Stoichiometric Relationship Research Articles

N:P:S stoichiometry in grains and physiological attributes associated with grain yield in maize as affected by phosphorus and sulfur nutrition

Balanced nutrition is necessary to reduce yield gaps in maize. Simultaneous phosphorus (P) and sulfur (S) deficiencies may be present in soils, so a P×S interaction is expected. In maize, yield is closely related to grain number (GN); thus, nutrient deficiencies impacting crop growth during GN formation can consequently impact yields. Grain nutrient concentration may reflect soil supplying capacity, and nutrient stoichiometry in grains can be used as an indirect indicator of nutrient deficiency for a retrospective diagnosis of sites responsive to P or S fertilization. The objectives of this study were to: i) determine maize response to increasing S fertilizer rates and to P addition; ii) analyze the effects of P, S, and their interaction on mechanisms involved in yield determination of maize; and iii) evaluate the effects of P and S shortage on stoichiometric relationships among N, P, and S content in maize grains. Two fertilization experiments were conducted on-farming conditions in 19 sites-year (SY) for analyzing grain yield response to increasing S fertilizer rates (E1), and studying the interaction between P and S fertilization on grain yield and physiological attributes associated with grain yield determination (E2), i.e. CGRCP, IPARCP, RUECP and biomass at R6. Also N (%N), S (%S) and P (%P) concentration in grains were determined. Stoichiometric relationships among N, P and S in both P or S fertilized and unfertilized treatments in all SY were analyzed. Average grain yield response due to S and P addition was ca. 13 and 20%, respectively. Grain yield increased up to S fertilizer rates around 10kgSha−1. P addition increased CGRCP by 15–60% in 8 SY while S addition 12–16% in 2 SY. Both, RUECP and IPARCP were positively associated with biomass production. P fertilization increased IPARCP by 4%, but no S effect was observed. Before silking, P addition boosted cumulated radiation by 7%, but after silking no P or S effects were observed. A significant P×S interaction was observed for RUECP, since S fertilization increased RUECP by 14% only when P was not added. Independently of P or S shortage, grain N content scaled almost isometrically with grain S content, while N:P and P:S showed allometric relationships. Phosphorus deficiency did not modify N:S, N:P nor P:S stoichiometry. Likewise, S addition did not modify the N:P or N:S stoichiometry. A significant change in the intercept of the P:S relationship was observed in response to fertilization and may be used as a tool for identifying S responsive sites using grain nutrient analysis.

Age-related changes of leaf traits and stoichiometry in an alpine shrub (Rhododendron agglutinatum) along altitudinal gradient

Leaf morphological and stoichiometric characteristics are considered to represent both the interior inheritable characters in the plant and its adaptations to specific exterior environments. Rhododendron agglutinatum, an evergreen alpine shrub species, occupies a wide range of habitats above timberline in the Miyaluo Natural Reserve, southwestern China. Along an altitudinal gradient ranging from 3700 to 4150 m, we measured leaf morphological characters including leaf dry matter content (LDMC), leaf dry mass per unit area (LMA), and one leaf area (OLA), as well as carbon (C) and nutrient (N, P) contents in leaves of three different age groups (juvenile leaves, mature leaves and senescent leaves). We also calculated the stoichiometric relationships among carbon and nutrients (C/N, C/P and N/P). Results showed that both age and altitude affected the leaf morphological and stoichiometric properties of R. agglutinatum. Mature leaves possessed the highest LDMC, LMA and C contents both on a dry mass basis and on a unit area basis. Younger leaves possessed higher contents of nutrients. OLA as well as ratios between carbon and nutrients (C/N, C/P) increased with ages. Juvenile leaves possessed lowest ratio between nitrogen and phosphorus. In juvenile leaves, nutrients increased with altitudinal elevation, whereas other traits decreased. In mature leaves, nutrients and their ratios with carbon showed consistent trends with juvenile leaves along increasing altitude, whereas LMA and carbon on a unit area basis showed opposite trends with juvenile leaves along increasing altitude. In senescent leaves, only content of phosphorus on a unit area basis and N/P were found linearly correlated with altitude. Our results demonstrated a clear pattern of nutrient distribution with aging process in leaves and indicated that a high possibility of N limitation in this region. We also concluded that younger leaves could be more sensitive to climate changes due to a greater altitudinal influence on the leaf traits in younger leaves than those in elder leaves.

Ecological stoichiometric characteristics of plants and soil in grassland under different restoration types in Yunwu Mountain, China

Carbon (C), nitrogen (N) and phosphorus (P) stoichiometry from the aboveground parts of plants, roots, plant litter and soils, as well as their relationships were studied in grassland under four distinct types of vegetation recovery including natural grassland, grassland with shrubs, grassland after grazing exclusion, and abandoned cropland in Yunwu Mountain, China. The results showed that there was significant correlation among the ecological stoichiometric characteristics of soils with the aboveground parts and roots. The relation between the aboveground parts and roots was closer in P concentration than in N concentration. The linkage of plants and soils was closer in N concentration than in P concentration. The ecological stoichiometric relationships between soils and litter as well as between roots and litter were weak. There was no significant difference between the aboveground parts and roots in total C and N storages among four distinct recovery methods. How-ever, the P storage differed greatly among the four recovery types with the maximum of 0.49 g·m-2 in the abandoned cropland and the minimum value of 0.29 g·m-2 in the grassland after grazing exclusion. Grazing prohibition duration had minor effects on ecological stoichiometric characteristics. The 12-year-abandoned cropland had lower soil organic C and total N concentration (9.98 and 1.07 g·kg-1, respectively) compared with natural grasslands (14.27 and 1.55 g·kg-1, respectively), and this difference of ecological stoichiometric characteristics was caused by the high P concentration in abandoned cropland. The roots N and P concentrations were the lowest in natural grassland with 6.25 and 0.57 g·kg-1, respectively, due to the greatest amount of root biomass. The N and P concentrations in the grassland with shrubs were relatively lower in the aboveground parts(12.77 and 0.98 g·kg-1,respectively) while relatively higher in roots (9.30 and 0.77 g·kg-1, respectively). Overall, the plant composition was the key factor that influenced the ecological stoichiome-tric characteristics of plant communities. The distinctions of the ecological stoichiometric characteristics among different restoration types decreased with the increasing Sorensen index.

El Inventario Ecológico y Forestal de Cataluña: una herramienta para la ecologíafuncional

Vayreda, J., Martínez-Vilalta, J., Vilà-Cabrera, A.. 2016. The Ecological Forest Inventory of Catalonia: a tool for functional ecology. Ecosistemas 25(3): 70-79. Doi.: 10.7818/ECOS.2016.25-3.08 This paper describes the particular characteristics of IEFC that makes it singular unique tool for the advance of forest ecological understanding. The IEFC stressed by sampling uncommon variables such as biomass and production of branches and leaves, growth curves or nutrient content in wood, bark, branches and leaves. This additional information allowed to carry out some functional studies. In this paper we briefly review the most relevant results regarding: i) the geographical distribution of functional traits across levels of organization and intraspecific and interspecific variability along environmental gradients; ii) the positive relationship between species richness and timber production in Mediterranean forests; iii) the trend to higher growth during most of the twentieth century reversed from year 1970 by lower water availability and; iv) stoichiometric relationships of nutrients by species and functional groups along environmental gradients. Today it is clear that the inclusion of these functional variables in a forest inventory is essential to better understand forest responses to environmental changes and evaluate the suitability of different management strategies.

Effects of stratification, organic matter remineralization and bathymetry on summertime oxygen distribution in the Bohai Sea, China

The Bohai Sea, a semi-enclosed shallow coastal sea with increasing nutrient loads, is susceptible to seasonal oxygen deficiency in its bottom waters, similar to many other areas of the worlds’ coastal oceans. We examined the dissolved oxygen (DO) distribution in the Bohai during August 2014. Two oxygen-deficient zones (DO<92μmol O2kg−1) with a minimum DO of ~80μmol O2kg−1 were documented. The area and volume of bottom oxygen-deficient water were ~756km2 and 7820×106 m3, with a mean thickness of ~10m. Thus, the Bohai is second to the Changjiang estuary in its oxygen-deficient zone size among China’s coastal waters. We classified three hydrographic areas that dictated the distribution of DO: 1) the shallow well-mixed zone; 2) the laterally-open stratified zone; and 3) the isolated stratified zone. Vertical mixing dominated the shallow well-mixed zone leading to homogeneous DO in the water column. The laterally-open stratified zone was influenced by high DO and low temperature inflow through the northern Bohai Strait. The isolated stratified zones, i.e., the low DO areas, were found in depressed regions. The stoichiometric relationship between DO consumption and the corresponding enrichment of dissolved inorganic carbon suggested that the aerobic respiration of organic matter contributed to the oxygen-depletion in the isolated stratified zone. Overall, the bottom DO distribution in the Bohai system was controlled largely by lateral DO exchange modified by bathymetric features, while superimposed on that was the build-up of stratification caused by summer heating and the remineralization of organics sourced from spring phytoplankton bloom.

Synthesis and characterization of nanoparticles of CZTSe by microwave-assited chemical synthesis

In this study we present the synthesis of Cu2ZnSnSe4 (CZTSe) nanoparticles by microwave-assisted chemical synthesis employing organic solvents. The effect of reaction time, reactant concentration, solvent and additives (inorganic material) was studied on the structural and optical properties of the nanomaterials. The powder samples were analyzed by x-ray diffraction, Raman spectroscopy, x-ray energy dispersive spectroscopy and x-ray photoelectron spectroscopy. The results show that the synthesis performed with triethanolamine and deionized water is better than others solvents, producing nanocrystals of quaternary phase (CZTSe) with stoichiometric relations similar to the reported research in the literature, which falls in the range of Cu/(Zn+Sn): 0.8–1.0, Zn/Sn: 1.0–1.20. The nanoparticles of CZTSe synthesized in this study present desirable properties in order to use them in solar cell and photoelectrochemical cell applications.

Mercury Stoichiometric Relationships in a Subtropical Peatland

Spatially variable areas, or hotspots, of elevated mercury (Hg) concentrations in soil, water, and wildlife occur throughout the Everglades wetland ecosystem. This study investigates the stoichiometric controls of Hg relative to soil, water, and biotic components. Surface water, porewater, soil, periphyton, and Gambusia spp. (mosquitofish) were collected from hotspots and non-spot stations and analyzed for various parameters, including total mercury (THg), organic carbon (OC), total carbon (TC), total phosphorus (TP), and total nitrogen (TN) between late 2010 and early 2013. Soil nutrient ratios were significantly different between hotspot and non-hotspot stations, indicating a difference in trophic status and position along the decay continuum or differences in limiting nutrients. Overall, soil total Hg concentrations were negatively correlated with soil TC/TN, while soil TC/TP and soil TN/TP molar ratios and soil THg were negatively correlated at hotspot stations. Meanwhile, mosquitofish THg was negatively correlated with soil TC/TN molar ratio and positively correlated with soil TC/TP and TN/TP molar ratios, suggesting trophic truncation. Soil, surface water, and porewater THg, TC, and OC interactions resulted in significant differences between hotspot and non-hotspot stations and between molar ratios of C, N, and P. Periphyton-surface water THg/OC homeostasis and soil nutrient ratios significantly explained mosquitofish THg concentrations, further indicating a trophic influence on mosquitofish THg and potential hotspot dynamics. Several factors and processes including bottom-up trophic interaction and vegetation influence on Hg accumulation dynamics and food-chain length explain the development and persistence of Hg hotspot formation within the Everglades system.

Apparent Quantum Efficiency Spectra for Superoxide Photoproduction and Its Formation of Hydrogen Peroxide in Natural Waters

Superoxide (O2−) is a key intermediate in the cycling of organic matter and trace metals in natural waters but production rates are difficult to determine due to low steady-state concentrations, rapid decay rates, and unstable standards. On the other hand, superoxide’s dismutation product, hydrogen peroxide (H2O2), is relatively stable in filtered water. Thus, if the stoichiometry between O2− and H2O2 is known, one can derive superoxide data from H2O2 measurements. The relationship between O2− and H2O2 remains uncertain in seawater but work by Petasne and Zika (1987) presented a method for examining the relationship between O2− and H2O2 during irradiations of coastal seawater using superoxide dismutase (SOD), which forces a 2:1 stoichiometry between O2− and H2O2. Here we report the first O2− apparent quantum yield (AQY) spectra following their approach; performing irradiations of various fresh and seawater samples and measuring H2O2 accumulation with and without added SOD. For all but a single riverine sample, H2O2 AQY spectra fell in a narrow range, but O2− AQY spectra varied such that O2−:H2O2 ratios were always greater than 2 and were highest for the clear waters of the Gulf Stream (~3.4 O2− per H2O2 generated). Because this approach eliminates the need to measure O2− production rates directly, it represents a simple way to refine the stoichiometric relationships that would potentially allow global estimates of O2− photoproduction rates, O2− steady-state concentrations ([O2−]ss), and related surface ocean redox reactions based on more manageable H2O2 photochemical studies.

Romul_Hum—A model of soil organic matter formation coupling with soil biota activity. II. Parameterisation of the soil food web biota activity

A soil food web (FW) based approach to modelling the contribution of soil micro- and mesofauna to the formation of soil organic matter (SOM) was developed as an improvement to the soil organic matter model ROMUL, which is the predecessor of Romul_Hum. The main improvement is that the by-products (excrement and necromass) of soil micro- and mesofauna, and their important role as precursors to formation of stable SOM, that are not represented in any soil organic matter model, are now included in the Romul_Hum. First, parameters were compiled to explicitly and mechanistically model the foundational role of microbial communities in the soil FW by using a substrate C:N ratio based function that allows (a) the fungal to bacterial biomass ratio to vary from 3 to 15, (b) fungal C:N to vary from 8 to 30, and (c) bacterial C:N to vary from 5 to 8. These equations were used in model algorithms instead of fixed values that are used in the SOM models. Second, ordination was used on 15 published FWs biomass C datasets to define six FW patterns as combinations of two energy channels (fungal and bacterial) and three types of soil horizons (L, F+H, Ah or Ahe) in temperate and boreal forests. Third, FW analysis methods were used to quantify excrement and necromass C produced by soil micro- and mesofauna at different trophic levels. Soil heterotrophic respiration (expressed as the rate of SOM mineralisation), a core rate variable in all SOM models, was associated with the formation of the faunal by-products (excrement and necromass) using stoichiometric relationships between the production of faunal excrement, necromass and total FW biotic respiration. The ratios of “excrement mass/necromass C to soil heterotrophic respiration C” were key parameters incorporated into the Romul_Hum. The values of these ratios vary from 0.03 to 0.41 for the bacterial energy channels (with maximum in the F+H soil horizon) and from 0.02 to 0.17 in fungal energy channels (wih maximum in the Ah/Ahe soil horizon). The well established mechanistic algorithm for available nitrogen (N) of the FW methodology was used to develop functions for the “ratio of available N to heterotrophic respiration C” depending on substrate C:N ranging from 5 to 120. The resulting algorithms, functions and new parameters for excrement and necromass production, as well as parameterisation of available N production, are described for all six FW patterns. The newly developed FW module was incorporated in the simulation model of SOM formation, Romul_Hum, allowing for the calculation of faunal organic matter contributions to SOM formation. This novel approach to including soil faunal activity in modelling of soil C dynamics takes advanatage of the high degree of organisation within soil biotic communities in FWs and integrates the effects of microorganisms and soil fauna that govern the processes of organic residues transformation and mineralisation in the soil system.

Soil enzyme activity and stoichiometry in forest ecosystems along the North-South Transect in eastern China (NSTEC)

Soil enzymes, as indicators of microbial metabolism, play an important role in nutrient biogeochemistry at the ecosystem level. In this study, we present information from a comprehensive analysis of the latitudinal variations in, and stoichiometric relationships between, soil β-glucosidase (BG), N-acetylglucosaminidase (NAG), leucine aminopeptidase (LAP), and acid phosphatase (AP) in nine forest ecosystems along the North-South Transect in eastern China. The results showed that soil BG and NAG activities were higher in temperate forests than in subtropical and tropical forests. Soil AP activities were the opposite, which indicates that microbial nutrient demand in tropical forests was limited by the nutrient phosphorus (P). Soil BG and NAG activities were significantly and negatively correlated with mean annual temperature (MAT), mean annual precipitation (MAP), the soil carbon (C):P and soil nitrogen (N):P ratios, but not with the soil C:N ratio. Soil NAG and AP activities were inversely correlated with soil pH, and soil AP activity increased as soil pH decreased. The latitudinal variations in the C:N, C:P, and N:P acquisition ratios represented by ln(BG):ln(LAP + NAG):ln(AP) activities across ecosystems were significantly and negatively related to MAP and MAT. The C:P and N:P acquisition ratios were positively related to soil pH but negatively related to the soil C:P and N:P ratios. The C:N and C:P acquisition ratios were also negatively correlated with leaf C:N, C:P, and N:P ratios. This study provides useful information about environmental controls on enzyme stoichiometry, and also highlights the stoichiometric and energy limitations on the metabolism of soil microbes.

Impact of MicroRNA Levels, Target-Site Complementarity, and Cooperativity on Competing Endogenous RNA-Regulated Gene Expression

SummaryExpression changes of competing endogenous RNAs (ceRNAs) have been proposed to influence microRNA (miRNA) activity and thereby regulate other transcripts containing miRNA-binding sites. Here, we find that although miRNA levels define the extent of repression, they have little effect on the magnitude of the ceRNA expression change required to observe derepression. Canonical 6-nt sites, which typically mediate modest repression, can nonetheless compete for miRNA binding, with potency ∼20% of that observed for canonical 8-nt sites. In aggregate, low-affinity/background sites also contribute to competition. Sites with extensive additional complementarity can appear as more potent, but only because they induce miRNA degradation. Cooperative binding of proximal sites for the same or different miRNAs does increase potency. These results provide quantitative insights into the stoichiometric relationship between miRNAs and target abundance, target-site spacing, and affinity requirements for ceRNA-mediated gene regulation, and the unusual circumstances in which ceRNA-mediated gene regulation might be observed.

Optimization of Ultrasound-Induced Microalgal Lipid Recovery

<abstract> <b><sc>Abstract.</sc></b> The objective of this work was to optimize the operating parameters of ultrasound for inducing cell disruption and lipid recovery of a marine alga (). Based on response surface methodology (RSM) experiments, a second-order polynomial model was developed to examine the effects of sonication duration (SD), power input (PI), and cell concentration (CC) on Nile red stained lipid fluorescence density (NRSLFD) per cell. The results showed that there was a positive stoichiometric relationship between SD and PI, but negative correlations existed between SD and CC and between PI and CC, suggesting that low CC was desirable for increasing NRSLFD per cell. The predicted maximum NRSLFD per cell was 1.25 x 10^-4, which was in close agreement with the measured NRSLFD of 1.15 x 10^-4 at SD of 3.42 min, PI of 364Â W, and CC of 1.20 x 10⁷ cells mL^-1. In addition, the recoverable crude lipids at the predicted optimal conditions for maximum NRSLFD per cell accounted for 74.5% of total lipid content. Long-chain and unsaturated lipids were degraded into short-chain and saturated lipids with ultrasonic cavitation.

Flame kernel formation behaviors in close dual-point laser breakdown spark ignition for lean methane/air mixtures

Ignition behaviors of close dual-point laser breakdown spark ignition were investigated experimentally for methane/air mixtures at 0.1 and 1.0MPa in a constant volume combustion vessel. Absorbed energy was measured from the difference between incident and transmitted laser rays using two joule meters as the ignition energy, and the behaviors of the initial flame kernel were observed with Schlieren photography using a high-speed video camera. First, the ignition behaviors of a single-point laser breakdown spark ignition were investigated. The results indicated that the effect of the focusing lens on the minimum ignition energy (MIE) was limited in terms of the absorbed energy. Although the MIE at 1.0MPa was lower than that at 0.1MPa near the stoichiometric equivalence relationship was reversed near the lean limit. For lean mixtures, local quenching of the initial flame kernel was clearly observed including third lobe region especially at 1.0MPa. In the case of the close dual-point sparks for an equivalence ratio of 0.6, formation of a third lobe was suppressed. When the dual spark gap was large, two flame kernels were formed as observed in the case of the single spark. An optimal gap in which the absorbed energy was minimal for successful ignition existed depending on the pressure, although the magnitude of the associated energy was not so different from that in the case of the single spark. However, the growth rate of the initial flame kernel formed by the close dual sparks was considerably higher than that formed by the single spark, especially at 1.0MPa. Enhancement of the flame kernel development due to the close dual spark was clearly observed.

Changes in stoichiometry of soil carbon, nitrogen and phosphorus in the early stage of temperate forest succession in Maoershan, Northeast China

A soil displacement experiment was established in the Maoershan Forest Ecosystem Research Station in 2004, replacing the cropland soil of the 0-30 cm depth with the eluvial horizon soil (A treatment), the sediment horizon soil (B treatment) and the parent material horizon soil (weathered sand, C treatment) of an adjacent temperate broadleaved stand. The three treatments simulated the secondary successions from forest clear-cutting, bare soil without seed bank, and primary succession, respectively. Changes in soil carbon, nitrogen, phosphorus and their stoichiometry were examined in 2014. The results indicated that during the ten-year succession, the contents of soil C, N and P changed insignificantly in the A treatment. The contents of soil C and N decreased by 34.7% and 38.6% in the B treatment, but increased by 63.4% and 198.4% in the C treatment, respectively. The slope of the log-transformed N-C relationships decreased significantly during the succession, while the slope of the log-transformed P-N relationships increased significantly. After 10-year's succession, only the C:N decreased by 44.5%, and the N:P increased by 283.6% in the C treatment, with no significant changes for others. The contents of C, N and P were significantly correlated with the root biomass and necromass, suggesting that the succession might change the soil elements and their stoichiometric relationships through modifying organic matter inputs.

The C:N:P:S stoichiometry of soil organic matter.

The formation and turnover of soil organic matter (SOM) includes the biogeochemical processing of the macronutrient elements nitrogen (N), phosphorus (P) and sulphur (S), which alters their stoichiometric relationships to carbon (C) and to each other. We sought patterns among soil organic C, N, P and S in data for c. 2000 globally distributed soil samples, covering all soil horizons. For non-peat soils, strong negative correlations (p < 0.001) were found between N:C, P:C and S:C ratios and % organic carbon (OC), showing that SOM of soils with low OC concentrations (high in mineral matter) is rich in N, P and S. The results can be described approximately with a simple mixing model in which nutrient-poor SOM (NPSOM) has N:C, P:C and S:C ratios of 0.039, 0.0011 and 0.0054, while nutrient-rich SOM (NRSOM) has corresponding ratios of 0.12, 0.016 and 0.016, so that P is especially enriched in NRSOM compared to NPSOM. The trends hold across a range of ecosystems, for topsoils, including O horizons, and subsoils, and across different soil classes. The major exception is that tropical soils tend to have low P:C ratios especially at low N:C. We suggest that NRSOM comprises compounds selected by their strong adsorption to mineral matter. The stoichiometric patterns established here offer a new quantitative framework for SOM classification and characterisation, and provide important constraints to dynamic soil and ecosystem models of carbon turnover and nutrient dynamics.Electronic supplementary materialThe online version of this article (doi:10.1007/s10533-016-0247-z) contains supplementary material, which is available to authorized users.

Computational Flux Balance Analysis Predicts that Stimulation of Energy Metabolism in Astrocytes and their Metabolic Interactions with Neurons Depend on Uptake of K+ Rather than Glutamate

Brain activity involves essential functional and metabolic interactions between neurons and astrocytes. The importance of astrocytic functions to neuronal signaling is supported by many experiments reporting high rates of energy consumption and oxidative metabolism in these glial cells. In the brain, almost all energy is consumed by the Na+/K+ ATPase, which hydrolyzes 1 ATP to move 3 Na+ outside and 2 K+ inside the cells. Astrocytes are commonly thought to be primarily involved in transmitter glutamate cycling, a mechanism that however only accounts for few % of brain energy utilization. In order to examine the participation of astrocytic energy metabolism in brain ion homeostasis, here we attempted to devise a simple stoichiometric relation linking glutamatergic neurotransmission to Na+ and K+ ionic currents. To this end, we took into account ion pumps and voltage/ligand-gated channels using the stoichiometry derived from available energy budget for neocortical signaling and incorporated this stoichiometric relation into a computational metabolic model of neuron-astrocyte interactions. We aimed at reproducing the experimental observations about rates of metabolic pathways obtained by 13C-NMR spectroscopy in rodent brain. When simulated data matched experiments as well as biophysical calculations, the stoichiometry for voltage/ligand-gated Na+ and K+ fluxes generated by neuronal activity was close to a 1:1 relationship, and specifically 63/58 Na+/K+ ions per glutamate released. We found that astrocytes are stimulated by the extracellular K+ exiting neurons in excess of the 3/2 Na+/K+ ratio underlying Na+/K+ ATPase-catalyzed reaction. Analysis of correlations between neuronal and astrocytic processes indicated that astrocytic K+ uptake, but not astrocytic Na+-coupled glutamate uptake, is instrumental for the establishment of neuron-astrocytic metabolic partnership. Our results emphasize the importance of K+ in stimulating the activation of astrocytes, which is relevant to the understanding of brain activity and energy metabolism at the cellular level.

Synthesis of an elastic β‐cyclodextrin hydrogel cage by hydroxyethyl cellulose

ABSTRACTCurrent cyclodextrin (CD) hydrogels have disadvantages, including a limited CD content, long reaction time, and complicated chemical reactions. To overcome these, a one‐pot reaction was adopted, and a concept of a β‐CD hydrogel cage was proposed. Hydroxyethyl cellulose (HEC) was used as the raw material with the adjustment of the stoichiometric relationship among the crosslinking agent of epichlorohydrin, alkali environment, and β‐CD amount, and an elastic β‐CD hydrogel cage system was established. After the β‐CD was caged, the contents of active β‐CD in hydrogel products reached 74.45 and 69.14 wt % by weight measurement and photometric titration, respectively. Furthermore, compared to the pure HEC hydrogel, the hydrogel mechanical strength improved obviously after the β‐CD was caged, and we obtained a faster water swelling rate at the same time. Finally, a hydrophobic molecule of phenolphthalein (PP) was used to evaluated the activity of caged β‐CD in the hydrogel. In addition, the absorption and release of PP by an elastic β‐CD hydrogel cage at certain time intervals were also studied. The results demonstrate that the β‐CD hydrogel cage was used as a functional molecule carrier to quickly absorb and sustain the release of PP. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44388.

Impact of glyphosate-resistant corn, glyphosate applications and tillage on soil nutrient ratios, exoenzyme activities and nutrient acquisition ratios.

We report results of the last two years of a 7 year field experiment designed to test the null hypothesis: applications of glyphosate on glyphosate-resistant (GR) and non-resistant (non-GR) corn (Zea mays L.) under conventional tillage and no-till would have no effect on soil exoenzymes and microbial activity. Bulk soil (BS) and rhizosphere soil (RS) macronutrient ratios were not affected by either GR or non-GR corn, or glyphosate applications. Differences observed between exoenzyme activities were associated with tillage rather than glyphosate applications. In 2013, nutrient acquisition ratios for bulk and rhizosphere soils indicated P limitations, but sufficient assimilable N. In 2014, P limitations were observed for bulk and rhizosphere soils, in contrast to balanced C and N acquisition ratios in rhizosphere soils. Stoichiometric relationships indicated few differences between glyphosate and non-glyphosate treatments. Negative correlations between C:P and N:P nutrient ratios and nutrient acquisition ratios underscored the inverse relation between soil nutrient status and microbial community exoenzyme activities. Inconsistent relationships between microbial community metabolic activity and exoenzyme activity indicated an ephemeral effect of glyphosate on BS exoenzyme activity. Except for ephemeral effects, glyphosate applications appeared not to affect the function of the BS and RS exoenzymes under conventional tillage or no-till. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Romul_Hum model of soil organic matter formation coupled with soil biota activity. I. Problem formulation, model description, and testing

For many decades in the late 20th century, the processes involved in the formation of soil organic matter (SOM) (also known as humification) constituted one of the most important areas of scientific inquiry in soil science. However, these processes have not been included in modern models of SOM dynamics, despite their relevance to quantifying carbon stabilisation (i.e., sequestration) in soil. Furthermore, modern models have focussed on mineralisation processes (e.g., mainly microbial heterotrophic respiration) and have not included the important effects of soil fauna that are known as key agents of SOM formation. To address these issues, we developed a modelling approach predicated on the existence of definable stoichiometric relations among the processes leading to SOM formation that are mediated by soil biota (e.g., correlations among biotic respiration, production of faunal excrement, and necromass as sources of SOM formation). Soil respiration, a core rate variable in all SOM models, was associated with the production of faunal by-products in soil food webs as precursors of stable SOM, specifically micro- and meso-faunal excrement, necromass, and earthworm casts. We developed a food-web based module, using a synthesis of decades of published data, to describe micro- and meso-faunal excrement and necromass production. We developed a separate module for anecic earthworms, with explicit representation of processes related to fresh casts. The contributions of these two modules were compiled and integrated with the ROMUL model of SOM dynamics, without changing the structure of the original model. These modules enabled calculation of the proportional contribution of faunal by-products to humification (i.e., recalcitrant SOM formation) and carbon sequestration. Testing of the new version of the model, known as Romul_Hum, showed consistent accumulation of faunal by-products in the “final” SOM fractions: the well-decomposed SOM of the organic soil horizons and the stable SOM of the mineral soil.

Reduction kinetics of lanthanum ferrite perovskite for the production of synthesis gas by chemical-looping methane reforming

The reduction kinetics of LaFeO3 oxygen carrier for the production of synthesis gas by chemical-looping methane reforming (CLMR) is investigated in the present work. The stoichiometric relationship between oxygen carrier and methane in chemical-looping process is established by temperature programmed surface reaction (TPSR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) characterization. The effects of reduction conditions, namely, gas to solid molar ratio, temperature and sequential redox reaction on the oxygen carrier conversion are investigated. The results from Hancock and Sharp method suggest that the phase boundary control is likely to be dominant. The power law model (PLM), shrinking core model (SCM), as well as nucleation and nuclei growth model (NNGM) are considered to interpret the reduction kinetics of LaFeO3 with methane to synthesis gas. The obtained results show that the 2-D NNGM best describes the experimental data providing parameters with adequate statistical fitting indicators. The model validity is also verified by the data from continuous flow reaction and sequential redox cycles to simulate chemical-looping methane reforming process. The apparent activation energy is estimated and compared with values from the literature data.