Effect of light and darkness on the growth and development of downy mildew pathogen Hyaloperonospora arabidopsidis

Disease development in plants requires a susceptible host, a virulent pathogen, and a favourable environment. Oomycete pathogens cause many important diseases and have evolved sophisticated molecular mechanisms to manipulate their hosts. Day length has been shown to impact plant‐oomycete interactions but a need exists for a tractable reference system to understand the mechanistic interplay between light regulation, oomycete pathogen virulence, and plant host immunity. Here we present data demonstrating that light is a critical factor in the interaction between Arabidopsis thaliana and its naturally occurring downy mildew pathogen Hyaloperonospora arabidopsidis (Hpa). We investigated the role of light on spore germination, mycelium development, sporulation and oospore formation of Hpa, along with defence responses in the host. We observed abundant Hpa sporulation on compatible Arabidopsis under day lengths ranging from 10 to 14 hours. Contrastingly, exposure to constant light or constant dark suppressed sporulation. Exposure to constant dark suppressed spore germination, mycelial development and oospore formation. Interestingly, exposure to constant light stimulated spore germination, mycelial development and oospore formation. A biomarker of plant immune system activation was induced under both constant light and constant dark. Altogether, these findings demonstrate that Hpa has the molecular mechanisms to perceive and respond to light and that both the host and pathogen responses are influenced by the light regime. Therefore, this pathosystem can be used for investigations to understand the molecular mechanisms through which oomycete pathogens like Hpa perceive and integrate light signals, and how light influences pathogen virulence and host immunity during their interactions

A Global Perspective on Phosphorus Management Decision Support in Agriculture: Lessons Learned and Future Directions

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Adult beginner distance language learner perceptions and use of assignment feedback

This qualitative study examines perceptions and use of assignment feedback among adult beginner modern foreign language learners on higher education distance learning courses. A survey of responses to feedback on assignments by 43 Open University students on beginner language courses in Spanish, French, and German indicated that respondents can be classified into three groups: those who use feedback strategically by integrating it into the learning process and comparing it with, for example, informal feedback from interaction with native speakers, those who take note of feedback, but seem not to use it strategically, and those who appear to take little account of either marks or feedback. The first group proved to be the most confident and most likely to maintain their motivation in the longer term. The conclusion discusses some of the pedagogical and policy implications of the findings

The inverse problem of determining the filtration function and permeability reduction in flow of water with particles in porous media

The original publication can be found at www.springerlink.comDeep bed filtration of particle suspensions in porous media occurs during water injection into oil reservoirs, drilling fluid invasion of reservoir production zones, fines migration in oil fields, industrial filtering, bacteria, viruses or contaminants transport in groundwater etc. The basic features of the process are particle capture by the porous medium and consequent permeability reduction. Models for deep bed filtration contain two quantities that represent rock and fluid properties: the filtration function, which is the fraction of particles captured per unit particle path length, and formation damage function, which is the ratio between reduced and initial permeabilities. These quantities cannot be measured directly in the laboratory or in the field; therefore, they must be calculated indirectly by solving inverse problems. The practical petroleum and environmental engineering purpose is to predict injectivity loss and particle penetration depth around wells. Reliable prediction requires precise knowledge of these two coefficients. In this work we determine these quantities from pressure drop and effluent concentration histories measured in one-dimensional laboratory experiments. The recovery method consists of optimizing deviation functionals in appropriate subdomains; if necessary, a Tikhonov regularization term is added to the functional. The filtration function is recovered by optimizing a non-linear functional with box constraints; this functional involves the effluent concentration history. The permeability reduction is recovered likewise, taking into account the filtration function already found, and the functional involves the pressure drop history. In both cases, the functionals are derived from least square formulations of the deviation between experimental data and quantities predicted by the model.Alvarez, A. C., Hime, G., Marchesin, D., Bedrikovetski, P

The Two-Dimensional Content of Consciousness

In this paper I put forward a representationalist theory of conscious experience based on Robert Stalnaker's version of two-dimensional modal semantics. According to this theory the phenomenal character of an experience correlates with a content equivalent to what Stalnaker calls the diagonal proposition. I show that the theory is closely related both to functionalist theories of consciousness and to higher-order representational theories. It is also more compatible with an anti-Cartesian view of the mind than standard representationalist theories.</p

A multi-species synthesis of physiological mechanisms in drought-induced tree mortality

Widespread tree mortality associated with drought 92 has been observed on all forested continents, and global change is expected to exacerbate vegetation vulnerability. Forest mortality has implications for future biosphere-atmosphere interactions of carbon, water, and energy balance, and is poorly represented in dynamic vegetation models. Reducing uncertainty requires improved mortality projections founded on robust physiological processes. However, the proposed mechanisms of drought-induced mortality, including hydraulic failure and carbon starvation, are unresolved. A growing number of empirical studies have investigated these mechanisms, but data have not been consistently analyzed across species and biomes using a standardized physiological framework. Here we show that xylem hydraulic failure was ubiquitous across multiple tree taxa at drought induced mortality. All species assessed had 60% or higher loss of xylem hydraulic conductivity, consistent with proposed theoretical and modelled survival thresholds. We found diverse responses in non-structural carbohydrate reserves at mortality, indicating that evidence supporting carbon starvation was not universal. Reduced non-structural carbohydrates were more common for gymnosperms than angiosperms, associated with xylem hydraulic vulnerability, and may have a role in reducing hydraulic function. Our finding that hydraulic failure at drought-induced mortality was persistent across species indicates that substantial improvement in vegetation modelling can be achieved using thresholds in hydraulic function

A multi-species synthesis of physiological mechanisms in drought-induced tree mortality

Widespread tree mortality associated with drought 92 has been observed on all forested continents, and global change is expected to exacerbate vegetation vulnerability. Forest mortality has implications for future biosphere-atmosphere interactions of carbon, water, and energy balance, and is poorly represented in dynamic vegetation models. Reducing uncertainty requires improved mortality projections founded on robust physiological processes. However, the proposed mechanisms of drought-induced mortality, including hydraulic failure and carbon starvation, are unresolved. A growing number of empirical studies have investigated these mechanisms, but data have not been consistently analyzed across species and biomes using a standardized physiological framework. Here we show that xylem hydraulic failure was ubiquitous across multiple tree taxa at drought induced mortality. All species assessed had 60% or higher loss of xylem hydraulic conductivity, consistent with proposed theoretical and modelled survival thresholds. We found diverse responses in non-structural carbohydrate reserves at mortality, indicating that evidence supporting carbon starvation was not universal. Reduced non-structural carbohydrates were more common for gymnosperms than angiosperms, associated with xylem hydraulic vulnerability, and may have a role in reducing hydraulic function. Our finding that hydraulic failure at drought-induced mortality was persistent across species indicates that substantial improvement in vegetation modelling can be achieved using thresholds in hydraulic function

The Emergence and Development of Association Football: Influential Sociocultural Factors in Victorian Birmingham

This article explores the interdependent, complex sociocultural factors that facilitated the emergence and diffusion of football in Birmingham. The focus is the development of football in the city, against the backdrop of the numerous social changes in Victorian Birmingham. The aim is to fill a gap in the existing literature which seemingly overlooked Birmingham as a significant footballing centre, and the ‘ordinary and everyday’ aspects of the game’s early progression. Among other aspects, particular heed is paid to the working classes’ involvement in football, as previous literature has often focused on the middle classes and their influence on and participation in organized sport. As the agency of the working classes along with their mass participation and central role in the game’s development is unfolded, it is argued that far from being passive cultural beings, the working classes, from the beginnings, actively negotiated the development of their own emergent football culture