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Abstract Alternative cropping systems are promoted to reduce nitrogen (N) losses in the environment and mitigate greenhouse gas (GHG) emissions. However, these supposed benefits are not fully known, rarely studied together and on the long-term. Here, we studied the N inputs, N exports, soil organic N (SON) storage, N leaching, gaseous N emissions and GHG balance in a 19-yr field experiment comparing four arable cropping systems without manure fertilization, under conventional (CON), low-input (LI), conservation agriculture (CA) and organic (ORG) managements. The N surplus, i.e. the difference between total N inputs and exports, was lowest in LI (43 kg ha−1 yr−1), intermediary for CON and ORG with 63 kg ha−1 yr−1 and highest in CA (163 kg ha−1 yr−1). CA and ORG received high amounts of N derived from biological fixation from alfalfa. The annual SON storage rates markedly differed between CA (55 kg ha−1 yr−1) and both CON and LI (13 and 6 kg ha−1 yr−1), with intermediary value in ORG (30 kg ha−1 yr−1). N leaching, calculated using soil mineral N measurements, reached an average of 21 kg ha−1 yr−1 and did not significantly differ between treatments. The gaseous N emissions (volatilization + denitrification), calculated as the difference between N surplus, SON storage and N leaching, ranged from 12 kg ha−1 yr−1 in ORG to 83 kg ha−1 yr−1 in CA. N 2 O emissions were continuously monitored with automatic chambers during 40 months. They varied from 1.20 kg ha−1 yr−1 in LI to 4.09 kg ha−1 yr−1 in CA system and were highly correlated with calculated gaseous N emissions. The GHG balance, calculated using SOC and N 2 O measurements, varied widely between systems: it was highest in CON and LI, with 2198 and 1763 kg CO 2eq ha−1 yr−1 respectively. In CA, the GHG balance was much more favourable (306 kg CO 2eq ha−1 yr−1), despite important N 2 O losses which partly offset the benefit of SOC storage. ORG was the system with the smallest GHG balance (−65 kg CO 2eq ha−1 yr−1), acting as a CO 2 sink in the long-term. Similar trends were observed when GHG was expressed per unit of N input or N exported. The N surplus alone was not a good indicator of the N fate in the four agricultural systems. Complementary predictors of N losses and GHG balance are required to obtain a true overview of the C and N environmental impacts of cropping systems. On an operational point of view, these results should lead to investigate the variability of the GHG emissions within each cropping system. Highlights • N fate and GHG balance were investigated in four arable cropping systems over 19 years. • Conventional (CON), low input (LI), conservation (CA) and organic (ORG) systems • N recovery ranked as ORG > LI > CON > CA and gaseous N losses in the opposite order. • CA system resulted both in high C and N storage in soil and high N 2 O emissions. • GHG balance ranked as CON > LI > CA > ORG, ORG being the most favourable system. [ABSTRACT FROM AUTHOR]

Nitrogen (N) starvation is commonly used in the microalgae industry to induce biosynthesis of value-added products, such as astaxanthin and triacylglycerols. Microalgal adaptation to N starvation not only has an effect on biomass yield but also relates to a topic of N storage and utilization. Here, we show that only 30 % of saturated N availability and 47 % of maximum protein content is necessary to maintain a chemostat of microalga Graesiella emersonii growing at 0.96 d−1. The additionally absorbed nitrogen are transformed mainly as proteins to maintain reserves in metabolic capacity, as demonstrated by the proteomic resources allocation analysis. Such intracellular nitrogen reserve can be considered as an advanced nitrogen storage and utilization strategy as it shows a highly efficient utilization of nitrogen resources in cells. The results allow us to identify kinetics of microalgal response to N availability that is basic to future metabolic engineering. • Biomass accumulation under nitrogen deficiency is observed in Graesiella emersonii. • Nitrogen are assimilated in excess under nitrogen sufficient conditions. • Excessively absorbed nitrogen are transformed as proteins to maintain metabolic reserves. • Nitrogen-reserving proteins reach striking 26 % of biomass dry weight. • Protein reserve is a more efficient nitrogen storage and utilization strategy. [ABSTRACT FROM AUTHOR]

The rhodophyte Gracilaria lemaneiformis plays a significant role in nitrogen (N) utilization as an economic macroalgae. However, very little is known about how G. lemaneiformis adapts to N deprivation. In this study, G. lemaneiformis were pre-cultured in artificial seawater with 50 μM inorganic N for 4 days and two groups were set after the pre-culture, N-deprived treatment with 0 μM N nutrient and N-replete control with 50 μM N nutrient. The response of G. lemaneiformis to N deprivation was analyzed at physiological, transcriptomic and proteomic levels. Physiologically, our data revealed that N depletion resulted in the increase of C/N ratio in a sustained period of N deprivation. Nitrogenous compounds were available in N depletion, including amino acids, phycoerythrin and soluble protein, but not DNA and chlorophyll-a. Furthermore, transcriptomic analysis underscored two major responses of G. lemaneiformis to N deprivation: 1) N assimilation pathway, PSII and PSI initially responded to N deprivation in 4 days, but declined sharply during the N deprivation; 2) Carbon fixation and glycolysis metabolism both rapidly recovered during a sustained period of N deprivation from strong repression of the first 2 days. Proteomics data indicated that electron-transfer proteins in the photosynthesis of G. lemaneiformis increased dramatically, but phycoerythrin protein decreased under N deprivation. However, GS protein and ribulose-bisphosphate carboxylase (RubisCO) protein remained stable. Therefore, this investigation revealed that the C-N metabolism was essential to survival under N deprivation. [ABSTRACT FROM AUTHOR]

To be economically and environmentally sound, the nitrogen (N) supply in orchards needs to be finely tuned according to crop needs. This requires knowledge of the amount and the dynamics of N uptake by roots and of its allocation. This paper reports two experiments, carried out on the same set of trees, in order to: 1) study the uptake dynamics of N derived from fertiliser (N dff ) and its allocation to tree organs and, 2) quantify its N remobilization in spring from storage organs to new growth. The study was carried out using field-grown adult orange trees (cv. Tarocco nucellare grafted on Troyer Citrange), one of the most important fruit tree crops in the Mediterranean area. Nitrogen was supplied as ammonium nitrate in 10 applications with equal doses evenly distributed from March to November 2009. Four groups of 5 trees each received 15 N-enriched N starting from March, July, September, and November, respectively, while they received unlabelled N in the remaining periods. The results show that trees absorbed roughly 30% of the fertiliser N. Fertiliser-N use efficiency (NUE) was generally low in spite of the fact that readily available N sources were regularly supplied and the trees were irrigated; the later the fertiliser N was supplied, the lower was the NUE. Uptake rate was rather constant from April to November, but relatively less N was partitioned to fruits when the fertiliser was supplied later in the season. Remobilization of N from one-year-old leaves provided more than 60% of the N required by shoots in spring. By the end of April, most of the N had already been transferred from storage to growing organs. We estimated that, during the vegetative season, trees absorbed 94 kg N ha −1 from the soil and half of this amount derived from fertiliser. Spring remobilisation of winter stored N contributed for additional 40 kg N ha −1 to the N needs. [ABSTRACT FROM AUTHOR]

Microalgal cells possess a vast diversity of subcellular structures and cytoplasmic inclusions differing in their morphology, functionality, and composition, some of them giving rise to distinct Raman spectral signatures allowing their identification, localization, and visualization in situ . Here, we show that certain Raman features observed in Raman spectra of microalgae can be unambiguously attributed to guanine microcrystals because they are clearly distinct from Raman fingerprints of closely related purine species. Using confocal Raman microscopy, we have localized crystalline guanine as a part of cellular inclusions in the chlorophyte Desmodesmus quadricauda and in the eustigmatophyte Trachydiscus minutus . We propose that this finding also explains the chemical nature of similar nitrogen-rich crystalline structures recently documented in a number of other chlorophyte species by energy-dispersive X-ray spectroscopy. To the best of our knowledge, this is the first Raman microscopy-based direct evidence of the presence of guanine microcrystalline inclusions within microalgal cells. We tentatively propose that the crystalline guanine serves as a very compact, long-term depot of nitrogen in microalgae. Simplicity of specimen preparation requiring no fixation, labeling, or staining of the cells predetermines Raman microscopy as a method of choice for more advanced studies of the physiological role of guanine particles, as well as other crystalline inclusions in situ within intact cells. [ABSTRACT FROM AUTHOR]

Grazing regime has an important effect on grassland ecosystem. however, the mechanisms how alpine meadow vegetation, soil quality responds to this management regime remain unclear. A short term field experiment (4–5 years) was conducted to quantify the impact of different grazing management regimes (fencing (NG), grazing rest in growing stage (RG), traditional grazing (TG) and continued grazing (CG)) on alpine meadow of the Qinghai-Tibet Plateau (QTP) and investigated vegetation structure, soil physicochemical properties, C and N storage regarding grazing regime, during two consecutive years: 2014 and 2015. Our results revealed that the above-, below-ground and litter biomass, plant coverage in NG were significantly higher than those in RG, TG and CG in 2014 and 2015. The NG significantly increased the diversity, evenness and richness indexes when compared to CG, while NG significantly decreased those indexes compared with RG. Meanwhile, litter biomass and plant coverage had no significant difference between RG and TG in 2014 and 2015, and the above- and below-ground biomass had no significant difference between RG and TG in 2014, but RG significantly increased the above- and below-ground biomass compared with TG in 2015. The NG, RG and TG sites all significantly improved the bulk density, soil compaction in 0–30 cm soil depth, available nitrogen and available potassium concentrations in 0–10 cm soil layer compared with CG site. NG, RG and TG all significantly increased the soil water content, total nitrogen, total phosphorus and available phosphorus in 0–30 cm soil depth compared with CG site. The C and N storage in vegetation, 0–40 cm soil depth and whole ecosystem were significantly increased in NG, RG and TG compared with CG in both years. Our results demonstrated that fencing is the most suitable grazing management regime on alpine meadow of the QTP. However, taking into account other factors such as: use and update of grassland resources, economic income stability of herdsmen, the grazing rest in the growing stage enable to promote the efficient use of grassland resources, maintaining alpine ecosystem and preventing it from further degradation or desertification is the best one. [ABSTRACT FROM AUTHOR]

Afforestation of degraded land is one of the principal strategies for preventing soil erosion and promoting ecosystem recovery in fragile regions, especially in rocky desertification areas. In China, millions of hectares of farmland have been converted into forest in order to arrest and reverse rocky desertification under the Grain for Green Program (GGP). This study evaluated implications of land-use change from annual maize cultivation to perennial Zanthoxylum bungeanum plantations (1-, 4-, 7-, and 10-year-old) in the karst region of Guizhou province, southwest China. The study analyses the variations of biomass and nitrogen (N) storages as well as N distributions in biomass components and soil depths. Results showed that the N content in components of Z. bungeanum ranged from 0.31% to 3.24% with a mean value of 1.75%, which was lower than that of maize (2.13%) in the same region. The biomass N storage measured for the maize cropland was 210.59 kg ha ⿿1 , while this value increased linearly with stand ages for the four Z. bungeanum plantations (0.94, 108.31, 212.20, and 262.12 kg ha ⿿1 , respectively). The average amount of soil N storage in the Z. bungeanum plantations (9.33 t ha ⿿1 ) was significantly lower than in the adjacent intensively managed maize cropland (10.04 t ha ⿿1 ). This is mainly due to long-term organic and inorganic fertilizer inputs in the farmland stage. Total ecosystem N storage averaged 10.25 t ha ⿿1 in the maize cropland, and 9.38, 9.82, 9.05, and 9.67 t ha ⿿1 in the 1-, 4-, 7- and 10-year-old Z. bungeanum plantations, respectively. Soils accounted for 97% of total ecosystem N storage in both land-use systems. This study suggests that the reduction of surface soil disturbance during plantation management practices plays a crucial role in improving the N storage. Data of annual plantation area and biomass N accumulation rates under the GGP indicate that Guizhou province was a net N sink with 2.35 ÿ 10 8 kg N in 2010, corresponding to 41.45% of N (NO X -N and NH 3 -N) emissions in that year. Besides increasing N sequestration over time (as these forest mature), the large-scale plantations of Z. bungeanum have the potential to restore severely degraded soils in the karst region of SW China. [ABSTRACT FROM AUTHOR]

Desertification is one of the most severe types of land degradation. This study quantified the impact of five different desertification regimes (potential (PD), light (LD), moderate (MD), severe (SD), and very severe (VSD)) on a desert steppe ecosystem in northern China, and investigated the changes in carbon (C) and nitrogen (N) storage in relation to land desertification. The C and N content in different stages of desertification were significantly different, while there was no obvious variation of C and N in different plant components as desertification progressed. Changes in soil C and N were not in accordance with plant succession, with the soil being more sensitive to desertification than the ground vegetation. When the VSD stage was compared with the PD stage, desertification resulted in the total C and N storage in plants decreasing by 97.3% and 96.8%, respectively, and in the 0–40 cm soil layer decreasing by 58.5%, and 76.0%, respectively. The highest C and N storage levels in the desert steppe ecosystem were 1291.93 g m −2 , and 142.10 g m −2 in the PD stage, and the lowest levels were 505.14 and 33.41 g m −2 in the VSD stage. C and N losses through desertification were 786.79 and 108.69 g m −2 , respectively. Therefore, it was confirmed that desertification results in soil degradation and seriously decreases soil potential productivity. [ABSTRACT FROM AUTHOR]

• Cyanophycin synthesis-degradation genes were found in 21 of 23 Raphidiopsis strains. • N fluctuation was the factor triggerring cyanophycin accumulation in R. raciborskii. • Proposed a N threshold determining the N substrate used for cyanophycin synthesis. • The first attempt to elucidate the role of stored N in cyanobacterial dominance. Nutrient storage is considered a critical strategy for algal species to adapt to a fluctuating nutrient supply. Luxury phosphorus (P) uptake into storage of polyphosphate extends the duration of cyanobacterial dominance and their blooms under P deficiency. However, it is unclear whether nitrogen (N) storage in the form of cyanophycin supports persistent cyanobacterial dominance or blooms in the tropics where N deficiency commonly occurs in summer. In this study, we examined genes for cyanophycin synthesis and degradation in Raphidiopsis raciborskii , a widespread and dominant cyanobacterium in tropical waters; and detected the cyanophycin accumulation under fluctuating N concentrations and its ecological role in the population dynamics of the species. The genes for cyanophycin synthesis (cphA) and degradation (cphB) were highly conserved in 21 out of 23 Raphidiopsis strains. This suggested that the synthesis and degradation of cyanophycin are evolutionarily conserved to support the proliferation of R. raciborskii in N-fluctuating and/or deficient conditions. Isotope 15N-NaNO 3 labeling experiments showed that R. raciborskii QDH7 always commenced to synthesize and accumulate cyanophycin under fluctuating N conditions, regardless of whether exogenous N was deficient. When the NO 3 −-N concentration exceeded 1.2 mg L−1, R. raciborskii synthesized cyanophycin primarily through uptake of 15N-NaNO 3. However, when the NO 3 −-N concentration was below 1.0 mg L−1, cyanophycin-based N was derived from unlabeled N 2 , as evidenced by increased dinitrogenase activity. Cells grown under NO 3 −- N < 1.0 mg L−1 had lower cyanophycin accumulation rates than cells grown under NO 3 −- N > 1.2 mg L−1. Our field investigation in a large tropical reservoir underscored the association between cyanophycin content and the population dynamics of R. raciborskii. The cyanophycin content was high in N-sufficient (NO 3 −- N > 0.45 mg L−1) periods, and decreased in N-deficient summer. In summer, R. raciborskii sustained a relatively high biomass and produced few heterocysts (< 1%). These findings indicated that cyanophycin-released N, rather than fixed N, supported persistent R. raciborskii blooms in N-deficient seasons. Our study suggests that the highly adaptive strategy in a N 2 -fixing cyanobacterial species makes mitigating its bloom more difficult than previously assumed. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Our main objective was to trace and to quantify the stabilization of nitrogen released from litter decomposition in different functional soil organic matter fractions. To identify the fate of nitrogen in a free-range experiment, 15N-labeled beech litter was deposited on the bare soil surface of three 2 m × 2 m plots on a Rendzic Leptosol under beech (Fagus sylvatica L.) with mull humus form near Tuttlingen (Swabian Jura, Germany). The 15N composition of bulk soil and soil fractions was monitored for three years by sampling the litter layer and the Ah horizon (0–5, 5–10 cm) after 140, 507, and 876 d. A combined density and particle size fractionation procedure allowed the isolation of different functional soil organic matter fractions: free light fraction, occluded organic matter, and organo-mineral associations. The first flush in the 15N enrichment was observed in the bulk soil within 140 d, due to plant debris transferred to the free light fraction by probably bioturbation and soluble compounds being leached from the litter directly to the clay fractions. The observed rates within the first 140 d indicated a quick transfer of 15N-enriched compounds from litter into the free light fraction, with a rate of 0.07 μg kg−1 d−1, and to the clay fractions, with a rate of 0.31 μg kg−1 d−1. In contrast, transfer to the occluded light fractions was delayed, with rates of 0.01 μg kg−1 d−1 (> 20 μm) and 0.001 μg kg−1 d−1 (< 20 μm), respectively. After 876 d, we recovered 9% of the added label in the 0–10 cm soil horizon, of which more than 4% was found in the organo-mineral fraction (0–5 cm), nearly 3% in the light fractions (0–5 cm), and another 2% unspecified in the bulk soil of 5–10 cm depth. We therefore conclude that the clay fractions act as the main sink for the recovered 15N. The rapid incorporation and the high preservation of 15N in the clay fractions revealed the dominant role of organo-mineral associations in the stabilization of nitrogen in the investigated soil. [Copyright &y& Elsevier]

Abstract: Frequently, improved plant genetics is viewed as the path to increased crop yields. However, in this manuscript, we argue that yield increases most often result from a combination of improved genetics and increased availability of nitrogen and water resources. At this time, it is likely that resource availability is the main impediment to yield increase in many cropping systems. In developing regions, it appears that nitrogen availability limits crop yield. In developed regions, rainfall and water availability commonly impose a substantial constraint on further crop yield increase. Strategies are examined to enhance resource accumulation and use in cropping systems of the future. [Copyright &y& Elsevier]

Abstract: The nitrogen absorption and desorption property of LaNi5 was investigated using NH3 and N2 as nitrogen sources. It was found that both as purchased and milling processed LaNi5 powder can absorb and desorb nitrogen using NH3 as the nitrogen source, while milled LaNi5 powder can absorb and desorb more. XRD, cross sectional SEM and EPMA were performed to elucidate the nitrogen stored phases. When N2 gas was used as the nitrogen source, it was found that the amount of absorbed nitrogen significantly decreased. By using high pressure for the absorption treatment or performing an activation treatment using hydrogen absorption/desorption before the nitrogen absorption treatment, milled LaNi5 was found to absorb nitrogen of 0.1mol/mol Finally, the mechanism of the nitrogen absorption was discussed from the EPMA and kinetic data of the nitrogen absorption, and it was suggested that the mechanism of the nitrogen absorption might be explained by a combined model of a diffusion controlled process and an interface controlled process. [Copyright &y& Elsevier]

Abstract: Mechanical alloying was performed on the Ca–Co system and the nitrogen storage property and magnetization were investigated. The solid solution of Co dissolving Ca is formed during MA process that has limited storage ability, while longer milling produces amorphous/nanocrystalline phase with the ability. The milled Ca–Co powder absorbed and desorbed more nitrogen than pure Ca and Co powder each separately milled and processed. The increase of Ca surface area mainly controls the storage property for short MA, while that for longer MA is ascribed to the non-equilibrium phase. The stored amount for Ca–Co powder increases with milling time, and its magnetization significantly decreased. The large reduction is explained by linear dilution of atomic moment based on the rigid band model, while the deviation from the model for longer MA is explained by formation of the non-equilibrium phase with limited magnetization but with nitrogen storage ability. [Copyright &y& Elsevier]

Abstract: Land use change can lead to changes in a range of soil properties, including soil carbon (C) and nitrogen (N) content, bulk density and pH. Previous investigations on the effects of land use change have been biased towards the impact of forest clearing and afforestation in tropical environments. Therefore, the aim of this study is to determine the impact of a conversion from cropland to grassland on soil properties in two districts of the Lahn-Dill Highlands, Germany. We determined a land use history for the period 1945–2004 from aerial photographs and field surveys. This land use history was used to build a chronosequence of grassland sites with a different age since the conversion from cropland for both districts. Each chronosequence was sampled to determine bulk density, pH, coarse material fraction, C/N ratio and soil C and N content as a function of grassland age. Results showed that there was no clear dependency of soil properties on grassland age for both districts. It was concluded that observed differences within each district are much more related to differences in soil parent material or slope position, instead of land use. Interestingly, the reduction of the chronosequence analysis to a paired site survey led to an opposite conclusion for the Erda district because all investigated soil properties were significantly different for continuous grassland and cropland. This indicates that care is required when interpreting results from paired site surveys, especially when the equality of initial soil conditions is not (or cannot be) tested. [Copyright &y& Elsevier]

Abstract: The type of land use and soil cultivation are important factors controlling organic carbon storage in soils and they may also change the relative importance of different mechanisms of soil organic matter stabilization. Our objectives were: i) to quantify the soil organic carbon (SOC) and nitrogen (N) storage in silty soils under wheat, maize, grassland and spruce, ii) to determine the SOC and N storage in water-stable aggregates of different size (&#60;53 μm, 53–250 μm, 250–1000 μm, 1000–2000 μm, >2000 μm) and in density fractions (Mineral-associated soil organic matter >2 g cm−3 (Mineral-SOM), free particulate organic matter &#60;1.6 g cm−3 (free POM), light occluded particulate organic matter &#60;1.6 g cm−3 (occluded POM&#60;1.6) and dense occluded particulate organic matter 1.6 to 2.0 g cm−3 (occluded POM1.6–2.0)) and iii) to analyse the stability and turnover of these SOC fractions in the maize soil on the basis of the δ13C values. Total SOC stocks down to a depth of 60 cm and including the humus layer were larger at the spruce site (10.3 kg C m−2) as compared with the grassland, wheat and maize (7 to 8 C kg m−2). However, SOC stocks in the mineral soil were smaller in the forest soil than in the agricultural soils. In the arable soils, the aggregate fractions 53–250 μm and 250–1000 μm were the most abundant size fractions, whereas aggregates >1000 μm were most abundant in the grassland and forest soil. The SOC concentration and the C/N ratio were greater for macroaggregates (>250 μm) than microaggregates (&#60;250 μm) in the field and grassland soils. At the maize site the percentage of maize-derived C was smallest in the fraction &#60;53 μm with 24% and steadily increased with increasing aggregate size to 47% in the fraction >1000 μm. The major part (86–91%) of the SOC was associated with the heavy mineral fraction at the grassland, maize and wheat site. In the A horizon of the spruce stand, the particulate organic matter accounted for 52% of the total SOC content. The C/N ratios of density fractions decreased in the order free POM&#60;1.6>occluded POM>Mineral-SOM for all soils and depths. The mean age of organic carbon in the water-stable aggregates in the Ap horizon of the maize site increased with decreasing aggregate size from 35 yr (>1000 μm) to 86 yr (&#60;53 μm). For the density fractions the order was free POM (22 yr)&#60;dense occluded POM1.6–2.0 (49 yr)&#60;Mineral-SOM (63 yr)&#60;light occluded POM&#60;1.6 (83 yr). The results showed that the type of land use affected the distribution pattern of litter carbon to functionally different SOM pools and that increasing SOC concentrations were closely associated with the formation of macroaggregates. [Copyright &y& Elsevier]

Abstract: Nitrogen absorption and desorption properties as well as possible formation of a non-equilibrium phase were investigated on Ca–Fe powder prepared by ball milling (BM) method. The milled Ca–Fe powder absorbed and desorbed more amount of nitrogen than pure Ca powder and pure Fe powder when each was separately milled and processed. The amount of nitrogen absorbed and desorbed by the Ca–Fe powder is increased with milling time and its magnetization significantly decreased. The large reduction in the magnetization is explained by formation of the non-equilibrium alloy phase in the Ca–Fe powder system, where the new phase is capable of absorbing and desorbing nitrogen and has its magnetization significantly less than pure Fe. [Copyright &y& Elsevier]

Nitrogen absorption and desorption characteristics on rare earth–iron intermetallic compounds, R2Fe17 and RFe7, were performed. These intermetallic compounds absorbed nitrogen into their crystal lattices by heating in NH3 or N2 gas at 573–773 K to form the interstitial-type metal nitrides. The nitrogen stored in the metal nitrides was reversibly released by a successive heat treatment in a stream of H2 gas at 523–723 K. The nitrogen absorption and desorption properties of RFe7 was superior to that of R2Fe17 because of the ease of nitrogen diffusion due to the difference of crystal structure between them. The nitrogen absorbed in the lattice of both compounds exists as an atomic state, so that the nitrogen desorbed from the compounds readily reacted with hydrogen to form ammonia during the nitrogen desorption. [Copyright &y& Elsevier]

Bananas (Musa acuminata Colla, Cavendish cv. ‘Williams’) were stored in nitrogen at 22 °C for 6, 12 and 24 h at a more green than yellow (stage 3) or more yellow than green (stage 4) ripening stage. Shelf life in nitrogen at 22 °C, that is the time taken from a more yellow than green colour stage 4 to yellow with slight brown flecking stage 7, was not extended when compared to air-stored bananas. However, areas of brown discolouration appeared on bananas placed in nitrogen-storage. The aroma of ripe bananas was assessed with a mass spectrometry-based chemical nose. Bananas stored in nitrogen generally had a riper aroma profile compared with air-storage. An ion with a mass to charge ratio of 61 was strongly associated with nitrogen-treated bananas; this ion is a decomposition product of a known banana aroma compound, ethyl acetate that produces an over-ripe banana note. An ion with a mass to charge ratio of 55 was associated with air-stored bananas; this ion is a decomposition product of ripe bananas (3-methylbutyl ester and 1-butanol). Post-climacteric nitrogen storage is not a suitable method for increasing shelf life, as it causes skin browning. [Copyright &y& Elsevier]

Nitrogen (N) is an essential element for plant growth and ecosystem productivity. Accurate estimation of N storage in terrestrial ecosystems is crucial because it is one of the most important N pools in the earth system; however, the spatial patterns of N storage and the main influencing factors remain unclear due to the limited data available, particularly on the N content in plant organs. Here we systematically estimated the N storage in China for the first time using 44,337 field-measured data. The total N storage was 10.43 Pg N, with 0.29 Pg N in vegetation and 10.14 Pg N in soil (0–100 cm); of these, approximately 62.07% (0.18 Pg N) of the vegetation N was stored in active plant organs (leaf and root). Furthermore, N storage in the forest, grassland, wetland, and cropland ecosystems (excluding vegetation) was 3.74, 3.15, 0.24, and 1.93 Pg N, respectively. The spatial patterns of N density were different in vegetation and soil. Redundancy analysis showed that the main factor influencing the spatial patterns in vegetation was climate, whereas the main factors influencing the spatial patterns in soil were climate and soil nutrient. Our study clarified the N pools of each subsystem (particularly for plant organs) and revealed the main influencing factors. In addition, we compiled N density datasets for different plant organs and soil depths across various climatic regions in China, which could provide parameters for regional N cycle models or serve as a reference for regional N management. Unlabelled Image • About 10.43 Pg N was synthesized in China's terrestrial ecosystems. • Vegetation and soil stored 0.29 Pg N and 10.14 Pg N, respectively • About 62.07% of vegetation N stored in active plant organs (leaf and root) • Climate regulated the spatial pattern of N storage in vegetation and soil. [ABSTRACT FROM AUTHOR]

Halophila stipulacea is a small tropical seagrass species native to the Red Sea. Due to its invasive character, there is growing interest in understanding its ability to thrive in a broad range of ecological niches. We studied temporal (February 2014 and July 2014), depth (5, 9, 18 m) and spatial (NB and SB) related dynamics of H. stipulacea meadows in the northern Gulf of Aqaba. We evaluated changes in density, morphometry, biomass, and biochemical parameters alongside the reproductive effort. In both sites, maximal growth and vegetative performance occurred in the summer with a marked increase of 35% in shoot density and 18% in biomass; PAR reduction with season and depth induced a significant increase of 28% in leaf area. Sexual reproduction efforts were only observed in July, and the density of plants carrying male or female flowers decreased significantly with depth. The favorable growth responses of H. stipulacea plants observed in the N-enriched NB site suggests their capacity to acclimate to human-disturbed nearshore environments. • H. stipulacea displayed contrasted responses to different environmental conditions. • Higher phenol contents were observed in SB than in NB in both seasons. • H. stipulacea plants positively acclimate to N-enriched marine systems. • Most detailed quantitative baseline data of native Halophila stipulacea populations. [ABSTRACT FROM AUTHOR]

Cyanobacteria are oxygenic phoautotrophs that can utilize inorganic nitrogen salts, atmospheric nitrogen and some amino acids such as arginine as nitrogen source. Under unbalanced growth in the presence of sufficient nitrogen, many cyanobacteria accumulate cyanophycin, a co-polymer of aspartate and arginine that serves as a nitrogen reservoir. Cyanophycin metabolism enzymes include cyanophycin synthetases, cyanophycinase and isoaspartyl dipeptidase. The latter splits β‑aspartyl arginine released from cyanophycin by cyanophycinase into aspartate and arginine. The arginine catabolic pathway of cyanobacteria has been recently elucidated and consists of two bifunctional enzymes, arginine-guanidine removing enzyme (AgrE) and proline oxidase (PutA). This pathway makes available to metabolism the four nitrogen atoms of arginine, three as ammonia and one as glutamate. A variant of the pathway cycles ornithine (an intermediate in the AgrE-catalyzed reactions) back to arginine incorporating aspartate and, hence, recovering its nitrogen atom for metabolism. Many cyanobacteria also make use of this pathway to utilize arginine taken up from the outer medium through a high-affinity ABC transporter. An analysis of co-occurrence in cyanobacteria of genes encoding cyanophycin metabolism and arginine catabolism enzymes and arginine and aspartate transporters indicates a strong correlation between the presence of cyanophycin and the AgrE/PutA pathway. • Cyanobacteria accumulate cyanophycin (a poly-aspartate-arginine material) under unbalanced growth with sufficient nitrogen. • Cyanophycin serves as a transient storage of nitrogen that is very relevant in the fixation of atmospheric nitrogen. • Cyanophycin is synthesized non-ribosomally and degraded stepwise producing free aspartate and arginine. • The arginine catabolic pathway consists of two bifunctional enzymes (AgrE and PutA) that provide nitrogen to metabolism. [ABSTRACT FROM AUTHOR]