Diurnal Variation in Gas Exchange: The Balance between Carbon Fixation and Water Loss

Stomatal control of transpiration is critical for maintaining important processes, such as plant water status, leaf temperature, as well as permitting sufficient CO2 diffusion into the leaf to maintain photosynthetic rates (A). Stomatal conductance often closely correlates with A and is thought to control the balance between water loss and carbon gain. It has been suggested that a mesophyll-driven signal coordinates A and stomatal conductance responses to maintain this relationship; however, the signal has yet to be fully elucidated. Despite this correlation under stable environmental conditions, the responses of both parameters vary spatially and temporally and are dependent on species, environment, and plant water status. Most current models neglect these aspects of gas exchange, although it is clear that they play a vital role in the balance of carbon fixation and water loss. Future efforts should consider the dynamic nature of whole-plant gas exchange and how it represents much more than the sum of its individual leaf-level components, and they should take into consideration the long-term effect on gas exchange over time

Acclimation to fluctuating light impacts the rapidity and diurnal rhythm of stomatal conductance.

Plant acclimation to growth light environment has been studied extensively, however, the majority of these studies have focused on light intensity and photo-acclimation, with few studies exploring the impact of dynamic growth light on stomatal acclimation and behavior. In order to assess the impact of growth light regime on stomatal acclimation, we grew plants in three different lighting regimes (with the same average daily intensity); fluctuating with a fixed pattern of light, fluctuating with a randomized pattern of light (sinusoidal), and non-fluctuating (square wave), to assess the effect of light regime dynamics on gas exchange. We demonstrated that gs acclimation is influenced by both intensity and light pattern, modifying the stomatal kinetics at different times of the day resulting in differences in the rapidity and magnitude of the gs response. We also describe and quantify response to an internal signal that uncouples variation in A and gs over the majority of the diurnal period, and represents 25% of the total diurnal gs. This gs response can be characterized by a Gaussian element and when incorporated into the widely used Ball-Berry Model greatly improved the prediction of gs in a dynamic environment. From these findings we conclude that acclimation of gs to growth light could be an important strategy for maintaining carbon fixation and overall plant water status, and should be considered when inferring responses in the field from laboratory based experiments

The Flexibility and Strength of Corrugated Diaphragms and Folded Plates

Trapozoi, lally corrugated sheeting has been previously studiedwith regald to applications in shear diaphragms, making use of itsinherent strength and stiffness prepeitios by suitable connections.The in-plane deflection is an important design factor and the sheardistortion component, due to eccentric transfer of fastener force intoprofile shear, is a major contributor to the total. A design formu]ais developed for the distortional shear flexibility for .ets taste edin every trough and in intermediate purlins which takes account of thelocalized distortion at the sheet ends by using an energy method analysisof assumed displacement functions to represent plate bending.For fastening in alternate or multiple of troughs, an additionalprofile concertina distortiOn occurs, resulting in a large increase inthe shear flexibility. A similar energy method is performed as for theprevious case, developing the same basic formula for the distortionaldeflection. A corresponding study is made for sinusoidally corrugatedsheeting.A nuMber of practical design factors have been examined - includingthe effect of longitudinally overlapping sheets, and purlin restraint onprofile distortion. For sheets spanning over rafters into differentshear fields, the expressions for shear flexibility have been modified.The strength of diaphragms has been investigated, especially withregard to fastening on two sides only, which includes the torsional andbending stiffness of laterally weak purlins. Diaphragm openings cause anincrease in the sheet flexibility and constrain purlins to follow theresulting displaced shape. Consequently locally high purlin bendingstresses and sheet-purlin forces may be generated, as revealed bydifferential equation and finite element studies.Corrugated sheeting has many applications in frameless structuressuch as folded plates and hyperbolic paraboloids. The flexibility and •strength expressions have been used to design a prototype three bay foldedplate roof Which utilizes specially pressed sheeting to reduce the sheardistortion component of roof deflection,The shear buckling strength of corrugated diaphragms is animpottant factor in such construction. For larger roof diaphragmswith only periodic intenrediate fixings to purlins, buckling may occurover the complete diaphragm depth rather than separately in each bay,and design tables are shown for this condition

Mortality associated with avian reovirus infection in a free-living magpie (Pica pica) in Great Britain

Avian reoviruses (ARVs) cause a range of disease presentations in domestic, captive and free-living bird species. ARVs have been reported as a cause of significant disease and mortality in free-living corvid species in North America and continental Europe. Until this report, there have been no confirmed cases of ARV-associated disease in British wild birds

Temporal Dynamics of Stomatal Behavior: Modeling and Implications for Photosynthesis and Water Use.

An analysis of stomatal behavior reveals the importance of modeling slow stomatal responses and the impacts on photosynthesis under dynamic light environments

Generationing development

The articles in this special issue present a persuasive case for accounts of development to recognise the integral and fundamental roles played by age and generation. While the past two decades have witnessed a burgeoning of literature demonstrating that children and youth are impacted by development, and that they can and do participate in development, the literature has tended to portray young people as a special group whose perspectives should not be forgotten. By contrast, the articles collected here make the case that age and generation, as relational constructs, cannot be ignored. Appropriating the term ‘generationing’, the editors argue that a variety of types of age relations profoundly structure the ways in which societies are transformed through development – both immanent processes of neoliberal modernisation and the interventions of development agencies that both respond and contribute to these. Drawing on the seven empirical articles, I attempt to draw some of the ideas together into a narrative that further argues the case for ‘generationing’ but also identifies gaps, questions and implications for further research

Sympatric and allopatric Alcolapia soda lake cichlid species show similar levels of assortative mating

Characterising reproductive barriers such as mating preferences within rapid evolutionary radiations is crucial for understanding the early stages of speciation. Cichlid fishes are well-known for their adaptive radiations and capacity for rapid speciation and as such we investigate assortative mating among Alcolapia species; a recent (<10,000 years), small adaptive radiation, endemic to the extreme soda lakes, Magadi (one species) and Natron (three species), in East Africa. In seminatural aquarium conditions, we observed both courtship and mate choice (tested by microsatellite paternity analysis) to be significantly assortative among the three sympatric Natron species in a three-way choice experiment. This was also the case between allopatric species from Natron and Magadi, as found in a two-way choice experiment. However, the proportion of disassortative matings was substantial in both of these experiments, with hybrids comprising 29% of offspring in sympatric species and 11.4% in allopatric species comparisons. . Previous work suggests that the Natron/Magadi split might not be much older than the radiation within Natron, so the similar rate of hybridisation in the allopatric comparison is surprising and inconsistent with predictions of reinforcement theory, which predicts a faster rate of accumulation of premating isolation in sympatry. The relatively weak assortative mating in sympatry suggests that additional reproductive barriers, such as microhabitat preferences or spatial structuring may contribute to genetic isolation in nature

Particle Kinematics in Horava-Lifshitz Gravity

We study the deformed kinematics of point particles in the Horava theory of gravity. This is achieved by considering particles as the optical limit of fields with a generalized Klein-Gordon action. We derive the deformed geodesic equation and study in detail the cases of flat and spherically symmetric (Schwarzschild-like) spacetimes. As the theory is not invariant under local Lorenz transformations, deviations from standard kinematics become evident even for flat manifolds, supporting superluminal as well as massive luminal particles. These deviations from standard behavior could be used for experimental tests of this modified theory of gravity.Comment: Added references, corrected a typing erro