Expression of the nos operon proteins from Pseudomonas stutzeri in transgenic plants to assemble nitrous oxide reductase

Nitrous oxide (N(2)O) is a stable greenhouse gas that plays a significant role in the destruction of the ozone layer. Soils are a significant source of atmospheric N(2)O. It is important to explore some innovative and effective biology-based strategies for N(2)O mitigation. The enzyme nitrous oxide reductase (N(2)OR), naturally found in soil bacteria, is responsible for catalysing the final step of the denitrification pathway, conversion of N(2)O to dintrogen gas (N(2)). To transfer this catalytic pathway from soil into plants and amplify the abundance of this essential mechanism (to reduce global warming), a mega-cassette of five coding sequences was assembled to produce transgenic plants heterologously expressing the bacterial nos operon in plant leaves. Both the single-gene transformants (nosZ) and the multi-gene transformants (nosFLZDY) produced active recombinant N(2)OR. Enzymatic activity was detected using the methyl viologen-linked enzyme assay, showing that extracts from both types of transgenic plants exhibited N(2)O-reducing activity. Remarkably, the single-gene strategy produced higher reductase capability than the whole-operon approach. The data indicate that bacterial N(2)OR expressed in plants could convert N(2)O into inert N(2) without involvement of other Nos proteins. Silencing by homologous signal sequences, or cryptic intracellular targeting are possible explanations for the low activities obtained. Expressing N(2)OR from Pseudomonas stutzeri in single-gene transgenic plants indicated that such ag-biotech solutions to climate change have the potential to be easily incorporated into existing genetically modified organism seed germplasm.     

Strategy and tactics of disarming GHG at the source: N2O reductase crops

Nitrous oxide (N(2)O), the third most abundant greenhouse gas (GHG), is highly stable and plays a significant role in stratospheric ozone destruction. The primary anthropogenic source of N(2)O stems from use of nitrogen fertilizers in soil. The bacterial enzyme nitrous oxide reductase (N(2)OR), naturally found in some soils, is the only known enzyme capable of catalyzing the final step of the denitrification pathway, conversion of N(2)O to N(2). In this opinion, we discuss potential biology-based strategies to reduce N(2)O by amplifying the amount of available enzyme catalyst in agri-system environments during crop growth and in post-harvest detritus. N(2)OR from Pseudomonas stutzeri has been tested in transgenic plants with promising results. Such seed-borne phytoremediation systems targeted towards GHGs merit field testing.     

Aerobic denitrifying bacteria that produce low levels of nitrous oxide

Most denitrifiers produce nitrous oxide (N(2)O) instead of dinitrogen (N(2)) under aerobic conditions. We isolated and characterized novel aerobic denitrifiers that produce low levels of N(2)O under aerobic conditions. We monitored the denitrification activities of two of the isolates, strains TR2 and K50, in batch and continuous cultures. Both strains reduced nitrate (NO(3)(-)) to N(2) at rates of 0.9 and 0.03 micro mol min(-1) unit of optical density at 540 nm(-1) at dissolved oxygen (O(2)) (DO) concentrations of 39 and 38 micro mol liter(-1), respectively. At the same DO level, the typical denitrifier Pseudomonas stutzeri and the previously described aerobic denitrifier Paracoccus denitrificans did not produce N(2) but evolved more than 10-fold more N(2)O than strains TR2 and K50 evolved. The isolates denitrified NO(3)(-) with concomitant consumption of O(2). These results indicated that strains TR2 and K50 are aerobic denitrifiers. These two isolates were taxonomically placed in the beta subclass of the class Proteobacteria and were identified as P. stutzeri TR2 and Pseudomonas sp. strain K50. These strains should be useful for future investigations of the mechanisms of denitrifying bacteria that regulate N(2)O emission, the single-stage process for nitrogen removal, and microbial N(2)O emission into the ecosystem.     

广东省入库河口N2O分布和通量的时空变化

本研究于2011年7月(丰水期)和12月(枯水期)分别对广东省13个水库的入库河口进行调查,使用吹扫捕集-气相色谱法测定了水中N2O的浓度并用Liss&Merlivat公式估算出入库河口向大气释放N2O的水-气交换通量。结果表明,河口丰水期N2O溶存浓度范围为15.37～175.22 nmol/L,平均值为(73.77±43.58)nmol/L;N2O水-气交换通量范围为0.26～5.40μmol/(m2.d),平均值是(2.53±1.94)μmol/(m2.d)。河口枯水期N2O溶存浓度范围为44.26～366.11 nmol/L,平均值是(126.61±102.74)nmol/L;N2O水-气交换通量范围是0.86～21.88μmol/(m2.d),平均值是(7.50±6.65)μmol/(m2.d)。河口丰水期N2O溶存浓度和水-气交换通量明显低于枯水期。与其他研究相比,本研究区N2O溶存浓度和水-气交换通量偏低。     

Nitrogen oxide gas emissions from temperate forest soils receiving long-term nitrogen inputs

From spring 2000 through fall 2001, we measured nitric oxide (NO) and nitrous oxide (N₂O) fluxes in two temperate forest sites in Massachusetts, USA that have been treated since 1988 with different levels of nitrogen (N) to simulate elevated rates of atmospheric N deposition. Plots within a pine stand that were treated with either 50 or 150 kg N ha^?1 yr^?1 above background displayed consistently elevated NO fluxes (100–200 µg N m^?2 h^?1) compared to control plots, while only the higher N treatment plot within a mixed hardwood stand displayed similarly elevated NO fluxes. Annual NO emissions estimated from monthly sampling accounted for 3.0–3.7% of N inputs to the high‐N plots and 8.3% of inputs to the Pine low‐N plot. Nitrous oxide fluxes in the N‐treated plots were generally < 10% of NO fluxes. Net nitrification rates (NRs) and NO production rates measured in the laboratory displayed patterns that were consistent with field NO fluxes. Total N oxide gas flux was positively correlated with contemporaneous measurements of NR and concentration. Acetylene inhibited both nitrification and NO production, indicating that autotrophic nitrification was responsible for the elevated NO production. Soil pH was negatively correlated with N deposition rate. Low levels (3–11 µg N kg^?1) of nitrite () were detected in mineral soils from both sites. Kinetic models describing NO production as a function of the protonated form of (nitrous acid [HNO₂]) adequately described the mineral soil data. The results indicate that atmospheric deposition may generate losses of gaseous NO from forest soils by promoting nitrification, and that the response may vary significantly between forest types under similar climatic regimes. The lowering of pH resulting from nitrification and/or directly from deposition may also play a role by promoting reactions involving HNO₂.     

不同施肥方式对土壤氨挥发和氧化亚氮排放的影响

采用密闭室间歇通气法和静态箱法对不同施肥方式(撒施后翻耕、条施后覆土、撒施后灌水)下的土壤氨挥发和氧化亚氮排放进行了研究.结果表明:不同施肥方式显著影响了土壤中的氨挥发和氧化亚氮排放.撒施后灌水处理明显促进了氨挥发,其最大氨挥发速率明显高于其它处理,氨挥发累计达2.465 kg N·hm-2.不同施肥方式下氧化亚氮排放通量存在显著差异(P《0.05),且峰值出现时间也不同.施肥后第2天,撒施后灌水处理达到峰值,为193.66 μg·m-2·h-1,而条施后覆土处理在施肥后第5天才出现峰值,为51.13 μg·m-2·h-1,且其排放峰值在3种施肥方式中最低.撒施后灌水处理的氧化亚氮累积净排放量达121.55 g N·hm-2,显著大于撒施后翻耕和条施后覆土处理.撒施后翻耕和条施后覆土处理能有效抑制氨挥发和氧化亚氮排放损失,是较为合理的施肥方式.     

Requirements for Cu(A) and Cu-S center assembly of nitrous oxide reductase deduced from complete periplasmic enzyme maturation in the nondenitrifier Pseudomonas putida

Bacterial nitrous oxide (N(2)O) reductase is the terminal oxidoreductase of a respiratory process that generates dinitrogen from N(2)O. To attain its functional state, the enzyme is subjected to a maturation process which involves the protein-driven synthesis of a unique copper-sulfur cluster and metallation of the binuclear Cu(A) site in the periplasm. There are seven putative maturation factors, encoded by nosA, nosD, nosF, nosY, nosL, nosX, and sco. We wanted to determine the indispensable proteins by expressing nos genes from Pseudomonas stutzeri in the nondenitrifying organism Pseudomonas putida. An in silico study of denitrifying bacteria revealed that nosL, nosX (or a homologous gene, apbE), and sco, but not nosA, coexist consistently with the N(2)O reductase structural gene and other maturation genes. Nevertheless, we found that expression of only three maturation factors (periplasmic protein NosD, cytoplasmic NosF ATPase, and the six-helix integral membrane protein NosY) together with nosRZ in trans was sufficient to produce catalytically active holo-N(2)O reductase in the nondenitrifying background. We suggest that these obligatory factors are required for Cu-S center assembly. Using a mutational approach with P. stutzeri, we also studied NosA, the Cu-containing outer membrane protein previously thought to have Cu insertase function, and ScoP, a putative membrane-anchored chaperone for Cu(A) metallation. Both of these were found to be dispensable elements for N(2)O reductase biosynthesis. Our experimental and in silico data were integrated in a model of N(2)O reductase maturation.     

Plant-mediated nitrous oxide emissions from beech (Fagus sylvatica) leaves

Nitrous oxide (N2O) emission estimates from forest ecosystems are based currently on emission measurements using soil enclosures. Such enclosures exclude emissions via tall plants and trees and may therefore underestimate the whole-ecosystem N2O emissions. Here, we measured plant-mediated N2O emissions from the leaves of potted beech (Fagus sylvatica) seedlings after fertilizing the soil with 15N-labelled ammonium nitrate (15NH4(15)NO3), and after exposing the roots to elevated concentrations of N2O. Ammonium nitrate fertilization induced N2O + 15N2O emissions from beech leaves. Likewise, the foliage emitted N2O after beech roots were exposed to elevated concentrations of N2O. The average N2O emissions from the fertilization and the root exposure experiments were 0.4 and 2.0 microg N m(-2) leaf area h(-1), respectively. Higher than ambient atmospheric concentrations of N2O in the leaves of the forest trees indicate a potential for canopy N2O emissions in the forest. Our experiments demonstrate the existence of a previously overlooked pathway of N2O to the atmosphere in forest ecosystems, and bring about a need to investigate the magnitude of this phenomenon at larger scales.     

The production and emission of nitrous oxide from headwater streams in the Midwestern United States

The emission of nitrous oxide (N₂O) from streams draining agricultural landscapes is estimated by the Intergovernmental Panel on Climate Change (IPCC) to constitute a globally significant source of this gas to the atmosphere, although there is considerable uncertainty in the magnitude of this source. We measured N₂O emission rates and potential controlling variables in 12 headwater streams draining a predominantly agricultural basin on glacial terrain in southwestern Michigan. The study sites were nearly always supersaturated with N₂O and emission rates ranged from ?8.9 to 266.8 μg N₂O‐N m^?2 h^?1 with an overall mean of 35.2 μg N₂O‐N m^?2 h^?1. Stream water NO₃^? concentrations best‐predicted N₂O emission rates. Although streams and agricultural soils in the basin had similar areal emission rates, emissions from streams were equivalent to 6% of the anthropogenic emissions from soils because of the vastly greater surface area of soils. We found that the default value of the N₂O emission factor for streams and groundwater as defined by the IPCC (EF5‐g) was similar to the value observed in this study lending support to the recent downward revision to EF5‐g. However, the EF5‐g spanned four orders of magnitude across our study sites suggesting that the IPCC's methodology of applying one emission factor to all streams may be inappropriate.     

冻融作用下土壤物理和微生物性状变化与氧化亚氮排放的关系

在中、高纬度及高海拔地区,土壤冻融交替现象普遍存在.冻融作用影响土壤的物理和微生物性状,影响土壤的氮素转化过程和强度,导致土壤温室气体氧化亚氮排放增多,使冻融区土壤成为氧化亚氮的重要排放源.冻融作用改变了土壤水分特征和土壤团聚体的稳定性;冻融作用使土壤微生物量、微生物的组成和结构发生改变,导致微生物标识物氨基糖种类和数量改变.本文概述了上述变化与氧化亚氮排放的关系,简要提出了冻融作用下土壤氧化亚氮产生、排放的理论问题及其研究去向.     

Influence of nutrient solution pH on N2O and N2 emissions from a soilless culture system

The influence of nutrient solution pH on the emission of N2O and N2 was investigated during cultivation of cucumbers in a closed-loop rockwool system. Between pH 4 and 7 these gaseous nitrogen losses increased from 1.6 to 21.1% of the N fertilizer input. This was equivalent to average flux rates of 0.06 and 0.85 kg nitrogen per hectare greenhouse area and day, respectively. The N2O/N2 ratio was inversely related to the total gaseous nitrogen losses. At neutral pH dinitrogen was the main emission product, whereas more acidic conditions favoured the emission of nitrous oxide. The pH effects were probably not indirectly affected by root respiration or exudation as much as by a direct inhibition of the activity of denitrifying microorganisms due to high H+ concentrations since similar results were obtained in unplanted nutrient solution systems with the addition of glucose as carbon source. Despite the low microbial denitrification activity under acidic conditions, nitrogen balance deficits of up to one-fifth of the N input still occurred. It is suggested these losses were predominantly caused by chemodenitrification.     

Emission of Methane and Nitrous Oxide by Australian Mangrove Ecosystems

Abstract: The fluxes of the greenhouse gases methane (CH₄) and nitrous oxide (N₂O) were measured in mangrove wetlands in Queensland, Australia, using the closed chamber technique. Large differences in the fluxes of both gases from different study sites were observed, which presumably depended on differences in substrate availability. CH₄ emission rates were in the range of 20 to 350 μg m^‐2 h^‐1, whereas N₂O fluxes were lower, amounting to ‐ 2 to 14 μg m^‐2 h^‐1. In general, the field sites with high substrate availability showed higher emissions than sites with poor nutrient supply. This assumption is supported by the observation of dramatically increased N₂O emissions (150 ‐ 400 μg m^‐2 h^‐1) if study sites were artificially fertilised with additional N. As expected, N fertilisation did not alter CH₄ fluxes during the period of investigation. In the present study, it was confirmed that the mangrove vegetation may play a role as a transport path for CH₄ and N₂O by facilitating diffusion out of the soil. Prop roots from Rhizophora stylosa emitted CH₄ and N₂O at rates of 2.6 and 3.3 μg m^‐2 root surface h^‐1, respectively, whereas the soil of this stand acted as a sink for CH₄. As a consequence, the ecosystem as a whole could constitute a CH₄ source despite CH₄ uptake by the soil. In contrast to prop roots, the presence of pneumatophores in Avicennia marina led to a significant increase in CH₄ emissions from mangrove soils, but did not enhance N₂O emissions. These findings indicate that mangrove ecosystems may be considered a significant source of N₂O and that anthropogenic nutrient input into these ecosystems will lead to enhanced source strengths. For an up‐scaling of greenhouse gas emissions from mangrove forests to a global scale, more information is needed, particularly on the significance of vegetation.     

Growth yield of denitrifiers using nitrous oxide as a terminal electron acceptor

The molar yields (g cell/mol) forAlcaligenes faecalis, Pseudomonas stutzeri, Paracoccus denitrificans andPseudomonas perfectomarinus batch cultures, under nitrous oxide (N₂O) as the electron acceptor, were 11.2, 8.2, 6.1 and 4.4, respectively.Paracoccus denitrificans andPseudomonas perfectomarinus, which had the slowest growth rates, gave the lowest yields. Large maintenance energy costs may be partially responsible for this. The growth efficiencies ofA. faecalis andPs. perfectomarinus on N₂O indicate that the numbers of sites for oxidative phosphorylation in the electron transport system associated with N₂O reduction are about 49% and 39% of those in the electron transport system associated with O₂ respiration, respectively.     

Night and day: short‐term variation in nitrogen chemistry and nitrous oxide emissions from streams

1. Diel variation in metabolism contributes to variation in oxygen (O₂) concentrations in streams. This variation in O₂ and other parameters (e.g. pH) can in turn affect the rates of microbial nitrogen (N) processing, concentrations of nitrogenous solutes and production of the greenhouse gas nitrous oxide (N₂O). We investigated diel variability in emissions of N₂O and the magnitude of short‐term variability in N solutes across 10 streams. 2. Nitrous oxide fluxes varied on average 2.3‐fold over diel cycles. Concentrations would be underestimated by sampling around noon, but N₂O fluxes would not show a consistent bias. Time‐weighted mean daily N₂O flux was strongly related to nitrate concentration (r² = 0.58). Diel patterns in N₂O and dissolved N species were often complex (rather than simple sinusoidal curves), probably reflecting complex underlying processes. 3. Reliance on samples obtained around noon would overestimate daily mean nitrate concentrations by 5% and underestimate ammonium by 32% (average bias across all streams and dates). 4. Dissolved organic N did not show consistent day–night variation. However, the magnitude of diel variability was similar to that observed for dissolved inorganic N. Organic and inorganic N concentrations were often similar. Both appear to be dynamic components of stream N budgets. 5. The Intergovernmental Panel on Climate Change (IPCC) relies upon an emission factor to estimate indirect agricultural N₂O emissions from streams and ground water. The measured emission factor (defined as the ratio of concentrations of N₂O‐N to ‐N) was typically below the recently revised IPCC default figure. Measured values varied on average 1.8‐fold over approximately 24‐h periods and were slightly higher at night than by day. The emission factor was actually highest in streams that were net sinks for N₂O, highlighting a conceptual problem in the current IPCC method. 6. Typical sampling programmes rely on daytime‐only sampling, which might cause bias in results. In our study streams, the bias was generally small. Diel variation in nitrate concentrations was related to mean temperature; variation in ammonium and N₂O concentrations was greatest at low concentrations of nitrite and ammonium.     

Diurnal fluctuations of dissolved nitrous oxide (N2O) concentrations and estimates of N2O emissions from a spring-fed river: implications for IPCC methodology

There is uncertainty in the estimates of indirect nitrous oxide (N₂O) emissions as defined by the Intergovernmental Panel on Climate Change (IPCC). The uncertainty is due to the challenge and dearth of in situ measurements. Recent work in a subtropical stream system has shown the potential for diurnal variability to influence the downstream N transfer, N form, and estimates of in‐stream N₂O production. Studies in temperate stream systems have also shown diurnal changes in stream chemistry. The objectives of this study were to measure N₂O fluxes and dissolved N₂O concentrations from a spring‐fed temperate river to determine if diurnal cycles were occurring. The study was performed during a 72 h period, over a 180 m reach, using headspace chamber methodology. Significant diurnal cycles were observed in radiation, river temperature and chemistry including dissolved N₂O‐N concentrations. These data were used to further assess the IPCC methodology and experimental methodology used. River NO₃‐N and N₂O‐N concentrations averaged 3.0 mg L⁻¹ and 1.6 μg L⁻¹, respectively, with N₂O saturation reaching a maximum of 664%. The N₂O‐N fluxes, measured using chamber methodology, ranged from 52 to 140 μg m⁻² h⁻¹ while fluxes predicted using the dissolved N₂O concentration ranged from 13 to 25 μg m⁻² h⁻¹. The headspace chamber methodology may have enhanced the measured N₂O flux and this is discussed. Diurnal cycles in N₂O% saturation were not large enough to influence downstream N transfer or N form with variability in measured N₂O fluxes greater and more significant than diurnal variability in N₂O% saturation. The measured N₂O fluxes, extrapolated over the study reach area, represented only 6 × 10⁻⁴% of the NO₃‐N that passed through the study reach over a 72 h period. This is only 0.1% of the IPCC calculated flux.     

Fine root dynamics and trace gas fluxes in two lowland tropical forest soils

Fine root dynamics have the potential to contribute significantly to ecosystem‐scale biogeochemical cycling, including the production and emission of greenhouse gases. This is particularly true in tropical forests which are often characterized as having large fine root biomass and rapid rates of root production and decomposition. We examined patterns in fine root dynamics on two soil types in a lowland moist Amazonian forest, and determined the effect of root decay on rates of C and N trace gas fluxes. Root production averaged 229 (±35) and 153 (±27) g m^?2 yr^?1 for years 1 and 2 of the study, respectively, and did not vary significantly with soil texture. Root decay was sensitive to soil texture with faster rates in the clay soil (k=?0.96 year^?1) than in the sandy loam soil (k=?0.61 year^?1), leading to greater standing stocks of dead roots in the sandy loam. Rates of nitrous oxide (N₂O) emissions were significantly greater in the clay soil (13±1 ng N cm^?2 h^?1) than in the sandy loam (1.4±0.2 ng N cm^?2 h^?1). Root mortality and decay following trenching doubled rates of N₂O emissions in the clay and tripled them in sandy loam over a 1‐year period. Trenching also increased nitric oxide fluxes, which were greater in the sandy loam than in the clay. We used trenching (clay only) and a mass balance approach to estimate the root contribution to soil respiration. In clay soil root respiration was 264–380 g C m^?2 yr^?1, accounting for 24% to 35% of the total soil CO₂ efflux. Estimates were similar using both approaches. In sandy loam, root respiration rates were slightly higher and more variable (521±206 g C m² yr^?1) and contributed 35% of the total soil respiration. Our results show that soil heterotrophs strongly dominate soil respiration in this forest, regardless of soil texture. Our results also suggest that fine root mortality and decomposition associated with disturbance and land‐use change can contribute significantly to increased rates of nitrogen trace gas emissions.     

Seasonal variation in nitrous oxide and methane emissions from subtropical estuary and coastal mangrove sediments, Australia

Mangrove sediments can act as sources of the greenhouse trace gases, nitrous oxide (N(2) O) and methane (CH(4) ). Confident reporting of trace gas emissions from mangrove sediments at local levels is important for regional emissions inventories, since small changes in N(2) O and CH(4) fluxes greatly influence greenhouse gas budgets due to their high global warming potentials. It is also important to identify the drivers of trace gas emission, to prioritize management for minimising emissions. We measured N(2) O and CH(4) fluxes and abiotic sediment parameters at midday low tide in winter and summer seasons, at four sites (27°33'S, 152°59'E) ranging from estuary to ocean sub-tropical mangrove sediments, having varied anthropogenic impacts. At all sites, sediment N(2) O and CH(4) emissions were significantly lower during winter (7-26 μg N(2) O m(-2) · h(-1); 47-466 μg CH(4) m(-2) · h(-1)) compared to summer (28-202 μg N(2) Om(-2) · h(-1); 247-1570 μg CH(4) m(-2) · h(-1)). Sediment temperature, ranging from 18 to 33°C, strongly influenced N(2) O and CH(4) emissions. Highest emissions (202 μg N(2) O m(-2) · h(-1), 1570 μg CH(4) m(-2) · h(-1) ) were detected at human-impacted estuary sites, which generally had higher total carbon (<8%) and total nitrogen (<0.4%) in sediments and reduced salinity (<16 dS · m(-1)). Large between-site variation highlights the need for regular monitoring of sub-tropical mangroves to capture short-lived, episodic N(2) O and CH(4) flux events that are affected by sediment biophysico-chemical conditions at site level. This is important, particularly at sites receiving anthropogenic nutrients, and that have variable freshwater inputs and tidal hydrology.     

Nitrous oxide production, its source and distribution in urine patches on grassland on peat soil

Urine patches are considered to be important sites for nitrous oxide (N₂O) production through nitrification and denitrification due to their high concentration of nitrogen (N). The aim of the present study was to determine the microbial source and size of production of N₂O in different zones of a urine patch on grassland on peat soil. Artificial urine was applied in elongated patches of 4.5 m. Four lateral zones were distinguished and sampled for four weeks using an intact soil core incubation method. Incubation of soil cores took place without any additions to the headspace to determine total N₂O production, with acetylene addition to determine total denitrification (N₂O+N₂), and with methyl fluoride to determine the N₂O produced through denitrification.Nitrous oxide production was largest in the centre and decreased towards the edge of the patch. Maximum N₂O production was about 50 mg N m^–2 d^–1 and maximum denitrification activity was 70 mg N m^–2 d^–1. Nitrification was the main N₂O producing process. Nitrous oxide production through denitrification was only of significance when denitrification activity was high. Total N loss through nitrification and denitrification over 31 days was 4.1 g N per patch which was 2.2% of the total applied urine-N.     

What plant functional traits can reduce nitrous oxide emissions from intensively managed grasslands?

Plant species exert a dominant control over the nitrogen (N) cycle of natural and managed grasslands. Although in intensively managed systems that receive large external N inputs the emission of the potent greenhouse gas nitrous oxide (N₂O) is a crucial component of this cycle, a mechanistic relationship between plant species and N₂O emissions has not yet been established. Here we use a plant functional trait approach to study the relation between plant species strategies and N₂O emissions from soils. Compared to species with conservative strategies, species with acquisitive strategies have higher N uptake when there is ample N in the soil, but also trigger N mineralization when soil N is limiting. Therefore, we hypothesized that (1) compared to conservative species, species with acquisitive traits reduce N₂O emissions after a high N addition; and (2) species with conservative traits have lower N₂O emissions than acquisitive plants if there is no high N addition. This was tested in a greenhouse experiment using monocultures of six grass species with differing above‐ and below‐ground traits, growing across a gradient of soil N availability. We found that acquisitive species reduced N₂O emissions at all levels of N availability, produced higher biomass and showed larger N uptake. As such, acquisitive species had 87% lower N₂O emissions per unit of N uptake than conservative species (p < .05). Structural equation modelling revealed that specific leaf area and root length density were key traits regulating the effects of plants on N₂O emission and biomass productivity. These results provide the first framework to understand the mechanisms through which plants modulate N₂O emissions, pointing the way to develop productive grasslands that contribute optimally to climate change mitigation.