3,783 research outputs found
A commercial arbuscular mycorrhizal inoculum increases root colonization across wheat cultivars but does not increase assimilation of mycorrhizaâacquired nutrients
Production and heavy application of chemicalâbased fertilizers to maintain crop yields is unsustainable due to pollution from runâoff, high CO2 emissions, and diminishing yield returns. Access to fertilizers will be limited in the future due to rising energy costs and dwindling rock phosphate resources. A growing number of companies produce and sell arbuscular mycorrhizal fungal (AMF) inoculants, intended to help reduce fertilizer usage by facilitating crop nutrient uptake through arbuscular mycorrhizas. However, their success has been variable. Here, we present information about the efficacy of a commercially available AMF inoculant in increasing AMF root colonization and fungal contribution to plant nutrient uptake, which are critical considerations within the growing AMF inoculant industry.
Summary
Arable agriculture needs sustainable solutions to reduce reliance on large inputs of nutrient fertilizers while continuing to improve crop yields. By harnessing arbuscular mycorrhizal symbiosis, there is potential to improve crop nutrient assimilation and growth without additional inputs, although the efficacy of commercially available mycorrhizal inocula in agricultural systems remains controversial.
Using stable and radioisotope tracing, carbonâforânutrient exchange between arbuscular mycorrhizal fungi and three modern cultivars of wheat was quantified in a nonâsterile, agricultural soil, with or without the addition of a commercial mycorrhizal inoculant.
While there was no effect of inoculum addition on aboveâground plant biomass, there was increased root colonization by arbuscular mycorrhizal fungi and changes in community structure. Inoculation increased phosphorus uptake across all wheat cultivars by up to 30%, although this increase was not directly attributable to mycorrhizal fungi. Carbonâforânutrient exchange between symbionts varied substantially between the wheat cultivars.
Plant tissue phosphorus increased in inoculated plants potentially because of changes induced by inoculation in microbial community composition and/or nutrient cycling within the rhizosphere. Our data contribute to the growing consensus that mycorrhizal inoculants could play a role in sustainable food production systems of the future
Assessment of the food available to cape anchovy during their spawning season
The Cape anchovy Engraulis capensis spawns serially between September and February each year on the western Agulhas Bank, South Africa. Food availability in terms of copepod biomass is important for successfulspawning and subsequent recruitment. This note investigates the variability within a spawning season (1993/94 and 1994/95) of copepod biomass on the western Bank and demonstrates that the food available to the Capeanchovy cannot be adequately assessed by a single mid-season estimate, as was the previous sampling strategy. The mid-season estimate of food availability failed to reveal important fluctuations, such as the small biomass of copepods in January 1994, which contributed to the early cessation of spawning and subsequent poor recruitment in 1994. A strategy, based on monthly sampling, is recommended for future sampling programmes
Sexual behaviour in Britain: partnerships, practices, and HIV risk behaviours.
BACKGROUND: Sexual behaviour is a major determinant of sexual and reproductive health. We did a National Survey of Sexual Attitudes and Lifestyles (Natsal 2000) in 1999-2001 to provide population estimates of behaviour patterns and to compare them with estimates from 1990-91 (Natsal 1990). METHODS: We did a probability sample survey of men and women aged 16-44 years who were resident in Britain, using computer-assisted interviews. Results were compared with data from respondents in Natsal 1990. FINDINGS: We interviewed 11161 respondents (4762 men, 6399 women). Patterns of heterosexual and homosexual partnership varied substantially by age, residence in Greater London, and marital status. In the past 5 years, mean numbers of heterosexual partners were 3.8 (SD 8.2) for men, and 2.4 (SD 4.6) for women; 2.6% (95% CI 2.2-3.1) of both men and women reported homosexual partnerships; and 4.3% (95% CI 3.7-5.0) of men reported paying for sex. In the past year, mean number of new partners varied from 2.04 (SD 8.4) for single men aged 25-34 years to 0.05 (SD 0.3) for married women aged 35-44 years. Prevalence of many reported behaviours had risen compared with data from Natsal 1990. Benefits of greater condom use were offset by increases in reported partners. Changes between surveys were generally greater for women than men and for respondents outside London. INTERPRETATION: Our study provides updated estimates of sexual behaviour patterns. The increased reporting of risky sexual behaviours is consistent with changing cohabitation patterns and rising incidence of sexually transmitted infections. Observed differences between Natsal 1990 and Natsal 2000 are likely to result from a combination of true change and greater willingness to report sensitive behaviours in Natsal 2000 due to improved survey methodology and more tolerant social attitudes
The effect of sea temperature and food availability on the spawning success of Cape Anchovy engraulis capensis in the Southern Benguela
Data on the thermal structure, copepod biomass and production, and total number of eggs of the Cape anchovy Engraulis capensis were obtained from monthly surveys during the periods August 1993 â March1994 and September 1994 â March 1995 on the western Agulhas Bank and off the South-Western Cape, South Africa. Previous work suggested that anchovy spawn on the western Agulhas Bank in temperaturesbetween 16 and 19°C, where they feed predominantly on copepods. This study shows that the western Bank is a more suitable spawning area for anchovy, having greater thermal stability, a larger area of 16â19°Cwater and a more consistent food environment than off the South-Western Cape. Also, copepod production on the western Bank was highest in 16â19°C water. To identify factors controlling the area of this watermass, a cluster analysis was used on a suite of hydrographic variables. Three periods were identified: winter (August-September), spring (October-December) and summer (January-March), reflecting changes in theextent of the 16â19°C water and anchovy spawning, both of which peaked during spring. Spring was further characterized by infrequent surface upwelling. During summer, upwelling frequently reached the surface andthe upwelling front migrated offshore, constricting the area of 16â19°C water. It is hypothesized that spawning success in anchovy is dependent upon the extent of suitable spawning habitat, both spatially (16â19°Cwater) and temporally (spring). To put this concept into a predictive framework, the number of anchovy eggs was regressed against the area of 16â19°C water; a significant, positive relationship (p < 0.001, r2 = 0.56, n = 17) was found. An implication of the hypothesis is that the duration of spawning may be important to recruitment
Chapter 6: Ice-Phase Precipitation
Ice-phase precipitation occurs at Earthâs surface and may include various types of pristine crystals, rimed crystals, freezing droplets, secondary crystals, aggregates, graupel, hail, or combinations of any of these. Formation of ice-phase precipitation is directly related to environmental and cloud meteorological parameters that include available moisture, temperature, and three-dimensional wind speed and turbulence, as well as processes related to nucleation, cooling rate, and microphysics. Cloud microphysical parameters in the numerical models are resolved based on various processes such as nucleation, mixing, collision and coalescence, accretion, riming, secondary ice particle generation, turbulence, and cooling processes. These processes are usually parameterized based on assumed particle size distributions and ice crystal microphysical parameters such as mass, size, and number and mass density. Microphysical algorithms in the numerical models are developed based on their need for applications. Observations of ice-phase precipitation are performed using in situ and remote sensing platforms, including radars and satellite-based systems. Because of the low density of snow particles with small ice water content, their measurements and predictions at the surface can include large uncertainties. Wind and turbulence affecting collection efficiency of the sensors, calibration issues, and sensitivity of ground-based in situ observations of snow are important challenges to assessing the snow precipitation. This chapterâs goals are to provide an overview for accurately measuring and predicting ice-phase precipitation. The processes within and below cloud that affect falling snow, as well as the known sources of error that affect understanding and prediction of these processes, are discussed
Normative Visual Development: efficient coding principles for adult V1 predict properties of LGN waves prior to eye opening
The effect of contextual variables on match performance across different playing positions in professional portuguese soccer players
This study investigated the position-specific physical demands of professional Portuguese players. The effects of situational variables on the physical performance demands were also analysed (match location, match half and match result). Match performance observations were collected using Global Navigation Satellite System devices across 11 matches during a competitive season (2019â 2020). Data were analysed according to five playing positions: goalkeepers (n = 11), central defenders (n = 42), wide defenders (n = 31), central midfielders (n = 34), open attackers (n = 28), and centre forwards (n = 14). Central midfield players completed the greatest total distance (10,787 ± 1536 m), while central defenders covered the least distance (9272 ± 455; p < 0.001). Open attackers covered the greatest high and very-high-speed distance (1504 ± 363 m), number of high-speed decelerations per match (11 ± 4) and were the fastest players (30.6 ± 1.5 km/h), along with center forwards (30.6 ± 2.0 km/h), versus all other positions (p < 0.05). Greater distances were performed in teams that were winning (9978 ± 1963 m) or drawing (10,395 ± 875 m) versus losing (9415 ± 2050) p = 0.036 and p = 0.006, respectively. Increases in distance covered at walking speeds were observed during the 2nd half (1574 ± 179 m) compared with the 1st half (1483 ± 176; (p < 0.003). A higher number of decelerations across all speeds were performed in the 1st half (144 ± 39) versus the 2nd half (135 ± 37). The distance covered in home matches (10,206 ± 1926 m) far exceeded away matches (9471 ± 1932 m; p < 0.001). The number of faster accelerations were higher in away (7 ± 5) versus home matches (6 ± 4; p < 0.049). The data demonstrate the different physical demands of each playing position and suggest that situational variables influence physical performance. These findings suggest position-specific physical training is required to condition players for the bespoke demands of each playing position
The Importance of CHâ Ebullition in Floodplain Fens
Uncertainty in estimates of CH4 emissions from peatlands arise, in part, due to difficulties in quantifying the importance of ebullition. This is a particular concern in temperate lowland floodplain fens in which total CH4 emissions to the atmosphere (often measured as the sum of diffusive and plantâmediated fluxes) are known to be high, but few direct measurements of CH4 ebullition fluxes have been made. Our study quantified CH4 fluxes (diffusion, plantâmediated, and ebullition) from two temperate floodplain fens under conservation management (Norfolk, UK) over 176 days using funnels and static chambers. CH4 ebullition was a major component (>38%) of total CH4 emissions over spring and summer. Seasonal variations in quantifiable CH4 ebullition fluxes were marked, covering six orders of magnitude (5 Ă 10â5 to 62 mg·CH4·mâ2·hrâ1). This seasonal variability in CH4 ebullition fluxes arose from changes in both bubble volume flux and bubble CH4 concentration, highlighting the importance of regular measurements of the latter for accurate assessment of CH4 ebullition using funnels. Soil temperature was the primary control on CH4 ebullition fluxes. Elevated water level was also associated with increased CH4 ebullition fluxes, with a distinct increase in CH4 ebullition flux when water level rose to within 10 cm of the peat surface. In contrast, CH4 ebullition flux decreased steadily with increasing plant cover (measured as vascular green area). Ebullition was both steady and episodic in nature, and drops in air pressure during the twoâday funnel deployments were associated with higher fluxes
Estimating the Prevalence of Sexual Function Problems: The Impact of Morbidity Criteria
Establishing the clinical significance of symptoms of sexual dysfunction is challenging. To address this, the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) introduced two new morbidity criteria (duration and symptom severity) to the existing criteria of distress. This study sought to establish the impact of these three criteria on the population prevalence of sexual function problems. The data come from a national probability survey (Natsal-3) and are based on 11,509 male and female participants aged 16-74, reporting at least one sexual partner in the past year. The key outcomes were: proportion of individuals reporting proxy measures of DSM-5 problems, and the proportion of those meeting morbidity criteria. We found that among sexually active men, the prevalence of reporting one or more of four specific sexual problems was 38.2%, but 4.2% after applying the three morbidity criteria; corresponding figures for women reporting one or more of three specific sexual problems, were 22.8% and 3.6%. Just over a third of men and women reporting a problem meeting all three morbidity criteria had sought help in the last year. We conclude that the DSM-5 morbidity criteria impose a focus on clinically significant symptoms
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