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1.
Li-Fen Hung Ching-Chu Tsai Shiang-Jiuun Chen Yan-San Huang Ling-Long Kuo-Huang 《Trees - Structure and Function》2016,30(3):609-625
Key message
Stem reorientation is critical to tree survival. With anatomical observation and strain measurement, the tension wood formation and biomechanical behavior were studied to gain insights into tree uprighting process.Abstract
Tension wood plays a role in maintaining the mechanical stability of angiosperm trees. Both biological and physical aspects of tension wood are essential in understanding the mechanism of trunk or branch reorientation. In this study, we worked on both tension wood formation and its biomechanical function in artificially inclined 2-year-old Koelreuteria henryi seedlings. The tension wood formation and reorientation process of the trunk last for about 3 months. With pinning method, we confirmed that at the beginning of inclination the cambial zone including the vascular cambium and the developing normal wood fibers on the upper side of the inclined trunk perceives the onset of mechanical change and starts to produce G-fibers that generate a strong contractile released growth strain (RGS) for gravitropic correction. Stronger contractile RGS and more tension wood were found at the trunk base than at the half-height, suggesting that the trunk base plays a key role in trunk uprighting of K. henryi seedlings. The eccentric cambial growth in the tension wood side increases the efficiency of gravitropic correction and the compressive strains measured in the opposite wood of some inclined seedlings also help the upright movement.2.
Guillaume Pot Catherine Coutand Evelyne Toussaint Jean-Benoît Le Cam Marc Saudreau 《Trees - Structure and Function》2014,28(4):1235-1248
Key message
The developed model of gravitropism takes non-instantaneous maturation of wood into account which enabled to correctly simulate different gravitropic phases and realistic internal stress profiles.Abstract
A new biomechanical model of tree movement in relation to gravity (gravitropism) is proposed in this study. The modelling of the progressive maturation of wood cells is taken into account, as well as spatio-temporal variations in maturation strains (MS) and mechanical properties. MS were identified using an inverse method that allows the model to fit the gravitropic reaction observed experimentally. For this purpose, the curvature during righting movement, the geometry and the mass distribution of a two-year-old poplar tree was measured. The identified MS are higher than expected, which shows the underestimation of MS by usual measurements. By using the same mechanical parameters and MS as an input, the model gives satisfying results in terms of shape modelling for different trees up to 32 days after tree tilting. The model is able to simulate the latency phase observed in the tree righting movement, and the internal stress profile in the trunk is realistic (low compressive value in the central part of the trunk and zero stress in newly formed cells). The next development of the model will aim to simulate the end of the gravitropic phase in relation with the regulation of MS by the tree. 相似文献3.
Catherine Coutand Malia Chevolot Andr�� Lacointe Nick Rowe Ivan Scotti 《Annals of botany》2010,105(2):341-347
Background and Aims
In rain forests, sapling survival is highly dependent on the regulation of trunk slenderness (height/diameter ratio): shade-intolerant species have to grow in height as fast as possible to reach the canopy but also have to withstand mechanical loadings (wind and their own weight) to avoid buckling. Recent studies suggest that mechanosensing is essential to control tree dimensions and stability-related morphogenesis. Differences in species slenderness have been observed among rainforest trees; the present study thus investigates whether species with different slenderness and growth habits exhibit differences in mechanosensitivity.Methods
Recent studies have led to a model of mechanosensing (sum-of-strains model) that predicts a quantitative relationship between the applied sum of longitudinal strains and the plant''s responses in the case of a single bending. Saplings of five different neotropical species (Eperua falcata, E. grandiflora, Tachigali melinonii, Symphonia globulifera and Bauhinia guianensis) were subjected to a regimen of controlled mechanical loading phases (bending) alternating with still phases over a period of 2 months. Mechanical loading was controlled in terms of strains and the five species were subjected to the same range of sum of strains. The application of the sum-of-strain model led to a dose–response curve for each species. Dose–response curves were then compared between tested species.Key Results
The model of mechanosensing (sum-of-strain model) applied in the case of multiple bending as long as the bending frequency was low. A comparison of dose–response curves for each species demonstrated differences in the stimulus threshold, suggesting two groups of responses among the species. Interestingly, the liana species B. guianensis exhibited a higher threshold than other Leguminosae species tested.Conclusions
This study provides a conceptual framework to study variability in plant mechanosensing and demonstrated interspecific variability in mechanosensing.Key words: Mechanosensing, interspecific variability, trees, lianas, rain forest, neotropical species, bending, biomechanics, Bauhinia, Eperua, Symphonia, Tachigali 相似文献4.
Severino A Lucena Leile S Lima Luís SA Cordeiro Jr Celso Sant’Anna Reginaldo Constantino Patricia Azambuja Wanderley de Souza Eloi S Garcia Fernando A Genta 《Biotechnology for biofuels》2011,4(1):1-9
Background
Short rotation coppice willow is a potential lignocellulosic feedstock in the United Kingdom and elsewhere; however, research on optimising willow specifically for bioethanol production has started developing only recently. We have used the feedstock Salix viminalis × Salix schwerinii cultivar 'Olof' in a three-month pot experiment with the aim of modifying cell wall composition and structure within the stem to the benefit of bioethanol production. Trees were treated for 26 or 43 days with tension wood induction and/or with an application of the cellulose synthesis inhibitor 2,6-dichlorobenzonitrile that is specific to secondary cell walls. Reaction wood (tension and opposite wood) was isolated from material that had received the 43-day tension wood induction treatment.Results
Glucan content, lignin content and enzymatically released glucose were assayed. All measured parameters were altered without loss of total stem biomass yield, indicating that enzymatic saccharification yield can be enhanced by both alterations to cell wall structure and alterations to absolute contents of either glucan or lignin.Conclusions
Final glucose yields can be improved by the induction of tension wood without a detrimental impact on biomass yield. The increase in glucan accessibility to cell wall degrading enzymes could help contribute to reducing the energy and environmental impacts of the lignocellulosic bioethanol production process. 相似文献5.
6.
J. N. Axelson A. Bast R. Alfaro D. J. Smith H. Gärtner 《Trees - Structure and Function》2014,28(6):1837-1846
Key message
An outbreak of the western spruce budworm temporarily modifies cellular wood anatomy of stem wood in natural and mature Douglas-fir stands impacting wood quality properties.Abstract
Western spruce budworm (Choristoneura occidentalis Freeman) is a widespread and destructive defoliator of commercially important coniferous forests in western North America. In British Columbia, Canada, Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] is the most important and widely distributed host. Permanent sample plots were established at a number of locations in southern interior at the beginning of a severe western spruce budworm outbreak in the 1970s. Two of the sites were sampled in 2012 to determine whether modifications had occurred in the anatomical characteristics of stem wood formed during outbreak years. We determined that rings formed during the western spruce budworm 1976–1980 outbreak had a significantly lower proportion of latewood, reduced mean cell wall thickness and smaller radial cell diameters. While the cellular characteristics of the earlywood remained fairly constant, significant reductions in lumen area occurred in 1978 and 1979 at each site. Our study shows that western spruce budworm outbreaks not only reduce annual radial growth, but also temporarily modify cellular characteristics in latewood cells, which has implications for wood density and quality in Douglas-fir. 相似文献7.
Lorenzo Rossi Luca Sebastiani Roberto Tognetti Riccardo d’Andria Giovanni Morelli Paolo Cherubini 《Plant and Soil》2013,372(1-2):567-579
Background and Aims
Olive tree (Olea europaea L.) is a drought-tolerant tree species cultivated in Mediterranean-type environments. Although it is tolerant to drought, dry conditions decrease its productivity. A thorough analysis of the hydraulic architecture and wood anatomical plasticity, as well as of their physiological significance, is needed to understand how olive trees will adapt to the predicted increase in frequency and severity of drought in the Mediterranean region.Methods
Dendrochronological, stable isotopic (δ13C, δ18O) and wood anatomical analyses were applied to understand how different water availability can affect wood stem structure and function, in rainfed and irrigated at 100 % of crop evapotranspiration (ETc) olive trees in an experimental orchard close to Benevento (Italy) from 1992 to 2009.Results
Dendrochronological data indicate that cross-dating and synchronization of ring-width time series in olive tree is possible. After the start of irrigation, significantly more negative δ13C and lower δ18O values were recorded in irrigated trees indicating higher stomatal conductance and transpiration rates. Increased water balance induced the formation of a higher number of vessels with higher diameter.Conclusions
Water balance variations affected wood anatomy and isotopic composition. Anatomical analyses detected structural and functional adjustments in rainfed trees that produced more vessels with lower diameter to prevent cavitation. Isotopic analyses confirmed that irrigated trees continuously showed enhanced transpiration rates. 相似文献8.
Yi-Shiuan Lin Arthur Y Shaw Shi-Gang Wang Chia-Chen Hsu I-Wen Teng Min-Jen Tseng Tim HM Huang Ching-Shih Chen Yu-Wei Leu Shu-Huei Hsiao 《Journal of biomedical science》2011,18(1):1-8
Background
The extracellular calcium-sensing receptor (CaSR) belongs to family C of the G protein coupled receptors. Whether the CaSR is expressed in the pulmonary artery (PA) is unknown.Methods
The expression and distribution of CaSR were detected by RT-PCR, Western blotting and immunofluorescence. PA tension was detected by the pulmonary arterial ring technique, and the intracellular calcium concentration ([Ca2+]i) was detected by a laser-scanning confocal microscope.Results
The expressions of CaSR mRNA and protein were found in both rat pulmonary artery smooth muscle cells (PASMCs) and PAs. Increased levels of [Ca2+]o (extracellular calcium concentration) or Gd3+ (an agonist of CaSR) induced an increase of [Ca2+]i and PAs constriction in a concentration-dependent manner. In addition, the above-mentioned effects of Ca2+ and Gd3+ were inhibited by U73122 (specific inhibitor of PLC), 2-APB (specific antagonist of IP3 receptor), and thapsigargin (blocker of sarcoplasmic reticulum calcium ATPase).Conclusions
CaSR is expressed in rat PASMCs, and is involved in regulation of PA tension by increasing [Ca2+]i through G-PLC-IP3 pathway. 相似文献9.
Karin Höglmeier Gabriele Weber-Blaschke Klaus Richter 《The International Journal of Life Cycle Assessment》2014,19(10):1755-1766
Purpose
A cascading utilization of resources is encouraged especially by legislative bodies. However, only few consecutive assessments of the environmental impacts of cascading are available. This study provides answers to the following questions for using recovered wood as a secondary resource: (1) Does cascading decrease impacts on the environment compared to the use of primary wood resources? (2) What aspects of the cascading system are decisive for the life cycle assessment (LCA) results?Methods
We conducted full LCAs for cascading utilization options of waste wood and compared the results to functionally equivalent products from primary wood, thereby focusing on the direct effects cascading has on the environmental impacts of the systems. In order to compare waste wood cascading to the use of primary wood with LCA, a functional equivalence of the systems has to be achieved. We applied a system expansion approach, considering different options for providing the additionally needed energy for the cascading system.Results and discussion
We found that the cascading systems create fewer environmental impacts than the primary wood systems, if system expansion is based on wood energy. The most noticeable advantages were detected for the impact categories of land transformation and occupation and the demand of primary energy from renewable sources. The results of the sensitivity analyses indicate that the advantage of the cascading system is robust against the majority of considered factors. Efficiency and the method of incineration at the end of life do influence the results.Conclusions
To maximize the benefits and minimize the associated environmental impacts, cascading proves to be a preferable option of utilizing untreated waste wood. 相似文献10.
11.
Abraham Morales-Cruz Rosa Figueroa-Balderas Jadran F. García Eric Tran Philippe E. Rolshausen Kendra Baumgartner Dario Cantu 《BMC microbiology》2018,18(1):214
Background
DNA metabarcoding, commonly used in exploratory microbial ecology studies, is a promising method for the simultaneous in planta-detection of multiple pathogens associated with disease complexes, such as the grapevine trunk diseases. Profiling of pathogen communities associated with grapevine trunk diseases is particularly challenging, due to the presence within an individual wood lesion of multiple co-infecting trunk pathogens and other wood-colonizing fungi, which span a broad range of taxa in the fungal kingdom. As such, we designed metabarcoding primers, using as template the ribosomal internal transcribed spacer of grapevine trunk-associated ascomycete fungi (GTAA) and compared them to two universal primer widely used in microbial ecology.Results
We first performed in silico simulations and then tested the primers by high-throughput amplicon sequencing of (i) multiple combinations of mock communities, (ii) time-course experiments with controlled inoculations, and (iii) diseased field samples from vineyards under natural levels of infection. All analyses showed that GTAA had greater affinity and sensitivity, compared to those of the universal primers. Importantly, with GTAA, profiling of mock communities and comparisons with shotgun-sequencing metagenomics of field samples gave an accurate representation of genera of important trunk pathogens, namely Phaeomoniella, Phaeoacremonium, and Eutypa, the abundances of which were over- or under-estimated with universal primers.Conclusions
Overall, our findings not only demonstrate that DNA metabarcoding gives qualitatively and quantitatively accurate results when applied to grapevine trunk diseases, but also that primer customization and testing are crucial to ensure the validity of DNA metabarcoding results.12.
A. Galambos A. Zok A. Kuczmog R. Oláh P. Putnoky W. Ream E. Szegedi 《Plant cell reports》2013,32(11):1751-1757
Key message
Grapevine rootstock transformed with an Agrobacterium oncogene-silencing transgene was resistant to certain Agrobacterium strains but sensitive to others. Thus, genetic diversity of Agrobacterium oncogenes may limit engineering crown gall resistance.Abstract
Crown gall disease of grapevine induced by Agrobacterium vitis or Agrobacterium tumefaciens causes serious economic losses in viticulture. To establish crown gall-resistant lines, somatic proembryos of Vitis berlandieri × V. rupestris cv. ‘Richter 110’ rootstock were transformed with an oncogene-silencing transgene based on iaaM and ipt oncogene sequences from octopine-type, tumor-inducing (Ti) plasmid pTiA6. Twenty-one transgenic lines were selected, and their transgenic nature was confirmed by polymerase chain reaction (PCR). These lines were inoculated with two A. tumefaciens and three A. vitis strains. Eight lines showed resistance to octopine-type A. tumefaciens A348. Resistance correlated with the expression of the silencing genes. However, oncogene silencing was mostly sequence specific because these lines did not abolish tumorigenesis by A. vitis strains or nopaline-type A. tumefaciens C58. 相似文献13.
Comparative hybridization reveals extensive genome variation in the AIDS-associated pathogen Cryptococcus neoformans 总被引:1,自引:0,他引:1
Background
Genome variability can have a profound influence on the virulence of pathogenic microbes. The availability of genome sequences for two strains of the AIDS-associated fungal pathogen Cryptococcus neoformans presented an opportunity to use comparative genome hybridization (CGH) to examine genome variability between strains of different mating type, molecular subtype, and ploidy.Results
Initially, CGH was used to compare the approximately 100 kilobase MAT a and MATα mating-type regions in serotype A and D strains to establish the relationship between the Log2 ratios of hybridization signals and sequence identity. Subsequently, we compared the genomes of the environmental isolate NIH433 (MAT a) and the clinical isolate NIH12 (MATα) with a tiling array of the genome of the laboratory strain JEC21 derived from these strains. In this case, CGH identified putative recombination sites and the origins of specific segments of the JEC21 genome. Similarly, CGH analysis revealed marked variability in the genomes of strains representing the VNI, VNII, and VNB molecular subtypes of the A serotype, including disomy for chromosome 13 in two strains. Additionally, CGH identified differences in chromosome content between three strains with the hybrid AD serotype and revealed that chromosome 1 from the serotype A genome is preferentially retained in all three strains.Conclusion
The genomes of serotypes A, D, and AD strains exhibit extensive variation that spans the range from small differences (such as regions of divergence, deletion, or amplification) to the unexpected disomy for chromosome 13 in haploid strains and preferential retention of specific chromosomes in naturally occurring diploids. 相似文献14.
Derek J Sloan Andrew Nicolson Alastair RO Miller Nick J Beeching Mike BJ Beadsworth 《Journal of medical case reports》2008,2(1):1-5
Introduction
Electrocardiogram (ECG) abnormalities in patients with blunt chest trauma are diverse and non-specific, but may be indicative of potentially life-threatening conditions.Case presentation
We report a rare case of pneumopericardium with extreme ECG abnormalities after blunt chest trauma in a 22-year-old male. The diagnosis was confirmed using computed tomography (CT) scanning. The case is discussed, together with its differential diagnosis and the aetiology of pneumopericardium and tension pneumopericardium.Conclusion
Pneumopericardium should be distinguished from other pathologies such as myocardial contusion and myocardial infarction because of the possible development of tension pneumopericardium. Early CT scanning is important in the evaluation of blunt chest trauma. 相似文献15.
Gregory J Lehman Trish Gordon Jo Langley Patricia Pemrose Sara Tregaskis 《Dynamic medicine : DM》2005,4(1):6
Background
The addition of Swiss balls to conventional exercise programs has recently been adopted. Swiss balls are an unstable surface which may result in an increased need for force output from trunk muscles to provide adequate spinal stability or balance. The aim of the study was to determine whether the addition of a Swiss ball to upper body strength exercises results in consistent increases in trunk muscle activation levels.Methods
The myoelectric activity of four trunk muscles was quantified during the performance of upper body resistance exercises while seated on both a stable (exercise bench) and labile (swiss ball) surface. Participants performed the supine chest press, shoulder press, lateral raise, biceps curl and overhead triceps extension. A repeated measures ANOVA with post-hoc Tukey test was used to determine the influence of seated surface type on muscle activity for each muscle.Results & Discussion
There was no statistically significant (p < .05) difference in muscle activity between surface conditions. However, there was large degree of variability across subjects suggesting that some individuals respond differently to surface stability. These findings suggest that the incorporation of swiss balls instead of an exercise bench into upper body strength training regimes may not be justified based only on the belief that an increase spinal stabilizing musculature activity is inherent. Biomechanically justified ground based exercises have been researched and should form the basis for spinal stability training as preventative and therapeutic exercise training regimes.Conclusion
Selected trunk muscle activity during certain upper limb strength training exercises is not consistently influenced by the replacement of an exercise bench with a swiss ball.16.
Key message
Large aerial roots grow out from the branches of injured Dracaena draco trees. They integrate with the trunk or cause the branches to break off the tree and deform it.Abstract
Dracaena draco, the dragon tree, is an iconic monocot of the Canary Islands with a tree-like growth habit and some distinctive features that are unique in the plant kingdom. We report about the massive aerial roots in this tree. They appear on trees that are injured or under environmental stress and affect growth form and the whole life of the plant. We analysed the growth of these roots and tested our findings in experiments on plants. Clusters of these roots emerge from the bases of the lowest branches and growing down they may reach the soil. Descending along the trunk, they cling tightly to the trunk, integrate with it and contribute to its radial growth. This may explain (1) why the trunk of a mature D. draco tree looks fibrous, as if made of many individual strands, and (2) how some trees reach enormous radial dimensions. Alternately, a large, 2–5 m high, multi-segmented branch with aerial roots at its base, may break off the tree and grow on its own, as a mammoth off-cut, perhaps the largest known in the plant kingdom. This detachment would cause a significant reduction in the size of the crown and deform its original, highly organized pattern of branching. In the extreme condition this may result in the destruction of the mother plant. 相似文献17.
Key message
Mongolian pine in a sparse wood grassland stand maintains a relatively stable state under the current water conditions by varying its water use sources at a constant water use efficiency.Abstract
In a semi-arid sandy ecosystem, water is one of the most important factors influencing survival and growth of Mongolian pine in a sparse wood grassland (MPSWG); however, the mechanism of water utilization of MPSWG has been yet poorly understood. Stable isotopes of hydrogen and oxygen of water in xylem, soil, precipitation and groundwater were analyzed to determine water sources used by MPSWG from April to October in two consecutive years (1.2 and 0.89 times of long-term annual precipitation in 2010 and 2011, respectively). Needles δ13C were measured simultaneously to assess water use efficiency. Results showed that MPSWG used soil water (sampling depth up to 60 cm) between April and July, and in October. However, water sources used by MPSWG exhibited significant differences in August and September between 2 years. In 2010, MPSWG only utilized soil water in August and September due to higher soil water content, but they used both soil water and groundwater in 2011 because of lower soil water availability, suggesting that MPSWG could utilize groundwater to replenish soil water deficiency. No significant differences in mean δ13C among months and between 2 years indicated that MPSWG did not suffer severely water stresses. In conclusion, MPSWG only used soil water during higher precipitation year, whereas they primarily utilized soil water and relied a little on groundwater during lower precipitation year. Water obtained by MPSWG (including water stored in trunk) basically satisfied its requirement for growth. Thus, MPSWG stand was relatively stable presently in the semi-arid sandy region. 相似文献18.
Cihan Ciftci Brian Kane Sergio F. Brena Sanjay R. Arwade 《Trees - Structure and Function》2014,28(2):517-529
Key message
We model varying decay in tree cross-sections by considering bending theory to estimate moment capacity loss (MCL) for the sections. We compare MCL with experiments on selected oak trees.Abstract
Tree failures can damage property and injure people, sometimes with fatal consequences. Arborists assess the likelihood of failure by examining many factors, including strength loss in the stem or branch due to decay. Current methods for assessing strength loss due to decay are limited by not accounting for offset areas of decay and assuming that the neutral axis of the cross-section corresponds to the centroidal axis. This paper considers that strength loss of a tree can be related to moment capacity loss (MCL) of the decayed tree cross-section, because tree failures are assumed to occur when induced moments exceed the moment capacity of the tree cross-section. An estimation of MCL is theoretically derived to account for offset areas of decay and for differences in properties of wood under compressive and tensile stresses. Field measurements are used to validate the theoretical approach, and predictions of loss in moment capacity are plotted for a range of scenarios of decayed stems or branches. Results show that the location and size of decay in the cross-section and relative to the direction of sway are important to determine MCL. The effect of wood properties on MCL was most evident for concentric decay and decreased as the location of decay moved to the periphery of the stem. The effect of the ratio of tensile to compressive moduli of elasticity on calculations of MCL was negligible. Practitioners are cautioned against using certain existing methods because the degree to which they over- or underestimate the likelihood of failure depended on the amount and location of decay in the cross-section. 相似文献19.
Key message
The present study unravels the anatomical characteristics and distribution patterns of cell wall polymers in the G-fibres found in the roots of A. nilotica using different microscopy techniques (light, electron and immunofluorescence microscopy).Abstract
The present study was aimed to investigate the anatomy of reaction xylem in the positively gravitropic roots of Acacia nilotica growing in compact and waterlogged soils. The roots collected from the two different sites showed occurrence of gelatinous fibres throughout xylem radii from a distance of 4 cm from the soil surface. The thickness of gelatinous layer (G-layer) increased in the root collected from the deeper soil. Further, the ultrastructural studies revealed a complete replacement of S2 and S3 layers in G-fibres nearer to root tip region as compared to the root portion close to upper part of the soil surface. In addition, these fibres demonstrated intense lignification in compound middle lamellae region of G-fibre walls. Moreover, the vessel density and their width increased considerably near the root tip region. The immunofluorescence analysis suggested that the β-1,4-galactans were prevalent in G-layer, whereas the xylan was restricted to only regions of lignified secondary wall. The similarities in distribution pattern and anatomical features of G-fibres in waterlogged and non-waterlogged roots suggest the occurrence of G-fibres as inherent characteristics in the roots of Acacia nilotica. 相似文献20.
Aline Cobut Robert Beauregard Pierre Blanchet 《The International Journal of Life Cycle Assessment》2013,18(3):722-742