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Plant S deficiency is common, but the role of S-containing amino acids such as cysteine in plant S uptake is unknown. We applied 14C-, 35S-, 13C-, and 15N-labelled cysteine to wheat and oilseed rape rhizospheres and traced the plants' elemental uptake. Both plants absorbed 0.37–0.81% of intact cysteine after 6 h with no further increase after 24 h. They absorbed 1.6–11.5% 35S and 12.3–7.6% 15N from cysteine after 24 h and utilised SO42− as their main S source (75.5–86.4%). Added and naturally occurring cysteine-S contributed 5.6 and 1.1% of total S uptake by wheat and oilseed rape, respectively. Cysteine and inorganic S derived from cysteine contributed 24.5 and 13.6% of uptake for wheat and oilseed rape, respectively, after 24 h. Oilseed rape absorbed ~10-fold more S from cysteine and SO42− than did wheat. The highest absorption of free cysteine should be in the organic-rich soil patches. Soil microorganisms rapidly decomposed cysteine (t1/2 = 1.37 h), and roots absorbed mineralised inorganic N and S. After 15 min, 11.7–14.3% of the 35S-cysteine was retained in the microbial biomass, while 30.2–36.7% of the SO42− was released, suggesting that rapid microbial S immobilisation occurs after cysteine addition. Plants acquire N and S from cysteine via unidirectional soil-to-root nutrient flow, and cysteine is an important S source for plants. [ABSTRACT FROM AUTHOR]

Aims: The capacity of plant roots to directly acquire organic nitrogen (N) in the form of oligopeptides and amino acids from soil is well established. However, plants have poor access to protein, the central reservoir of soil organic N. Our question is: do plants actively secrete proteases to enhance the breakdown of soil protein or are they functionally reliant on soil microorganisms to undertake this role? Methods: Growing maize and wheat under sterile hydroponic conditions with and without inorganic N, we measured protease activity on the root surface (root-bound proteases) or exogenously in the solution (free proteases). We compared root protease activities to the rhizosphere microbial community to estimate the ecological significance of root-derived proteases. Results: We found little evidence for the secretion of free proteases, with almost all protease activity associated with the root surface. Root protease activity was not stimulated under N deficiency. Our findings suggest that cereal roots contribute one-fifth of rhizosphere protease activity. Conclusions: Our results indicate that plant N uptake is only functionally significant when soil protein is in direct contact with root surfaces. The lack of protease upregulation under N deficiency suggests that root protease activity is unrelated to enhanced soil N capture. [ABSTRACT FROM AUTHOR]

Soil soluble nitrogen (N) is crucial to the N nutrition and productivity of plants. Consequently, understanding the factors that affect its pool size and composition is of considerable importance. Here, six typical forest types in northeast China were investigated to determine the dynamics of soil soluble N across seasons and plant communities, and the potential drivers. Soil free amino acids, NH4+, NO3−, dissolved organic N (DON) and a variety of soil characteristics were measured over the growing season (from May to September). Seasonality showed a stronger effect on the availability of soil inorganic N and free amino acids than vegetation. The coefficients of variation of soil inorganic N, amino acid-N and the potential drivers (moisture and DON) appeared to be greater for season, and the concentrations of these available N sources tended to be higher at the beginning than at the height of growing season. Potential soil drivers (e.g. moisture, microbial biomass-N and DON) and plant phenology together drove the seasonal dynamics of inorganic N and amino acid-N. Arginine, histidine, serine, leucine, aspartic acid, glycine, glutamic acid and proline composed the dominant soil amino acid pool in the temperate forest soils. The basic amino acids (arginine and histidine) were consistently dominant irrespective of vegetation and season, suggesting that selective sorption by the soil solid phase could play an important role in regulating the cycling of amino acid-N in these temperate forest ecosystems. This research indicates that changes in local soil properties, and plant phenology caused by seasonality, exert a powerful influence on the characteristics of plant-soil N cycling. [ABSTRACT FROM AUTHOR]

Purpose: Retrograde pyelography (RPG) is used in some centers to further evaluate patients with incompletely opacified segments on CT urography (CTU). This study intends to evaluate the utility of this imaging combination in terms of the yield of abnormal findings on the follow up RPG. Methods: In this retrospective study, we searched the radiology database over a three-year period (11/1/2015–10/30/2018) for patients who had a CTU and then a diagnostic RPG within 180 days. Images and reports were reviewed from this period for patients who met the inclusion criteria. Results: 292 patients underwent a CTU with follow up RPG over the search period. 131/292 RPGs (44.9%) were performed because the CTU described at least one incompletely opacified ureteral segment. Of the 148 ureters evaluated in these 131 patients, 4 ureters (2.7%) showed an abnormality on follow up retrograde pyelogram—two revealed a stricture at the unfilled segment, and two revealed contour irregularity in the distal ureter (biopsy showed urothelial cell carcinoma in these two). Conclusion: There is a relatively low yield for detecting ureteral abnormalities when a retrograde pyelogram is performed after a CTU to evaluate an incompletely opacified ureteral segment—2.7% in our study, with only two of these incompletely opacified segments containing urothelial cancer (1.4%). In these two cases, a ureteral abnormality was visible on the CTU and RPG would seem to have a very low yield for follow up of unopacified ureteral segments if the ureters are otherwise normal-appearing on CTU and there is no hydronephrosis. [ABSTRACT FROM AUTHOR]

A coupled hydrodynamic-wave-sediment model is used to simulate the broad-scale tidal circulation, surface waves, and suspended sediment concentrations (SSC) in Minas Basin, a 70-km long tidal estuary in the Bay of Fundy, during winter and summer periods. The model hydrodynamics are validated using acoustic-Doppler current profile observations, the surface SSC predictions are compared to satellite observations, and model results indicate that strong seasonal signals in SSC can be explained in part by seasonal changes in fetch-limited surface waves generated by local winds over the basin. The spatial and temporal variability of SSC is evaluated in this study by focussing on different forcing conditions from waves and tidal currents, the two primary physical process that influence the response of sediments in suspension. Model predictions in the intertidal areas indicate that surface waves can increase the bed shear stress from tidal currents alone by up to 1–5 Nm− 2, causing excess bed shear stresses to be higher and result in higher SSC by 100–200 gm− 3 particularly during wind events that are stronger and more frequent in winter months. Resuspension of sediments on tidal flats is driven by the combination of shear stresses from near-bed wave orbital velocities and tidal currents, and transport of the suspended materials over deeper areas of the basin is driven by advection from the strong tidal currents. [ABSTRACT FROM AUTHOR]

Understanding the processes that lead to seasonal changes in grain size on muddy macro-tidal flat and channel complexes will assist efforts to predict future changes caused by climate change and construction of infrastructure like tidal power generators, wind farms, and causeways. Surficial sediment samples were collected for disaggregated inorganic grain size (DIGS) analysis every month for 1 year from a tidal flat and from a tidal channel and its banks in Kingsport, NS, Canada, which is located in the Minas Basin of the Bay of Fundy. A process-based parameterization of the DIGS distribution was used to determine floc fraction, representative of the percentage of fine-grained material deposited to the seabed in flocs. Small changes in floc fraction occurred seasonally in the channel. Values were higher in late winter and lower in late summer. A more pronounced seasonal variation in floc fraction was observed on the tidal flats. Observed changes in floc fraction correlated with elevation. Results from this study are discussed in terms of the controls on floc fraction which include suspended particulate matter concentration (SPM), turbulence, and stickiness in the water column, all of which can be used to understand the formative processes responsible for shaping the bottom sediment texture. [ABSTRACT FROM AUTHOR]

Background and aims: There is ample experimental evidence for shifts in plant community composition under climate warming. To date, however, the underlying mechanisms driving these compositional shifts remain poorly understood.Methods: The amount and form of nitrogen (N) available to plants are among the primary factors limiting productivity and plant coexistence in terrestrial ecosystems. We conducted a short-term 15N tracer experiment in a ten-year warming and grazing experiment in an alpine grassland to investigate the effects of warming and grazing on plant uptake of NO3−-N, NH4+-N, and glycine-N. Four dominant plant species (Kobresia humilis, Potentilla anseria, Elymus nutans, Poa annua) were selected. Results We found that 10-years of warming decreased plant uptake of inorganic N by up to 80% in all species. In contrast, warming increased the uptake of organic N in K. humilis, P. anseria, and E. nutans but not in P. annua. Results showed that plant relative biomass increased hyperbolically with the ratio of the plant species total uptake of available N and plant community uptake of available N. And a significant positive correlation between plant species uptake of soil glycine-N and the uptake of total available N.Conclusions: The stable relative biomass of plant species is largely dependent on organic N uptake by plants. We conclude that plant organic N uptake maintains species dominance under long-term warming. [ABSTRACT FROM AUTHOR]

Soil organic matter (SOM) content is a key indicator of riparian soil functioning and in the provision of ecosystem services such as water retention, flood alleviation, pollutant attenuation and carbon (C) sequestration for climate change mitigation. Here, we studied the importance of microbial biomass and nutrient availability in regulating SOM turnover rates. C stabilisation in soil is expected to vary both vertically, down the soil profile and laterally across the riparian zone. In this study, we evaluated the influence of five factors on C mineralisation (Cmin): (i) substrate quantity, (ii) substrate quality, (iii) nutrient (C, N and P) stoichiometry, (iv) soil microbial activity with proximity to the river (2 to 75 m) and (v) as a function of soil depth (0-3 m). Substrate quality, quantity and nutrient stoichiometry were evaluated using high and low molecular weight 14C-labelled dissolved organic (DOC) along with different nutrient additions. Differences in soil microbial activity with proximity to the river and soil depth were assessed by comparing initial (immediate) Cmin rates and cumulative C mineralised at the end of the incubation period. Overall, microbial biomass C (MBC), organic matter (OM) and soil moisture content (MC) proved to be the major factors controlling rates of Cmin at depth. Differences in the immediate and medium-term response (42 days) of Cmin suggested that microbial growth increased and carbon use efficiency (CUE) decreased down the soil profile. Inorganic N and/or P availability had little or no effect on Cmin suggesting that microbial community growth and activity is predominantly C limited. Similarly, proximity to the watercourse also had relatively little effect on Cmin. This work challenges current theories suggesting that areas adjacent to watercourse process C differently from upslope areas. In contrast, our results suggest that substrate quality and microbial biomass are more important in regulating C processing rates rather than proximity to a river. [ABSTRACT FROM AUTHOR]

An untargeted strategy aiming at identifying non-intentionally added substances (NIAS) migrating from coatings was developed. This innovative approach was applied to two polyester-polyurethane lacquers, for which suppliers previously provided the identity of the monomers involved. Lacquers were extracted with acetonitrile and analyzed by liquid chromatography-high resolution mass spectrometry (LC-HRMS). Data, acquired in the full scan mode, were processed using an open-source R-environment (xcms and CAMERA packages) to list the detected features and deconvolute them in groups related to individual compounds. The most intense groups, accounting for more than 85% of cumulated feature intensities, were then investigated. A homemade database, populated with predicted polyester oligomer combinations from a relevant selection of diols and diacids, enabled highlighting the presence of 14 and 17 cyclic predicted polyester oligomers in the two lacquers, including three mutual combinations explained by common known monomers. Combination hypotheses were strengthened by chromatographic considerations and by the investigation of fragmentation patterns. Regarding unpredicted migrating substances, four monomers were hypothesised to explain several polyester or caprolactam oligomer series. Finally, considering both predicted and tentatively elucidated unpredicted oligomers, it was possible to assign hypotheses to features representing up to 82% and 90% of the cumulated intensities in the two lacquers, plus 9% and 3% (respectively) originating from the procedural blank.Elucidation of non-intentionally added substances [ABSTRACT FROM AUTHOR]

Extreme flood events are predicted to have a negative impact on soil quality. Currently, there is a lack of information about the effect of agricultural practices on soil functioning and microbial processes under these events. We hypothesized that the impact of flooding on soil quality will be exacerbated when crop residues are present in the soil as they will induce more extreme anaerobicity. A spring extreme flood event (10 °C, 9 weeks) was simulated in mesocosms containing an arable sandy-loam soil low in nutrients. The main treatments were (1) with and without flooding and (2) with and without maize residue addition (8 Mg ha). We monitored changes in soil chemical quality indicators (e.g. pH, salinity, Fe, P, C, NH , NO and organic N), greenhouse gas (GHG) emissions (CO, CH, NO) and soil microbial community composition (PLFAs) during a prolonged flood period (9 weeks) and an 8-week 'recovery' period after flooding. In comparison to the other treatments, flooding in the presence of crop residues resulted in a dramatic drop in soil redox potential. This was associated with the enhanced release of Fe and C into solution and an increase in CH emissions. In contrast, maize residues reduced potential nitrate losses and NO emissions, possibly due to complete denitrification and microbial N immobilization. Both flooding and maize residues stimulated microbial growth and promoted a shift in microbial community composition. Following floodwater removal, most of the soil quality indicators returned to the levels of the control treatment within 5 weeks. After this short recovery phase, no major impact of flooding could be observed on plant growth (maize pot-grown). Overall, we conclude that both extreme flooding and management regime negatively impact upon a range of soil quality indicators (e.g. redox, GHG emissions); however, the soil showed high resilience and recovered quickly after floodwater removal. Further work is required to investigate the impact of repeated extreme flood events on soil quality and function over longer timescales. [ABSTRACT FROM AUTHOR]

In this paper, we present a method for autonomously detecting and extracting region(s)-of-interest (ROI) from surveillance videos using trajectory-based analysis. Our approach, localizes ROI in a stochastic manner using correlated probability density functions that model motion dynamics of multiple moving targets. The motion dynamics model is built by analyzing trajectories of multiple moving targets and associating importance to regions in the scene. The importance of each region is estimated as a function of the total time spent by multiple targets, their instantaneous velocity and direction of movement whilst passing through that region. We systematically validate our model and benchmark our technique against competing baselines through extensive experimentation using public datasets such as CAVIAR, ViSOR, and CUHK as well as a scenario-specific in-house surveillance dataset. Results obtained have demonstrated the superiority of the proposed technique against a few popular existing state-of-the-art techniques. [ABSTRACT FROM AUTHOR]

Here, we investigated how root age and mode of death influenced their subsequent turnover and rate of C loss from soil. Young white-coloured and older pigmented roots of Cistus monspeliensis were excised (to simulate death by mechanical severance) or frozen (to simulate death by cell rupture) and immediately buried in soil. CO loss from soil was then measured over time. In a parallel experiment, the rate of CO loss from severed or ruptured roots in the absence of soil was determined. Our results revealed large differences in root chemistry related to age, with young roots having a lower C:N ratio and a greater nutrient content (soluble C, N, P and K). Both root age and mode of death resulted in very different temporal patterns of C release from soil. The amount of C lost from soil followed the series: severed white roots (42.6 ± 3.3 mg C) > ruptured pigmented roots (27.7 ± 0.4 mg C) = ruptured white roots (27.1 ± 0.5 mg C) > severed pigmented roots (10.1 ± 1.0 mg C) > soil only (3.0 ± 0.2 mg C). Therefore, depending on the treatment, 7 to 41% of the total root-derived C was lost as CO over the duration of the experiment. Comparison with soil-free treatments revealed that the CO release from the severed roots buried in soil was not associated with microbial breakdown but caused by root-induced autophagy in an attempt to keep themselves metabolically active. Ruptured roots also induced a rapid loss of CO which we ascribe to the diffusive loss of root solutes into the soil and subsequent microbial mineralization. Surprisingly, the rate of C loss from soil was greater from the severed root tips than those that were ruptured. Our results imply two distinct routes of C loss dependent on how roots die, one which bypasses the microbial community and one which flows through it. [ABSTRACT FROM AUTHOR]

Introduction: Grass species may acquire different forms of nitrogen (N) to reduce competition for the same resources. Climate change influences the availability of soil N and is therefore likely to cause shifts in N forms acquired by plants, thereby affecting their competitive interactions. Methods: We investigated the effects of warming on the uptake of different N forms and competitive interactions of Festuca ovina and Anthoxanthum odoratum in a pot experiment. The plants were grown either in monocultures or mixture, and at ambient or elevated temperature (+10 °C), and supplied with C and N isotopes to test for treatment effects on the relative uptake of ammonium, alanine or tri-alanine. Results: Both grass species took up relatively more N supplied as ammonium than as alanine or tri-alanine when grown under ambient conditions in monoculture. In contrast, when grown in mixtures, F. ovina took up the three supplied N forms in equal amounts, whereas A. odoratum switched to tri-alanine as the main N form. Under warmed conditions, both species took up the N forms equally, irrespective of competition treatments. Conclusions: We have shown that grass species grown in mixture and under ambient conditions reduce competition by acquiring different N forms. Warming increased the availability of inorganic N in the soil and therefore deregulated the need for differential uptake of N forms. [ABSTRACT FROM AUTHOR]

Peatlands export significant amounts of dissolved organic carbon (DOC) to freshwaters, but the quantity of DOC reaching marine environments is typically less than the input to the fluvial system due to processing within the water column. Key removal processes include photo-chemical degradation, and heterotrophic bacterial respiration. In this study we examined these processes using C-labelled DOC to quantify the extent of DOC breakdown and to determine its fate following irradiation under controlled laboratory conditions. We examined the influence of microbial processes occurring within the water column, the potential role of stream-bed biofilms, and the possible modifying effects of downstream mixing, as DOC in water from the peatland encounters runoff from upland mineral soils ('Mountain'), nutrient-rich runoff from agricultural soils, and seawater in an estuary. Our results demonstrated conservative mixing of DOC from Peatland and Mountain waters but interactive effects when Peatland water was mixed with Agricultural and Estuary waters and exposed to solar radiation. The mixing of Peatland and Agricultural waters led to net DOC production, suggesting that DOC was only partially degraded by solar radiation and that the products of this might have fuelled autotrophic microbial growth in the samples. The mixing of Peatland water with saline estuary water resulted in net DOC loss following irradiation, suggesting a role for sunlight in enhancing the flocculation of DOC to particulate organic carbon (POC) in saline environments. [ABSTRACT FROM AUTHOR]

Urine patches within pasture soils are hotspots for nitrogen (N) cycling and losses, where nitrification inhibitors (NI) offer a means of reducing such losses. Within urine influenced soil, more research has been conducted for dicyandiamide (DCD) than 3,4-dimethylpyrazole phosphate (DMPP). Differences in the efficacy of these NI are often ascribed to a greater mobility of DCD, which may lead to spatial separation from NH and nitrifying microorganisms. We tested the mobility of C-labelled DCD and DMPP relative to sheep urine-derived NH in soil columns of contrasting texture and organic matter content, following simulated rainfall. We also assessed factors influencing the vertical mobility of these NI in soils, including solubility, sorption/desorption processes and microbial degradation and uptake. Following 40-mm rainfall, without the presence of sheep urine, the distribution of both NI were similar in the soil columns; however, there was a greater retention of DCD compared to DMPP in the top 1 cm. Both NI appeared to co-locate well with urine-derived NH, and the presence of sheep urine altered the leaching profile of the NI (compared to rainfall application alone), but this effect was inhibitor and soil-type dependent. A greater sorption to the soil matrix was observed for DCD in comparison to DMPP in all three studied soils, and the presence of urine generally increased desorption processes. Of the NI applied to the soil columns, 18-66 % was taken up within 30 min by the microbial community. However, only small amounts (<1 %) were mineralized during this period. In conclusion, due to the greater adsorption of DCD as opposed to DMPP and similarity in the degree of co-location of both NI with urine NH, the results of this study suggest that differences in microbial uptake and degradation may be more important parameters for explaining differences in the efficacy of reducing nitrification. Further work is required to determine the comparative efficacy of both NI in reducing nitrification rates under field conditions in a range of soil types and environmental conditions. [ABSTRACT FROM AUTHOR]

Background and aims: There is increasing interest and use of nitrification inhibitors (NI) in agroecosystems, yet little is known of their fate in planta. Residues of the organic, N-rich NI, dicyandiamide (DCD), have been found in milk products following commercial application to pasture. We investigated whether plant acquisition and metabolism of DCD were consistent with plant-mediated transmission from soil to agricultural food products. Methods: Uptake rates, translocation to the shoot, degradation of the label within wheat tissue and availability within two soils of DCD and the structurally similar naturally occurring N-rich molecule, guanidine, were measured using C labelling. Results: Under sterile conditions, over 2 h wheat took up (34 and 14 μmol g root DW h at 1 mM: DCD and guanidine, respectively), translocated (7-15 and 19-22 %) and metabolised (0.4 and 0.9 % of uptake) DCD- and guanidine-C. Both molecules were also acquired from soil by wheat despite concurrent soil sorption and microbial uptake. Conclusions: Both DCD and guanidine can be acquired and metabolised by graminaceous plants. Although probably not a significant route of N acquisition, plant uptake provides a direct route of DCD entry into the food chain. [ABSTRACT FROM AUTHOR]

The goal of this research was to investigate size-specific retention of clay and silt-sized grains by biofilms in sandy intertidal sediments. Sediment cores were collected from an intertidal flat in Cole Harbour, NS, and eroded at increasing shear stresses (0.08-0.60 Pa) with a Gust microcosm. Half of the cores were eroded without undergoing prior treatment, while sodium hypochlorite was added to the other cores to destroy biofilms. The disaggregated inorganic grain size distribution of sediment resuspended by the Gust microcosm was then obtained with a Multisizer 3 Coulter Counter®, and each treated core was compared with its corresponding untreated core. Overall, significantly less total sediment mass was resuspended from untreated cores than from treated cores. At intermediate shear stresses, the sediment resuspended from treated cores contained a greater proportion of fine and medium silts than the sediment resuspended from untreated cores. Very fine silts and clays were not retained preferentially by biofilms. The results show that biofilms stabilize the sediment, but they do not necessarily enhance the proportion of finest sediment sizes, as previously proposed. [ABSTRACT FROM AUTHOR]

Over the past 20 years, our understanding of soil nitrogen (N) cycling has changed with evidence that amino acids are major substrates for both soil microorganisms and plants. However, the recent discovery that plants and microorganisms can directly utilize small peptides in soil needs to be evaluated for its ecological significance, because peptides are released earlier in protein decomposition and thus would provide significant competitive advantage to any organism that can use them directly. We tested whether soil microorganisms took up peptides faster than amino acids across a broad range of ecosystems. We show that l-enantiomeric-peptidic-N is taken up significantly faster than the equivalent monomer, and that this is universal across soils from different ecosystems, with distinct microbial communities. Peptides may have an unrecognized, global, importance in the terrestrial N cycle, providing N to soil microorganisms at an earlier stage of decomposition than previously acknowledged. [ABSTRACT FROM AUTHOR]

lthough progress has been made, greater efforts are needed to promote faculty diversity at the college and university levels, especially in STEM fields. Thus, it is important to elucidate best practices both for increasing awareness of diversity issues pertaining to higher education and for implementing change. This article focuses on the outcomes of a diversity workshop for college and university faculty hosted by the West Virginia Higher Education Policy Commission, Division of Science and Research. More specifically, it elucidates how participation in the workshop translated into practice at the faculty participants' home institutions. [ABSTRACT FROM AUTHOR]

Rising atmospheric CO2 concentrations have highlighted the importance of being able to understand and predict C fluxes in plant-soil systems. We investigated the responses of the two fluxes contributing to below-ground efflux of plant root-dependent CO2, root respiration and rhizomicrobial respiration of root exudates. Wheat ( Triticum aestivum L ., var. Consort) plants were grown in hydroponics at 20°C, pulse-labelled with 14CO2 and subjected to two regimes of temperature and light (12 h photoperiod or darkness at either 15°C or 25°C), to alter plant C supply and demand. Root respiration was increased by temperature with a Q 10 of 1.6. Root exudation was, in itself, unaltered by temperature, however, it was reduced when C supply to the roots was reduced and demand for C for respiration was increased by elevated temperature. The rate of exudation responded much more rapidly to the restriction of C input than did respiration and was approximately four times more sensitive to the decline in C supply than respiration. Although temporal responses of exudation and respiration were treatment dependent, at the end of the experimental period (2 days) the relative proportion of C lost by the two processes was conserved despite differences in the magnitude of total root C loss. Approximately 77% of total C and 67% of 14C lost from roots was accounted for by root respiration. The ratio of exudate specific activity to CO2 specific activity converged to a common value for all treatments of 2, suggesting that exudates and respired CO2were not composed of C of the same age. The results suggest that the contributions of root and rhizomicrobial respiration to root-dependent below-ground respiration are conserved and highlight the dangers in estimating short-term respiration and exudation only from measurements of labelled C. The differences in responses over time and in the age of C lost may ultimately prove useful in improving estimates of root and rhizomicrobial respiration. [ABSTRACT FROM AUTHOR]

The release of root exudates into the rhizosphere is known to enhance soil biological activity and alter microbial community structure. To assess whether root exudates also stimulated litter decomposition, in a rhizosphere model system we continuously injected solutions of glucose, malate or glutamate through porous Rhizon® soil solution samplers into the soil at rhizosphere concentrations. The effect of these substances on the decomposition of 14C-labelled Lolium perenne shoot residues present in the soil was evaluated by monitoring 14CO2 evolution at either 15°C or 25°C. The incorporation of the 14C into the microbial biomass and appearance in the dissolved organic matter (DOM) pool was estimated after 32 d incubation. The presence of malate and glutamate increased the mineralization of L. perenne residues by approximately 20% relative to the soil without their addition at 15°C, however, no significant effects on residue decomposition were observed at 25°C. The incorporation of the 14C-label into the microbial biomass and DOM pool was not affected by the addition of either glucose, malate or glutamate. Although nearly the same amount of L. perenne residues were mineralized at either temperature after 32 d, less 14C was recovered in the microbial biomass and DOM pools at 25°C compared to 15°C. Alongside other results, this suggests that the rate of microbial turnover is greater at 25°C compared to 15°C. We conclude that the addition of labile root exudate components to the rhizosphere induced a small but significant increase on litter decomposition but that the magnitude of this effect was regulated by temperature. [ABSTRACT FROM AUTHOR]

Classical epistasis analysis can determine the order of function of genes in pathways using morphological, biochemical and other phenotypes. It requires knowledge of the pathway's phenotypic output and a variety of experimental expertise and so is unsuitable for genome-scale analysis. Here we used microarray profiles of mutants as phenotypes for epistasis analysis. Considering genes that regulate activity of protein kinase A in Dictyostelium, we identified known and unknown epistatic relationships and reconstructed a genetic network with microarray phenotypes alone. This work shows that microarray data can provide a uniform, quantitative tool for large-scale genetic network analysis. [ABSTRACT FROM AUTHOR]

Presents the temporal variation of apoplastic ammonium concentration and pH measured in leaves of Lolium perenne L. in a grassland, through two period of cutting/fertilization, followed by a livestock grazing period. Leaf apoplastic ammonium concentration and pH; Compensation point and the ratio of ammonium to pH concntrations; Total free ammonium in leaves; Soil nitrogen trioxide and ammonium concentration.

Increases in N deposition (wet and dry) have been associated with a decline in semi-natural plant communities, adapted for growth on nutrient poor soils in the UK and Europe. The impacts of N deposition applied as either wet NH4+ or gaseous NH3 on vegetation (7 species) from acid moorland in SE Scotland were compared in a dose-response study. Wet N deposition at 0, 8, 16, 32, 64, 128 kg N ha-1 y-1 was applied as NH4Cl, and dry deposition as gaseous NH3 (2, 6, 20, 50, 90 µg NH3 m-3) under controlled conditions in open-top chambers. A strong linear dose-response relationship (p<0.05) was found between foliar N content in all seven plant species and applied NH4-N. However, in the NH3 treatment, only C. vulgaris and P. commune showed a significant response to increasing N additions. NH3 was found to increase the rate of water loss in Calluna in both autumn and winter by comparison with wet deposition. For Eriophorum vaginatum, the NH3 and NH4+ treatments showed significant N dose response relationships for biomass. A significant increase in above ground biomass, proportional to the added N, was found for Narthecium ossifragum when N was applied as NH3 compared to NH4+. [ABSTRACT FROM AUTHOR]

Ethanol yield and ethanol tolerance, the two factors that most constrain the utilization of thermophilic bacteria for ethanol production, were investigated in continuous xylose-grown cultures of Clostridium thermosaccharolyticum. Under xylose-limiting conditions, including varying dilution rates and feed concentrations, the ethanol selectivity (Se, mol/mol) relative to acetic acid, lactic acid, and propane diol remained relatively constant at about 2. Product addition and removal experiments indicate that mass action effects related to the concentrations of organic fermentation products play a relatively minor role in determining the ratios of products made. Of much greater apparent importance were as yet uncharacterized regulatory mechanisms that appear to be correlated with nonlimiting concentrations of the carbon and energy-source. Substrate-plentiful transients were found to accompany Se values > 11. Such transients provide a useful model system for the study of end product control, as well as a cultivation mode with considerable applied potential. No apparent ethanol inhibition was observed, as indicated by no decrease in the maximum rate of growth allowing complete substrate utilization (0.22 h) for endogenously-produced ethanol concentrations up to 11.4 g/L, and total endogenously-produced + exogenously-added ethanol concentrations up to 21.3 g/L. Higher concentrations of ethanol are tolerated at µ = 0.11 h, although the onset of inhibition was not characterized at this growth rate. Results suggest that the ethanol tolerance of C. thermosaccharolyticum grown in continuous culture may be greater than that typically observed previously for thermophiles grown in batch culture. [ABSTRACT FROM AUTHOR]

A wetland atlas (Mitsch et al. 1983) was developed for a 3960 km region of the Western Coalfield in Kentucky to inventory the wetlands there and to present a regional assessment of coal surface mining. Both the methodology and the results of the atlas are presented as they relate to wetland management. The atlas was designed to present the location, type, and extent of wetlands as well as useful environmental and ecological information for both wetland managers and coal mine operators. The study identified 460 km of wetlands with about 84 percent as broad-leaved deciduous forested wetlands. There were also 5.6 km of needle-leaved deciduous wetlands (bald cypress swamps) and 24.3 km of persistent emergent wetlands, scrub-shrub wetlands, and dead forested wetlands. Surface mines were also identified from aerial photography for the atlas and were often shown to be contiguous with existing wetlands. Data on hydrology, water chemistry, and fish and wildlife resources were gathered from several sources to supplement the mapping and inventory results. The complete inventory showed that surface mining had several impacts on wetlands, including 1) direct removal, 2) acid drainage, 3) sedimentation, and 4) altered hydroperiod. [ABSTRACT FROM AUTHOR]

The initial attractiveness of the volume of isoflow (V) as an index of early small airways dysfunction has faded, perhaps because of V's high variability, a significant part of which is contributed by the observer. We suggest here that the observer variability can be removed by filtering the flow data in the reciprocal volume domain, by using a modified foreign gas mixture in which some of the helium is replaced by neon, and by reading V from a plot of density dependence vs. lung inflation. Support for these suggestions is drawn from both model simulations and experiments. Model simulations suggested that V would be increased by the substitution of neon for some of the helium in the usual helium-oxygen (Helox) mixture. This was confirmed in tests on matched groups of normal and asymptomatic asthmatic children. The inclusion of 20% neon (Heneox20) was found to reduce the coefficient of variation in the mean value of V in both groups of subjects. An interesting result of this test was that V using Heneox20 was significantly higher in the asthmatic group than in the normal group, whereas V using Helox was not. The results for density dependence (DD) between the 2 groups were not significantly different using Heneox20 but were using Helox. Plots of DD (derived from heavily filtered flow curves) vs. lung inflation showed an unambiguous value for V. [ABSTRACT FROM AUTHOR]

Throughout the black community, one of the most compelling issues is the socialization process of young people. There is a growing feeling of alienation and despondency being exhibited by youth and adults alike. Back To The Future addresses the issue of Western socialization and offers an African Life Paradigm For Life Cycles Development. Rites of Passage, the vessel for life cycles development, is discussed as a process for the shaping of centered and grounded African American adults. [ABSTRACT FROM AUTHOR]

Proteins play a crucial role in many soil processes, however, standardised methods to extract soluble protein from soil are lacking. The aim of this study was to compare the ability of different extractants to quantify the recovery of soluble proteins from three soil types (Cambisol, Ferralsol and Histosol) with contrasting clay and organic matter contents. Known amounts of plant-derived 14C-labelled soluble proteins were incubated with soil and then extracted with solutions of contrasting pH, concentration and polarity. Protein recovery proved highly solvent and soil dependent (Histosol > Cambisol > Ferralsol) and no single extractant was capable of complete protein recovery. In comparison to deionised water (10-60% of the total protein recovered), maximal recovery was observed with NaOH (0.1 M; 61-80%) and Na-pyrophosphate (0.05 M, pH 7.0; 45-75% recovery). We conclude that the dependence of protein recovery on both extractant and soil type prevents direct comparison of studies using different recovery methods, particularly if no extraction controls are used. We present recommendations for a standard protein extraction protocol. [ABSTRACT FROM AUTHOR]