196,748 research outputs found
Molecular characterization of ALDRXv4, an aldose reductase orthologue isolated from xerophyta viscosa, in response to abiotic stress
No full textIncludes bibliographical references (leaves 61-70)
Detection of change in shape and its relation to part structure
No full textUsing a change detection paradigm (Barenholtz, E., Cohen, E. H., Feldman, J., & Singh, M. (2003). Detection of change in shape: An advantage for concavities. Cognition, 89(1) 1-9), we measured sensitivity to the changes of shapes and in particular the difference between detecting a new convex or concave vertex. We conclude that concave vertices per se are not more salient, but changes in the sequence of convexities and concavities along a contour are salient. We argue that these changes are likely to signal a change in perceived part structure. © 2005 Elsevier B.V. All rights reserved
Editorial Current advances and challenges in understanding plant desiccation tolerance
Full text linkCITATION: Moore, J. P. & Farrant, J. M. 2015. Editorial : Current advances and challenges in understanding plant desiccation tolerance. Frontiers in Plant Science, 6:768, doi:10.3389/fpls.2015.00768.The original publication is available at www.frontiersin.orgNo abstracthttp://journal.frontiersin.org/article/10.3389/fpls.2015.00768/fullPublisher's versio
Cell wall involvement in desiccation tolerance in the resurrection plant Craterostigma wilmsii
No full textBibliography: leaves 92-129.Resurrection plants have the unique capacity to revive from an air-dried state. In order to cope with desiccation, resurrection plants have to overcome a number of stresses, mechanical stress being one. This occurs when the cytoplasm shrinks creating tension between the plasma membrane and the cell wall. In leaves of the Craterostigma species, an extensive shrinkage occurs during drying as well as a considerable wall folding. It is thought that this folding is a well controlled process rather than a simple collapse and that the ability of the wall to fold is important for the viability of the tissues upon drying. The aim of this study was to characterize the cell wall architecture and composition in hydrated and dry leaves of C. wilmsii using microscopical and biochemical techniques. Calcium and hormone contents were also determined during drying. The development of anhydrous fixation for microscopy confirmed the important folding of the wall previously observed with chemical fixation. Using immunocytochemical techniques and a variety of well characterized antibodies, the nature and composition of wall polymers was investigated. There was nothing unusual in the wall composition of C. wilmsii leaves as compared with other dicotyledonous plants. The results show a significant increase of the hemicellulosic polysaccharide xyloglucan and of the unesterified pectins during drying with levels declining again during rehydration. In contrast no increase was observed in others polysaccharides such as ß (1-4) galactans and methylesterified pectins. Biochemical analysis allowed further characterization of cell wall composition of C. wilmsii. The data demonstrate marked changes in the pectic and hemicellulosic wall fraction from dry plants compared to hydrated ones. The most conspicuous change was a decrease in glucose content in the hemicellulose fraction of the dry plant. Together these findings show that dehydration causes important alteration of polysaccharides content in the cell wall of C. wilmsii. Such modifications might be involved in the modulation of the mechanical properties of the wall during dehydration. Furthermore calcium ions content was shown to increase in the cell wall of dry plants, this could also have a role in stabilizing the wall architecture. All these alterations might be under the control of auxin, an hormone whose content was shown to increase during dehydration
Hayek, Mill and the liberal tradition
Full text linkThis book considers the relationship between Hayek and Mill, taking issues with Hayek s criticism of Mill and providing a broader perspective of the liberal tradition. Featuring contributions from the likes of Ross Emmett, Leon Montes and Robert Garnett, these chapters ask whether Hayek had an accurate reading of the ideas of Mill and Smith, as well as considering themes such as sympathy and analytical egalitarianism that play a large part in the liberal tradition, but less in work of Hayek These chapters argue that addition of these key ideas to the Hayekian corpus leads to a far broader understanding of the liberal tradition than that provided by Hayek. Contents: Introduction (Andrew Farrant). I. Hayek and the Liberal Tradition - Is Friedrich Hayek rowing Adam Smith s boat (Leon Montes); F. A. Hayek s Sympathetic Agents (David M. Levy and Sandra Peart); Discussion and the Evolution of Institutions in a Liberal Democracy: Frank Knight Joins the Debate (Ross Emmett). II. Pushing the Boundaries of the Liberal Tradition? - Hayek, Mill, and the Problem of Institutional Change? (Andrew Farrant); A Socialist Spontaneous Order (Theodore A. Burczak); Hayek and Philanthropy: A Classical Liberal Road Not (Yet) Taken (Robert Garnett)
A cell boundary element method applied to laminar vortex-shedding from arrays of cylinders in various arrangements
No full textA cell boundary element method is used to solve the two-dimensional incompressible Navier–Stokes equation for vortex-shedding flows around arrays of cylinders. The method is a hybrid scheme using a boundary element method in each fluid cell discretization with a finite element procedure to solve for the global fluid problem. Computations are presented of two-dimensional flow characteristics and interactive forces associated with flows around four equispaced cylinders of equal diameter, and two cylinders, one with circular cross-section and the other elliptical. It was found that behaviour such as in-phase vortex-shedding, anti-phase vortex shedding and synchronized vortex shedding, which are well-known characteristics for flows past arrangements of two circular cylinders, were also present in these more complicated flows. The application of the cell boundary element method to these flow problems, using an unstructured fluid domain mesh idealization, proved straightforward and required no modification for variation of the number of bodies or their shape
Cloning and characterisation of LEA1-EM genes in the resurrection plant, Xerophyta humilis
No full textIncludes abstract.Includes bibliographical references (leaves 75-86).The presence and expressIon patterns of orthologues of LEA group 1 genes has been characterised in the resurrection plant, Xerophyta humilis. The group I LEAs (Em I and Em6) were first identified as proteins that were abundantly and specifically expressed during the desiccation and germination phase of angiosperm seed development. The group I LEA genes are characterised by the presence of one or more tandemly repeated 20-amino acid motifs that are particularly rich in Gly residues
A cell boundary element method applied to laminar vortex shedding from circular cylinders
Full text linkThe two-dimensional unsteady incompressible Navier–Stokes equations are solved for flows around arrangements of circular cylinders at Reynolds number 100 and 200. A hybrid boundary element/finite element method is used to discretise the spatial domain together with a second order implicit finite difference approximation in time. The numerical scheme of study is validated for a uniform stream past an isolated circular cylinder by comparing findings with experimental and numerical studies. Both steady state and time dependent solutions were predicted with good agreement. The numerical approach, known here as the cell boundary element method (cell BEM), was also used to solve flows around two cylinders of equal diameter side by side and in tandem. It was found that no modifications to the method were needed to compute the flow field for these connected domains. In-phase and anti-phase vortex shedding modes were found to exist in the flow simulation. These simulations were in excellent agreement with phenomena observed in experiments. Particle simulations, generated from the cell BEM velocity fields, were found to have great similarity with smoke visualisations from experiment
Investigating the mechanisms of desiccation tolerance in the resurrection plant, myrothamnus flabellifolius (WELW)
No full textBiliography : leaves 162-184.Resurrection plants, including Myrothamnus flabellifolius, grow in shallow soil upon rocky outcrops where they experience regular periods of water stress. Associated with this is light stress. The presence of light under water limiting conditions can result in photo-oxidation which causes damage to plant tissues. M flabellifolius is a homoichlorophyllous plant and thus retains chlorophyll during desiccation. The mechanisms whereby this plant prevents photo-oxidation damage are not known and thus one of the objectives of this study was to characterise the chloroplasts and the changes they undergo during dehydration. It was shown that chloroplasts from M flabellifolius could only be isolated using trehalose gradients (instead of sucrose gradients) and were found to have a higher buoyant density than chloroplasts isolated from another resurrection plant, Craterostigma wilmsii. The latter had the same buoyant density as those isolated from the desiccation sensitive plant Pisum sativum. The increased buoyant density in M flabellifolius was ascribed to the unusual ultrastructure of the thylakoid membranes. The latter have a staggered conformation (staircase arrangement) rather than the discrete granal and intergranal conformation found in most plants
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