The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Lloyd Donaldson - One of the best experts on this subject based on the ideXlab platform.
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Chemical Characterisation of Compression Wood in Pinus Radiata
2020Co-Authors: Bernadette Nanayakkara, Merilyn Manley-harris, Ian D. Suckling, Lloyd DonaldsonAbstract:To determine how the chemistry of Compression Wood varies in Pinus radiata, we have studied summative composition and lignin structure in a range of different Compression Wood and opposite Wood samples. Wood anatomy was used to characterise the Compression Wood severity. Lignin structure was studied by three methods based on thioacidolysis. Overall the results showed that, as the severity of Compression Wood changed, progressively from opposite through mild to severe, all features commonly associated with Compression Wood changed concurrently. In particular, galactose levels increased and glucose and mannose levels decreased, lignin content increased and the lignin became more condensed. Levels of p-hydroxyphenyl β-O-4 units increased while guaiacyl β-O-4 units decreased with increasing Compression Wood severity. Similar chemical compositional and lignin structural changes were seen in stems, branches and young Wood upon Compression Wood formation.
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Xylem parenchyma cell walls lack a gravitropic response in conifer Compression Wood.
Planta, 2015Co-Authors: Lloyd Donaldson, Bernadette Nanayakkara, Ksenija Radotić, D. Djikanovic-golubović, Aleksandra Mitrovic, J. Bogdanović Pristov, J. Simonović Radosavljević, Aleksandar KalauziAbstract:Main conclusion Cell wall fluorescence and immunocytochemistry demonstrate that xylem parenchyma cell walls do not show changes in structure and composition related to gravitropic response comparable to those of tracheids, even when they have lignified secondary cell walls. Tracheid cell walls in Compression Wood have altered composition and structure which generates the strain responsible for correction of stem lean as part of the gravitropic response of Woody plants. Xylem parenchyma cell walls vary among conifer species and can be lignified secondary walls (spruce) or unlignified primary walls (pine). It can be expected that xylem parenchyma with lignified secondary cell walls might show features of Compression Wood comparable to those of tracheids that have a similar type of cell wall. A comparison of xylem parenchyma cell walls in normal and Compression Wood in species with lignified and non-lignified parenchyma cell walls provides a unique opportunity to understand the process of reaction Wood formation in conifers. Using both UV/visible fluorescence microscopy of cell wall fluorophores and immunocytochemistry of galactan and mannan epitopes, we demonstrate that xylem parenchyma cell walls do not show the changes in composition and structure typical of Compression Wood tracheids. Adjacent cells of different types but with similar cell wall structure can undergo cell wall developmental changes related to support or defence functions independent of their neighbours. Tracheids are sensitive to gravitropic signals while xylem parenchyma cells are not.
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fluorescence lifetime imaging of lignin autofluorescence in normal and Compression Wood
Journal of Microscopy, 2013Co-Authors: Lloyd Donaldson, Ksenija RadoticAbstract:Summary Wood cell walls fluoresce as a result of UV and visible light excitation due to the presence of lignin. Fluorescence spectroscopy has revealed characteristic spectral differences in various Wood types, notably normal and Compression Wood. In order to extend this method of characterising cell walls we examined the fluorescence lifetime of Wood cell walls using TCSPC (Time-Correlated Single Photon Counting) as a method of potentially detecting differences in lignin composition and measuring the molecular environment within cell walls. The fluorescence decay curves of both normal and Compression Wood from pine contain three exponential decay components with a mean lifetime of τm = 473 ps in normal Wood and 418 ps in Compression Wood. Lifetimes are spatially resolved to different cell wall layers or cell types where individual lifetimes are shown to have a log-normal distribution. The differences in fluorescence lifetime observed in pine Compression Wood compared to normal Wood, are associated with known differences in cell wall composition such as increased p-hydroxyphenyl content in lignin as well as novel deposition of β(1,4)-Galactan. Our results indicate increased deposition of lignin fluorophores with shorter lifetimes in the outer secondary wall of Compression Wood. We have demonstrated the usefulness of fluorescence lifetime imaging for characterising Wood cell walls, offering some advantages over conventional fluorescence imaging/spectroscopy. For example, we have measured significant changes in fluorescence lifetime resulting from changes to lignin composition as a result of Compression Wood formation that complement similar changes in fluorescence intensity.
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formation and structure of Compression Wood
2013Co-Authors: Lloyd Donaldson, Adya P SinghAbstract:Compression Wood is a hard, dark-coloured Wood typically found on the lower side of leaning stems and branches in conifers, Taxus and Ginkgo. This reaction Wood is the result of the geotropic response of the tree, usually resulting from stem lean or the effect of stem flexing caused by wind. Compression Wood is characterised by anatomical and compositional features that vary in a continuum between normal Wood and severe Compression Wood. The main characteristics of Compression Wood are altered cell wall structure especially increased microfibril orientation, presence of helical cavities and intercellular spaces and increased lignification associated with significant amounts of (1 → 4)-β-galactan in the secondary wall. This chapter briefly reviews the formation, structure and composition of Compression Wood with an emphasis on recent advances.
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quantification of Compression Wood severity in tracheids of pinus radiata d don using confocal fluorescence imaging and spectral deconvolution
Journal of Structural Biology, 2010Co-Authors: Lloyd Donaldson, Ksenija Radotic, Aleksandar Kalauzi, Daniela Djikanovic, Milorad JeremicAbstract:Confocal fluorescence microscopy was used to examine the spectral characteristics of lignin autofluorescence in secondary cell walls of normal and Compression Wood from Pinus radiata. Using UV excitation, fluorescence spectra of normal and Compression Wood sections showed significant differences, especially in the outer secondary cell wall of tracheids, with a shift in maxima from violet to blue wavelengths between normal and Compression Wood. A comparison of normal Wood, mild and severe Compression Wood, showed that the wavelength shift was intermediate in the mild Compression Wood compared to the severe Compression Wood, thus offering the possibility of quantifying the severity by measuring ratios of fluorescence at violet and blue wavelengths. Fluorescence induced by blue light, rather than UV, was less well differentiated amongst Wood types. Spectral deconvolution indicated the presence of a minimum of five discrete lignin fluorophores in the cell walls of both normal and Compression Wood tracheids. Comparison with lignin model compounds suggest that the wavelength shift may correspond in part to increased levels of p-hydroxy type lignin in the Compression Wood samples. The combination of confocal fluorescence imaging and related spectral deconvolution therefore offers a novel technique for characterising cell wall lignin in situ.
Clemens M Altaner - One of the best experts on this subject based on the ideXlab platform.
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measuring Compression Wood severity in spruce
Wood Science and Technology, 2009Co-Authors: Paul J Mclean, Clemens M Altaner, Elena N Tokareva, Janet C T Wong, Adrian Ilie Hapca, Michael C JarvisAbstract:As the severity of Compression Wood influences the mechanical and chemical properties of Wood it is desirable to be able to measure Compression Wood severity. However, so far no satisfactory method has been reported in the literature. Here we describe how scanning FTIR micro-spectroscopy can be employed to achieve CW severity measurements on increment cores of Norway spruce (Picea abies (L. Karst.) and Sitka spruce (Picea sitchensis (Bong.) Carriere). Radial Wood strips were converted into sawdust by a process that maintained their spatial orientation. Samples prepared in this way were scanned with an FTIR-microscope in reflective mode and from the spectra obtained a CW-indicator was calculated representing aromatic and carboxyl signals. This FTIR CW-indicator correlated well with alternative CW identification techniques (namely microfibril angle, transmitted light and immunolabelling of beta 1–4 galactan), which have been used to validate the method. Repeatability of the measurements was good and no systematic difference between spruce species was found. The achievable resolution of the measurements was of sub-mm order. The CW indicator described offers the opportunity to correlate CW severity with mechanical Wood properties in spruce.
Kristofer E Gamstedt - One of the best experts on this subject based on the ideXlab platform.
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modelling of the hygroelastic behaviour of normal and Compression Wood tracheids
Journal of Structural Biology, 2014Co-Authors: Thomas Joffre, Stig L. Bardage, Cristian R Neagu, Kristofer E GamstedtAbstract:Compression Wood conifer tracheids show different swelling and stiffness properties than those of usual normal Wood, which has a practical function in the living plant: when a conifer shoot is moved from its vertical position, Compression Wood is formed in the under part of the shoot. The growth rate of the Compression Wood is faster than in the upper part resulting in a renewed horizontal growth. The actuating and load-carrying function of the Compression Wood is addressed, on the basis of its special ultrastructure and shape of the tracheids. As a first step, a quantitative model is developed to predict the difference of moisture-induced expansion and axial stiffness between normal Wood and Compression Wood. The model is based on a state space approach using concentric cylinders with anisotropic helical structure for each cell-wall layer, whose hygroelastic properties are in turn determined by a self-consistent concentric cylinder assemblage of the constituent Wood polymers. The predicted properties compare well with experimental results found in the literature. Significant differences in both stiffness and hygroexpansion are found for normal and Compression Wood, primarily due to the large difference in microfibril angle and lignin content. On the basis of these numerical results, some functional arguments for the reason of high microfibril angle, high lignin content and cylindrical structure of Compression Wood tracheids are supported. (C) 2013 Elsevier Inc. All rights reserved.
Ksenija Radotic - One of the best experts on this subject based on the ideXlab platform.
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fluorescence lifetime imaging of lignin autofluorescence in normal and Compression Wood
Journal of Microscopy, 2013Co-Authors: Lloyd Donaldson, Ksenija RadoticAbstract:Summary Wood cell walls fluoresce as a result of UV and visible light excitation due to the presence of lignin. Fluorescence spectroscopy has revealed characteristic spectral differences in various Wood types, notably normal and Compression Wood. In order to extend this method of characterising cell walls we examined the fluorescence lifetime of Wood cell walls using TCSPC (Time-Correlated Single Photon Counting) as a method of potentially detecting differences in lignin composition and measuring the molecular environment within cell walls. The fluorescence decay curves of both normal and Compression Wood from pine contain three exponential decay components with a mean lifetime of τm = 473 ps in normal Wood and 418 ps in Compression Wood. Lifetimes are spatially resolved to different cell wall layers or cell types where individual lifetimes are shown to have a log-normal distribution. The differences in fluorescence lifetime observed in pine Compression Wood compared to normal Wood, are associated with known differences in cell wall composition such as increased p-hydroxyphenyl content in lignin as well as novel deposition of β(1,4)-Galactan. Our results indicate increased deposition of lignin fluorophores with shorter lifetimes in the outer secondary wall of Compression Wood. We have demonstrated the usefulness of fluorescence lifetime imaging for characterising Wood cell walls, offering some advantages over conventional fluorescence imaging/spectroscopy. For example, we have measured significant changes in fluorescence lifetime resulting from changes to lignin composition as a result of Compression Wood formation that complement similar changes in fluorescence intensity.
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quantification of Compression Wood severity in tracheids of pinus radiata d don using confocal fluorescence imaging and spectral deconvolution
Journal of Structural Biology, 2010Co-Authors: Lloyd Donaldson, Ksenija Radotic, Aleksandar Kalauzi, Daniela Djikanovic, Milorad JeremicAbstract:Confocal fluorescence microscopy was used to examine the spectral characteristics of lignin autofluorescence in secondary cell walls of normal and Compression Wood from Pinus radiata. Using UV excitation, fluorescence spectra of normal and Compression Wood sections showed significant differences, especially in the outer secondary cell wall of tracheids, with a shift in maxima from violet to blue wavelengths between normal and Compression Wood. A comparison of normal Wood, mild and severe Compression Wood, showed that the wavelength shift was intermediate in the mild Compression Wood compared to the severe Compression Wood, thus offering the possibility of quantifying the severity by measuring ratios of fluorescence at violet and blue wavelengths. Fluorescence induced by blue light, rather than UV, was less well differentiated amongst Wood types. Spectral deconvolution indicated the presence of a minimum of five discrete lignin fluorophores in the cell walls of both normal and Compression Wood tracheids. Comparison with lignin model compounds suggest that the wavelength shift may correspond in part to increased levels of p-hydroxy type lignin in the Compression Wood samples. The combination of confocal fluorescence imaging and related spectral deconvolution therefore offers a novel technique for characterising cell wall lignin in situ.
Milorad Jeremic - One of the best experts on this subject based on the ideXlab platform.
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quantification of Compression Wood severity in tracheids of pinus radiata d don using confocal fluorescence imaging and spectral deconvolution
Journal of Structural Biology, 2010Co-Authors: Lloyd Donaldson, Ksenija Radotic, Aleksandar Kalauzi, Daniela Djikanovic, Milorad JeremicAbstract:Confocal fluorescence microscopy was used to examine the spectral characteristics of lignin autofluorescence in secondary cell walls of normal and Compression Wood from Pinus radiata. Using UV excitation, fluorescence spectra of normal and Compression Wood sections showed significant differences, especially in the outer secondary cell wall of tracheids, with a shift in maxima from violet to blue wavelengths between normal and Compression Wood. A comparison of normal Wood, mild and severe Compression Wood, showed that the wavelength shift was intermediate in the mild Compression Wood compared to the severe Compression Wood, thus offering the possibility of quantifying the severity by measuring ratios of fluorescence at violet and blue wavelengths. Fluorescence induced by blue light, rather than UV, was less well differentiated amongst Wood types. Spectral deconvolution indicated the presence of a minimum of five discrete lignin fluorophores in the cell walls of both normal and Compression Wood tracheids. Comparison with lignin model compounds suggest that the wavelength shift may correspond in part to increased levels of p-hydroxy type lignin in the Compression Wood samples. The combination of confocal fluorescence imaging and related spectral deconvolution therefore offers a novel technique for characterising cell wall lignin in situ.