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Steven Jansen - One of the best experts on this subject based on the ideXlab platform.
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The Effect of Preparation Techniques on Sem-Imaging of Pit Membranes
Iawa Journal, 2020Co-Authors: Steven Jansen, Annelies Pletsers, Yuzou SanoAbstract:This paper examines the effects of 30 preparation techniques on SEMimages of Pit Membranes in vessels and tracheids from the two latest growth rings in twigs of Pinus wallichiana, Fraxinus americana and Laurus nobilis. Most variation observed is due to coating and treatment with chemical solutions, such as acetone, ethanol and hydrogen peroxide. The effects of chemicals appear to be associated with the thickness of the Pit Membrane, resulting in an increased density and diameter of pores in Pit Membranes of F. americana and L. nobilis and an almost complete dissolution of the porous margo in P. wallichiana. Although different protocols offer advantages for different species, the following methods are recommended: (1) the use of fresh material, (2) air-drying without any chemical treatment, (3) splitting of dried samples, (4) vacuum evaporation with platinum, and (5) SEM-imaging at an accelerating voltage below 5 kV.
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Pit Membranes in tracheary elements of Rosaceae and related families: New records of tori and pseudotori
Various articles, 2020Co-Authors: Steven Jansen, Brendan Choat, David Rabaey, Frederic Lens, Yuzou Sano, Roland R DuteAbstract:The micromorphology of Pits in tracheary elements was examined in 35 species representing 29 genera of Rosaceae and related families to evaluate the assumption that angiosperm Pits are largely invariant. In most Rosaceae, Pit Membranes between fibers and tracheids frequently appear to have amorphous thickenings with an irregular distribution. Although these structures are toruslike under the light microscope, observations by electron microscopy illustrate that they represent ‘‘pseudotori’’ or plasmodesmata-associated thickenings. These thickenings frequently extend from the periphery of the Pit Membrane and form a cap-like, hollow structure. Pseudotori are occasionally found in few Elaeagnaceae and Rhamnaceae and appear to be related to species with fiber-tracheids and/or tracheids. True tori are strongly associated with round to oval Pit apertures and are consistently present in narrow tracheary elements of Cercocarpus (Rosaceae), Planera (Ulmaceae), and ring-porous species of Ulmus and Zelkova (Ulmaceae). Vestured Pits with homogenous Pit Membranes are reported for Hemiptelea (Ulmaceae). The homoplasticnature of Pit Membrane characteristics may be related to functional adaptations in terms of safety and efficiency of water transportor may reflect different developmental processes of xylem elements. These observations illustrate that there is more variation in angiosperm Pits than previously thought.
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Within-tree variability and sample storage effects of bordered Pit Membranes in xylem of Acer pseudoplatanus
Trees, 2019Co-Authors: Martyna M Kotowska, Rebecca Thom, H.j. Schenk, Ya Zhang, Steven JansenAbstract:Key messageIntervessel Pit Membranes in xylem tissue of Acer pseudoplatanus differ in their thickness both within and across plant organs and may undergo considerable shrinkage during dehydration and sample preparation.AbstractIntervessel Pit Membranes have been suggested to account for more than half of the total xylem hydraulic resistance in plants and play a major role in vulnerability to drought-induced hydraulic failure. While the thickness of intervessel Pit Membranes was found to be associated with xylem embolism resistance at an interspecific level, variation in Pit Membrane structure across different organs along the flow path within a single tree remains largely unknown. Based on transmission electron microscopy, we examined intra-tree variation of bordered Pit and Pit Membrane characteristics in xylem of roots, stems, branches, petioles, and leaf veins of Acer pseudoplatanus . Moreover, potential preparation artefacts on Pit Membrane structure such as alcohol treatment and dehydration were tested. Our observations showed quantitative differences in bordered Pits across organs, including variation in Pit Membrane thickness within and across organs. Vessel size was weakly related to intervessel wall thickness, but not significantly linked to Pit Membrane thickness. Gradual dehydration of wood samples resulted in irreversible shrinkage of Pit Membranes, together with increased levels of aspiration. These findings are relevant to explore similarity in xylem embolism resistance across plant organs.
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Infrared Nanospectroscopy Reveals the Chemical Nature of Pit Membranes in Water-Conducting Cells of the Plant Xylem.
Plant Physiology, 2018Co-Authors: Luciano José Pereira, Steven Jansen, Denisele N. A. Flores-borges, Paulo R. L. Bittencourt, Juliana Lischka Sampaio Mayer, Eduardo Kiyota, Pedro Araújo, Raul O. Freitas, Rafael S. Oliveira, Paulo MazzaferaAbstract:In the xylem of angiosperm plants, microscopic Pits through the secondary cell walls connect the water-conducting vessels. Cellulosic meshes originated from primary walls and middle lamella between adjacent vessels, called Pit Membrane, separates one conduit from another. The intricate structure of the nano-sized pores in Pit Membranes enables the passage of water under negative pressure without hydraulic failure due to obstruction by gas bubbles (i.e., embolism) under normal conditions or mild drought stress. Since the chemical composition of Pit Membranes affects embolism formation and bubble behavior, we directly measured Pit Membrane composition in Populus nigra wood. Here, we characterized the chemical composition of cell wall structures by synchrotron infrared nanospectroscopy and atomic force microscopy-infrared nanospectroscopy with high spatial resolution. Characteristic peaks of cellulose, phenolic compounds, and proteins were found in the intervessel Pit Membrane of P. nigra wood. In addition, vessel to parenchyma Pit Membranes and developing cell walls of the vascular cambium showed clear signals of cellulose, proteins, and pectin. We did not find a distinct peak of lignin and other compounds in these structures. Our investigation of the complex chemical composition of intervessel Pit Membranes furthers our understanding of the flow of water and bubbles between neighboring conduits. The advances presented here pave the way for further label-free studies related to the nano-chemistry of plant cell components.
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Bordered Pits in xylem of vesselless angiosperms and their possible misinterpretation as perforation plates
Plant Cell and Environment, 2017Co-Authors: Ya Zhang, Matthias Klepsch, Steven JansenAbstract:Vesselless wood represents a rare phenomenon within the angiosperms, characterizing Amborellaceae, Trochodendraceae, and Winteraceae. Anatomical observations of bordered Pits and their Pit Membranes based on light, scanning and transmission electron microscopy (SEM, TEM) are required to understand functional questions surrounding vesselless angiosperms and the potential occurrence of cryptic vessels. Interconduit Pit Membranes in 11 vesselless species showed a similar ultrastructure as mesophytic vessel-bearing angiosperms, with a mean thickness of 245 nm (± 53, SD; n = 6 species). Shrunken, damaged, and aspirated Pit Membranes, which were 52% thinner than Pit Membranes in fresh samples (n = 4 species), occurred in all dried-and-rehydrated samples, and in fresh latewood of Tetracentron sinense and Trochodendron aralioides. SEM demonstrated that shrunken Pit Membranes showed artificially enlarged, > 100 nm wide pores. Moreover, perfusion experiments with stem segments of Drimys winteri showed that 20 and 50 nm colloidal gold particles only passed through 2 cm long dried-and-rehydrated segments, but not through similar sized fresh ones. These results indicate that Pit Membrane shrinkage is irreversible and associated with a considerable increase in pore size. Moreover, our findings suggest that Pit Membrane damage, which may occur in planta, could explain earlier records of vessels in vesselless angiosperms.
Roland R Dute - One of the best experts on this subject based on the ideXlab platform.
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Pit Membranes in tracheary elements of Rosaceae and related families: New records of tori and pseudotori
Various articles, 2020Co-Authors: Steven Jansen, Brendan Choat, David Rabaey, Frederic Lens, Yuzou Sano, Roland R DuteAbstract:The micromorphology of Pits in tracheary elements was examined in 35 species representing 29 genera of Rosaceae and related families to evaluate the assumption that angiosperm Pits are largely invariant. In most Rosaceae, Pit Membranes between fibers and tracheids frequently appear to have amorphous thickenings with an irregular distribution. Although these structures are toruslike under the light microscope, observations by electron microscopy illustrate that they represent ‘‘pseudotori’’ or plasmodesmata-associated thickenings. These thickenings frequently extend from the periphery of the Pit Membrane and form a cap-like, hollow structure. Pseudotori are occasionally found in few Elaeagnaceae and Rhamnaceae and appear to be related to species with fiber-tracheids and/or tracheids. True tori are strongly associated with round to oval Pit apertures and are consistently present in narrow tracheary elements of Cercocarpus (Rosaceae), Planera (Ulmaceae), and ring-porous species of Ulmus and Zelkova (Ulmaceae). Vestured Pits with homogenous Pit Membranes are reported for Hemiptelea (Ulmaceae). The homoplasticnature of Pit Membrane characteristics may be related to functional adaptations in terms of safety and efficiency of water transportor may reflect different developmental processes of xylem elements. These observations illustrate that there is more variation in angiosperm Pits than previously thought.
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Comparative Development of Intertracheary Pit Membranes in Abies Firma and Metasequoia Glyptostroboides
Iawa Journal, 2020Co-Authors: Roland R Dute, Latoya Hagler, Adam BlackAbstract:This study compares intertracheary Pit Membrane structure and ontogeny in Abies firma (Pinaceae) and Metasequoia glyptostroboides (Cupressaceae). Initial phases of Pit Membrane development are the same for both species. Branched plasmodesmata are present in the earliest stages of Pit Membrane development observed. Torus thickening of the Pit Membrane occurs early in Pit development prior to Pit border initiation. During Pit border enlargement, plastids frequently occlude the apertures. Cell lysis is associated with complete wall matrix removal from Pit Membranes of Metasequoia. By contrast, cell lysis in Abies results in loss of matrix material from the margo, whereas the torus remains largely unaffected. Torus extensions in Pit Membranes of A. firma retain variable amounts of matrix material. Either a difference in chemical composition of the torus or a difference in autolytic enzymes is hypothesized to explain developmental differences between Pit Membranes of the two species.
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Development, Structure, and Function of Torus–Margo Pits in Conifers, Ginkgo and Dicots
Functional and Ecological Xylem Anatomy, 2020Co-Authors: Roland R DuteAbstract:Tracheary elements, the water-conducting cells of the xylem, are connected by bordered Pit pairs containing Pit Membranes. The function of the latter is to allow passage of water but not air embolisms. One type of Pit Membrane form that has evolved repeatedly consists of a central, impermeable torus surrounded by a permeable margo. This Membrane structure is common in gymnosperms, but less so in angiosperms. In this chapter, various ontogenetic sequences for the formation of torus/margo Pit Membranes are explored. Also, the presence and function of such Pit Membranes under xeric conditions are discussed.
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Pit MembraneS OF EPHEDRA RESEMBLE GYMNOSPERMS MORE THAN ANGIOSPERMS
Iawa Journal, 2014Co-Authors: Roland R Dute, Lauren A. Bowen, Sarah Schier, Alexa G. Vevon, Troy L. Best, Maria L. Auad, Thomas Elder, Pauline S. Bouche, Steven JansenAbstract:Bordered Pit pairs of Ephedra species were characterized using different types of microscopy. Pit Membranes contained tori that did not stain for lignin. SEM and AFM views of the torus surface showed no plasmodesmatal openings, but branched, secondary plasmodesmata were occasionally noted using TEM in conjunction with ultrathin sections. The margo consisted of radial microfibrils as well as finer diameter tangential fibrils. The former formed fascicles of fibrils that merged into even thicker buttresses during the act of Pit Membrane aspiration. AFM showed a discontinuous layer of non-microfibrillar material on the surface of both torus and margo. It is hypothesized that this material is responsible for adhesion of the Pit Membrane to the surface of the Pit border during the process of aspiration. Taken as a whole, intervascular Pit Membranes of Ephedra more closely resemble those of conifers than those of torus-bearing Pit Membranes of angiosperms.
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crystals associated with the intertracheid Pit Membrane of the woody fern botrychium multifidum
American Fern Journal, 2002Co-Authors: Angela C Morrow, Roland R DuteAbstract:Abstract Calcium-containing crystals have been found in the lumens of secondary tracheids in the rhizome of the woody fern Botrychium multifidum. These crystals are styloids with rough, pyramid-shaped ends. The crystals are usually single; however, conjoined or grouped crystals were also found. Crystal formation apparently has no constant relation to the Pit Membrane, but crystals of mature tracheids are often associated with the Pit Membrane or are located in the Pit areas. Crystals were also located between the helical thickenings of the lumen walls. No crystal chamber or crystal sheath was found in association with the crystal body.
Edward L Schneider - One of the best experts on this subject based on the ideXlab platform.
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Distinctive tracheid microstructure in stems of Victoria and Euryale (Nymphaeaceae).
Botanical Journal of the Linnean Society, 2020Co-Authors: Sherwin Carlquist, Edward L SchneiderAbstract:Scanning electron microscopy (SEM) photographs of thick sections from liquid-preserved stems of Victoria cruziana and Euryale ferox show accretions of coarse fibrils on Pit Membranes of tracheids. The first-deposited fibrils are randomly orientated; on top of them (facing the tracheid lumina) are axially orientated coarse fibrils. The two systems are interconnected. Axially orientated fibrils were more extensively observed in Euryale than in Victoria and tips of fibrils in Euryale extend over the Pit apertures onto secondary wall surfaces. Tracheid–parenchyma interfaces bear rudimentary coarse fibrils on the tracheid side. End walls of Victoria tracheids have highly porose Pit Membranes, thinner and less complex than those of the lateral intertracheid walls. The structures reported in Victoria and Euryale are consistent with those concurrently reported for stems of other Nymphaeaceae. Although also present in Cabombaceae, the coarse fibrils are otherwise not reported for stems of angiosperms and are not yet reported in roots of any species. Pit Membrane remnants in perforation plates of various woody dicotyledons represent a nonhomologous phenomenon. The accretions of coarse fibrils in stem tracheids of Nymphaeaceae do not appear to enhance conduction, although they do contain porosities interconnecting tracheids. Removal of Pit Membrane remnants from perforation plates of primitive dicotyledon woods by hydrolysis does, on the contrary, suggest conduction enhancement. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159, 52–57.
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origins and nature of vessels in monocotyledons 12 Pit Membrane microstructure diversity in tracheary elements of astelia
Pacific Science, 2010Co-Authors: Sherwin Carlquist, Edward L SchneiderAbstract:Abstract: Xylem of stems and roots of three species of Astelia, a monocot with relatively unspecialized xylem, was examined with scanning electron microscopy (SEM) to better understand structural conditions intermediate between tracheids and vessel elements. Both macerations and hand-sectioned material were studied. Tracheary elements of roots of Asteliaceae can be characterized as tracheids, with some degrees of transition to vessel elements. Pit Membrane remnants, which take the form of pores, reticula, or threads, are present commonly in end walls of tracheary elements of roots of Astelia. Stems of Astelia have tracheids with less-conspicuous porosities in the Pit Membranes of end walls than those of roots. Sectioned materials show that the porose (reticulate) cellulosic layers of the primary wall, which is embedded in a matrix of amorphous material, can be exposed to various degrees by the sectioning process; the cellulosic network faces the lumen, and the amorphous material is the compound middle lam...
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xylem of early angiosperms nuphar nymphaeaceae has novel tracheid microstructure1
American Journal of Botany, 2009Co-Authors: Sherwin Carlquist, Edward L Schneider, Barre C HellquistAbstract:: SEM studies of xylem of stems of Nuphar reveal a novel feature, not previously reported for any angiosperm. Pit Membranes of tracheid end walls are composed of coarse fibrils, densest on the distal (outside surface, facing the Pit of an adjacent cell) surface of the Pit Membrane of a tracheid, thinner, and disposed at various levels on the lumen side of a Pit Membrane. The fibrils tend to be randomly oriented on the distal face of the Pit Membrane; the innermost fibrils facing the lumen take the form of longitudinally oriented strands. Where most abundantly present, the fibrils tend to be disposed in a spongiform, three-dimensional pattern. Pores that interconnect tracheids are present within the fibrillar meshwork. Pit Membranes on lateral walls of stem tracheids bear variously diminished versions of this pattern. Pits of root tracheids are unlike those of stems in that the lumen side of Pit Membranes bears a reticulum revealed on the outer surface of the tracheid after most of the thickness of a Pit Membrane is shaved away by the sectioning process. No fibrillar texturing is visible on the root tracheid Pits when they are viewed from the inside of a tracheid. Tracheid end walls of roots do contain pores of various sizes in Pit Membranes. These root and stem patterns were seen in six species representing the two sections of Nuphar, plus one intersectional hybrid, as well as in one collection of Nymphaea, included for purposes of comparison. Differences between root and stem tracheids with respect to microstructure are consistent in all species studied. Microstructural patterns reported here for stem tracheid Pits of Nymphaeaceae are not like those of Chloranthaceae, Illiciaceae, or other basal angiosperms. They are not referable to any of the patterns reported for early vascular plants. The adaptational nature of the Pit Membrane structure in these tracheids is not apparent; microstructure of Pit Membranes in basal angiosperms is more diverse than thought prior to study with SEM.
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Pit Membrane remnants in perforation plates of hydrangeales with comments on Pit Membrane remnant occurrence physiological significance and phylogenetic distribution in dicotyledons
Botanical Journal of the Linnean Society, 2004Co-Authors: Sherwin Carlquist, Edward L SchneiderAbstract:Perforation plates from ten species of seven genera of Hydrangeales sensu Thorne were studied using scanning elec tron microscopy (SEM). The presence of Pit Membranes in perforations ranges from abundant, as in Carpenteria and Ilydrangea, to minimal, as in Deutzia, Escallonia and Fhiladelphus. Abnormally great Pit Membrane presence may result from the presence of secondary compounds that inhibit lysis, as in Quintinia serrata; such interference with the natural lysis process may or may not be evident from coarseness and irregularity of Pit Membrane surface and of threads composing the Pit Membrane remnants. The presence of Pit Membrane remnants in perforation plates is hypothesized to be a symplesiomorphy, found in a fraction of dicotyledons with scalarifonn perforation plates (but still in an appreciable number of species). Pit Membrane remnant presence may represent incomplete lysis of pri mary wall material (cellulose microfibrils) in species that occupy highly mesic habitats, where such impedance in the conductive stream does not have an appreciable negative s&ective value. This physiological interpretation of Pit Membrane remnants in perforations is enhanced by the phylogenetic distribution as well as the strongly mesic eco logical preferences of species that exempli’ this phenomenon in dicotyledons at large. Families with Pit Membrane presence in perforations are scattered throughout phylogenetic trees, but they occur most often in basal branches of major clades (superorders) or as basal branches of orders within the major clades. Further study will doubtless reveal other families and genera in which this phenomenon occurs, although it is readily detected only with SEM. Phylo genetic stages in the disappearance of Pit Membrane remnants from perforation plates are described, ranging from intact Pit Membranes except for presence of pores of various sizes, to presence of Membrane remnants only at lateral ends of perforations and in one or two perforations (arguably Pits) at the transition between a perforation plate and subadj scent lateral wall Pitting. Developmental study of the mechanism and timing of lysis of Pit Membranes in per forations, and assessment of the role of the conductive stream in their removal, are needed to enhance present under standing of vessel evolution. © 2004 The Linnean Society of London, Botanical Jottrnal of the Linnean Society, 2004, 146, 41—51. ADDITIONAL KEYWORDS: Cornales — ecological wood anatomy — Escalloniaceae — Ixerbaceae — Saxifragaceae — vessel evolution — wood evolution.
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Pit Membrane remnants in perforation plates and other vessel details of cornales
Brittonia, 2004Co-Authors: Edward L Schneider, Sherwin CarlquistAbstract:Perforation plates and other vessel details as studied with scanning electron microscopy (SEM) have been reported for four species of Cornaceae (s.l.): similar features are shown by the four, suggesting that a more extensive sampling of the family might reveal similar phenomena. Perforation plates contain Pit Membrane remnants in the form of threads or, less commonly, laminar portions perforated by pores. When least well-represented, the Pit Membrane remnants are restricted to lateral ends of perforations and to the perforations transitional to lateral wall Pitting. Perforations are all clearly bordered. Helical thickenings that do not form a continuous gyre are reported for the vessel walls ofAucuba. The presence of Pit Membrane remnants in vessel elements of Cornaceae correlates with the mesic habitats occupied by species in this family. The presence and type of Pit Membrane remnants reported by us in the three genera is very similar, although Pit Membrane remnants are doubtless a symplesiomorphy and thus not an indicator of relationships. The presence of Pit Membrane remnants in the three genera, however, does attest to the primitiveness of wood and other features of Cornaceae s.l.
Brendan Choat - One of the best experts on this subject based on the ideXlab platform.
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Pit Membranes in tracheary elements of Rosaceae and related families: New records of tori and pseudotori
Various articles, 2020Co-Authors: Steven Jansen, Brendan Choat, David Rabaey, Frederic Lens, Yuzou Sano, Roland R DuteAbstract:The micromorphology of Pits in tracheary elements was examined in 35 species representing 29 genera of Rosaceae and related families to evaluate the assumption that angiosperm Pits are largely invariant. In most Rosaceae, Pit Membranes between fibers and tracheids frequently appear to have amorphous thickenings with an irregular distribution. Although these structures are toruslike under the light microscope, observations by electron microscopy illustrate that they represent ‘‘pseudotori’’ or plasmodesmata-associated thickenings. These thickenings frequently extend from the periphery of the Pit Membrane and form a cap-like, hollow structure. Pseudotori are occasionally found in few Elaeagnaceae and Rhamnaceae and appear to be related to species with fiber-tracheids and/or tracheids. True tori are strongly associated with round to oval Pit apertures and are consistently present in narrow tracheary elements of Cercocarpus (Rosaceae), Planera (Ulmaceae), and ring-porous species of Ulmus and Zelkova (Ulmaceae). Vestured Pits with homogenous Pit Membranes are reported for Hemiptelea (Ulmaceae). The homoplasticnature of Pit Membrane characteristics may be related to functional adaptations in terms of safety and efficiency of water transportor may reflect different developmental processes of xylem elements. These observations illustrate that there is more variation in angiosperm Pits than previously thought.
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the relationships between xylem safety and hydraulic efficiency in the cupressaceae the evolution of Pit Membrane form and function
Plant Physiology, 2010Co-Authors: Jarmila Pittermann, Steven Jansen, Brendan Choat, Stephanie A Stuart, Lucy Lynn, Todd E DawsonAbstract:Water transport in conifers occurs through single-celled tracheids that are connected to one another via intertracheid Pit Membranes. These Membranes have two components: the porous margo, which allows water to pass through the Membrane, and the impermeable torus, which functions to isolate gas-filled tracheids. During drought, tracheids can become air filled and thus hydraulically dysfunctional, a result of air entering through the Pit Membrane and nucleating cavitation in the water column. What are the hydraulic tradeoffs associated with cavitation resistance at the Pit level, and how do they vary within the structural components of the intertracheid Pit? To address these questions, we examined Pit structure in 15 species of Cupressaceae exhibiting a broad range of cavitation resistances. Across species, cavitation resistance was most closely correlated to the ratio of the torus to Pit aperture diameter but did not vary systematically with margo porosity. Furthermore, our data indicate that constraints on Pit hydraulic efficiency are shared: the Pit aperture limits Pit conductivity in more drought-resistant taxa, while increased margo resistance is more likely to control Pit conductivity in species that are more vulnerable to cavitation. These results are coupled with additional data concerning Pit Membrane structure and function and are discussed in the context of the evolutionary biogeography of the Cupressaceae.
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Morphological variation of intervessel Pit Membranes and implications to xylem function in angiosperms
American Journal of Botany, 2009Co-Authors: Steven Jansen, Brendan Choat, Annelies PletsersAbstract:: Pit Membranes between xylem vessels have been suggested to have functional adaptive traits because of their influence on hydraulic resistance and vulnerability to embolism in plants. Observations of intervessel Pit Membranes in 26 hardwood species using electron microscopy showed significant variation in their structure, with a more than 25-fold difference in thickness (70-1892 nm) and observed maximum pore diameter (10-225 nm). In some SEM images, Pit Membrane porosity was affected by sample preparation, although pores were resolvable in intact Pit Membranes of many species. A significant relationship (r(2) = 0.7, P = 0.002) was found between Pit Membrane thickness and maximum pore diameter, indicating that the thinner Membranes are usually more porous. In a subset of nine species, maximum pore diameter determined from SEM was correlated with pore diameter calculated from air-seeding thresholds (r(2) = 0.8, P < 0.001). Our data suggest that SEM images of intact Pit Membranes underestimate the porosity of Pit Membranes in situ. Pit Membrane porosity based on SEM offers a relative estimate of air-seeding thresholds, but absolute pore diameters must be treated with caution. The implications of variation in Pit Membrane thickness and porosity to plant function are discussed.
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direct measurements of intervessel Pit Membrane hydraulic resistance in two angiosperm tree species
American Journal of Botany, 2006Co-Authors: Brendan Choat, Tyler W Brodie, Alexander R Cobb, Maciej A Zwieniecki, Michelle N HolbrookAbstract:The hydraulic resistance of Pit Membranes was measured directly in earlywood vessels of Fraxinus americana and Ulmus americana. The area-specific resistance of Pit Membranes (rmem) was higher than modeled or measured values obtained previously for hardwood species, with rmem of 5.24 3 10 3 MPasm � 1 for Fraxinus and 2.56 3 10 3 MPasm � 1 for Ulmus. The calculated resistance of Pit canals was three orders of magnitude below total Pit resistance indicating that Pit Membranes contributed the majority of resistance. Scanning electron microscopy indicated that Pit Membranes of Ulmus were thinner and more porous than those of Fraxinus, consistent with the difference in rmem between the species. Measurements of average vessel diameter and length and area of wall overlap with neighboring vessels were used to partition the vascular resistance between vessel lumen and Pit Membrane components. Pit Membrane resistance accounted for 80% of the total resistance in Fraxinus and 87% in Ulmus in 2-yr-old branch sections. However, measurements of vessel dimensions in the trunk suggest that the division of resistance between Pit Membrane and lumen components would be closer to co-limiting in older regions of the tree. Thus, Pit Membrane resistance may be of greater relative importance in small branches than in older regions of mature trees.
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changes in Pit Membrane porosity due to deflection and stretching the role of vestured Pits
Journal of Experimental Botany, 2004Co-Authors: Brendan Choat, Steven Jansen, Maciej A Zwieniecki, Erik Smets, Michele N HolbrookAbstract:The effect of increasing pressure difference (deltaP) on intervessel Pit Membrane porosity was studied in two angiosperm tree species with differing Pit architecture. Fraxinus americana L. possesses typical angiosperm bordered Pit structure while Sophora japonica L. exhibits well-developed vestures in intervessel Pit chambers. It was hypothesized (a) that large deltaP across intervessel Pits would cause the deflection of Pit Membranes in the stems of F. americana resulting in significant increases in porosity and thus lower cavitation thresholds, and (b) that the presence of vestures would prevent the deflection of Pit Membranes in S. japonica. To determine if the porosity of Pit Membranes increased under mechanical stress, suspensions of colloidal gold, 5 nm and 20 nm in diameter, were perfused across intervessel Pit Membranes at deltaP ranging from 0.25 MPa to 6.0 MPa. The effect of increasing deltaP on Membrane porosity was also tested by comparing air seeding thresholds (P(a)) in stems perfused with water or a solution with lower surface tension. Air seeding and colloidal gold experiments indicated that Pit Membrane porosity increased significantly with deltaP in F. americana. In S. japonica, increases in permeability to colloidal gold with deltaP were small and maximum pore diameters predicted from P(a) were independent of deltaP, suggesting that vestures limited the degree to which the Membrane can be deflected from the centre of the Pit cavity. This provides the first experimental evidence that vestures reduce the probability of air seeding through Pit Membranes.
Sherwin Carlquist - One of the best experts on this subject based on the ideXlab platform.
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Distinctive tracheid microstructure in stems of Victoria and Euryale (Nymphaeaceae).
Botanical Journal of the Linnean Society, 2020Co-Authors: Sherwin Carlquist, Edward L SchneiderAbstract:Scanning electron microscopy (SEM) photographs of thick sections from liquid-preserved stems of Victoria cruziana and Euryale ferox show accretions of coarse fibrils on Pit Membranes of tracheids. The first-deposited fibrils are randomly orientated; on top of them (facing the tracheid lumina) are axially orientated coarse fibrils. The two systems are interconnected. Axially orientated fibrils were more extensively observed in Euryale than in Victoria and tips of fibrils in Euryale extend over the Pit apertures onto secondary wall surfaces. Tracheid–parenchyma interfaces bear rudimentary coarse fibrils on the tracheid side. End walls of Victoria tracheids have highly porose Pit Membranes, thinner and less complex than those of the lateral intertracheid walls. The structures reported in Victoria and Euryale are consistent with those concurrently reported for stems of other Nymphaeaceae. Although also present in Cabombaceae, the coarse fibrils are otherwise not reported for stems of angiosperms and are not yet reported in roots of any species. Pit Membrane remnants in perforation plates of various woody dicotyledons represent a nonhomologous phenomenon. The accretions of coarse fibrils in stem tracheids of Nymphaeaceae do not appear to enhance conduction, although they do contain porosities interconnecting tracheids. Removal of Pit Membrane remnants from perforation plates of primitive dicotyledon woods by hydrolysis does, on the contrary, suggest conduction enhancement. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159, 52–57.
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origins and nature of vessels in monocotyledons 12 Pit Membrane microstructure diversity in tracheary elements of astelia
Pacific Science, 2010Co-Authors: Sherwin Carlquist, Edward L SchneiderAbstract:Abstract: Xylem of stems and roots of three species of Astelia, a monocot with relatively unspecialized xylem, was examined with scanning electron microscopy (SEM) to better understand structural conditions intermediate between tracheids and vessel elements. Both macerations and hand-sectioned material were studied. Tracheary elements of roots of Asteliaceae can be characterized as tracheids, with some degrees of transition to vessel elements. Pit Membrane remnants, which take the form of pores, reticula, or threads, are present commonly in end walls of tracheary elements of roots of Astelia. Stems of Astelia have tracheids with less-conspicuous porosities in the Pit Membranes of end walls than those of roots. Sectioned materials show that the porose (reticulate) cellulosic layers of the primary wall, which is embedded in a matrix of amorphous material, can be exposed to various degrees by the sectioning process; the cellulosic network faces the lumen, and the amorphous material is the compound middle lam...
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xylem of early angiosperms nuphar nymphaeaceae has novel tracheid microstructure1
American Journal of Botany, 2009Co-Authors: Sherwin Carlquist, Edward L Schneider, Barre C HellquistAbstract:: SEM studies of xylem of stems of Nuphar reveal a novel feature, not previously reported for any angiosperm. Pit Membranes of tracheid end walls are composed of coarse fibrils, densest on the distal (outside surface, facing the Pit of an adjacent cell) surface of the Pit Membrane of a tracheid, thinner, and disposed at various levels on the lumen side of a Pit Membrane. The fibrils tend to be randomly oriented on the distal face of the Pit Membrane; the innermost fibrils facing the lumen take the form of longitudinally oriented strands. Where most abundantly present, the fibrils tend to be disposed in a spongiform, three-dimensional pattern. Pores that interconnect tracheids are present within the fibrillar meshwork. Pit Membranes on lateral walls of stem tracheids bear variously diminished versions of this pattern. Pits of root tracheids are unlike those of stems in that the lumen side of Pit Membranes bears a reticulum revealed on the outer surface of the tracheid after most of the thickness of a Pit Membrane is shaved away by the sectioning process. No fibrillar texturing is visible on the root tracheid Pits when they are viewed from the inside of a tracheid. Tracheid end walls of roots do contain pores of various sizes in Pit Membranes. These root and stem patterns were seen in six species representing the two sections of Nuphar, plus one intersectional hybrid, as well as in one collection of Nymphaea, included for purposes of comparison. Differences between root and stem tracheids with respect to microstructure are consistent in all species studied. Microstructural patterns reported here for stem tracheid Pits of Nymphaeaceae are not like those of Chloranthaceae, Illiciaceae, or other basal angiosperms. They are not referable to any of the patterns reported for early vascular plants. The adaptational nature of the Pit Membrane structure in these tracheids is not apparent; microstructure of Pit Membranes in basal angiosperms is more diverse than thought prior to study with SEM.
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Pit Membrane remnants in perforation plates of hydrangeales with comments on Pit Membrane remnant occurrence physiological significance and phylogenetic distribution in dicotyledons
Botanical Journal of the Linnean Society, 2004Co-Authors: Sherwin Carlquist, Edward L SchneiderAbstract:Perforation plates from ten species of seven genera of Hydrangeales sensu Thorne were studied using scanning elec tron microscopy (SEM). The presence of Pit Membranes in perforations ranges from abundant, as in Carpenteria and Ilydrangea, to minimal, as in Deutzia, Escallonia and Fhiladelphus. Abnormally great Pit Membrane presence may result from the presence of secondary compounds that inhibit lysis, as in Quintinia serrata; such interference with the natural lysis process may or may not be evident from coarseness and irregularity of Pit Membrane surface and of threads composing the Pit Membrane remnants. The presence of Pit Membrane remnants in perforation plates is hypothesized to be a symplesiomorphy, found in a fraction of dicotyledons with scalarifonn perforation plates (but still in an appreciable number of species). Pit Membrane remnant presence may represent incomplete lysis of pri mary wall material (cellulose microfibrils) in species that occupy highly mesic habitats, where such impedance in the conductive stream does not have an appreciable negative s&ective value. This physiological interpretation of Pit Membrane remnants in perforations is enhanced by the phylogenetic distribution as well as the strongly mesic eco logical preferences of species that exempli’ this phenomenon in dicotyledons at large. Families with Pit Membrane presence in perforations are scattered throughout phylogenetic trees, but they occur most often in basal branches of major clades (superorders) or as basal branches of orders within the major clades. Further study will doubtless reveal other families and genera in which this phenomenon occurs, although it is readily detected only with SEM. Phylo genetic stages in the disappearance of Pit Membrane remnants from perforation plates are described, ranging from intact Pit Membranes except for presence of pores of various sizes, to presence of Membrane remnants only at lateral ends of perforations and in one or two perforations (arguably Pits) at the transition between a perforation plate and subadj scent lateral wall Pitting. Developmental study of the mechanism and timing of lysis of Pit Membranes in per forations, and assessment of the role of the conductive stream in their removal, are needed to enhance present under standing of vessel evolution. © 2004 The Linnean Society of London, Botanical Jottrnal of the Linnean Society, 2004, 146, 41—51. ADDITIONAL KEYWORDS: Cornales — ecological wood anatomy — Escalloniaceae — Ixerbaceae — Saxifragaceae — vessel evolution — wood evolution.
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perforation plate Pit Membrane remnants and other vessel details of clethraceae primitive features in wood of ericales
International Journal of Plant Sciences, 2004Co-Authors: Sherwin Carlquist, Edward K SchneiderAbstract:Wood of 12 species of Clethra was studied with SEM; wood features are illustrated here for eight of these. Pit Membrane remnants were observed in perforations of all species, although in some, the remnants occur only in the form of small webs at the lateral ends of perforations. Pit Membranes take the form of threads or porose sheets; the former are more common. Extensive Pit Membrane remnants are uncommon in tropical species and are more characteristic of temperate species, perhaps because of water flow characteristics. As with other dicotyledons, occurrence of Pit Membrane remnants in perforations is considered a primitive feature in Clethraceae. Pit Membrane remnants also occur in families of Ericales placed in primitive positions in the order and close to Clethraceae: Cyrillaceae and Sarraceniaceae. Bars of perforation plates are numerous and are prominently bordered. Grooves interconnecting Pit apertures occur in distal portions of vessel elements and are accompanied by pairs of ridges in some specie...
