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Modern crops exhibit diverse sensitivities to ammonium as the primary nitrogen source, influenced by environmental factors such as external pH and nutrient availability. Despite its significance, there is currently no systematic classification of plant species based on their ammonium sensitivity. We conducted a meta-analysis of 50 plant species and present a new classification method based on the comparison of fresh biomass obtained under ammonium and nitrate nutrition. The classification uses the natural logarithm of the biomass ratio as the size effect indicator of ammonium sensitivity. This numerical parameter is associated with critical factors for nitrogen demand and form preference, such as Ellenberg indicators and the repertoire of nitrogen transporters for ammonium and nitrate uptake. Finally, a comparative analysis of the developmental and metabolic responses, including hormonal balance, is conducted in two species with divergent ammonium sensitivity values in the classification. Results indicate that nitrate has a key role in counteracting ammonium toxicity in species with a higher abundance of genes encoding NRT2-type proteins and fewer of those encoding the AMT2-type proteins. Additionally, the study demonstrates the reliability of the phytohormone balance and methylglyoxal content as indicators for anticipating ammonium toxicity. [ABSTRACT FROM AUTHOR]

Nitrate, the form of nitrogen often associated with kelp growth, is typically low in summer during periods of high macroalgal growth. More ephemeral, regenerated forms of nitrogen, such as ammonium and urea, are much less studied as sources of nitrogen for kelps, despite the relatively high concentrations of regenerated nitrogen found in the Southern California Bight, where kelps are common. To assess how nitrogen uptake by kelps varies by species and nitrogen form in southern California, USA, we measured uptake rates of nitrate, ammonium, and urea by Macrocystis pyrifera and Eisenia arborea individuals from four regions characterized by differences in nitrogen availability—Orange County, San Pedro, eastern Santa Catalina Island, and western Santa Catalina Island—during the summers of 2021 and 2022. Seawater samples collected at each location showed that overall nitrogen availability was low, but ammonium and urea were often more abundant than nitrate. We also quantified the internal %nitrogen of each kelp blade collected, which was positively associated with ambient environmental nitrogen concentrations at the time of collection. We observed that both kelp species readily took up nitrate, ammonium, and urea, with M. pyrifera taking up nitrate and ammonium more efficiently than E. arborea. Urea uptake efficiency for both species increased as internal percent nitrogen decreased. Our results indicate that lesser‐studied, more ephemeral forms of nitrogen can readily be taken up by these kelps, with possible upregulation of urea uptake as nitrogen availability declines. [ABSTRACT FROM AUTHOR]

Nitrogen and brassinosteroids (BRs) play a vital role in modulating the growth, development, and yield of rice. However, the influences of BRs on nitrogen assimilation and metabolism in rice are not fully understood. In this study, we analyzed the impact of BRs on nitrogen utilization in rice using the indica variety 'Zhongjiazao 17' and the japonica variety 'Nipponbare' in hydroponic conditions. The results showed that BR treatment could efficiently elevate nitrate and ammonium nitrogen accumulation in both shoots and roots. Furthermore, some genes involved in the uptake of nitrate and ammonium in roots were stimulated by BRs, though we noted subtle variances between the two rice cultivars. Moreover, BRs augmented the activity of nitrate reductase (NR) and glutamine synthetase (GS) in roots, along with NR in shoots. Interestingly, BRs also spiked the total free amino acid content in both the shoots and roots. Gene expression analysis uncovered a robust induction by BRs of NR genes and GS-related genes in the roots of both 'Nipponbare' and 'Zhongjiazao 17'. Collectively, our data suggest that BRs significantly enhance the accumulation of both nitrate and ammonium in rice and trigger a series of reactions related to nitrogen utilization. [ABSTRACT FROM AUTHOR]

Ammonium and polyamines are essential nitrogen metabolites in all living organisms. Crosstalk between ammonium and polyamines through their metabolic pathways has been demonstrated in plants and animals, while no research has been directed to explore this relationship in algae or to investigate the underlying molecular mechanisms. Previous research demonstrated that high concentrations of ammonium and putrescine were among the active substances in bacteria-derived algicide targeting dinoflagellates, suggesting that the biochemical inter-connection and/or interaction of these nitrogen compounds play an essential role in controlling these ecologically important algal species. In this research, putrescine, ammonium, or a combination of putrescine and ammonium was added to cultures of three dinoflagellate species to explore their effects. The results demonstrated the dose-dependent and species-specific synergistic effects of putrescine and ammonium on these species. To further explore the molecular mechanisms behind the synergistic effects, transcriptome analysis was conducted on dinoflagellate Karlodinium veneficum treated with putrescine or ammonium vs. a combination of putrescine and ammonium. The results suggested that the synergistic effects of putrescine and ammonium disrupted polyamine homeostasis and reduced ammonium tolerance, which may have contributed to the cell death of K. veneficum. There was also transcriptomic evidence of damage to chloroplasts and impaired photosynthesis of K. veneficum. This research illustrates the molecular mechanisms underlying the synergistic effects of the major nitrogen metabolites, ammonium and putrescine, in dinoflagellates and provides direction for future studies on polyamine biology in algal species. [ABSTRACT FROM AUTHOR]

It is generally accepted that hydrogen is generated by ferrous iron oxidation and/or water radiolysis but no attempt has been done so far to explain the origin of the nitrogen that is associated to 'hydrogen systems' such as those located in Brazil and Oman and New Caledonian ophiolites. We carried out 25–300 °C geochemical equilibrium calculations on model water and water-mineral systems including ammonium (NH 4 +) to see if this ion could be a 'precursor' in the generation of hydrogen and/or nitrogen. The considered minerals of the water-mineral systems were the magnetite-hematite or fayalite-magnetite-quartz redox-buffering assemblages. The water systems including NH 4 + only or NH 4 + and ferrous iron co-generate hydrogen and nitrogen through the ammonium decomposition reaction: NH 4 + = 1.5 H 2 + 0.5 N 2 + H+ In the water-mineral systems, hydrogen is generated by the magnetite and fayalite ferrous iron oxidation while nitrogen is generated independently by the hematite and magnetite ferric iron reduction by NH 4 +: 3 Fe3+ + NH 4 + = 0.5 N 2 + 3 Fe2+ + 4 H+ With magnetite-hematite, the produced gas is mainly composed of nitrogen. At low temperature with fayalite-magnetite-quartz, the produced gas is mainly composed of hydrogen; approaching 300 °C, and with a sufficient initial ammonium stock, a significant amount of nitrogen is produced to form a mixed gas. If we consider low (magnetite-hematite) or high (fayalite-magnetite-quartz) reducing conditions occurring respectively within the central or peripheral zones of the hydrogen systems, NH 4 + passing through and reacting with these two kinds of redox environments could explain why the central zones release mainly hydrogen (with some amounts of nitrogen) and why mainly nitrogen is emitted at the peripheries. • Modeling of ammonium oxidation in redox-unbuffered and -buffered aqueous systems. • Hydrogen and nitrogen co-generation through ammonium decomposition. • Nitrogen generation through ferric iron reduction by ammonium. • Hydrogen to nitrogen gas ratios as function of redox conditions. • Explanation of hydrogen and nitrogen association within natural hydrogen seepages. [ABSTRACT FROM AUTHOR]

Plant growth and development depend on sufficient nutrient availability in soils. Agricultural soils are generally nitrogen (N) deficient, and thus soils need to be supplemented with fertilizers. Ammonium (NH4+) is a major inorganic N source. However, at high concentrations, NH4+ becomes a stressor that inhibits plant growth. The cause of NH4+ stress or toxicity is multifactorial, but the interaction of NH4+ with other nutrients is among the main determinants of plants' sensitivity towards high NH4+ supply. In addition, NH4+ uptake and assimilation provoke the acidification of the cell external medium (apoplast/rhizosphere), which has a clear impact on nutrient availability. This review summarizes current knowledge, at both the physiological and the molecular level, of the interaction of NH4+ nutrition with essential mineral elements that are absorbed as cations, both macronutrients (K+, Ca2+, Mg2+) and micronutrients (Fe2+/3+, Mn2+, Cu+/2+, Zn2+, Ni2+). We hypothesize that considering these nutritional interactions, and soil pH, when formulating fertilizers may be key in order to boost the use of NH4+-based fertilizers, which have less environmental impact compared with nitrate-based ones. In addition, we are convinced that better understanding of these interactions will help to identify novel targets with the potential to improve crop productivity. [ABSTRACT FROM AUTHOR]

Background: Land plants exhibit a haplodiplontic life cycle, whereby multicellular bodies develop in both the haploid and diploid generations. The early-diverging land plants, known as bryophytes, have a haploid-dominant life cycle, in which a short-lived multicellular body in the diploid generation, known as the sporophyte, develops on the maternal haploid gametophyte tissues. The moss Physcomitrium (Physcomitrella) patens has become one of the most powerful model systems in evolutionary plant developmental studies. To induce diploid sporophytes of P. patens, several protocols are implemented. One of the conventional approaches is to grow approximately one-month-old gametophores for another month on Jiffy-7 pellets made from the peat moss that is difficult to fully sterilize. A more efficient method to obtain all tissues throughout the life cycle should accelerate studies of P. patens. Results: Here, we investigated the effect of nitrogen conditions on the growth and development of P. patens. We provide an improved protocol for the sporophyte induction of P. patens using a BCD-based solid culture medium without Jiffy-7 pellets, based on the finding that the formation of gametangia and subsequent sporophytes is promoted by nitrogen-free growth conditions. The protocol consists of two steps; first, culture the protonemata and gametophores on nitrogen-rich medium under continuous light at 25 °C, and then transfer the gametophores onto nitrogen-free medium under short-day and at 15 °C for sporophyte induction. The protocol enables to shorten the induction period and reduce the culture space. Conclusions: Our more efficient and shortened protocol for inducing the formation of sporophytes will contribute to future studies into the fertilization or the diploid sporophyte generation of P. patens. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of feeding silage to pigs on nitrogen (N) utilization and ammonia (NH3) volatilization. In total, 128 Yorkshire × Hampshire (30–110 kg) pigs were fed commercial feed (Control) or commercial feed mixed with dried, milled silage in pelleted form (Pellet-S), fresh, chopped silage (Silage-Ch) or intensively treated silage (Silage-Pr). Silage replaced 20% of the crude protein (g/kg). Diet affected daily N excretion, which was higher for pigs fed Silage-Ch and Silage-Pr than for pigs in the Pellet-S and Control treatments. Ammonium nitrogen (NH4-N) content in the manure and NH3 volatilization from fresh manure were higher for Control pigs than for pigs in the other treatments. Overall, these results show that pre-treatment of silage influences N utilization and excretion. Furthermore, the results indicate that feeding silage to pigs can reduce NH3 volatilization from fresh manure. [ABSTRACT FROM AUTHOR]

The preferable N source for tropical grasses and its effects on the nutritional status are still matters of priority investigation. This study aimed to explore the effects of N sources and N deprivation on growth and uptake of elements in a newly-released ruzigrass cultivar, BRS Integra. Plants were grown under controlled conditions in vermiculite and were supplied with nutrient solution containing either NH4+, NH4++NO3-, NO3- or no N added in solution making. Plant biomass, chlorophyll content, transpiration, N status, and levels of selected elements were evaluated. NH4+ improved biomass production and aboveground N contents. Other elements exhibited high (N, K and Na), medium (Mn), low (Ca, Cd, Cr, Cu, Mg, Ni and Zn) or non-detected (Al and Fe) translocation. Cd was included in the study because of its hazardous concentrations in agricultural soils in Brazil and its influence on N uptake and translocation in the genus Urochloa. All N sources increased the uptake of whole plant Cu and K and Al, and root Fe and Mg. Other favorable relations prevailed in the roots, specifically of NO3- on Ca and Ni, NH4+ and NH4++NO3- on Cr, and NH4+ on Cd. Removal of N supply caused increases on Mn and Na aboveground and Zn in roots. Overall, the more evident N source-induced uptakes were, in order of decrease, of NO3- on Ca, NH4++NO3- on Ni, and NH4+ on Cr, Cu and Mn. It is concluded that NH4+ is more efficient for fertilizing ruzigrass by improving growth and N uptake compared to NH4++NO3- or NO3-. In addition, the diverse effects of varying N sources on the uptake of 12 elements indicate such interactions should be taken into account to further improve fertilizer formulations. [ABSTRACT FROM AUTHOR]

[Objective] The study aimed to investigate the effects of nitrogen application rate on soil inorganic nitrogen content, cotton yield, nutrient absorption and utilization in cotton field in Southern Xinjiang. [Method] Taken Xinluzao 66 as the material, five nitrogen application treatments ( 0, 150, 225, 300, 450 kg N/hm2, respectively expressed as NO, N150, N225, N300, N450) were set, and field tests in Shaya county, Aksu Prefecture, Xinjiang in 2021 were conducted. The content of nitrate nitrogen, ammonium nitrogen, dry matter quality, nitrogen accumulation and yield of cotton in 0 - 60 cm soil layer were measured. [Result] ( i) The content of nitrate nitrogen and anunonium nitrogen in soil of each treatment decreased with soil deepening. With the increase of nitrogen application level, the contents of nitrate nitrogen and ammonium nitrogen in 0 - 60 cm soil layers were significantly increased. The nitrate nitrogen in 0 - 20 cm soil layers at bud stage was significantly different ( P < 0. 05, the same as below), and the fertilization treatment increased I. 54 - 2. 47 times compared with NO; There was no significant difference in ammonium nitrogen content between N225 and N300 treatments in 0 - 20 cm soil layer at seedling stage ( P >0. 05, the same as below), and N450 treatment significantly increased 57% -140% compared with other treatments. The anunonium nitrogen content was abundant at the seedling stage, but it was obviously lacking in the peak bell stage. The nitrate nitrogen content was lacking in the seedling stage and abundant at the peak bell stage. (ii) The dry matter quality, nitrogen content, lint yield, nitrogen fertilizer utilization rate and agronomic utilization rate of cotton all increased first and then decreased with the increase of fertilization amount, and reached the maximum under N300 treatment. The maximum dry matter accumulation of cotton roots, stems, leaves, buds, flowers and bolls under N300 treatment were 4. 16, 20. 33, 7. 47 and 10. 84 g/ plant, respectively; The nitrogen accumulation amount of cotton at N300 treatment was 304. 00 kg/hm2, and the nitrogen accumulation amount of the boll at N300 treatment was 32.17%, which increased by 3. 95% - 5. 27% compared to other treatments; The lint yield at N300 treatment reached 6574. 8 kg/hm2, which increased by 21. 23% -67. 54% compared to other treatments, the nitrogen fertilizer utilization rate increased by 6. 85 % - 20. 88 %, and the agronomic utilization rate 2. 86% -6. 66%. [ Conclusion] The best amount of nitrogen fertilizer is 300 kg/hm² . When the nitrogen application rate exceeds 300 kg/ hm², the dry matter quality and nitrogen accumulation of cotton decrease, the soil nitrate nitrogen ammonium nitrogen content is higher, the nitrogen use efficiency decreases, and the yield increase effect is not obvious. [ABSTRACT FROM AUTHOR]

The extensive agricultural feedlot operations in the Neuse River Watershed (NRW) in North Carolina result in high nutrient loading, particularly of ammonium (NH4+). In September 2018, Hurricane Florence devastated large portions of the NRW, creating a unique opportunity to study the impact of such hydrological events on the biogeochemistry of riverine and riparian sediments. The high NH4+ concentrations, naturally acidic conditions, and elevated levels of ferric iron [Fe(III)] in Neuse River sediments and soils provide an ideal environment for Acidimicrobium sp. A6 (referred to hereon as A6), a bacterium capable of conducting the Feammox process in which NH4+ is oxidized while iron is reduced. A6 was observed in all sediment samples obtained from the Neuse River, and it is therefore predicted that this process may be an important mechanism for NH4+ removal in this river system. Incubations of NRW samples indicate that the NH4+ oxidation potential via the Feammox process in the NRW is comparable with aerobic NH4+ oxidation by heterotrophic microorganisms. Given the high demand for Fe(III) by the Feammox process, it has been unclear how such a process may occur in sedimentary environments where ferric iron [Fe(III)] might be depleted. The results presented here show that a major hydrologic storm event can result in an increase in Fe(III) and in an increase in the abundance of Fe-reducing bacteria, including Acidimicrobium sp. A6. These findings indicate that major hydrologic storm events may, via the delivery of Fe(III), be capable of enhancing Feammox activity in riverine sediments that favor the Feammox process. [ABSTRACT FROM AUTHOR]

We evaluated the effects of isoforms of ammonium transporters (AMT) and amino acid transporters (AAT) on three rice varieties cultivated with different levels of ammonium (NH4+) and its biochemical responses. The rice varieties used were IAC-47 (improved), Manteiga and Piauí (landraces), cultivated under 0.2 mM NH4+ (low N, LN), 1 mM NH4+ (sufficient N, SN) or resupply with 1 mM of NH4+ after three days without nitrogen (N). When cultivated with LN, the Piauí variety presented a higher expression of AAT (Lysine-Histidine Transporter 4 (OsLHT4) and GABA Transporters (OsGAT1)) in roots, while Manteiga and IAC-47 presented higher expression of the Amino Acid Permease 1 (OsAAP1) and Ammonium Transporter 1.1 (OsAMT1.1), respectively. Additionally, Piauí had the higher expression of glutamine synthetase (OsGS1.1 and OsGS1.3) in shoots cultivated with LN or resupply. The Piauí variety displayed higher glutamine synthetase activity and amino acid content under resupply. Manteiga and Piauí presented a lower reduction in fresh weight of leaves and sheaths under LN compared to IAC-47. The results suggest that the improved variety IAC-47 is more efficient when cultivated with SN, while, under LN or resupply, the landrace varieties were superior. Overall, the molecular responses were different among the varieties, which may affected their nitrogen metabolism. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is an essential macronutrient for plants and profoundly affects crop yields and qualities. Ammonium (NH4+) and nitrate (NO3−) are major inorganic N forms absorbed by plants from the surrounding environments. Intriguingly, NH4+ is usually toxic to plants when it serves as the sole or dominant N source. It is thus important for plants to coordinate the utilization of NH4+ and the alleviation of NH4+ toxicity. To fully decipher the molecular mechanisms underlying how plants minimize NH4+ toxicity may broadly benefit agricultural practice. In the current minireview, we attempt to discuss recent discoveries in the strategies for mitigating NH4+ toxicity in plants, which may provide potential solutions for improving the nitrogen use efficiency (NUE) and stress adaptions in crops. [ABSTRACT FROM AUTHOR]

The ammonium transporter (AMT) family gene is an important transporter involved in ammonium uptake and transfer in plants and is mainly engaged in the uptake and transport of ammonium from the environment by roots and the reabsorption of ammonium in the aboveground parts. In this study, the expression pattern, functional identification, and genetic transformation of the PtrAMT1;6 gene, a member of the ammonium transporter protein family in P. trichocarpa, were investigated as follows: (1) Fluorescence quantitative PCR demonstrated that the PtrAMT1;6 gene was preferentially expressed in the leaves, with both dark-induced and light-inhibited expression patterns. (2) A functional restoration assay using the yeast ammonium transporter protein mutant strain indicated that the PtrAMT1;6 gene restored the ability of the mutant to transport ammonium with high affinity. (3) Arabidopsis was transformed with pCAMBIA-PtrAMT1;6P, and the transformed lines were stained with GUS, which showed that the rootstock junction, cotyledon petioles, and the leaf veins and pulp near the petioles of the transformed plants could be stained blue, indicating that the promoter of the PtrAMT1;6 gene had promoter activity. (4) The overexpression of the PtrAMT1;6 gene caused an imbalance in carbon and nitrogen metabolism and reduced nitrogen assimilation ability in '84K' poplar and ultimately reduced biomass. The above results suggest that PtrAMT1;6 may be involved in ammonia recycling during nitrogen metabolism in aboveground parts, and overexpression of PtrAMT1;6 may affect the process of carbon and nitrogen metabolism, as well as nitrogen assimilation in plants, resulting in stunted growth of overexpression plants. [ABSTRACT FROM AUTHOR]

Lowman, H.E.; Hirsch, M.E.; Brzezinski, M.A., and Melack, J.M., 2023. Examining the potential of sandy marine sediments surrounding giant kelp forests to provide recycled nutrients for growth. Journal of Coastal Research, 39(3), 442–454. Charlotte (North Carolina), ISSN 0749-0208. Permeable marine sediments are biogeochemically active and may contribute dissolved nutrients to support primary production in coastal regions. This study examined the potential of permeable marine sediments near giant kelp forests in the Santa Barbara Channel, California as a source of ammonium (NH4+) to the overlying water column to support the observed growth of kelp during summer months when nitrate availability is low. Several nearshore sites located in coastal California in <20 m water depth were sampled for porewater nutrient concentrations, flushing rates, and nutrient fluxes in addition to diel fluctuations in nutrient concentrations of the overlying water column. Time-series analyses of porewater temperatures indicate that porewater flushed to a depth of 15 cm approximately every two hours, and mean NH4+ concentrations of porewater at these depths was 40 µM. The results of flow-through bioreactor incubations indicate that the top 2 cm of sediment are a net source of dissolved nitrogen to the overlying water column and are capable of supplying from 0.05 to 0.90 mmol NH4+ m–2 day–1. Diel water sampling demonstrates that kelp forests may be exposed to NH4+ concentrations greater than 1 µM for multiple hours (four–eight) over a day. These measured reservoirs and exchange rates of NH4+ suggest sandy marine sediments provide a significant source of nitrogen to the water column and may help meet the nitrogen demand by giant kelp during summer in the Santa Barbara Channel. [ABSTRACT FROM AUTHOR]

Excess ammonium imposes toxicity and stress response in cyanobacteria. How cyanobacteria acclimate to NH4+ stress is so far poorly understood. Here, Synechocystis sp. PCC6803 S2P homolog Slr1821 was identified as the essential regulator through physiological characterization and transcriptomic analysis of its knockout mutant. The proper expression of 60% and 67% of the NH4+ activated and repressed genes, respectively, were actually Slr1821-dependent since they were abolished or reversed in ∆slr1821. Synechocystis 6803 suppressed nitrogen uptake and assimilation, ammonium integration and mobilization of other nitrogen sources upon NH4+ stress. Opposite regulation on genes for assimilation of nitrogen and carbon, such as repression of nitrogen regulatory protein PII, PII interactive protein PirC and activation of carbon acquisition regulator RcbR, demonstrated that Synechocystis 6803 coordinated regulation to maintain carbon/nitrogen homeostasis under increasing nitrogen, while functional Slr1821 was indispensable for most of this coordinated regulation. Additionally, slr1821 knockout disrupted the proper response of regulators and transporters in the ammonium-specific stimulon, and resulted in defective photosynthesis as well as compromised translational and transcriptional machinery. These results provide new insight into the coordinated regulation of nutritional fluctuation and the functional characterization of S2Ps. They also provide new targets for bioengineering cyanobacteria in bioremediation and improving ammonium tolerance in crop plants. [ABSTRACT FROM AUTHOR]

Ammonium uptake into wheat roots relies primarily on two AMmonium Transporters of subfamily one, while the wheat genome comprises 4 to 6 AMT2 type transporters. Plant AMT2s generally show functions in root‐to‐shoot translocation or pathogenic and symbiotic plant–microorganism interactions. We addressed the activity of TaAMT2s in ammonium transport. Nitrogen‐dependent expression implicated a physiological function in ammonium uptake for TaAMT2;1 and in ammonium distribution for TaAMT2;2‐6. [ABSTRACT FROM AUTHOR]

Soil ammonium toxicity can decrease plant growth, and many crop species have low resistance to ammonium, including canola, an economically important crop. Different genotypes may differ in their resistance to ammonium toxicity, and therefore determining if there are genotypes that exhibit variation in their ability to tolerate soil ammonium is a research priority. Here, we evaluate how soil ammonium impacts canola root and shoot growth and characterise differences among canola genotypes in regard to resistance to ammonium toxicity. In the first experiment, eight ammonium chloride treatments and five calcium nitrate treatments were tested for their impact on the canola genotype Crusher TT, where high application (60 mg N/kg soil) significantly decreased the dry weight of canola shoots and roots and acidified the soil from pHCaCl2 5.9 to 5.6. In the second experiment, 30 canola genotypes were screened at selected concentrations of NH4+-N, using nitrate as the control. There was wide variation among genotypes in sensitivity to high NH4+-N application. Genotypes G16, G26, and G29 had greater shoot dry weights and the highest shoot N concentration of all genotypes, and G16, G26, and G28 had root dry weight up to 35% higher at high soil NH4+-N compared with other genotypes. In contrast, genotypes G3, G13, and G30 showed the largest reduction in shoot weight, and genotypes G13, G23, and G30 showed the largest reduction in root weight at high NH4+-N application. Residual NH4+-N/kg soil in soil was higher for sensitive than resistant genotypes, suggesting lower NH4+-N use in the former. These results reveal the potential for selecting canola genotypes that are resistant to high NH4+-N concentrations in soil. [ABSTRACT FROM AUTHOR]

A four-component synthesis of 2-phenyl-9H-pyrimido[4,5-b]indoles was developed using indole-3-carboxaldehydes, aromatic aldehyde and ammonium iodide as the raw materials under transition-metal-free conditions. The pyrimidine ring was formed in one pot through [4 + 2] annulation reaction. Four C–N bonds were formed in one pot promoted by iodine and iodide additives. This work is highlighted by using two ammonium iodides as the sole nitrogen source. [ABSTRACT FROM AUTHOR]

The dynamics of nitrogen availability in soil result from the net amount of organic and inorganic inputs undergoing decomposition, mineralization, and immobilization. This varies with soil type, climate, and cropping system management practices. Hence, the interaction of these factors in a specific environment is important for nitrogen management and availability in any cropping system. This study evaluated the concentration of nitrate (NO3−) and ammonium (NH4+) in a maize monocropping system in a long-term trial under different tillage practices, i.e., no-till (NT), conventional tillage (CT), and rotational tillage (RT), and with different nitrogen (Urea) fertiliser application rates (0, 100, and 200 kg/ha N). The experimental area was a split plot with randomized tillage strips as the main plots, with the nitrogen fertiliser application rates forming the subplots. The results found the highest concentration of NO3− (7.728 mg/kg) and NH4+ (0.762 mg/kg) under the NT (p < 0.05) compared to the other treatments. CT recorded the lowest amount of NH4+ (0.648 mg/kg) (p < 0.05) compared to RT (0.758 mg/kg), while the concentration of NO3− (6.755 mg/kg) under the CT was relatively higher than under the RT (4.720 mg/kg). The results also showed that the 0–10 cm depth had a significantly (p < 0.05) higher concentration of NO3− (6.787 mg/kg) and NH4+ (0.851 mg/kg), followed at the 20–30 cm depth with 6.229 mg/kg NO3− and 0.832 mg/kg NH4+. Soil samples taken at 10–20 cm depth recorded the lowest NO3− (6.188 mg/kg) and NH4+ (0.485 mg/kg). The study also found the highest NO3− concentration (0.452 mg/kg) with 200 kg/ha N (p < 0.05), while the highest concentration of NH4+ (0.954 mg/kg) was found with 0 kg/ha N. The lowest concentrations of both NO3− (6.333 mg/kg) and NH4+ (0.561 mg/kg) were found with 100 kg/ha N. the no-till also had a significantly (p < 0.05) higher NO3− (8.518 mg/kg) concentration with 200 kg/ha N compared to the CT (6.005 mg/kg) and RT (4.833 mg/kg). On the other hand, more NH4+ (1.478 mg/kg) was found with 0 kg/ha N under the NT compared to the CT (0.717 mg/kg) and the RT (0.669 mg/kg). The concentration of NH4+ was relatively low with 200 kg/ha N in the NT (0.545 mg/kg) and CT (0.598 mg/kg) but higher in the RT (0.813 mg/kg). In conclusion, the NT favoured the availability of NO3− and NH4+ in the studied cropping system; however, the concentration of these was affected by fertiliser application rate and depth. This suggested that each tillage system should be compatible with the type and the rate of inorganic nitrogen fertiliser for better crop production. [ABSTRACT FROM AUTHOR]

Ammonia nitrogen (NH 4 +-N) is a ubiquitous environmental pollutant, especially in offshore aquaculture systems. Electrochemical oxidation is very promising to remove NH 4 +-N, but suffers from the use of precious metals anodes. In this work, a robust and cheap electrocatalyst, iron single-atoms distributed in nitrogen-doped carbon (Fe-SAs/N-C), was developed for electrochemical removal of NH 4 +-N from in wastewater containing chloride. The Fe-SAs/N-C catalyst exhibited superior activity than that of iron nanoparticles loaded carbon (Fe-NPs/N-C), unmodified carbon and conventional Ti/IrO 2 -TiO 2 -RuO 2 electrodes. And high removal efficiency (> 99%) could be achieved as well as high N 2 selectivity (99.5%) at low current density. Further experiments and density functional theory (DFT) calculations demonstrated the indispensable role of single-atom iron in the promoted generation of chloride derived species for efficient removal of NH 4 +-N. This study provides promising inexpensive catalysts for NH 4 +-N removal in aquaculture wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]

Ammonium transporters (AMTs) are responsible for ammonium absorption and utilization in plants. As a high-nitrogen-demand crop and a legume, soybean can also obtain ammonium from symbiotic root nodules in which nitrogen-fixing rhizobia convert atmospheric nitrogen (N2) into ammonium. Although increasing evidence implicates vital roles of ammonium transport in soybean, no systematic analyses of AMTs in soybean (named GmAMTs) or functional analyses of GmAMTs are available. In this study, we aimed to identify all GmAMT family genes and gain a better understanding of the characteristics of GmAMT genes in soybean. Here, due to the improved genome assembly and annotation of soybean, we tried to generate a phylogenetic tree of 16 GmAMTs based on new information. Consistent with reported data, GmAMT family members can be divided into two subfamilies of GmAMT1 (6 genes) and GmAMT2 (10 genes). Interestingly, unlike Arabidopsis, which has only one AMT2, soybean has substantially increased the number of GmAMT2s, suggesting enhanced demand for ammonium transport. These genes were distributed on nine chromosomes, of which GmAMT1.3, GmAMT1.4, and GmAMT1.5 were three tandem repeat genes. The gene structures and conserved protein motifs of the GmAMT1 and GmAMT2 subfamilies were different. All the GmAMTs were membrane proteins with varying numbers of transmembrane domains ranging from 4 to 11. Promoter analysis found that these GmAMT genes have phytohormone-, circadian control-, and organ expression-related cis-elements in their promoters, and notably, there were nodulation-specific and nitrogen-responsive elements in the promoters of the GmAMT1 and GmAMT2 genes. Further expression data showed that these GmAMT family genes exhibited different spatiotemporal expression patterns across tissues and organs. In addition, GmAMT1.1, GmAMT1.2, GmAMT2.2, and GmAMT2.3 were responsive to nitrogen treatment, while GmAMT1.2, GmAMT1.3, GmAMT1.4, GmAMT1.5, GmAMT1.6, GmAMT2.1, GmAMT2.2, GmAMT2.3, GmAMT3.1, and GmAMT4.6 showed circadian rhythms in transcription. RT-qPCR validated the expression patterns of GmAMTs in response to different forms of nitrogen and exogenous ABA treatments. Gene expression analysis also confirmed that GmAMTs are regulated by key nodulation gene GmNINa, indicating a role of GmAMTs in symbiosis. Together, these data indicate that GmAMTs may differentially and/or redundantly regulate ammonium transport during plant development and in response to environmental factors. These findings provide a basis for future research on the functions of GmAMTs and the mechanisms through which GmAMTs regulate ammonium metabolism and nodulation in soybean. [ABSTRACT FROM AUTHOR]

In China, nitrogen (N) fertilizer is excessively used in sugarcane planting areas, while the nitrogen use efficiency (NUE) of sugarcane is relatively low. Mining and identifying the key genes in response to low N stress in sugarcane can provide useful gene elements and a theoretical basis for developing sugarcane varieties with high NUE. In our study, RNA-Seq combined with qRT-PCR analysis revealed that the ScAMT1.1 gene responded positively to low N stress, resulting in the stronger low N tolerance and high NUE ability of sugarcane cultivar ROC22. Then, ScAMT1.1 was cloned from sugarcane. The full-length cDNA of the ScAMT1.1 gene is 1868 bp, containing a 1491 bp open reading frame (ORF), and encoding 496 amino acids. ScAMT1.1 belongs to the AMT superfamily and shares 91.57% homologies with AMT1.1 from Oryza sativa. Furthermore, it was stably overexpressed in rice (O. sativa). Under low N treatment, the plant height and the fresh weight of the ScAMT1.1-overexpressed transgenic rice were 36.48% and 51.55% higher than that of the wild-type, respectively. Both the activity of ammonium assimilation key enzymes GS and GDH, and the expression level of ammonium assimilation key genes, including GS1.1, GS1.2, GDH, Fd-GOGAT, and NADH-GOGAT2 in the transgenic plants, were significantly higher than that of the wild-type. The grain number and grain yield per plant in the transgenic rice were 6.44% and 9.52% higher than that of the wild-type in the pot experiments, respectively. Taken together, the sugarcane ScAMT1.1 gene has the potential to improve ammonium assimilation ability and the yield of transgenic rice under low N fertilizer conditions. This study provided an important functional gene for improving sugarcane varieties with high NUE. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) is involved not only in the regulation of plant growth, development, and stress responses but also in the regulation of plant-microbe interactions. Here, we demonstrate that Piriformospora indica can induce tobacco nitrate reductase to produce a NO signal in roots which enhances nitrogen uptake capacity by inducing the expression of ammonium and nitrate transporter genes and the development of lateral root and root hair, thereby promoting tobacco growth. In addition, the NO signal induced by P. indica is significantly different from that induced by the pathogen Phytophthora nicotianae. Inoculation with P. indica did not produce H2O2 and maintained high expression of Phytoglobin 1 in roots, resulting in a significantly lower NO level than in the roots inoculated with P. nicotianae. These findings suggest that an appropriate NO level is the likely basis of plant-P. indica symbiosis, which promotes the growth of host plants. [ABSTRACT FROM AUTHOR]

SUMMARY: Ammonium (NH4+)‐based fertilization efficiently mitigates the adverse effects of nitrogen fertilization on the environment. However, high concentrations of soil NH4+ provoke growth inhibition, partly caused by the reduction of cell enlargement and associated with modifications of cell composition, such as an increase of sugars and a decrease in organic acids. Cell expansion depends largely on the osmotic‐driven enlargement of the vacuole. However, the involvement of subcellular compartmentation in the adaptation of plants to ammonium nutrition has received little attention, until now. To investigate this, tomato (Solanum lycopersicum) plants were cultivated under nitrate and ammonium nutrition and the fourth leaf was harvested at seven developmental stages. The vacuolar expansion was monitored and metabolites and inorganic ion contents, together with intracellular pH, were determined. A data‐constrained model was constructed to estimate subcellular concentrations of major metabolites and ions. It was first validated at the three latter developmental stages by comparison with subcellular concentrations obtained experimentally using non‐aqueous fractionation. Then, the model was used to estimate the subcellular concentrations at the seven developmental stages and the net vacuolar uptake of solutes along the developmental series. Our results showed ammonium nutrition provokes an acidification of the vacuole and a reduction in the flux of solutes into the vacuoles. Overall, analysis of the subcellular compartmentation reveals a mechanism behind leaf growth inhibition under ammonium stress linked to the higher energy cost of vacuole expansion, as a result of alterations in pH, the inhibition of glycolysis routes and the depletion of organic acids. Significance Statement: Ammonium nutrition provoked tomato growth inhibition, partly caused by the reduction of cell enlargement. Combining in vivo pH measurement, non‐aqueous fractionation and mathematical modeling, we report that the decrease in vacuolar pH and organic acid concentrations incurred an increase in the energy cost of solute accumulation in the vacuole, and thus limited cell growth under ammonium nutrition. [ABSTRACT FROM AUTHOR]

Fusarium graminearum is an important wheat pathogen and a producer of deoxynivalenol (DON). Biosynthesis of DON is suppressed by ammonium and induced by arginine and polyamines. To better understand ammonium repression of DON biosynthesis, in this study, we functionally characterized three ammonium permease (MEP) genes in F. graminearum. All the mep deletion mutants were normal in growth on V8 agar. Whereas deletion of MEP1 had no detectable phenotypes, the mep2 and mep3 mutants had defects in hyphal growth under ammonium limiting conditions and infection of wheat heads, with the latter having less severe defects. Deletion of MEP2 but not MEP3 affected nitrogen repression of DON biosynthesis and genes involved in nitrate metabolism. The mep2 mep3 double mutant had more severe defects in nitrogen repression than the mep2 mutant and was defective in ascospore releasing. Mutant alleles of MEP2 with truncated C‐terminal cytoplasmic tail (CT) failed to complement the mep2 mutant. Expression of a dominant active allele of RAS2 partially rescued the defects of mep2 in nitrogen repression. Taken together, these results suggest that Mep2 acts as the major sensor of ammonium availability in F. graminearum and its CT region functions in nitrogen repression via RAS2 and downstream signalling pathways. [ABSTRACT FROM AUTHOR]

Aim: Pacific hagfish are exceptionally tolerant to high environmental ammonia (HEA). Here, we elucidated a cellular mechanism that enables hagfish to actively excrete ammonia against steep ammonia gradients expected to be found inside a decomposing whale carcass. Methods: Hagfish were exposed to varying concentrations of HEA in the presence or absence of environmental Na+, while plasma ammonia levels were tracked. 14C‐methylammonium was used as a proxy for NH4+ to measure efflux in whole animals and in isolated gill pouches; the latter allowed us to assess the effects of amiloride specifically on Na+/H+ exchangers (NHEs) in gill cells. Western blotting and immunohistochemistry were utilized to evaluate the abundance and sub‐cellular localization of Rhesus glycoprotein (Rh) channels in the response to HEA. Results: Hagfish actively excreted NH4+ against steep inwardly directed ENH4+ (ΔENH4+ ~ 35 mV) and pNH3 (ΔpNH3 ~ 2000 μtorr) gradients. Active NH4+ excretion and plasma ammonia hypo‐regulation were contingent on the presence of environmental Na+, indicating a Na+/NH4+ exchange mechanism. Active NH4+ excretion across isolated gill pouches was amiloride‐sensitive. Exposure to HEA resulted in decreased abundance of Rh channels in the apical membrane of gill ionocytes. Conclusions: During HEA exposure, hagfish can actively excrete ammonia against a steep concentration gradient using apical NHEs energized by Na+‐K+‐ATPase in gill ionocytes. Additionally, apical Rh channels are removed from the apical membrane, presumably to reduce ammonia loading from the environment. We suggest that this mechanism allows hagfish to maintain tolerable ammonia levels while feeding inside decomposing carrion, allowing them to exploit nutrient‐rich food‐falls. [ABSTRACT FROM AUTHOR]

The aim was to improve the fertilizer utilization efficiency and alleviate environmental pollution risk under a wheat-maize rotation system. Here, the combinations of different nitrogen stabilizers and phosphorus activators were used to reduce nitrogen loss and phosphorus fixation in the field experiment. Compared to the control, the combination of 1.5%HQ + 0.5%DMPP + biochar showed the most significant effect on the retention of alkali-hydrolysable nitrogen (Nah), the highest with an increase of 22.6% at the 0~20 cm layer soil; and the combination of 1.5%HQ + 3.5%DCD + CMFs (compound microbial fertilizers) showed the most significant effect on the maintenance of available phosphorus (Pa), with the highest increase of 41.3%. N, P synergists combined with a basal fertilizer could effectively slow down the transformation from N H 4 + to N O 3 − , and keep N H 4 + at an increase of 7.38%~19.6%. Moreover, the N, P synergists could efficiently lock the available nutrients around the roots, preventing the migration of N O 3 − , N H 4 + , Nah, and Pa to the deeper layers. Especially for N O 3 − , the total accumulation at 0~60 cm decreased by 32.1%, and the activation of Pa was mainly concentrated at 0~40 cm. Under the same nutrient inputs, the combination of 0.3%NBPT + 0.5%DMPP + CMFs obtained the highest wheat yield. The combination of 1.5%HQ + 0.5%DMPP+ biochar gained the highest maize yield. Overall, the application of N, P synergists could increase the effective duration of Nah, Pa, and N H 4 + in the surface soil, and reduce the accumulation of N O 3 − in the 0~60 cm soil layer. The capacity of holding and keeping nutrients from leaching rose obviously; simultaneously, the assimilative capacity of crops for nitrogen and phosphorus increased distinctly, which could lower the eutrophia risks from nitrogen and phosphorus. [ABSTRACT FROM AUTHOR]

Diatom–diazotroph associations (DDAs) are one of the most important symbiotic dinitrogen (N2) fixing groups in the oligotrophic ocean. Despite their capability to fix N2, ammonium (NH4+) remains a key nitrogen (N) source for DDAs, and the effect of NH4+ on their metabolism remains elusive. Here, we developed a coarse-grained, cellular model of the DDA with NH4+ uptake and quantified how the level of extracellular NH4+ influences metabolism and nutrient exchange within the symbiosis. The model shows that, under a fixed growth rate, an increased NH4+ concentration may lower the required level of N2 fixation and photosynthesis, and decrease carbon (C) and N exchange. A low-NH4+ environment leads to more C and N in nutrient exchange and more fixed N2 to support a higher growth rate. With higher growth rates, nutrient exchange and metabolism increased. Our study shows a strong effect of NH4+ on metabolic processes within DDAs, and thus highlights the importance of in situ measurement of NH4+ concentrations. [ABSTRACT FROM AUTHOR]

In most algae, NO3− assimilation is tightly controlled and is often inhibited by the presence of NH4+. In the marine, non-colonial, non-diazotrophic cyanobacterium Synechococcus UTEX 2380, NO3− assimilation is sensitive to NH4+ only when N does not limit growth. We sequenced the genome of Synechococcus UTEX 2380, studied the genetic organization of the nitrate assimilation related (NAR) genes, and investigated expression and kinetics of the main NAR enzymes, under N or light limitation. We found that Synechococcus UTEX 2380 is a β-cyanobacterium with a full complement of N uptake and assimilation genes and NAR regulatory elements. The nitrate reductase of our strain showed biphasic kinetics, previously observed only in freshwater or soil diazotrophic Synechococcus strains. Nitrite reductase and glutamine synthetase showed little response to our growth treatments, and their activity was usually much higher than that of nitrate reductase. NH4+ insensitivity of NAR genes may be associated with the stimulation of the binding of the regulator NtcA to NAR gene promoters by the high 2-oxoglutarate concentrations produced under N limitation. NH4+ sensitivity in energy-limited cells fits with the fact that, under these conditions, the use of NH4+ rather than NO3− decreases N-assimilation cost, whereas it would exacerbate N shortage under N limitation. [ABSTRACT FROM AUTHOR]

The impacts of nitrogen on environmental quality, greenhouse gas balances, ecosystem and biodiversity in China are of great concern given the magnitude of demand for food and energy. Comprehensive summaries of historic N flows and their critical threats and sustainable management are urgently needed. This paper initially reviews the historical trends of N flows in China and identifies the critical threats of N loss. Subsequently, it describes some recent success stories of N management, and finally indicates barriers to N pollution control. This review highlights three key points. Firstly, a steady increase of N input in China has led to a series of environmental problems via leaching and runoff, ammonia emissions and denitrification. Secondly, although great efforts to improve N management and N safety in China, further quantifications of N flows and analysis of their underlying mechanisms are needed to improve the understanding of the N cycle and pollution control. Finally, it proposes that the best available technologies combined with regulatory plans, laws, projects and policies should be implemented to overcome current barriers in N control and achieve a balance between the sustainable use of N resources and environmental conservation in China. [ABSTRACT FROM AUTHOR]

The global urban area is expanding continuously, resulting in unprecedented emissions and deposition of reactive nitrogen (N) in urban environments. However, large knowledge gaps remain in the ecological effects of N deposition on urban forests that provide key ecosystem services for an increasing majority of city dwellers. The current understanding of the spatial patterns and ecological effects of N deposition in urban forests was synthesized based on a literature review of observational and experimental studies. Nitrogen deposition generally increases closer to cities, resulting in an urban hotspot phenomenon. Chemical components of N deposition also shift across urban-suburban-rural gradients, showing higher ratios of ammonium to nitrate in and around urban areas. The ecological effects of N deposition on urban forest ecosystems are overviewed with a special focus on ecosystem N cycling, soil acidification, nutrient imbalances, soil greenhouse gas emissions, tree growth and forest productivity, and plant and soil microbial diversity. The distinct effects of unprecedented N deposition on urban forests are discussed in comparison with the common effects in natural forests. Despite the existing research efforts, several key research needs are highlighted to fill the knowledge gaps in the ecological effects of N deposition on urban forests. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) are important symbiotic microorganisms in soil that engage in symbiotic relationships with legumes, resulting in mycorrhizal symbiosis. Establishment of strong symbiotic relationships between AMF and legumes promotes the absorption of nitrogen by plants. Ammonium nitrogen can be directly utilised by plants following ammonium transport, but there are few reports on ammonium transporters (AMTs) promoting ammonium nitrogen transport during AM symbiosis. Lotus japonicus is a typical legume model plant that hosts AMF. In this study, we analysed the characteristics of the Lotus japonicus ammonium transporter LjAMT2;2, and found that it is a typical ammonium transporter with mycorrhizal-induced and ammonium nitrogen transport-related cis-acting elements in its promoter region. LjAMT2;2 facilitated ammonium transfer in yeast mutant supplement experiments. In the presence of different nitrogen concentrations, the LjAMT2;2 gene was significantly upregulated following inoculation with AMF, and induced by low nitrogen. Overexpression of LjAMT2;2 increased the absorption of ammonium nitrogen, resulting in doubling of nitrogen content in leaves and roots, thus alleviating nitrogen stress and promoting plant growth. [ABSTRACT FROM AUTHOR]

To improve crop nitrogen recovery efficiency (NRE), plants must be supplied with their preferred form of nitrogen (N). However, whether pH affects crop N-form preference remains unclear. Here, we aimed to explore how maize (Zea mays L.) preference for NH4+ and NO3− is affected by pH and to determine the critical pH controlling this preference. Maize plants were grown with NH4+ or NO3− in different soils (pH 4.32–8.14) and nutrient solutions (pH 4.00–8.00). After harvest, plant dry weights, N content, N uptake, NRE, soil pH, and exchangeable aluminum (Al) were measured. Compared with the effect of NO3−, NH4+ decreased maize dry weight, N uptake, and NRE by 28–94% at soil pHs of 4.32 and 4.36 and a solution pH of 4.00, whereas it increased these parameters by 10–88% at soil pHs of 6.52–8.02 and solution pHs of 7.00 and 8.00. NO3− increased soil pH and decreased soil exchangeable Al content at soil pHs of 4.32–6.68. Critical soil and solution pHs for changing plant growth and N uptake preference for NH4+ vs. NO3− ranged from 5.08 to 5.40 and from 5.50 to 6.59, respectively. In conclusion, the preference of maize seedling growth and N uptake for NH4+ vs. NO3− mainly depends on the pH of the growth medium, and maize seedlings generally prefer NO3− in strongly acid soils but NH4+ in neutral to alkaline soils. [ABSTRACT FROM AUTHOR]

Background: Centella [Centella asiatica (L.) Urban], as a herb, is well known for its nutritional and pharmaceutical value. Nitrogen fertilizer plays a significant role in yield and quality of the herb. The present study was aimed to evaluate the effect of mineral nitrogen on the centella plant yield, total chlorophyll, total flavonoid content, antioxidant activities and C/N ratio.  Methods: The experiment was conducted under greenhouse conditions. Mineral nitrogen fertilizer ammonium nitrate (33% N) was applied with 30, 60, 90 and 120 kg N ha-1, with no N (0 kg ha-1) as the control. The dosage was split into three times application at 7, 14 and 21 days after transplanting. All plants were watered 10-days intervals with the nutrient solution.  Result: The results showed that the increasing doses of nitrogen improved growth rate and overall biomass of centella. Among nitrogen treatments, the 60 kg N ha-1 were found to yield maximum growth and the maximum values of leaf number, leaf area, rosette diameter and petiole length. The application of nitrogen (30-60 kg N ha-1) increased the total chlorophyll and reduced total flavonoid content, antioxidant activity and the C:N ratio. The application of 60 kg N ha-1 of nitrogen should be considered as the optimal amount for reconciling limited yield loss and maintaining the quality of centella. [ABSTRACT FROM AUTHOR]

Understanding how plants adjust their requirements for different N forms can help elucidate plant coexistence strategies in N‐limited desert ecosystems. To understand the mechanisms involved, we investigated whether two desert herbs can directly absorb dissolved organic nitrogen (N) and tested whether the patterns changed over different growth stages.Two dominant herbaceous species, Astragalus arpilobus and Arnebia decumbens, from the southern edge of the Gurbantunggut desert, China, were selected. Short‐term (24 h) 15N‐labelled tracer (15N‐NO3, 15N‐NH4, 2‐13C‐15N‐Glycine) treatments were conducted at two soil depths (0–5 cm and 5–15 cm) in the season of rapid growth (June) and in the peak biomass season (July). Enrichment in 13C and 15N was assessed in the two species receiving glycine.The ratio 13C:15N was 0.21–1.39 at the 24‐h harvest, suggesting that approximately 10.5–69.5% of glycine had been absorbed. The amount of absorbed 15N was significantly affected by species, month, soil depth and N form. The two species absorbed most 15N from the 0–5 cm soil layer, and the absorption rate in July was higher than that in June. The absorption of 15N‐NO3 and 15N‐NH4 was significantly higher than that of 2‐13C‐15N‐Glycine.The results indicate that these herbs could use amino acids in the N‐deficient desert ecosystem. The two co‐existing species used different forms of inorganic N for their requirements and maintained a specific preference throughout various growth stages. [ABSTRACT FROM AUTHOR]

• The content of total nitrogen and ammonia nitrogen in pit mud was rapidly detected. • The characteristic wavelength is extracted by the combination of VCPA-IVSO. • Four prediction models (ELM, SVM, LSSVM, PSO-LSSVM) are established. Total nitrogen and ammonium nitrogen play a pivotal role in preserving the soil's nutrient ecosystem, and rapid determination of their levels in the soil can help improve soil utilization. In this study, hyperspectral imaging technology(HSI) was used to achieve rapid determination of total and ammonia nitrogen in pit mud. Both types of spectral data were pre-processed and the characteristic wavelengths were screened using a combination of variable combined population analysisand iterative variable subset optimization (VCPA-IVSO). Four prediction models (ELM, SVM, LSSVM, PSO-LSSVM) based on characteristic wavelengths and full wavelengths were developed. The results showed that the PSO-LSSVM model with the NIR characteristic wavelengths was more effective in predicting total and ammonia nitrogen in pit sludge (total nitrogen: R c 2 = 0.9999, RMSEC = 0.0014, R p 2 = 0.9892, RMSEP = 0.0111, RPD = 9.6225; ammonia nitrogen: R c 2 = 0.9941, RMSEC = 4.3004, R p 2 = 0.9644, RMSEP = 9.8962, RPD = 5.3).The distribution of total nitrogen and ammonia nitrogen in the region of interest is visually analyzed using the determined best model. These results underscore the potential of HSI as a rapid and non-destructive method for detecting total and ammonia nitrogen levels in pit mud. [ABSTRACT FROM AUTHOR]

In recent decades, anthropogenic emissions in the Gulf of Mexico have caused a deterioration in air quality in surrounding areas, mainly due to particulate matter, sulfur dioxide and nitrogen dioxide. Over this period, interest in reactive nitrogen compounds has increased due to their relationships to air quality and ecosystem impacts associated with atmospheric deposition. In this study we summarize air concentrations of nitrogen dioxide in ambient air and wet atmospheric deposition of nitrate and ammonium along the southern coast of the United States of America and eastern Mexico over the period 2017 to 2020. The highest concentrations of ammonium and nitrate were observed in precipitation at Texas and sites in Mexico, although the highest rates of atmospheric deposition were observed in Florida and Louisiana. The ratio between ammonium and nitrate in precipitation was higher at Mexican stations than in studied sites in the United States, influenced by meteorological factors, atmospheric emissions, and characteristic air mass transport in the region. Back trajectory modeling showed the importance of the seasonality of the wind in the transport of nitrogen compounds of local and regional origin that affect Veracruz. [Display omitted] • In the Gulf of Mexico, anthropogenic emissions have deteriorated air quality. • NO 2 peaks in the cold months and during peak traffic times. • In rural areas, NH 4 + predominates, indicating its relationship with agriculture. • Seasonal meteorological conditions influence the origin of nitrogen compounds in Veracruz. [ABSTRACT FROM AUTHOR]

[Display omitted] • UDB and DB at different pyrolysis temperatures played contrasting roles. • DB800-amended group displayed superior nitrogen removal performance. • DB at lower pyrolysis temperature imposed suppression. • Properties of dissolved organic matter released by DB were tracked at molecular level. Biochar has attracted increasingly attention in the biological wastewater treatment owing to its unique environmental behavior. However, the differential effects of undissolved and dissolved fractions of biochar (hereafter named as UDB and DB, respectively) on the anaerobic ammonium oxidation (anammox) process remain unclear. The study evaluated the nitrogen removal performance of anammox system in response to UDB and DB prepared at different pyrolysis temperatures (300 °C, 550 °C and 800 °C). The DB800-amended group displayed superior nitrogen removal performance with the total nitrogen removal efficiency (TNRE) of 92.8 ± 1.4 %. Compared with CK, TNRE was changed by +5.0 % (UDB300), +0.4 % (UDB550) and −22.3 % (UDB800) for UDB-amended groups, and by −16.0 % (DB300), −9.4 % (DB550), and +9.2 % (DB800) for DB-amended groups, respectively. The differences were closely related to the physicochemical properties of UDB and DB. Particularly, dissolved organic matter released by DB were tracked at molecular level, which revealed that CHO occupied the highest proportion of 70.3 % and lignin-like and carboxylic rich alicyclic molecules were dominant in DB800. This study would facilitate the understanding of the differences between the nitrogen removal performance of UDB and DB-amended anammox, thus providing deeper insights for the comprehensive assessment of the impacts of biochar on the anammox process. [ABSTRACT FROM AUTHOR]

In this study, two experiments were conducted to evaluate the plant response of Brachiaria brizantha cv. MG5 to nitrogen forms and different pH of nutrient solution. For this, nutrient solutions containing ammonium and ammonium nitrate were fixed at pH 4, 6 or 8, and nutrient solution containing nitrate was fixed at pH 6. The pH adjustment was done by different compounds including MES, calcium hydroxide, calcium carbonate and sulfuric acid. In another experiment the seedlings were grown in nutrient solution with different N forms, but without pH adjustment. The results showed that plants in ammonium or ammonium nitrate at pH = 4 had better growth and performance, followed by pH = 6, compared to plants grown at pH = 8 (buffered with calcium carbonate). Calcium carbonate (bicarbonate) especially in higher amounts in nutrient solution (pH = 8) significantly reduced plant growth particularly root growth as the toxic effects were visible on the roots. The adverse effect of carbonate at high pH was more than those at low pH. High concentration of carbonate in presence of ammonium also was toxic for plants probably due to additional toxic effect of ammonia. However, plants were able to grow normally with different N forms under hydroponics culture, independent of pH effect. When pH was not controlled under different N-forms, there was no significant difference between root and shoot biomass production or leaf SPAD value and protein concentration. So, the presence of carbonate but not pH, was determined as an inhibiting factor for growth of Palisadegrass plants. [ABSTRACT FROM AUTHOR]

Nitrogen recycling between Earth's interior and exterior determines the evolution of the atmosphere and habitability of the planet. However, the contribution of subduction to the deep nitrogen recycling is still highly debated. Ammonium‐bearing silicate minerals are the main nitrogen carriers in subduction zones. Nitrogen retention in subduction‐zone minerals determines the subducted nitrogen fluxes to the deep Earth. Here, we reveal ammonium behavior in a natural ammonium‐bearing feldspar at elevated temperatures to 1000°C and pressures to 19.99 GPa. With increasing temperature and pressure, ammonium interacts with the silicate framework and forms hydrogen bonding. The ammonium loss rates are on the order of 10−15, 10−14, and 10−13 at 800, 900, and 1000°C, respectively, with activation energy of 271 ± 13 kJ/mol. The activation energy of ammonium loss in feldspar is higher than that in phengite. Moreover, the ammonium diffusivities are similar to that of hydrogen in feldspar, but much slower than that of molecular water and faster than those of K and Ar. The results imply that most of nitrogen can be potentially retain in the feldspar structure before feldspar breakdown. Considering that feldspar could be stable to a great depth along cold subduction, it could be a potential carrier for nitrogen transport to the deep Earth. Plain Language Summary: Feldspar is an important constituent of Earth's crust and has a large affinity of nitrogen as ammonium in the structure. Here, we report nitrogen retention in feldspar at high temperature and high pressure. Our data show that ammonium interacts with the silicate framework and forms hydrogen bonding with increasing temperature and pressure. Ammonium is more stable in feldspar than in phengite, with similar diffusion kinetics to hydrogen in feldspar. Therefore, ammonium may be carried by feldspar to a great depth along cold subduction. Key Points: Ammonium interacts with the silicate framework and forms hydrogen bonding with increasing temperature and pressureAmmonium loss has the similar kinetics to hydrogen in feldspar, with larger activation energy in feldspar than that in phengiteFeldspar is a potential carrier for nitrogen transport in subduction zones [ABSTRACT FROM AUTHOR]

Nitrogen deficiency frequently occurs in agricultural soil because of ammonia volatilization to the environment, resulting in low urea-N use efficiency by plants. A laboratory incubation experiment was conducted to assess the effect of rice straw and rice husk biochar's on ammonia volatilization, soil pH, exchangeable ammonium, and available nitrate in comparison to the urea without additives under waterlogged conditions. Application of rice straw and rice husk biochar's mixture at application rate 5-10 t ha-1 had significantly minimized ammonia volatilization by 30.86% - 38.61% over T1 (175 kg ha-1 urea). T2 (5 t ha-1) and T3 (10 t ha-1) also had significantly increased retention of ammonium by 79% - 95% and nitrate ions by 49% - 51% over control. The treatments amended with biochar had successfully improved soil pH compared to T0 (soil only) and T1. Hence, the findings suggest that urea amended with rice straw and rice husk biochar's altered the nutrients level in the soil by minimizing ammonia loss to enhance nitrogen availability in waterlogged conditions. [ABSTRACT FROM AUTHOR]

Background: Nitrate (NO3−) and ammonium (NH4+) are the primary forms of inorganic nitrogen (N) taken up by plant roots, and a lack of these N sources commonly limits plant growth. To better understand how NO3− and NH4+ differentially affect root system architecture, we analyzed the expression profiles of microRNAs and their targets in poplar roots treated with three forms of nitrogen S1 (NO3−), S2 (NH4NO3, normal), and S3 (NH4+) via RNA sequencing. Results: The results revealed a total of 709 miRNAs. Among them, 57 significantly differentially expressed miRNAs and 28 differentially expressed miRNA-target pairs showed correlated expression profiles in S1 vs. S2. Thirty-six significantly differentially expressed miRNAs and 12 differentially expressed miRNA-target pairs showed correlated expression profiles in S3 vs. S2. In particular, NFYA3, a target of upregulated ptc-miR169i and ptc-miR169b, was downregulated in S1 vs. S2, while NFYA1, a target of upregulated ptc-miR169b, was downregulated in S3 vs. S2 and probably played an important role in the changes in root morphology observed when the poplar plants were treated with different N forms. Furthermore, the miRNA-target pairs ptc-miR169i/b-D6PKL2, ptc-miR393a-5p-AFB2, ptc-miR6445a-NAC14, ptc-miR172d-AP2, csi-miR396a-5p_R + 1_1ss21GA-EBP1, ath-miR396b-5p_R + 1-TPR4, and ptc-miR166a/b/c-ATHB-8 probably contributed to the changes in root morphology observed when poplar plants were treated with different N forms. Conclusions: These results demonstrate that differentially expressed miRNAs and their targets play an important role in the regulation of the poplar root system architecture by different N forms. [ABSTRACT FROM AUTHOR]

Karenia mikimotoi is a toxic bloom-forming dinoflagellate that sometimes co-blooms with Karenia brevis in the Gulf of Mexico, especially on the West Florida Shelf where strong vertical temperature gradients and rapid changes in nitrogen (N) can be found. Here, the short-term interactions of temperature, N form, and availability on photosynthesis-irradiance responses were examined using rapid light curves and PAM fluorometry in order to understand their interactions, and how they may affect photosynthetic yields. Cultures of K. mikimotoi were enriched with either nitrate (NO3), ammonium (NH4 +), or urea with varying amounts (1, 5, 10, 20, 50 μM-N) and then incubated at temperatures of 15, 20, 25, 30 °C for 1 h. At 15-25 °C, fluorescence parameters (Fv/Fm, rETR) when averaged for all N treatments were comparable. Within a given light intensity, increasing all forms of N concentrations generally led to higher photosynthetic yields. Cells appeared to dynamically balance the "push" due to photon flux pressure and reductant generation, with consumption in overall metabolism ("pull" due to demand). However, at 30 °C, all fluorescence parameters declined precipitously, but differential responses were observed depending on N form. Cells enriched with urea at 30 °C showed a smaller decline in fluorescence parameters than cells treated with NO3 or NH4 +, implying that urea might induce a photoprotective mechanism by increasing metabolic "pull". [ABSTRACT FROM AUTHOR]

[Display omitted] • NF-HOB showed elevated levels of CO 2 and N 2 fixation under continuous gas supply. • The highest biomass yield of NF-HOB communities reached 0.153 g CDW/g COD-H 2. • Rich ammonium enhanced H 2 and CO 2 absorption for HOB communities. • Xanthobacter was enriched only in the presence of ammonium. • Ammonium boosted the abundance of nitrogenase and glutamate synthase. To investigate the effects of nitrogen source supply on microbial protein (MP) production by hydrogen-oxidizing bacteria (HOB) under continuous feed gas provision, a sequencing batch culture comparison (N 2 fixation versus ammonium assimilation) was performed. The results confirmed that even under basic cultivation conditions, N 2 -fixing HOB (NF-HOB) communities showed higher levels of CO 2 and N 2 fixation (190.45 mg/L Δ COD t and 11.75 mg/L Δ TN biomass) than previously known, with the highest biomass yield being 0.153 g CDW/g COD-H 2. Rich ammonium stimulated MP synthesis and the biomass accumulation of communities (increased by 7.4 ～ 14.3 times), presumably through the enhancement of H 2 and CO 2 absorption. The micro mechanism may involve encouraging the enrichment of species like Xanthobacter and Acinetobacter then raising the abundance of nitrogenase and glutamate synthase to facilitate the nitrogen assimilation. This would provide NF-HOB with ideas for optimizing their MP synthesis activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel fungal strain perform aerobically simultaneous removal of N and P. • The nutrient removal pathway was revealed. • Nitrogen dissimilation via heterotrophic nitrification and aerobic denitrification. • Phosphorus was mainly stored in extracellular polymeric substances. • Treating real domestic treatment indicates its stability and high efficiency. Fungi with multiple contaminant removal function have rarely been studied. Here, a novel fungal strain Fusarium keratoplasticum FSP1, which was isolated from halophilic granular sludge, is reported for first time to perform simultaneous nitrogen and phosphate removal. The strain showed wide adaptability under C/N ratios of 30–35, salinities of 0 %–3 % (m/v), and pH of 7.5–9.5. The maximum removal rates of ammonium, nitrate and nitrite were 4.43, 4.01 and 2.97 mg N/L/h. The nitrogen balance, enzyme activity and substrate conversion experiments demonstrated a single strain FSP1 can assimilate inorganic nitrogen and convert inorganic nitrogen to gaseous nitrogen through heterotrophic nitrification or aerobic denitrification. About 39 %–42 % of the degraded phosphorus was in the extracellular polymeric substances (EPS). Orthophosphate was the main phosphorus species in the cell, whereas phosphate monoester and diester were in the EPS. The novel strain FSP1 is a potential candidate for wastewater treatment. [ABSTRACT FROM AUTHOR]

Most plant species develop stress symptoms when exposed to high ammonium (NH4+) concentrations. The root is the first organ in contact with high NH4+ and therefore the first barrier to cope with ammonium stress. In this work, we focused on root adaptation to ammonium nutrition in the model plant Brachypodium distachyon. Proteome analysis revealed changes associated with primary metabolism, cell wall remodelling, and redox homeostasis. In addition, it showed a strong induction of proteins related to methionine (Met) metabolism and phytosiderophore (PS) synthesis in ammonium-fed plants. In agreement with this, we show how ammonium nutrition impacts Met/ S -adenosyl-Met and PS metabolic pathways together with increasing root iron content. Nevertheless, ammonium-fed plants displayed higher sensitivity to iron deficiency, suggesting that ammonium nutrition triggers impaired iron utilization and root to shoot transport, which entailed an induction in iron-related responses. Overall, this work demonstrates the importance of iron homeostasis during ammonium nutrition and paves a new way to better understand and improve ammonium use efficiency and tolerance. [ABSTRACT FROM AUTHOR]

The response of pepper (Capsicum annuum L.) to Ammonium-N was studied in a multispan greenhouse under soilless culture using coir fiber as substrate. Ammonium-N application rates were 0, 2, 4, 6 and 8 mM with a total-N concentration of 13 mM. The total content of the rest of all macronutrients in the nutrient solution was maintained from the beginning of the experiment until the end. The highest water uptake was recorded at 2 mM ammonium concentration in the nutrient solution. Compared to nitrate, ammonium nitrogen caused a decrease in nitrate absorption, but led to an increase when applying 8 mM ammonium. Despite a progressive increase in ammonium content in the nutrient solution, potassium absorption was constant below the ammonium concentration of 8 mM. Under a high N-NH4 content (from 6 to 8 mM) in the nutrient solution, high toxicity was found, deriving in the appearance of deformed or noncommercial fruits. There was a significant benefit by the use of ammonium as a component in the nutrient solution. The optimum yield ammonium concentrations were found in the range from 2 to 4 mM. Nevertheless, concentrations higher than 6 mM led into a decrease in commercial production, with the production of increasing deformed fruit, out of size and/or blossom-end rot. [ABSTRACT FROM AUTHOR]

Background and Aims The utility of root hairs for nitrogen (N) acquisition is poorly understood. Methods We explored the utility of root hairs for N acquisition in the functional–structural model SimRoot and with maize genotypes with variable root hair length (RHL) in greenhouse and field environments. Key Results Simulation results indicate that long, dense root hairs can improve N acquisition under varying N availability. In the greenhouse, ammonium availability had no effect on RHL and low nitrate availability increased RHL, while in the field low N reduced RHL. Longer RHL was associated with 216 % increase in biomass and 237 % increase in plant N content under low-N conditions in the greenhouse and a 250 % increase in biomass and 200 % increase in plant N content in the field compared with short-RHL phenotypes. In a low-N field environment, genotypes with long RHL had 267 % greater yield than those with short RHL. We speculate that long root hairs improve N capture by increased root surface area and expanded soil exploration beyond the N depletion zone surrounding the root surface. Conclusions We conclude that root hairs play an important role in N acquisition. We suggest that root hairs merit consideration as a breeding target for improved N acquisition in maize and other crops. [ABSTRACT FROM AUTHOR]

Downy mildew (Peronospora belbahrii) is a severe disease in sweet basil. The aim of the present research was to study the effect of total nitrogen (N) concentration and NH4+ partial concentration in sweet basil fertigation on sweet basil downy mildew (SBDM). The study was conducted under controlled conditions, semi-commercial conditions, and commercial-like (field) conditions. Increasing the total N concentration in the irrigation water from 1.1 to 10.7 mM resulted in a gradual increase in N concentration in the shoots, and SBDM severity in potted sweet basil plants. Similarly, under commercial-like greenhouse conditions, higher N in the irrigation water resulted in higher SBDM severity. A high rate of 30–40% of the total N of NH4+ in the irrigation water, was associated with lower SBDM severity. Mineral concentration in the shoots of sweet basil was measured in all greenhouse plots. Shoot concentrations of N, P, K, and Ca were positively correlated with SBDM severity, while shoot concentrations of Mg and Cl negatively correlated with disease severity. In conclusion, N fertigation affected SBDM severity. We suggest that the effect of N fertigation on disease may be due to the change in N concentration in the tissue, or the change in other nutritional element (s). [ABSTRACT FROM AUTHOR]