scholarly journals Plasticity of the xylem vulnerability to embolism in Populus tremula x alba relies on pit quantity properties rather than on pit structure.

2021 ◽  
Author(s):  
Cédric Lemaire ◽  
Yann Quilichini ◽  
Nicole Brunel-Michac ◽  
Jérémie Santini ◽  
Liliane Berti ◽  
...  
Keyword(s):  
Structural Changes ◽  
Light Exposure ◽  
Phenotypic Variability ◽  
Hybrid Poplar ◽  
Populus Tremula ◽  
Severe Drought ◽  
Structural Determinants ◽  
Individual Tree ◽  
Xylem Vulnerability ◽  
Microscopy Techniques

Abstract Knowledge on variations of drought resistance traits are needed to predict the potential of trees to acclimate to coming severe drought events. Xylem vulnerability to embolism is a key parameter related to such droughts, and its phenotypic variability relies mainly on environmental plasticity. We investigated the structural determinants controlling the plasticity of vulnerability to embolism, focusing on the key elements involved in the air bubble entry in vessels, especially the inter-vessel pits. Poplar saplings (Populus tremula x alba) grown in contrasted water availability or light exposure exhibited differences in vulnerability to embolism (P50) in a range of 0.76 MPa. We then characterized the structural changes in features related to pit quantity and pit structure, from the pit ultrastructure to the organization of xylem vessels, using different microscopy techniques (TEM, SEM, LM). A multispectral combination of X-ray microtomography and light microscopy analysis allowed measuring the vulnerability of each single vessel and testing some of the relationships between structural traits and vulnerability to embolism inside the xylem. The pit ultrastructure did not change, whereas the vessel dimensions increased with vulnerability to embolism and the grouping index and fraction of inter-vessel cell wall both decreased with vulnerability to embolism. These findings hold when comparing between trees, or between the vessels inside the xylem of an individual tree. These results evidenced that plasticity of vulnerability to embolism in hybrid poplar occurs through changes in the pit quantity properties such as pit area and vessel grouping rather than on the pit structure.

scholarly journals Plasticity of the xylem vulnerability to embolism in poplar relies on quantitative pit properties rather than on pit structure

2020 ◽  
Author(s):  
Cédric Lemaire ◽  
Yann Quilichini ◽  
Nicole Brunel-Michac ◽  
Jérémie Santini ◽  
Liliane Berti ◽  
...  
Keyword(s):  
Structural Changes ◽  
Light Exposure ◽  
Phenotypic Variability ◽  
Severe Drought ◽  
Structural Determinants ◽  
Air Bubble ◽  
Qualitative And Quantitative ◽  
Xylem Vulnerability ◽  
Microscopy Techniques ◽  
Key Parameter

AbstractKnowledge on variations of drought resistance traits are needed to predict the potential of trees to acclimate to coming severe drought events. Xylem vulnerability to embolism is a key parameter related to such droughts, and its phenotypic variability relies mainly on environmental plasticity. We investigated the structural determinants controlling the plasticity of vulnerability to embolism, focusing on the key elements involved in the air bubble entry in a vessel, especially the inter-vessel pits. Poplar saplings (Populus tremula x alba) grown in contrasted water availability or light exposure exhibited differences in vulnerability to embolism in a range of 0.76 MPa. We then characterized the structural changes related to qualitative and quantitative pit characteristics, from the pit structure to the organization of xylem vessels, using different microscopy techniques (TEM, SEM, light). X-ray microtomography analysis allowed observing the vessel vulnerability and testing some of the relationships between structural traits and vulnerability to embolism inside the xylem. The pit ultrastructure did not change, whereas the vessel dimensions increased with vulnerability to embolism and the grouping index and fraction of inter-vessel cell wall decreased with vulnerability to embolism. These findings holds when comparing trees or when comparing vessels inside the xylem. These results evidenced that plasticity of vulnerability to embolism occurs through changes in the quantitative pit properties such as pit area and vessel grouping rather than on the pit structure.

scholarly journals Structural and Morphological Properties of Titanium Aluminum Nitride Coatings Produced by Triode Magnetron Sputtering

2014 ◽  
Vol 10 (20) ◽  
pp. 51-64 ◽  
Author(s):  
D.M. Devia ◽  
E. Restrepo-Parra ◽  
J.M. Velez-Restrepo
Keyword(s):  
Magnetron Sputtering ◽  
Bias Voltage ◽  
Structural Changes ◽  
Morphological Properties ◽  
X Ray Diffraction ◽  
Force Microscopy ◽  
Atomic Force ◽  
Titanium Aluminum ◽  
Microscopy Techniques ◽  
Titanium Aluminum Nitride

Tix Al1−xN coatings were grown using the triode magnetron sputtering technique varying the bias voltage between -40 V and -150V. The influence of bias voltage on structural and morphological properties was analyzed by means of energy dispersive spectroscopy, x-ray diffraction and atomic force microscopy techniques. As the bias voltage increased, an increase inthe Al atomic percentage was observed competing with Ti and producing structural changes. At low Al concentrations, the film presented a FCC crystalline structure; nevertheless, as Al was increased, the structure pre-sented a mix of FCC and HCP phases. On the other hand, an increase inbias voltage produced a decrease films thickness due to an increase in colli-sions. Moreover, the grain size and roughness were also strongly influencedby bias voltage.

Using tree rings to assess the potential of thinning to alleviate drought stress in a dry forest of western Canada

2021 ◽  
Author(s):  
David Montwé ◽  
Audrey Standish ◽  
Miriam Isaac-Renton ◽  
Jodi Axelson
Keyword(s):  
Tree Ring ◽  
Tree Rings ◽  
Basal Area ◽  
Dry Forest ◽  
Tree Level ◽  
Severe Drought ◽  
Western Canada ◽  
Drought Event ◽  
Individual Tree ◽  
Potential Benefits

<p>Increasing frequency of severe drought events under climate change is a major cause for concern for millions of hectares of forested land. One practical solution to improving forest resilience may be thinning. There may be several potential benefits, chief of which is that drought tolerance could be improved in the remaining trees due to lower competition for resources and increased precipitation throughfall. By improving resilience to drought, this may increase productivity of the remaining trees while lowering risks of mortality. Such potential benefits can effectively be quantified with data from statistically-sound, long-term field experiments, and tree rings provide a suitable avenue to compare treatments. We work with an experiment that applied different levels of tree retention to mature interior Douglas fir (<em>Pseudotsuga menziesii</em> var. <em>glauca</em>) in a dry ecosystem of western Canada. The treatments were applied in the winter of 2002/2003, coinciding with the aftermath of a severe natural drought event in 2002. We used tree-rings to quantify the extent to which thinning improves recovery and resilience of treated trees as compared to non-thinned controls. Tree-ring samples as well as height and diameter data were obtained from 83 trees from 8 treatment units of the randomized experimental design. Indicators for resilience to drought were calculated based on basal area increments. Thinning substantially increased basal area increments at the individual tree level, but more importantly, led to significantly higher recovery and resilience relative to the control. The results of this tree-ring analysis suggest that thinning may be a viable silvicultural intervention to counteract effects of severe drought events and to maintain tree cover.</p>

scholarly journals Immunocytochemical Labeling of Rhabdomeric Proteins inDrosophilaPhotoreceptor Cells Is Compromised by a Light-dependent Technical Artifact

2019 ◽  
Vol 67 (10) ◽  
pp. 745-757 ◽  
Author(s):  
Krystina Schopf ◽  
Thomas K. Smylla ◽  
Armin Huber
Keyword(s):  
Structural Changes ◽  
Protein Transport ◽  
Light Exposure ◽  
Protein Localization ◽  
Photoreceptor Cells ◽  
Antibody Staining ◽  
Technical Artifact ◽  
Stage Process ◽  
Stage 1 ◽  
Antibody Labeling

Drosophila photoreceptor cells are employed as a model system for studying membrane protein transport. Phototransduction proteins like rhodopsin and the light-activated TRPL ion channel are transported within the photoreceptor cell, and they change their subcellular distribution in a light-dependent way. Investigating the transport mechanisms for rhodopsin and ion channels requires accurate histochemical methods for protein localization. By using immunocytochemistry the light-triggered translocation of TRPL has been described as a two-stage process. In stage 1, TRPL accumulates at the rhabdomere base and the adjacent stalk membrane a few minutes after onset of illumination and is internalized in stage 2 by endocytosis after prolonged light exposure. Here, we show that a commonly observed crescent shaped antibody labeling pattern suggesting a fast translocation of rhodopsin, TRP, and TRPL to the rhabdomere base is a light-dependent antibody staining artifact. This artifact is most probably caused by the profound structural changes in the microvillar membranes of rhabdomeres that result from activation of the signaling cascade. By using alternative labeling methods, either eGFP-tags or the self-labeling SNAP-tag, we show that light activation of TRPL transport indeed results in fast changes of the TRPL distribution in the rhabdomere but not in the way described previously.

scholarly journals Size-dependent diffusion controls natural aging in aluminium alloys

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Phillip Dumitraschkewitz ◽  
Peter J. Uggowitzer ◽  
Stephan S. A. Gerstl ◽  
Jörg F. Löffler ◽  
Stefan Pogatscher
Keyword(s):  
Structural Changes ◽  
Materials Science ◽  
Natural Aging ◽  
Atom Probe ◽  
Rapid Quenching ◽  
Image Resolution ◽  
Atomic Lattice ◽  
Atomic Image ◽  
Microscopy Techniques ◽  
Non Equilibrium

Abstract A key question in materials science is how fast properties evolve, which relates to the kinetics of phase transformations. In metals, kinetics is primarily connected to diffusion, which for substitutional elements is enabled via mobile atomic-lattice vacancies. In fact, non-equilibrium vacancies are often required for structural changes. Rapid quenching of various important alloys, such as Al- or Mg-alloys, results for example in natural aging, i.e. slight movements of solute atoms in the material, which significantly alter the material properties. In this study we demonstrate a size effect of natural aging in an AlMgSi alloy via atom probe tomography with near-atomic image resolution. We show that non-equilibrium vacancy diffusional processes are generally stopped when the sample size reaches the nanometer scale. This precludes clustering and natural aging in samples below a certain size and has implications towards the study of non-equilibrium diffusion and microstructural changes via microscopy techniques.

Influence of overexpression of a gibberellin 20-oxidase gene on the kinetics of xylem cell development in hybrid poplar (Populus tremula L. and P. tremuloides Michx.)

Holzforschung ◽  
2006 ◽  
Vol 60 (6) ◽  
pp. 608-617 ◽  
Author(s):  
Oliver Dünisch ◽  
Matthias Fladung ◽  
Satoshi Nakaba ◽  
Yoko Watanabe ◽  
Ryo Funada
Keyword(s):  
Transgenic Plants ◽  
Cell Expansion ◽  
Hybrid Poplar ◽  
Cell Development ◽  
Populus Tremula ◽  
Uv Spectrophotometry ◽  
Wild Type ◽  
Oxidase Gene ◽  
Xylem Cell ◽  
Kinetics Of

Abstract Gibberellins (GAs) are important regulators of shoot growth in trees. We studied the kinetics of xylem formation in hybrid poplar (Populus tremula L.×P. tremuloides Michx.) in which the key regulatory gene gibberellin acid 20 oxidase (GA20-oxidase) isolated from Arabidopsis is overexpressed. Increments in the height and radius of shoots were registered by high-resolution laser measurements. The anatomical and chemical structure of mature xylem cells was studied by light electron microscopy and UV spectrophotometry. Transgenic plants showed an increase in height growth, but a lower speed of cell elongation during primary growth compared to wild-type plants. During the first year of growth, transgenic plants showed a higher radius increment, an increase in the period of cell expansion of vessels and fibres and their final size, and a higher lignin content of the compound middle lamella between fibres compared to wild-type plants. In contrast, during the third year of growth, only a slight increase in the period of cell expansion of fibre cells was observed in transgenic compared to wild-type plants. Analyses of GA20-oxidase expression in leaves and shoots of 6-month- and 3-year-old plants of three different independent transgenic lines revealed a decrease in its expression only in shoots but not in leaves of the 3-year-old plants. The results indicate that overexpression of the GA20-oxidase gene in young shoots of transgenic poplar predominately affects cell expansion, while no GA20-oxidase expression was observed in shoots of 3-year-old transgenic plants, resulting in wild-type xylem cell development.

Structural determinants of glomerular hydraulic permeability

1994 ◽  
Vol 266 (1) ◽  
pp. F1-F12 ◽  
Author(s):  
M. C. Drumond ◽  
W. M. Deen
Keyword(s):  
Basement Membrane ◽  
Hydraulic Resistance ◽  
Structural Changes ◽  
Water Movement ◽  
Capillary Wall ◽  
Hydraulic Permeability ◽  
Structural Determinants ◽  
Membrane Area

To elucidate which structures determine the resistance to water movement, we used a computational fluid dynamics approach to determine velocity and pressure fields within the glomerular capillary wall. The model included representations of the endothelial fenestrae, basement membrane, and epithelial filtration slits with slit diaphragms. The input data included dimensions of the various structures from previous electron microscopy studies, as well as the hydraulic permeability recently measured for isolated films of glomerular basement membrane in vitro. The hydraulic resistance of the endothelium was predicted to be small, whereas the basement membrane and filtration slits were each found to contribute roughly one-half of the total hydraulic resistance of the capillary wall. It was calculated that, for a given filtrate flux, the pressure drop within basement membrane in vivo is roughly twice that of “bare” or isolated basement membrane, because of the small fraction of basement membrane area exposed. The dominant resistance in the filtration slit was found to be the slit diaphragm. Predicted values for the overall hydraulic permeability of the capillary wall were within the experimental range derived from micropuncture measurements in normal rats. The model should be a useful tool for analyzing the effects of various structural changes on glomerular hydraulic permeability. This is illustrated by applying the model to recent physiological and morphometric data in nephrotic rats.

Molecular Structural Changes of Plasticized PVC after UV Light Exposure

2013 ◽  
Vol 117 (50) ◽  
pp. 16336-16344 ◽  
Author(s):  
Jeanne M. Hankett ◽  
William R. Collin ◽  
Zhan Chen
Keyword(s):  
Structural Changes ◽  
Uv Light ◽  
Light Exposure ◽  
Plasticized Pvc

scholarly journals Delayed effect of drought on the xylem vulnerability to cavitation in Fagus sylvatica L.

2020 ◽  
Author(s):  
Stephane Herbette ◽  
Olivia Charrier ◽  
Herve Cochard ◽  
Tete Severien Barigah
Keyword(s):  
Drought Resistance ◽  
Environmental Conditions ◽  
European Beech ◽  
Severe Drought ◽  
Delayed Effect ◽  
Large Variability ◽  
Xylem Structure ◽  
Vulnerability To Cavitation ◽  
Xylem Vulnerability ◽  
Fagus Sylvatica L

Knowledge on variations of drought resistance traits is needed to predict the potential of trees to adapt to severe drought events expected to be more intense and frequent. Xylem vulnerability to cavitation is among the most important traits related to drought-induced mortality and exhibits a large variability between species. Acclimation of this trait to environmental conditions implies changes in the xylem structure and organization, leading previous studies to investigate its variations under conditions preserving growth. In European beech saplings, we assessed the effect of droughts of on the vulnerability to cavitation in branches that develop during recovery. The newly formed branches displayed lower vulnerability to cavitation in the plants that underwent the severest droughts leading to native embolism; the pressure that induces 50% loss of conductance being of -3.98 MPa in severely droughted plants whereas it was of -3.1 MPa in control plants, respectively. Although unexpected, these results argue for an acclimation, and not a weakening, of this trait to drought events.

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