nitrate-induced expression of NITRATE TRANSPORTER 2 (LjNRT2) family genes was specifically regulated by LjNLP1. In contrast, LjNRT1 gene family expression was regulated by both LjNLP1 and LjNLP4. Therefore, it is likely that the two NLPs play distinct roles in the regulation of nitrate transport.

Nostoc Talks Back: Temporal Patterns of Differential Gene Expression During Establishment of Anthoceros-Nostoc Symbiosis.

Endosymbiotic associations between hornworts and nitrogen-fixing cyanobacteria form when the plant is limited for combined nitrogen (N). We generated RNA-seq data to examine temporal gene expression patterns during the culturing of N-starved Anthoceros punctatus in the absence and the presence of symbiotic cyanobacterium Nostoc punctiforme. In symbiont-free A.punctatus gametophytes, N starvation caused downregulation of chlorophyll content and chlorophyll fluorescence characteristics as well as transcription of photosynthesis-related genes. This downregulation was reversed in A. punctatus cocultured with N. punctiforme, corresponding to the provision by the symbiont of N2-derived NH4+, which commenced within 5 days of coculture and reached a maximum by 14 days. We also observed transient increases in transcription of ammonium and nitrate transporters in a N. punctiforme-dependent manner as well as that of a SWEET transporter that was initially independent of N2-derived NH4+. The temporal patterns of differential gene expression indicated that N. punctiforme transmits signals that impact gene expression to A. punctatus both prior to and after its provision of fixed N. This study is the first illustrating the temporal patterns of gene expression during establishment of an endosymbiotic nitrogen-fixing association in this monophyletic evolutionary lineage of land plants. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Development of a predictive kinetic model with statistically analyzed parameters for Donnan Dialysis process

Donnan Dialysis (DD) utilizes ion exchange membranes that allow the selective transport of target ions from a feed solution to a concentrated receiver solution. The kinetics of DD involves boundary layer diffusion (BLD), diffusional membrane transport (MD), and a mixed regime where both mechanisms are active. The objective of the research was to develop an automated computational model that can predict nitrate, bicarbonate, and sulfate concentration profiles and transport mechanisms in DD processes. Experiments were conducted in a batch dialyzer in sole- and multi-component feed solutions and NaCl receiver solutions.Training of the model included numerical extraction of the BLD and MD coefficients from the experimental data; determination of the statistically significant parameters that affect the DD transport; development of correlations between these parameters and the kinetic coefficients; and mapping of the ratio between the boundary layer resistance and the membrane resistance to determine the transport mechanism.The predictive model, included the kinetic equations, i.e., the Nernst-Planck formulation, mass balances, and electro-neutrality, the correlations, and the mapping of the transport mechanism. The model was verified by the experimental data used for the model training and validated by independent datasets. Very good fits between the predicted and experimental concentration profiles were obtained, and the ability to determine the transport mechanism was demonstrated.

Patterns of long-term variations of nitrate concentration – Stream discharge relationships for a drained agricultural watershed in Mid-western USA

Nitrate Concentration–discharge (C-Q) relationshipshave been used to infer nitrate sources, storage, reactions, and transport in watersheds, and to reveal key processes that control runoff chemistry. Yet, studies on long-term nitrate C-Q relationships are limited due to scarce high frequency (e.g., daily) concentration data. In this paper, using a long-term high-frequency dataset (1976–2019) comprising stream flow and nitrate concentrations, we quantitatively analyzed the long-term variations of event-scale hysteresis patterns (quantified by hysteresis index, HI, and flushing index, FI) to infer the leaching mechanisms of nitrate in an artificially drained agricultural watershed in Mid-western U.S. Our results revealed that most events exhibited anti-clockwise behaviors (HI < 0), regardless of whether nitrate was flushed or diluted during events. This means that water with high levels of nitrate-N reaches the stream network slower than water with lower nitrate concentrations. Long-term mean FI was close to zero but had strong seasonal patterns with dilution patterns observed during Winter and Summer, and flushing patterns during late Spring and Fall. The consistently negative HI values regardless of the FI value gave a strong indication of the preponderant role of the near-drain zone that usually exhibits accelerated leaching and less accumulation of nitrate in the soil profile in these drained agricultural watersheds. Both HI and FI depicted strong but opposite seasonality because of weather patterns and agricultural activities, particularly N fertilization. Overall, our findings suggest a little evidence of the role of deep groundwater and instead a strong evidence of the role of subsurface drainage as the primary pathway for nitrate transport in drained agricultural watersheds. Therefore, artificial drainage could dampen N legacy caused by the historically intensive N fertilization in drained agricultural landscapes.

Inhibition of shoot-expressed NRT1.1 improves reutilization of apoplastic iron under iron-deficient conditions.

Iron deficiency is a major constraint for plant growth in calcareous soils. The interplay between NO3 - and Fe nutrition affects plant performance under Fe-deficient conditions. However, how NO3 - negatively regulates Fe nutrition at the molecular level in plants remains elusive. Here, we showed that the key nitrate transporter NRT1.1 in Arabidopsis plants, especially in the shoots, was markedly downregulated at post-translational levels by Fe deficiency. However, loss of NRT1.1 function alleviated Fe deficiency chlorosis, suggesting that downregulation of NRT1.1 by Fe deficiency favors plant tolerance to Fe deficiency. Further analysis showed that although disruption of NRT1.1 did not alter Fe levels in both the shoots and roots, it improved the reutilization of apoplastic Fe in shoots but not in roots. In addition, disruption of NRT1.1 prevented Fe deficiency-induced apoplastic alkalization in shoots by inhibiting apoplastic H+ depletion via NO3 - uptake. In vitro analysis showed that reduced pH facilitates release of cell wall-bound Fe. Thus, foliar spray with an acidic buffer promoted the reutilization of Fe in the leaf apoplast to enhance plant tolerance to Fe deficiency, while the opposite was true for the foliar spray with a neutral buffer. Thus, downregulation of the shoot-part function of NRT1.1 prevents apoplastic alkalization to ensure the reutilization of apoplastic Fe under Fe-deficient conditions. Our findings may provide a basis for elucidating the link between N and Fe nutrition in plants and insight to scrutinize the relevance of shoot-expressed NRT1.1 to the plant response to stress.

Grafting improves growth and nitrogen-use efficiency by enhancing NO3− uptake, photosynthesis, and gene expression of nitrate transporters and nitrogen metabolizing enzymes in watermelon under reduced nitrogen application

Grafting improves growth and nitrogen-use efficiency by enhancing NO3− uptake, photosynthesis, and gene expression of nitrate transporters and nitrogen metabolizing enzymes in watermelon under reduced nitrogen application

OsTBP2.1, a TATA-Binding Protein, Alters the Ratio of OsNRT2.3b to OsNRT2.3a and Improves Rice Grain Yield.

The OsNRT2.3a and OsNRT2.3b isoforms play important roles in the uptake and transport of nitrate during rice growth. However, it is unclear which cis-acting element controls the transcription of OsNRT2.3 into these specific isoforms. In this study, we used a yeast one-hybrid assay to obtain the TATA-box binding protein OsTBP2.1, which binds to the TATA-box of OsNRT2.3, and verified its important role through transient expression and RNA-seq. We found that the TATA-box of OsNRT2.3 mutants and binding protein OsTBP2.1 together increased the transcription ratio of OsNRT2.3b to OsNRT2.3a. The overexpression of OsTBP2.1 promoted nitrogen uptake and increased rice yield compared with the wild-type; however, the OsTBP2.1 T-DNA mutant lines exhibited the opposite trend. Detailed analyses demonstrated that the TATA-box was the key cis-regulatory element for OsNRT2.3 to be transcribed into OsNRT2.3a and OsNRT2.3b. Additionally, this key cis-regulatory element, together with the binding protein OsTBP2.1, promoted the development of rice and increased grain yield.

Capability of HYDRUS wetland module to simulate flow and nitrogen removal processes in pilot-scale treatment peatlands under frost and no-frost conditions

The HYDRUS wetland module is widely used together with the biokinetic model CWM1 to simulate reactive transport of contaminants in constructed wetlands. However, this approach has not been used previously to simulate processes in peat-based wetlands operating in cold climates and treating mining-influenced water. In this study, the goal was to clarify changes in flow, transport, and nitrogen removal processes in cold climate treatment peatlands by assessing the performance of HYDRUS-CWM1. Flow and non-reactive transport of tracer, and reactive transport of ammonium, nitrite, and nitrate, in two pilot wetlands operated under controlled conditions representing frozen (winter) and frost-free (summer) periods were simulated. Model simulation outputs were compared against data obtained from the pilot wetlands and from a full-scale treatment peatland treating mining-influenced water in an Arctic region. Initial peaks in tracer concentration were simulated satisfactorily, but transformation and transport of nitrogen species in treatment peatlands, especially under partially frozen conditions, were modeled with only limited success. Limitations of the model and the assumptions made for the simulations have been discussed to highlight the challenges in modeling of treatment peatlands.

Unraveling the transport and compressibility behaviour of copper nitrates in non-aqueous solvents at 308 K temperature and 1 atmospheric pressure

In the present studies, density (ρ), viscosity (η), conductance and ultrasonic velocity (u) of copper (I) nitrate complexes were measured by conventional methods. The data was used to evaluate the transport and compressibility properties of the prepared compounds in Dimethylsulfoxide (DMSO), Pyridine (Py) and Nitromethane (NM) and in their binary mixtures: DMSO + Py and DMSO + NM at different concentrations at 308 K and 1 atmospheric pressure. The experimentally measured data was used to evaluate parameters like Limiting ionic molar conductance (λ⁰i), solvated radii (ri), ionic mobility (μ±), transport number(t±), Ionic B values (B±), Isentropic Compressibility (κs), Limiting molal ionic isentropic compressibility (κso,ø), limiting apparent molar volume (ɸ°v), Masson's coefficient (Sv), partial molar expansibilities (ɸ°E) and Hepler's constant. Trend in the transport behaviour of complexes like conductance and viscosity was discussed in terms of solvated radii and Jones Dole equation for B- coefficients respectively. Similarly, the compressibility behaviour was discussed in terms of trend in the values of limiting molal ionic isentropic compressibility's. The results were interpreted in terms of solute–solute/solute–solvent interaction and structure making/breaking characteristics of solute in the non-aqueous solution.

Exogenous calcium promotes growth of adzuki bean (Vigna angularis Willd.) seedlings under nitrogen limitation through the regulation of nitrogen metabolism

Plants exhibit lower nitrogen use efficiency (NUE) under N-limitation conditions. Although the function of calcium (Ca) has been widely studied in plants, it remains to be explored whether regulation of nitrate uptake and reduction is needed. A hydroponics experiment on adzuki beans (Vigna angularis Willd.) was used as a test material to determine the interactions between Ca and three levels of nitrogen supply. The height of the plant, the leaf area per plant, the biomass of the plant, the morphology of the roots, the hydraulic conductivity of the roots, the level of gas exchange, and the level of N metabolism of the adzuki beans were evaluated. Furthermore, RT-qPCR was conducted to explore the expression of genes related to nitrate transporter responses to Ca under N-limitation stress conditions. The rate of accumulation of N in plant tissue increased with the application of Ca. However, plant biomass, photosynthetic parameters, and root activity peaked for Ca2+ supply under N-marginal conditions. Further investigation revealed that the activities of nitrate reductase and glutamine synthetase were relatively high. The transcription of the nitrate transporter (VaNRT1.1; VaNRT2.5) was up-regulated in the roots of the Ca-treated plants. Both N-marginal conditions and N deficiency inhibit N absorption and utilization. The favorable effects of Ca on seedling growth and N metabolism under N-marginal conditions were more significant than those under N-deficiency conditions. The supply of Ca2+ is optimal, as it increases NUE by enhancing photosynthesis, N-metabolizing enzyme activities, and NO3 uptake and transport under N-marginal conditions.