Nitrogen recycling from the xylem in rice leaves: dependence upon metabolism and associated changes in xylem hydraulics

PubMed Central

Bailey, Karen J.

2016-01-01

Measurements of amino acids in the guttation fluid and in the xylem exudates of cut leaves from intact plants provide evidence of the remarkable efficiency with which these nitrogenous compounds are reabsorbed from the xylem sap. This could be achieved by mechanisms involving intercellular transport and/or metabolism. Developmental changes in transcripts and protein showed that transcripts for phosphoenolpyruvate carboxykinase (PEPCK) increased from the base to the leaf tip, and were markedly increased by supplying asparagine. Supplying amino acids also increased the amounts of protein of PEPCK and, to a lesser extent, of pyruvate, Pi dikinase. PEPCK is present in the hydathodes, stomata and vascular parenchyma of rice leaves. Evidence for the role of PEPCK was obtained by using 3-mercaptopicolinic acid (MPA), a specific inhibitor of PEPCK, and by using an activation-tagged rice line that had an increase in PEPCK activity, to show that activation of PEPCK resulted in a decrease in N in the guttation fluid and that treatment by MPA resulted in an increase in amino acids in the guttation fluid and xylem sap towards the leaf tip. Furthermore, increasing PEPCK activity decreased the amount of guttation fluid, whereas decreasing PEPCK activity increased the amount of xylem sap or guttation fluid towards the leaf tip. The findings suggest the following hypotheses: (i) both metabolism and transport are involved in xylem recycling and (ii) excess N is the signal involved in modulating xylem hydraulics, perhaps via nutrient regulation of water-transporting aquaporins. Water relations and vascular metabolism and transport are thus intimately linked. PMID:27053722

Compositions and methods for xylem-specific expression in plant cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Kyung-Hwan; Ko, Jae-Heung

The invention provides promoter sequences that regulate specific expression of operably linked sequences in developing xylem cells and/or in developing xylem tissue. The developing xylem-specific sequences are exemplified by the DX5, DX8, DX11, and DX15 promoters, portions thereof, and homologs thereof. The invention further provides expression vectors, cells, tissues and plants that contain the invention's sequences. The compositions of the invention and methods of using them are useful in, for example, improving the quantity (biomass) and/or the quality (wood density, lignin content, sugar content etc.) of expressed biomass feedstock products that may be used for bioenergy, biorefinary, and generating woodmore » products such as pulp, paper, and solid wood.« less

Nitrogen recycling from the xylem in rice leaves: dependence upon metabolism and associated changes in xylem hydraulics.

PubMed

Bailey, Karen J; Leegood, Richard C

2016-04-01

Measurements of amino acids in the guttation fluid and in the xylem exudates of cut leaves from intact plants provide evidence of the remarkable efficiency with which these nitrogenous compounds are reabsorbed from the xylem sap. This could be achieved by mechanisms involving intercellular transport and/or metabolism. Developmental changes in transcripts and protein showed that transcripts for phosphoenolpyruvate carboxykinase (PEPCK) increased from the base to the leaf tip, and were markedly increased by supplying asparagine. Supplying amino acids also increased the amounts of protein of PEPCK and, to a lesser extent, of pyruvate, Pi dikinase. PEPCK is present in the hydathodes, stomata and vascular parenchyma of rice leaves. Evidence for the role of PEPCK was obtained by using 3-mercaptopicolinic acid (MPA), a specific inhibitor of PEPCK, and by using an activation-tagged rice line that had an increase in PEPCK activity, to show that activation of PEPCK resulted in a decrease in N in the guttation fluid and that treatment by MPA resulted in an increase in amino acids in the guttation fluid and xylem sap towards the leaf tip. Furthermore, increasing PEPCK activity decreased the amount of guttation fluid, whereas decreasing PEPCK activity increased the amount of xylem sap or guttation fluid towards the leaf tip. The findings suggest the following hypotheses: (i) both metabolism and transport are involved in xylem recycling and (ii) excess N is the signal involved in modulating xylem hydraulics, perhaps via nutrient regulation of water-transporting aquaporins. Water relations and vascular metabolism and transport are thus intimately linked. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Verticillium Infection Triggers VASCULAR-RELATED NAC DOMAIN7–Dependent de Novo Xylem Formation and Enhances Drought Tolerance in Arabidopsis[W

PubMed Central

Reusche, Michael; Thole, Karin; Janz, Dennis; Truskina, Jekaterina; Rindfleisch, Sören; Drübert, Christine; Polle, Andrea; Lipka, Volker; Teichmann, Thomas

2012-01-01

The soilborne fungal plant pathogen Verticillium longisporum invades the roots of its Brassicaceae hosts and proliferates in the plant vascular system. Typical aboveground symptoms of Verticillium infection on Brassica napus and Arabidopsis thaliana are stunted growth, vein clearing, and leaf chloroses. Here, we provide evidence that vein clearing is caused by pathogen-induced transdifferentiation of chloroplast-containing bundle sheath cells to functional xylem elements. In addition, our findings suggest that reinitiation of cambial activity and transdifferentiation of xylem parenchyma cells results in xylem hyperplasia within the vasculature of Arabidopsis leaves, hypocotyls, and roots. The observed de novo xylem formation correlates with Verticillium-induced expression of the VASCULAR-RELATED NAC DOMAIN (VND) transcription factor gene VND7. Transgenic Arabidopsis plants expressing the chimeric repressor VND7-SRDX under control of a Verticillium infection-responsive promoter exhibit reduced de novo xylem formation. Interestingly, infected Arabidopsis wild-type plants show higher drought stress tolerance compared with noninfected plants, whereas this effect is attenuated by suppression of VND7 activity. Together, our results suggest that V. longisporum triggers a tissue-specific developmental plant program that compensates for compromised water transport and enhances the water storage capacity of infected Brassicaceae host plants. In conclusion, we provide evidence that this natural plant–fungus pathosystem has conditionally mutualistic features. PMID:23023171

Protein S-Nitrosylation Regulates Xylem Vessel Cell Differentiation in Arabidopsis.

PubMed

Kawabe, Harunori; Ohtani, Misato; Kurata, Tetsuya; Sakamoto, Tomoaki; Demura, Taku

2018-01-01

Post-translational modifications of proteins have important roles in the regulation of protein activity. One such modification, S-nitrosylation, involves the covalent binding of nitric oxide (NO)-related species to a cysteine residue. Recent work showed that protein S-nitrosylation has crucial functions in plant development and environmental responses. In the present study, we investigated the importance of protein S-nitrosylation for xylem vessel cell differentiation using a forward genetics approach. We performed ethyl methanesulfonate mutagenesis of a transgenic Arabidopsis 35S::VND7-VP16-GR line in which the activity of VASCULAR-RELATED NAC-DOMAIN7 (VND7), a key transcription factor involved in xylem vessel cell differentiation, can be induced post-translationally by glucocorticoid treatment, with the goal of obtaining suppressor mutants that failed to differentiate ectopic xylem vessel cells; we named these mutants suppressor of ectopic vessel cell differentiation induced by VND7 (seiv) mutants. We found the seiv1 mutant to be a recessive mutant in which ectopic xylem cell differentiation was inhibited, especially in aboveground organs. In seiv1 mutants, a single nucleic acid substitution (G to A) leading to an amino acid substitution (E36K) was present in the gene encoding S-NITROSOGLUTATHIONE REDUCTASE 1 (GSNOR1), which regulates the turnover of the natural NO donor, S-nitrosoglutathione. An in vitro S-nitrosylation assay revealed that VND7 can be S-nitrosylated at Cys264 and Cys320 located near the transactivation activity-related domains, which were shown to be important for transactivation activity of VND7 by transient reporter assay. Our results suggest crucial roles for GSNOR1-regulated protein S-nitrosylation in xylem vessel cell differentiation, partly through the post-translational modification of VND7. © The Author 2017. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions

Identification and expression analyses of new potential regulators of xylem development and cambium activity in cassava (Manihot esculenta).

PubMed

Siebers, Tyche; Catarino, Bruno; Agusti, Javier

2017-03-01

We have identified new potential regulators of xylem cell-type determination and cellular proliferation in cassava and studied their expression in roots. Results are highly relevant for cassava biotechnology. Cassava's root system is composed of two types of root that coexist in every individual: the fibrous and the storage roots. Whether a root becomes fibrous or storage depends on the xylem cell types that it develops: fibrous roots develop xylem fibres and vessels while storage roots develop parenchyma xylem, the starch-storing tissue. A crucial question in cassava root development is how the specific xylem cell types differentiate and proliferate in the fibrous and storage roots. Using phylogenetic, protein sequence and synteny analyses we identified (1) MeVND6, MeVND7.1, MeVND7.2, MeNST3.1 and MeNST3.2 as the potential cassava orthologues of the Arabidopsis regulators of xylem cell type determination AtVND6, AtVND7 and AtNST3; and (2) MeWOX4.1 and MeWOX4.2 as the potential cassava orthologues of the Arabidopsis cambium regulator AtWOX4. Fibrous and storage roots were anatomically characterised and tested for the expression of the identified genes. Results revealed that (1) MeVND7.1 and MeVND7.2 are expressed in the fibrous but not in the storage roots; (2) MeVND6 shows low expression in both root types; (3) MeNST3.1 is not expressed in the fibrous or storage roots, while MeNST3.2 is highly expressed in both root-types and (4) MeWOX4.1 and, to a higher level, MeWOX4.2 are expressed in both the fibrous and storage roots. Results open new avenues for research in cassava root development and for food security-oriented biotechnology programmes.

Wood anatomical correlates with theoretical conductivity and wood density across China: evolutionary evidence of the functional differentiation of axial and radial parenchyma

PubMed Central

Zheng, Jingming; Martínez-Cabrera, Hugo I.

2013-01-01

Background and Aims In recent years considerable effort has focused on linking wood anatomy and key ecological traits. Studies analysing large databases have described how these ecological traits vary as a function of wood anatomical traits related to conduction and support, but have not considered how these functions interact with cells involved in storage of water and carbohydrates (i.e. parenchyma cells). Methods We analyzed, in a phylogenetic context, the functional relationship between cell types performing each of the three xylem functions (conduction, support and storage) and wood density and theoretical conductivity using a sample of approx. 800 tree species from China. Key Results Axial parenchyma and rays had distinct evolutionary correlation patterns. An evolutionary link was found between high conduction capacity and larger amounts of axial parenchyma that is probably related to water storage capacity and embolism repair, while larger amounts of ray tissue have evolved with increased mechanical support and reduced hydraulic capacity. In a phylogenetic principal component analysis this association of axial parenchyma with increased conduction capacity and rays with wood density represented orthogonal axes of variation. In multivariate space, however, the proportion of rays might be positively associated with conductance and negatively with wood density, indicating flexibility in these axes in species with wide rays. Conclusions The findings suggest that parenchyma types may differ in function. The functional axes represented by different cell types were conserved across lineages, suggesting a significant role in the ecological strategies of the angiosperms. PMID:23904446

Assessing Conifer Ray Parenchyma for Ecological Studies: Pitfalls and Guidelines.

PubMed

von Arx, Georg; Arzac, Alberto; Olano, José M; Fonti, Patrick

2015-01-01

Ray parenchyma is an essential tissue for tree functioning and survival. This living tissue plays a major role for storage and transport of water, nutrients, and non-structural carbohydrates (NSC), thus regulating xylem hydraulics and growth. However, despite the importance of rays for tree carbon and water relations, methodological challenges hamper knowledge about ray intra- and inter-tree variability and its ecological meaning. In this study we provide a methodological toolbox for soundly quantifying spatial and temporal variability of different ray features. Anatomical ray features were surveyed in different cutting planes (cross-sectional, tangential, and radial) using quantitative image analysis on stem-wood micro-sections sampled from 41 mature Scots pines (Pinus sylvestris). The percentage of ray surface (PERPAR), a proxy for ray volume, was compared among cutting planes and between early- and latewood to assess measurement-induced variability. Different tangential ray metrics were correlated to assess their similarities. The accuracy of cross-sectional and tangential measurements for PERPAR estimates as a function of number of samples and the measured wood surface was assessed using bootstrapping statistical technique. Tangential sections offered the best 3D insight of ray integration into the xylem and provided the most accurate estimates of PERPAR, with 10 samples of 4 mm(2) showing an estimate within ±6.0% of the true mean PERPAR (relative 95% confidence interval, CI95), and 20 samples of 4 mm(2) showing a CI95 of ±4.3%. Cross-sections were most efficient for establishment of time series, and facilitated comparisons with other widely used xylem anatomical features. Earlywood had significantly lower PERPAR (5.77 vs. 6.18%) and marginally fewer initiating rays than latewood. In comparison to tangential sections, PERPAR was systematically overestimated (6.50 vs. 4.92%) and required approximately twice the sample area for similar accuracy. Radial cuttings

Assessing Conifer Ray Parenchyma for Ecological Studies: Pitfalls and Guidelines

PubMed Central

von Arx, Georg; Arzac, Alberto; Olano, José M.; Fonti, Patrick

2015-01-01

Ray parenchyma is an essential tissue for tree functioning and survival. This living tissue plays a major role for storage and transport of water, nutrients, and non-structural carbohydrates (NSC), thus regulating xylem hydraulics and growth. However, despite the importance of rays for tree carbon and water relations, methodological challenges hamper knowledge about ray intra- and inter-tree variability and its ecological meaning. In this study we provide a methodological toolbox for soundly quantifying spatial and temporal variability of different ray features. Anatomical ray features were surveyed in different cutting planes (cross-sectional, tangential, and radial) using quantitative image analysis on stem-wood micro-sections sampled from 41 mature Scots pines (Pinus sylvestris). The percentage of ray surface (PERPAR), a proxy for ray volume, was compared among cutting planes and between early- and latewood to assess measurement-induced variability. Different tangential ray metrics were correlated to assess their similarities. The accuracy of cross-sectional and tangential measurements for PERPAR estimates as a function of number of samples and the measured wood surface was assessed using bootstrapping statistical technique. Tangential sections offered the best 3D insight of ray integration into the xylem and provided the most accurate estimates of PERPAR, with 10 samples of 4 mm2 showing an estimate within ±6.0% of the true mean PERPAR (relative 95% confidence interval, CI95), and 20 samples of 4 mm2 showing a CI95 of ±4.3%. Cross-sections were most efficient for establishment of time series, and facilitated comparisons with other widely used xylem anatomical features. Earlywood had significantly lower PERPAR (5.77 vs. 6.18%) and marginally fewer initiating rays than latewood. In comparison to tangential sections, PERPAR was systematically overestimated (6.50 vs. 4.92%) and required approximately twice the sample area for similar accuracy. Radial cuttings

Plant GSK3 proteins regulate xylem cell differentiation downstream of TDIF-TDR signalling

NASA Astrophysics Data System (ADS)

Kondo, Yuki; Ito, Tasuku; Nakagami, Hirofumi; Hirakawa, Yuki; Saito, Masato; Tamaki, Takayuki; Shirasu, Ken; Fukuda, Hiroo

2014-03-01

During plant radial growth typically seen in trees, procambial and cambial cells act as meristematic cells in the vascular system to self-proliferate and differentiate into xylem cells. These two processes are regulated by a signalling pathway composed of a peptide ligand and its receptor; tracheary element differentiation inhibitory factor (TDIF) and TDIF RECEPTOR (TDR). Here we show that glycogen synthase kinase 3 proteins (GSK3s) are crucial downstream components of the TDIF signalling pathway suppressing xylem differentiation from procambial cells. TDR interacts with GSK3s at the plasma membrane and activates GSK3s in a TDIF-dependent fashion. Consistently, a specific inhibitor of plant GSK3s strongly induces xylem cell differentiation through BRI1-EMS SUPPRESSOR 1 (BES1), a well-known target transcription factor of GSK3s. Our findings provide insight into the regulation of cell fate determination in meristem maintenance.

Agatharesinol biosynthesis-related changes of ray parenchyma in sapwood sticks of Cryptomeria japonica during cell death.

PubMed

Nakaba, Satoshi; Arakawa, Izumi; Morimoto, Hikaru; Nakada, Ryogo; Bito, Nobumasa; Imai, Takanori; Funada, Ryo

2016-05-01

The work demonstrates a relationship between the biosynthesis of the secondary metabolite, agatharesinol, and cytological changes that occur in ray parenchyma during cell death in sapwood sticks of Cryptomeria japonica under humidity-regulated conditions. To characterize the death of ray parenchyma cells that accompanies the biosynthesis of secondary metabolites, we examined cell death in sapwood sticks of Cryptomeria japonica under humidity-regulated conditions. We monitored features of ray parenchyma cells, such as viability, the morphology of nuclei and vacuoles, and the amount of starch grains. In addition, we analyzed levels of agatharesinol, a heartwood norlignan, by gas chromatography-mass spectrometry in the same sapwood sticks. Dramatic changes in the amount of starch grains and in the level of agatharesinol occurred simultaneously. Therefore, the biosynthesis of agatharesinol appeared to originate from the breakdown of starch. Furthermore, we observed the expansion of vacuoles in ray parenchyma cells prior to other cytological changes at the final stage of cell death. In our experimental system, we were able to follow the process of cell death and to demonstrate relationships between cytological changes and the biosynthesis of a secondary metabolite during the death of ray parenchyma cells.

Outside-Xylem Vulnerability, Not Xylem Embolism, Controls Leaf Hydraulic Decline during Dehydration.

PubMed

Scoffoni, Christine; Albuquerque, Caetano; Brodersen, Craig R; Townes, Shatara V; John, Grace P; Bartlett, Megan K; Buckley, Thomas N; McElrone, Andrew J; Sack, Lawren

2017-02-01

Leaf hydraulic supply is crucial to maintaining open stomata for CO 2 capture and plant growth. During drought-induced dehydration, the leaf hydraulic conductance (K leaf ) declines, which contributes to stomatal closure and, eventually, to leaf death. Previous studies have tended to attribute the decline of K leaf to embolism in the leaf vein xylem. We visualized at high resolution and quantified experimentally the hydraulic vulnerability of xylem and outside-xylem pathways and modeled their respective influences on plant water transport. Evidence from all approaches indicated that the decline of K leaf during dehydration arose first and foremost due to the vulnerability of outside-xylem tissues. In vivo x-ray microcomputed tomography of dehydrating leaves of four diverse angiosperm species showed that, at the turgor loss point, only small fractions of leaf vein xylem conduits were embolized, and substantial xylem embolism arose only under severe dehydration. Experiments on an expanded set of eight angiosperm species showed that outside-xylem hydraulic vulnerability explained 75% to 100% of K leaf decline across the range of dehydration from mild water stress to beyond turgor loss point. Spatially explicit modeling of leaf water transport pointed to a role for reduced membrane conductivity consistent with published data for cells and tissues. Plant-scale modeling suggested that outside-xylem hydraulic vulnerability can protect the xylem from tensions that would induce embolism and disruption of water transport under mild to moderate soil and atmospheric droughts. These findings pinpoint outside-xylem tissues as a central locus for the control of leaf and plant water transport during progressive drought. © 2017 The author(s). All Rights Reserved.

Spatial organization of xylem cell walls by ROP GTPases and microtubule-associated proteins.

PubMed

Oda, Yoshihisa; Fukuda, Hiroo

2013-12-01

Proper patterning of cellulosic cell walls is critical for cell shaping and differentiation of plant cells. Cortical microtubule arrays regulate the deposition patterns of cellulose microfibrils by controlling the targeting and trajectory of cellulose synthase complexes. Although some microtubule-associated proteins (MAPs) regulate the arrangement of cortical microtubules, knowledge about the overall mechanism governing the spacing of cortical microtubules is still limited. Recent studies reveal that ROP GTPases and MAPs spatially regulate the assembly and disassembly of cortical microtubules in developing xylem cells, in which localized secondary cell walls are deposited. Here, we review recent insights into the regulation of xylem cell wall patterning by cortical microtubules, ROP GTPases, and MAPs. Copyright © 2013 Elsevier Ltd. All rights reserved.

Compositional analysis of Chinese water chestnut (Eleocharis dulcis) cell-wall material from parenchyma, epidermis, and subepidermal tissues.

PubMed

Grassby, Terri; Jay, Andrew J; Merali, Zara; Parker, Mary L; Parr, Adrian J; Faulds, Craig B; Waldron, Keith W

2013-10-09

Chinese water chestnut (Eleocharis dulcis (Burman f.) Trin ex Henschel) is a corm consumed globally in Oriental-style cuisine. The corm consists of three main tissues, the epidermis, subepidermis, and parenchyma; the cell walls of which were analyzed for sugar, phenolic, and lignin content. Sugar content, measured by gas chromatography, was higher in the parenchyma cell walls (931 μg/mg) than in the subepidermis (775 μg/mg) or epidermis (685 μg/mg). The alkali-extractable phenolic content, measured by high-performance liquid chromatography, was greater in the epidermal (32.4 μg/mg) and subepidermal cell walls (21.7 μg/mg) than in the cell walls of the parenchyma (12.3 μg/mg). The proportion of diferulic acids was higher in the parenchyma. The Klason lignin content of epidermal and subepidermal cell walls was ~15%. Methylation analysis of Chinese water chestnut cell-wall polysaccharides identified xyloglucan as the predominant hemicellulose in the parenchyma for the first time, and also a significant pectin component, similar to other nongraminaceous monocots.

Outside-Xylem Vulnerability, Not Xylem Embolism, Controls Leaf Hydraulic Decline during Dehydration1[CC-BY

PubMed Central

Townes, Shatara V.; Bartlett, Megan K.; Buckley, Thomas N.; McElrone, Andrew J.; Sack, Lawren

2017-01-01

Leaf hydraulic supply is crucial to maintaining open stomata for CO2 capture and plant growth. During drought-induced dehydration, the leaf hydraulic conductance (Kleaf) declines, which contributes to stomatal closure and, eventually, to leaf death. Previous studies have tended to attribute the decline of Kleaf to embolism in the leaf vein xylem. We visualized at high resolution and quantified experimentally the hydraulic vulnerability of xylem and outside-xylem pathways and modeled their respective influences on plant water transport. Evidence from all approaches indicated that the decline of Kleaf during dehydration arose first and foremost due to the vulnerability of outside-xylem tissues. In vivo x-ray microcomputed tomography of dehydrating leaves of four diverse angiosperm species showed that, at the turgor loss point, only small fractions of leaf vein xylem conduits were embolized, and substantial xylem embolism arose only under severe dehydration. Experiments on an expanded set of eight angiosperm species showed that outside-xylem hydraulic vulnerability explained 75% to 100% of Kleaf decline across the range of dehydration from mild water stress to beyond turgor loss point. Spatially explicit modeling of leaf water transport pointed to a role for reduced membrane conductivity consistent with published data for cells and tissues. Plant-scale modeling suggested that outside-xylem hydraulic vulnerability can protect the xylem from tensions that would induce embolism and disruption of water transport under mild to moderate soil and atmospheric droughts. These findings pinpoint outside-xylem tissues as a central locus for the control of leaf and plant water transport during progressive drought. PMID:28049739

Plasticity in variation of xylem and phloem cell characteristics of Norway spruce under different local conditions

PubMed Central

Gričar, Jožica; Prislan, Peter; de Luis, Martin; Gryc, Vladimír; Hacurová, Jana; Vavrčík, Hanuš; Čufar, Katarina

2015-01-01

There is limited information on intra-annual plasticity of secondary tissues of tree species growing under different environmental conditions. To increase the knowledge about the plasticity of secondary growth, which allows trees to adapt to specific local climatic regimes, we examined climate–radial growth relationships of Norway spruce [Picea abies (L.) H. Karst.] from three contrasting locations in the temperate climatic zone by analyzing tree-ring widths for the period 1932–2010, and cell characteristics in xylem and phloem increments formed in the years 2009–2011. Variation in the structure of xylem and phloem increments clearly shows that plasticity in seasonal dynamics of cambial cell production and cell differentiation exists on xylem and phloem sides. Anatomical characteristics of xylem and phloem cells are predominantly site-specific characteristics, because they varied among sites but were fairly uniform among years in trees from the same site. Xylem and phloem tissues formed in the first part of the growing season seemed to be more stable in structure, indicating their priority over latewood and late phloem for tree performance. Long-term climate and radial growth analyses revealed that growth was in general less dependent on precipitation than on temperature; however, growth sensitivity to local conditions differed among the sites. Only partial dependence of radial growth of spruce on climatic factors on the selected sites confirms its strategy to adapt the structure of wood and phloem increments to function optimally in local conditions. PMID:26442044

Infrared nanospectroscopy reveals the chemical nature of pit membranes in water-conducting cells of the plant xylem.

PubMed

Pereira, Luciano; Flores-Borges, Denisele; Bittencourt, Paulo; Mayer, Juliana; Kiyota, Eduardo; Araújo, Pedro; Jansen, Steven; Freitas, Raul; Oliveira, Rafael; Mazzafera, Paulo

2018-06-05

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. {copyright, serif} 2018 American Society of Plant Biologists. All rights reserved.

Two Complementary Mechanisms Underpin Cell Wall Patterning during Xylem Vessel Development.

PubMed

Schneider, Rene; Tang, Lu; Lampugnani, Edwin R; Barkwill, Sarah; Lathe, Rahul; Zhang, Yi; McFarlane, Heather E; Pesquet, Edouard; Niittyla, Totte; Mansfield, Shawn D; Zhou, Yihua; Persson, Staffan

2017-10-01

The evolution of the plant vasculature was essential for the emergence of terrestrial life. Xylem vessels are solute-transporting elements in the vasculature that possess secondary wall thickenings deposited in intricate patterns. Evenly dispersed microtubule (MT) bands support the formation of these wall thickenings, but how the MTs direct cell wall synthesis during this process remains largely unknown. Cellulose is the major secondary wall constituent and is synthesized by plasma membrane-localized cellulose synthases (CesAs) whose catalytic activity propels them through the membrane. We show that the protein CELLULOSE SYNTHASE INTERACTING1 (CSI1)/POM2 is necessary to align the secondary wall CesAs and MTs during the initial phase of xylem vessel development in Arabidopsis thaliana and rice ( Oryza sativa ). Surprisingly, these MT-driven patterns successively become imprinted and sufficient to sustain the continued progression of wall thickening in the absence of MTs and CSI1/POM2 function. Hence, two complementary principles underpin wall patterning during xylem vessel development. © 2017 American Society of Plant Biologists. All rights reserved.

Two Complementary Mechanisms Underpin Cell Wall Patterning during Xylem Vessel Development[OPEN

PubMed Central

Tang, Lu; Barkwill, Sarah; Lathe, Rahul; McFarlane, Heather E.

2017-01-01

The evolution of the plant vasculature was essential for the emergence of terrestrial life. Xylem vessels are solute-transporting elements in the vasculature that possess secondary wall thickenings deposited in intricate patterns. Evenly dispersed microtubule (MT) bands support the formation of these wall thickenings, but how the MTs direct cell wall synthesis during this process remains largely unknown. Cellulose is the major secondary wall constituent and is synthesized by plasma membrane-localized cellulose synthases (CesAs) whose catalytic activity propels them through the membrane. We show that the protein CELLULOSE SYNTHASE INTERACTING1 (CSI1)/POM2 is necessary to align the secondary wall CesAs and MTs during the initial phase of xylem vessel development in Arabidopsis thaliana and rice (Oryza sativa). Surprisingly, these MT-driven patterns successively become imprinted and sufficient to sustain the continued progression of wall thickening in the absence of MTs and CSI1/POM2 function. Hence, two complementary principles underpin wall patterning during xylem vessel development. PMID:28947492

Xylem and phloem phenology in co-occurring conifers exposed to drought.

PubMed

Swidrak, Irene; Gruber, Andreas; Oberhuber, Walter

2014-01-01

Variability in xylem and phloem phenology among years and species is caused by contrasting temperatures prevailing at the start of the growing season and species-specific sensitivity to drought. The focus of this study was to determine temporal dynamics of xylem and phloem formation in co-occurring deciduous and evergreen coniferous species in a dry inner Alpine environment (750 m a.s.l., Tyrol, Austria). By repeated micro-sampling of the stem, timing of key phenological dates of xylem and phloem formation was compared among mature Pinus sylvestris , Larix decidua and Picea abies during two consecutive years. Xylem formation in P. sylvestris started in mid and late April 2011 and 2012, respectively, and in both years about 2 week later in P. abies and L. decidua . Phloem formation preceded xylem formation on average by 3 week in P. sylvestris , and c . 5 week in P. abies and L. decidua . Based on modeled cell number increase, tracheid production peaked between early through late May 2011 and late May through mid-June 2012. Phloem formation culminated between late April and mid-May in 2011 and in late May 2012. Production of xylem and phloem cells continued for about 4 and 5-6 months, respectively. High variability in xylem increment among years and species is related to exogenous control by climatic factors and species-specific sensitivity to drought, respectively. On the other hand, production of phloem cells was quite homogenous and showed asymptotic decrease with respect to xylem cells indicating endogenous control. Results indicate that onset and culmination of xylem and phloem formation are controlled by early spring temperature, whereby strikingly advanced production of phloem compared to xylem cells suggests lower temperature requirement for initiation of the former.

Uptake of water via branches helps timberline conifers refill embolized xylem in late winter.

PubMed

Mayr, Stefan; Schmid, Peter; Laur, Joan; Rosner, Sabine; Charra-Vaskou, Katline; Dämon, Birgit; Hacke, Uwe G

2014-04-01

Xylem embolism is a limiting factor for woody species worldwide. Conifers at the alpine timberline are exposed to drought and freeze-thaw stress during winter, which induce potentially lethal embolism. Previous studies indicated that timberline trees survive by xylem refilling. In this study on Picea abies, refilling was monitored during winter and spring seasons and analyzed in the laboratory and in situ experiments, based on hydraulic, anatomical, and histochemical methods. Refilling started in late winter, when the soil was frozen and soil water not available for the trees. Xylem embolism caused up to 86.2% ± 3.1% loss of conductivity and was correlated with the ratio of closed pits. Refilling of xylem as well as recovery in shoot conductance started in February and corresponded with starch accumulation in secondary phloem and in the mesophyll of needles, where we also observed increasing aquaporin densities in the phloem and endodermis. This indicates that active, cellular processes play a role for refilling even under winter conditions. As demonstrated by our experiments, water for refilling was thereby taken up via the branches, likely by foliar water uptake. Our results suggest that refilling is based on water shifts to embolized tracheids via intact xylem, phloem, and parenchyma, whereby aquaporins reduce resistances along the symplastic pathway and aspirated pits facilitate isolation of refilling tracheids. Refilling must be taken into account as a key process in plant hydraulics and in estimating future effects of climate change on forests and alpine tree ecosystems.

Xylem phenology and wood production: resolving the chicken-or-egg dilemma.

PubMed

Lupi, Carlo; Morin, Hubert; Deslauriers, Annie; Rossi, Sergio

2010-10-01

Delays in the start of the growing season reduce the period available for growth and the amount of xylem production. However, a higher number of developing tracheids could prolong cell differentiation and, consequently, lengthen the growing season. The relationship between the amount and duration of cell production in the xylem remains an unresolved issue. The aim of this study was to resolve the chicken-or-egg causality dilemma about duration of growth and cell production through simple- and double-cause models. This was achieved by (1) analysing the intra-annual growth dynamics of the xylem in Picea mariana (Mill.) BSP during 2006-2009 in two contrasting sites of the boreal forest of Quebec, Canada, and (2) extracting the dates of onset and ending of xylem formation and the number of radial cells along the tree ring. A higher number of cells was linked to an earlier onset (r=0.74) and later ending (r=0.61) of cell differentiation. The absence of a relationship between the residuals of the onset and ending of xylogenesis (r(p)=-0.06) indicated that cell production influenced the correlation between the two phenophases of the xylem. These results demonstrated that a higher number of cells produced delay the ending of xylem maturation, so extending the duration of wood formation. © 2010 Blackwell Publishing Ltd.

Effects of Grape Xylem Sap and Cell-Wall Constituents on In Vitro Growth, Biofilm Formation and Cellular Aggregation of Xylella fastidiosa

USDA-ARS?s Scientific Manuscript database

Purified cell-wall constituents or grape xylem sap added to media affected in vitro growth, biofilm formation, cell aggregation and gene expression of Xylella fastidiosa. Media containing xylem sap from Pierce’s disease (PD)-susceptible plants provided better support for bacterial growth and biofil...

Cell Wall Modifications in Arabidopsis Plants with Altered α-l-Arabinofuranosidase Activity[C][W

PubMed Central

Chávez Montes, Ricardo A.; Ranocha, Philippe; Martinez, Yves; Minic, Zoran; Jouanin, Lise; Marquis, Mélanie; Saulnier, Luc; Fulton, Lynette M.; Cobbett, Christopher S.; Bitton, Frédérique; Renou, Jean-Pierre; Jauneau, Alain; Goffner, Deborah

2008-01-01

Although cell wall remodeling is an essential feature of plant growth and development, the underlying molecular mechanisms are poorly understood. This work describes the characterization of Arabidopsis (Arabidopsis thaliana) plants with altered expression of ARAF1, a bifunctional α-l-arabinofuranosidase/β-d-xylosidase (At3g10740) belonging to family 51 glycosyl-hydrolases. ARAF1 was localized in several cell types in the vascular system of roots and stems, including xylem vessels and parenchyma cells surrounding the vessels, the cambium, and the phloem. araf1 T-DNA insertional mutants showed no visible phenotype, whereas transgenic plants that overexpressed ARAF1 exhibited a delay in inflorescence emergence and altered stem architecture. Although global monosaccharide analysis indicated only slight differences in cell wall composition in both mutant and overexpressing lines, immunolocalization experiments using anti-arabinan (LM6) and anti-xylan (LM10) antibodies indicated cell type-specific alterations in cell wall structure. In araf1 mutants, an increase in LM6 signal intensity was observed in the phloem, cambium, and xylem parenchyma in stems and roots, largely coinciding with ARAF1 expression sites. The ectopic overexpression of ARAF1 resulted in an increase in LM10 labeling in the secondary walls of interfascicular fibers and xylem vessels. The combined ARAF1 gene expression and immunolocalization studies suggest that arabinan-containing pectins are potential in vivo substrates of ARAF1 in Arabidopsis. PMID:18344421

A potential role for xylem-phloem interactions in the hydraulic architecture of trees: effects of phloem girdling on xylem hydraulic conductance.

PubMed

Zwieniecki, Maciej A; Melcher, Peter J; Feild, Taylor S; Holbrook, N Michele

2004-08-01

We investigated phloem-xylem interactions in Acer rubrum L. and Acer saccharum Marsh. Our experimental method allowed us to determine xylem conductance of an intact branch by measuring the flow rate of water supplied at two delivery pressures to the cut end of a small side branch. We found that removal of bark tissue (phloem girdling) upstream of the point at which deionized water was delivered to the branch resulted in a decrease (24% for A. rubrum and 15% for A. saccharum) in branch xylem hydraulic conductance. Declines in hydraulic conductance with girdling were accompanied by a decrease in the osmotic concentration of xylem sap. The decrease in xylem sap concentration following phloem girdling suggests that ion redistribution from the phloem was responsible for the observed decline in hydraulic conductance. When the same measurements were made on branches perfused with KCl solution (approximately 140 mOsm kg(-1)), phloem girdling had no effect on xylem hydraulic conductance. These results suggest a functional link between phloem and xylem hydraulic systems that is mediated by changes in the ionic content of the cell sap.

Cutting edge: control of Mycobacterium tuberculosis infection by a subset of lung parenchyma-homing CD4 T cells.

PubMed

Sakai, Shunsuke; Kauffman, Keith D; Schenkel, Jason M; McBerry, Cortez C; Mayer-Barber, Katrin D; Masopust, David; Barber, Daniel L

2014-04-01

Th1 cells are critical for containment of Mycobacterium tuberculosis infection, but little else is known about the properties of protective CD4 T cell responses. In this study, we show that the pulmonary Th1 response against M. tuberculosis is composed of two populations that are either CXCR3(hi) and localize to lung parenchyma or are CX3CR1(hi)KLRG1(hi) and are retained within lung blood vasculature. M. tuberculosis-specific parenchymal CD4 T cells migrate rapidly back into the lung parenchyma upon adoptive transfer, whereas the intravascular effectors produce the highest levels of IFN-γ in vivo. Importantly, parenchymal T cells displayed greater control of infection compared with the intravascular counterparts upon transfer into susceptible T cell-deficient hosts. Thus, we identified a subset of naturally generated M. tuberculosis-specific CD4 T cells with enhanced protective capacity and showed that control of M. tuberculosis correlates with the ability of CD4 T cells to efficiently enter the lung parenchyma rather than produce high levels of IFN-γ.

HURTLE CELLS IMMUNOHISTOCHEMICAL ACTIVITIES IN HASHIMOTO THYROIDITIS PARENCHYMA.

PubMed

Tsagareli, Z; Kvachadze, T; Melikadze, E; Metreveli, L; Nikobadze, E; Gogiashvili, L

2016-11-01

The present study was designed to evaluate the participation and utility of Hǘrtle cells morphological requirment and transformation under Hashimoto autoimmune thyroiditis versus Riedel´s struma. Several markers have been evaluated to detect induced activities of Hǘrtle cells. Study subject - specimens (tissue fragments) collected from TG surgery (thyroidectomy) for mollecular (receptor) diagnosis of Hǘrtle cells activities using routine histological and immunohistochemical samples. 89 cases were selected in Hashimoto thyroiditis diagnosis with Hǘrtle cells history (adenoma and adenomatous grouth of oncocytes). Markers as: TSH receptors, TTF-1, S-100 protein, also anti-TPO and anti-TG levels in blood plasm were detected. It was shown that solid cell claster-nests like agregation of oncocytes and adenomatous growth foci in parafollicular areas with anti-TPO and anti-TG antibodies levels arising while Riedel´s struma shown only large intra- and extra glandular inflammatory proliferative fibrosing process. Large positive expression of TTF-1 and S-100 protein and the negative reaction of TSH receptor factor suggest that Thyroid parenchyma disorganization and mollecular biological atypia with Hǘrtle cells are proceses due to hypothyreoidismus, as well as neuroectodermal cells prominent activities in 70% of Hashimoto cases.

Localization of Cell Wall Polysaccharides in Normal and Compression Wood of Radiata Pine: Relationships with Lignification and Microfibril Orientation1

PubMed Central

Donaldson, Lloyd A.; Knox, J. Paul

2012-01-01

The distribution of noncellulosic polysaccharides in cell walls of tracheids and xylem parenchyma cells in normal and compression wood of Pinus radiata, was examined to determine the relationships with lignification and cellulose microfibril orientation. Using fluorescence microscopy combined with immunocytochemistry, monoclonal antibodies were used to detect xyloglucan (LM15), β(1,4)-galactan (LM5), heteroxylan (LM10 and LM11), and galactoglucomannan (LM21 and LM22). Lignin and crystalline cellulose were localized on the same sections used for immunocytochemistry by autofluorescence and polarized light microscopy, respectively. Changes in the distribution of noncellulosic polysaccharides between normal and compression wood were associated with changes in lignin distribution. Increased lignification of compression wood secondary walls was associated with novel deposition of β(1,4)-galactan and with reduced amounts of xylan and mannan in the outer S2 (S2L) region of tracheids. Xylan and mannan were detected in all lignified xylem cell types (tracheids, ray tracheids, and thick-walled ray parenchyma) but were not detected in unlignified cell types (thin-walled ray parenchyma and resin canal parenchyma). Mannan was absent from the highly lignified compound middle lamella, but xylan occurred throughout the cell walls of tracheids. Using colocalization measurements, we confirmed that polysaccharides containing galactose, mannose, and xylose have consistent correlations with lignification. Low or unsubstituted xylans were localized in cell wall layers characterized by transverse cellulose microfibril orientation in both normal and compression wood tracheids. Our results support the theory that the assembly of wood cell walls, including lignification and microfibril orientation, may be mediated by changes in the amount and distribution of noncellulosic polysaccharides. PMID:22147521

Water relations in silver birch during springtime: How is sap pressurised?

PubMed

Hölttä, T; Dominguez Carrasco, M D R; Salmon, Y; Aalto, J; Vanhatalo, A; Bäck, J; Lintunen, A

2018-05-06

Positive sap pressures are produced in the xylem of birch trees in boreal conditions during the time between the thawing of the soil and bud break. During this period, xylem embolisms accumulated during wintertime are refilled with water. The mechanism for xylem sap pressurization and its environmental drivers are not well known. We measured xylem sap flow, xylem sap pressure, xylem sap osmotic concentration, xylem and whole stem diameter changes, and stem and root non-structural carbohydrate concentrations, along with meteorological conditions at two sites in Finland during and after the sap pressurisation period. The diurnal dynamics of xylem sap pressure and sap flow during the sap pressurisation period varied, but were more often opposite to the diurnal pattern after bud burst, i.e. sap pressure increased and sap flow rate mostly decreased when temperature increased. Net conversion of soluble sugars to starch in the stem and roots occurred during the sap pressurisation period. Xylem sap osmotic pressure was small in comparison to total sap pressure, and it did not follow changes in environmental conditions or tree water relations. Based on these findings, we suggest that xylem sap pressurisation and embolism refilling occur gradually over a few weeks through water transfer from parenchyma cells to xylem vessels during daytime, and then the parenchyma are refilled mostly during nighttime by water uptake from soil. Possible drivers for water transfer from parenchyma cells to vessels are discussed. Also the functioning of thermal dissipation probes in conditions of changing stem water content is discussed. © 2018 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands.

Comparative genomics reveals conservative evolution of the xylem transcriptome in vascular plants.

PubMed

Li, Xinguo; Wu, Harry X; Southerton, Simon G

2010-06-21

Wood is a valuable natural resource and a major carbon sink. Wood formation is an important developmental process in vascular plants which played a crucial role in plant evolution. Although genes involved in xylem formation have been investigated, the molecular mechanisms of xylem evolution are not well understood. We use comparative genomics to examine evolution of the xylem transcriptome to gain insights into xylem evolution. The xylem transcriptome is highly conserved in conifers, but considerably divergent in angiosperms. The functional domains of genes in the xylem transcriptome are moderately to highly conserved in vascular plants, suggesting the existence of a common ancestral xylem transcriptome. Compared to the total transcriptome derived from a range of tissues, the xylem transcriptome is relatively conserved in vascular plants. Of the xylem transcriptome, cell wall genes, ancestral xylem genes, known proteins and transcription factors are relatively more conserved in vascular plants. A total of 527 putative xylem orthologs were identified, which are unevenly distributed across the Arabidopsis chromosomes with eight hot spots observed. Phylogenetic analysis revealed that evolution of the xylem transcriptome has paralleled plant evolution. We also identified 274 conifer-specific xylem unigenes, all of which are of unknown function. These xylem orthologs and conifer-specific unigenes are likely to have played a crucial role in xylem evolution. Conifers have highly conserved xylem transcriptomes, while angiosperm xylem transcriptomes are relatively diversified. Vascular plants share a common ancestral xylem transcriptome. The xylem transcriptomes of vascular plants are more conserved than the total transcriptomes. Evolution of the xylem transcriptome has largely followed the trend of plant evolution.

Comparative genomics reveals conservative evolution of the xylem transcriptome in vascular plants

PubMed Central

2010-01-01

Background Wood is a valuable natural resource and a major carbon sink. Wood formation is an important developmental process in vascular plants which played a crucial role in plant evolution. Although genes involved in xylem formation have been investigated, the molecular mechanisms of xylem evolution are not well understood. We use comparative genomics to examine evolution of the xylem transcriptome to gain insights into xylem evolution. Results The xylem transcriptome is highly conserved in conifers, but considerably divergent in angiosperms. The functional domains of genes in the xylem transcriptome are moderately to highly conserved in vascular plants, suggesting the existence of a common ancestral xylem transcriptome. Compared to the total transcriptome derived from a range of tissues, the xylem transcriptome is relatively conserved in vascular plants. Of the xylem transcriptome, cell wall genes, ancestral xylem genes, known proteins and transcription factors are relatively more conserved in vascular plants. A total of 527 putative xylem orthologs were identified, which are unevenly distributed across the Arabidopsis chromosomes with eight hot spots observed. Phylogenetic analysis revealed that evolution of the xylem transcriptome has paralleled plant evolution. We also identified 274 conifer-specific xylem unigenes, all of which are of unknown function. These xylem orthologs and conifer-specific unigenes are likely to have played a crucial role in xylem evolution. Conclusions Conifers have highly conserved xylem transcriptomes, while angiosperm xylem transcriptomes are relatively diversified. Vascular plants share a common ancestral xylem transcriptome. The xylem transcriptomes of vascular plants are more conserved than the total transcriptomes. Evolution of the xylem transcriptome has largely followed the trend of plant evolution. PMID:20565927

Analysis of Xylem Sap from Functional (Nonembolized) and Nonfunctional (Embolized) Vessels of Populus nigra: Chemistry of Refilling1[C][W][OA

PubMed Central

Secchi, Francesca; Zwieniecki, Maciej A.

2012-01-01

It is assumed that the refilling of drought-induced embolism requires the creation of an osmotic gradient between xylem parenchyma cells and vessel lumens to generate the water efflux needed to fill the void. To assess the mechanism of embolism repair, it is crucial to determine if plants can up-regulate the efflux of osmotically active substances into embolized vessels and identify the major components of the released osmoticum. Here, we introduce a new approach of sap collection designed to separate water from nonembolized (functional) and embolized (nonfunctional) vessels. This new approach made possible the chemical analysis of liquid collected from both types of vessels in plants subjected to different levels of water stress. The technique also allowed us to determine the water volumes in nonfunctional vessels as a function of stress level. Overall, with the increase of water stress in plants, the osmotic potential of liquid collected from nonfunctional vessels increased while its volume decreased. These results revealed the presence of both sugars and ions in nonfunctional vessels at elevated levels in comparison with liquid collected from functional vessels, in which only traces of sugars were found. The increased sugar concentration was accompanied by decreased xylem sap pH. These results provide new insight into the biology of refilling, underlining the role of sugar and sugar transporters, and imply that a large degree of hydraulic compartmentalization must exist in the xylem during the refilling process. PMID:22837359

Differential expression of genes of Xylella fastidiosa in xylem fluid of citrus and grapevine.

PubMed

Shi, Xiangyang; Bi, Jianlong; Morse, Joseph G; Toscano, Nick C; Cooksey, Donald A

2010-03-01

Xylella fastidiosa causes a serious Pierce's disease (PD) in grapevine. Xylella fastidiosa cells from a PD strain were grown in a pure xylem fluid of a susceptible grapevine cultivar vs. xylem fluid from citrus, which is not a host for this strain of X. fastidiosa. When grown in grapevine xylem fluid, cells of the PD strain formed clumps and biofilm formed to a greater extent than in citrus xylem fluid, although the PD strain did grow in xylem fluid of three citrus varieties. The differential expression of selected genes of a PD X. fastidiosa strain cultured in the two xylem fluids was analyzed using a DNA macroarray. Compared with citrus xylem fluid, grapevine xylem fluid stimulated the expression of X. fastidiosa genes involved in virulence regulation, such as gacA, algU, xrvA, and hsq, and also genes involved in the biogenesis of pili and twitching motility, such as fimT, pilI, pilU, and pilY1. Increased gene expression likely contributes to PD expression in grapevine, whereas citrus xylem fluid did not support or possibly suppressed the expression of these virulence genes.

The accumulation pattern of ferruginol in the heartwood-forming Cryptomeria japonica xylem as determined by time-of-flight secondary ion mass spectrometry and quantity analysis

PubMed Central

Kuroda, Katsushi; Fujiwara, Takeshi; Hashida, Koh; Imai, Takanori; Kushi, Masayoshi; Saito, Kaori; Fukushima, Kazuhiko

2014-01-01

Background and Aims Heartwood formation is a unique phenomenon of tree species. Although the accumulation of heartwood substances is a well-known feature of the process, the accumulation mechanism remains unclear. The aim of this study was to determine the accumulation process of ferruginol, a predominant heartwood substance of Cryptomeria japonica, in heartwood-forming xylem. Methods The radial accumulation pattern of ferruginol was examined from sapwood and through the intermediate wood to the heartwood by direct mapping using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The data were compared with quantitative results obtained from a novel method of gas chromatography analysis using laser microdissection sampling and with water distribution obtained from cryo-scanning electron microscopy. Key Results Ferruginol initially accumulated in the middle of the intermediate wood, in the earlywood near the annual ring boundary. It accumulated throughout the entire earlywood in the inner intermediate wood, and in both the earlywood and the latewood in the heartwood. The process of ferruginol accumulation continued for more than eight annual rings. Ferruginol concentration peaked at the border between the intermediate wood and heartwood, while the concentration was less in the latewood compared wiht the earlywood in each annual ring. Ferruginol tended to accumulate around the ray parenchyma cells. In addition, at the border between the intermediate wood and heartwood, the accumulation was higher in areas without water than in areas with water. Conclusions TOF-SIMS clearly revealed ferruginol distribution at the cellular level. Ferruginol accumulation begins in the middle of intermediate wood, initially in the earlywood near the annual ring boundary, then throughout the entire earlywood, and finally across to the whole annual ring in the heartwood. The heterogeneous timing of ferruginol accumulation could be related to the distribution of ray parenchyma cells

Sequential depolarization of root cortical and stelar cells induced by an acute salt shock - implications for Na(+) and K(+) transport into xylem vessels.

PubMed

Wegner, Lars H; Stefano, Giovanni; Shabala, Lana; Rossi, Marika; Mancuso, Stefano; Shabala, Sergey

2011-05-01

Early events in NaCl-induced root ion and water transport were investigated in maize (Zea mays L) roots using a range of microelectrode and imaging techniques. Addition of 100 mm NaCl to the bath resulted in an exponential drop in root xylem pressure, rapid depolarization of trans-root potential and a transient drop in xylem K(+) activity (A(K+) ) within ∼1 min after stress onset. At this time, no detectable amounts of Na(+) were released into the xylem vessels. The observed drop in A(K+) was unexpected, given the fact that application of the physiologically relevant concentrations of Na(+) to isolated stele has caused rapid plasma membrane depolarization and a subsequent K(+) efflux from the stelar tissues. This controversy was explained by the difference in kinetics of NaCl-induced depolarization between cortical and stelar cells. As root cortical cells are first to be depolarized and lose K(+) to the environment, this is associated with some K(+) shift from the stelar symplast to the cortex, resulting in K(+) being transiently removed from the xylem. Once Na(+) is loaded into the xylem (between 1 and 5 min of root exposure to NaCl), stelar cells become more depolarized, and a gradual recovery in A(K+) occurs. © 2011 Blackwell Publishing Ltd.

Uptake of Water via Branches Helps Timberline Conifers Refill Embolized Xylem in Late Winter1[C][W][OPEN

PubMed Central

Mayr, Stefan; Schmid, Peter; Laur, Joan; Rosner, Sabine; Charra-Vaskou, Katline; Dämon, Birgit; Hacke, Uwe G.

2014-01-01

Xylem embolism is a limiting factor for woody species worldwide. Conifers at the alpine timberline are exposed to drought and freeze-thaw stress during winter, which induce potentially lethal embolism. Previous studies indicated that timberline trees survive by xylem refilling. In this study on Picea abies, refilling was monitored during winter and spring seasons and analyzed in the laboratory and in situ experiments, based on hydraulic, anatomical, and histochemical methods. Refilling started in late winter, when the soil was frozen and soil water not available for the trees. Xylem embolism caused up to 86.2% ± 3.1% loss of conductivity and was correlated with the ratio of closed pits. Refilling of xylem as well as recovery in shoot conductance started in February and corresponded with starch accumulation in secondary phloem and in the mesophyll of needles, where we also observed increasing aquaporin densities in the phloem and endodermis. This indicates that active, cellular processes play a role for refilling even under winter conditions. As demonstrated by our experiments, water for refilling was thereby taken up via the branches, likely by foliar water uptake. Our results suggest that refilling is based on water shifts to embolized tracheids via intact xylem, phloem, and parenchyma, whereby aquaporins reduce resistances along the symplastic pathway and aspirated pits facilitate isolation of refilling tracheids. Refilling must be taken into account as a key process in plant hydraulics and in estimating future effects of climate change on forests and alpine tree ecosystems. PMID:24521876

Cold stability of microtubules in wood-forming tissues of conifers during seasons of active and dormant cambium.

PubMed

Begum, Shahanara; Shibagaki, Masaki; Furusawa, Osamu; Nakaba, Satoshi; Yamagishi, Yusuke; Yoshimoto, Joto; Jin, Hyun-O; Sano, Yuzou; Funada, Ryo

2012-01-01

The cold stability of microtubules during seasons of active and dormant cambium was analyzed in the conifers Abies firma, Abies sachalinensis and Larix leptolepis by immunofluorescence microscopy. Samples were fixed at room temperature and at a low temperature of 2-3°C to examine the effects of low temperature on the stability of microtubules. Microtubules were visible in cambium, xylem cells and phloem cells after fixation at room temperature during seasons of active and dormant cambium. By contrast, fixation at low temperature depolymerized microtubules in cambial cells, differentiating tracheids, differentiating xylem ray parenchyma and phloem ray parenchyma cells during the active season. However, similar fixation did not depolymerize microtubules during cambial dormancy in winter. Our results indicate that the stability of microtubules in cambial cells and cambial derivatives at low temperature differs between seasons of active and dormant cambium. Moreover, the change in the stability of microtubules that we observed at low temperature might be closely related to seasonal changes in the cold tolerance of conifers. In addition, low-temperature fixation depolymerized microtubules in cambial cells and differentiating cells that had thin primary cell walls, while such low-temperature fixation did not depolymerize microtubules in differentiating secondary xylem ray parenchyma cells and tracheids that had thick secondary cell walls. The stability of microtubules at low temperature appears to depend on the structure of the cell wall, namely, primary or secondary. Therefore, we propose that the secondary cell wall might be responsible for the cold stability of microtubules in differentiating secondary xylem cells of conifers.

Analysis of xylem formation in pine by cDNA sequencing

NASA Technical Reports Server (NTRS)

Allona, I.; Quinn, M.; Shoop, E.; Swope, K.; St Cyr, S.; Carlis, J.; Riedl, J.; Retzel, E.; Campbell, M. M.; Sederoff, R.;

Lengthening of the duration of xylogenesis engenders disproportionate increases in xylem production.

PubMed

Rossi, Sergio; Girard, Marie-Josée; Morin, Hubert

2014-07-01

In cold climates, the expected global warming will lead to earlier cambial resumptions in spring, with a resultant lengthening of the growing season but unknown consequences on forest productivity. The phenological traits of cambium activity and xylem formation were analyzed at a short time scale along a thermal gradient represented by an alti-latitudinal range from the 48th to 53rd parallels and covering the whole closed black-spruce [Picea mariana (Mill.) BSP] forest in Quebec, Canada. A hypothesis was tested that warmer temperatures influence cambium phenology, allowing longer duration and higher intensity of growth, and resulting in proportionally increased xylem production. From April to October 2012, cell division in cambium and post-cambial differentiation of xylem were observed on anatomical sections obtained from microcores collected weekly from the stem of fifty trees. The southern and warmer site was characterized by the highest radial growth, which corresponded to both the highest rates and longest durations of cell production. The differences in terms of xylem phenology and growth were marginal between the other sites. Xylem growth was positively correlated with rate and duration of cell production, with the latter explaining most variability in growth. Within the range analyzed, the relationship between temperature and most phenological phases of xylogenesis was linear. On the contrary, temperature was related with cell production according to an exponential pattern. Periods of xylogenesis of 14 days longer (+13.1%) corresponded to a massive increase in cell production (33 cells, +109%). This disproportionate change occurred at a May-September average temperature of ca. 14 °C and a snow-free period of 210-235 days. At the lower boundary of the distribution of black spruce, small environmental changes allowing marginal lengthening of the period of cell division could potentially lead to disproportionate increases in xylem cell production, with

Easy Come, Easy Go: Capillary Forces Enable Rapid Refilling of Embolized Primary Xylem Vessels.

PubMed

Rolland, Vivien; Bergstrom, Dana M; Lenné, Thomas; Bryant, Gary; Chen, Hua; Wolfe, Joe; Holbrook, N Michele; Stanton, Daniel E; Ball, Marilyn C

2015-08-01

Protoxylem plays an important role in the hydraulic function of vascular systems of both herbaceous and woody plants, but relatively little is known about the processes underlying the maintenance of protoxylem function in long-lived tissues. In this study, embolism repair was investigated in relation to xylem structure in two cushion plant species, Azorella macquariensis and Colobanthus muscoides, in which vascular water transport depends on protoxylem. Their protoxylem vessels consisted of a primary wall with helical thickenings that effectively formed a pit channel, with the primary wall being the pit channel membrane. Stem protoxylem was organized such that the pit channel membranes connected vessels with paratracheal parenchyma or other protoxylem vessels and were not exposed directly to air spaces. Embolism was experimentally induced in excised vascular tissue and detached shoots by exposing them briefly to air. When water was resupplied, embolized vessels refilled within tens of seconds (excised tissue) to a few minutes (detached shoots) with water sourced from either adjacent parenchyma or water-filled vessels. Refilling occurred in two phases: (1) water refilled xylem pit channels, simplifying bubble shape to a rod with two menisci; and (2) the bubble contracted as the resorption front advanced, dissolving air along the way. Physical properties of the protoxylem vessels (namely pit channel membrane porosity, hydrophilic walls, vessel dimensions, and helical thickenings) promoted rapid refilling of embolized conduits independent of root pressure. These results have implications for the maintenance of vascular function in both herbaceous and woody species, because protoxylem plays a major role in the hydraulic systems of leaves, elongating stems, and roots. © 2015 American Society of Plant Biologists. All Rights Reserved.

Xylem development in prunus flower buds and the relationship to deep supercooling.

PubMed

Ashworth, E N

1984-04-01

Xylem development in eight Prunus species was examined and the relationship to deep supercooling assessed. Dormant buds of six species, P. armeniaca, P. avium, P. cerasus, P. persica, P. salicina, and P. sargentii deep supercooled. Xylem vessel elements were not observed within the dormant floral primordia of these species. Instead, discrete bundles containing procambial cells were observed. Vascular differentiation resumed and xylem continuity was established during the time that the capacity to deep supercool was lost. In P. serotina and P. virginiana, two species which do not supercool, xylem vessels ran the length of the inflorescence and presumably provided a conduit for the spread of ice into the bud. The results support the hypothesis that the lack of xylem continuity is an important feature of buds which deep supercool.

Tolerance to oxidative stress is required for maximal xylem colonization by the xylem-limited bacterial phytopathogen, Xylella fastidiosa.

PubMed

Wang, Peng; Lee, Yunho; Igo, Michele M; Roper, M Caroline

2017-09-01

Bacterial plant pathogens often encounter reactive oxygen species (ROS) during host invasion. In foliar bacterial pathogens, multiple regulatory proteins are involved in the sensing of oxidative stress and the activation of the expression of antioxidant genes. However, it is unclear whether xylem-limited bacteria, such as Xylella fastidiosa, experience oxidative stress during the colonization of plants. Examination of the X. fastidiosa genome uncovered only one homologue of oxidative stress regulatory proteins, OxyR. Here, a knockout mutation in the X. fastidiosa oxyR gene was constructed; the resulting strain was significantly more sensitive to hydrogen peroxide (H 2 O 2 ) relative to the wild-type. In addition, during early stages of grapevine infection, the survival rate was 1000-fold lower for the oxyR mutant than for the wild-type. This supports the hypothesis that grapevine xylem represents an oxidative environment and that X. fastidiosa must overcome this challenge to achieve maximal xylem colonization. Finally, the oxyR mutant exhibited reduced surface attachment and cell-cell aggregation and was defective in biofilm maturation, suggesting that ROS could be a potential environmental cue stimulating biofilm development during the early stages of host colonization. © 2016 BSPP AND JOHN WILEY & SONS LTD.

Accumulation of sugars in the xylem apoplast observed under water stress conditions is controlled by xylem pH.

PubMed

Secchi, Francesca; Zwieniecki, Maciej A

2016-11-01

Severe water stress constrains, or even stops, water transport in the xylem due to embolism formation. Previously, the xylem of poplar trees was shown to respond to embolism formation by accumulating carbohydrates in the xylem apoplast and dropping xylem sap pH. We hypothesize that these two processes may be functionally linked as lower pH activates acidic invertases degrading sucrose and inducing accumulation of monosaccharides in xylem apoplast. Using a novel in vivo method to measure xylem apoplast pH, we show that pH drops from ~6.2 to ~5.6 in stems of severely stressed plants and rises following recovery of stem water status. We also show that in a lower pH environment, sugars are continuously accumulating in the xylem apoplast. Apoplastic carbohydrate accumulation was reduced significantly in the presence of a proton pump blocker (orthovanadate). These observations suggest that a balance in sugar concentrations exists between the xylem apoplast and symplast that can be controlled by xylem pH and sugar concentration. We conclude that lower pH is related to loss of xylem transport function, eventually resulting in accumulation of sugars that primes stems for recovery from embolism when water stress is relieved. © 2016 John Wiley & Sons Ltd.

Seasonal development of cambial activity in relation to xylem formation in Chinese fir.

PubMed

Wu, Hongyang; Xu, Huimin; Li, Hanyin; Wei, Dongmei; Lin, Jinxing; Li, Xiaojuan

2016-05-20

The vascular cambium is a lateral meristem which can differentiate into secondary phloem and xylem. The secondary growth of woody plants resulting from vascular cambium activity has been a focus of considerable attention, but the quantitative relationships between cambial activity and secondary xylem formation have been little studied. Our analysis of cytological changes in the cambium of Chinese fir (Cunninghamia lanceolata), revealed a significant positive correlation between vascular cambium cell numbers and cambium zone width through the seasonal cycle. Cambium cell numbers and the cambium cell radial diameter were closely related to xylem formation. Immuno-labeling showed that de-esterified homogalacturonan and (1-4)-β-d-galactan epitopes were highly abundant in cell walls of dormant-stage cambium, whereas high methylesterified homogalacturonan was strongly labeled in the active stage. Raman spectroscopy detected significant changes in the chemical composition of cell walls during the active-dormant stage transition. More pectin and less monolignols occurred in radial cell walls than in tangential walls during the dormant stage, but no significant changes were found in other stages, indicating that pectin accumulation facilitates cell wall expansion, with cambium activity transition. Our quantitative analysis of the relationship between cambial activity and xylem formation, as well as the cell wall modification during the active stage provides useful information about cambial characteristics and xylogenesis. Copyright © 2016. Published by Elsevier GmbH.

Comparative interrogation of the developing xylem transcriptomes of two wood-forming species: Populus trichocarpa and Eucalyptus grandis.

PubMed

Hefer, Charles A; Mizrachi, Eshchar; Myburg, Alexander A; Douglas, Carl J; Mansfield, Shawn D

2015-06-01

Wood formation is a complex developmental process governed by genetic and environmental stimuli. Populus and Eucalyptus are fast-growing, high-yielding tree genera that represent ecologically and economically important species suitable for generating significant lignocellulosic biomass. Comparative analysis of the developing xylem and leaf transcriptomes of Populus trichocarpa and Eucalyptus grandis together with phylogenetic analyses identified clusters of homologous genes preferentially expressed during xylem formation in both species. A conserved set of 336 single gene pairs showed highly similar xylem preferential expression patterns, as well as evidence of high functional constraint. Individual members of multi-gene orthologous clusters known to be involved in secondary cell wall biosynthesis also showed conserved xylem expression profiles. However, species-specific expression as well as opposite (xylem versus leaf) expression patterns observed for a subset of genes suggest subtle differences in the transcriptional regulation important for xylem development in each species. Using sequence similarity and gene expression status, we identified functional homologs likely to be involved in xylem developmental and biosynthetic processes in Populus and Eucalyptus. Our study suggests that, while genes involved in secondary cell wall biosynthesis show high levels of gene expression conservation, differential regulation of some xylem development genes may give rise to unique xylem properties. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Xylem Development in Prunus Flower Buds and the Relationship to Deep Supercooling

PubMed Central

Ashworth, Edward N.

1984-01-01

Xylem development in eight Prunus species was examined and the relationship to deep supercooling assessed. Dormant buds of six species, P. armeniaca, P. avium, P. cerasus, P. persica, P. salicina, and P. sargentii deep supercooled. Xylem vessel elements were not observed within the dormant floral primordia of these species. Instead, discrete bundles containing procambial cells were observed. Vascular differentiation resumed and xylem continuity was established during the time that the capacity to deep supercool was lost. In P. serotina and P. virginiana, two species which do not supercool, xylem vessels ran the length of the inflorescence and presumably provided a conduit for the spread of ice into the bud. The results support the hypothesis that the lack of xylem continuity is an important feature of buds which deep supercool. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 PMID:16663523

Lung parenchyma remodeling in a murine model of chronic allergic inflammation.

PubMed

Xisto, Debora G; Farias, Luciana L; Ferreira, Halina C; Picanço, Miguel R; Amitrano, Daniel; Lapa E Silva, Jose R; Negri, Elnara M; Mauad, Thais; Carnielli, Denise; Silva, Luiz Fernando F; Capelozzi, Vera L; Faffe, Debora S; Zin, Walter A; Rocco, Patricia R M

2005-04-15

This study tested the hypotheses that chronic allergic inflammation induces not only bronchial but also lung parenchyma remodeling, and that these histologic changes are associated with concurrent changes in respiratory mechanics. For this purpose, airway and lung parenchyma remodeling were evaluated by quantitative analysis of collagen and elastin, immunohistochemistry (smooth-muscle actin expression, eosinophil, and dendritic cell densities), and electron microscopy. In vivo (airway resistance, viscoelastic pressure, and static elastance) and in vitro (tissue elastance, resistance, and hysteresivity) respiratory mechanics were also analyzed. BALB/c mice were sensitized with ovalbumin and exposed to repeated ovalbumin challenges. A marked eosinophilic infiltration was seen in lung parenchyma and in large and distal airways. Neutrophils, lymphocytes, and dendritic cells also infiltrated the lungs. There was subepithelial fibrosis, myocyte hypertrophy and hyperplasia, elastic fiber fragmentation, and increased numbers of myofibroblasts in airways and lung parenchyma. Collagen fiber content was increased in the alveolar walls. The volume proportion of smooth muscle-specific actin was augmented in distal airways and alveolar duct walls. Airway resistance, viscoelastic pressure, static elastance, and tissue elastance and resistance were significantly increased. In conclusion, prolonged allergen exposure induced remodeling not only of the airway wall but also of the lung parenchyma, leading to in vivo and in vitro mechanical changes.

Weak tradeoff between xylem safety and xylem-specific hydraulic efficiency across the world's woody plant species.

PubMed

Gleason, Sean M; Westoby, Mark; Jansen, Steven; Choat, Brendan; Hacke, Uwe G; Pratt, Robert B; Bhaskar, Radika; Brodribb, Tim J; Bucci, Sandra J; Cao, Kun-Fang; Cochard, Hervé; Delzon, Sylvain; Domec, Jean-Christophe; Fan, Ze-Xin; Feild, Taylor S; Jacobsen, Anna L; Johnson, Daniel M; Lens, Frederic; Maherali, Hafiz; Martínez-Vilalta, Jordi; Mayr, Stefan; McCulloh, Katherine A; Mencuccini, Maurizio; Mitchell, Patrick J; Morris, Hugh; Nardini, Andrea; Pittermann, Jarmila; Plavcová, Lenka; Schreiber, Stefan G; Sperry, John S; Wright, Ian J; Zanne, Amy E

2016-01-01

The evolution of lignified xylem allowed for the efficient transport of water under tension, but also exposed the vascular network to the risk of gas emboli and the spread of gas between xylem conduits, thus impeding sap transport to the leaves. A well-known hypothesis proposes that the safety of xylem (its ability to resist embolism formation and spread) should trade off against xylem efficiency (its capacity to transport water). We tested this safety-efficiency hypothesis in branch xylem across 335 angiosperm and 89 gymnosperm species. Safety was considered at three levels: the xylem water potentials where 12%, 50% and 88% of maximal conductivity are lost. Although correlations between safety and efficiency were weak (r(2)  < 0.086), no species had high efficiency and high safety, supporting the idea for a safety-efficiency tradeoff. However, many species had low efficiency and low safety. Species with low efficiency and low safety were weakly associated (r(2)  < 0.02 in most cases) with higher wood density, lower leaf- to sapwood-area and shorter stature. There appears to be no persuasive explanation for the considerable number of species with both low efficiency and low safety. These species represent a real challenge for understanding the evolution of xylem. No claim to US government works. New Phytologist © 2015 New Phytologist Trust.

Xylem sap proteins.

PubMed

Biles, C L; Abeles, F B

1991-06-01

Xylem sap from apple (Malus domestica Borkh), peach (Prunus persica Batsch), and pear (Pyrus communis L.) twigs was collected by means of pressure extrusion. This sap contained a number of acidic peroxidases and other proteins. Two other sources of xylem sap used in this study were stem exudates and guttation fluid. Similar peroxidases were also found in stem exudates and guttation fluids of strawberry (Fragaria x ananassa Duch.), tomato (Lycopersicum esculentum L.), and cucumber (Cucumis sativus L.). Isoelectric focusing activity gels showed that two peroxidases (isoelectric point [pl] 9 and pl 4.6) were present in initial stem exudates collected in the first 30 minutes after excision. Subsequent samples of stem exudate collected contained only the pl 4.6 isozyme. The pl 4.6 peroxidase isozyme was also found in root tissue and guttation fluid. These observations suggest that roots produce and secrete the pl 4.6 peroxidase into xylem sap. Cucumber seedlings were treated with 100 microliters per liter ethylene for 16 hours and the exudate from decapitated hypocotyl stumps was collected over a 3 hour period. Ethylene increased the peroxidase activity of stem exudates and inhibited the amount of exudate released. These observations suggest that xylem sap peroxidase may play a role in plugging damaged vascular tissue.

Laccase Down-Regulation Causes Alterations in Phenolic Metabolism and Cell Wall Structure in Poplar1

PubMed Central

Ranocha, Philippe; Chabannes, Matthieu; Chamayou, Simon; Danoun, Saïda; Jauneau, Alain; Boudet, Alain-M.; Goffner, Deborah

2002-01-01

Laccases are encoded by multigene families in plants. Previously, we reported the cloning and characterization of five divergent laccase genes from poplar (Populus trichocarpa) xylem. To investigate the role of individual laccase genes in plant development, and more particularly in lignification, three independent populations of antisense poplar plants, lac3AS, lac90AS, and lac110AS with significantly reduced levels of laccase expression were generated. A repression of laccase gene expression had no effect on overall growth and development. Moreover, neither lignin content nor composition was significantly altered as a result of laccase suppression. However, one of the transgenic populations, lac3AS, exhibited a 2- to 3-fold increase in total soluble phenolic content. As indicated by toluidine blue staining, these phenolics preferentially accumulate in xylem ray parenchyma cells. In addition, light and electron microscopic observations of lac3AS stems indicated that lac3 gene suppression led to a dramatic alteration of xylem fiber cell walls. Individual fiber cells were severely deformed, exhibiting modifications in fluorescence emission at the primary wall/middle lamella region and frequent sites of cell wall detachment. Although a direct correlation between laccase gene expression and lignification could not be assigned, we show that the gene product of lac3 is essential for normal cell wall structure and integrity in xylem fibers. lac3AS plants provide a unique opportunity to explore laccase function in plants. PMID:12011346

Xylem hydraulic safety margins in woody plants: coordination of stomatal control of xylem tension with hydraulic capacitance

Treesearch

Frederick C. Meinzer; Daniel M. Johnson; Barbara Lachenbruch; Katherine A. McCulloh; David R. Woodruff

2009-01-01

The xylem pressure inducing 50% loss of hydraulic conductivity due to embolism (P50) is widely used for comparisons of xylem vulnerability among species and across aridity gradients. However, despite its utility as an index of resistance to catastrophic xylem failure under extreme drought, P50 may have no special...

Effects of Age and Size on Xylem Phenology in Two Conifers of Northwestern China.

PubMed

Zeng, Qiao; Rossi, Sergio; Yang, Bao

2017-01-01

The climatic signals that directly affect the trees can be registered by xylem during its growth. If the timings and duration of xylem formation change, xylogenesis can occur under different environmental conditions and subsequently be subject to different climatic signals. An experimental design was applied in the field to disentangle the effects of age and size on xylem phenology, and it challenges the hypothesis that the timings and dynamics of xylem growth are size-dependent. Intra-annual dynamics of xylem formation were monitored weekly during the growing seasons 2013 and 2014 in Chinese pine ( Pinus tabulaeformis ) and Qilian juniper ( Juniperus przewalskii ) with different sizes and ages in a semi-arid region of northwestern China. Cell differentiation started 3 weeks earlier in 2013 and terminated 1 week later in 2014 in small-young pines than in big-old pines. However, differences in the timings of growth reactivation disappeared when comparing the junipers with different sizes but similar age. Overall, 77 days were required for xylem differentiation to take place, but timings were shorter for older trees, which also exhibited smaller cell production. Results from this study suggest that tree age does play an important role in timings and duration of growth. The effect of age should also be considered to perform reliable responses of trees to climate.

Effects of Age and Size on Xylem Phenology in Two Conifers of Northwestern China

PubMed Central

Zeng, Qiao; Rossi, Sergio; Yang, Bao

2018-01-01

The climatic signals that directly affect the trees can be registered by xylem during its growth. If the timings and duration of xylem formation change, xylogenesis can occur under different environmental conditions and subsequently be subject to different climatic signals. An experimental design was applied in the field to disentangle the effects of age and size on xylem phenology, and it challenges the hypothesis that the timings and dynamics of xylem growth are size-dependent. Intra-annual dynamics of xylem formation were monitored weekly during the growing seasons 2013 and 2014 in Chinese pine (Pinus tabulaeformis) and Qilian juniper (Juniperus przewalskii) with different sizes and ages in a semi-arid region of northwestern China. Cell differentiation started 3 weeks earlier in 2013 and terminated 1 week later in 2014 in small-young pines than in big-old pines. However, differences in the timings of growth reactivation disappeared when comparing the junipers with different sizes but similar age. Overall, 77 days were required for xylem differentiation to take place, but timings were shorter for older trees, which also exhibited smaller cell production. Results from this study suggest that tree age does play an important role in timings and duration of growth. The effect of age should also be considered to perform reliable responses of trees to climate. PMID:29379517

Refilling of a Hydraulically Isolated Embolized Xylem Vessel: Model Calculations

PubMed Central

VESALA, TIMO; HÖLTTÄ, TEEMU; PERÄMÄKI, MARTTI; NIKINMAA, EERO

2003-01-01

When they are hydraulically isolated, embolized xylem vessels can be refilled, while adjacent vessels remain under tension. This implies that the pressure of water in the refilling vessel must be equal to the bubble gas pressure, which sets physical constraints for recovery. A model of water exudation into the cylindrical vessel and of bubble dissolution based on the assumption of hydraulic isolation is developed. Refilling is made possible by the turgor of the living cells adjacent to the refilling vessel, and by a reflection coefficient below 1 for the exchange of solutes across the interface between the vessel and the adjacent cells. No active transport of solutes is assumed. Living cells are also capable of importing water from the water‐conducting vessels. The most limiting factors were found to be the osmotic potential of living cells and the ratio of the volume of the adjacent living cells to that of the embolized vessel. With values for these of 1·5 MPa and 1, respectively, refilling times were in the order of hours for a broad range of possible values of water conductivity coefficients and effective diffusion distances for dissolved air, when the xylem water tension was below 0·6 MPa and constant. Inclusion of the daily pattern for xylem tension improved the simulations. The simulated gas pressure within the refilling vessel was in accordance with recent experimental results. The study shows that the refilling process is physically possible under hydraulic isolation, while water in surrounding vessels is under negative pressure. However, the osmotic potentials in the refilling vessel tend to be large (in the order of 1 MPa). Only if the xylem water tension is, at most, twice atmospheric pressure, the reflection coefficient remains close to 1 (0·95) and the ratio of the volume of the adjacent living cells to that of the embolized vessel is about 2, does the osmotic potential stay below 0·4 MPa. PMID:12588721

Arrangement of Cellulose Microfibrils in Walls of Elongating Parenchyma Cells

PubMed Central

Setterfield, G.; Bayley, S. T.

1958-01-01

The arrangement of cellulose microfibrils in walls of elongating parenchyma cells of Avena coleoptiles, onion roots, and celery petioles was studied in polarizing and electron microscopes by examining whole cell walls and sections. Walls of these cells consist firstly of regions containing the primary pit fields and composed of microfibrils oriented predominantly transversely. The transverse microfibrils show a progressive disorientation from the inside to the outside of the wall which is consistent with the multinet model of wall growth. Between the pit-field regions and running the length of the cells are ribs composed of longitudinally oriented microfibrils. Two types of rib have been found at all stages of cell elongation. In some regions, the wall appears to consist entirely of longitudinal microfibrils so that the rib forms an integral part of the wall. At the edges of such ribs the microfibrils can be seen to change direction from longitudinal in the rib to transverse in the pit-field region. Often, however, the rib appears to consist of an extra separate layer of longitudinal microfibrils outside a continuous wall of transverse microfibrils. These ribs are quite distinct from secondary wall, which consists of longitudinal microfibrils deposited within the primary wall after elongation has ceased. It is evident that the arrangement of cellulose microfibrils in a primary wall can be complex and is probably an expression of specific cellular differentiation. PMID:13563544

Transcriptome Analysis of the Phytobacterium Xylella fastidiosa Growing under Xylem-Based Chemical Conditions

PubMed Central

Ciraulo, Maristela Boaceff; Santos, Daiene Souza; Rodrigues, Ana Claudia de Freitas Oliveira; de Oliveira, Marcus Vinícius; Rodrigues, Tiago; de Oliveira, Regina Costa; Nunes, Luiz R.

2010-01-01

Xylella fastidiosa is a xylem-limited bacterium responsible for important plant diseases, like citrus-variegated chlorosis (CVC) and grapevine Pierce's disease (PD). Interestingly, in vitro growth of X. fastidiosa in chemically defined media that resemble xylem fluid has been achieved, allowing studies of metabolic processes used by xylem-dwelling bacteria to thrive in such nutrient-poor conditions. Thus, we performed microarray hybridizations to compare transcriptomes of X. fastidiosa cells grown in 3G10-R, a medium that resembles grape sap, and in Periwinkle Wilt (PW), the complex medium traditionally used to cultivate X. fastidiosa. We identified 299 transcripts modulated in response to growth in these media. Some 3G10R-overexpressed genes have been shown to be upregulated in cells directly isolated from infected plants and may be involved in plant colonization, virulence and environmental competition. In contrast, cells cultivated in PW show a metabolic switch associated with increased aerobic respiration and enhanced bacterial growth rates. PMID:20625415

Transcriptome analysis of the phytobacterium Xylella fastidiosa growing under xylem-based chemical conditions.

PubMed

Ciraulo, Maristela Boaceff; Santos, Daiene Souza; Rodrigues, Ana Claudia de Freitas Oliveira; de Oliveira, Marcus Vinícius; Rodrigues, Tiago; de Oliveira, Regina Costa; Nunes, Luiz R

2010-01-01

Xylella fastidiosa is a xylem-limited bacterium responsible for important plant diseases, like citrus-variegated chlorosis (CVC) and grapevine Pierce's disease (PD). Interestingly, in vitro growth of X. fastidiosa in chemically defined media that resemble xylem fluid has been achieved, allowing studies of metabolic processes used by xylem-dwelling bacteria to thrive in such nutrient-poor conditions. Thus, we performed microarray hybridizations to compare transcriptomes of X. fastidiosa cells grown in 3G10-R, a medium that resembles grape sap, and in Periwinkle Wilt (PW), the complex medium traditionally used to cultivate X. fastidiosa. We identified 299 transcripts modulated in response to growth in these media. Some 3G10R-overexpressed genes have been shown to be upregulated in cells directly isolated from infected plants and may be involved in plant colonization, virulence and environmental competition. In contrast, cells cultivated in PW show a metabolic switch associated with increased aerobic respiration and enhanced bacterial growth rates.

Defining the Diverse Cell Populations Contributing to Lignification in Arabidopsis Stems.

PubMed

Smith, Rebecca A; Schuetz, Mathias; Karlen, Steven D; Bird, David; Tokunaga, Naohito; Sato, Yasushi; Mansfield, Shawn D; Ralph, John; Samuels, A Lacey

2017-06-01

Many land plants evolved tall and sturdy growth habits due to specialized cells with thick lignified cell walls: tracheary elements that function in water transport and fibers that function in structural support. The objective of this study was to define how and when diverse cell populations contribute lignin precursors, monolignols, to secondary cell walls during lignification of the Arabidopsis ( Arabidopsis thaliana ) inflorescence stem. Previous work demonstrated that, when lignin biosynthesis is suppressed in fiber and tracheary element cells with thickened walls, fibers become lignin-depleted while vascular bundles still lignify, suggesting that nonlignifying neighboring xylem cells are contributing to lignification. In this work, we dissect the contributions of different cell types, specifically xylary parenchyma and fiber cells, to lignification of the stem using cell-type-specific promoters to either knock down an essential monolignol biosynthetic gene or to introduce novel monolignol conjugates. Analysis of either reductions in lignin in knockdown lines, or the addition of novel monolignol conjugates, directly identifies the xylary parenchyma and fiber cell populations that contribute to the stem lignification and the developmental timing at which each contribution is most important. © 2017 American Society of Plant Biologists. All Rights Reserved.

Transcriptome Response to Embolism Formation in Stems of Populus trichocarpa Provides Insight into Signaling and the Biology of Refilling1[W][OA

PubMed Central

Secchi, Francesca; Gilbert, Matthew E.; Zwieniecki, Maciej A.

2011-01-01

The mechanism of embolism repair in transpiring plants is still not understood, despite significant scientific effort. The refilling process is crucial to maintaining stem transport capacity and ensuring survival for plants experiencing dynamic changes in water stress. Refilling air-filled xylem vessels requires an energy and water source that can only be provided by adjacent living parenchyma cells. Here, we report an analysis of the transcriptome response of xylem parenchyma cells after embolism formation in Populus trichocarpa trees. Genes encoding aquaporins, ion transporters, and carbohydrate metabolic pathways were up-regulated, and there was a significant reduction in the expression of genes responding to oxidative stress. Thus, a novel view of the plant response to embolism emerges that suggests a role for oxygen in embolized vessels as a signal triggering xylem refilling and for the activity of cation transport as having a significant role in the generation of the energy gradient necessary to heal embolized vessels. These findings redefine current hypotheses surrounding the refilling phenomenon and provide insight into the complexity of the biological response to the seemingly simple physical event of xylem embolism formation. PMID:21951466

Antileukotriene Reverts the Early Effects of Inflammatory Response of Distal Parenchyma in Experimental Chronic Allergic Inflammation

PubMed Central

Gobbato, Nathália Brandão; de Souza, Flávia Castro Ribas; Fumagalli, Stella Bruna Napolitano; Lopes, Fernanda Degobbi Tenório Quirino dos Santos; Prado, Carla Máximo; Martins, Milton Arruda; Tibério, Iolanda de Fátima Lopes Calvo; Leick, Edna Aparecida

2013-01-01

Aims. Compare the effects of montelukast or dexamethasone in distal lung parenchyma and airway walls of guinea pigs (GP) with chronic allergic inflammation. Methods. GP have inhaled ovalbumin (OVA group-2x/week/4weeks). After the 4th inhalation, GP were treated with montelukast or dexamethasone. After 72 hours of the 7th inhalation, GP were anesthetised, and lungs were removed and submitted to histopathological evaluation. Results. Montelukast and dexamethasone treatments reduced the number of eosinophils in airway wall and distal lung parenchyma compared to OVA group (P < 0.05). On distal parenchyma, both treatments were effective in reducing RANTES, NF-κB, and fibronectin positive cells compared to OVA group (P < 0.001). Montelukast was more effective in reducing eotaxin positive cells on distal parenchyma compared to dexamethasone treatment (P < 0.001), while there was a more expressive reduction of IGF-I positive cells in OVA-D group (P < 0.001). On airway walls, montelukast and dexamethasone were effective in reducing IGF-I, RANTES, and fibronectin positive cells compared to OVA group (P < 0.05). Dexamethasone was more effective in reducing the number of eotaxin and NF-κB positive cells than Montelukast (P < 0.05). Conclusions. In this animal model, both treatments were effective in modulating allergic inflammation and remodeling distal lung parenchyma and airway wall, contributing to a better control of the inflammatory response. PMID:24151607

Arabinogalactan protein-rich cell walls, paramural deposits and ergastic globules define the hyaline bodies of rhinanthoid Orobanchaceae haustoria

PubMed Central

Pielach, Anna; Leroux, Olivier; Domozych, David S.; Knox, J. Paul; Popper, Zoë A.

2014-01-01

Background and Aims Parasitic plants obtain nutrients from their hosts through organs called haustoria. The hyaline body is a specialized parenchymatous tissue occupying the central parts of haustoria in many Orobanchaceae species. The structure and functions of hyaline bodies are poorly understood despite their apparent necessity for the proper functioning of haustoria. Reported here is a cell wall-focused immunohistochemical study of the hyaline bodies of three species from the ecologically important clade of rhinanthoid Orobanchaceae. Methods Haustoria collected from laboratory-grown and field-collected plants of Rhinanthus minor, Odontites vernus and Melampyrum pratense attached to various hosts were immunolabelled for cell wall matrix glycans and glycoproteins using specific monoclonal antibodies (mAbs). Key Results Hyaline body cell wall architecture differed from that of the surrounding parenchyma in all species investigated. Enrichment in arabinogalactan protein (AGP) epitopes labelled with mAbs LM2, JIM8, JIM13, JIM14 and CCRC-M7 was prominent and coincided with reduced labelling of de-esterified homogalacturonan with mAbs JIM5, LM18 and LM19. Furthermore, paramural bodies, intercellular deposits and globular ergastic bodies composed of pectins, xyloglucans, extensins and AGPs were common. In Rhinanthus they were particularly abundant in pairings with legume hosts. Hyaline body cells were not in direct contact with haustorial xylem, which was surrounded by a single layer of paratracheal parenchyma with thickened cell walls abutting the xylem. Conclusions The distinctive anatomy and cell wall architecture indicate hyaline body specialization. Altered proportions of AGPs and pectins may affect the mechanical properties of hyaline body cell walls. This and the association with a transfer-like type of paratracheal parenchyma suggest a role in nutrient translocation. Organelle-rich protoplasts and the presence of exceptionally profuse intra- and intercellular

Divergent climate response on hydraulic-related xylem anatomical traits of Picea abies along a 900-m altitudinal gradient.

PubMed

Castagneri, Daniele; Petit, Giai; Carrer, Marco

2015-12-01

Climate change can induce substantial modifications in xylem structure and water transport capacity of trees exposed to environmental constraints. To elucidate mechanisms of xylem plasticity in response to climate, we retrospectively analysed different cell anatomical parameters over tree-ring series in Norway spruce (Picea abies L. Karst.). We sampled 24 trees along an altitudinal gradient (1200, 1600 and 2100 m above sea level, a.s.l.) and processed 2335 ± 1809 cells per ring. Time series for median cell lumen area (MCA), cell number (CN), tree-ring width (RW) and tree-ring-specific hydraulic conductivity (Kr) were crossed with daily temperature and precipitation records (1926-2011) to identify climate influence on xylem anatomical traits. Higher Kr at the low elevation site was due to higher MCA and CN. These variables were related to different aspects of intra-seasonal climatic variability under different environmental conditions, with MCA being more sensitive to summer precipitation. Winter precipitation (snow) benefited most parameters in all the sites. Descending the gradient, sensitivity of xylem features to summer climate shifted mostly from temperature to precipitation. In the context of climate change, our results indicate that higher summer temperatures at high elevations will benefit cell production and xylem hydraulic efficiency, whereas reduced water availability at lower elevations could negatively affect tracheids enlargement and thus stem capacity to transport water. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

The chemical identity of intervessel pit membranes in Acer challenges hydrogel control of xylem hydraulic conductivity

PubMed Central

Klepsch, Matthias M.; Schmitt, Marco; Paul Knox, J.; Jansen, Steven

2016-01-01

Ion-mediated enhancement of the hydraulic conductivity of xylem tissue (i.e. the ionic effect) has been reported for various angiosperm species. One explanation of the ionic effect is that it is caused by the swelling and shrinking of intervessel pit membranes due to the presence of pectins and/or other cell-wall matrix polymers such as heteroxylans or arabinogalactan–proteins (AGPs) that may contain acidic sugars. Here, we examined the ionic effect for six Acer species and their pit membrane chemistry using immunocytochemistry, including antibodies against glycoproteins. Moreover, anatomical features related to the bordered pit morphology and vessel dimensions were investigated using light and electron microscopy. The ionic effect varied from 18 % (± 9) to 32 % (± 13). Epitopes of homogalacturonan (LM18) and xylan (LM11) were not detected in intervessel pit membranes. Negative results were also obtained for glycoproteins (extensin: LM1, JIM20; AGP glycan: LM2), although AGP (JIM13)-related epitopes were detected in parenchyma cells. The mean vessel length was significantly correlated with the magnitude of the ionic effect, unlike other pit or vessel-related characteristics. Our results suggest that intervessel pit membranes of Acer are unlikely to contain pectic or other acidic polysaccharides. Therefore, alternative explanations should be tested to clarify the ionic effect. PMID:27354661

Related B cell clones populate the meninges and parenchyma of patients with multiple sclerosis

PubMed Central

Lovato, Laura; Willis, Simon N.; Rodig, Scott J.; Caron, Tyler; Almendinger, Stefany E.; Howell, Owain W.; Reynolds, Richard; Hafler, David A.

2011-01-01

In the central nervous system of patients with multiple sclerosis, B cell aggregates populate the meninges, raising the central question as to whether these structures relate to the B cell infiltrates found in parenchymal lesions or instead, represent a separate central nervous system immune compartment. We characterized the repertoires derived from meningeal B cell aggregates and the corresponding parenchymal infiltrates from brain tissue derived primarily from patients with progressive multiple sclerosis. The majority of expanded antigen-experienced B cell clones derived from meningeal aggregates were also present in the parenchyma. We extended this investigation to include 20 grey matter specimens containing meninges, 26 inflammatory plaques, 19 areas of normal appearing white matter and cerebral spinal fluid. Analysis of 1833 B cell receptor heavy chain variable region sequences demonstrated that antigen-experienced clones were consistently shared among these distinct compartments. This study establishes a relationship between extraparenchymal lymphoid tissue and parenchymal infiltrates and defines the arrangement of B cell clones that populate the central nervous system of patients with multiple sclerosis. PMID:21216828

Related B cell clones populate the meninges and parenchyma of patients with multiple sclerosis.

PubMed

Lovato, Laura; Willis, Simon N; Rodig, Scott J; Caron, Tyler; Almendinger, Stefany E; Howell, Owain W; Reynolds, Richard; O'Connor, Kevin C; Hafler, David A

2011-02-01

In the central nervous system of patients with multiple sclerosis, B cell aggregates populate the meninges, raising the central question as to whether these structures relate to the B cell infiltrates found in parenchymal lesions or instead, represent a separate central nervous system immune compartment. We characterized the repertoires derived from meningeal B cell aggregates and the corresponding parenchymal infiltrates from brain tissue derived primarily from patients with progressive multiple sclerosis. The majority of expanded antigen-experienced B cell clones derived from meningeal aggregates were also present in the parenchyma. We extended this investigation to include 20 grey matter specimens containing meninges, 26 inflammatory plaques, 19 areas of normal appearing white matter and cerebral spinal fluid. Analysis of 1833 B cell receptor heavy chain variable region sequences demonstrated that antigen-experienced clones were consistently shared among these distinct compartments. This study establishes a relationship between extraparenchymal lymphoid tissue and parenchymal infiltrates and defines the arrangement of B cell clones that populate the central nervous system of patients with multiple sclerosis.

Lignin Composition and Structure Differs between Xylem, Phloem and Phellem in Quercus suber L.

PubMed Central

Lourenço, Ana; Rencoret, Jorge; Chemetova, Catarina; Gominho, Jorge; Gutiérrez, Ana; del Río, José C.; Pereira, Helena

2016-01-01

The composition and structure of lignin in different tissues—phellem (cork), phloem and xylem (wood)—of Quercus suber was studied. Whole cell walls and their respective isolated milled lignins were analyzed by pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS), two-dimensional nuclear magnetic resonance spectroscopy (2D-NMR) and derivatization followed by reductive cleavage (DFRC). Different tissues presented varied p-hydroxyphenyl:guaiacyl:syringyl (H:G:S) lignin compositions. Whereas lignin from cork has a G-rich lignin (H:G:S molar ratio 2:85:13), lignin from phloem presents more S-units (H:G:S molar ratio of 1:58:41) and lignin from xylem is slightly enriched in S-lignin (H:G:S molar ratio 1:45:55). These differences were reflected in the relative abundances of the different interunit linkages. Alkyl-aryl ethers (β–O–4′) were predominant, increasing from 68% in cork, to 71% in phloem and 77% in xylem, as consequence of the enrichment in S-lignin units. Cork lignin was enriched in condensed structures such as phenylcoumarans (β-5′, 20%), dibenzodioxocins (5–5′, 5%), as corresponds to a lignin enriched in G-units. In comparison, lignin from phloem and xylem presented lower levels of condensed linkages. The lignin from cork was highly acetylated at the γ-OH of the side-chain (48% lignin acetylation), predominantly over G-units; while the lignins from phloem and xylem were barely acetylated and this occurred mainly over S-units. These results are a first time overview of the lignin structure in xylem, phloem (generated by cambium), and in cork (generated by phellogen), in agreement with literature that reports that lignin biosynthesis is flexible and cell specific. PMID:27833631

Palaeo‐adaptive Properties of the Xylem of Metasequoia: Mechanical/Hydraulic Compromises

PubMed Central

JAGELS, RICHARD; VISSCHER, GEORGE E.; LUCAS, JOHN; GOODELL, BARRY

2003-01-01

The xylem of Metasequoia glyptostroboides Hu et Cheng is characterized by very low density (average specific gravity = 0·27) and tracheids with relatively large dimensions (length and diameter). The microfibril angle in the S2 layer of tracheid walls is large, even in outer rings, suggesting a cambial response to compressive rather than tensile stresses. In some cases, this compressive stress is converted to irreversible strain (plastic deformation), as evidenced by cell wall corrugations. The heartwood is moderately decay resistant, helping to prevent Brazier buckling. These xylem properties are referenced to the measured bending properties of modulus of rupture and modulus of elasticity, and compared with other low‐to‐moderate density conifers. The design strategy for Metasequoia is to produce a mechanically weak but hydraulically efficient xylem that permits rapid height growth and crown development to capture and dominate a wet site environment. The adaptability of these features to a high‐latitude Eocene palaeoenvironment is discussed. PMID:12763758

Palaeo-adaptive properties of the xylem of Metasequoia: mechanical/hydraulic compromises.

PubMed

Jagels, Richard; Visscher, George E; Lucas, John; Goodell, Barry

2003-07-01

The xylem of Metasequoia glyptostroboides Hu et Cheng is characterized by very low density (average specific gravity = 0.27) and tracheids with relatively large dimensions (length and diameter). The microfibril angle in the S2 layer of tracheid walls is large, even in outer rings, suggesting a cambial response to compressive rather than tensile stresses. In some cases, this compressive stress is converted to irreversible strain (plastic deformation), as evidenced by cell wall corrugations. The heartwood is moderately decay resistant, helping to prevent Brazier buckling. These xylem properties are referenced to the measured bending properties of modulus of rupture and modulus of elasticity, and compared with other low-to-moderate density conifers. The design strategy for Metasequoia is to produce a mechanically weak but hydraulically efficient xylem that permits rapid height growth and crown development to capture and dominate a wet site environment. The adaptability of these features to a high-latitude Eocene palaeoenvironment is discussed.

Electrophysiological approach to determine kinetic parameters of sucrose uptake by single sieve elements or phloem parenchyma cells in intact Vicia faba plants.

PubMed

Hafke, Jens B; Höll, Sabina-Roxana; Kühn, Christina; van Bel, Aart J E

2013-01-01

Apart from cut aphid stylets in combination with electrophysiology, no attempts have been made thus far to measure in vivo sucrose-uptake properties of sieve elements. We investigated the kinetics of sucrose uptake by single sieve elements and phloem parenchyma cells in Vicia faba plants. To this end, microelectrodes were inserted into free-lying phloem cells in the main vein of the youngest fully-expanded leaf, half-way along the stem, in the transition zone between the autotrophic and heterotrophic part of the stem, and in the root axis. A top-to-bottom membrane potential gradient of sieve elements was observed along the stem (-130 mV to -110 mV), while the membrane potential of the phloem parenchyma cells was stable (approx. -100 mV). In roots, the membrane potential of sieve elements dropped abruptly to -55 mV. Bathing solutions having various sucrose concentrations were administered and sucrose/H(+)-induced depolarizations were recorded. Data analysis by non-linear least-square data fittings as well as by linear Eadie-Hofstee (EH) -transformations pointed at biphasic Michaelis-Menten kinetics (2 MM, EH: K m1 1.2-1.8 mM, K m2 6.6-9.0 mM) of sucrose uptake by sieve elements. However, Akaike's Information Criterion (AIC) favored single MM kinetics. Using single MM as the best-fitting model, K m values for sucrose uptake by sieve elements decreased along the plant axis from 1 to 7 mM. For phloem parenchyma cells, higher K m values (EH: K m1 10 mM, K m2 70 mM) as compared to sieve elements were found. In preliminary patch-clamp experiments with sieve-element protoplasts, small sucrose-coupled proton currents (-0.1 to -0.3 pA/pF) were detected in the whole-cell mode. In conclusion (a) K m values for sucrose uptake measured by electrophysiology are similar to those obtained with heterologous systems, (b) electrophysiology provides a useful tool for in situ determination of K m values, (c) As yet, it remains unclear if one or two uptake systems are involved in sucrose

Electrophysiological approach to determine kinetic parameters of sucrose uptake by single sieve elements or phloem parenchyma cells in intact Vicia faba plants

PubMed Central

Hafke, Jens B.; Höll, Sabina-Roxana; Kühn, Christina; van Bel, Aart J. E.

2013-01-01

Apart from cut aphid stylets in combination with electrophysiology, no attempts have been made thus far to measure in vivo sucrose-uptake properties of sieve elements. We investigated the kinetics of sucrose uptake by single sieve elements and phloem parenchyma cells in Vicia faba plants. To this end, microelectrodes were inserted into free-lying phloem cells in the main vein of the youngest fully-expanded leaf, half-way along the stem, in the transition zone between the autotrophic and heterotrophic part of the stem, and in the root axis. A top-to-bottom membrane potential gradient of sieve elements was observed along the stem (−130 mV to −110 mV), while the membrane potential of the phloem parenchyma cells was stable (approx. −100 mV). In roots, the membrane potential of sieve elements dropped abruptly to −55 mV. Bathing solutions having various sucrose concentrations were administered and sucrose/H+-induced depolarizations were recorded. Data analysis by non-linear least-square data fittings as well as by linear Eadie–Hofstee (EH) -transformations pointed at biphasic Michaelis–Menten kinetics (2 MM, EH: Km1 1.2–1.8 mM, Km2 6.6–9.0 mM) of sucrose uptake by sieve elements. However, Akaike's Information Criterion (AIC) favored single MM kinetics. Using single MM as the best-fitting model, Km values for sucrose uptake by sieve elements decreased along the plant axis from 1 to 7 mM. For phloem parenchyma cells, higher Km values (EH: Km1 10 mM, Km2 70 mM) as compared to sieve elements were found. In preliminary patch-clamp experiments with sieve-element protoplasts, small sucrose-coupled proton currents (−0.1 to −0.3 pA/pF) were detected in the whole-cell mode. In conclusion (a) Km values for sucrose uptake measured by electrophysiology are similar to those obtained with heterologous systems, (b) electrophysiology provides a useful tool for in situ determination of Km values, (c) As yet, it remains unclear if one or two uptake systems are involved

[The changes in contents and composition of phenolic acids during cell xylem growth in scots pine].

PubMed

Antonova, G F; Zheliznichenko, T V; Stasova, V V

2011-01-01

The contents and composition of alcohol soluble phenolic acids were studied during cell xylem growth in the course of wood annual increment formation in the stems of Scots pine. The cells of cambium zone, of two stages of expansion growth and the outset of secondary thickening zone (before lignification) were successively gathered from the stem segments of 25-old pine trees in the period of earlywood xylem formation with constant anatomical and histochemical control. The contents of free and bound forms of phenolic acids, isolated by 80% ethanol from tissues, as well as of their ethers and esters were calculated both per dry weight and per cell. The content and relation of the fractions and the composition of phenolic acid have been found to change significantly from cambium zone to the outset of tracheid secondary thickening. The character of the variations depends on a calculation method. According to the calculation per cell the amount of free and bound phenolic acids and in their composition of esters and especially ethers increased at the first step of expansion growth zone, decreased at the second one and rose again in the outset of secondary wall deposition. In dependence on the stage of cell development the pool of bound phenolic acids exceeded of free acid pool in 2-5 times. Sinapic and ferulic acids dominated in the composition of free hydroxycinnamic acids. The content and composition of hydroxycinnamic acids in ethers and esters depended on cell development phase. In cambium p-coumaric and sinapic acids were principal aglycons in ethers, at other stages these were sinapic and caffeic acids. The esters in cambium zone included essentially p-coumaric acid and at the other stages - sinapic and ferulic acids. At the first phase of growth benzoic acid was connected principally by ester bonds. The pool of these esters decreased from the first phase of growth to the outset of cell wall thickening and in proportion to this the level of free benzoic acid rose.

Applications of the compensating pressure theory of water transport.

PubMed

Canny, M

1998-07-01

Some predictions of the recently proposed theory of long-distance water transport in plants (the Compensating Pressure Theory) have been verified experimentally in sunflower leaves. The xylem sap cavitates early in the day under quite small water stress, and the compensating pressure P (applied as the tissue pressure of turgid cells) pushes water into embolized vessels, refilling them during active transpiration. The water potential, as measured by the pressure chamber or psychrometer, is not a measure of the pressure in the xylem, but (as predicted by the theory) a measure of the compensating pressure P. As transpiration increases, P is increased to provide more rapid embolism repair. In many leaf petioles this increase in P is achieved by the hydrolysis of starch in the starch sheath to soluble sugars. At night P falls as starch is reformed. A hypothesis is proposed to explain these observations by pressure-driven reverse osmosis of water from the ground parenchyma of the petiole. Similar processes occur in roots and are manifested as root pressure. The theory requires a pump to transfer water from the soil into the root xylem. A mechanism is proposed by which this pump may function, in which the endodermis acts as a one-way valve and a pressure-confining barrier. Rays and xylem parenchyma of wood act like the xylem parenchyma of petioles and roots to repair embolisms in trees. The postulated root pump permits a re-appraisal of the work done by evaporation during transpiration, leading to the proposal that in tall trees there is no hydrostatic gradient to be overcome in lifting water. Some published observations are re-interpreted in terms of the theory: doubt is cast on the validity of measurements of hydraulic conductance of wood; vulnerability curves are found not to measure the cavitation threshold of water in the xylem, but the osmotic pressure of the xylem parenchyma; if measures of xylem pressure and of hydraulic conductance are both suspect, the accepted

Direct Measurement of Xylem Pressure in Leaves of Intact Maize Plants. A Test of the Cohesion-Tension Theory Taking Hydraulic Architecture into Consideration1

PubMed Central

Wei, Chunfang; Tyree, Melvin T.; Steudle, Ernst

1999-01-01

The water relations of maize (Zea mays L. cv Helix) were documented in terms of hydraulic architecture and xylem pressure. A high-pressure flowmeter was used to characterize the hydraulic resistances of the root, stalk, and leaves. Xylem pressure measurements were made with a Scholander-Hammel pressure bomb and with a cell pressure probe. Evaporation rates were measured by gas exchange and by gravimetric measurements. Xylem pressure was altered by changing the light intensity, by controlling irrigation, or by gas pressure applied to the soil mass (using a root pressure bomb). Xylem pressure measured by the cell pressure probe and by the pressure bomb agreed over the entire measured range of 0 to −0.7 MPa. Experiments were consistent with the cohesion-tension theory. Xylem pressure changed rapidly and reversibly with changes in light intensity and root-bomb pressure. Increasing the root-bomb pressure increased the evaporation rate slightly when xylem pressure was negative and increased water flow rate through the shoots dramatically when xylem pressure was positive and guttation was observed. The hydraulic architecture model could predict all observed changes in water flow rate and xylem. We measured the cavitation threshold for oil- and water-filled pressure probes and provide some suggestions for improvement. PMID:10594106

Widening of xylem conduits in a conifer tree depends on the longer time of cell expansion downwards along the stem

PubMed Central

Anfodillo, Tommaso; Deslauriers, Annie; Menardi, Roberto; Tedoldi, Laura; Petit, Giai; Rossi, Sergio

2012-01-01

The diameter of vascular conduits increases towards the stem base. It has been suggested that this profile is an efficient anatomical feature for reducing the hydraulic resistance when trees grow taller. However, the mechanism that controls the cell diameter along the plant is not fully understood. The timing of cell differentiation along the stem was investigated. Cambial activity and cell differentiation were investigated in a Picea abies tree (11.5 m in height) collecting microsamples at nine different heights (from 1 to 9 m) along the stem with a 4 d time interval. Wood sections (8–12 μm thick) were stained and observed under a light microscope with polarized light to differentiate the developing xylem cells. Cell wall lignification was detected using cresyl violet acetate. The first enlarging cells appeared almost simultaneously along the tree axis indicating that cambium activation is not height-dependent. A significant increase in the duration of the cell expansion phase was observed towards the tree base: at 9 m from the ground, xylem cells expanded for 7 d, at 6 m for 14 d, and at 3 m for 19 d. The duration of the expansion phase is positively correlated with the lumen area of the tracheids (r2=0.68, P < 0.01) at the same height. By contrast, thickness of the cell wall of the earlywood did not show any trend with height. The lumen area of the conduits down the stem appeared linearly dependent on time during which differentiating cells remained in the expansion phase. However, the inductive signal of such long-distance patterned differentiation remains to be identified. PMID:22016427

Widening of xylem conduits in a conifer tree depends on the longer time of cell expansion downwards along the stem.

PubMed

Anfodillo, Tommaso; Deslauriers, Annie; Menardi, Roberto; Tedoldi, Laura; Petit, Giai; Rossi, Sergio

2012-01-01

The diameter of vascular conduits increases towards the stem base. It has been suggested that this profile is an efficient anatomical feature for reducing the hydraulic resistance when trees grow taller. However, the mechanism that controls the cell diameter along the plant is not fully understood. The timing of cell differentiation along the stem was investigated. Cambial activity and cell differentiation were investigated in a Picea abies tree (11.5 m in height) collecting microsamples at nine different heights (from 1 to 9 m) along the stem with a 4 d time interval. Wood sections (8-12 μm thick) were stained and observed under a light microscope with polarized light to differentiate the developing xylem cells. Cell wall lignification was detected using cresyl violet acetate. The first enlarging cells appeared almost simultaneously along the tree axis indicating that cambium activation is not height-dependent. A significant increase in the duration of the cell expansion phase was observed towards the tree base: at 9 m from the ground, xylem cells expanded for 7 d, at 6 m for 14 d, and at 3 m for 19 d. The duration of the expansion phase is positively correlated with the lumen area of the tracheids (r(2)=0.68, P < 0.01) at the same height. By contrast, thickness of the cell wall of the earlywood did not show any trend with height. The lumen area of the conduits down the stem appeared linearly dependent on time during which differentiating cells remained in the expansion phase. However, the inductive signal of such long-distance patterned differentiation remains to be identified.

Cambial Activity and Intra-annual Xylem Formation in Roots and Stems of Abies balsamea and Picea mariana

PubMed Central

Thibeault-Martel, Maxime; Krause, Cornelia; Morin, Hubert; Rossi, Sergio

2008-01-01

Background and Aims Studies on xylogenesis focus essentially on the stem, whereas there is basically no information about the intra-annual growth of other parts of the tree. As roots strongly influence carbon allocation and tree development, knowledge of the dynamics of xylem production and maturation in roots at a short time scale is required for a better understanding of the phenomenon of tree growth. This study compared cambial activity and xylem formation in stem and roots in two conifers of the boreal forest in Canada. Methods Wood microcores were collected weekly in stem and roots of ten Abies balsamea and ten Picea mariana during the 2004–2006 growing seasons. Cross-sections were cut using a rotary microtome, stained with cresyl violet acetate and observed under visible and polarized light. The number of cells in the cambial zone and in differentiation, plus the number of mature cells, was counted along the developing xylem. Key Results Xylem formation lasted from the end of May to the end of September, with no difference between stem and roots in 2004–2005. On the contrary, in 2006 a 1-week earlier beginning of cell differentiation was observed in the stem, with cell wall thickening and lignification in roots ending up to 22 d later than in the stem. Cell production in the stem was concentrated early in the season, in June, while most cell divisions in roots occurred 1 month later. Conclusions The intra-annual dynamics of growth observed in stem and roots could be related to the different amount of cells produced by the cambium and the patterns of air and soil temperature occurring in spring. PMID:18708643

Invasion of Peripheral Immune Cells into Brain Parenchyma after Cardiac Arrest and Resuscitation.

PubMed

Zhang, Can; Brandon, Nicole R; Koper, Kerryann; Tang, Pei; Xu, Yan; Dou, Huanyu

2018-06-01

Although a direct link has long been suspected between systemic immune responses and neuronal injuries after stroke, it is unclear which immune cells play an important role. A question remains as to whether the blood brain barrier (BBB) is transiently disrupted after circulatory arrest to allow peripheral immune cells to enter brain parenchyma. Here, we developed a clinically relevant cardiac arrest and resuscitation model in mice to investigate the BBB integrity using noninvasive magnetic resonance imaging. Changes in immune signals in the brain and periphery were assayed by immunohistochemistry and flow cytometry. Quantitative variance maps from T1-weighted difference images before and after blood-pool contrast clearance revealed BBB disruptions immediately after resuscitation and one day after reperfusion. Time profiles of hippocampal CA1 neuronal injuries correlated with the morphological changes of microglia activation. Cytotoxic T cells, CD11b + CD11c + dendritic cells, and CD11b + CD45 +hi monocytes and macrophages were significantly increased in the brain three days after cardiac arrest and resuscitation, suggesting direct infiltration of these cells following the BBB disruption. Importantly, these immune cell changes were coupled with a parallel increase in the same subset of immune cell populations in the bone marrow and blood. We conclude that neurovascular breakdown during the initial reperfusion phase contributes to the systemic immune cell invasion and subsequent neuropathogenesis affecting the long-term outcome after cardiac arrest and resuscitation.

Salivary enzymes are injected into xylem by the glassy-winged sharpshooter, a vector of Xylella fastidiosa.

PubMed

Backus, Elaine A; Andrews, Kim B; Shugart, Holly J; Carl Greve, L; Labavitch, John M; Alhaddad, Hasan

2012-07-01

A few phytophagous hemipteran species such as the glassy-winged sharpshooter, Homalodisca vitripennis, (Germar), subsist entirely on xylem fluid. Although poorly understood, aspects of the insect's salivary physiology may facilitate both xylem-feeding and transmission of plant pathogens. Xylella fastidiosa is a xylem-limited bacterium that causes Pierce's disease of grape and other scorch diseases in many important crops. X. fastidiosa colonizes the anterior foregut (precibarium and cibarium) of H. vitripennis and other xylem-feeding vectors. Bacteria form a dense biofilm anchored in part by an exopolysaccharide (EPS) matrix that is reported to have a β-1,4-glucan backbone. Recently published evidence supports the following, salivation-egestion hypothesis for the inoculation of X. fastidiosa during vector feeding. The insect secretes saliva into the plant and then rapidly takes up a mixture of saliva and plant constituents. During turbulent fluid movements in the precibarium, the bacteria may become mechanically and enzymatically dislodged; the mixture is then egested back out through the stylets into plant cells, possibly including xylem vessels. The present study found that proteins extracted from dissected H. vitripennis salivary glands contain several enzyme activities capable of hydrolyzing glycosidic linkages in polysaccharides such as those found in EPS and plant cell walls, based on current information about the structures of those polysaccharides. One of these enzymes, a β-1,4-endoglucanase (EGase) was enriched in the salivary gland protein extract by subjecting the extract to a few, simple purification steps. The EGase-enriched extract was then used to generate a polyclonal antiserum that was used for immunohistochemical imaging of enzymes in sharpshooter salivary sheaths in grape. Results showed that enzyme-containing gelling saliva is injected into xylem vessels during sharpshooter feeding, in one case being carried by the transpiration stream away

Ion-mediated changes of xylem hydraulic resistance in planta: fact or fiction?

PubMed

van Ieperen, Wim

2007-04-01

Although xylem provides an efficient transport pathway for water in plants, the hydraulic conductivity of xylem (K(h)) can still influence plant water status. For decades, the K(h) of functional xylem has been assumed to be constant in the short term because xylem consists of a network of dead interconnected capillary elements (conduits). Recent research has shown that K(h) can change in response to the cation content of the xylem fluid. Volume changes of pectin gel in nanometer-sized pores at inter-conduit connections are hypothesized to be the cause, and implications for xylem transport in planta are suggested. However, it seems too early to be conclusive about this phenomenon because the phenomenon has not been measured in planta with xylem fluids that realistically mimic natural xylem sap and the applied methods used to measure ion-mediated changes in K(h) have drawbacks.

Mobile Gibberellin Directly Stimulates Arabidopsis Hypocotyl Xylem Expansion[W][OA

PubMed Central

Ragni, Laura; Nieminen, Kaisa; Pacheco-Villalobos, David; Sibout, Richard; Schwechheimer, Claus; Hardtke, Christian S.

2011-01-01

Secondary growth of the vasculature results in the thickening of plant structures and continuously produces xylem tissue, the major biological carbon sink. Little is known about the developmental control of this quantitative trait, which displays two distinct phases in Arabidopsis thaliana hypocotyls. The later phase of accelerated xylem expansion resembles the secondary growth of trees and is triggered upon flowering by an unknown, shoot-derived signal. We found that flowering-dependent hypocotyl xylem expansion is a general feature of herbaceous plants with a rosette growth habit. Flowering induction is sufficient to trigger xylem expansion in Arabidopsis. By contrast, neither flower formation nor elongation of the main inflorescence is required. Xylem expansion also does not depend on any particular flowering time pathway or absolute age. Through analyses of natural genetic variation, we found that ERECTA acts locally to restrict xylem expansion downstream of the gibberellin (GA) pathway. Investigations of mutant and transgenic plants indicate that GA and its signaling pathway are both necessary and sufficient to directly trigger enhanced xylogenesis. Impaired GA signaling did not affect xylem expansion systemically, suggesting that it acts downstream of the mobile cue. By contrast, the GA effect was graft transmissible, suggesting that GA itself is the mobile shoot-derived signal. PMID:21498678

The proteomics of nitrogen remobilization in poplar bark

USDA-ARS?s Scientific Manuscript database

Seasonal nitrogen (N) cycling in temperate deciduous trees involves the accumulation of bark storage proteins (BSPs), a class of vegetative storage proteins in phloem parenchyma and xylem ray cells. BSPs are anabolized using recycled N in the form of amino acids after autumn leaf senescence and lat...

Water filtration using plant xylem.

PubMed

Boutilier, Michael S H; Lee, Jongho; Chambers, Valerie; Venkatesh, Varsha; Karnik, Rohit

2014-01-01

Effective point-of-use devices for providing safe drinking water are urgently needed to reduce the global burden of waterborne disease. Here we show that plant xylem from the sapwood of coniferous trees--a readily available, inexpensive, biodegradable, and disposable material--can remove bacteria from water by simple pressure-driven filtration. Approximately 3 cm(3) of sapwood can filter water at the rate of several liters per day, sufficient to meet the clean drinking water needs of one person. The results demonstrate the potential of plant xylem to address the need for pathogen-free drinking water in developing countries and resource-limited settings.

Effects of Fe and Mn deficiencies on the protein profiles of tomato (Solanum lycopersicum) xylem sap as revealed by shotgun analyses.

PubMed

Ceballos-Laita, Laura; Gutierrez-Carbonell, Elain; Takahashi, Daisuke; Abadía, Anunciación; Uemura, Matsuo; Abadía, Javier; López-Millán, Ana Flor

2018-01-06

The aim of this work was to study the effects of Fe and Mn deficiencies on the xylem sap proteome of tomato using a shotgun proteomic approach, with the final goal of elucidating plant response mechanisms to these stresses. This approach yielded 643 proteins reliably identified and quantified with 70% of them predicted as secretory. Iron and Mn deficiencies caused statistically significant and biologically relevant abundance changes in 119 and 118 xylem sap proteins, respectively. In both deficiencies, metabolic pathways most affected were protein metabolism, stress/oxidoreductases and cell wall modifications. First, results suggest that Fe deficiency elicited more stress responses than Mn deficiency, based on the changes in oxidative and proteolytic enzymes. Second, both nutrient deficiencies affect the secondary cell wall metabolism, with changes in Fe deficiency occurring via peroxidase activity, and in Mn deficiency involving peroxidase, Cu-oxidase and fasciclin-like arabinogalactan proteins. Third, the primary cell wall metabolism was affected by both nutrient deficiencies, with changes following opposite directions as judged from the abundances of several glycoside-hydrolases with endo-glycolytic activities and pectin esterases. Fourth, signaling pathways via xylem involving CLE and/or lipids as well as changes in phosphorylation and N-glycosylation also play a role in the responses to these stresses. Biological significance In spite of being essential for the delivery of nutrients to the shoots, our knowledge of xylem responses to nutrient deficiencies is very limited. The present work applies a shotgun proteomic approach to unravel the effects of Fe and Mn deficiencies on the xylem sap proteome. Overall, Fe deficiency seems to elicit more stress in the xylem sap proteome than Mn deficiency, based on the changes measured in proteolytic and oxido-reductase proteins, whereas both nutrients exert modifications in the composition of the primary and secondary

Brachypodium as an experimental system for the study of stem parenchyma biology in grasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jensen, Jacob Kruger; Wilkerson, Curtis Gene; Ma, Wujun

Stem parenchyma is a major cell type that serves key metabolic functions for the plant especially in large grasses, such as sugarcane and sweet sorghum, where it serves to store sucrose or other products of photosynthesis. It is therefore desirable to understand the metabolism of this cell type as well as the mechanisms by which it provides its function for the rest of the plant. Ultimately, this information can be used to selectively manipulate this cell type in a controlled manner to achieve crop improvement. In this study, we show that Brachypodium distachyon is a useful model system for stemmore » pith parenchyma biology. Brachypodium can be grown under condition where it resembles the growth patterns of important crops in that it produces large amounts of stem material with the lower leaves senescing and with significant stores of photosynthate located in the stem parenchyma cell types. We further characterize stem plastid morphology as a function of tissue types, as this organelle is central for a number of metabolic pathways, and quantify gene expression for the four main classes of starch biosynthetic genes. Notably, we find several of these genes differentially regulated between stem and leaf. Furthermore, these studies show, consistent with other grasses, that the stem functions as a specialized storage compartment in Brachypodium.« less

Brachypodium as an experimental system for the study of stem parenchyma biology in grasses

DOE PAGES

Jensen, Jacob Kruger; Wilkerson, Curtis Gene; Ma, Wujun

2017-03-01

Stem parenchyma is a major cell type that serves key metabolic functions for the plant especially in large grasses, such as sugarcane and sweet sorghum, where it serves to store sucrose or other products of photosynthesis. It is therefore desirable to understand the metabolism of this cell type as well as the mechanisms by which it provides its function for the rest of the plant. Ultimately, this information can be used to selectively manipulate this cell type in a controlled manner to achieve crop improvement. In this study, we show that Brachypodium distachyon is a useful model system for stemmore » pith parenchyma biology. Brachypodium can be grown under condition where it resembles the growth patterns of important crops in that it produces large amounts of stem material with the lower leaves senescing and with significant stores of photosynthate located in the stem parenchyma cell types. We further characterize stem plastid morphology as a function of tissue types, as this organelle is central for a number of metabolic pathways, and quantify gene expression for the four main classes of starch biosynthetic genes. Notably, we find several of these genes differentially regulated between stem and leaf. Furthermore, these studies show, consistent with other grasses, that the stem functions as a specialized storage compartment in Brachypodium.« less

Analysis of microstructures and macrotextures for different apple cultivars based on parenchyma morphology.

PubMed

Hou, Jumin; Sun, Yonghai; Chen, Fangyuan; Yu, Libo; Mao, Qian; Wang, Lu; Guo, Xiaolei; Liu, Chao

2016-04-01

Fuji, Golden Delicious, and Jonagold parenchyma were imaged by confocal laser scanning microscopy to be extracted morphology characteristics, which were used to analyze the relationship with macrotexture of apples tested by penetration and compression. Before analyzing the relationship, the significantly different morphology parameters were reduced in dimensions by principal component analysis and were proved to be availably used for distinguishing the different apple cultivars. For compression results, cell did not absolutely determine the hardness in different apple cultivars, and the pore should also be taken into consideration. With the same size in cell feret diameter, the bigger the pore feret diameter was, the softer the apple became. If no difference existed in pore feret diameter size, the cultivar became harder with a narrower distribution in cell feret diameter. The texture parameters were compared with the roundness parameters in the same or inverse changing trends to explore the relationship. High correlations were found between the texture parameters (energy required in whole penetration (Wt), fracture force (Fp), crispness) and pore solidity (R(2)  > 0.924, P < 0.001). Compactness of parenchyma played an important role in fruit texture. This research could provide the comprehension about relationship between microstructure and macrotexture of apple cultivars and morphological values for modeling apple parenchyma, contributing to numerical simulation for constitutive relation of fruit. © 2016 Wiley Periodicals, Inc.

Influence of Drought on the Hydraulic Efficiency and the Hydraulic Safety of the Xylem - Case of a Semi-arid Conifer.

NASA Astrophysics Data System (ADS)

Gentine, P.; Guerin, M. F.; von Arx, G.; Martin-Benito, D.; Griffin, K. L.; McDowell, N.; Pockman, W.; Andreu-Hayles, L.

2017-12-01

Recent droughts in the Southwest US have resulted in extensive mortality in the pinion pine population (Pinus Edulis). An important factor for resiliency is the ability of a plant to maintain a functional continuum between soil and leaves, allowing water's motion to be sustained or resumed. During droughts, loss of functional tracheids happens through embolism, which can be partially mitigated by increasing the hydraulic safety of the xylem. However, higher hydraulic safety is usually achieved by building narrower tracheids with thicker walls, resulting in a reduction of the hydraulic efficiency of the xylem (conductivity per unit area). Reduced efficiency constrains water transport, limits photosynthesis and might delay recovery after the drought. Supporting existing research on safety-efficiency tradeoff, we test the hypothesis that under dry conditions, isohydric pinions grow xylem that favor efficiency over safety. Using a seven-year experiment with three watering treatments (drought, control, irrigated) in New Mexico, we investigate the effect of drought on the xylem anatomy of pinions' branches. We also compare the treatment effect with interannual variations in xylem structure. We measure anatomical variables - conductivities, cell wall thicknesses, hydraulic diameter, cell reinforcement and density - and preliminarily conclude that treatment has little effect on hydraulic efficiency while hydraulic safety is significantly reduced under dry conditions. Taking advantage of an extremely dry year occurrence during the experiment, we find a sharp increase in vulnerability for xylem tissues built the same year.

Long-distance transport of mRNA via parenchyma cells and phloem across the host-parasite junction in Cuscuta.

PubMed

David-Schwartz, Rakefet; Runo, Steven; Townsley, Brad; Machuka, Jesse; Sinha, Neelima

2008-01-01

It has been shown that the parasitic plant dodder (Cuscuta pentagona) establishes a continuous vascular system through which water and nutrients are drawn. Along with solutes, viruses and proteins, mRNA transcripts are transported from the host to the parasite. The path of the transcripts and their stability in the parasite have yet to be revealed. To discover the route of mRNA transportation, the in situ reverse transcriptase-polymerase chain reaction (RT-PCR) technique was used to locally amplify host transcript within parasitic tissue. The stability of host mRNA molecules was also checked by monitoring specific transcripts along the growing dodder thread. Four mRNAs, alpha and beta subunits of PYROPHOSPHATE (PPi)-DEPENDENT PHOSPHOFRUCTOKINASE (LePFP), the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), and GIBBERELLIC ACID INSENSITIVE (LeGAI), were found to move from host (tomato (Solanum lycopersicum)) to dodder. LePFP mRNA was localized to the dodder parenchyma cells and to the phloem. LePFP transcripts were found in the growing dodder stem up to 30 cm from the tomato-dodder connection. These results suggest that mRNA molecules are transferred from host to parasite via symplastic connections between parenchyma cells, move towards the phloem, and are stable for a long distance in the parasite. This may allow developmental coordination between the parasite and its host.

Reversible Leaf Xylem Collapse: A Potential “Circuit Breaker” against Cavitation1[OPEN

PubMed Central

Zhang, Yong-Jiang; Rockwell, Fulton E.; Graham, Adam C.; Alexander, Teressa; Holbrook, N. Michele

2016-01-01

We report a novel form of xylem dysfunction in angiosperms: reversible collapse of the xylem conduits of the smallest vein orders that demarcate and intrusively irrigate the areoles of red oak (Quercus rubra) leaves. Cryo-scanning electron microscopy revealed gradual increases in collapse from approximately −2 MPa down to −3 MPa, saturating thereafter (to −4 MPa). Over this range, cavitation remained negligible in these veins. Imaging of rehydration experiments showed spatially variable recovery from collapse within 20 s and complete recovery after 2 min. More broadly, the patterns of deformation induced by desiccation in both mesophyll and xylem suggest that cell wall collapse is unlikely to depend solely on individual wall properties, as mechanical constraints imposed by neighbors appear to be important. From the perspective of equilibrium leaf water potentials, petioles, whose vessels extend into the major veins, showed a vulnerability to cavitation that overlapped in the water potential domain with both minor vein collapse and buckling (turgor loss) of the living cells. However, models of transpiration transients showed that minor vein collapse and mesophyll capacitance could effectively buffer major veins from cavitation over time scales relevant to the rectification of stomatal wrong-way responses. We suggest that, for angiosperms, whose subsidiary cells give up large volumes to allow large stomatal apertures at the cost of potentially large wrong-way responses, vein collapse could make an important contribution to these plants’ ability to transpire near the brink of cavitation-inducing water potentials. PMID:27733514

Water Filtration Using Plant Xylem

PubMed Central

Chambers, Valerie; Venkatesh, Varsha; Karnik, Rohit

2014-01-01

Effective point-of-use devices for providing safe drinking water are urgently needed to reduce the global burden of waterborne disease. Here we show that plant xylem from the sapwood of coniferous trees – a readily available, inexpensive, biodegradable, and disposable material – can remove bacteria from water by simple pressure-driven filtration. Approximately 3 cm3 of sapwood can filter water at the rate of several liters per day, sufficient to meet the clean drinking water needs of one person. The results demonstrate the potential of plant xylem to address the need for pathogen-free drinking water in developing countries and resource-limited settings. PMID:24587134

Branch xylem density variations across the Amazon Basin

NASA Astrophysics Data System (ADS)

Patiño, S.; Lloyd, J.; Paiva, R.; Baker, T. R.; Quesada, C. A.; Mercado, L. M.; Schmerler, J.; Schwarz, M.; Santos, A. J. B.; Aguilar, A.; Czimczik, C. I.; Gallo, J.; Horna, V.; Hoyos, E. J.; Jimenez, E. M.; Palomino, W.; Peacock, J.; Peña-Cruz, A.; Sarmiento, C.; Sota, A.; Turriago, J. D.; Villanueva, B.; Vitzthum, P.; Alvarez, E.; Arroyo, L.; Baraloto, C.; Bonal, D.; Chave, J.; Costa, A. C. L.; Herrera, R.; Higuchi, N.; Killeen, T.; Leal, E.; Luizão, F.; Meir, P.; Monteagudo, A.; Neil, D.; Núñez-Vargas, P.; Peñuela, M. C.; Pitman, N.; Priante Filho, N.; Prieto, A.; Panfil, S. N.; Rudas, A.; Salomão, R.; Silva, N.; Silveira, M.; Soares Dealmeida, S.; Torres-Lezama, A.; Vásquez-Martínez, R.; Vieira, I.; Malhi, Y.; Phillips, O. L.

2009-04-01

Xylem density is a physical property of wood that varies between individuals, species and environments. It reflects the physiological strategies of trees that lead to growth, survival and reproduction. Measurements of branch xylem density, ρx, were made for 1653 trees representing 598 species, sampled from 87 sites across the Amazon basin. Measured values ranged from 218 kg m-3 for a Cordia sagotii (Boraginaceae) from Mountagne de Tortue, French Guiana to 1130 kg m-3 for an Aiouea sp. (Lauraceae) from Caxiuana, Central Pará, Brazil. Analysis of variance showed significant differences in average ρx across regions and sampled plots as well as significant differences between families, genera and species. A partitioning of the total variance in the dataset showed that species identity (family, genera and species) accounted for 33% with environment (geographic location and plot) accounting for an additional 26%; the remaining "residual" variance accounted for 41% of the total variance. Variations in plot means, were, however, not only accountable by differences in species composition because xylem density of the most widely distributed species in our dataset varied systematically from plot to plot. Thus, as well as having a genetic component, branch xylem density is a plastic trait that, for any given species, varies according to where the tree is growing in a predictable manner. Within the analysed taxa, exceptions to this general rule seem to be pioneer species belonging for example to the Urticaceae whose branch xylem density is more constrained than most species sampled in this study. These patterns of variation of branch xylem density across Amazonia suggest a large functional diversity amongst Amazonian trees which is not well understood.

Sugar demand of ripening grape berries leads to recycling of surplus phloem water via the xylem.

PubMed

Keller, Markus; Zhang, Yun; Shrestha, Pradeep M; Biondi, Marco; Bondada, Bhaskar R

2015-06-01

We tested the common assumption that fleshy fruits become dependent on phloem water supply because xylem inflow declines at the onset of ripening. Using two distinct grape genotypes exposed to drought stress, we found that a sink-driven rise in phloem inflow at the beginning of ripening was sufficient to reverse drought-induced berry shrinkage. Rewatering accelerated berry growth and sugar accumulation concurrently with leaf photosynthetic recovery. Interrupting phloem flow through the peduncle prevented the increase in berry growth after rewatering, but interrupting xylem flow did not. Nevertheless, xylem flow in ripening berries, but not berry size, remained responsive to root or shoot pressurization. A mass balance analysis on ripening berries sampled in the field suggested that phloem water inflow may exceed growth and transpiration water demands. Collecting apoplastic sap from ripening berries showed that osmotic pressure increased at distinct rates in berry vacuoles and apoplast. Our results indicate that the decrease in xylem inflow at the onset of ripening may be a consequence of the sink-driven increase in phloem inflow. We propose a conceptual model in which surplus phloem water bypasses the fruit cells and partly evaporates from the berry surface and partly moves apoplastically to the xylem for outflow. © 2014 John Wiley & Sons Ltd.

Lateral Movement of Water and Sugar Across Xylem in Sugarcane Stalks

PubMed Central

Bull, T. A.; Gayler, K. R.; Glasziou, K. T.

1972-01-01

Laterally connected vascular bundles in the nodes of sugarcane (Saccharum species cv. Pindar) stalks allow a rapid redistribution of water across the stalk should the vascular continuity be partly disrupted. Tritiated water supplied to the roots exchanged rapidly between the xylem and storage tissue so that net movement up the stalk was slow. The half-time for exchange in a labeled stalk was about 4 hours so that the entire water content of a sugarcane stalk can turn over at least once in a single day. No rapid flux of sugar between xylem and phloem or xylem and storage tissue was detected. Functional xylem contained only low sugar concentrations: less than 0.3% w/v in the stalk and less than 0.02% w/v in the leaf. Previous reports of high sugar levels (9% w/v) in sugarcane stalk xylem reflect some degree of xylem blockage followed by a slow equilibration with free space sugars in the storage tissue. PMID:16658067

Seasonal variation in xylem pressure of walnut trees: root and stem pressures.

PubMed

Ewers, F W; Améglio, T; Cochard, H; Beaujard, F; Martignac, M; Vandame, M; Bodet, C; Cruiziat, P

2001-09-01

Measurements of air and soil temperatures and xylem pressure were made on 17-year-old orchard trees and on 5-year-old potted trees of walnut (Juglans regia L.). Cooling chambers were used to determine the relationships between temperature and sugar concentration ([glucose] + [fructose] + [sucrose], GFS) and seasonal changes in xylem pressure development. Pressure transducers were attached to twigs of intact plants, root stumps and excised shoots while the potted trees were subjected to various temperature regimes in autumn, winter and spring. Osmolarity and GFS of the xylem sap (apoplast) were measured before and after cooling or warming treatments. In autumn and spring, xylem pressures of up to 160 kPa were closely correlated with soil temperature but were not correlated with GFS in xylem sap. High root pressures were associated with uptake of mineral nutrients from soil, especially nitrate. In autumn and spring, xylem pressures were detected in root stumps as well as in intact plants, but not in excised stems. In contrast, in winter, 83% of the xylem sap osmolarity in both excised stems and intact plants could be accounted for by GFS, and both GFS and osmolarity were inversely proportional to temperature. Plants kept at 1.5 degrees C developed positive xylem pressures up to 35 kPa, xylem sap osmolarities up to 260 mosmol l(-1) and GFS concentrations up to 70 g l(-1). Autumn and spring xylem pressures, which appeared to be of root origin, were about 55% of the theoretical pressures predicted by osmolarity of the xylem sap. In contrast, winter pressures appeared to be of stem origin and were only 7% of the theoretical pressures, perhaps because of a lower stem water content during winter.

Tocochromanols in wood: a potential new tool for dendrometabolomics.

PubMed

Fleta-Soriano, Eva; Fernández-Marín, Beatriz; Olano, José Miguel; Míguez, Fátima; Molinero, Jon; Camarero, Jesús Julio; García-Plazaola, José Ignacio

2014-12-01

Tocochromanols are the most abundant lipid-soluble antioxidants in plants. Among them, α-tocopherol (α-Toc) shows a particularly high sensitivity to environmental stressors and its content is used as a stress biomarker even in non-photosynthetic tissues. Nevertheless, the presence of tocochromanols has not been described yet in the xylem of woody plants, even when their functions regarding cell membrane protection and the transport of photoassimilates may be crucial in this tissue and despite its potential utility in dendrometabolomics. Considering all these, we aimed to determine the presence and distribution of tocochromanols in the xylem of woody plants, to examine their responsiveness to high temperature and to evaluate their potential as environmental bioindicators. The analysis of 29 phyllogenetically diverse species showed that α-Toc is the most abundant and frequent tocochromanol in the xylem and is ubiquitously present in all the studied species, with a concentration ranging from 0.5 to 39.3 μg g(-1) of dry weight. α-Tocopherol appeared to be mainly located in the parenchyma rays and was found in both the sapwood and the heartwood, suggesting that it is present even in dead parenchyma cells. The levels of α-Toc in the xylem did not change in response to locally induced xylem heating, but responded positively to the 3-year moving average of annual precipitation. The present findings suggest that α-Toc may be linked to changes in climatic stress. This should enhance further research on the environmental controls of α-Toc variation in the xylem as a first step towards a deeper understanding of dendrometabolomics. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Growth of Verticillium longisporum in Xylem Sap of Brassica napus is Independent from Cultivar Resistance but Promoted by Plant Aging.

PubMed

Lopisso, Daniel Teshome; Knüfer, Jessica; Koopmann, Birger; von Tiedemann, Andreas

2017-09-01

late maturity stages of plants in the field. While falsifying the presence of antifungal activity in xylem sap of resistant cultivars, this study strengthens previous findings that indicated a significant role of physical cell wall bound resistance factors involved in quantitative, cultivar-related resistance of B. napus to V. longisporum.

The role of the parenchyma sheath and PCD during the development of oil cavities in Pterodon pubescens (Leguminosae-Papilionoideae).

PubMed

Rodrigues, Tatiane Maria; Santos, Daniela Carvalho Dos; Machado, Silvia Rodrigues

2011-07-01

Pterodon pubescens cavities are constituted by lumen and uniseriated epithelium surrounded by multiseriate parenchyma sheath. We studied the development of secretory cavities, including the role of parenchyma sheath, using light and transmission electron microscopy. A Tunel assay was performed to verify whether programmed cell death (PCD) occurs during the process. The lumen is formed by schizogeny and lysigeny occur in later developmental stages of the secretory cavities. Ultrastructurally, epithelial cells in later developmental stages become dark and with sinuous walls; the protoplast becomes retracted and the cytoplasm shows low organelle definition. Degenerated cells are released toward the lumen. Our results showed that PCD occurs during later developmental stages of cavities and plays a critical role in functioning of these glands. New cells originated from the parenchyma sheath differentiate into secretory cells and replace those degenerated ones. This fact associated to PCD guarantees epithelium renovation during the secretory cycle and the maintenance of secretory activity of cavities. Copyright © 2011 Académie des sciences. Published by Elsevier SAS. All rights reserved.

Structure-function constraints of tracheid-based xylem: a comparison of conifers and ferns.

PubMed

Pittermann, Jarmila; Limm, Emily; Rico, Christopher; Christman, Mairgareth A

2011-10-01

The ferns comprise one of the most ancient tracheophytic plant lineages, and occupy habitats ranging from tundra to deserts and the equatorial tropics. Like their nearest relatives the conifers, modern ferns possess tracheid-based xylem but the structure-function relationships of fern xylem are poorly understood. Here, we sampled the fronds (megaphylls) of 16 species across the fern phylogeny, and examined the relationships among hydraulic transport, drought-induced cavitation resistance, the xylem anatomy of the stipe, and the gas-exchange response of the pinnae. For comparison, the results are presented alongside a similar suite of conifer data. Fern xylem is as resistant to cavitation as conifer xylem, but exhibits none of the hydraulic or structural trade-offs associated with resistance to cavitation. On a conduit diameter basis, fern xylem can exhibit greater hydraulic efficiency than conifer and angiosperm xylem. In ferns, wide and long tracheids compensate in part for the lack of secondary xylem and allow ferns to exhibit transport rates on a par with those of conifers. We suspect that it is the arrangement of the primary xylem, in addition to the intrinsic traits of the conduits themselves, that may help explain the broad range of cavitation resistance in ferns. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

A particle-based model to simulate the micromechanics of single-plant parenchyma cells and aggregates

NASA Astrophysics Data System (ADS)

Van Liedekerke, P.; Ghysels, P.; Tijskens, E.; Samaey, G.; Smeedts, B.; Roose, D.; Ramon, H.

2010-06-01

This paper is concerned with addressing how plant tissue mechanics is related to the micromechanics of cells. To this end, we propose a mesh-free particle method to simulate the mechanics of both individual plant cells (parenchyma) and cell aggregates in response to external stresses. The model considers two important features in the plant cell: (1) the cell protoplasm, the interior liquid phase inducing hydrodynamic phenomena, and (2) the cell wall material, a viscoelastic solid material that contains the protoplasm. In this particle framework, the cell fluid is modeled by smoothed particle hydrodynamics (SPH), a mesh-free method typically used to address problems with gas and fluid dynamics. In the solid phase (cell wall) on the other hand, the particles are connected by pairwise interactions holding them together and preventing the fluid to penetrate the cell wall. The cell wall hydraulic conductivity (permeability) is built in as well through the SPH formulation. Although this model is also meant to be able to deal with dynamic and even violent situations (leading to cell wall rupture or cell-cell debonding), we have concentrated on quasi-static conditions. The results of single-cell compression simulations show that the conclusions found by analytical models and experiments can be reproduced at least qualitatively. Relaxation tests revealed that plant cells have short relaxation times (1 µs-10 µs) compared to mammalian cells. Simulations performed on cell aggregates indicated an influence of the cellular organization to the tissue response, as was also observed in experiments done on tissues with a similar structure.

Assessment of nutrient remobilization through structural changes of palisade and spongy parenchyma in oilseed rape leaves during senescence.

PubMed

Sorin, Clément; Musse, Maja; Mariette, François; Bouchereau, Alain; Leport, Laurent

2015-02-01

Differential palisade and spongy parenchyma structural changes in oilseed rape leaf were demonstrated. These dismantling processes were linked to early senescence events and associated to remobilization processes. During leaf senescence, an ordered cell dismantling process allows efficient nutrient remobilization. However, in Brassica napus plants, an important amount of nitrogen (N) in fallen leaves is associated with low N remobilization efficiency (NRE). The leaf is a complex organ mainly constituted of palisade and spongy parenchyma characterized by different structures and functions concerning water relations and carbon fixation. The aim of the present study was to demonstrate a specific structural evolution of these parenchyma throughout natural senescence in B. napus, probably linked to differential nutrient remobilization processes. The study was performed on 340 leaves from 32 plants during an 8-week development period under controlled growing conditions. Water distribution and status at the cellular level were investigated by low-field proton nuclear magnetic resonance (NMR), while light and electron microscopy were used to observe cell and plast structure. Physiological parameters were determined on all leaves studied and used as indicators of leaf development and remobilization progress. The results revealed a process of hydration and cell enlargement of leaf tissues associated with senescence. Wide variations were observed in the palisade parenchyma while spongy cells changed only very slightly. The major new functional information revealed was the link between the early senescence events and specific tissue dismantling processes.

Morphological changes in woody stem of Prunus jamasakura under simulated microgravity

NASA Technical Reports Server (NTRS)

Yoneyama, Emi; Ishimoto-Negishi, Yoko; Sano, Yuzou; Funada, Ryo; Yamada, Mitsuhiro; Nakamura, Teruko

2004-01-01

When the four-week-old woody stem of Prunus jamasakura was grown under simulated microgravity condition on a three-dimensional clinostat, it bent at growth, and width of its secondary xylem decreased due to the reduction of fiber cell numbers and a smaller microfibril angle in the secondary cell wall, as reported in our previous paper. Gravity induces the development of the secondary xylem that supports the stem upward against the action of gravity. In this study, morphological changes of the tissues and cells were microscopically observed. Disorder was found in the concentric structure of tissues that organize the stem. The radial arrangement of the cells was also disturbed in the secondary xylem, and in the secondary phloem secondary cell walls of the bast fiber cells were undeveloped. These findings suggest that differentiation and development of the secondary xylem and the bast fiber cells are strongly controlled by terrestrial gravity. These tissue and cells functions to support the stem under the action of gravity. Furthermore, clinorotation induced disorder in the straight joint of vessel elements and the lattice-like structure of radial parenchyma cells, which is responsible for water transportation and storage, respectively. Gravity is an essential factor for keeping the division and differentiation normal in woody stem.

[ULTRASTRUCTURE OF PARENCHYMA IN THE SYNCYTIAL DIGESTIVE SYSTEM IN TURBELLARIA Convoluta convoluta (Acoela].

PubMed

Gazizova, G R; Zabotin, Ya I; Golubev, A I

2015-01-01

The paper presents data on the ultrastructure of parenchyma that is involved in the digestion in turbellaria Convoluta convoluta (n = 15). Unusual connections between the nuclear envelope, endoplasmic reticulum and plasma membrane of parenchymal cells were found for the first time, which may indicate the origin of these cell structures. The double trophic role of zooxanthellae in the organism of Convoluta is described.

Causes and Effects of Changes in Xylem Functionality in Apple Fruit

PubMed Central

DRAŽETA, LAZAR; LANG, ALEXANDER; HALL, ALISTAIR J.; VOLZ, RICHARD K.; JAMESON, PAULA E.

2004-01-01

• Background and Aims The xylem in fruit of a number of species becomes dysfunctional as the fruit develops, resulting in a reduction of xylem inflow to the fruit. Such a reduction may have consequential effects on the mineral balance of the fruit. The aim of this study was to elucidate the dynamics and nature of xylem failure in developing apples (Malus domestica) showing differing susceptibilities to bitter pit, a calcium‐related disorder. • Methods Developmental changes in xylem functionality of the fruit were investigated in ‘Braeburn’ and ‘Granny Smith’ apples by using a dye infusion technique, to stain the vasculature along the path of dye movement. The vascular bundles were clearly visible in transverse section when fruit were sectioned equatorially. The intensity of staining of the vascular bundles in the fruit was recorded at regular intervals throughout the season. Tissue containing dysfunctional bundles was fixed and embedded in wax for subsequent sectioning and examination. • Key Results As the season progressed, an increasing proportion of vascular bundles failed to show any staining, with the most marked change occurring in the primary bundles, and in nearly all bundles with increasing distance from the stalk end of the fruit. Decreased conductance in the primary bundles of ‘Braeburn’ occurred earlier than in ‘Granny Smith’. Microscopy revealed that the xylem in vascular bundles of the fruit suffered substantial damage, indicating that the mode of dysfunction was via the physical disruption of the xylem caused by expansion of the flesh. • Conclusions Results support the view that the relative calcium deficiency of apple fruit is due to a progressive breakdown of xylem conductance caused by growth‐induced damage to the xylem strand in the bundle. The earlier onset of xylem dysfunction in the cultivar more susceptible to bitter pit suggests that the relative growth dynamics of the fruit may control the occurrence of calcium�

Extraction of immune and inflammatory cells from human lung parenchyma: evaluation of an enzymatic digestion procedure.

PubMed Central

Holt, P G; Robinson, B W; Reid, M; Kees, U R; Warton, A; Dawson, V H; Rose, A; Schon-Hegrad, M; Papadimitriou, J M

1986-01-01

The inflammatory and immune cell populations of the human lung parenchyma have not been characterized in detail. This report describes a novel and efficient procedure for their extraction. Histologically normal human lung tissue samples from pneumonectomy specimens were sliced to 0.5 mm, and digested in collagenase/DNAse. Viable mononuclear cell yields ranged from 15-48 X 10(6)/g, and were markedly in excess of reported methods employing mechanical tissue disruption, which normally yield populations containing almost exclusively macrophages. The lung digest population was examined by flow cytometry using monoclonal antibodies against cell surface receptors, and found to comprise up to 40% T lymphocytes, 10% B lymphocytes and 30% macrophages, contaminated by less than 1% peripheral blood cells. Based upon these figures, the recoverable lung parenchymal lymphoid cell pool appears considerably larger than previously recognized, being of the same order as the peripheral blood pool. Initial functional studies suggest that such cellular activities as antigen-specific T cell proliferation, antigen-presentation, interleukin 1 production and natural killer cell activity survive the extraction process, and controlled enzymatic digestion experiments with peripheral blood cells indicate that the degree of enzyme-mediated damage to these functions and to cell-surface structures, was minimal. The extraction method thus appears suitable for studying the types and functions of human parenchymal lung cells in health and disease. Images Fig. 2 p195-a PMID:3026698

Metal Complexation in Xylem Fluid 1

PubMed Central

White, Michael C.; Decker, A. Morris; Chaney, Rufus L.

1981-01-01

Xylem fluid was analyzed for numerous solutes to characterize chemically the sap as a medium for forming and transporting metal complexes. The stem exudate was collected hourly for 8 hours from topped 31-day-old soybean (Glycine max L. Merr.) and 46-day-old tomato (Lycopersicon esculentum Mill.) plants grown in normal (0.5 micromolar) and Za-phytotoxic nutrient solutions. Soybean plants were grown in the normal and high-Zn solutions for 24 days; tomato plants were grown for 32 days. The exudate was analyzed for seven organic acids, 22 amino acids, eight inorganic solutes, apparent ionic strength, and pH. Significant changes in many solutes occurred over the 8-hour sampling period. These fluctuations depended on plant species, individual solute, and Zn treatment, and demonstrated that extrapolation of xylem-fluid analyses to whole-plant xylem sap is valid only for sap samples collected shortly after topping a plant. Exudate pH decreased over the 8-hour period for both species; exudate ionic strength increased for tomato and decreased for soybean. At the normal-Zn treatment (0 to 1 hour), the highest acid micromolar concentrations in soybean exudate were: asparagine, 2,583; citric, 1,706; malic, 890; and malonic, 264. Under the same conditions, the highest acid micromolar concentrations in tomato exudate were: maleic, 1,206; malic, 628; glutamine, 522; citric, 301; and asparagine, 242. Cysteine and methionine were above detection limits only in soybean exudate. Zinc phytotoxicity caused significant changes in many solutes. The analyses reported here provide a comprehensive data base for further studies on metal-complex equilibria in xylem fluid. PMID:16661664

What are the driving forces for water lifting in the xylem conduit?

PubMed

Zimmermann, Ulrich; Schneider, Heike; Wegner, Lars H; Wagner, Hans-Jürgen; Szimtenings, Michael; Haase, Axel; Bentrup, Friedrich-Wilhelm

2002-03-01

After Renner had shown convincingly in 1925 that the transpirational water loss generates tensions larger than 0.1 MPa (i.e. negative pressures) in the xylem of cut leafy twigs the Cohesion Theory proposed by Böhm, Askenasy, Dixon and Joly at the end of the 19th century was immediately accepted by plant physiologists. Introduction of the pressure chamber technique by Scholander et al. in 1965 enforced the general belief that tension is the only driving force for water lifting although substantial criticism regarding the technique and/or the Cohesion Theory was published by several authors. As typical for scientific disciplines, the advent of minimal- and non-invasive techniques in the last decade as well as the development of a new, reliable method for xylem sap sampling have challenged this view. Today, xylem pressure gradients, potentials, ion concentrations and volume flows as well as cell turgor pressure gradients can be monitored online in intact transpiring higher plants, and within a given physiological context by using the pressure probe technique and high-resolution NMR imaging techniques, respectively. Application of the pressure probe technique to transpiring plants has shown that negative absolute pressures (down to - 0.6 MPa) and pressure gradients can exist temporarily in the xylem conduit, but that the magnitude and (occasionally) direction of gradients contrasts frequently the belief that tension is the only driving force. This seems to be particularly the case for plants faced with problems of height, drought, freezing and salinity as well as with cavitation of the tensile water. Reviewing the current data base shows that other forces come into operation when exclusively tension fails to lift water against gravity due to environmental conditions. Possible candidates are longitudinal cellular and xylem osmotic pressure gradients, axial potential gradients in the vessels as well as gel- and gas bubble-supported interfacial gradients. The multiforce

Tryptophan-dependent auxin biosynthesis is required for HD-ZIP III-mediated xylem patterning.

PubMed

Ursache, Robertas; Miyashima, Shunsuke; Chen, Qingguo; Vatén, Anne; Nakajima, Keiji; Carlsbecker, Annelie; Zhao, Yunde; Helariutta, Ykä; Dettmer, Jan

2014-03-01

The development and growth of higher plants is highly dependent on the conduction of water and minerals throughout the plant by xylem vessels. In Arabidopsis roots the xylem is organized as an axis of cell files with two distinct cell fates: the central metaxylem and the peripheral protoxylem. During vascular development, high and low expression levels of the class III HD-ZIP transcription factors promote metaxylem and protoxylem identities, respectively. Protoxylem specification is determined by both mobile, ground tissue-emanating miRNA165/6 species, which downregulate, and auxin concentrated by polar transport, which promotes HD-ZIP III expression. However, the factors promoting high HD-ZIP III expression for metaxylem identity have remained elusive. We show here that auxin biosynthesis promotes HD-ZIP III expression and metaxylem specification. Several auxin biosynthesis genes are expressed in the outer layers surrounding the vascular tissue in Arabidopsis root and downregulation of HD-ZIP III expression accompanied by specific defects in metaxylem development is seen in auxin biosynthesis mutants, such as trp2-12, wei8 tar2 or a quintuple yucca mutant, and in plants treated with L-kynurenine, a pharmacological inhibitor of auxin biosynthesis. Some of the patterning defects can be suppressed by synthetically elevated HD-ZIP III expression. Taken together, our results indicate that polar auxin transport, which was earlier shown to be required for protoxylem formation, is not sufficient to establish a proper xylem axis but that root-based auxin biosynthesis is additionally required.

Do xylem fibers affect vessel cavitation resistance?

PubMed

Jacobsen, Anna L; Ewers, Frank W; Pratt, R Brandon; Paddock, William A; Davis, Stephen D

2005-09-01

Possible mechanical and hydraulic costs to increased cavitation resistance were examined among six co-occurring species of chaparral shrubs in southern California. We measured cavitation resistance (xylem pressure at 50% loss of hydraulic conductivity), seasonal low pressure potential (P(min)), xylem conductive efficiency (specific conductivity), mechanical strength of stems (modulus of elasticity and modulus of rupture), and xylem density. At the cellular level, we measured vessel and fiber wall thickness and lumen diameter, transverse fiber wall and total lumen area, and estimated vessel implosion resistance using (t/b)(h)(2), where t is the thickness of adjoining vessel walls and b is the vessel lumen diameter. Increased cavitation resistance was correlated with increased mechanical strength (r(2) = 0.74 and 0.76 for modulus of elasticity and modulus of rupture, respectively), xylem density (r(2) = 0.88), and P(min) (r(2) = 0.96). In contrast, cavitation resistance and P(min) were not correlated with decreased specific conductivity, suggesting no tradeoff between these traits. At the cellular level, increased cavitation resistance was correlated with increased (t/b)(h)(2) (r(2) = 0.95), increased transverse fiber wall area (r(2) = 0.89), and decreased fiber lumen area (r(2) = 0.76). To our knowledge, the correlation between cavitation resistance and fiber wall area has not been shown previously and suggests a mechanical role for fibers in cavitation resistance. Fiber efficacy in prevention of vessel implosion, defined as inward bending or collapse of vessels, is discussed.

A 6-Year-Long Manipulation with Soil Warming and Canopy Nitrogen Additions does not Affect Xylem Phenology and Cell Production of Mature Black Spruce

PubMed Central

Dao, Madjelia C. E.; Rossi, Sergio; Walsh, Denis; Morin, Hubert; Houle, Daniel

2015-01-01

The predicted climate warming and increased atmospheric inorganic nitrogen deposition are expected to have dramatic impacts on plant growth. However, the extent of these effects and their interactions remains unclear for boreal forest trees. The aim of this experiment was to investigate the effects of increased soil temperature and nitrogen (N) depositions on stem intra-annual growth of two mature stands of black spruce [Picea mariana (Mill.) BSP] in Québec, QC, Canada. During 2008–2013, the soil around mature trees was warmed up by 4°C with heating cables during the growing season and precipitations containing three times the current inorganic N concentration were added by frequent canopy applications. Xylem phenology and cell production were monitored weekly from April to October. The 6-year-long experiment performed in two sites at different altitude showed no substantial effect of warming and N-depositions on xylem phenological phases of cell enlargement, wall thickening and lignification. Cell production, in terms of number of tracheids along the radius, also did not differ significantly and followed the same patterns in control and treated trees. These findings allowed the hypothesis of a medium-term effect of soil warming and N depositions on the growth of mature black spruce to be rejected. PMID:26617610

Aluminium localization in root tips of the aluminium-accumulating plant species buckwheat (Fagopyrum esculentum Moench)

PubMed Central

Klug, Benjamin; Specht, André; Horst, Walter J.

2011-01-01

Aluminium (Al) uptake and transport in the root tip of buckwheat is not yet completely understood. For localization of Al in root tips, fluorescent dyes and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were compared. The staining of Al with morin is an appropriate means to study qualitatively the radial distribution along the root tip axis of Al which is complexed by oxalate and citrate in buckwheat roots. The results compare well with the distribution of total Al determined by LA-ICP-MS which could be reliably calibrated to compare with Al contents by conventional total Al determination using graphite furnace atomic absorption spectrometry. The Al localization in root cross-sections along the root tip showed that in buckwheat Al is highly mobile in the radial direction. The root apex predominantly accumulated Al in the cortex. The subapical root section showed a homogenous Al distribution across the whole section. In the following root section Al was located particularly in the pericycle and the xylem parenchyma cells. With further increasing distance from the root apex Al could be detected only in individual xylem vessels. The results support the view that the 10 mm apical root tip is the main site of Al uptake into the symplast of the cortex, while the subapical 10–20 mm zone is the main site of xylem loading through the pericycle and xylem parenchyma cells. Progress in the better molecular understanding of Al transport in buckwheat will depend on the consideration of the tissue specificity of Al transport and complexation. PMID:21831842

Pharmacognostical and Phytochemical Studies of Helleborus niger L Root.

PubMed

Kumar, V Kishor; Lalitha, K G

2017-01-01

Helleborus niger L (Ranunculaceae) is used Ayurvedic and Unani systems and other herbal medicine systems. The roots of H. niger have a good medicinal value. To conduct a pharmacognostical and phytochemical study of H. niger . The pharmacognostical studies on roots including parameters such as taxonomical, macroscopic, microscopic characters, physico-chemical, ultra-violet analysis and phytochemical studies are established. Macroscopically, the roots are brownish-black in colour, cylindrical in shape, feeble odour, slightly acrid taste with irregularly branched. Microscopically the root showed the presence of epidermis, air-chambers, fissure periderm, periderm, inner cortex, pith, phloem, xylem, vessels and xylem vessels. Microscopic examination of the powder showed the presence of parenchyma cells, parenchyma mass, periderm, cell inclusion, laticifer, lateral wall pith, perforation, xylem bundle and xylem elements. Ultra-violet and ordinary light analyses with different reagents were conducted to identify the drug in powder form. Physico-chemical evaluation established, Ash values - Total, acid insoluble, water soluble and sulphated ash values were 7.3%, 4.1%, 3.7% and 5.2%, respectively. Extractive values - Alcohol soluble, water soluble and ether soluble extractive values were 22.8%, 7.4% and 5.6%, respectively. Loss on drying was 3.3%. Preliminary phytochemical screening showed the presence of carbohydrate, glycoside, saponins, flavonoid, phytosterols, tannins and phenolic compounds. The results of the study can serve as a valuable resource of pharmacognostic and phytochemical information. This will serve as appropriate, standards for discovery of this plant material in future investigations and applications and also contribute towards establishing pharmacopoeial standards.

NRT1.5/NPF7.3 Functions as a Proton-Coupled H+/K+ Antiporter for K+ Loading into the Xylem in Arabidopsis.

PubMed

Li, Hong; Yu, Miao; Du, Xin-Qiao; Wang, Zhi-Fang; Wu, Wei-Hua; Quintero, Francisco J; Jin, Xue-Hua; Li, Hao-Dong; Wang, Yi

2017-08-01

Potassium and nitrogen are essential macronutrients for plant growth and have a positive impact on crop yield. Previous studies have indicated that the absorption and translocation of K + and NO 3 - are correlated with each other in plants; however, the molecular mechanism that coordinates K + and NO 3 - transport remains unknown. In this study, using a forward genetic approach, we isolated a low-K + -sensitive Arabidopsis thaliana mutant, lks2 , that showed a leaf chlorosis phenotype under low-K + conditions. LKS2 encodes the transporter NRT1.5/NPF7.3, a member of the NRT1/PTR (Nitrate Transporter 1/Peptide Transporter) family. The lks2 / nrt1.5 mutants exhibit a remarkable defect in both K + and NO 3 - translocation from root to shoot, especially under low-K + conditions. This study demonstrates that LKS2 (NRT1.5) functions as a proton-coupled H + /K + antiporter. Proton gradient can promote NRT1.5-mediated K + release out of root parenchyma cells and facilitate K + loading into the xylem. This study reveals that NRT1.5 plays a crucial role in K + translocation from root to shoot and is also involved in the coordination of K + /NO 3 - distribution in plants. © 2017 American Society of Plant Biologists. All rights reserved.

Glassy-winged sharpshooter feeding does not cause air embolisms in xylem of well-watered plants.

USDA-ARS?s Scientific Manuscript database

Plant xylem vessels are under negative hydrostatic pressure (tension) as evapotranspiration of water from the leaf surface pulls the column of water in xylem upwards. When xylem fluid flux is under extreme tension, any puncture or breakage of the xylem vessel wall can cause formation of air embolis...

Tyloses and Phenolic Deposits in Xylem Vessels Impede Water Transport in Low-Lignin Transgenic Poplars: A Study by Cryo-Fluorescence Microscopy1[W][OA

PubMed Central

Kitin, Peter; Voelker, Steven L.; Meinzer, Frederick C.; Beeckman, Hans; Strauss, Steven H.; Lachenbruch, Barbara

2010-01-01

Of 14 transgenic poplar genotypes (Populus tremula × Populus alba) with antisense 4-coumarate:coenzyme A ligase that were grown in the field for 2 years, five that had substantial lignin reductions also had greatly reduced xylem-specific conductivity compared with that of control trees and those transgenic events with small reductions in lignin. For the two events with the lowest xylem lignin contents (greater than 40% reduction), we used light microscopy methods and acid fuchsin dye ascent studies to clarify what caused their reduced transport efficiency. A novel protocol involving dye stabilization and cryo-fluorescence microscopy enabled us to visualize the dye at the cellular level and to identify water-conducting pathways in the xylem. Cryo-fixed branch segments were planed in the frozen state on a sliding cryo-microtome and observed with an epifluorescence microscope equipped with a cryo-stage. We could then distinguish clearly between phenolic-occluded vessels, conductive (stain-filled) vessels, and nonconductive (water- or gas-filled) vessels. Low-lignin trees contained areas of nonconductive, brown xylem with patches of collapsed cells and patches of noncollapsed cells filled with phenolics. In contrast, phenolics and nonconductive vessels were rarely observed in normal colored wood of the low-lignin events. The results of cryo-fluorescence light microscopy were supported by observations with a confocal microscope after freeze drying of cryo-planed samples. Moreover, after extraction of the phenolics, confocal microscopy revealed that many of the vessels in the nonconductive xylem were blocked with tyloses. We conclude that reduced transport efficiency of the transgenic low-lignin xylem was largely caused by blockages from tyloses and phenolic deposits within vessels rather than by xylem collapse. PMID:20639405

Xylem Surfactants Introduce a New Element to the Cohesion-Tension Theory.

PubMed

Schenk, H Jochen; Espino, Susana; Romo, David M; Nima, Neda; Do, Aissa Y T; Michaud, Joseph M; Papahadjopoulos-Sternberg, Brigitte; Yang, Jinlong; Zuo, Yi Y; Steppe, Kathy; Jansen, Steven

2017-02-01

Vascular plants transport water under negative pressure without constantly creating gas bubbles that would disable their hydraulic systems. Attempts to replicate this feat in artificial systems almost invariably result in bubble formation, except under highly controlled conditions with pure water and only hydrophilic surfaces present. In theory, conditions in the xylem should favor bubble nucleation even more: there are millions of conduits with at least some hydrophobic surfaces, and xylem sap is saturated or sometimes supersaturated with atmospheric gas and may contain surface-active molecules that can lower surface tension. So how do plants transport water under negative pressure? Here, we show that angiosperm xylem contains abundant hydrophobic surfaces as well as insoluble lipid surfactants, including phospholipids, and proteins, a composition similar to pulmonary surfactants. Lipid surfactants were found in xylem sap and as nanoparticles under transmission electron microscopy in pores of intervessel pit membranes and deposited on vessel wall surfaces. Nanoparticles observed in xylem sap via nanoparticle-tracking analysis included surfactant-coated nanobubbles when examined by freeze-fracture electron microscopy. Based on their fracture behavior, this technique is able to distinguish between dense-core particles, liquid-filled, bilayer-coated vesicles/liposomes, and gas-filled bubbles. Xylem surfactants showed strong surface activity that reduces surface tension to low values when concentrated as they are in pit membrane pores. We hypothesize that xylem surfactants support water transport under negative pressure as explained by the cohesion-tension theory by coating hydrophobic surfaces and nanobubbles, thereby keeping the latter below the critical size at which bubbles would expand to form embolisms. © 2017 American Society of Plant Biologists. All Rights Reserved.

Protein and metabolite composition of xylem sap from field-grown soybeans (Glycine max).

PubMed

Krishnan, Hari B; Natarajan, Savithiry S; Bennett, John O; Sicher, Richard C

2011-05-01

The xylem, in addition to transporting water, nutrients and metabolites, is also involved in long-distance signaling in response to pathogens, symbionts and environmental stresses. Xylem sap has been shown to contain a number of proteins including metabolic enzymes, stress-related proteins, signal transduction proteins and putative transcription factors. Previous studies on xylem sap have mostly utilized plants grown in controlled environmental chambers. However, plants in the field are subjected to high light and to environmental stress that is not normally found in growth chambers. In this study, we have examined the protein and metabolite composition of xylem sap from field-grown cultivated soybean plants. One-dimensional gel electrophoresis of xylem sap from determinate, indeterminate, nodulating and non-nodulating soybean cultivars revealed similar protein profiles consisting of about 8-10 prominent polypeptides. Two-dimensional gel electrophoresis of soybean xylem sap resulted in the visualization of about 60 distinct protein spots. A total of 38 protein spots were identified using MALDI-TOF MS and LC-MS/MS. The most abundant proteins present in the xylem sap were identified as 31 and 28 kDa vegetative storage proteins. In addition, several proteins that are conserved among different plant species were also identified. Diurnal changes in the metabolite profile of xylem sap collected during a 24-h cycle revealed that asparagine and aspartate were the two predominant amino acids irrespective of the time collected. Pinitol (D-3-O-methyl-chiro-inositol) was the most abundant carbohydrate present. The possible roles of xylem sap proteins and metabolites as nutrient reserves for sink tissue and as an indicator of biotic stress are also discussed.

Chemical and anatomical changes in Liquidambar styraciflua L.xylem after long term exposure to elevated CO

Treesearch

Keonhee Kim; Nicole Labbé; Jeffrey M. Warren; Thomas Elder; Timothy G. Rials

2015-01-01

The anatomical and chemical characteristics of sweetgum were studied after 11 years of elevated CO₂(544 ppm, ambient at 391 ppm) exposure. Anatomically, branch xylem cells were larger for elevated CO2 trees, and the cell wall thickness was thinner. Chemically, elevated CO₂ exposure did not...

Scaling of xylem and phloem transport capacity and resource usage with tree size

PubMed Central

Hölttä, Teemu; Kurppa, Miika; Nikinmaa, Eero

2013-01-01

Xylem and phloem need to maintain steady transport rates of water and carbohydrates to match the exchange rates of these compounds at the leaves. A major proportion of the carbon and nitrogen assimilated by a tree is allocated to the construction and maintenance of the xylem and phloem long distance transport tissues. This proportion can be expected to increase with increasing tree size due to the growing transport distances between the assimilating tissues, i.e., leaves and fine roots, at the expense of their growth. We formulated whole tree level scaling relations to estimate how xylem and phloem volume, nitrogen content and hydraulic conductance scale with tree size, and how these properties are distributed along a tree height. Xylem and phloem thicknesses and nitrogen contents were measured within varying positions in four tree species from Southern Finland. Phloem volume, nitrogen amount and hydraulic conductance were found to be concentrated toward the branch and stem apices, in contrast to the xylem where these properties were more concentrated toward the tree base. All of the species under study demonstrated very similar trends. Total nitrogen amount allocated to xylem and phloem was predicted to be comparable to the nitrogen amount allocated to the leaves in small and medium size trees, and to increase significantly above the nitrogen content of the leaves in larger trees. Total volume, hydraulic conductance and nitrogen content of the xylem were predicted to increase faster than that of the phloem with increasing tree height in small trees (<~10 m in height). In larger trees, xylem sapwood turnover to heartwood, if present, would maintain phloem conductance at the same level with xylem conductance with further increases in tree height. Further simulations with a previously published xylem-phloem transport model demonstrated that the Münch pressure flow hypothesis could explain phloem transport with increasing tree height even for the tallest trees. PMID

Cell-to-cell signaling in Xylella fastidiosa suppresses movement and xylem vessel colonization in grape.

PubMed

Chatterjee, Subhadeep; Newman, Karyn L; Lindow, Steven E

2008-10-01

Cell-to-cell signaling mediated by a fatty acid diffusible signaling factor (DSF) is central to the regulation of the virulence of Xylella fastidiosa. DSF production by X. fastidiosa is dependent on rpfF and, although required for insect colonization, appears to reduce its virulence to grape. To understand what aspects of colonization of grape are controlled by DSF in X. fastidiosa and, thus, those factors that contribute to virulence, we assessed the colonization of grape by a green fluorescent protein-marked rpfF-deficient mutant. The rpfF-deficient mutant was detected at a greater distance from the point of inoculation than the wild-type strain at a given sampling time, and also attained a population size that was up to 100-fold larger than that of the wild-type strain at a given distance from the point of inoculation. Confocal laser-scanning microscopy revealed that approximately 10-fold more vessels in petioles of symptomatic leaves harbored at least some cells of either the wild type or rpfF mutant when compared with asymptomatic leaves and, thus, that disease symptoms were associated with the extent of vessel colonization. Importantly, the rpfF mutant colonized approximately threefold more vessels than the wild-type strain. Although a wide range of colony sizes were observed in vessels colonized by both the wild type and rpfF mutant, the proportion of colonized vessels harboring large numbers of cells was significantly higher in plants inoculated with the rpfF mutant than with the wild-type strain. These studies indicated that the hypervirulence phenotype of the rpfF mutant is due to both a more extensive spread of the pathogen to xylem vessels and unrestrained multiplication within vessels leading to blockage. These results suggest that movement and multiplication of X. fastidiosa in plants are linked, perhaps because cell wall degradation products are a major source of nutrients. Thus, DSF-mediated cell-to-cell signaling, which restricts movement and

Transport and coordination in the coupled soil-root-xylem-phloem leaf system

NASA Astrophysics Data System (ADS)

Huang, C. W.; Katul, G. G.; Pockman, W.; Litvak, M. E.; Domec, J. C.; Palmroth, S.

2016-12-01

In response to varying environmental conditions, stomatal pores act as biological valves that dynamically adjust their size thereby determining the rate of CO2 assimilation and water loss (i.e., transpiration) to the dry atmosphere. Although the significance of this biotic control on gas exchange is rarely disputed, representing parsimoniously all the underlying mechanisms responsible for stomatal kinetics remain a subject of some debate. It has been conjectured that stomatal control in seed plants (i.e., angiosperm and gymnosperm) represents a compromise between biochemical demand for CO2 and prevention of excessive water loss. This view has been amended at the whole-plant level, where xylem hydraulics and sucrose transport efficiency in phloem appear to impose additional constraints on gas exchange. If such additional constraints impact stomatal opening and closure, then seed plants may have evolved coordinated photosynthetic-hydraulic-sugar transporting machinery that confers some competitive advantages in fluctuating environmental conditions. Thus, a stomatal optimization model that explicitly considers xylem hydraulics and maximum sucrose transport is developed to explore this coordination in the leaf-xylem-phloem system. The model is then applied to progressive drought conditions. The main findings from the model calculations are that (1) the predicted stomatal conductance from the conventional stomatal optimization theory at the leaf and the newly proposed models converge, suggesting a tight coordination in the leaf-xylem-phloem system; (2) stomatal control is mainly limited by the water supply function of the soil-xylem hydraulic system especially when the water flux through the transpiration stream is significantly larger than water exchange between xylem and phloem; (3) thus, xylem limitation imposed on the supply function can be used to differentiate species with different water use strategy across the spectrum of isohydric to anisohydric behavior

Liver Parenchyma Perforation following Endoscopic Retrograde Cholangiopancreatography.

PubMed

Kayashima, Hiroto; Ikegami, Toru; Kasagi, Yuta; Hidaka, Gen; Yamazaki, Koji; Sadanaga, Noriaki; Itoh, Hiroyuki; Emi, Yasunori; Matsuura, Hiroshi; Okadome, Kenichiro

2011-05-01

Although endoscopic retrograde cholangiopancreatography (ERCP) is an effective modality for the diagnosis and treatment of biliary and pancreatic diseases, it is still related with several severe complications. We report on the case of a female patient who developed liver parenchyma perforation following ERCP. She underwent ERCP with sphincterotomy and extraction of a common bile duct stone. Shortly after ERCP, abdominal distension was identified. Abdominal computed tomography revealed intraabdominal air leakage and leakage of contrast dye penetrating the liver parenchyma into the space around the spleen. Since periampullary perforation related to sphincterotomy could not be denied, she was referred for immediate surgery. Obvious perforation could not be found at surgery. Cholecystectomy, insertion of a T tube into the common bile duct, placement of a duodenostomy tube and drainage of the retroperitoneum were performed. She did well postoperatively and was discharged home on postoperative day 28. In conclusion, as it is well recognized that perforation is one of the most serious complication related to ERCP, liver parenchyma perforation should be suspected as a cause.

[Developmental anatomy of anomalous structure and investigation of medicinal parts Sophora flavescens].

PubMed

Wang, Jun; Xie, Xiaomei; Peng, Huasheng

2012-06-01

To elucidate the composition structure of "annual rings" and the formation process of anomalous structures in Sophora flavescens, and further discuss the medicinal parts of S. flavescens. Based on investigation on S. flavescens in its producing areas, the morphology of root systems was observed, and the developmental anatomy of roots was researched. Creeping underground rhizomes of S. flavescen existed in some parts of the north place, there were many differences in appearance characters and microscopic features between these roots and rhizomes. Parenchyma cells in secondary xylem regained meristematic ability, became into anomalous cambia, and then developed into anomalous structures. "Annual rings" in transverse section of S. flavescens were not actually growth rings, they were made up of anomalous parenchyma girdle in secondary xylem and normal secondary structure. Roots are the medicinal parts of S. flavescens. This paper suggests that "annual rings" in the decoction pieces of S. flavescens should be called "annular structure".

A broad survey of hydraulic and mechanical safety in the xylem of conifers

Treesearch

Pauline S. Bouche; Maximilien Larter; Jean-Christophe Domec; Regis Burlett; Peter Gasson; Steven Jansen; Sylvain Delzon

2014-01-01

Drought-induced forest dieback has been widely reported over the last decades, and the evidence for a direct causal link between survival and hydraulic failure (xylem cavitation) is now well known. Because vulnerability to cavitation is intimately linked to the anatomy of the xylem, the main objective of this study was to better understand the xylem anatomical...

Recovery performance in xylem hydraulic conductivity is correlated with cavitation resistance for temperate deciduous tree species.

PubMed

Ogasa, Mayumi; Miki, Naoko H; Murakami, Yuki; Yoshikawa, Ken

2013-04-01

Woody species hydraulically vulnerable to xylem cavitation may experience daily xylem embolism. How such species cope with the possibility of accumulated embolism is unclear. In this study, we examined seven temperate woody species to assess the hypothesis that low cavitation resistance (high vulnerability to cavitation) is compensated by high recovery performance via vessel refilling. We also evaluated leaf functional and xylem structural traits. The xylem recovery index (XRI), defined as the ratio of xylem hydraulic conductivity in plants rewatered after soil drought to that in plants under moist conditions, varied among species. The xylem water potential causing 50% loss of hydraulic conductivity (Ψ50) varied among the species studied, whereas only a slight difference was detected with respect to midday xylem water potential (Ψmin), indicating smaller hydraulic safety margins (Ψmin - Ψ50) for species more vulnerable to cavitation. Cavitation resistance (|Ψ50|) was negatively correlated with XRI across species, with cavitation-vulnerable species showing a higher performance in xylem recovery. Wood density was positively correlated with cavitation resistance and was negatively correlated with XRI. These novel results reveal that coordination exists between cavitation resistance and xylem recovery performance, in association with wood functional traits such as denser wood for cavitation-resistant xylem and less-dense but water-storable wood for refillable xylem. These findings provide insights into long-term maintenance of water transport in tree species growing under variable environmental conditions.

Micromechanical model of lung parenchyma hyperelasticity

NASA Astrophysics Data System (ADS)

Concha, Felipe; Sarabia-Vallejos, Mauricio; Hurtado, Daniel E.

2018-03-01

Mechanics plays a key role in respiratory physiology, as lung tissue cyclically deforms to bring air in and out the lung, a life-long process necessary for respiration. The study of regional mechanisms of deformation in lung parenchyma has received great attention to date due to its clinical relevance, as local overstretching and stress concentration in lung tissue is currently associated to pathological conditions such as lung injury during mechanical ventilation therapy. This mechanical approach to lung physiology has motivated the development of constitutive models to better understand the relation between stress and deformation in the lung. While material models proposed to date have been key in the development of whole-lung simulations, either they do not directly relate microstructural properties of alveolar tissue with coarse-scale behavior, or they require a high computational effort when based on real alveolar geometries. Furthermore, most models proposed to date have not been thoroughly validated for anisotropic deformation states, which are commonly found in normal lungs in-vivo. In this work, we develop a novel micromechanical model of lung parenchyma hyperelasticity using the framework of finite-deformation homogenization. To this end, we consider a tetrakaidecahedron unit cell with incompressible Neo-Hookean structural elements that account for the alveolar wall tissue responsible for the elastic response, and derive expressions for its effective coarse-scale behavior that directly depend on the alveolar wall elasticity, reference porosity, and two other geometrical coefficients. To validate the proposed model, we simulate the non-linear elastic response of twelve representative volume elements (RVEs) of lung parenchyma with micrometric dimensions, whose geometry is obtained from micrometric computed-tomography reconstructions of murine lungs. We show that the proposed micromechanical model accurately captures the RVEs response not only for isotropic

Xylem Development and Cell Wall Changes of Soybean Seedlings Grown in Space

PubMed Central

de Micco, Veronica; Aronne, Giovanna; Joseleau, Jean-Paul; Ruel, Katia

2008-01-01

Background and Aims Plants growing in altered gravity conditions encounter changes in vascular development and cell wall deposition. The aim of this study was to investigate xylem anatomy and arrangement of cellulose microfibrils in vessel walls of different organs of soybean seedlings grown in Space. Methods Seeds germinated and seedlings grew for 5 d in Space during the Foton-M2 mission. The environmental conditions, other than gravity, of the ground control repeated those experienced in orbit. The seedlings developed in space were compared with those of the control test on the basis of numerous anatomical and ultrastructural parameters such as number of veins, size and shape of vessel lumens, thickness of cell walls and deposition of cellulose microfibrils. Key Results Observations made with light, fluorescence and transmission electron microscopy, together with the quantification of the structural features through digital image analysis, showed that the alterations due to microgravity do not occur at the same level in the various organs of soybean seedlings. The modifications induced by microgravity or by the indirect effect of space-flight conditions, became conspicuous only in developing vessels at the ultrastructural level. The results suggested that the orientation of microfibrils and their assembly in developing vessels are perturbed by microgravity at the beginning of wall deposition, while they are still able to orient and arrange in thicker and ordered structures at later stages of secondary wall deposition. Conclusions The process of proper cell-wall building, although not prevented, is perturbed in Space at the early stage of development. This would explain the almost unaltered anatomy of mature structures, accompanied by a slower growth observed in seedlings grown in Space than on Earth. PMID:18252765

Xylem development and cell wall changes of soybean seedlings grown in space.

PubMed

de Micco, Veronica; Aronne, Giovanna; Joseleau, Jean-Paul; Ruel, Katia

2008-04-01

Plants growing in altered gravity conditions encounter changes in vascular development and cell wall deposition. The aim of this study was to investigate xylem anatomy and arrangement of cellulose microfibrils in vessel walls of different organs of soybean seedlings grown in Space. Seeds germinated and seedlings grew for 5 d in Space during the Foton-M2 mission. The environmental conditions, other than gravity, of the ground control repeated those experienced in orbit. The seedlings developed in space were compared with those of the control test on the basis of numerous anatomical and ultrastructural parameters such as number of veins, size and shape of vessel lumens, thickness of cell walls and deposition of cellulose microfibrils. Observations made with light, fluorescence and transmission electron microscopy, together with the quantification of the structural features through digital image analysis, showed that the alterations due to microgravity do not occur at the same level in the various organs of soybean seedlings. The modifications induced by microgravity or by the indirect effect of space-flight conditions, became conspicuous only in developing vessels at the ultrastructural level. The results suggested that the orientation of microfibrils and their assembly in developing vessels are perturbed by microgravity at the beginning of wall deposition, while they are still able to orient and arrange in thicker and ordered structures at later stages of secondary wall deposition. The process of proper cell-wall building, although not prevented, is perturbed in Space at the early stage of development. This would explain the almost unaltered anatomy of mature structures, accompanied by a slower growth observed in seedlings grown in Space than on Earth.

Incorporating hemlock woolly adelgid impacts into the Forest Vegetation Simulator model

Treesearch

R. Talbot III Trotter; Anthony W. Courter; Richard M. Turcotte; Brad. Onken

2008-01-01

The hemlock woolly adelgid (HWA), Adelges tsugae, is a small aphid-like insect that feeds on the xylem ray parenchyma cells near the base of hemlock needles. This insect, a native of Asia and western North America, was first noted in eastern North America in 1951 and has now spread to infest hemlock in at least 17 states. The increased hemlock...

Sugars from woody tissue photosynthesis reduce xylem vulnerability to cavitation.

PubMed

De Baerdemaeker, Niels J F; Salomón, Roberto Luis; De Roo, Linus; Steppe, Kathy

2017-11-01

Reassimilation of internal CO 2 via woody tissue photosynthesis has a substantial effect on tree carbon income and wood production. However, little is known about its role in xylem vulnerability to cavitation and its implications in drought-driven tree mortality. Young trees of Populus nigra were subjected to light exclusion at the branch and stem levels. After 40 d, measurements of xylem water potential, diameter variation and acoustic emission (AE) were performed in detached branches to obtain acoustic vulnerability curves to cavitation following bench-top dehydration. Acoustic vulnerability curves and derived AE 50 values (i.e. water potential at which 50% of cavitation-related acoustic emissions occur) differed significantly between light-excluded and control branches (AE 50,light-excluded  = -1.00 ± 0.13 MPa; AE 50,control  = -1.45 ± 0.09 MPa; P = 0.007) denoting higher vulnerability to cavitation in light-excluded trees. Woody tissue photosynthesis represents an alternative and immediate source of nonstructural carbohydrates (NSC) that confers lower xylem vulnerability to cavitation via sugar-mediated mechanisms. Embolism repair and xylem structural changes could not explain this observation as the amount of cumulative AE and basic wood density did not differ between treatments. We suggest that woody tissue assimilates might play a role in the synthesis of xylem surfactants for nanobubble stabilization under tension. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Is desiccation tolerance and avoidance reflected in xylem and phloem anatomy of two co-existing arid-zone coniferous trees?: Xylem and Phloem Anatomy

DOE PAGES

Sevanto, Sanna Annika; Ryan, Max; Turin Dickman, L.; ...

2018-03-22

Plants close their stomata during drought to avoid excessive water loss, but species differ in respect to the drought severity at which stomata close. The stomatal closure point is related to xylem anatomy and vulnerability to embolism, but it also has implications for phloem transport, and possibly phloem anatomy to allow sugar transport at low water potentials. Desiccation tolerant plants that close their stomata at severe drought should have smaller xylem conduits and/or fewer and smaller inter-conduit pits to reduce vulnerability to embolism, but more phloem tissue and larger phloem conduits compared to plants that avoid desiccation. These anatomical differencesmore » could be expected to increase in response to long-term reduction in precipitation. To test these hypotheses we used tridimensional synchroton X-ray microtomograph and light microscope imaging of combined xylem and phloem tissues of two coniferous species: one-seed juniper (Juniperus monosperma) and piñon pine (Pinus edulis) subjected to precipitation manipulation treatments. These species show different xylem vulnerability to embolism, contrasting desiccation tolerance, and stomatal closure points. Our results support the hypothesis that desiccation tolerant plants require higher phloem transport capacity than desiccation avoiding plants, but this can be gained through various anatomical adaptations in addition to changing conduit or tissue size.« less

Is desiccation tolerance and avoidance reflected in xylem and phloem anatomy of two co-existing arid-zone coniferous trees?: Xylem and Phloem Anatomy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sevanto, Sanna Annika; Ryan, Max; Turin Dickman, L.

Plants close their stomata during drought to avoid excessive water loss, but species differ in respect to the drought severity at which stomata close. The stomatal closure point is related to xylem anatomy and vulnerability to embolism, but it also has implications for phloem transport, and possibly phloem anatomy to allow sugar transport at low water potentials. Desiccation tolerant plants that close their stomata at severe drought should have smaller xylem conduits and/or fewer and smaller inter-conduit pits to reduce vulnerability to embolism, but more phloem tissue and larger phloem conduits compared to plants that avoid desiccation. These anatomical differencesmore » could be expected to increase in response to long-term reduction in precipitation. To test these hypotheses we used tridimensional synchroton X-ray microtomograph and light microscope imaging of combined xylem and phloem tissues of two coniferous species: one-seed juniper (Juniperus monosperma) and piñon pine (Pinus edulis) subjected to precipitation manipulation treatments. These species show different xylem vulnerability to embolism, contrasting desiccation tolerance, and stomatal closure points. Our results support the hypothesis that desiccation tolerant plants require higher phloem transport capacity than desiccation avoiding plants, but this can be gained through various anatomical adaptations in addition to changing conduit or tissue size.« less

Characterization of AgMaT2, a Plasma Membrane Mannitol Transporter from Celery, Expressed in Phloem Cells, Including Phloem Parenchyma Cells[OA

PubMed Central

Juchaux-Cachau, Marjorie; Landouar-Arsivaud, Lucie; Pichaut, Jean-Philippe; Campion, Claire; Porcheron, Benoit; Jeauffre, Julien; Noiraud-Romy, Nathalie; Simoneau, Philippe; Maurousset, Laurence; Lemoine, Rémi

2007-01-01

A second mannitol transporter, AgMaT2, was identified in celery (Apium graveolens L. var. dulce), a species that synthesizes and transports mannitol. This transporter was successfully expressed in two different heterologous expression systems: baker's yeast (Saccharomyces cerevisiae) cells and tobacco (Nicotiana tabacum) plants (a non-mannitol-producing species). Data indicated that AgMaT2 works as an H+/mannitol cotransporter with a weak selectivity toward other polyol molecules. When expressed in tobacco, AgMaT2 decreased the sensitivity to the mannitol-secreting pathogenic fungi Alternaria longipes, suggesting a role for polyol transporters in defense mechanisms. In celery, in situ hybridization showed that AgMaT2 was expressed in the phloem of leaflets, petioles from young and mature leaves, floral stems, and roots. In the phloem of petioles and leaflets, AgMaT2, as localized with specific antibodies, was present in the plasma membrane of three ontologically related cell types: sieve elements, companion cells, and phloem parenchyma cells. These new data are discussed in relation to the physiological role of AgMaT2 in regulating mannitol fluxes in celery petioles. PMID:17631523

There were no differences in serum HBV DNA level between HBeAg-positive and HBeAg-negative chronic hepatitis B with same liver histological necroinflammation grade but differences among grades 1, 2, 3 and 4 apportioned by the same hepatic parenchyma cell volume.

PubMed

Ke, W-M; Xie, S-B; Li, X-J; Zhang, S-Q; Lai, J; Ye, Y-N; Gao, Z-L; Chen, P-J

2011-09-01

Hepatitis B virus (HBV) DNA levels and liver histological necroinflammation grades are correlated with the antiviral efficacy. It is necessary to clarify the relationship between HBV replication levels apportioned by the same hepatic parenchyma cell volume and severity of liver histological necroinflammation grades in both hepatitis B e antigen (HBeAg)-positive and HBeAg-negative chronic hepatitis B. The serum HBV DNA levels apportioned by the same hepatic parenchyma cell volume were compared between HBeAg-positive and HBeAg-negative chronic hepatitis B as well as among liver histological necroinflammation grades 1, 2, 3 and 4, respectively. There were no differences in the serum HBV DNA levels between HBeAg-positive and HBeAg-negative chronic hepatitis B as well as among liver histological necroinflammation grades 1, 2, 3 and 4. However, there were differences in the serum HBV DNA levels apportioned by the same hepatic parenchyma cell volume among liver histological necroinflammation grades 1, 2, 3 and 4 in both HBeAg-positive and HBeAg-negative chronic hepatitis B, respectively. There were no differences in HBV DNA levels with the same liver histological necroinflammation grade activated by HBV wild-type and variant strains. After the differences in hepatic parenchyma cell volume for HBV replication of the same liver histological necroinflammation grade accompanied by different hepatic fibrosis stages were adjusted, the serum HBV DNA level apportioned by the same hepatic parenchyma cell volume was correlated with the severity of liver histological necroinflammation grade. © 2011 Blackwell Publishing Ltd.

Isolation of 4-coumarate Co-A ligase gene promoter from loblolly pine (Pinus taeda) and characterization of tissue-specific activity in transgenic tobacco.

PubMed

Osakabe, Yuriko; Osakabe, Keishi; Chiang, Vincent L

2009-01-01

We characterized promoter activity of a phenylpropanoid biosynthetic gene encoding 4-coumarate Co-A ligase (4CL), Pta4Clalpha, from Pinus taeda. Histochemical- and quantitative assays of GUS expression in the vascular tissue were performed using transgenic tobacco plants expressing promoter-GUS reporters. Deletion analysis of the Pta4Clalpha promoter showed that the region -524 to -252, which has two AC elements, controls the high expression levels in ray-parenchyma cells of older tobacco stems. High activity level of the promoter domain of Pta4CLalpha was also detected in the xylem cells under bending stress. DNA-protein complexes were detected in the reactions of the Pta4CLalpha promoter fragments with the nuclear proteins of xylem of P. taeda. The AC elements in the Pta4CLalpha promoter appeared to have individual roles during xylem development that are activated in a coordinated manner in response to stress in transgenic tobacco.

Conservation of element concentration in xylem sap of red spruce

Treesearch

Kevin T. Smith; Walter C. Shortle

2001-01-01

We investigated the chemistry of xylem sap as a marker of red spruce metabolism and soil chemistry at three locations in northern New England. A Scholander pressure chamber was used to extract xylem sap from roots and branches cut from mature trees in early June and September. Root sap contained significantly greater concentrations of K, Ca, Mg, Mn, and A1 than branch...

A rhamnose-rich O-antigen mediates adhesion, virulence, and host colonization for the xylem-limited phytopathogen Xylella fastidiosa.

PubMed

Clifford, Jennifer C; Rapicavoli, Jeannette N; Roper, M Caroline

2013-06-01

Xylella fastidiosa is a gram-negative, xylem-limited bacterium that causes a lethal disease of grapevine called Pierce's disease. Lipopolysaccharide (LPS) composes approximately 75% of the outer membrane of gram-negative bacteria and, because it is largely displayed on the cell surface, it mediates interactions between the bacterial cell and its surrounding environment. LPS is composed of a conserved lipid A-core oligosaccharide component and a variable O-antigen portion. By targeting a key O-antigen biosynthetic gene, we demonstrate the contribution of the rhamnose-rich O-antigen to surface attachment, cell-cell aggregation, and biofilm maturation: critical steps for successful infection of the host xylem tissue. Moreover, we have demonstrated that a fully formed O-antigen moiety is an important virulence factor for Pierce's disease development in grape and that depletion of the O-antigen compromises its ability to colonize the host. It has long been speculated that cell-surface polysaccharides play a role in X. fastidiosa virulence and this study confirms that LPS is a major virulence factor for this important agricultural pathogen.

De novo transcriptome assemblies of four xylem sap-feeding insects

PubMed Central

Tassone, Erica E.; Cowden, Charles C.

2017-01-01

Abstract Background: Spittle bugs and sharpshooters are well-known xylem sap-feeding insects and vectors of the phytopathogenic bacterium Xylella fastidiosa (Wells), a causal agent of Pierce's disease of grapevines and other crop diseases. Specialized feeding on nutrient-deficient xylem sap is relatively rare among insect herbivores, and only limited genomic and transcriptomic information has been generated for xylem-sap feeders. To develop a more comprehensive understanding of biochemical adaptations and symbiotic relationships that support survival on a nutritionally austere dietary source, transcriptome assemblies for three sharpshooter species and one spittlebug species were produced. Findings: Trinity-based de novo transcriptome assemblies were generated for all four xylem-sap feeders using raw sequencing data originating from whole-insect preps. Total transcripts for each species ranged from 91 384 for Cuerna arida to 106 998 for Homalodisca liturata with transcript totals for Graphocephala atropunctata and the spittlebug Clastoptera arizonana falling in between. The percentage of transcripts comprising complete open reading frames ranged from 60% for H. liturata to 82% for C. arizonana. Bench-marking universal single-copy orthologs analyses for each dataset indicated quality assemblies and a high degree of completeness for all four species. Conclusions: These four transcriptomes represent a significant expansion of data for insect herbivores that feed exclusively on xylem sap, a nutritionally deficient dietary source relative to other plant tissues and fluids. Comparison of transcriptome data with insect herbivores that utilize other dietary sources may illuminate fundamental differences in the biochemistry of dietary specialization. PMID:28327966

Xylem Surfactants Introduce a New Element to the Cohesion-Tension Theory1[OPEN

PubMed Central

Espino, Susana; Nima, Neda; Do, Aissa Y.T.; Michaud, Joseph M.; Papahadjopoulos-Sternberg, Brigitte; Yang, Jinlong; Steppe, Kathy

2017-01-01

Vascular plants transport water under negative pressure without constantly creating gas bubbles that would disable their hydraulic systems. Attempts to replicate this feat in artificial systems almost invariably result in bubble formation, except under highly controlled conditions with pure water and only hydrophilic surfaces present. In theory, conditions in the xylem should favor bubble nucleation even more: there are millions of conduits with at least some hydrophobic surfaces, and xylem sap is saturated or sometimes supersaturated with atmospheric gas and may contain surface-active molecules that can lower surface tension. So how do plants transport water under negative pressure? Here, we show that angiosperm xylem contains abundant hydrophobic surfaces as well as insoluble lipid surfactants, including phospholipids, and proteins, a composition similar to pulmonary surfactants. Lipid surfactants were found in xylem sap and as nanoparticles under transmission electron microscopy in pores of intervessel pit membranes and deposited on vessel wall surfaces. Nanoparticles observed in xylem sap via nanoparticle-tracking analysis included surfactant-coated nanobubbles when examined by freeze-fracture electron microscopy. Based on their fracture behavior, this technique is able to distinguish between dense-core particles, liquid-filled, bilayer-coated vesicles/liposomes, and gas-filled bubbles. Xylem surfactants showed strong surface activity that reduces surface tension to low values when concentrated as they are in pit membrane pores. We hypothesize that xylem surfactants support water transport under negative pressure as explained by the cohesion-tension theory by coating hydrophobic surfaces and nanobubbles, thereby keeping the latter below the critical size at which bubbles would expand to form embolisms. PMID:27927981

Improved pulmonary nodule classification utilizing quantitative lung parenchyma features.

PubMed

Dilger, Samantha K N; Uthoff, Johanna; Judisch, Alexandra; Hammond, Emily; Mott, Sarah L; Smith, Brian J; Newell, John D; Hoffman, Eric A; Sieren, Jessica C

2015-10-01

Current computer-aided diagnosis (CAD) models for determining pulmonary nodule malignancy characterize nodule shape, density, and border in computed tomography (CT) data. Analyzing the lung parenchyma surrounding the nodule has been minimally explored. We hypothesize that improved nodule classification is achievable by including features quantified from the surrounding lung tissue. To explore this hypothesis, we have developed expanded quantitative CT feature extraction techniques, including volumetric Laws texture energy measures for the parenchyma and nodule, border descriptors using ray-casting and rubber-band straightening, histogram features characterizing densities, and global lung measurements. Using stepwise forward selection and leave-one-case-out cross-validation, a neural network was used for classification. When applied to 50 nodules (22 malignant and 28 benign) from high-resolution CT scans, 52 features (8 nodule, 39 parenchymal, and 5 global) were statistically significant. Nodule-only features yielded an area under the ROC curve of 0.918 (including nodule size) and 0.872 (excluding nodule size). Performance was improved through inclusion of parenchymal (0.938) and global features (0.932). These results show a trend toward increased performance when the parenchyma is included, coupled with the large number of significant parenchymal features that support our hypothesis: the pulmonary parenchyma is influenced differentially by malignant versus benign nodules, assisting CAD-based nodule characterizations.

Trypanosoma brucei Invasion and T-Cell Infiltration of the Brain Parenchyma in Experimental Sleeping Sickness: Timing and Correlation with Functional Changes.

PubMed

Laperchia, Claudia; Palomba, Maria; Seke Etet, Paul F; Rodgers, Jean; Bradley, Barbara; Montague, Paul; Grassi-Zucconi, Gigliola; Kennedy, Peter G E; Bentivoglio, Marina

2016-12-01

The timing of Trypanosoma brucei entry into the brain parenchyma to initiate the second, meningoencephalitic stage of human African trypanosomiasis or sleeping sickness is currently debated and even parasite invasion of the neuropil has been recently questioned. Furthermore, the relationship between neurological features and disease stage are unclear, despite the important diagnostic and therapeutic implications. Using a rat model of chronic Trypanosoma brucei brucei infection we determined the timing of parasite and T-cell neuropil infiltration and its correlation with functional changes. Parasite DNA was detected using trypanosome-specific PCR. Body weight and sleep structure alterations represented by sleep-onset rapid eye movement (SOREM) periods, reported in human and experimental African trypanosomiasis, were monitored. The presence of parasites, as well as CD4+ and CD8+ T-cells in the neuropil was assessed over time in the brain of the same animals by immunocytochemistry and quantitative analyses. Trypanosome DNA was present in the brain at day 6 post-infection and increased more than 15-fold by day 21. Parasites and T-cells were observed in the parenchyma from day 9 onwards. Parasites traversing blood vessel walls were observed in the hypothalamus and other brain regions. Body weight gain was reduced from day 7 onwards. SOREM episodes started in most cases early after infection, with an increase in number and duration after parasite neuroinvasion. These findings demonstrate invasion of the neuropil over time, after an initial interval, by parasites and lymphocytes crossing the blood-brain barrier, and show that neurological features can precede this event. The data thus challenge the current clinical and cerebrospinal fluid criteria of disease staging.

Trypanosoma brucei Invasion and T-Cell Infiltration of the Brain Parenchyma in Experimental Sleeping Sickness: Timing and Correlation with Functional Changes

PubMed Central

Laperchia, Claudia; Palomba, Maria; Seke Etet, Paul F.; Rodgers, Jean; Bradley, Barbara; Montague, Paul; Grassi-Zucconi, Gigliola; Bentivoglio, Marina

2016-01-01

Background The timing of Trypanosoma brucei entry into the brain parenchyma to initiate the second, meningoencephalitic stage of human African trypanosomiasis or sleeping sickness is currently debated and even parasite invasion of the neuropil has been recently questioned. Furthermore, the relationship between neurological features and disease stage are unclear, despite the important diagnostic and therapeutic implications. Methodology Using a rat model of chronic Trypanosoma brucei brucei infection we determined the timing of parasite and T-cell neuropil infiltration and its correlation with functional changes. Parasite DNA was detected using trypanosome-specific PCR. Body weight and sleep structure alterations represented by sleep-onset rapid eye movement (SOREM) periods, reported in human and experimental African trypanosomiasis, were monitored. The presence of parasites, as well as CD4+ and CD8+ T-cells in the neuropil was assessed over time in the brain of the same animals by immunocytochemistry and quantitative analyses. Principal findings Trypanosome DNA was present in the brain at day 6 post-infection and increased more than 15-fold by day 21. Parasites and T-cells were observed in the parenchyma from day 9 onwards. Parasites traversing blood vessel walls were observed in the hypothalamus and other brain regions. Body weight gain was reduced from day 7 onwards. SOREM episodes started in most cases early after infection, with an increase in number and duration after parasite neuroinvasion. Conclusion These findings demonstrate invasion of the neuropil over time, after an initial interval, by parasites and lymphocytes crossing the blood-brain barrier, and show that neurological features can precede this event. The data thus challenge the current clinical and cerebrospinal fluid criteria of disease staging. PMID:28002454

Auxin Influx Carriers Control Vascular Patterning and Xylem Differentiation in Arabidopsis thaliana

PubMed Central

Siligato, Riccardo; Alonso, Jose M.; Swarup, Ranjan; Bennett, Malcolm J.; Mähönen, Ari Pekka; Caño-Delgado, Ana I.; Ibañes, Marta

2015-01-01

Auxin is an essential hormone for plant growth and development. Auxin influx carriers AUX1/LAX transport auxin into the cell, while auxin efflux carriers PIN pump it out of the cell. It is well established that efflux carriers play an important role in the shoot vascular patterning, yet the contribution of influx carriers to the shoot vasculature remains unknown. Here, we combined theoretical and experimental approaches to decipher the role of auxin influx carriers in the patterning and differentiation of vascular tissues in the Arabidopsis inflorescence stem. Our theoretical analysis predicts that influx carriers facilitate periodic patterning and modulate the periodicity of auxin maxima. In agreement, we observed fewer and more spaced vascular bundles in quadruple mutants plants of the auxin influx carriers aux1lax1lax2lax3. Furthermore, we show AUX1/LAX carriers promote xylem differentiation in both the shoot and the root tissues. Influx carriers increase cytoplasmic auxin signaling, and thereby differentiation. In addition to this cytoplasmic role of auxin, our computational simulations propose a role for extracellular auxin as an inhibitor of xylem differentiation. Altogether, our study shows that auxin influx carriers AUX1/LAX regulate vascular patterning and differentiation in plants. PMID:25922946

Effects of environmental conditions on onset of xylem growth in Pinus sylvestris under drought

PubMed Central

Swidrak, Irene; Gruber, Andreas; Kofler, Werner; Oberhuber, Walter

2012-01-01

Summary We determined influence of environmental factors (air and soil temperature, precipitation, photoperiod) on onset of xylem growth in Scots pine (Pinus sylvestris L.) within a dry inner Alpine valley (750 m a.s.l., Tyrol, Austria) by repeatedly sampling micro-cores throughout 2007-2010 at two sites (xeric and dry-mesic) at the start of the growing season. Temperature sums were calculated in degree-days (DD) ≥ 5 °C from 1 January and 20 March, i.e. spring equinox, to account for photoperiodic control of release from winter dormancy. Threshold temperatures at which xylogenesis had a 0.5 probability of being active were calculated by logistic regression. Onset of xylem growth, which was not significantly different between the xeric and dry-mesic site, ranged from mid-April in 2007 to early May in 2008. Among most study years statistically significant differences (P < 0.05) in onset of xylem growth were detected. Mean air temperature sums calculated from 1 January until onset of xylem growth were 230 ± 44 DD (mean ± standard deviation) at the xeric and 205 ± 36 DD at the dry-mesic site. Temperature sums calculated from spring equinox until onset of xylem growth showed quite less variability during the four year study period amounting to 144 ± 10 and 137 ± 12 DD at the xeric and dry-mesic site, respectively. At both sites xylem growth was active when daily minimum, mean and maximum air temperatures were 5.3, 10.1 and 16.2 °C, respectively. Soil temperature thresholds and DD until onset of xylem growth differed significantly between sites indicating minor importance of root-zone temperature for onset of xylem growth. Although spring precipitation is known to limit radial growth in P. sylvestris exposed to dry inner Alpine climate, results of this study revealed that (i) a daily minimum air temperature threshold for onset of xylem growth in the range of 5-6 °C exists and (ii) air temperature sum rather than precipitation or soil temperature triggers start

Source of Sustained Voltage Difference between the Xylem of a Potted Ficus benjamina Tree and Its Soil

PubMed Central

Love, Christopher J.; Zhang, Shuguang; Mershin, Andreas

2008-01-01

It has long been known that there is a sustained electrical potential (voltage) difference between the xylem of many plants and their surrounding soil, but the mechanism behind this voltage has remained controversial. After eliminating any extraneous capacitive or inductive couplings and ground-mediated electric current flows, we have measured sustained differences of 50–200 mV between the xylem region of a Faraday-caged, intact, potted Ficus benjamina tree and its soil, as well as between its cut branches and soils and ionic solutions standardized to various pH values. Using identical platinum electrodes, no correlation between the voltage and time of day, illumination, sap flow, electrode elevation, or ionic composition of soil was found, suggesting no direct connection to simple dissimilar-metal redox reactions or transpirational activity. Instead, a clear relationship between the voltage polarity and magnitude and the pH difference between xylem and soil was observed. We attribute these sustained voltages to a biological concentration cell likely set up by the homeostatic mechanisms of the tree. Potential applications of this finding are briefly explored. PMID:18698415

Specification of Cortical Parenchyma and Stele of Maize Primary Roots by Asymmetric Levels of Auxin, Cytokinin, and Cytokinin-Regulated Proteins1[C][W][OA

PubMed Central

Saleem, Muhammad; Lamkemeyer, Tobias; Schützenmeister, André; Madlung, Johannes; Sakai, Hajime; Piepho, Hans-Peter; Nordheim, Alfred; Hochholdinger, Frank

2010-01-01

In transverse orientation, maize (Zea mays) roots are composed of a central stele that is embedded in multiple layers of cortical parenchyma. The stele functions in the transport of water, nutrients, and photosynthates, while the cortical parenchyma fulfills metabolic functions that are not very well characterized. To better understand the molecular functions of these root tissues, protein- and phytohormone-profiling experiments were conducted. Two-dimensional gel electrophoresis combined with electrospray ionization tandem mass spectrometry identified 59 proteins that were preferentially accumulated in the cortical parenchyma and 11 stele-specific proteins. Hormone profiling revealed preferential accumulation of indole acetic acid and its conjugate indole acetic acid-aspartate in the stele and predominant localization of the cytokinin cis-zeatin, its precursor cis-zeatin riboside, and its conjugate cis-zeatin O-glucoside in the cortical parenchyma. A root-specific β-glucosidase that functions in the hydrolysis of cis-zeatin O-glucoside was preferentially accumulated in the cortical parenchyma. Similarly, four enzymes involved in ammonium assimilation that are regulated by cytokinin were preferentially accumulated in the cortical parenchyma. The antagonistic distribution of auxin and cytokinin in the stele and cortical parenchyma, together with the cortical parenchyma-specific accumulation of cytokinin-regulated proteins, suggest a molecular framework that specifies the function of these root tissues that also play a role in the formation of lateral roots from pericycle and endodermis cells. PMID:19933382

De novo transcriptome assemblies of four xylem sap-feeding insects.

PubMed

Tassone, Erica E; Cowden, Charles C; Castle, S J

2017-03-01

Spittle bugs and sharpshooters are well-known xylem sap-feeding insects and vectors of the phytopathogenic bacterium Xylella fastidiosa (Wells), a causal agent of Pierce's disease of grapevines and other crop diseases. Specialized feeding on nutrient-deficient xylem sap is relatively rare among insect herbivores, and only limited genomic and transcriptomic information has been generated for xylem-sap feeders. To develop a more comprehensive understanding of biochemical adaptations and symbiotic relationships that support survival on a nutritionally austere dietary source, transcriptome assemblies for three sharpshooter species and one spittlebug species were produced. Trinity-based de novo transcriptome assemblies were generated for all four xylem-sap feeders using raw sequencing data originating from whole-insect preps. Total transcripts for each species ranged from 91 384 for Cuerna arida to 106 998 for Homalodisca liturata with transcript totals for Graphocephala atropunctata and the spittlebug Clastoptera arizonana falling in between. The percentage of transcripts comprising complete open reading frames ranged from 60% for H. liturata to 82% for C. arizonana. Bench-marking universal single-copy orthologs analyses for each dataset indicated quality assemblies and a high degree of completeness for all four species. These four transcriptomes represent a significant expansion of data for insect herbivores that feed exclusively on xylem sap, a nutritionally deficient dietary source relative to other plant tissues and fluids. Comparison of transcriptome data with insect herbivores that utilize other dietary sources may illuminate fundamental differences in the biochemistry of dietary specialization. Published by Oxford University Press on behalf of GIGSCI 2017. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Dissimilarity representations in lung parenchyma classification

NASA Astrophysics Data System (ADS)

Sørensen, Lauge; de Bruijne, Marleen

2009-02-01

A good problem representation is important for a pattern recognition system to be successful. The traditional approach to statistical pattern recognition is feature representation. More specifically, objects are represented by a number of features in a feature vector space, and classifiers are built in this representation. This is also the general trend in lung parenchyma classification in computed tomography (CT) images, where the features often are measures on feature histograms. Instead, we propose to build normal density based classifiers in dissimilarity representations for lung parenchyma classification. This allows for the classifiers to work on dissimilarities between objects, which might be a more natural way of representing lung parenchyma. In this context, dissimilarity is defined between CT regions of interest (ROI)s. ROIs are represented by their CT attenuation histogram and ROI dissimilarity is defined as a histogram dissimilarity measure between the attenuation histograms. In this setting, the full histograms are utilized according to the chosen histogram dissimilarity measure. We apply this idea to classification of different emphysema patterns as well as normal, healthy tissue. Two dissimilarity representation approaches as well as different histogram dissimilarity measures are considered. The approaches are evaluated on a set of 168 CT ROIs using normal density based classifiers all showing good performance. Compared to using histogram dissimilarity directly as distance in a emph{k} nearest neighbor classifier, which achieves a classification accuracy of 92.9%, the best dissimilarity representation based classifier is significantly better with a classification accuracy of 97.0% (text{emph{p" border="0" class="imgtopleft"> = 0.046).

Separation and characterization of needle and xylem maritime pine proteins.

PubMed

Costa, P; Pionneau, C; Bauw, G; Dubos, C; Bahrmann, N; Kremer, A; Frigerio, J M; Plomion, C

1999-01-01

Two-dimensional gel electrophoresis (2-DE) and image analysis are currently used for proteome analysis in maritime pine (Pinus pinaster Ait.). This study presents a database of expressed proteins extracted from needles and xylem, two important tissues for growth and wood formation. Electrophoresis was carried out by isoelectric focusing (IEF) in the first dimension and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in the second. Silver staining made it possible to detect an average of 900 and 600 spots on 2-DE gels from needles and xylem, respectively. A total of 28 xylem and 35 needle proteins were characterized by internal peptide microsequencing. Out of these 63 proteins, 57 (90%) could be identified based on amino acid similarity with known proteins, of which 24 (42%) have already been described in conifers. Overall comparison of both tissues indicated that 29% and 36% of the spots were specific to xylem and needles, respectively, while the other spots were of identical molecular weight and isoelectric point. The homology of spot location in 2-DE patterns was further validated by sequence analysis of proteins present in both tissues. A proteomic database of maritime pine is accessible on the internet (http://www.pierroton.inra.fr/genetics/2D/).

Xylem anatomy correlates with gas exchange, water-use efficiency and growth performance under contrasting water regimes: evidence from Populus deltoides x Populus nigra hybrids.

PubMed

Fichot, Régis; Laurans, Françoise; Monclus, Romain; Moreau, Alain; Pilate, Gilles; Brignolas, Franck

2009-12-01

Six Populus deltoides Bartr. ex Marsh. x P. nigra L. genotypes were selected to investigate whether stem xylem anatomy correlated with gas exchange rates, water-use efficiency (WUE) and growth performance. Clonal copies of the genotypes were grown in a two-plot common garden test under contrasting water regimes, with one plot maintained irrigated and the other one subjected to moderate summer water deficit. The six genotypes displayed a large range of xylem anatomy, mean vessel and fibre diameter varying from about 40 to 60 microm and from 7.5 to 10.5 microm, respectively. Decreased water availability resulted in a reduced cell size and an important rise in vessel density, but the extent of xylem plasticity was both genotype and trait dependent. Vessel diameter and theoretical xylem-specific hydraulic conductivity correlated positively with stomatal conductance, carbon isotope discrimination and growth performance-related traits and negatively with intrinsic WUE, especially under water deficit conditions. Vessel diameter and vessel density measured under water deficit conditions correlated with the relative losses in biomass production in response to water deprivation; this resulted from the fact that a more plastic xylem structure was generally accompanied by a larger loss in biomass production.

Analysis of HRCT-derived xylem network reveals reverse flow in some vessels

USDA-ARS?s Scientific Manuscript database

Flow in xylem vessels is modeled based on constructions of three dimensional xylem networks derived from High Resolution Computed Tomography (HRCT) images of grapevine (Vitis vinifera) stems. Flow in 6-14% of the vessels was found to be oriented in the opposite direction to the bulk flow under norma...

Effects of environmental conditions on onset of xylem growth in Pinus sylvestris under drought.

PubMed

Swidrak, Irene; Gruber, Andreas; Kofler, Werner; Oberhuber, Walter

2011-05-01

We determined the influence of environmental factors (air and soil temperature, precipitation, photoperiod) on onset of xylem growth in Scots pine (Pinus sylvestris L.) within a dry inner Alpine valley (750 m a.s.l., Tyrol, Austria) by repeatedly sampling micro-cores throughout 2007-10 at two sites (xeric and dry-mesic) at the start of the growing season. Temperature sums were calculated in degree-days (DD) ≥5 °C from 1 January and 20 March, i.e., spring equinox, to account for photoperiodic control of release from winter dormancy. Threshold temperatures at which xylogenesis had a 0.5 probability of being active were calculated by logistic regression. Onset of xylem growth, which was not significantly different between the xeric and dry-mesic sites, ranged from mid-April in 2007 to early May in 2008. Among most study years, statistically significant differences (P<0.05) in onset of xylem growth were detected. Mean air temperature sums calculated from 1 January until onset of xylem growth were 230 ± 44 DD (mean ± standard deviation) at the xeric site and 205 ± 36 DD at the dry-mesic site. Temperature sums calculated from spring equinox until onset of xylem growth showed somewhat less variability during the 4-year study period, amounting to 144 ± 10 and 137 ± 12 DD at the xeric and dry-mesic sites, respectively. At both sites, xylem growth was active when daily minimum, mean and maximum air temperatures were 5.3, 10.1 and 16.2 °C, respectively. Soil temperature thresholds and DD until onset of xylem growth differed significantly between sites, indicating minor importance of root-zone temperature for onset of xylem growth. Although spring precipitation is known to limit radial growth in P. sylvestris exposed to a dry inner Alpine climate, the results of this study revealed that (i) a daily minimum air temperature threshold for onset of xylem growth in the range 5-6 °C exists and (ii) air temperature sum rather than precipitation or soil temperature triggers

Turnip mosaic virus Moves Systemically through Both Phloem and Xylem as Membrane-Associated Complexes1

PubMed Central

Zheng, Huanquan

2015-01-01

Plant viruses move systemically in plants through the phloem. They move as virions or as ribonucleic protein complexes, although it is not clear what these complexes are made of. The approximately 10-kb RNA genome of Turnip mosaic virus (TuMV) encodes a membrane protein, known as 6K2, that induces endomembrane rearrangements for the formation of viral replication factories. These factories take the form of vesicles that contain viral RNA (vRNA) and viral replication proteins. In this study, we report the presence of 6K2-tagged vesicles containing vRNA and the vRNA-dependent RNA polymerase in phloem sieve elements and in xylem vessels. Transmission electron microscopy observations showed the presence in the xylem vessels of vRNA-containing vesicles that were associated with viral particles. Stem-girdling experiments, which leave xylem vessels intact but destroy the surrounding tissues, confirmed that TuMV could establish a systemic infection of the plant by going through xylem vessels. Phloem sieve elements and xylem vessels from Potato virus X-infected plants also contained lipid-associated nonencapsidated vRNA, indicating that the presence of membrane-associated ribonucleic protein complexes in the phloem and xylem may not be limited to TuMV. Collectively, these studies indicate that viral replication factories could end up in the phloem and the xylem. PMID:25717035

How Does Leaf Anatomy Influence Water Transport outside the Xylem?1[OPEN

PubMed Central

Buckley, Thomas N.; Scoffoni, Christine; Sack, Lawren

2015-01-01

Leaves are arguably the most complex and important physicobiological systems in the ecosphere. Yet, water transport outside the leaf xylem remains poorly understood, despite its impacts on stomatal function and photosynthesis. We applied anatomical measurements from 14 diverse species to a novel model of water flow in an areole (the smallest region bounded by minor veins) to predict the impact of anatomical variation across species on outside-xylem hydraulic conductance (Kox). Several predictions verified previous correlational studies: (1) vein length per unit area is the strongest anatomical determinant of Kox, due to effects on hydraulic pathlength and bundle sheath (BS) surface area; (2) palisade mesophyll remains well hydrated in hypostomatous species, which may benefit photosynthesis, (3) BS extensions enhance Kox; and (4) the upper and lower epidermis are hydraulically sequestered from one another despite their proximity. Our findings also provided novel insights: (5) the BS contributes a minority of outside-xylem resistance; (6) vapor transport contributes up to two-thirds of Kox; (7) Kox is strongly enhanced by the proximity of veins to lower epidermis; and (8) Kox is strongly influenced by spongy mesophyll anatomy, decreasing with protoplast size and increasing with airspace fraction and cell wall thickness. Correlations between anatomy and Kox across species sometimes diverged from predicted causal effects, demonstrating the need for integrative models to resolve causation. For example, (9) Kox was enhanced far more in heterobaric species than predicted by their having BS extensions. Our approach provides detailed insights into the role of anatomical variation in leaf function. PMID:26084922

Organic geochemical studies of the transformation of gymnospermous xylem during peatification and coalification to subbituminous coal

USGS Publications Warehouse

Hatcher, P.G.; Lerch, H. E.; Verheyen, T.V.

1990-01-01

It is generally recognized that xylem from trees that are buried in peat swamps is transformed first to huminite macerals in brown coal and then to vitrinite macerals in bituminous coal by processes collectively known as coalification. In order to understand the chemical nature of coalification of xylem and the chemical structures that eventually evolve in coal, we examined a series of gymnospermous xylem samples coalified to varying degrees. The samples included modern fresh xylem, modern degraded xylem in peat, and xylem coalified to ranks of brown coal (lignite B), lignite A, and subbituminous coal. The organic geochemical methods used in this study included solid-state 13C nuclear magnetic resonance (NMR) and pyrolysis/gas chromatography/mass spectrometry. The NMR method provided average compositional information, and the pyrolysis provided detailed molecular information. Although the samples examined include different plants of different geologic ages, they all share a common feature in that they are gymnospermous and presumably have or had a similar kind of lignin. The data obtained in this study provide enough details to allow delineation of specific coalification pathway for the xylem is microbial degradation in peat (peatification), leading to selective removal of cellulosic components. These components constitute a large fraction of the total mass of xylem, usually greater than 50%. Although cellulosic components can survive degradation under certain conditions, their loss during microbial degradation is the rule rather than exception during peatification. As these components of xylem are degraded and lost, lignin, another major component of xylem, is selectively enriched because it is more resistant to microbial degradation than the cellulosic components. Thus, lignin survives peatification in a practically unaltered state and becomes the major precursor of coalified xylem. During its transformation to brown coal and lignite A, lignin in xylem is altered

Antigen-Induced but Not Innate Memory CD8 T Cells Express NKG2D and Are Recruited to the Lung Parenchyma upon Viral Infection.

PubMed

Grau, Morgan; Valsesia, Séverine; Mafille, Julien; Djebali, Sophia; Tomkowiak, Martine; Mathieu, Anne-Laure; Laubreton, Daphné; de Bernard, Simon; Jouve, Pierre-Emmanuel; Ventre, Erwan; Buffat, Laurent; Walzer, Thierry; Leverrier, Yann; Marvel, Jacqueline

2018-05-15

The pool of memory-phenotype CD8 T cells is composed of Ag-induced (AI) and cytokine-induced innate (IN) cells. IN cells have been described as having properties similar to those of AI memory cells. However, we found that pathogen-induced AI memory cells can be distinguished in mice from naturally generated IN memory cells by surface expression of NKG2D. Using this marker, we described the increased functionalities of AI and IN memory CD8 T cells compared with naive cells, as shown by comprehensive analysis of cytokine secretion and gene expression. However, AI differed from IN memory CD8 T cells by their capacity to migrate to the lung parenchyma upon inflammation or infection, a process dependent on their expression of ITGA1/CD49a and ITGA4/CD49d integrins. Copyright © 2018 by The American Association of Immunologists, Inc.

Arabidopsis thaliana as a model species for xylem hydraulics: does size matter?

PubMed Central

Tixier, Aude; Cochard, Hervé; Badel, Eric; Dusotoit-Coucaud, Anaïs; Jansen, Steven; Herbette, Stéphane

2013-01-01

While Arabidopsis thaliana has been proposed as a model species for wood development, the potential of this tiny herb for studying xylem hydraulics remains unexplored and anticipated by scepticism. Inflorescence stems of A. thaliana were used to measure hydraulic conductivity and cavitation resistance, whereas light and electron microscopy allowed observations of vessels. In wild-type plants, measured and theoretical conductivity showed a significant correlation (R 2 = 0.80, P < 0.01). Moreover, scaling of vessel dimensions and intervessel pit structure of A. thaliana were consistent with structure–function relationships of woody plants. The reliability and resolution of the hydraulic methods applied to measure vulnerability to cavitation were addressed by comparing plants grown under different photoperiods or different mutant lines. Sigmoid vulnerability curves of A. thaliana indicated a pressure corresponding to 50% loss of hydraulic conductance (P 50) between –3 and –2.5MPa for short-day and long-day plants, respectively. Polygalacturonase mutants showed a higher P 50 value (–2.25MPa), suggesting a role for pectins in vulnerability to cavitation. The application of A. thaliana as a model species for xylem hydraulics provides exciting possibilities for (1) exploring the molecular basis of xylem anatomical features and (2) understanding genetic mechanisms behind xylem functional traits such as cavitation resistance. Compared to perennial woody species, however, the lesser amount of xylem in A. thaliana has its limitations. PMID:23547109

Arabidopsis thaliana as a model species for xylem hydraulics: does size matter?

PubMed

Tixier, Aude; Cochard, Hervé; Badel, Eric; Dusotoit-Coucaud, Anaïs; Jansen, Steven; Herbette, Stéphane

2013-05-01

While Arabidopsis thaliana has been proposed as a model species for wood development, the potential of this tiny herb for studying xylem hydraulics remains unexplored and anticipated by scepticism. Inflorescence stems of A. thaliana were used to measure hydraulic conductivity and cavitation resistance, whereas light and electron microscopy allowed observations of vessels. In wild-type plants, measured and theoretical conductivity showed a significant correlation (R (2) = 0.80, P < 0.01). Moreover, scaling of vessel dimensions and intervessel pit structure of A. thaliana were consistent with structure-function relationships of woody plants. The reliability and resolution of the hydraulic methods applied to measure vulnerability to cavitation were addressed by comparing plants grown under different photoperiods or different mutant lines. Sigmoid vulnerability curves of A. thaliana indicated a pressure corresponding to 50% loss of hydraulic conductance (P 50) between -3 and -2.5MPa for short-day and long-day plants, respectively. Polygalacturonase mutants showed a higher P 50 value (-2.25MPa), suggesting a role for pectins in vulnerability to cavitation. The application of A. thaliana as a model species for xylem hydraulics provides exciting possibilities for (1) exploring the molecular basis of xylem anatomical features and (2) understanding genetic mechanisms behind xylem functional traits such as cavitation resistance. Compared to perennial woody species, however, the lesser amount of xylem in A. thaliana has its limitations.

Persistent Supercooling of Reproductive Shoots Is Enabled by Structural Ice Barriers Being Active Despite an Intact Xylem Connection

PubMed Central

Pfaller, Kristian; Wagner, Johanna

2016-01-01

Extracellular ice nucleation usually occurs at mild subzero temperatures in most plants. For persistent supercooling of certain plant parts ice barriers are necessary to prevent the entry of ice from already frozen tissues. The reproductive shoot of Calluna vulgaris is able to supercool down to below -22°C throughout all developmental stages (shoot elongation, flowering, fruiting) despite an established xylem conductivity. After localization of the persistent ice barrier between the reproductive and vegetative shoot at the base of the pedicel by infrared differential thermal analysis, the currently unknown structural features of the ice barrier tissue were anatomically analyzed on cross and longitudinal sections. The ice barrier tissue was recognized as a 250 μm long constriction zone at the base of the pedicel that lacked pith tissue and intercellular spaces. Most cell walls in this region were thickened and contained hydrophobic substances (lignin, suberin, and cutin). A few cell walls had what appeared to be thicker cellulose inclusions. In the ice barrier tissue, the area of the xylem was as much as 5.7 times smaller than in vegetative shoots and consisted of tracheids only. The mean number of conducting units in the xylem per cross section was reduced to 3.5% of that in vegetative shoots. Diameter of conducting units and tracheid length were 70% and 60% (respectively) of that in vegetative shoots. From vegetative shoots water transport into the ice barrier must pass pit membranes that are likely impermeable to ice. Pit apertures were about 1.9 μm x 0.7 μm, which was significantly smaller than in the vegetative shoot. The peculiar anatomical features of the xylem at the base of the pedicel suggest that the diameter of pores in pit membranes could be the critical constriction for ice propagation into the persistently supercooled reproductive shoots of C. vulgaris. PMID:27632365

Persistent Supercooling of Reproductive Shoots Is Enabled by Structural Ice Barriers Being Active Despite an Intact Xylem Connection.

PubMed

Kuprian, Edith; Tuong, Tan D; Pfaller, Kristian; Wagner, Johanna; Livingston, David P; Neuner, Gilbert

2016-01-01

Extracellular ice nucleation usually occurs at mild subzero temperatures in most plants. For persistent supercooling of certain plant parts ice barriers are necessary to prevent the entry of ice from already frozen tissues. The reproductive shoot of Calluna vulgaris is able to supercool down to below -22°C throughout all developmental stages (shoot elongation, flowering, fruiting) despite an established xylem conductivity. After localization of the persistent ice barrier between the reproductive and vegetative shoot at the base of the pedicel by infrared differential thermal analysis, the currently unknown structural features of the ice barrier tissue were anatomically analyzed on cross and longitudinal sections. The ice barrier tissue was recognized as a 250 μm long constriction zone at the base of the pedicel that lacked pith tissue and intercellular spaces. Most cell walls in this region were thickened and contained hydrophobic substances (lignin, suberin, and cutin). A few cell walls had what appeared to be thicker cellulose inclusions. In the ice barrier tissue, the area of the xylem was as much as 5.7 times smaller than in vegetative shoots and consisted of tracheids only. The mean number of conducting units in the xylem per cross section was reduced to 3.5% of that in vegetative shoots. Diameter of conducting units and tracheid length were 70% and 60% (respectively) of that in vegetative shoots. From vegetative shoots water transport into the ice barrier must pass pit membranes that are likely impermeable to ice. Pit apertures were about 1.9 μm x 0.7 μm, which was significantly smaller than in the vegetative shoot. The peculiar anatomical features of the xylem at the base of the pedicel suggest that the diameter of pores in pit membranes could be the critical constriction for ice propagation into the persistently supercooled reproductive shoots of C. vulgaris.

78 FR 77649 - Notification of Proposed Production Activity, Xylem Water Systems USA LLC, Subzone 37D...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-24

... DEPARTMENT OF COMMERCE Foreign-Trade Zones Board [B-106-2013] Notification of Proposed Production Activity, Xylem Water Systems USA LLC, Subzone 37D, (Centrifugal, Submersible Pumps and Related Components), Auburn, New York Xylem Water Systems USA LLC (Xylem), operator of Subzone 37D, submitted a notification of proposed production activity to...

Seasonal dynamics of mobile carbohydrate pools in phloem and xylem of two alpine timberline conifers.

PubMed

Gruber, A; Pirkebner, D; Oberhuber, W

2013-10-01

Recent studies on non-structural carbohydrate (NSC) reserves in trees focused on xylem NSC reserves, while still little is known about changes in phloem carbohydrate pools, where NSC charging might be significantly different. To gain insight on NSC dynamics in xylem and phloem, we monitored NSC concentrations in stems and roots of Pinus cembra (L.) and Larix decidua (Mill.) growing at the alpine timberline throughout 2011. Species-specific differences affected tree phenology and carbon allocation during the course of the year. After a delayed start in spring, NSC concentrations in L. decidua were significantly higher in all sampled tissues from August until the end of growing season. In both species, NSC concentrations were five to seven times higher in phloem than that in xylem. However, significant correlations between xylem and phloem starch content found for both species indicate a close linkage between long-term carbon reserves in both tissues. In L. decidua also, free sugar concentrations in xylem and phloem were significantly correlated throughout the year, while a lack of correlation between xylem and phloem free sugar pools in P. cembra indicate a decline of phloem soluble carbohydrate pools during periods of high sink demand.

Seasonal dynamics of mobile carbohydrate pools in phloem and xylem of two alpine timberline conifers

PubMed Central

GRUBER, A.; PIRKEBNER, D.; OBERHUBER, W.

2016-01-01

Recent studies on non-structural carbohydrate (NSC) reserves in trees focused on xylem NSC reserves, while still little is known about changes in phloem carbohydrate pools, where NSC charging might be significantly different. To gain insight on NSC dynamics in xylem and phloem, we monitored NSC concentrations in stems and roots of Pinus cembra and Larix decidua growing at the alpine timberline throughout 2011. Species-specific differences affected tree phenology and carbon allocation in the course of the year. After a delayed start in spring, NSC concentrations in Larix decidua were significantly higher in all sampled tissues from August until end of growing season. In both species NSC concentrations were five to seven times higher in phloem than in xylem. However, significant correlations between xylem and phloem starch content found for both species indicate a close linkage between long term carbon reserves in both tissues. In Larix decidua also free sugar concentrations in xylem and phloem were significantly correlated throughout the year, while missing correlations between xylem and phloem free sugar pools in Pinus cembra indicate a decline of phloem soluble carbohydrate pools during periods of high sink demand. PMID:24186941

Metal Complexation in Xylem Fluid 1

PubMed Central

White, Michael C.; Chaney, Rufus L.; Decker, A. Morris

1981-01-01

The capacity of ligands in xylem fluid to form metal complexes was tested with a series of in vitro experiments using paper electrophoresis and radiographs. The xylem fluid was collected hourly for 8 hours from soybean (Glycine max L. Merr.) and tomato (Lycopersicon esculentum Mill.) plants grown in normal and Zn-phytotoxic nutrient solutions. Metal complexation was assayed by anodic or reduced cathodic movement of radionuclides (63Ni, 65Zn, 109Cd, 54Mn) that were presumed to have formed negatively charged complexes. Electrophoretic migration of Ni, Zn, Cd, and Mn added to xylem exudate and spotted on KCl- or KNO3-wetted paper showed that stable Ni, Zn, and Cd metal complexes were formed by exudate ligands. No anodic Mn complexes were observed in this test system. Solution pH, plant species, exudate collection time, and Zn phytotoxicity all affected the amount of metal complex formed in exudate. As the pH increased, there was increased anodic metal movement. Soybean exudate generally bound more of each metal than did tomato exudate. Metal binding usually decreased with increasing exudate collection time, and less metal was bound by the high-Zn exudate. Ni, Zn, Cd, and Mn in exudate added to exudate-wetted paper demonstrated the effect of ligand concentration on stable metal complex formation. Complexes for each metal were demonstratable with this method. Cathodic metal movement increased with time of exudate collection, and it was greater in the high-Zn exudate than in the normal-Zn exudate. A model study illustrated the effect of ligand concentration on metal complex stability in the electrophoretic field. Higher ligand (citric acid) concentrations increased the stability for all metals tested. Images PMID:16661666

Static and dynamic bending has minor effects on xylem hydraulics of conifer branches (Picea abies, Pinus sylvestris).

PubMed

Mayr, Stefan; Bertel, Clara; Dämon, Birgit; Beikircher, Barbara

2014-09-01

The xylem hydraulic efficiency and safety is usually measured on mechanically unstressed samples, although trees may be exposed to combined hydraulic and mechanical stress in the field. We analysed changes in hydraulic conductivity and vulnerability to drought-induced embolism during static bending of Picea abies and Pinus sylvestris branches as well as the effect of dynamic bending on the vulnerability. We hypothesized this mechanical stress to substantially impair xylem hydraulics. Intense static bending caused an only small decrease in hydraulic conductance (-19.5 ± 2.4% in P. abies) but no shift in vulnerability thresholds. Dynamic bending caused a 0.4 and 0.8 MPa decrease of the water potential at 50 and 88% loss of conductivity in P. sylvestris, but did not affect vulnerability thresholds in P. abies. With respect to applied extreme bending radii, effects on plant hydraulics were surprisingly small and are thus probably of minor eco-physiological importance. More importantly, results indicate that available xylem hydraulic analyses (of conifers) sufficiently reflect plant hydraulics under field conditions. © 2014 The Authors. Plant, Cell & Environment published by John Wiley & Sons Ltd.

The metastatic infiltration at the metastasis/brain parenchyma-interface is very heterogeneous and has a significant impact on survival in a prospective study

PubMed Central

Siam, Laila; Bleckmann, Annalen; Chaung, Han-Ning; Mohr, Alexander; Klemm, Florian; Barrantes-Freer, Alonso; Blazquez, Raquel; Wolff, Hendrik A.; Lüke, Florian; Rohde, Veit; Stadelmann, Christine; Pukrop, Tobias

2015-01-01

The current approach to brain metastases resection is macroscopic removal of metastasis until reaching the glial pseudo-capsule (gross total resection (GTR)). However, autopsy studies demonstrated infiltrating metastatic cells into the parenchyma at the metastasis/brain parenchyma (M/BP)-interface. Aims/Methods: To analyze the astrocyte reaction and metastatic infiltration pattern at the M/BP-interface with an organotypic brain slice coculture system. Secondly, to evaluate the significance of infiltrating metastatic tumor cells in a prospective biopsy study. Therefore, after GTR, biopsies were obtained from the brain parenchyma beyond the glial pseudo-capsule and analyzed histomorphologically. Results: The coculture revealed three types of cancer cell infiltration. Interestingly, the astrocyte reaction was significantly different in the coculture with a benign, neuroectodermal-derived cell line. In the prospective biopsy study 58/167 (34.7%) samples revealed infiltrating metastatic cells. Altogether, 25/39 patients (64.1%) had proven to exhibit infiltration in at least one biopsy specimen with significant impact on survival (OS) (3.4 HR; p = 0.009; 2-year OS was 6.6% versus 43.5%). Exceptionally, in the non-infiltrating cohort three patients were long-term survivors. Conclusions: Metastatic infiltration has a significant impact on prognosis. Secondly, the astrocyte reaction at the M/BP-interface is heterogeneous and supports our previous concept of the organ-specific defense against metastatic (organ-foreign) cells. PMID:26299612

Structures of Bordered Pits Potentially Contributing to Isolation of a Refilled Vessel from Negative Xylem Pressure in Stems of Morus australis Poir.: Testing of the Pit Membrane Osmosis and Pit Valve Hypotheses.

PubMed

Ooeda, Hiroki; Terashima, Ichiro; Taneda, Haruhiko

2017-02-01

Two hypotheses have been proposed to explain the mechanism preventing the refilling vessel water from being drained to the neighboring functional vessels under negative pressure. The pit membrane osmosis hypothesis proposes that the xylem parenchyma cells release polysaccharides that are impermeable to the intervessel pit membranes into the refilling vessel; this osmotically counteracts the negative pressure, thereby allowing the vessel to refill. The pit valve hypothesis proposes that gas trapped within intervessel bordered pits isolates the refilling vessel water from the surrounding functional vessels. Here, using the single-vessel method, we assessed these hypotheses in shoots of mulberry (Morus australis Poir.). First, we confirmed the occurrence of xylem refilling under negative pressure in the potted mulberry saplings. To examine the pit membrane osmosis hypothesis, we estimated the semi-permeability of pit membranes for molecules of various sizes and found that the pit membranes were not semi-permeable to polyethylene glycol of molecular mass <20,000. For the pit valve hypothesis, we formed pit valves in the intervessel pits in the short stem segments and measured the maximum liquid pressure up to which gases in bordered pits were retained. The threshold pressure ranged from 0.025 to 0.10 MPa. These values matched the theoretical value calculated from the geometry of the pit chamber (0.0692-0.101 MPa). Our results suggest that gas in the pits is retained by surface tension, even under substantial positive pressure to resolve gases in the refilling vessel, whereas the molecule size required for the pit membrane osmosis mechanism in mulberry would be unrealistically large. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Phototropic bending of non-elongating and radially growing woody stems results from asymmetrical xylem formation.

PubMed

Matsuzaki, Jun; Masumori, Masaya; Tange, Takeshi

2007-05-01

Active phototropic bending of non-elongating and radially growing portion of stems (woody stems) has not been previously documented, whereas negative gravitropic bending is well known. We found phototropic bending in woody stems and searched for the underlying mechanism. We inclined 1-year-old Quercus crispula Blume seedlings and unilaterally illuminated them from a horizontal direction perpendicular to ('normal' illumination) or parallel to ('parallel' illumination) the inclination azimuth. With normal illumination, active phototropic bending and xylem formation could be evaluated separately from the negative gravitropic response and vertical deflection resulting from the weight of the seedlings. One-year-old stems with normal illumination bent significantly, with asymmetrical xylem formation towards the illuminated upper surface and side of the stem, whereas those with parallel illumination showed non-significant lateral bending, with asymmetrical xylem formation only on the upper side. A mechanical model was built on the assumption that a bending moment resulted from the asymmetrical xylem formation during phototropic bending of the woody stems. The model fitted the relationship between the observed spatial distributions of the xylem and the observed lateral bending, and thus supported the hypothesis that phototropic bending of woody stems results from asymmetrical xylem formation, as such occurs during gravitropism.

New insights into pioneer root xylem development: evidence obtained from Populus trichocarpa plants grown under field conditions

PubMed Central

Bagniewska-Zadworna, Agnieszka; Arasimowicz-Jelonek, Magdalena; Smoliński, Dariusz J.; Stelmasik, Agnieszka

2014-01-01

Background and Aims Effective programmed xylogenesis is critical to the structural framework of the plant root system and its central role in the acquisition and long-distance transport of water and nutrients. The process of xylem differentiation in pioneer roots under field conditions is poorly understood. In this study it is hypothesized that xylogenesis, an example of developmental programmed cell death (PCD), in the roots of woody plants demonstrates a clearly defined sequence of events resulting in cell death. A comprehensive analysis was therefore undertaken to identify the stages of xylogenesis in pioneer roots from procambial cells to fully functional vessels with lignified cell walls and secondary cell wall thickenings. Methods Xylem differentiation was monitored in the pioneer roots of Populus trichocarpa at the cytological level using rhizotrons under field conditions. Detection and localization of the signalling molecule nitric oxide (NO) and hydrogen peroxide (H2O2) was undertaken and a detailed examination of nuclear changes during xylogenesis was conducted. In addition, analyses of the expression of genes involved in secondary cell wall synthesis were performed in situ. Key Results The primary event in initially differentiating tracheary elements (TEs) was a burst of NO in thin-walled cells, followed by H2O2 synthesis and the appearance of TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling)-positive nuclei. The first changes in nuclear structure were observed in the early stages of xylogenesis of pioneer roots, prior to lignification; however, the nucleus was detectable under transmission electron microscopy in differentiating cells until the stage at which vacuole integrity was maintained, indicating that their degradation was slow and prolonged. The subsequent sequence of events involved secondary cell wall formation and autophagy. Potential gene markers from the cinnamyl alcohol dehydrogenase (CAD) gene family that were

Hydraulic efficiency and safety of branch xylem increases with height in Sequoia sempervirens (D. Don) crowns.

PubMed

Burgess, Stephen S O; Pittermann, Jarmila; Dawson, Todd E

2006-02-01

The hydraulic limitation hypothesis of Ryan & Yoder (1997, Bioscience 47, 235-242) suggests that water supply to leaves becomes increasingly difficult with increasing tree height. Within the bounds of this hypothesis, we conjectured that the vertical hydrostatic gradient which gravity generates on the water column in tall trees would cause a progressive increase in xylem 'safety' (increased resistance to embolism and implosion) and a concomitant decrease in xylem 'efficiency' (decreased hydraulic conductivity). We based this idea on the historically recognized concept of a safety-efficiency trade-off in xylem function, and tested it by measuring xylem conductivity and vulnerability to embolism of Sequoia sempervirens branches collected at a range of heights. Measurements of resistance of branch xylem to embolism did indeed show an increase in 'safety' with height. However, the expected decrease in xylem 'efficiency' was not observed. Instead, sapwood-specific hydraulic conductivities (Ks) of branches increased slightly, while leaf-specific hydraulic conductivities increased dramatically, with height. The latter could be largely explained by strong vertical gradients in specific leaf area. The increase in Ks with height corresponded to a decrease in xylem wall fraction (a measure of wall thickness), an increase in percentage of earlywood and slight increases in conduit diameter. These changes are probably adaptive responses to the increased transport requirements of leaves growing in the upper canopy where evaporative demand is greater. The lack of a safety-efficiency tradeoff may be explained by opposing height trends in the pit aperture and conduit diameter of tracheids and the major and semi-independent roles these play in determining xylem safety and efficiency, respectively.

Identity and Behavior of Xylem-Residing Bacteria in Rough Lemon Roots of Florida Citrus Trees †

PubMed Central

Gardner, John M.; Feldman, Albert W.; Zablotowicz, Robert M.

1982-01-01

An aseptic vacuum extraction technique was used to obtain xylem fluid from the roots of rough lemon (Citrus jambhiri Lush.) rootstock of Florida citrus trees. Bacteria were consistently isolated from vascular fluid of both healthy and young tree decline-affected trees. Thirteen genera of bacteria were found, the most frequently occurring genera being Pseudomonas (40%), Enterobacter (18%), Bacillus, Corynebacterium, and other gram-positive bacteria (16%), and Serratia (6%). Xylem bacterial counts fluctuated seasonally. Bacterial populations ranged from 0.1 to 22 per mm3 of root tissue (about 102 to 2 × 104 bacteria per g of xylem) when bacterial counts were made on vascular fluid, but these numbers were 10- to 1,000-fold greater when aseptically homogenized xylem tissue was examined similarly. Some of the resident bacteria (4%) are potentially phytopathogenic. It is proposed that xylem bacteria have an important role in the physiology of citrus. PMID:16346030

A broad survey of hydraulic and mechanical safety in the xylem of conifers

PubMed Central

Bouche, Pauline S.; Larter, Maximilien; Domec, Jean-Christophe; Burlett, Régis; Gasson, Peter; Jansen, Steven; Delzon, Sylvain

2014-01-01

Drought-induced forest dieback has been widely reported over the last decades, and the evidence for a direct causal link between survival and hydraulic failure (xylem cavitation) is now well known. Because vulnerability to cavitation is intimately linked to the anatomy of the xylem, the main objective of this study was to better understand the xylem anatomical properties associated with cavitation resistance. An extensive data set of cavitation resistance traits and xylem anatomical properties was developed for 115 conifer species, with special attention given to the micro-morphology of bordered pits. The ratio of torus to pit aperture diameter, so-called torus overlap, increased with increasing cavitation resistance, while the flexibility of the margo does not seem to play a role, suggesting that air-seeding is located at the seal between the aspirated torus and pit aperture. Moreover, punctured tori were reported in various Pinaceae species. Species resistant to cavitation had thicker tracheid walls, while their lumen diameter (conduit size) was only slightly reduced, minimizing the impact on hydraulic conductance. The results also demonstrated (i) the existence of an indirect trade-off between hydraulic safety and mechanical strength; and (ii) a consistency between species distribution and xylem anatomy: species with a wide torus overlap and high valve effects are found in arid environments such as the Mediterranean region. PMID:24916072

Factors Which Affect the Amount of Inorganic Phosphate, Phosphorylcholine, and Phosphorylethanolamine in Xylem Exudate of Tomato Plants 1

PubMed Central

Martin, Barry A.; Tolbert, N. E.

1983-01-01

Phosphate in the xylem exudate of tomato (Lycopersicon esculentum) plants was 70 to 98% inorganic phosphate (Pi), 2 to 30% P-choline, and less than 1% P-ethanolamine. Upon adding 32Pi to the nutrient, Pi in xylem exudate had the same specific activity within 4 hours. P-choline and P-ethanolamine reached the same specific activity only after 96 hours. The amount of Pi in xylem exudate was dependent on Pi concentration in the nutrient and decreased from 1700 to 170 micromolar when Pi in the nutrient decreased from 50 to 2 micromolar. The flux of 0.4 nmoles organic phosphate per minute per gram fresh weight root into the xylem exudate was not affected by the Pi concentration in the nutrient solution unless it was below 1 micromolar. During 7 days of Pi starvation, Pi in the xylem exudate decreased from 1400 to 130 micromolar while concentrations of the two phosphate esters remained unchanged. The concentration of phosphate esters in the xylem exudate was increased by addition of choline or ethanolamine to the nutrient solution, but Pi remained unchanged. Upon adding [14C]choline to the nutrient, 10 times more [14C]P-choline than [14C]choline was in the xylem exudate and 85 to 90% of the ester phosphate was P-choline. When [14C]ethanolamine was added, [14C]P-ethanolamine and [14C]ethanolamine in the xylem sap were equal in amount. P-choline and P-ethanolamine accumulated in leaves of whole plants at the same time and the same proportion as observed for their flux into the xylem exudate. No relationship between the transport of P-choline and Pi in the xylem was established. Rather, the amount of choline in xylem exudate and its incorporation into phosphatidylcholine in the leaf suggest that the root is a site of synthesis of P-choline and P-ethanolamine for phospholipid synthesis in tomato leaves. PMID:16663240

Relating xylem cavitation to transpiration in cotton

USDA-ARS?s Scientific Manuscript database

Acoustic emmisions (AEs) from xylem cavitation events are characteristic of transpiration processes. Even though a body of work employing AE exists with a large number of species, cotton and other agronomically important crops have either not been investigated, or limited information exists. A few s...

Arsenate Impact on the Metabolite Profile, Production, and Arsenic Loading of Xylem Sap in Cucumbers (Cucumis sativus L.)

PubMed Central

Uroic, M. Kalle; Salaün, Pascal; Raab, Andrea; Feldmann, Jörg

2012-01-01

Arsenic uptake and translocation studies on xylem sap focus generally on the concentration and speciation of arsenic in the xylem. Arsenic impact on the xylem sap metabolite profile and its production during short term exposure has not been reported in detail. To investigate this, cucumbers were grown hydroponically and arsenate (AsV) and DMA were used for plant treatment for 24 h. Total arsenic and arsenic speciation in xylem sap was analyzed including a metabolite profiling under AsV stress. Produced xylem sap was quantified and absolute arsenic transported was determined. AsV exposure had a significant impact on the metabolite profile of xylem sap. Four m/z values corresponding to four compounds were up-regulated, one compound down-regulated by AsV exposure. The compound down-regulated was identified to be isoleucine. Furthermore, AsV exposure had a significant influence on sap production, leading to a reduction of up to 96% sap production when plants were exposed to 1000 μg kg−1 AsV. No difference to control plants was observed when plants were exposed to 1000 μg kg−1 DMA. Absolute arsenic amount in xylem sap was the lowest at high AsV exposure. These results show that AsV has a significant impact on the production and metabolite profile of xylem sap. The physiological importance of isoleucine needs further attention. PMID:22536187

Organic geochemical studies of the transformation of gymnospermous xylem during peatification and coalification to subbituminous coal

USGS Publications Warehouse

Hatcher, P.G.; Lerch, H. E.; Verheyen, Vincent T.

1989-01-01

Organic geochemical investigations of peatified and coalified xylem from gymnosperms have provided useful information on the organic transformational processes collectively known as coalification. The combined use of solid-state 13C nuclear magnetic resonance (NMR) and pyrolysis/gas chromatography/mass spectrometry (py/gc/ms) has allowed us to examine the organic composition of peatified and coalified xylem on both a bulk (average) compositional basis and on a detailed molecular basis. We conclude from our studies that coalification of gymnospermous xylem involves the following processes: 1. (1) early selective removal of cellulosic materials so that lignin, a primary constituent of xylem, is transformed to macromolecular aromatic components in coal; 2. (2) modification of gymnospermous lignin by demethylation to form catechol-like structures, and by condensation reactions to induce a high level of cross-linking at an early stage of coalification; and 3. (3) dehydroxylation during increasing coalification to subbituminous coal, the resultant xylem becomes more phenolic in character as the catechol-like structures decrease. ?? 1989.

A tree-parenchyma coupled model for lung ventilation simulation.

PubMed

Pozin, Nicolas; Montesantos, Spyridon; Katz, Ira; Pichelin, Marine; Vignon-Clementel, Irene; Grandmont, Céline

2017-11-01

In this article, we develop a lung ventilation model. The parenchyma is described as an elastic homogenized media. It is irrigated by a space-filling dyadic resistive pipe network, which represents the tracheobronchial tree. In this model, the tree and the parenchyma are strongly coupled. The tree induces an extra viscous term in the system constitutive relation, which leads, in the finite element framework, to a full matrix. We consider an efficient algorithm that takes advantage of the tree structure to enable a fast matrix-vector product computation. This framework can be used to model both free and mechanically induced respiration, in health and disease. Patient-specific lung geometries acquired from computed tomography scans are considered. Realistic Dirichlet boundary conditions can be deduced from surface registration on computed tomography images. The model is compared to a more classical exit compartment approach. Results illustrate the coupling between the tree and the parenchyma, at global and regional levels, and how conditions for the purely 0D model can be inferred. Different types of boundary conditions are tested, including a nonlinear Robin model of the surrounding lung structures. Copyright © 2017 John Wiley & Sons, Ltd.

Changes in the Proteome of Xylem Sap in Brassica oleracea in Response to Fusarium oxysporum Stress

PubMed Central

Pu, Zijing; Ino, Yoko; Kimura, Yayoi; Tago, Asumi; Shimizu, Motoki; Natsume, Satoshi; Sano, Yoshitaka; Fujimoto, Ryo; Kaneko, Kentaro; Shea, Daniel J.; Fukai, Eigo; Fuji, Shin-Ichi; Hirano, Hisashi; Okazaki, Keiichi

2016-01-01

Fusarium oxysporum f.sp. conlutinans (Foc) is a serious root-invading and xylem-colonizing fungus that causes yellowing in Brassica oleracea. To comprehensively understand the interaction between F. oxysporum and B. oleracea, composition of the xylem sap proteome of the non-infected and Foc-infected plants was investigated in both resistant and susceptible cultivars using liquid chromatography-tandem mass spectrometry (LC-MS/MS) after in-solution digestion of xylem sap proteins. Whole genome sequencing of Foc was carried out and generated a predicted Foc protein database. The predicted Foc protein database was then combined with the public B. oleracea and B. rapa protein databases downloaded from Uniprot and used for protein identification. About 200 plant proteins were identified in the xylem sap of susceptible and resistant plants. Comparison between the non-infected and Foc-infected samples revealed that Foc infection causes changes to the protein composition in B. oleracea xylem sap where repressed proteins accounted for a greater proportion than those of induced in both the susceptible and resistant reactions. The analysis on the proteins with concentration change > = 2-fold indicated a large portion of up- and down-regulated proteins were those acting on carbohydrates. Proteins with leucine-rich repeats and legume lectin domains were mainly induced in both resistant and susceptible system, so was the case of thaumatins. Twenty-five Foc proteins were identified in the infected xylem sap and 10 of them were cysteine-containing secreted small proteins that are good candidates for virulence and/or avirulence effectors. The findings of differential response of protein contents in the xylem sap between the non-infected and Foc-infected samples as well as the Foc candidate effectors secreted in xylem provide valuable insights into B. oleracea-Foc interactions. PMID:26870056

Changes in the Proteome of Xylem Sap in Brassica oleracea in Response to Fusarium oxysporum Stress.

PubMed

Pu, Zijing; Ino, Yoko; Kimura, Yayoi; Tago, Asumi; Shimizu, Motoki; Natsume, Satoshi; Sano, Yoshitaka; Fujimoto, Ryo; Kaneko, Kentaro; Shea, Daniel J; Fukai, Eigo; Fuji, Shin-Ichi; Hirano, Hisashi; Okazaki, Keiichi

2016-01-01

Fusarium oxysporum f.sp. conlutinans (Foc) is a serious root-invading and xylem-colonizing fungus that causes yellowing in Brassica oleracea. To comprehensively understand the interaction between F. oxysporum and B. oleracea, composition of the xylem sap proteome of the non-infected and Foc-infected plants was investigated in both resistant and susceptible cultivars using liquid chromatography-tandem mass spectrometry (LC-MS/MS) after in-solution digestion of xylem sap proteins. Whole genome sequencing of Foc was carried out and generated a predicted Foc protein database. The predicted Foc protein database was then combined with the public B. oleracea and B. rapa protein databases downloaded from Uniprot and used for protein identification. About 200 plant proteins were identified in the xylem sap of susceptible and resistant plants. Comparison between the non-infected and Foc-infected samples revealed that Foc infection causes changes to the protein composition in B. oleracea xylem sap where repressed proteins accounted for a greater proportion than those of induced in both the susceptible and resistant reactions. The analysis on the proteins with concentration change > = 2-fold indicated a large portion of up- and down-regulated proteins were those acting on carbohydrates. Proteins with leucine-rich repeats and legume lectin domains were mainly induced in both resistant and susceptible system, so was the case of thaumatins. Twenty-five Foc proteins were identified in the infected xylem sap and 10 of them were cysteine-containing secreted small proteins that are good candidates for virulence and/or avirulence effectors. The findings of differential response of protein contents in the xylem sap between the non-infected and Foc-infected samples as well as the Foc candidate effectors secreted in xylem provide valuable insights into B. oleracea-Foc interactions.

A broad survey of hydraulic and mechanical safety in the xylem of conifers.

PubMed

Bouche, Pauline S; Larter, Maximilien; Domec, Jean-Christophe; Burlett, Régis; Gasson, Peter; Jansen, Steven; Delzon, Sylvain

2014-08-01

Drought-induced forest dieback has been widely reported over the last decades, and the evidence for a direct causal link between survival and hydraulic failure (xylem cavitation) is now well known. Because vulnerability to cavitation is intimately linked to the anatomy of the xylem, the main objective of this study was to better understand the xylem anatomical properties associated with cavitation resistance. An extensive data set of cavitation resistance traits and xylem anatomical properties was developed for 115 conifer species, with special attention given to the micro-morphology of bordered pits. The ratio of torus to pit aperture diameter, so-called torus overlap, increased with increasing cavitation resistance, while the flexibility of the margo does not seem to play a role, suggesting that air-seeding is located at the seal between the aspirated torus and pit aperture. Moreover, punctured tori were reported in various Pinaceae species. Species resistant to cavitation had thicker tracheid walls, while their lumen diameter (conduit size) was only slightly reduced, minimizing the impact on hydraulic conductance. The results also demonstrated (i) the existence of an indirect trade-off between hydraulic safety and mechanical strength; and (ii) a consistency between species distribution and xylem anatomy: species with a wide torus overlap and high valve effects are found in arid environments such as the Mediterranean region. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.

In vivo dynamic analysis of water refilling in embolized xylem vessels of intact Zea mays leaves

PubMed Central

Ryu, Jeongeun; Hwang, Bae Geun; Lee, Sang Joon

2016-01-01

Background and Aims The refilling of embolized xylem vessels under tension is a major issue in water transport among vascular plants. However, xylem embolism and refilling remain poorly understood because of technical limitations. Direct observation of embolism repair in intact plants is essential to understand the biophysical aspects of water refilling in embolized xylem vessels. This paper reports on details of the water refilling process in leaves of the intact herbaceous monocot plant Zea mays and its refilling kinetics obtained by a direct visualization technique. Methods A synchrotron X-ray micro-imaging technique was used to monitor water refilling in embolized xylem vessels of intact maize leaves. Xylem embolism was artificially induced by using a glass capillary; real-time images of water refilling dynamics were consecutively captured at a frame rate of 50 f.p.s. Key Results Water supply in the radial direction initiates droplet formation on the wall of embolized xylem vessels. Each droplet grows into a water column; this phenomenon shows translation motion or continuous increase in water column volume. In some instances, water columns merge and form one large water column. Water refilling in the radial direction causes rapid recovery from embolism in several minutes. The average water refilling velocity is approx. 1 μm s−1. Conclusions Non-destructive visualization of embolized xylem vessels demonstrates rapid water refilling and gas bubble removal as key elements of embolism repair in a herbaceous monocot species. The refilling kinetics provides new insights into the dynamic mechanism of water refilling phenomena. PMID:27539601

Dissolved atmospheric gas in xylem sap measured with membrane inlet mass spectrometry.

PubMed

Schenk, H Jochen; Espino, Susana; Visser, Ate; Esser, Bradley K

2016-04-01

A new method is described for measuring dissolved gas concentrations in small volumes of xylem sap using membrane inlet mass spectrometry. The technique can be used to determine concentrations of atmospheric gases, such as argon, as reported here, or for any dissolved gases and their isotopes for a variety of applications, such as rapid detection of trace gases from groundwater only hours after they were taken up by trees and rooting depth estimation. Atmospheric gas content in xylem sap directly affects the conditions and mechanisms that allow for gas removal from xylem embolisms, because gas can dissolve into saturated or supersaturated sap only under gas pressure that is above atmospheric pressure. The method was tested for red trumpet vine, Distictis buccinatoria (Bignoniaceae), by measuring atmospheric gas concentrations in sap collected at times of minimum and maximum daily temperature and during temperature increase and decline. Mean argon concentration in xylem sap did not differ significantly from saturation levels for the temperature and pressure conditions at any time of collection, but more than 40% of all samples were supersaturated, especially during the warm parts of day. There was no significant diurnal pattern, due to high variability between samples. © 2015 John Wiley & Sons Ltd.

Water Transport Properties of the Grape Pedicel during Fruit Development: Insights into Xylem Anatomy and Function Using Microtomography.

PubMed

Knipfer, Thorsten; Fei, Jiong; Gambetta, Gregory A; McElrone, Andrew J; Shackel, Kenneth A; Matthews, Mark A

2015-08-01

Xylem flow of water into fruits declines during fruit development, and the literature indicates a corresponding increase in hydraulic resistance in the pedicel. However, it is unknown how pedicel hydraulics change developmentally in relation to xylem anatomy and function. In this study on grape (Vitis vinifera), we determined pedicel hydraulic conductivity (kh) from pressure-flow relationships using hydrostatic and osmotic forces and investigated xylem anatomy and function using fluorescent light microscopy and x-ray computed microtomography. Hydrostatic kh (xylem pathway) was consistently 4 orders of magnitude greater than osmotic kh (intracellular pathway), but both declined before veraison by approximately 40% and substantially over fruit development. Hydrostatic kh declined most gradually for low (less than 0.08 MPa) pressures and for water inflow and outflow conditions. Specific kh (per xylem area) decreased in a similar fashion to kh despite substantial increases in xylem area. X-ray computed microtomography images provided direct evidence that losses in pedicel kh were associated with blockages in vessel elements, whereas air embolisms were negligible. However, vessel elements were interconnected and some remained continuous postveraison, suggesting that across the grape pedicel, a xylem pathway of reduced kh remains functional late into berry ripening. © 2015 American Society of Plant Biologists. All Rights Reserved.

Characteristics of ultrasonic acoustic emissions from walnut branches during freeze-thaw-induced embolism formation.

PubMed

Kasuga, Jun; Charrier, Guillaume; Uemura, Matsuo; Améglio, Thierry

2015-04-01

Ultrasonic acoustic emission (UAE) methods have been applied for the detection of freeze-thaw-induced embolism formation in water conduits of tree species. Until now, however, the exact source(s) of UAE has not been identified especially in angiosperm species, in which xylem tissues are composed of diverse types of cells. In this study, UAE was recorded from excised branches of walnut (Juglans regia cv. Franquette) during freeze-thaw cycles, and attempts were made to characterize UAEs generated by cavitation events leading to embolism formation according to their properties. During freeze-thaw cycles, a large number of UAEs were generated from the sample segments. However, the cumulative numbers of total UAE during freeze-thawing were not correlated with the percentage loss of hydraulic conductivity after thawing, suggesting that the sources of UAE were not only cavitation leading to embolism formation in vessels. Among the UAEs, cumulative numbers of UAEs with absolute energy >10.0 fJ strongly correlated with the increase in percentage loss of hydraulic conductivity. The high absolute energy of the UAEs might reflect the formation of large bubbles in the large lumen of vessels. Therefore, UAEs generated by cavitation events in vessels during freeze-thawing might be distinguished from other signals according to their magnitudes of absolute energy. On the other hand, the freezing of xylem parenchyma cells was followed by a certain number of UAEs. These results indicate the possibility that UAE methods can be applied to the detection of both freeze-thaw-induced embolism and supercooling breakdown in parenchyma cells in xylem. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Effects of HIFU induced cavitation on flooded lung parenchyma.

PubMed

Wolfram, Frank; Dietrich, Georg; Boltze, Carsten; Jenderka, Klaus Vitold; Lesser, Thomas Günther

2017-01-01

High intensity focused ultrasound (HIFU) has gained clinical interest as a non-invasive local tumour therapy in many organs. In addition, it has been shown that lung cancer can be targeted by HIFU using One-Lung Flooding (OLF). OLF generates a gas free saline-lung compound in one lung wing and therefore acoustic access to central lung tumours. It can be assumed that lung parenchyma is exposed to ultrasound intensities in the pre-focal path and in cases of misguiding. If so, cavitation might be induced in the saline fraction of flooded lung and cause tissue damage. Therefore this study was aimed to determine the thresholds of HIFU induced cavitation and tissue erosion in flooded lung. Resected human lung lobes were flooded ex-vivo. HIFU (1,1 MHz) was targeted under sonographic guidance into flooded lung parenchyma. Cavitation events were counted using subharmonic passive cavitation detection (PCD). B-Mode imaging was used to detect cavitation and erosion sonographically. Tissue samples out of the focal zone were analysed histologically. In flooded lung, a PCD and a sonographic cavitation detection threshold of 625  Wcm - 2 ( p r  = 4, 3  MPa ) and 3.600  Wcm - 2 ( p r  = 8, 3  MPa ) was found. Cavitation in flooded lung appears as blurred hyperechoic focal region, which enhances echogenity with insonation time. Lung parenchyma erosion was detected at intensities above 7.200  Wcm - 2 ( p r  = 10, 9  MPa ). Cavitation occurs in flooded lung parenchyma, which can be detected passively and by B-Mode imaging. Focal intensities required for lung tumour ablation are below levels where erosive events occur. Therefore focal cavitation events can be monitored and potential risk from tissue erosion in flooded lung avoided.

Macrocystic lymphatic malformation in the pulmonary parenchyma.

PubMed

Schulman, Joshua M; Christison-Lagay, Emily R; Kozakewich, Harry P W; Boiselle, Phillip M; Burrows, Patricia E; Fox, Victor L; Fishman, Steven J

2009-05-01

We present a young girl with a diffuse, macrocystic lymphatic malformation with associated venous dilation involving the left lower pulmonary lobe and mediastinum. Recurrent hemoptysis necessitated left lower lobectomy. This is the first reported case of a macrocystic lymphatic lesion with venous anomalies located within the parenchyma of the lung.

Proteomics approach to identify unique xylem sap proteins in Pierce's disease-tolerant Vitis species.

PubMed

Basha, Sheikh M; Mazhar, Hifza; Vasanthaiah, Hemanth K N

2010-03-01

Pierce's disease (PD) is a destructive bacterial disease of grapes caused by Xylella fastidiosa which is xylem-confined. The tolerance level to this disease varies among Vitis species. Our research was aimed at identifying unique xylem sap proteins present in PD-tolerant Vitis species. The results showed wide variation in the xylem sap protein composition, where a set of polypeptides with pI between 4.5 and 4.7 and M(r) of 31 kDa were present in abundant amount in muscadine (Vitis rotundifolia, PD-tolerant), in reduced levels in Florida hybrid bunch (Vitis spp., PD-tolerant) and absent in bunch grapes (Vitis vinifera, PD-susceptible). Liquid chromatography/mass spectrometry/mass spectrometry analysis of these proteins revealed their similarity to beta-1, 3-glucanase, peroxidase, and a subunit of oxygen-evolving enhancer protein 1, which are known to play role in defense and oxygen generation. In addition, the amount of free amino acids and soluble sugars was found to be significantly lower in xylem sap of muscadine genotypes compared to V. vinifera genotypes, indicating that the higher nutritional value of bunch grape sap may be more suitable for Xylella growth. These data suggest that the presence of these unique proteins in xylem sap is vital for PD tolerance in muscadine and Florida hybrid bunch grapes.

Xylem resistance to embolism: presenting a simple diagnostic test for the open vessel artefact.

PubMed

Torres-Ruiz, José M; Cochard, Hervé; Choat, Brendan; Jansen, Steven; López, Rosana; Tomášková, Ivana; Padilla-Díaz, Carmen M; Badel, Eric; Burlett, Regis; King, Andrew; Lenoir, Nicolas; Martin-StPaul, Nicolas K; Delzon, Sylvain

2017-07-01

Xylem vulnerability to embolism represents an essential trait for the evaluation of the impact of hydraulics in plant function and ecology. The standard centrifuge technique is widely used for the construction of vulnerability curves, although its accuracy when applied to species with long vessels remains under debate. We developed a simple diagnostic test to determine whether the open-vessel artefact influences centrifuge estimates of embolism resistance. Xylem samples from three species with differing vessel lengths were exposed to less negative xylem pressures via centrifugation than the minimum pressure the sample had previously experienced. Additional calibration was obtained from non-invasive measurement of embolism on intact olive plants by X-ray microtomography. Results showed artefactual decreases in hydraulic conductance (k) for samples with open vessels when exposed to a less negative xylem pressure than the minimum pressure they had previously experienced. X-Ray microtomography indicated that most of the embolism formation in olive occurs at xylem pressures below -4.0 MPa, reaching 50% loss of hydraulic conductivity at -5.3 MPa. The artefactual reductions in k induced by centrifugation underestimate embolism resistance data of species with long vessels. A simple test is suggested to avoid this open vessel artefact and to ensure the reliability of this technique in future studies. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Surface tension phenomena in the xylem sap of three diffuse porous temperate tree species

Treesearch

K. K. Christensen-Dalsgaard; M. T. Tyree; P. G. Mussone

2011-01-01

In plant physiology models involving bubble nucleation, expansion or elimination, it is typically assumed that the surface tension of xylem sap is equal to that of pure water, though this has never been tested. In this study we collected xylem sap from branches of the tree species Populus tremuloides, Betula papyrifera and Sorbus...

How does climate influence xylem morphogenesis over the growing season? Insights from long-term intra-ring anatomy in Picea abies

PubMed Central

Fonti, Patrick; von Arx, Georg; Carrer, Marco

2017-01-01

Background and Aims During the growing season, the cambium of conifer trees produces successive rows of xylem cells, the tracheids, that sequentially pass through the phases of enlargement and secondary wall thickening before dying and becoming functional. Climate variability can strongly influence the kinetics of morphogenetic processes, eventually affecting tracheid shape and size. This study investigates xylem anatomical structure in the stem of Picea abies to retrospectively infer how, in the long term, climate affects the processes of cell enlargement and wall thickening. Methods Tracheid anatomical traits related to the phases of enlargement (diameter) and wall thickening (wall thickness) were innovatively inspected at the intra-ring level on 87-year-long tree-ring series in Picea abies trees along a 900 m elevation gradient in the Italian Alps. Anatomical traits in ten successive tree-ring sectors were related to daily temperature and precipitation data using running correlations. Key Results Close to the altitudinal tree limit, low early-summer temperature negatively affected cell enlargement. At lower elevation, water availability in early summer was positively related to cell diameter. The timing of these relationships shifted forward by about 20 (high elevation) to 40 (low elevation) d from the first to the last tracheids in the ring. Cell wall thickening was affected by climate in a different period in the season. In particular, wall thickness of late-formed tracheids was strongly positively related to August–September temperature at high elevation. Conclusions Morphogenesis of tracheids sequentially formed in the growing season is influenced by climate conditions in successive periods. The distinct climate impacts on cell enlargement and wall thickening indicate that different morphogenetic mechanisms are responsible for different tracheid traits. Our approach of long-term and high-resolution analysis of xylem anatomy can support and extend short

How does climate influence xylem morphogenesis over the growing season? Insights from long-term intra-ring anatomy in Picea abies.

PubMed

Castagneri, Daniele; Fonti, Patrick; von Arx, Georg; Carrer, Marco

2017-04-01

During the growing season, the cambium of conifer trees produces successive rows of xylem cells, the tracheids, that sequentially pass through the phases of enlargement and secondary wall thickening before dying and becoming functional. Climate variability can strongly influence the kinetics of morphogenetic processes, eventually affecting tracheid shape and size. This study investigates xylem anatomical structure in the stem of Picea abies to retrospectively infer how, in the long term, climate affects the processes of cell enlargement and wall thickening. Tracheid anatomical traits related to the phases of enlargement (diameter) and wall thickening (wall thickness) were innovatively inspected at the intra-ring level on 87-year-long tree-ring series in Picea abies trees along a 900 m elevation gradient in the Italian Alps. Anatomical traits in ten successive tree-ring sectors were related to daily temperature and precipitation data using running correlations. Close to the altitudinal tree limit, low early-summer temperature negatively affected cell enlargement. At lower elevation, water availability in early summer was positively related to cell diameter. The timing of these relationships shifted forward by about 20 (high elevation) to 40 (low elevation) d from the first to the last tracheids in the ring. Cell wall thickening was affected by climate in a different period in the season. In particular, wall thickness of late-formed tracheids was strongly positively related to August-September temperature at high elevation. Morphogenesis of tracheids sequentially formed in the growing season is influenced by climate conditions in successive periods. The distinct climate impacts on cell enlargement and wall thickening indicate that different morphogenetic mechanisms are responsible for different tracheid traits. Our approach of long-term and high-resolution analysis of xylem anatomy can support and extend short-term xylogenesis observations, and increase our

Effect of long-term forest fertilization on Scots pine xylem quality and wood borer performance.

PubMed

Heijari, Juha; Nerg, Anne-Marja; Kainulainen, Pirjo; Noldt, Uwe; Levula, Teuvo; Raitio, Hannu; Holopainen, Jarmo K

2008-01-01

We tested whether changes in long-term nutrient availability would affect the xylem quality and characteristics of Scots pine trees as a food source for the larvae of the xylophagous wood borer Hylotrupes bajulus L. (Cerambycidae). We looked for an effect of host plant growth and xylem structural traits on H. bajulus larval performance, and looked for delayed effects of long-term forest fertilization on xylem chemical quality. In general, larval performance was dependent on larval developmental stage. However, the growth of larvae also varied with host plant quality (increases in the concentration of nitrogen and carbon-based secondary compounds of xylem were correlated with a decrease in the larval growth rate). The greater annual growth of trees reduced tracheid length and correlated positively with second-instar H. bajulus growth rate. This is consistent with the hypothesis that intrinsic growth patterns of host plants influence the development of the xylophagous wood borer H. bajulus.

Coordination and transport of water and carbohydrates in the coupled soil-root-xylem-phloem leaf system

NASA Astrophysics Data System (ADS)

Katul, Gabriel; Huang, Cheng-Wei

2017-04-01

In response to varying environmental conditions, stomatal pores act as biological valves that dynamically adjust their size thereby determining the rate of CO2 assimilation and water loss (i.e., transpiration) to the atmosphere. Although the significance of this biotic control on gas exchange is rarely disputed, representing parsimoniously all the underlying mechanisms responsible for stomatal kinetics remain a subject of some debate. It has been conjectured that stomatal control in seed plants (i.e., angiosperm and gymnosperm) represents a compromise between biochemical demand for CO2 and prevention of excessive water loss. This view has been amended at the whole-plant level, where xylem hydraulics and sucrose transport efficiency in phloem appear to impose additional constraints on gas exchange. If such additional constraints impact stomatal opening and closure, then seed plants may have evolved coordinated photosynthetic-hydraulic-sugar transporting machinery that confers some competitive advantages in fluctuating environmental conditions. Thus, a stomatal optimization model that explicitly considers xylem hydraulics and maximum sucrose transport is developed to explore this coordination in the leaf-xylem-phloem system. The model is then applied to progressive drought conditions. The main findings from the model calculations are that (1) the predicted stomatal conductance from the conventional stomatal optimization theory at the leaf and the newly proposed models converge, suggesting a tight coordination in the leaf-xylem-phloem system; (2) stomatal control is mainly limited by the water supply function of the soil-xylem hydraulic system especially when the water flux through the transpiration stream is significantly larger than water exchange between xylem and phloem; (3) thus, xylem limitation imposed on the supply function can be used to differentiate species with different water use strategy across the spectrum of isohydric to anisohydric behavior.

Relating xylem cavitation to gas exchange in cotton

USDA-ARS?s Scientific Manuscript database

Acoustic emissions (AEs) from xylem cavitation events are characteristic of transpiration processes. Though a body of work using AE exists with a large number of species, cotton and other agronomically important crops have either not been investigated, or limited information exists. The objective of...

Xylella fastidiosa infection of grapevines affects xylem levels of phenolic compounds and pathogenesis-related proteins

USDA-ARS?s Scientific Manuscript database

Pierce’s disease (PD), caused by the xylem-dwelling pathogen Xylella fastidiosa (X.f.), is a serious threat to grape production. The effects of X.f. infection six months post-inoculation on defense-associated proteins and phenolic compounds found in xylem sap and tissue were evaluated. Defense-assoc...

Water Transport Properties of the Grape Pedicel during Fruit Development: Insights into Xylem Anatomy and Function Using Microtomography1[OPEN

PubMed Central

Fei, Jiong; McElrone, Andrew J.; Shackel, Kenneth A.; Matthews, Mark A.

2015-01-01

Xylem flow of water into fruits declines during fruit development, and the literature indicates a corresponding increase in hydraulic resistance in the pedicel. However, it is unknown how pedicel hydraulics change developmentally in relation to xylem anatomy and function. In this study on grape (Vitis vinifera), we determined pedicel hydraulic conductivity (kh) from pressure-flow relationships using hydrostatic and osmotic forces and investigated xylem anatomy and function using fluorescent light microscopy and x-ray computed microtomography. Hydrostatic kh (xylem pathway) was consistently 4 orders of magnitude greater than osmotic kh (intracellular pathway), but both declined before veraison by approximately 40% and substantially over fruit development. Hydrostatic kh declined most gradually for low (less than 0.08 MPa) pressures and for water inflow and outflow conditions. Specific kh (per xylem area) decreased in a similar fashion to kh despite substantial increases in xylem area. X-ray computed microtomography images provided direct evidence that losses in pedicel kh were associated with blockages in vessel elements, whereas air embolisms were negligible. However, vessel elements were interconnected and some remained continuous postveraison, suggesting that across the grape pedicel, a xylem pathway of reduced kh remains functional late into berry ripening. PMID:26077763

Dynamic control of osmolality and ionic composition of the xylem sap in two mangrove species.

PubMed

López-Portillo, Jorge; Ewers, Frank W; Méndez-Alonzo, Rodrigo; Paredes López, Claudia L; Angeles, Guillermo; Alarcón Jiménez, Ana Luisa; Lara-Domínguez, Ana Laura; Torres Barrera, María Del Carmen

2014-06-01

• Premise of the study: Xylem sap osmolality and salinity is a critical unresolved issue in plant function with impacts on transport efficiency, pressure gradients, and living cell turgor pressure, especially for halophytes such as mangrove trees.• Methods: We collected successive xylem vessel sap samples from stems and shoots of Avicennia germinans and Laguncularia racemosa using vacuum and pressure extraction and measured their osmolality. Following a series of extractions with the pressure chamber, we depressurized the shoot and pressurized again after various equilibration periods (minutes to hours) to test for dynamic control of osmolality. Transpiration and final sap osmolality were measured in shoots perfused with deionized water or different seawater dilutions.• Key results: For both species, the sap osmolality values of consecutive samples collected by vacuum extraction were stable and matched those of the initial samples extracted with the pressure chamber. Further extraction of samples with the pressure chamber decreased sap osmolality, suggesting reverse osmosis occurred. However, sap osmolalities increased when longer equilibration periods after sap extraction were allowed. Analysis of expressed sap with HPLC indicated a 1:1 relation between measured osmolality and the osmolality of the inorganic ions in the sap (mainly Na + , K + , and Cl - ), suggesting no contamination by organic compounds. In stems perfused with deionized water, the sap osmolality increased to mimic the native sap osmolality.• Conclusions: Xylem sap osmolality and ionic contents are dynamically adjusted by mangroves and may help modulate turgor pressure, hydraulic conductivity, and water potential, thus being important for mangrove physiology, survival, and distribution. © 2014 Botanical Society of America, Inc.

A Segmentation Method for Lung Parenchyma Image Sequences Based on Superpixels and a Self-Generating Neural Forest

PubMed Central

Liao, Xiaolei; Zhao, Juanjuan; Jiao, Cheng; Lei, Lei; Qiang, Yan; Cui, Qiang

2016-01-01

Background Lung parenchyma segmentation is often performed as an important pre-processing step in the computer-aided diagnosis of lung nodules based on CT image sequences. However, existing lung parenchyma image segmentation methods cannot fully segment all lung parenchyma images and have a slow processing speed, particularly for images in the top and bottom of the lung and the images that contain lung nodules. Method Our proposed method first uses the position of the lung parenchyma image features to obtain lung parenchyma ROI image sequences. A gradient and sequential linear iterative clustering algorithm (GSLIC) for sequence image segmentation is then proposed to segment the ROI image sequences and obtain superpixel samples. The SGNF, which is optimized by a genetic algorithm (GA), is then utilized for superpixel clustering. Finally, the grey and geometric features of the superpixel samples are used to identify and segment all of the lung parenchyma image sequences. Results Our proposed method achieves higher segmentation precision and greater accuracy in less time. It has an average processing time of 42.21 seconds for each dataset and an average volume pixel overlap ratio of 92.22 ± 4.02% for four types of lung parenchyma image sequences. PMID:27532214

Kidney-induced cardiac allograft tolerance in miniature swine is dependent on MHC-matching of donor cardiac and renal parenchyma.

PubMed

Madariaga, M L; Michel, S G; La Muraglia, G M; Sekijima, M; Villani, V; Leonard, D A; Powell, H J; Kurtz, J M; Farkash, E A; Colvin, R B; Allan, J S; Cetrulo, C L; Huang, C A; Sachs, D H; Yamada, K; Madsen, J C

2015-06-01

Kidney allografts possess the ability to enable a short course of immunosuppression to induce tolerance of themselves and of cardiac allografts across a full-MHC barrier in miniature swine. However, the renal element(s) responsible for kidney-induced cardiac allograft tolerance (KICAT) are unknown. Here we investigated whether MHC disparities between parenchyma versus hematopoietic-derived "passenger" cells of the heart and kidney allografts affected KICAT. Heart and kidney allografts were co-transplanted into MHC-mismatched recipients treated with high-dose tacrolimus for 12 days. Group 1 animals (n = 3) received kidney and heart allografts fully MHC-mismatched to each other and to the recipient. Group 2 animals (n = 3) received kidney and heart allografts MHC-matched to each other but MHC-mismatched to the recipient. Group 3 animals (n = 3) received chimeric kidney allografts whose parenchyma was MHC-mismatched to the donor heart. Group 4 animals (n = 3) received chimeric kidney allografts whose passenger leukocytes were MHC-mismatched to the donor heart. Five of six heart allografts in Groups 1 and 3 rejected <40 days. In contrast, heart allografts in Groups 2 and 4 survived >150 days without rejection (p < 0.05). These data demonstrate that KICAT requires MHC-matching between kidney allograft parenchyma and heart allografts, suggesting that cells intrinsic to the kidney enable cardiac allograft tolerance. © Copyright 2015 The American Society of Transplantation and the American Society of Transplant Surgeons.

Characterization of the Lung Parenchyma Using Ultrasound Multiple Scattering.

PubMed

Mohanty, Kaustav; Blackwell, John; Egan, Thomas; Muller, Marie

2017-05-01

The purpose of the study described here was to showcase the application of ultrasound to quantitative characterization of the micro-architecture of the lung parenchyma to predict the extent of pulmonary edema. The lung parenchyma is a highly complex and diffusive medium for which ultrasound techniques have remained qualitative. The approach presented here is based on ultrasound multiple scattering and exploits the complexity of ultrasound propagation in the lung structure. The experimental setup consisted of a linear transducer array with an 8-MHz central frequency placed in contact with the lung surface. The diffusion constant D and transport mean free path L* of the lung parenchyma were estimated by separating the incoherent and coherent intensities in the near field and measuring the growth of the incoherent diffusive halo over time. Significant differences were observed between the L* values obtained in healthy and edematous rat lungs in vivo. In the control rat lung, L* was found to be 332 μm (±48.8 μm), whereas in the edematous lung, it was 1040 μm (±90 μm). The reproducibility of the measurements of L* and D was tested in vivo and in phantoms made of melamine sponge with varying air volume fractions. Two-dimensional finite difference time domain numerical simulations were carried out on rabbit lung histology images with varying degrees of lung collapse. Significant correlations were observed between air volume fraction and L* in simulation (r = -0.9542, p < 0.0117) and sponge phantom (r = -0.9932, p < 0.0068) experiments. Ex vivo measurements of a rat lung in which edema was simulated by adding phosphate-buffered saline revealed a linear relationship between the fluid volume fraction and L*. These results illustrate the potential of methods based on ultrasound multiple scattering for the quantitative characterization of the lung parenchyma. Copyright © 2017 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc

Xylella fastidiosa infection of grapevines affects host secondary metabolite and defense-related protein levels within xylem

USDA-ARS?s Scientific Manuscript database

Pierce’s disease of grapevine is a serious threat to grape production and is caused by the xylem-dwelling bacterial pathogen Xylella fastidiosa. Microscopy studies have documented morphological changes to grapevine xylem due to infection by X. fastidiosa. Comparatively, less is known about the bi...

Salivary enzymes are injected into xylem by the glassy-winged sharpshooter, a vector of Xylella fastidiosa

USDA-ARS?s Scientific Manuscript database

Certain hemipteran insects such as the glassy-winged sharpshooter, Homalodisca vitripennis, subsist entirely on xylem fluid, notwithstanding the poor nutrition of such food. Among many adaptations enabling xylem-feeding are aspects of the insect’s salivation that may also allow these insects to tra...

A closed-form solution for steady-state coupled phloem/xylem flow using the Lambert-W function.

PubMed

Hall, A J; Minchin, P E H

2013-12-01

A closed-form solution for steady-state coupled phloem/xylem flow is presented. This incorporates the basic Münch flow model of phloem transport, the cohesion model of xylem flow, and local variation in the xylem water potential and lateral water flow along the transport pathway. Use of the Lambert-W function allows this solution to be obtained under much more general and realistic conditions than has previously been possible. Variation in phloem resistance (i.e. viscosity) with solute concentration, and deviations from the Van't Hoff expression for osmotic potential are included. It is shown that the model predictions match those of the equilibrium solution of a numerical time-dependent model based upon the same mechanistic assumptions. The effect of xylem flow upon phloem flow can readily be calculated, which has not been possible in any previous analytical model. It is also shown how this new analytical solution can handle multiple sources and sinks within a complex architecture, and can describe competition between sinks. The model provides new insights into Münch flow by explicitly including interactions with xylem flow and water potential in the closed-form solution, and is expected to be useful as a component part of larger numerical models of entire plants. © 2013 John Wiley & Sons Ltd.

Plant fluid proteomics: Delving into the xylem sap, phloem sap and apoplastic fluid proteomes.

PubMed

Rodríguez-Celma, Jorge; Ceballos-Laita, Laura; Grusak, Michael A; Abadía, Javier; López-Millán, Ana-Flor

2016-08-01

The phloem sap, xylem sap and apoplastic fluid play key roles in long and short distance transport of signals and nutrients, and act as a barrier against local and systemic pathogen infection. Among other components, these plant fluids contain proteins which are likely to be important players in their functionalities. However, detailed information about their proteomes is only starting to arise due to the difficulties inherent to the collection methods. This review compiles the proteomic information available to date in these three plant fluids, and compares the proteomes obtained in different plant species in order to shed light into conserved functions in each plant fluid. Inter-species comparisons indicate that all these fluids contain the protein machinery for self-maintenance and defense, including proteins related to cell wall metabolism, pathogen defense, proteolysis, and redox response. These analyses also revealed that proteins may play more relevant roles in signaling in the phloem sap and apoplastic fluid than in the xylem sap. A comparison of the proteomes of the three fluids indicates that although functional categories are somewhat similar, proteins involved are likely to be fluid-specific, except for a small group of proteins present in the three fluids, which may have a universal role, especially in cell wall maintenance and defense. This article is part of a Special Issue entitled: Plant Proteomics--a bridge between fundamental processes and crop production, edited by Dr. Hans-Peter Mock. Copyright © 2016 Elsevier B.V. All rights reserved.

Vulnerability of Xylem Vessels to Cavitation in Sugar Maple. Scaling from Individual Vessels to Whole Branches1

PubMed Central

Melcher, Peter J.; Zwieniecki, Maciej A.; Holbrook, N. Michele

2003-01-01

The relation between xylem vessel age and vulnerability to cavitation of sugar maple (Acer saccharum Marsh.) was quantified by measuring the pressure required to force air across bordered pit membranes separating individual xylem vessels. We found that the bordered pit membranes of vessels located in current year xylem could withstand greater applied gas pressures (3.8 MPa) compared with bordered pit membranes in vessels located in older annular rings (2.0 MPa). A longitudinal transect along 6-year-old branches indicated that the pressure required to push gas across bordered pit membranes of current year xylem did not vary with distance from the growing tip. To understand the contribution of age-related changes in vulnerability to the overall resistance to cavitation, we combined data on the pressure thresholds of individual xylem vessels with measurements of the relative flow rate through each annual ring. The annual ring of the current year contributed only 16% of the total flow measured on 10-cm-long segments cut from 6-year-old branches, but it contributed more than 70% of the total flow when measured through 6-year-old branches to the point of leaf attachment. The vulnerability curve calculated using relative flow rates measured on branch segments were similar to vulnerability curves measured on 6-year-old branches (pressure that reduces hydraulic conductance by 50% = 1.6–2.4 MPa), whereas the vulnerability curve calculated using relative flow rates measured on 6-year-old branches were similar to ones measured on the extension growth of the current year (pressure that reduces hydraulic conductance by 50% = 3.8 MPa). These data suggest that, in sugar maple, the xylem of the current year can withstand larger xylem tensions than older wood and dominates water delivery to leaves. PMID:12692336

Effects of Xylem-Sap Composition on Glassy-Winged Sharpshooter (Hemiptera: Cicadellidae) Egg Maturation on High- and Low-Quality Host Plants.

PubMed

Sisterson, Mark S; Wallis, Christopher M; Stenger, Drake C

2017-04-01

Glassy-winged sharpshooters must feed as adults to produce mature eggs. Cowpea and sunflower are both readily accepted by the glassy-winged sharpshooter for feeding, but egg production on sunflower was reported to be lower than egg production on cowpea. To better understand the role of adult diet in egg production, effects of xylem-sap chemistry on glassy-winged sharpshooter egg maturation was compared for females confined to cowpea and sunflower. Females confined to cowpea consumed more xylem-sap than females held on sunflower. In response, females held on cowpea produced more eggs, had heavier bodies, and greater lipid content than females held on sunflower. Analysis of cowpea and sunflower xylem-sap found that 17 of 19 amino acids were more concentrated in cowpea xylem-sap than in sunflower xylem-sap. Thus, decreased consumption of sunflower xylem-sap was likely owing to perceived lower quality, with decreased egg production owing to a combination of decreased feeding and lower return per unit volume of xylem-sap consumed. Examination of pairwise correlation coefficients among amino acids indicated that concentrations of several amino acids within a plant species were correlated. Principal component analyses identified latent variables describing amino acid composition of xylem-sap. For females held on cowpea, egg maturation was affected by test date, volume of excreta produced, and principal components describing amino acid composition of xylem-sap. Principal component analyses aided in identifying amino acids that were positively or negatively associated with egg production, although determining causality with respect to key nutritional requirements for glassy-winged sharpshooter egg production will require additional testing. Published by Oxford University Press on behalf of Entomological Society of America 2017. This work is written by US Government employees and is in the public domain in the US.

Hydrolase treatments help unravel the function of intervessel pits in xylem hydraulics.

PubMed

Dusotoit-Coucaud, Anaïs; Brunel, Nicole; Tixier, Aude; Cochard, Hervé; Herbette, Stéphane

2014-03-01

Intervessel pits are structures that play a key role in the efficiency and safety functions of xylem hydraulics. However, little is known about the components of the pit membrane (PM) and their role in hydraulic functions, especially in resistance to cavitation. We tested the effect of commercial chemicals including a cellulase, a hemicellulase, a pectolyase, a proteinase and DTT on xylem hydraulic properties: vulnerability to cavitation (VC) and conductance. The effects were tested on branch segments from Fagus sylvatica (where the effects on pit structure were analyzed using TEM) and Populus tremula. Cellulose hydrolysis resulted in a sharp increase in VC and a significant increase in conductance, related to complete breakdown of the PM. Pectin hydrolysis also induced a sharp increase in VC but with no effect on conductance or pit structure observable by TEM. The other treatments with hemicellulase, proteinase or DTT showed no effect. This study brings evidence that cellulose and pectins are critical components underpinning VC, and that PM components may play distinct roles in the xylem hydraulic safety and efficiency. © 2013 Scandinavian Plant Physiology Society.

X-ray CT and histological imaging of xylem vessels organization in Mimosa pudica.

PubMed

Lee, Sang Joon; Song, Kahye; Kim, Hae Koo; Park, Joonghyuk

2013-11-01

Mimosa pudica has three distinct specialized organs, namely, pulvinus, secondary pulvinus, and pulvinule, which are respectively controlling the movements of petioles, leaflets, and pinna in response to external stimuli. Water flow is a key factor for such movements, but detailed studies on the organization of the vascular system for water transport in these organs have not been published yet. In this study, organizations of the xylem vessels and morphological features of the pulvinus, the secondary pulvinus, and the pulvinule were experimentally investigated by X-ray computed tomography and histological technique. Results showed that the xylem vessels were circularly distributed in the specialized motile organs and reorganized into distinct vascular bundles at the extremities. The number and the total cross-sectional area of the xylem vessels were increased inside the specialized motile organs. Morphological characteristics obtained in this study provided new insight to understand the functions of the vascular networks in the dynamic movements of M. pudica. Copyright © 2013 Wiley Periodicals, Inc.

Ear Rachis Xylem Occlusion and Associated Loss in Hydraulic Conductance Coincide with the End of Grain Filling for Wheat

PubMed Central

Neghliz, Hayet; Cochard, Hervé; Brunel, Nicole; Martre, Pierre

2016-01-01

Seed dehydration is the normal terminal event in the development of orthodox seeds and is physiologically related to the cessation of grain dry mass accumulation and crop grain yield. For a better understanding of grain dehydration, we evaluated the hypothesis that hydraulic conductance of the ear decreases during the latter stages of development and that this decrease results from disruption or occlusion of xylem conduits. Whole ear, rachis, and stem nodes hydraulic conductance and percentage loss of xylem conductivity were measured from flowering to harvest-ripeness on bread wheat (Triticum aestivum L.) cv. Récital grown under controlled environments. Flag leaf transpiration, stomatal conductance, chlorophyll content and grain and ear water potentials were also measured during grain development. We show that grain dehydration was not related with whole plant physiology and leaf senescence, but closely correlated with the hydraulic properties of the xylem conduits irrigating the grains. Indeed, there was a substantial decrease in rachis hydraulic conductance at the onset of the grain dehydration phase. This hydraulic impairment was not caused by the presence of air embolism in xylem conduits of the stem internodes or rachis but by the occlusion of the xylem lumens by polysaccharides (pectins and callose). Our results demonstrate that xylem hydraulics plays a key role during grain maturation. PMID:27446150

Physical analysis of the process of cavitation in xylem sap.

PubMed

Shen, Fanyi; Gao, Rongfu; Liu, Wenji; Zhang, Wenjie

2002-06-01

Recent studies have confirmed that cavitation in xylem is caused by air bubbles. We analyzed expansion of a preexistent bubble adhering to a crack in a conduit wall and a bubble formed by the passage of air through a pore of a pit membrane, a process known as air seeding. We consider that there are two equilibrium states for a very small air bubble in the xylem: one is temporarily stable with a bubble radius r1 at point s1 on the curve P(r) relating pressure within the bubble (P) with bubble radius (r); the other is unstable with a bubble radius r2 at point s2 on Pr (where r1 < r2). In each equilibrium state, the bubble collapse pressure (2sigma/r, where sigma is surface tension of water) is balanced by the pressure difference across its surface. In the case of a bubble from a crack in a conduit wall, which is initially at point s1, expansion will occur steadily as water potential decreases. The bubble will burst only if the xylem pressure drops below a threshold value. A formula giving the threshold pressure for bubble bursting is proposed. In the case of an air seed entering a xylem conduit through a pore in a pit membrane, its initial radius may be r2 (i.e., the radius of the pore by which the air seed entered the vessel) at point s2 on Pr. Because the bubble is in an unstable equilibrium when entering the conduit, it can either expand or contract to point s1. As water vaporizes into the air bubble at s2, P rises until it exceeds the gas pressure that keeps the bubble in equilibrium, at which point the bubble will burst and induce a cavitation event in accordance with the air-seeding hypothesis. However, other possible perturbations could make the air-seeded bubble contract to s1, in which case the bubble will burst at a threshold pressure proposed for a bubble expanding from a crack in a conduit wall. For this reason some cavitation events may take place at a xylem threshold pressure (Pl'*) other than that determined by the formula, Plp'* = -2sigma/rp, proposed

Functional adjustments of xylem anatomy to climatic variability: insights from long-term Ilex aquifolium tree-ring series.

PubMed

Rita, Angelo; Cherubini, Paolo; Leonardi, Stefano; Todaro, Luigi; Borghetti, Marco

2015-08-01

The present study assessed the effects of climatic conditions on radial growth and functional anatomical traits, including ring width, vessel size, vessel frequency and derived variables, i.e., potential hydraulic conductivity and xylem vulnerability to cavitation in Ilex aquifolium L. trees using long-term tree-ring time series obtained at two climatically contrasting sites, one mesic site in Switzerland (CH) and one drought-prone site in Italy (ITA). Relationships were explored by examining different xylem traits, and point pattern analysis was applied to investigate vessel clustering. We also used generalized additive models and bootstrap correlation functions to describe temperature and precipitation effects. Results indicated modified radial growth and xylem anatomy in trees over the last century; in particular, vessel frequency increased markedly at both sites in recent years, and all xylem traits examined, with the exception of xylem cavitation vulnerability, were higher at the CH mesic compared with the ITA drought site. A significant vessel clustering was observed at the ITA site, which could contribute to an enhanced tolerance to drought-induced embolism. Flat and negative relationships between vessel size and ring width were observed, suggesting carbon was not allocated to radial growth under conditions which favored stem water conduction. Finally, in most cases results indicated that climatic conditions influenced functional anatomical traits more substantially than tree radial growth, suggesting a crucial role of functional xylem anatomy in plant acclimation to future climatic conditions. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Performance assessment of an opto-fluidic phantom mimicking porcine liver parenchyma

NASA Astrophysics Data System (ADS)

Akl, Tony J.; King, Travis J.; Long, Ruiqi; McShane, Michael J.; Nance Ericson, M.; Wilson, Mark A.; Coté, Gerard L.

2012-07-01

An implantable, optical oxygenation and perfusion sensor to monitor liver transplants during the two-week period following the transplant procedure is currently being developed. In order to minimize the number of animal experiments required for this research, a phantom that mimics the optical, anatomical, and physiologic flow properties of liver parenchyma is being developed as well. In this work, the suitability of this phantom for liver parenchyma perfusion research was evaluated by direct comparison of phantom perfusion data with data collected from in vivo porcine studies, both using the same prototype perfusion sensor. In vitro perfusion and occlusion experiments were performed on a single-layer and on a three-layer phantom perfused with a dye solution possessing the absorption properties of oxygenated hemoglobin. While both phantoms exhibited response patterns similar to the liver parenchyma, the signal measured from the multilayer phantom was three times higher than the single layer phantom and approximately 21 percent more sensitive to in vitro changes in perfusion. Although the multilayer phantom replicated the in vivo flow patterns more closely, the data suggests that both phantoms can be used in vitro to facilitate sensor design.

Increasing atmospheric [CO2] from glacial through future levels affects drought tolerance via impacts on leaves, xylem and their integrated function

PubMed Central

Medeiros, Juliana S.; Ward, Joy K.

2013-01-01

Summary Changes in atmospheric carbon dioxide concentration ([CO2]) affect plant carbon/water trade-offs, with implications for drought tolerance. Leaf-level studies often indicate that drought tolerance may increase with rising [CO2], but integrated leaf and xylem responses are not well understood in this respect. In addition, the influence of low [CO2] of the last glacial period on drought tolerance and xylem properties is not well understood.We investigated the interactive effects of a broad range of [CO2] and plant water potentials on leaf function, xylem structure and function and the integration of leaf and xylem function in Phaseolus vulgaris.Elevated [CO2] decreased vessel implosion strength, reduced conduit specific hydraulic conductance, and compromised leaf specific xylem hydraulic conductance under moderate drought. By contrast, at glacial [CO2], transpiration was maintained under moderate drought via greater conduit specific and leaf specific hydraulic conductance in association with increased vessel implosion strength.Our study involving the integration of leaf and xylem responses suggests that increasing [CO2] does not improve drought tolerance. We show that under glacial conditions changes in leaf and xylem properties could increase drought tolerance, while under future conditions greater productivity may only occur when higher water use can be accommodated. PMID:23668237

A Novel Plasma Membrane-Anchored Protein Regulates Xylem Cell-Wall Deposition through Microtubule-Dependent Lateral Inhibition of Rho GTPase Domains.

PubMed

Sugiyama, Yuki; Wakazaki, Mayumi; Toyooka, Kiminori; Fukuda, Hiroo; Oda, Yoshihisa

2017-08-21

Spatial control of cell-wall deposition is essential for determining plant cell shape [1]. Rho-type GTPases, together with the cortical cytoskeleton, play central roles in regulating cell-wall patterning [2]. In metaxylem vessel cells, which are the major components of xylem tissues, active ROP11 Rho GTPases form oval plasma membrane domains that locally disrupt cortical microtubules, thereby directing the formation of oval pits in secondary cell walls [3-5]. However, the regulatory mechanism that determines the planar shape of active Rho of Plants (ROP) domains is still unknown. Here we show that IQD13 associates with cortical microtubules and the plasma membrane to laterally restrict the localization of ROP GTPase domains, thereby directing the formation of oval secondary cell-wall pits. Loss and overexpression of IQD13 led to the formation of abnormally round and narrow secondary cell-wall pits, respectively. Ectopically expressed IQD13 increased the presence of parallel cortical microtubules by promoting microtubule rescue. A reconstructive approach revealed that IQD13 confines the area of active ROP domains within the lattice of the cortical microtubules, causing narrow ROP domains to form. This activity required the interaction of IQD13 with the plasma membrane. These findings suggest that IQD13 positively regulates microtubule dynamics as well as their linkage to the plasma membrane, which synergistically confines the area of active ROP domains, leading to the formation of oval secondary cell-wall pits. This finding sheds light on the role of microtubule-plasma membrane linkage as a lateral fence that determines the planar shape of Rho GTPase domains. Copyright © 2017 Elsevier Ltd. All rights reserved.

Drought tolerance, xylem sap abscisic acid and stomatal conductance during soil drying: a comparison of canopy trees of three temperate deciduous angiosperms.

PubMed

Loewenstein, Nancy J.; Pallardy, Stephen G.

1998-07-01

Patterns of water relations, xylem sap abscisic acid concentration ([ABA]) and stomatal aperture were characterized and compared in drought-sensitive black walnut (Juglans nigra L.), less drought-sensitive sugar maple (Acer saccharum Marsh.) and drought-tolerant white oak (Quercus alba L.) trees co-occurring in a second-growth forest in Missouri, USA. There were strong correlations among reduction in predawn leaf water potential, increased xylem sap [ABA] and stomatal closure in all species. Stomatal conductance was more closely correlated with xylem sap ABA concentration than with ABA flux or xylem sap pH and cation concentrations. In isohydric black walnut, increased concentrations of ABA in the xylem sap appeared to be primarily of root origin, causing stomatal closure in response to soil drying. In anisohydric sugar maple and white oak, however, there were reductions in midday leaf water potential associated with stomatal closure, making it uncertain whether drought-induced xylem sap ABA was of leaf or root origin. The role of root-originated xylem sap ABA in these species as a signal to the shoot of the water status of the roots is, therefore, less certain.

The effect of xylem age on volume yield and sugar content of sugar maple sap

Treesearch

Carter B. Gibbs; Carter B. Gibbs

1969-01-01

At the Burlington, Vermont, research unit of the Northeastern Forest Experiment Station, a study was begun in 1966 in an effort to identify the portions of the xylem that produce the most sap and the sap with the highest sugar content. The study revealed that the greatest volume of sap comes from xylem that is about 35 years old, and that the sweetest sap comes from...

Wall ingrowth deposition in phloem parenchyma transfer cells in Arabidopsis: Heteroblastic variations and a potential role in pathogen defence.

PubMed

Nguyen, Suong T T; McCurdy, David W

2017-06-03

Transfer cell (TCs) develop unique wall ingrowth networks which amplify plasma membrane surface area and thus maximize nutrient transporter density at key anatomic sites for nutrient exchange within plants and their external environment. These sites fall into 4 main groups corresponding to 4 categories of trans-membrane flux: absorption/secretion of solutes from or to the external environment, and absorption/secretion of solutes from or to internal, extra-cytoplasmic compartments. Research on TC biology over recent decades has demonstrated correlations between wall ingrowth deposition in TCs and enhanced transport capacity in many major agricultural species such as pea, fava bean, cotton and maize. Consequently, there is general consensus that the existence of wall ingrowth morphology implies an augmentation in membrane transport capacity. However, this may not be entirely applicable for phloem parenchyma (PP) TCs in Arabidopsis. Our recent survey of PP TC abundance and distribution in Arabidopsis veins indicated that PP TC development reflects heteroblastic status. A consequence of this observation is the suggestion that PP TCs, or at least wall ingrowth deposition in these cells, potentially act as a physical barrier to defend access of invading pathogens to sugar-rich sieve elements rather than solely in facilitating the export of photoassimilate from collection phloem in leaves.

The Mechanism of Freezing Injury in Xylem of Winter Apple Twigs 1

PubMed Central

Quamme, H.; Weiser, C. J.; Stushnoff, C.

1973-01-01

In acclimated winter twigs of Haralson apple (Pyrus Malus L.), a lag in temperature during cooling at a constant rate was observed at about −41 C by differential thermal analysis. The temperature at which this low temperature exotherm occurred was essentially unaffected by the cooling rate. During thawing there was no lag in temperature (endotherm) near the temperature at which the low temperature exotherm occurred, but upon subsequent refreezing the exotherm reappeared at a somewhat higher temperature when twigs were rewarmed to at least −5 C before refreezing. These observations indicate that a small fraction of water may remain unfrozen to as low as −42 C after freezing of the bulk water in stems. The low temperature exotherm was not present in twigs freeze-dried to a water content below 8.5% (per unit fresh weight), but it reappeared when twigs were rehydrated to 20% water. When freeze-dried twigs were ground to a fine powder prior to rehydration, no exotherm was observed. Previous work has shown that the low temperature exotherm arises from xylem and pith tissues, and that injury to living cells in these tissues invariably occurs only when twigs are cooled below, but not above the temperature of the low temperature exotherm. This study revealed that the low temperature exotherm resulted from the freezing of a water fraction, that the freezing of this water was independent of the freezing of the bulk water, that the exotherm was associated with some gross structural feature but not the viability of the tissue, and that injury to living cells in the xylem and pith was closely and perhaps causally related to the initial freezing of this water. PMID:16658314

Lead mobility within the xylem of red spruce seedlings: Implications for the development of pollution histories

Treesearch

John R. Donnelly; John B. Shane; Paul G. Schaberg

1990-01-01

Development of Pb pollution histories using tree ring analyses has been troubled by possible mobility of Pb within stem xylem. In a 2-yr study, we exposed red spruce (Picea rubens Sarg.) seedlings to Pb during one growing season, with Pb excluded in either the previous or following growing season. Lead levels within xylem rings and bark were...

Modeling the biomechanical and injury response of human liver parenchyma under tensile loading.

PubMed

Untaroiu, Costin D; Lu, Yuan-Chiao; Siripurapu, Sundeep K; Kemper, Andrew R

2015-01-01

The rapid advancement in computational power has made human finite element (FE) models one of the most efficient tools for assessing the risk of abdominal injuries in a crash event. In this study, specimen-specific FE models were employed to quantify material and failure properties of human liver parenchyma using a FE optimization approach. Uniaxial tensile tests were performed on 34 parenchyma coupon specimens prepared from two fresh human livers. Each specimen was tested to failure at one of four loading rates (0.01s(-1), 0.1s(-1), 1s(-1), and 10s(-1)) to investigate the effects of rate dependency on the biomechanical and failure response of liver parenchyma. Each test was simulated by prescribing the end displacements of specimen-specific FE models based on the corresponding test data. The parameters of a first-order Ogden material model were identified for each specimen by a FE optimization approach while simulating the pre-tear loading region. The mean material model parameters were then determined for each loading rate from the characteristic averages of the stress-strain curves, and a stochastic optimization approach was utilized to determine the standard deviations of the material model parameters. A hyperelastic material model using a tabulated formulation for rate effects showed good predictions in terms of tensile material properties of human liver parenchyma. Furthermore, the tissue tearing was numerically simulated using a cohesive zone modeling (CZM) approach. A layer of cohesive elements was added at the failure location, and the CZM parameters were identified by fitting the post-tear force-time history recorded in each test. The results show that the proposed approach is able to capture both the biomechanical and failure response, and accurately model the overall force-deflection response of liver parenchyma over a large range of tensile loadings rates. Copyright © 2014 Elsevier Ltd. All rights reserved.

Golgi Enrichment and Proteomic Analysis of Developing Pinus radiata Xylem by Free-Flow Electrophoresis

PubMed Central

Macdonald, Lucy J.; Adams, Paul D.; Petzold, Christopher J.; Strabala, Timothy J.; Wagner, Armin; Heazlewood, Joshua L.

2013-01-01

Our understanding of the contribution of Golgi proteins to cell wall and wood formation in any woody plant species is limited. Currently, little Golgi proteomics data exists for wood-forming tissues. In this study, we attempted to address this issue by generating and analyzing Golgi-enriched membrane preparations from developing xylem of compression wood from the conifer Pinus radiata. Developing xylem samples from 3-year-old pine trees were harvested for this purpose at a time of active growth and subjected to a combination of density centrifugation followed by free flow electrophoresis, a surface charge separation technique used in the enrichment of Golgi membranes. This combination of techniques was successful in achieving an approximately 200-fold increase in the activity of the Golgi marker galactan synthase and represents a significant improvement for proteomic analyses of the Golgi from conifers. A total of thirty known Golgi proteins were identified by mass spectrometry including glycosyltransferases from gene families involved in glucomannan and glucuronoxylan biosynthesis. The free flow electrophoresis fractions of enriched Golgi were highly abundant in structural proteins (actin and tubulin) indicating a role for the cytoskeleton during compression wood formation. The mass spectrometry proteomics data associated with this study have been deposited to the ProteomeXchange with identifier PXD000557. PMID:24416096

Synchronisms between bud and cambium phenology in black spruce: early-flushing provenances exhibit early xylem formation.

PubMed

Perrin, Magali; Rossi, Sergio; Isabel, Nathalie

2017-05-01

Bud and cambial phenology represent the adaptation of species to the local environment that allows the growing season to be maximized while minimizing the risk of frost for the developing tissues. The temporal relationship between the apical and radial meristems can help in the understanding of tree growth as a whole process. The aim of this study was to compare cambial phenology in black spruce (Picea mariana (Mill.) B.S.P.) provenances classified as early and late bud flushing. The different phases of cambial phenology were assessed on wood microcores sampled weekly from April to October in 2014 and 2015 from 61 trees growing in a provenance trial in Quebec, Canada. Trees showing an early bud flush also exhibited early reactivation of xylem differentiation, although an average difference of 12 days for buds corresponded to small although significant differences of 4 days for xylem. Provenances with early bud flush had an early bud set and completed xylem formation earlier than late bud flush provenances. No significant difference in the period of xylem formation and total growth was observed between the flushing classes. Our results demonstrate that the ecotype differentiation of black spruce provenances represented by the phenological adaptation of buds to the local climate corresponds to specific growth dynamics of the xylem. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Xylella fastidiosa infection and ethylene exposure result in xylem and water movement disruption in grapevine shoots.

PubMed

Pérez-Donoso, Alonso G; Greve, L Carl; Walton, Jeffrey H; Shackel, Ken A; Labavitch, John M

2007-02-01

It is conventionally thought that multiplication of the xylem-limited bacterium Xylella fastidiosa (Xf) within xylem vessels is the sole factor responsible for the blockage of water movement in grapevines (Vitis vinifera) affected by Pierce's disease. However, results from our studies have provided substantial support for the idea that vessel obstructions, and likely other aspects of the Pierce's disease syndrome, result from the grapevine's active responses to the presence of Xf, rather than to the direct action of the bacterium. The use of magnetic resonance imaging (MRI) to observe the distribution of water within the xylem has allowed us to follow nondestructively the development of vascular system obstructions subsequent to inoculation of grapevines with Xf. Because we have hypothesized a role for ethylene produced in vines following infection, the impact of vine ethylene exposure on obstruction development was also followed using MRI. In both infected and ethylene-exposed plants, MRI shows that an important proportion of the xylem vessels become progressively air embolized after the treatments. The loss of xylem water-transporting function, assessed by MRI, has been also correlated with a decrease in stem-specific hydraulic conductivity (K(S)) and the presence of tyloses in the lumens of obstructed water conduits. We have observed that the ethylene production of leaves from infected grapevines is greater than that from healthy vines and, therefore, propose that ethylene may be involved in a series of cellular events that coordinates the vine's response to the pathogen.

The amino acid distribution in rachis xylem sap and phloem exudate of Vitis vinifera 'Cabernet Sauvignon' bunches.

PubMed

Gourieroux, Aude M; Holzapfel, Bruno P; Scollary, Geoffrey R; McCully, Margaret E; Canny, Martin J; Rogiers, Suzy Y

2016-08-01

Amino acids are essential to grape berry and seed development and they are transferred to the reproductive structures through the phloem and xylem from various locations within the plant. The diurnal and seasonal dynamics of xylem and phloem amino acid composition in the leaf petiole and bunch rachis of field-grown Cabernet Sauvignon are described to better understand the critical periods for amino acid import into the berry. Xylem sap was extracted by the centrifugation of excised leaf petioles and rachises, while phloem exudate was collected by immersing these structures in an ethylenediaminetetraacetic acid (EDTA) buffer. Glutamine and glutamic acid were the predominant amino acids in the xylem sap of both grapevine rachises and petioles, while arginine and glycine were the principal amino acids of the phloem exudate. The amino acid concentrations within the xylem sap and phloem exudate derived from these structures were greatest during anthesis and fruit set, and a second peak occurred within the rachis phloem at the onset of ripening. The concentrations of the amino acids within the phloem and xylem sap of the rachis were highest just prior to or after midnight while the flow of sugar through the rachis phloem was greatest during the early afternoon. Sugar exudation rates from the rachis was greater than that of the petiole phloem between anthesis and berry maturity. In summary, amino acid and sugar delivery through the vasculature to grape berries fluctuates over the course of the day as well as through the season and is not necessarily related to levels near the source. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Effects of ventilation and sucrose concentrations on the growth and plantlet anatomy of micropropagated persian walnut plants

USDA-ARS?s Scientific Manuscript database

Plantlets grown in conventional tissue culture systems usually encounter physiological and anatomical abnormalities including inability to photosynthesize, low chlorophyll content, open stomata, lack of a cuticle layer in the leaf, abnormal xylem parenchyma etc. Photoautotrophic and photomixotrophic...

Vulnerability to xylem embolism as a major correlate of the environmental distribution of rain forest species on a tropical island.

PubMed

Trueba, Santiago; Pouteau, Robin; Lens, Frederic; Feild, Taylor S; Isnard, Sandrine; Olson, Mark E; Delzon, Sylvain

2017-02-01

Increases in drought-induced tree mortality are being observed in tropical rain forests worldwide and are also likely to affect the geographical distribution of tropical vegetation. However, the mechanisms underlying the drought vulnerability and environmental distribution of tropical species have been little studied. We measured vulnerability to xylem embolism (P 50 ) of 13 woody species endemic to New Caledonia and with different xylem conduit morphologies. We examined the relation between P 50 , along with other leaf and xylem functional traits, and a range of habitat variables. Selected species had P 50 values ranging between -4.03 and -2.00 MPa with most species falling in a narrow range of resistance to embolism above -2.7 MPa. Embolism vulnerability was significantly correlated with elevation, mean annual temperature and percentage of species occurrences located in rain forest habitats. Xylem conduit type did not explain variation in P 50 . Commonly used functional traits such as wood density and leaf traits were not related to embolism vulnerability. Xylem embolism vulnerability stands out among other commonly used functional traits as a major driver of species environmental distribution. Drought-induced xylem embolism vulnerability behaves as a physiological trait closely associated with the habitat occupation of rain forest woody species. © 2016 John Wiley & Sons Ltd.

Secondary metabolite concentrations and terpene emissions of Scots pine xylem after long-term forest fertilization.

PubMed

Turtola, S; Manninen, A M; Holopainen, J K; Levula, T; Raitio, H; Kainulainen, P

2002-01-01

Secondary compounds are known to be associated with the resistance of conifer xylem against insects and fungi. The effects of long-term forest fertilization with nitrogen (N) or with N, calcium (Ca), and phosphorus (P) on secondary compounds in the xylem of 50-yr-old Scots pine (Pinus sylvestris L.) trees were examined. Xylem samples were collected from trees growing in three locations in southern Finland: Vilppula, Padasjoki, and Punkaharju. Forests were fertilized every fifth (Vilppula and Padasjoki) or tenth (Punkaharju) year since the 1950s. We compared concentrations of individual and total monoterpenes and resin acids in the heartwood and sapwood of Scots pine. Terpene emissions were analyzed from the sapwood and total phenolics from the heartwood. Fertilization did not have any significant effect on the concentrations and emissions of xylem monoterpenes. Concentrations of several individual terpenes in sapwood were positively correlated with the corresponding terpene emission. The concentrations of individual resin acids (i.e., abietic and dehydroabietic) decreased significantly in Punkaharju, but increased in the sapwood of N-fertilized trees compared with control ones at Padasjoki and Vilppula. The concentrations of resin acids in the heartwood were not significantly affected by fertilization. Both fertilization treatments decreased the total phenolic concentrations in the heartwood of trees growing in Padasjoki. There was a significant positive correlation between the total phenolics and total resin acid concentration. Overall, resin acids and phenolics seemed be more responsive than monoterpenes to N treatment. These results suggest that forest fertilization might cause slight changes in secondary compound concentrations of xylem, and thus might have significance in the decay resistance of wood.

Uncoupling between soil and xylem water isotopic composition: how to discriminate mobile and tightly-bound water?

NASA Astrophysics Data System (ADS)

Martín Gómez, Paula; Aguilera, Mònica; Pemán, Jesús; Gil Pelegrín, Eustaquio; Ferrio, Juan Pedro

2014-05-01

As a general rule, no isotopic fractionation occurs during water uptake and water transport, thus, xylem water reflects source water. However, this correspondence does not always happen. Isotopic enrichment of xylem water has been found in several cases and has been either associated to 'stem processes' like cuticular evaporation 1 and xylem-phloem communication under water stress 2,3 or to 'soil processes' such as species-specific use of contrasting water sources retained at different water potential forces in soil. In this regard, it has been demonstrated that mobile and tightly-bound water may show different isotopic signature 4,5. However, standard cryogenic distillation does not allow to separate different water pools within soil samples. Here, we carried out a study in a mixed adult forest (Pinus sylvestris, Quercus subpyrenaica and Buxus sempervirens) growing in a relatively deep loamy soil in the Pre-Pyrenees. During one year, we sampled xylem from twigs and soil at different depths (10, 30 and 50 cm). We also sampled xylem from trunk and bigger branches to assess whether xylem water was enriched in the distal parts of the tree. We found average deviations in the isotopic signature from xylem to soil of 4o 2o and 2.4o in δ18O and 18.3o 7.3o and 8.9o in δ2H, for P.sylvestris, Q.subpyrenaica and B.sempervirens respectively. Xylem water was always enriched compared to soil. In contrast, we did not find clear differences in isotopic composition between xylem samples along the tree. Declining the hypothesis that 'stem processes' would cause these uncoupling between soil and xylem isotopic values, we tested the possibility to separate mobile and tightly-bound water by centrifugation. Even though we could separate two water fractions in soils close to saturation, we could not recover a mobile fraction in drier soils. In this regard, we welcome suggestions on alternatives to separate different soil fractions in order to find the correspondence between soil and

Curios relationship revealed by looking at long term data sets-The geometry and allometric scaling of diel xylem sap flux in tropical trees.

PubMed

Kunert, Norbert

2016-10-20

Daily xylem sap flux values (daily J s ) and maximum xylem sap flux values (max J s ) from 125 tropical trees from different study sites in the Neotropics were compared. A cross species and study site relationship was found between daily and maximum values. The relationship can be expressed as daily J s =6.5x max J s . The geometrical relationship between the maximum xylem sap flux of a given day is thus defining the daily xylem sap flux rates. Assuming a bell-shaped diurnal sap flux course and a relatively constant day length the maximum xylem sap flux is the only possible changing variable to define daily fluxes. Further, this relationship is showing the inertia of the xylem sap flux as a physical object and highlights the delayed response to environmental changes and its subsequent inevitable susceptibility under environmental stress to hydraulic failure. Copyright © 2016 Elsevier GmbH. All rights reserved.

Trade-offs between xylem hydraulic properties, wood anatomy and yield in Populus.

PubMed

Hajek, Peter; Leuschner, Christoph; Hertel, Dietrich; Delzon, Sylvain; Schuldt, Bernhard

2014-07-01

Trees face the dilemma that achieving high plant productivity is accompanied by a risk of drought-induced hydraulic failure due to a trade-off in the trees' vascular system between hydraulic efficiency and safety. By investigating the xylem anatomy of branches and coarse roots, and measuring branch axial hydraulic conductivity and vulnerability to cavitation in 4-year-old field-grown aspen plants of five demes (Populus tremula L. and Populus tremuloides Michx.) differing in growth rate, we tested the hypotheses that (i) demes differ in wood anatomical and hydraulic properties, (ii) hydraulic efficiency and safety are related to xylem anatomical traits, and (iii) aboveground productivity and hydraulic efficiency are negatively correlated to cavitation resistance. Significant deme differences existed in seven of the nine investigated branch-related anatomical and hydraulic traits but only in one of the four coarse-root-related anatomical traits; this likely is a consequence of high intra-plant variation in root morphology and the occurrence of a few 'high-conductivity roots'. Growth rate was positively related to branch hydraulic efficiency (xylem-specific conductivity) but not to cavitation resistance; this indicates that no marked trade-off exists between cavitation resistance and growth. Both branch hydraulic safety and hydraulic efficiency significantly depended on vessel size and were related to the genetic distance between the demes, while the xylem pressure causing 88% loss of hydraulic conductivity (P88 value) was more closely related to hydraulic efficiency than the commonly used P50 value. Deme-specific variation in the pit membrane structure may explain why vessel size was not directly linked to growth rate. We conclude that branch hydraulic efficiency is an important growth-influencing trait in aspen, while the assumed trade-off between productivity and hydraulic safety is weak. © The Author 2014. Published by Oxford University Press. All rights reserved

Evidence for Hydraulic Vulnerability Segmentation and Lack of Xylem Refilling under Tension.

PubMed

Charrier, Guillaume; Torres-Ruiz, José M; Badel, Eric; Burlett, Regis; Choat, Brendan; Cochard, Herve; Delmas, Chloe E L; Domec, Jean-Christophe; Jansen, Steven; King, Andrew; Lenoir, Nicolas; Martin-StPaul, Nicolas; Gambetta, Gregory Alan; Delzon, Sylvain

2016-11-01

The vascular system of grapevine (Vitis spp.) has been reported as being highly vulnerable, even though grapevine regularly experiences seasonal drought. Consequently, stomata would remain open below water potentials that would generate a high loss of stem hydraulic conductivity via xylem embolism. This situation would necessitate daily cycles of embolism repair to restore hydraulic function. However, a more parsimonious explanation is that some hydraulic techniques are prone to artifacts in species with long vessels, leading to the overestimation of vulnerability. The aim of this study was to provide an unbiased assessment of (1) the vulnerability to drought-induced embolism in perennial and annual organs and (2) the ability to refill embolized vessels in two Vitis species X-ray micro-computed tomography observations of intact plants indicated that both Vitis vinifera and Vitis riparia were relatively vulnerable, with the pressure inducing 50% loss of stem hydraulic conductivity = -1.7 and -1.3 MPa, respectively. In V. vinifera, both the stem and petiole had similar sigmoidal vulnerability curves but differed in pressure inducing 50% loss of hydraulic conductivity (-1.7 and -1 MPa for stem and petiole, respectively). Refilling was not observed as long as bulk xylem pressure remained negative (e.g. at the apical part of the plants; -0.11 ± 0.02 MPa) and change in percentage loss of conductivity was 0.02% ± 0.01%. However, positive xylem pressure was observed at the basal part of the plant (0.04 ± 0.01 MPa), leading to a recovery of conductance (change in percentage loss of conductivity = -0.24% ± 0.12%). Our findings provide evidence that grapevine is unable to repair embolized xylem vessels under negative pressure, but its hydraulic vulnerability segmentation provides significant protection of the perennial stem. © 2016 American Society of Plant Biologists. All Rights Reserved.

Interplay of growth rate and xylem plasticity for optimal coordination of carbon and hydraulic economies in Fraxinus ornus trees.

PubMed

Petit, Giai; Savi, Tadeja; Consolini, Martina; Anfodillo, Tommaso; Nardini, Andrea

2016-11-01

Efficient leaf water supply is fundamental for assimilation processes and tree growth. Renovating the architecture of the xylem transport system requires an increasing carbon investment while growing taller, and any deficiency of carbon availability may result in increasing hydraulic constraints to water flow. Therefore, plants need to coordinate carbon assimilation and biomass allocation to guarantee an efficient and safe long-distance transport system. We tested the hypothesis that reduced branch elongation rates together with carbon-saving adjustments of xylem anatomy hydraulically compensate for the reduction in biomass allocation to xylem. We measured leaf biomass, hydraulic and anatomical properties of wood segments along the main axis of branches in 10 slow growing (SG) and 10 fast growing (FG) Fraxinus ornus L. trees. Branches of SG trees had five times slower branch elongation rate (7 vs 35 cm year -1 ), and produced a higher leaf biomass (P < 0.0001) and thinner xylem rings with fewer but larger vessels (P < 0.0001). On the contrary, we found no differences between SG and FG trees in terms of leaf-specific conductivity (P > 0.05) and xylem safety (Ψ 50 ≈ -3.2 MPa). Slower elongation rate coupled with thinner annual rings and larger vessels allows the reduction of carbon costs associated with growth, while maintaining similar leaf-specific conductivity and xylem safety. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Circadian patterns of xylem sap properties and their covariation with plant hydraulic traits in hybrid aspen.

PubMed

Meitern, Annika; Õunapuu-Pikas, Eele; Sellin, Arne

2017-06-01

Physiological processes taking place in plants are subject to diverse circadian patterns but some of them are poorly documented in natural conditions. The daily dynamics of physico-chemical properties of xylem sap and their covariation with tree hydraulic traits were investigated in hybrid aspen (Populus tremula L.×P. tremuloides Michx) in field conditions in order to clarify which environmental drivers govern the daily variation in these parameters. K + concentration ([K + ]), electrical conductivity (σ sap ), osmolality (Osm) and pH of the xylem sap, as well as branch hydraulic traits, were measured in the field over 24-h cycles. All studied xylem sap properties and hydraulic characteristics including whole-branch (K wb ), leaf blade (K lb ) and petiole hydraulic conductances (K P ) showed clear daily dynamics. Air temperature (T A ) and photosynthetic photon flux density (PPFD), but also water vapour pressure deficit (VPD) and relative humidity (RH), had significant impacts on K wb K lb , K P , [K + ] and σ sap . Osm varied only with light intensity, while K B varied depending on atmospheric evaporative demand expressed as T A , VPD or RH. Xylem sap pH depended inversely on soil water potential (Ψ S ) and during daylight also on VPD. Although soil water content was close to saturation during the study period, Ψ S influenced also [K + ] and σ sap . The present study presents evidence of coupling between circadian patterns of xylem sap properties and plant hydraulic conductance providing adequate water supply to foliage under environmental conditions characterised by diurnal variation. Copyright © 2017 Elsevier GmbH. All rights reserved.

Plastic and locally adapted phenology in cambial seasonality and production of xylem and phloem cells in Picea abies from temperate environments.

PubMed

Gričar, Jožica; Prislan, Peter; Gryc, Vladimír; Vavrčík, Hanuš; de Luis, Martin; Cufar, Katarina

2014-08-01

Despite its major economic importance and the vulnerability of Picea abies (L.) H. Karst. to climate change, how its radial growth at intra-annual resolution is influenced by weather conditions in forest stands with a high production capacity has scarcely been explored. Between 2009 and 2011, phenological variation in seasonal cambial cell production (CP) was analysed in adult P. abies trees from three contrasting sites, differing in altitude and latitude. The results indicate that the timing of cambial CP is a highly synchronic process within populations since in all cases the cambium simultaneously started and stopped producing xylem and phloem cells. Our results also demonstrate that the phenology of cambial CP is highly variable and plastic between years, depending on seasonal temperature and precipitation variation. Differences among sites, however, are only partially explained by different environmental (elevation and altitude) and climatic conditions, suggesting that local adaptation may also play a decisive role in the strategy of P. abies for adapting wood and phloem increments to function optimally under local conditions. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Maximum sustainable xylem sap tensions in Rhododendron and other species.

PubMed

Crombie, D S; Milburn, J A; Hipkins, M F

1985-01-01

The acoustic technique was used in conjunction with the pressure chamber to determine the tensions causing cavitation of xylem sap in leaves of five woody angiosperms (Acer pseudoplatanus L., Alnus glutinosa L. Gaertn., Eucalyptus globulus Labill., Fraxinus excelsior L. and Rhododendron ponticum L.) and three species of herbs (Lycopersicum esculentum Mill., Plantago major L. and Ricinus communis L.). The results showed leaves of most species to suffer considerably from cavitation at sap tensions of 1.6-3 MPa. Two of the herbs, Lycopersicum and Ricinus, cavitated extensively at sap tensions below 1 MPa. Additional evidence is presented that clicks, detected by acoustic amplification, are caused by cavitation of sap in the xylem conduits. A rapid method is suggested for the determination of sap tensions in cavitating leaves and which is suitable for surveys of the critical sap tension in a large number of species.

Brain parenchyma PO2, PCO2, and pH during and after hypoxic, ischemic brain insult in dogs.

PubMed

McKinley, B A; Morris, W P; Parmley, C L; Butler, B D

1996-11-01

1) The investigation of fiberoptic PO2, PCO2, and pH sensor technology as a monitor of brain parenchyma during and after brain injury, and 2) the comparison of brain parenchyma PO2, PCO2, and pH with intracranial pressure during and after hypoxic, ischemic brain insult. Prospective, controlled, animal study in an acute experimental preparation. Physiology laboratory in a university medical school. Fourteen mongrel dogs (20 to 35 kg), anesthetized, room-air ventilated. Anesthesia was induced with thiopental and maintained after intubation using 1% to 1.5% halothane in room air (FiO2 0.21). Mechanical ventilation was established to maintain end-tidal PCO2 approximately 35 torr (-4.7 kPa). Intravenous, femoral artery, and pulmonary artery catheters were placed. The common carotid arteries were surgically exposed, and ultrasonic blood flow probes were applied. A calibrated intracranial pressure probe was placed through a right-side transcranial bolt, and a calibrated intracranial chemistry probe with optical sensors for PO2, PCO2, and pH was placed through a left-side bolt into brain parenchyma. Brain insult was induced in the experimental group (n = 6) by hypoxia (FiO2 0.1), ischemia (bilateral carotid artery occlusion), and hypotension (mean arterial pressure [MAP] approximately 40 mm Hg produced with isoflurane approximately 4%). After 45 mins, carotid artery occlusion was released, FiO2 was reset to 0.21, and anesthetic was returned to halothane (approximately 1.25%). The control group (n = 5) had the same surgical preparation and sequence of anesthetic agent exposure but no brain insult. Monitored variables included brain parenchyma PO2, PCO2, and pH, which were monitored at 1-min intervals, and intracranial pressure, MAP, arterial hemoglobin oxygen saturation (by pulse oximetry), end-tidal PCO2, and carotid artery blood flow rate, for which data were collected at 15-min intervals for 7 hrs. Arterial and mixed venous blood gas analyses were done at approximately 1

Specific Fluorescence in Situ Hybridization (FISH) Test to Highlight Colonization of Xylem Vessels by Xylella fastidiosa in Naturally Infected Olive Trees (Olea europaea L.)

PubMed Central

Cardinale, Massimiliano; Luvisi, Andrea; Meyer, Joana B.; Sabella, Erika; De Bellis, Luigi; Cruz, Albert C.; Ampatzidis, Yiannis; Cherubini, Paolo

2018-01-01

The colonization behavior of the Xylella fastidiosa strain CoDiRO, the causal agent of olive quick decline syndrome (OQDS), within the xylem of Olea europaea L. is still quite controversial. As previous literature suggests, even if xylem vessel occlusions in naturally infected olive plants were observed, cell aggregation in the formation of occlusions had a minimal role. This observation left some open questions about the whole behavior of the CoDiRO strain and its actual role in OQDS pathogenesis. In order to evaluate the extent of bacterial infection in olive trees and the role of bacterial aggregates in vessel occlusions, we tested a specific fluorescence in situ hybridization (FISH) probe (KO 210) for X. fastidiosa and quantified the level of infection and vessel occlusion in both petioles and branches of naturally infected and non-infected olive trees. All symptomatic petioles showed colonization by X. fastidiosa, especially in the larger innermost vessels. In several cases, the vessels appeared completely occluded by a biofilm containing bacterial cells and extracellular matrix and the frequent colonization of adjacent vessels suggested a horizontal movement of the bacteria. Infected symptomatic trees had 21.6 ± 10.7% of petiole vessels colonized by the pathogen, indicating an irregular distribution in olive tree xylem. Thus, our observations point out the primary role of the pathogen in olive vessel occlusions. Furthermore, our findings indicate that the KO 210 FISH probe is suitable for the specific detection of X. fastidiosa. PMID:29681910

Xylem monoterpenes of pines: distribution, variation, genetics, function

Treesearch

Richard Smith

2000-01-01

The monoterpenes of about 16,000 xylem resin samples of pine (Pinus) speciesand hybrids—largely from the western United States—were analyzed in this long-term study of the resistance of pines to attack by bark beetles (Coleoptera:Scolytidae), with special emphasis on resistance to the western pine beetle(Dendroctonus brevicomis). The samples were analyzed by gas liquid...

Metabolomics of tomato xylem sap during bacterial wilt reveals Ralstonia solanacearum produces abundant putrescine, a metabolite that accelerates wilt disease.

PubMed

Lowe-Power, Tiffany M; Hendrich, Connor G; von Roepenack-Lahaye, Edda; Li, Bin; Wu, Dousheng; Mitra, Raka; Dalsing, Beth L; Ricca, Patrizia; Naidoo, Jacinth; Cook, David; Jancewicz, Amy; Masson, Patrick; Thomma, Bart; Lahaye, Thomas; Michael, Anthony J; Allen, Caitilyn

2018-04-01

Ralstonia solanacearum thrives in plant xylem vessels and causes bacterial wilt disease despite the low nutrient content of xylem sap. We found that R. solanacearum manipulates its host to increase nutrients in tomato xylem sap, enabling it to grow better in sap from infected plants than in sap from healthy plants. Untargeted GC/MS metabolomics identified 22 metabolites enriched in R. solanacearum-infected sap. Eight of these could serve as sole carbon or nitrogen sources for R. solanacearum. Putrescine, a polyamine that is not a sole carbon or nitrogen source for R. solanacearum, was enriched 76-fold to 37 µM in R. solanacearum-infected sap. R. solanacearum synthesized putrescine via a SpeC ornithine decarboxylase. A ΔspeC mutant required ≥ 15 µM exogenous putrescine to grow and could not grow alone in xylem even when plants were treated with putrescine. However, co-inoculation with wildtype rescued ΔspeC growth, indicating R. solanacearum produced and exported putrescine to xylem sap. Intriguingly, treating plants with putrescine before inoculation accelerated wilt symptom development and R. solanacearum growth and systemic spread. Xylem putrescine concentration was unchanged in putrescine-treated plants, so the exogenous putrescine likely accelerated disease indirectly by affecting host physiology. These results indicate that putrescine is a pathogen-produced virulence metabolite. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

Molecular crosstalk between tumour and brain parenchyma instructs histopathological features in glioblastoma.

PubMed

Bougnaud, Sébastien; Golebiewska, Anna; Oudin, Anaïs; Keunen, Olivier; Harter, Patrick N; Mäder, Lisa; Azuaje, Francisco; Fritah, Sabrina; Stieber, Daniel; Kaoma, Tony; Vallar, Laurent; Brons, Nicolaas H C; Daubon, Thomas; Miletic, Hrvoje; Sundstrøm, Terje; Herold-Mende, Christel; Mittelbronn, Michel; Bjerkvig, Rolf; Niclou, Simone P

2016-05-31

The histopathological and molecular heterogeneity of glioblastomas represents a major obstacle for effective therapies. Glioblastomas do not develop autonomously, but evolve in a unique environment that adapts to the growing tumour mass and contributes to the malignancy of these neoplasms. Here, we show that patient-derived glioblastoma xenografts generated in the mouse brain from organotypic spheroids reproducibly give rise to three different histological phenotypes: (i) a highly invasive phenotype with an apparent normal brain vasculature, (ii) a highly angiogenic phenotype displaying microvascular proliferation and necrosis and (iii) an intermediate phenotype combining features of invasion and vessel abnormalities. These phenotypic differences were visible during early phases of tumour development suggesting an early instructive role of tumour cells on the brain parenchyma. Conversely, we found that tumour-instructed stromal cells differentially influenced tumour cell proliferation and migration in vitro, indicating a reciprocal crosstalk between neoplastic and non-neoplastic cells. We did not detect any transdifferentiation of tumour cells into endothelial cells. Cell type-specific transcriptomic analysis of tumour and endothelial cells revealed a strong phenotype-specific molecular conversion between the two cell types, suggesting co-evolution of tumour and endothelial cells. Integrative bioinformatic analysis confirmed the reciprocal crosstalk between tumour and microenvironment and suggested a key role for TGFβ1 and extracellular matrix proteins as major interaction modules that shape glioblastoma progression. These data provide novel insight into tumour-host interactions and identify novel stroma-specific targets that may play a role in combinatorial treatment strategies against glioblastoma.

Down-regulation of SlIAA15 in tomato altered stem xylem development and production of volatile compounds in leaf exudates.

PubMed

Deng, Wei; Yan, Fang; Liu, Minchun; Wang, Xinyu; Li, Zhengguo

2012-08-01

The Aux/IAA family genes encode short-lived nuclear proteins that function as transcriptional regulators in auxin signal transduction. Aux/IAA genes have been reported to control many processes of plant development. Our recent study showed that down-regulation of SlIAA15 in tomato reduced apical dominance, altered pattern of axillary shoot development, increased lateral root formation and leaves thickness. The SlIAA15 suppressed lines display strong reduction of trichome density, suggesting that SlIAA15 is involved in trichome formation. Here, we reported that SlIAA15-suppressed transgenic lines display increased number of xylem cells compared to wild-type plants. Moreover, the monoterpene content in trichome exudates are significantly reduced in SlIAA15 down-regulated leaves. The results provide the roles of SlIAA15 in production of volatile compounds in leaf exudates and xylem development, clearly indicating that members of the Aux/IAA gene family can play distinct and specific functions. 

Volumetric analysis of cerebrospinal fluid and brain parenchyma in a patient with hydranencephaly and macrocephaly--case report.

PubMed

Radoš, Milan; Klarica, Marijan; Mučić-Pucić, Branka; Nikić, Ines; Raguž, Marina; Galkowski, Valentina; Mandić, Dora; Orešković, Darko

2014-08-28

The aim of this study was to perform for the first time the intracranial volumetric analysis of cerebrospinal fluid (CSF) and brain parenchyma in the supratentorial and infratentorial space in a 30-year-old female patient with hydranencephaly and macrocephaly. A head scan performed using a 3T magnetic resonance was followed by manual segmentation of the brain parenchyma and CSF on T2 coronal brain sections. The volume of CSF and brain parenchyma was measured separately for the supratentorial and infratentorial space. The total volume of the intracranial space was 3645.5 cm3. In the supratentorial space, the volume of CSF was 3375.2 cm3 and the volume of brain parenchyma was 80.3 cm3. In the infratentorial space, the volume of CSF was 101.3 cm3 and the volume of the brain parenchyma was 88.7 cm3. In the supratentorial space, there was severe malacia of almost all brain parenchyma with no visible remnants of the choroid plexuses. Infratentorial structures of the brainstem and cerebellum were hypoplastic but completely developed. Since our patient had no choroid plexuses in the supratentorial space and no obstruction between dural sinuses and CSF, development of hydrocephalus and macrocephaly cannot be explained by the classic hypothesis of CSF physiology with secretion, unidirectional circulation, and absorption as its basic postulates. However, the origin and turnover of the enormous amount of intracranial CSF volume, at least 10-fold larger than normal, and the mechanisms of macroencephaly development could be elucidated by the new hypothesis of CSF physiology recently published by our research team.

Xylem vulnerability curves of canopy branches of mature trees from Caxiuana and Tapajos National Forests, Para, Brazil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powell, Thomas; Moorcroft, Paul

Raw data for xylem vulnerability curves measured on upper canopy branches of mature trees from the Caxiuana and Tapajos National Forests, Para, Brazil. Tapajos samples were harvested from km67 transects, which is nearby the decommissioned throughfall-exclusion, drought-experiment plots. Caxiuana samples were harvested from trees growing in the throughfall-exclusion, drought-experiment plots. Data were collected in 2011 and 2012. Dataset includes: date of measurement, site ID, plot ID, tree ID (species, tree tag #), xylem pressure, percent loss of conductivity. Air injection method was used. Data reference: Powell et al. (2017) Differences in xylem cavitation resistance and leaf hydraulic traits explain differencesmore » in drought tolerance among mature Amazon rainforest trees. Global Change Biology.« less

Hierarchical statistical modeling of xylem vulnerability to cavitation.

PubMed

Ogle, Kiona; Barber, Jarrett J; Willson, Cynthia; Thompson, Brenda

2009-01-01

Cavitation of xylem elements diminishes the water transport capacity of plants, and quantifying xylem vulnerability to cavitation is important to understanding plant function. Current approaches to analyzing hydraulic conductivity (K) data to infer vulnerability to cavitation suffer from problems such as the use of potentially unrealistic vulnerability curves, difficulty interpreting parameters in these curves, a statistical framework that ignores sampling design, and an overly simplistic view of uncertainty. This study illustrates how two common curves (exponential-sigmoid and Weibull) can be reparameterized in terms of meaningful parameters: maximum conductivity (k(sat)), water potential (-P) at which percentage loss of conductivity (PLC) =X% (P(X)), and the slope of the PLC curve at P(X) (S(X)), a 'sensitivity' index. We provide a hierarchical Bayesian method for fitting the reparameterized curves to K(H) data. We illustrate the method using data for roots and stems of two populations of Juniperus scopulorum and test for differences in k(sat), P(X), and S(X) between different groups. Two important results emerge from this study. First, the Weibull model is preferred because it produces biologically realistic estimates of PLC near P = 0 MPa. Second, stochastic embolisms contribute an important source of uncertainty that should be included in such analyses.

Overexpression of poplar xylem sucrose synthase in tobacco leads to a thickened cell wall and increased height.

PubMed

Wei, Zhigang; Qu, Zanshuang; Zhang, Lijie; Zhao, Shuanjing; Bi, Zhihong; Ji, Xiaohui; Wang, Xiaowen; Wei, Hairong

2015-01-01

Sucrose synthase (SuSy) is considered the first key enzyme for secondary growth because it is a highly regulated cytosolic enzyme that catalyzes the reversible conversion of sucrose and UDP into UDP-glucose and fructose. Although SuSy enzymes preferentially functions in the direction of sucrose cleavage at most cellular condition, they also catalyze the synthetic reaction. We isolated a gene that encodes a SuSy from Populus simonii×Populus nigra and named it PsnSuSy2 because it shares high similarity to SuSy2 in Populus trichocarpa. RT-PCR revealed that PsnSuSy2 was highly expressed in xylem, but lowly expressed in young leaves. To characterize its functions in secondary growth, multiple tobacco overexpression transgenic lines of PnsSuSy2 were generated via Agrobacterium-mediated transformation. The PsnSuSy2 expression levels and altered wood properties in stem segments from the different transgenic lines were carefully characterized. The results demonstrated that the levels of PsnSuSy2 enzyme activity, chlorophyll content, total soluble sugars, fructose and glucose increased significantly, while the sucrose level decreased significantly. Consequently, the cellulose content and fiber length increased, whereas the lignin content decreased, suggesting that PsnSuSy2 plays a significant role in cleaving sucrose into UDP-glucose and fructose to facilitate cellulose biosynthesis and that promotion of cellulose biosynthesis suppresses lignin biosynthesis. Additionally, the noticeable increase in the lodging resistance in transgenic tobacco stem suggested that the cell wall characteristics were altered by PsnSuSy2 overexpression. Scanning electron microscopy was performed to study the cell wall morphology of stem, and surprisingly, we found that the secondary cell wall was significantly thicker in transgenic tobacco. However, the thickened secondary cell wall did not negatively affect the height of the plants because the PsnSuSy2- overexpressing lines grew taller than the

Overexpression of Poplar Xylem Sucrose Synthase in Tobacco Leads to a Thickened Cell Wall and Increased Height

PubMed Central

Wei, Zhigang; Qu, Zanshuang; Zhang, Lijie; Zhao, Shuanjing; Bi, Zhihong; Ji, Xiaohui; Wang, Xiaowen; Wei, Hairong

2015-01-01

Sucrose synthase (SuSy) is considered the first key enzyme for secondary growth because it is a highly regulated cytosolic enzyme that catalyzes the reversible conversion of sucrose and UDP into UDP-glucose and fructose. Although SuSy enzymes preferentially functions in the direction of sucrose cleavage at most cellular condition, they also catalyze the synthetic reaction. We isolated a gene that encodes a SuSy from Populus simonii×Populus nigra and named it PsnSuSy2 because it shares high similarity to SuSy2 in Populus trichocarpa. RT-PCR revealed that PsnSuSy2 was highly expressed in xylem, but lowly expressed in young leaves. To characterize its functions in secondary growth, multiple tobacco overexpression transgenic lines of PnsSuSy2 were generated via Agrobacterium-mediated transformation. The PsnSuSy2 expression levels and altered wood properties in stem segments from the different transgenic lines were carefully characterized. The results demonstrated that the levels of PsnSuSy2 enzyme activity, chlorophyll content, total soluble sugars, fructose and glucose increased significantly, while the sucrose level decreased significantly. Consequently, the cellulose content and fiber length increased, whereas the lignin content decreased, suggesting that PsnSuSy2 plays a significant role in cleaving sucrose into UDP-glucose and fructose to facilitate cellulose biosynthesis and that promotion of cellulose biosynthesis suppresses lignin biosynthesis. Additionally, the noticeable increase in the lodging resistance in transgenic tobacco stem suggested that the cell wall characteristics were altered by PsnSuSy2 overexpression. Scanning electron microscopy was performed to study the cell wall morphology of stem, and surprisingly, we found that the secondary cell wall was significantly thicker in transgenic tobacco. However, the thickened secondary cell wall did not negatively affect the height of the plants because the PsnSuSy2- overexpressing lines grew taller than the

Cellulose synthase complexes display distinct dynamic behaviors during xylem transdifferentiation.

PubMed

Watanabe, Yoichiro; Schneider, Rene; Barkwill, Sarah; Gonzales-Vigil, Eliana; Hill, Joseph L; Samuels, A Lacey; Persson, Staffan; Mansfield, Shawn D

2018-06-05

In plants, plasma membrane-embedded CELLULOSE SYNTHASE (CESA) enzyme complexes deposit cellulose polymers into the developing cell wall. Cellulose synthesis requires two different sets of CESA complexes that are active during cell expansion and secondary cell wall thickening, respectively. Hence, developing xylem cells, which first undergo cell expansion and subsequently deposit thick secondary walls, need to completely reorganize their CESA complexes from primary wall- to secondary wall-specific CESAs. Using live-cell imaging, we analyzed the principles underlying this remodeling. At the onset of secondary wall synthesis, the primary wall CESAs ceased to be delivered to the plasma membrane and were gradually removed from both the plasma membrane and the Golgi. For a brief transition period, both primary wall- and secondary wall-specific CESAs coexisted in banded domains of the plasma membrane where secondary wall synthesis is concentrated. During this transition, primary and secondary wall CESAs displayed discrete dynamic behaviors and sensitivities to the inhibitor isoxaben. As secondary wall-specific CESAs were delivered and inserted into the plasma membrane, the primary wall CESAs became concentrated in prevacuolar compartments and lytic vacuoles. This adjustment in localization between the two CESAs was accompanied by concurrent decreased primary wall CESA and increased secondary wall CESA protein abundance. Our data reveal distinct and dynamic subcellular trafficking patterns that underpin the remodeling of the cellulose biosynthetic machinery, resulting in the removal and degradation of the primary wall CESA complex with concurrent production and recycling of the secondary wall CESAs. Copyright © 2018 the Author(s). Published by PNAS.

Generation and analysis of expressed sequence tags from six developing xylem libraries in Pinus radiata D. Don

PubMed Central

Li, Xinguo; Wu, Harry X; Dillon, Shannon K; Southerton, Simon G

2009-01-01

Background Wood is a major renewable natural resource for the timber, fibre and bioenergy industry. Pinus radiata D. Don is the most important commercial plantation tree species in Australia and several other countries; however, genomic resources for this species are very limited in public databases. Our primary objective was to sequence a large number of expressed sequence tags (ESTs) from genes involved in wood formation in radiata pine. Results Six developing xylem cDNA libraries were constructed from earlywood and latewood tissues sampled at juvenile (7 yrs), transition (11 yrs) and mature (30 yrs) ages, respectively. These xylem tissues represent six typical development stages in a rotation period of radiata pine. A total of 6,389 high quality ESTs were collected from 5,952 cDNA clones. Assembly of 5,952 ESTs from 5' end sequences generated 3,304 unigenes including 952 contigs and 2,352 singletons. About 97.0% of the 5,952 ESTs and 96.1% of the unigenes have matches in the UniProt and TIGR databases. Of the 3,174 unigenes with matches, 42.9% were not assigned GO (Gene Ontology) terms and their functions are unknown or unclassified. More than half (52.1%) of the 5,952 ESTs have matches in the Pfam database and represent 772 known protein families. About 18.0% of the 5,952 ESTs matched cell wall related genes in the MAIZEWALL database, representing all 18 categories, 91 of all 174 families and possibly 557 genes. Fifteen cell wall-related genes are ranked in the 30 most abundant genes, including CesA, tubulin, AGP, SAMS, actin, laccase, CCoAMT, MetE, phytocyanin, pectate lyase, cellulase, SuSy, expansin, chitinase and UDP-glucose dehydrogenase. Based on the PlantTFDB database 41 of the 64 transcription factor families in the poplar genome were identified as being involved in radiata pine wood formation. Comparative analysis of GO term abundance revealed a distinct transcriptome in juvenile earlywood formation compared to other stages of wood development

Root xylem embolisms and refilling. Relation To water potentials of soil, roots, and leaves, and osmotic potentials of root xylem Sap

PubMed

McCully

1999-03-01

Embolism and refilling of vessels was monitored directly by cryomicroscopy of field-grown corn (Zea mays L.) roots. To test the reliability of an earlier study showing embolism refilling in roots at negative leaf water potentials, embolisms were counted, and root water potentials (Psiroot) and osmotic potentials of exuded xylem sap from the same roots were measured by isopiestic psychrometry. All vessels were full at dawn (Psiroot -0.1 MPa). Embolisms were first seen in late metaxylem vessels at 8 AM. Embolized late metaxylem vessels peaked at 50% at 10 AM (Psiroot -0.1 MPa), fell to 44% by 12 PM (Psiroot -0.23 MPa), then dropped steadily to zero by early evening (Psiroot -0.28 MPa). Transpiration was highest (8.5 μg cm-2 s-1) between 12 and 2 PM when the percentage of vessels embolized was falling. Embolized vessels were refilled by liquid moving through their lateral walls. Xylem sap was very low in solutes. The mechanism of vessel refilling, when Psiroot is negative, requires further investigation. Daily embolism and refilling in roots of well-watered plants is a normal occurrence and may be a component of an important hydraulic signaling mechanism between roots and shoots.

Molecular crosstalk between tumour and brain parenchyma instructs histopathological features in glioblastoma

PubMed Central

Bougnaud, Sébastien; Golebiewska, Anna; Oudin, Anaïs; Keunen, Olivier; Harter, Patrick N.; Mäder, Lisa; Azuaje, Francisco; Fritah, Sabrina; Stieber, Daniel; Kaoma, Tony; Vallar, Laurent; Brons, Nicolaas H.C.; Daubon, Thomas; Miletic, Hrvoje; Sundstrøm, Terje; Herold-Mende, Christel; Mittelbronn, Michel; Bjerkvig, Rolf; Niclou, Simone P.

2016-01-01

The histopathological and molecular heterogeneity of glioblastomas represents a major obstacle for effective therapies. Glioblastomas do not develop autonomously, but evolve in a unique environment that adapts to the growing tumour mass and contributes to the malignancy of these neoplasms. Here, we show that patient-derived glioblastoma xenografts generated in the mouse brain from organotypic spheroids reproducibly give rise to three different histological phenotypes: (i) a highly invasive phenotype with an apparent normal brain vasculature, (ii) a highly angiogenic phenotype displaying microvascular proliferation and necrosis and (iii) an intermediate phenotype combining features of invasion and vessel abnormalities. These phenotypic differences were visible during early phases of tumour development suggesting an early instructive role of tumour cells on the brain parenchyma. Conversely, we found that tumour-instructed stromal cells differentially influenced tumour cell proliferation and migration in vitro, indicating a reciprocal crosstalk between neoplastic and non-neoplastic cells. We did not detect any transdifferentiation of tumour cells into endothelial cells. Cell type-specific transcriptomic analysis of tumour and endothelial cells revealed a strong phenotype-specific molecular conversion between the two cell types, suggesting co-evolution of tumour and endothelial cells. Integrative bioinformatic analysis confirmed the reciprocal crosstalk between tumour and microenvironment and suggested a key role for TGFβ1 and extracellular matrix proteins as major interaction modules that shape glioblastoma progression. These data provide novel insight into tumour-host interactions and identify novel stroma-specific targets that may play a role in combinatorial treatment strategies against glioblastoma. PMID:27049916

Are phloem-derived amino acids the origin of the elevated malate concentration in the xylem sap following mineral N starvation in soybean?

PubMed

Vitor, Simone C; do Amarante, Luciano; Sodek, Ladaslav

2018-05-16

A substantial increase in malate in the xylem sap of soybean subjected to mineral N starvation originates mainly from aspartate, a prominent amino acid of the phloem. A substantial increase in xylem malate was found when non-nodulated soybean plants were transferred to a N-free medium. Nodulated plants growing in the absence of mineral N and, therefore, dependent on symbiotic N 2 fixation also contained elevated concentrations of malate in the xylem sap. When either nitrate or ammonium was supplied, malate concentrations in the xylem sap were low, both for nodulated and non-nodulated plants. Evidence was obtained that the elevated malate concentration of the xylem was derived from amino acids supplied by the phloem. Aspartate was a prominent component of the phloem sap amino acids and, therefore, a potential source of malate. Supplying the roots of intact plants with 13 C-aspartate revealed that malate of the xylem sap was readily labelled under N starvation. A hypothetical scheme is proposed whereby aspartate supplied by the phloem is metabolised in the roots and the products of this metabolism cycled back to the shoot. Under N starvation, aspartate metabolism is diverted from asparagine synthesis to supply N for the synthesis of other amino acids via transaminase activity. The by-product of aspartate transaminase activity, oxaloacetate, is transformed to malate and its export accounts for much of the elevated concentration of malate found in the xylem sap. This mechanism represents a new additional role for malate during mineral N starvation of soybean, beyond that of charge balance.

Symplastic isolation of the sieve element-companion cell complex in the phloem of Ricinus communis and Salix alba stems.

PubMed

van Bel, A J; Kempers, R

1991-12-01

The anatomical and physiological isolation of the sieve element-companion cell complex (se-cc complex) was investigated in stems of Ricinus communis L. and Salix alba L. In Ricinus, the plasmodesmatal frequencies were in the proportions 8∶1∶2∶30, in the order given, at the interfaces between sieve tube-companion cell, sieve tube-phloem parenchyma cell, companion cellphloem parenchyma cell, and phloem parenchyma cellphloem parenchyma cell. The membrane potentials of the se-cc complex and the surrounding phloem-parenchyma cells sharply contrasted: the membrane potential of the se-cc complex was about twice as negative as that of the phloem parenchyma. Lucifer Yellow CH injected into the sieve element or into the companion cell remained within the se-cc complex. Dye introduced into phloem parenchyma only moved (mostly poorly) to other phloem-parenchyma cells. The distribution of the plasmodesmatal frequencies, the differential dye-coupling and the sharp discontinuities in membrane potentials indicate that the se-cc complexes constitute symplast domains in the stem phloem. Symplastic autonomy is discussed as a basic necessity for the functioning of the se-cc complex in the stem.

Elasticity of excised dog lung parenchyma

NASA Technical Reports Server (NTRS)

Vawter, D. L.; Fung, Y. C.; West, J. B.

1978-01-01

An optical-electromechanical system is used to measure the force-deformation behavior of biaxially loaded rectangular slabs of excised dog lung parenchyma. In the course of the study, the effects of time, the consistency of reference lengths and areas, the presence of hysteresis, the necessity of preconditioning, the repeatability of results, the effects of lateral load, the effect of strain rate, the effect of pH, the influence of temperature, and the variations among specimens are considered. A new finding is that there is a change in elastic behavior when the tissue undergoes a compressive strain. When the tissue is in tension, increasing the lateral load decreases the compliance, whereas the opposite is true when compressive strain is present.

Embolism spread in the primary xylem of Polystichum munitum: implications for water transport during seasonal drought.

PubMed

Brodersen, Craig R; Rico, Christopher; Guenni, Orlando; Pittermann, Jarmila

2016-02-01

Xylem network structure and function have been characterized for many woody plants, but less is known about fern xylem, particularly in species endemic to climates where water is a limiting resource for months at a time. We characterized seasonal variability in soil moisture and frond water status in a common perennial fern in the redwood understory of a costal California, and then investigated the consequences of drought-induced embolism on vascular function. Seasonal variability in air temperature and soil water content was minimal, and frond water potential declined slowly over the observational period. Our data show that Polystichum munitum was protected from significant drought-induced hydraulic dysfunction during this growing season because of a combination of cavitation resistant conduits (Air-seeding threshold (ASP) = -1.53 MPa; xylem pressure inducing 50% loss of hydraulic conductivity (P50 ) = -3.02 MPa) and a soil with low moisture variability. High resolution micro-computed tomography (MicroCT) imaging revealed patterns of embolism formation in vivo for the first time in ferns providing insight into the functional status of the xylem network under drought conditions. Together with stomatal conductance measurements, these data suggest that P. munitum is adapted to tolerate drier conditions than what was observed during the growing season. © 2015 John Wiley & Sons Ltd.

Spatial and temporal patterns of xylem sap pH derived from stems and twigs of Populus deltoides L.

Treesearch

Doug Aubrey; Justin Boyles; Laura Krysinsky; Robert Teskey

2011-01-01

Xylem sap pH (pHX) is critical in determining the quantity of inorganic carbon dissolved in xylem solution from gaseous [CO2] measurements. Studies of internal carbon transport have generally assumed that pHX derived from stems and twigs is similar and that pHX remains constant through time; however, no empirical studies have investigated these assumptions. If any of...

In vivo quantification of motion in liver parenchyma and its application in shistosomiasis tissue characterization

NASA Astrophysics Data System (ADS)

Badawi, Ahmed M.; Hashem, Ahmed M.; Youssef, Abou-Bakr M.; Abdel-Wahab, Mohamed F.

1995-03-01

Schistosomiasis is a major problem in Egypt, despite an active control program it is estimated to exist in about 1/3 of the population. Deposition of less functioning fibrous tissues in the liver is the major contributory factor to the hepatic pathology. Fibrous tissues consist of a complex array of connective matrix material and a variety of collagen isotopes. As a result of an increased stromal density (collagen content), the parenchyma became more ectogenic and less elastic (hard). In this study we investigated the effect of cardiac mechanical impulses from the heart and aorta on the kinetics of the liver parenchyma. Under conditions of controlled patient movements and suspended respiration, a 30 frame per second of 588 X 512 ultrasound images (cineloop, 32 pels per cm) are captured from an aTL ultrasound machine then digitized. The image acquisition is triggered by the R wave of the ECG of the patient. The motion that has a forced oscillation form in the liver parenchyma is quantified by tracking of small box (20 - 30 pels) in 16 directions for all the successive 30 frames. The tracking was done using block matching techniques (the max correlation between boxes in time, frequency domains, and the minimum SAD (sum absolute difference) between boxes). The motion is quantified for many regions at different positions within the liver parenchyma for 80 cases of variable degrees of schisto., cirrhotic livers, and for normal livers. The velocity of the tissue is calculated from the displacement (quantified motion), time between frames, and the scan time for the ultrasound scanner. We found that the motion in liver parenchyma is small in the order of very few millimeters, and the attenuation of the mechanical wave for one ECG cycle is higher in the schisto. and cirrhotic livers than in the normal ones. Finally quantification of motion in liver parenchyma due to cardiac impulses under controlled limb movement and respiration may be of value in the characterization of

Moving beyond the cambium necrosis hypothesis of post-fire tree mortality: cavitation and deformation of xylem in forest fires

Treesearch

S.T. Michaletz; E.A. Johnson; M.T. Tyree

2012-01-01

It is widely assumed that post-fire tree mortality results from necrosis of phloem and vascular cambium in stems, despite strong evidence that reduced xylem conductivity also plays an important role. In this study, experiments with Populus balsamifera were used to demonstrate two mechanisms by which heat reduces the hydraulic conductivity of xylem:...

Tissue and cell-specific transcriptomes in cotton reveal the subtleties of gene regulation underlying the diversity of plant secondary cell walls.

PubMed

MacMillan, Colleen P; Birke, Hannah; Chuah, Aaron; Brill, Elizabeth; Tsuji, Yukiko; Ralph, John; Dennis, Elizabeth S; Llewellyn, Danny; Pettolino, Filomena A

2017-07-18

Knowledge of plant secondary cell wall (SCW) regulation and deposition is mainly based on the Arabidopsis model of a 'typical' lignocellulosic SCW. However, SCWs in other plants can vary from this. The SCW of mature cotton seed fibres is highly cellulosic and lacks lignification whereas xylem SCWs are lignocellulosic. We used cotton as a model to study different SCWs and the expression of the genes involved in their formation via RNA deep sequencing and chemical analysis of stem and seed fibre. Transcriptome comparisons from cotton xylem and pith as well as from a developmental series of seed fibres revealed tissue-specific and developmentally regulated expression of several NAC transcription factors some of which are likely to be important as top tier regulators of SCW formation in xylem and/or seed fibre. A so far undescribed hierarchy was identified between the top tier NAC transcription factors SND1-like and NST1/2 in cotton. Key SCW MYB transcription factors, homologs of Arabidopsis MYB46/83, were practically absent in cotton stem xylem. Lack of expression of other lignin-specific MYBs in seed fibre relative to xylem could account for the lack of lignin deposition in seed fibre. Expression of a MYB103 homolog correlated with temporal expression of SCW CesAs and cellulose synthesis in seed fibres. FLAs were highly expressed and may be important structural components of seed fibre SCWs. Finally, we made the unexpected observation that cell walls in the pith of cotton stems contained lignin and had a higher S:G ratio than in xylem, despite that tissue's lacking many of the gene transcripts normally associated with lignin biosynthesis. Our study in cotton confirmed some features of the currently accepted gene regulatory cascade for 'typical' plant SCWs, but also revealed substantial differences, especially with key downstream NACs and MYBs. The lignocellulosic SCW of cotton xylem appears to be achieved differently from that in Arabidopsis. Pith cell walls in

The role of water channel proteins in facilitating recovery of leaf hydraulic conductance from water stress in Populus trichocarpa.

PubMed

Laur, Joan; Hacke, Uwe G

2014-01-01

Gas exchange is constrained by the whole-plant hydraulic conductance (Kplant). Leaves account for an important fraction of Kplant and may therefore represent a major determinant of plant productivity. Leaf hydraulic conductance (Kleaf) decreases with increasing water stress, which is due to xylem embolism in leaf veins and/or the properties of the extra-xylary pathway. Water flow through living tissues is facilitated and regulated by water channel proteins called aquaporins (AQPs). Here we assessed changes in the hydraulic conductance of Populus trichocarpa leaves during a dehydration-rewatering episode. While leaves were highly sensitive to drought, Kleaf recovered only 2 hours after plants were rewatered. Recovery of Kleaf was absent when excised leaves were bench-dried and subsequently xylem-perfused with a solution containing AQP inhibitors. We examined the expression patterns of 12 highly expressed AQP genes during a dehydration-rehydration episode to identify isoforms that may be involved in leaf hydraulic adjustments. Among the AQPs tested, several genes encoding tonoplast intrinsic proteins (TIPs) showed large increases in expression in rehydrated leaves, suggesting that TIPs contribute to reversing drought-induced reductions in Kleaf. TIPs were localized in xylem parenchyma, consistent with a role in facilitating water exchange between xylem vessels and adjacent living cells. Dye uptake experiments suggested that reversible embolism formation in minor leaf veins contributed to the observed changes in Kleaf.

Infection processes of xylem-colonizing pathogenic bacteria: possible explanations for the scarcity of qualitative disease resistance genes against them in crops.

PubMed

Bae, Chungyun; Han, Sang Wook; Song, Yu-Rim; Kim, Bo-Young; Lee, Hyung-Jin; Lee, Je-Min; Yeam, Inhwa; Heu, Sunggi; Oh, Chang-Sik

2015-07-01

Disease resistance against xylem-colonizing pathogenic bacteria in crops. Plant pathogenic bacteria cause destructive diseases in many commercially important crops. Among these bacteria, eight pathogens, Ralstonia solanacearum, Xanthomonas oryzae pv. oryzae, X. campestris pv. campestris, Erwinia amylovora, Pantoea stewartii subsp. stewartii, Clavibacter michiganensis subsp. michiganensis, Pseudomonas syringae pv. actinidiae, and Xylella fastidiosa, infect their host plants through different infection sites and paths and eventually colonize the xylem tissues of their host plants, resulting in wilting symptoms by blocking water flow or necrosis of xylem tissues. Noticeably, only a relatively small number of resistant cultivars in major crops against these vascular bacterial pathogens except X. oryzae pv. oryzae have been found or generated so far, although these pathogens threaten productivity of major crops. In this review, we summarize the lifestyles of major xylem-colonizing bacterial pathogens and then discuss the progress of current research on disease resistance controlled by qualitative disease resistance genes or quantitative trait loci against them. Finally, we propose infection processes of xylem-colonizing bacterial pathogens as one of possible reasons for why so few qualitative disease resistance genes against these pathogens have been developed or identified so far in crops.

Xylem vulnerability to cavitation can be accurately characterised in species with long vessels using a centrifuge method.

PubMed

Tobin, M F; Pratt, R B; Jacobsen, A L; De Guzman, M E

2013-05-01

Vulnerability to cavitation curves describe the decrease in xylem hydraulic conductivity as xylem pressure declines. Several techniques for constructing vulnerability curves use centrifugal force to induce negative xylem pressure in stem or root segments. Centrifuge vulnerability curves constructed for long-vesselled species have been hypothesised to overestimate xylem vulnerability to cavitation due to increased vulnerability of vessels cut open at stem ends that extend to the middle or entirely through segments. We tested two key predictions of this hypothesis: (i) centrifugation induces greater embolism than dehydration in long-vesselled species, and (ii) the proportion of open vessels changes centrifuge vulnerability curves. Centrifuge and dehydration vulnerability curves were compared for a long- and short-vesselled species. The effect of open vessels was tested in four species by comparing centrifuge vulnerability curves for stems of two lengths. Centrifuge and dehydration vulnerability curves agreed well for the long- and short-vesselled species. Centrifuge vulnerability curves constructed using two stem lengths were similar. Also, the distribution of embolism along the length of centrifuged stems matched the theoretical pressure profile induced by centrifugation. We conclude that vulnerability to cavitation can be accurately characterised with vulnerability curves constructed using a centrifuge technique, even in long-vesselled species. © 2012 German Botanical Society and The Royal Botanical Society of the Netherlands.

Scaling of angiosperm xylem structure with safety and efficiency.

PubMed

Hacke, Uwe G; Sperry, John S; Wheeler, James K; Castro, Laura

2006-06-01

We tested the hypothesis that greater cavitation resistance correlates with less total inter-vessel pit area per vessel (the pit area hypothesis) and evaluated a trade-off between cavitation safety and transport efficiency. Fourteen species of diverse growth form (vine, ring- and diffuse-porous tree, shrub) and family affinity were added to published data predominately from the Rosaceae (29 species total). Two types of vulnerability-to-cavitation curves were found. Ring-porous trees and vines showed an abrupt drop in hydraulic conductivity with increasing negative pressure, whereas hydraulic conductivity in diffuse-porous species generally decreased gradually. The ring-porous type curve was not an artifact of the centrifuge method because it was obtained also with the air-injection technique. A safety versus efficiency trade-off was evident when curves were compared across species: for a given pressure, there was a limited range of optimal vulnerability curves. The pit area hypothesis was supported by a strong relationship (r2 = 0.77) between increasing cavitation resistance and diminishing pit membrane area per vessel (A(P)). Small A(P) was associated with small vessel surface area and hence narrow vessel diameter (D) and short vessel length (L)--consistent with an increase in vessel flow resistance with cavitation resistance. This trade-off was amplified at the tissue level by an increase in xylem/vessel area ratio with cavitation resistance. Ring-porous species were more efficient than diffuse-porous species on a vessel basis but not on a xylem basis owing to higher xylem/vessel area ratios in ring-porous anatomy. Across four orders of magnitude, lumen and end-wall resistivities maintained a relatively tight proportionality with a near-optimal mean of 56% of the total vessel resistivity residing in the end-wall. This was consistent with an underlying scaling of L to D(3/2) across species. Pit flow resistance did not increase with cavitation safety, suggesting

Fluctuations of cambial activity in relation to precipitation result in annual rings and intra-annual growth zones of xylem and phloem in teak (Tectona grandis) in Ivory Coast

PubMed Central

Dié, Agathe; Kitin, Peter; Kouamé, François N'Guessan; Van den Bulcke, Jan; Van Acker, Joris; Beeckman, Hans

2012-01-01

Background and Aims Teak forms xylem rings that potentially carry records of carbon sequestration and climate in the tropics. These records are only useful when the structural variations of tree rings and their periodicity of formation are known. Methods The seasonality of ring formation in mature teak trees was examined via correlative analysis of cambial activity, xylem and phloem formation, and climate throughout 1·5 years. Xylem and phloem differentiation were visualized by light microscopy and scanning electron microscopy. Key Results A 3 month dry season resulted in semi-deciduousness, cambial dormancy and formation of annual xylem growth rings (AXGRs). Intra-annual xylem and phloem growth was characterized by variable intensity. Morphometric features of cambium such as cambium thickness and differentiating xylem layers were positively correlated. Cambium thickness was strongly correlated with monthly rainfall (R2 = 0·7535). In all sampled trees, xylem growth zones (XGZs) were formed within the AXGRs during the seasonal development of new foliage. When trees achieved full leaf, the xylem in the new XGZs appeared completely differentiated and functional for water transport. Two phloem growth rings were formed in one growing season. Conclusions The seasonal formation pattern and microstructure of teak xylem suggest that AXGRs and XGZs can be used as proxies for analyses of the tree history and climate at annual and intra-annual resolution. PMID:22805529

Data on xylem sap proteins from Mn- and Fe-deficient tomato plants obtained using shotgun proteomics.

PubMed

Ceballos-Laita, Laura; Gutierrez-Carbonell, Elain; Takahashi, Daisuke; Abadía, Anunciación; Uemura, Matsuo; Abadía, Javier; López-Millán, Ana Flor

2018-04-01

This article contains consolidated proteomic data obtained from xylem sap collected from tomato plants grown in Fe- and Mn-sufficient control, as well as Fe-deficient and Mn-deficient conditions. Data presented here cover proteins identified and quantified by shotgun proteomics and Progenesis LC-MS analyses: proteins identified with at least two peptides and showing changes statistically significant (ANOVA; p ≤ 0.05) and above a biologically relevant selected threshold (fold ≥ 2) between treatments are listed. The comparison between Fe-deficient, Mn-deficient and control xylem sap samples using a multivariate statistical data analysis (Principal Component Analysis, PCA) is also included. Data included in this article are discussed in depth in the research article entitled "Effects of Fe and Mn deficiencies on the protein profiles of tomato ( Solanum lycopersicum) xylem sap as revealed by shotgun analyses" [1]. This dataset is made available to support the cited study as well to extend analyses at a later stage.

How do sharpshooter leafhoppers feed and survive on nutritionally depauperate xylem fluid?

USDA-ARS?s Scientific Manuscript database

Sharpshooters (Cicadellidae: Cicadellinae) are large, tropical and semi-tropical leafhoppers that are unique among all non-sessile hemipterans in ingesting primarily from xylem vessels. This presentation will summarize research on behavioral and physiological adaptations that permit sharpshooters ...

Arabidopsis VASCULAR-RELATED UNKNOWN PROTEIN1 Regulates Xylem Development and Growth by a Conserved Mechanism That Modulates Hormone Signaling1[W][OPEN

PubMed Central

Grienenberger, Etienne; Douglas, Carl J.

2014-01-01

Despite a strict conservation of the vascular tissues in vascular plants (tracheophytes), our understanding of the genetic basis underlying the differentiation of secondary cell wall-containing cells in the xylem of tracheophytes is still far from complete. Using coexpression analysis and phylogenetic conservation across sequenced tracheophyte genomes, we identified a number of Arabidopsis (Arabidopsis thaliana) genes of unknown function whose expression is correlated with secondary cell wall deposition. Among these, the Arabidopsis VASCULAR-RELATED UNKNOWN PROTEIN1 (VUP1) gene encodes a predicted protein of 24 kD with no annotated functional domains but containing domains that are highly conserved in tracheophytes. Here, we show that the VUP1 expression pattern, determined by promoter-β-glucuronidase reporter gene expression, is associated with vascular tissues, while vup1 loss-of-function mutants exhibit collapsed morphology of xylem vessel cells. Constitutive overexpression of VUP1 caused dramatic and pleiotropic developmental defects, including severe dwarfism, dark green leaves, reduced apical dominance, and altered photomorphogenesis, resembling brassinosteroid-deficient mutants. Constitutive overexpression of VUP homologs from multiple tracheophyte species induced similar defects. Whole-genome transcriptome analysis revealed that overexpression of VUP1 represses the expression of many brassinosteroid- and auxin-responsive genes. Additionally, deletion constructs and site-directed mutagenesis were used to identify critical domains and amino acids required for VUP1 function. Altogether, our data suggest a conserved role for VUP1 in regulating secondary wall formation during vascular development by tissue- or cell-specific modulation of hormone signaling pathways. PMID:24567189

Plant xylem hydraulics: What we understand, current research, and future challenges.

PubMed

Venturas, Martin D; Sperry, John S; Hacke, Uwe G

2017-06-01

Herein we review the current state-of-the-art of plant hydraulics in the context of plant physiology, ecology, and evolution, focusing on current and future research opportunities. We explain the physics of water transport in plants and the limits of this transport system, highlighting the relationships between xylem structure and function. We describe the great variety of techniques existing for evaluating xylem resistance to cavitation. We address several methodological issues and their connection with current debates on conduit refilling and exponentially shaped vulnerability curves. We analyze the trade-offs existing between water transport safety and efficiency. We also stress how little information is available on molecular biology of cavitation and the potential role of aquaporins in conduit refilling. Finally, we draw attention to how plant hydraulic traits can be used for modeling stomatal responses to environmental variables and climate change, including drought mortality. © 2017 Institute of Botany, Chinese Academy of Sciences.

Proton-Dependent Coniferin Transport, a Common Major Transport Event in Differentiating Xylem Tissue of Woody Plants1[W

PubMed Central

Tsuyama, Taku; Kawai, Ryo; Shitan, Nobukazu; Matoh, Toru; Sugiyama, Junji; Yoshinaga, Arata; Takabe, Keiji; Fujita, Minoru; Yazaki, Kazufumi

2013-01-01

Lignin biosynthesis is an essential physiological activity of vascular plants if they are to survive under various environmental stresses on land. The biosynthesis of lignin proceeds in the cell wall by polymerization of precursors; the initial step of lignin polymerization is the transportation of lignin monomers from the cytosol to the cell wall, which is critical for lignin formation. There has been much debate on the transported form of the lignin precursor, either as free monolignols or their glucosides. In this study, we performed biochemical analyses to characterize the membrane transport mechanism of lignin precursors using angiosperms, hybrid poplar (Populus sieboldii × Populus grandidentata) and poplar (Populus sieboldii), as well gymnosperms, Japanese cypress (Chamaecyparis obtusa) and pine (Pinus densiflora). Membrane vesicles prepared from differentiating xylem tissues showed clear ATP-dependent transport activity of coniferin, whereas less than 4% of the coniferin transport activity was seen for coniferyl alcohol. Bafilomycin A1 and proton gradient erasers markedly inhibited coniferin transport in hybrid poplar membrane vesicles; in contrast, vanadate had no effect. Cis-inhibition experiments suggested that this transport activity was specific for coniferin. Membrane fractionation of hybrid poplar microsomes demonstrated that transport activity was localized to the tonoplast- and endomembrane-rich fraction. Differentiating xylem of Japanese cypress exhibited almost identical transport properties, suggesting the involvement of a common endomembrane-associated proton/coniferin antiport mechanism in the lignifying tissues of woody plants, both angiosperms and gymnosperms. PMID:23585651

Functional anatomy controls ion distribution in banana leaves: significance of Na+ seclusion at the leaf margins.

PubMed

Shapira, Or; Khadka, Sudha; Israeli, Yair; Shani, Uri; Schwartz, Amnon

2009-05-01

Typical salt stress symptoms appear in banana (Musa sp., cv. 'Grand Nain' AAA) only along the leaf margins. Mineral analysis of the dry matter of plants treated with increasing concentrations of KCl or NaCl revealed significant accumulation of Na+, but not of K+ or Cl(-), in the affected leaf margins. The differential distribution of the three ions suggests that water and ion movement out of the xylem is mostly symplastic and, in contrast to K+ and Cl(-), there exists considerable resistance to the flow of Na+ from the xylem to the adjacent mesophyll and epidermis. The parallel veins of the lamina are enclosed by several layers of bundle sheath parenchyma; in contrast, the large vascular bundle that encircles the entire lamina, and into which the parallel veins merge, lacks a complete bundle sheath. Xylem sap containing a high concentration of Na+ is 'pulled' by water tension from the marginal vein back into the adjacent mesophyll without having to cross a layer of parenchyma tissue. When the marginal vein was dissected from the lamina, the pattern of Na+ distribution in the margins changed markedly. The distinct anatomy of the marginal vein plays a major role in the accumulation of Na+ in the margins, with the latter serving as a 'dumping site' for toxic molecules.

Transcript Profiling Identifies NAC-Domain Genes Involved in Regulating Wall Ingrowth Deposition in Phloem Parenchyma Transfer Cells of Arabidopsis thaliana

PubMed Central

Wu, Yuzhou; Hou, Jiexi; Yu, Fen; Nguyen, Suong T. T.; McCurdy, David W.

2018-01-01

Transfer cells (TCs) play important roles in facilitating enhanced rates of nutrient transport at key apoplasmic/symplasmic junctions along the nutrient acquisition and transport pathways in plants. TCs achieve this capacity by developing elaborate wall ingrowth networks which serve to increase plasma membrane surface area thus increasing the cell's surface area-to-volume ratio to achieve increased flux of nutrients across the plasma membrane. Phloem parenchyma (PP) cells of Arabidopsis leaf veins trans-differentiate to become PP TCs which likely function in a two-step phloem loading mechanism by facilitating unloading of photoassimilates into the apoplasm for subsequent energy-dependent uptake into the sieve element/companion cell (SE/CC) complex. We are using PP TCs in Arabidopsis as a genetic model to identify transcription factors involved in coordinating deposition of the wall ingrowth network. Confocal imaging of pseudo-Schiff propidium iodide-stained tissue revealed different profiles of temporal development of wall ingrowth deposition across maturing cotyledons and juvenile leaves, and a basipetal gradient of deposition across mature adult leaves. RNA-Seq analysis was undertaken to identify differentially expressed genes common to these three different profiles of wall ingrowth deposition. This analysis identified 68 transcription factors up-regulated two-fold or more in at least two of the three experimental comparisons, with six of these transcription factors belonging to Clade III of the NAC-domain family. Phenotypic analysis of these NAC genes using insertional mutants revealed significant reductions in levels of wall ingrowth deposition, particularly in a double mutant of NAC056 and NAC018, as well as compromised sucrose-dependent root growth, indicating impaired capacity for phloem loading. Collectively, these results support the proposition that Clade III members of the NAC-domain family in Arabidopsis play important roles in regulating wall ingrowth

Transcript Profiling Identifies NAC-Domain Genes Involved in Regulating Wall Ingrowth Deposition in Phloem Parenchyma Transfer Cells of Arabidopsis thaliana.

PubMed

Wu, Yuzhou; Hou, Jiexi; Yu, Fen; Nguyen, Suong T T; McCurdy, David W

2018-01-01

Transfer cells (TCs) play important roles in facilitating enhanced rates of nutrient transport at key apoplasmic/symplasmic junctions along the nutrient acquisition and transport pathways in plants. TCs achieve this capacity by developing elaborate wall ingrowth networks which serve to increase plasma membrane surface area thus increasing the cell's surface area-to-volume ratio to achieve increased flux of nutrients across the plasma membrane. Phloem parenchyma (PP) cells of Arabidopsis leaf veins trans -differentiate to become PP TCs which likely function in a two-step phloem loading mechanism by facilitating unloading of photoassimilates into the apoplasm for subsequent energy-dependent uptake into the sieve element/companion cell (SE/CC) complex. We are using PP TCs in Arabidopsis as a genetic model to identify transcription factors involved in coordinating deposition of the wall ingrowth network. Confocal imaging of pseudo-Schiff propidium iodide-stained tissue revealed different profiles of temporal development of wall ingrowth deposition across maturing cotyledons and juvenile leaves, and a basipetal gradient of deposition across mature adult leaves. RNA-Seq analysis was undertaken to identify differentially expressed genes common to these three different profiles of wall ingrowth deposition. This analysis identified 68 transcription factors up-regulated two-fold or more in at least two of the three experimental comparisons, with six of these transcription factors belonging to Clade III of the NAC-domain family. Phenotypic analysis of these NAC genes using insertional mutants revealed significant reductions in levels of wall ingrowth deposition, particularly in a double mutant of NAC056 and NAC018 , as well as compromised sucrose-dependent root growth, indicating impaired capacity for phloem loading. Collectively, these results support the proposition that Clade III members of the NAC-domain family in Arabidopsis play important roles in regulating wall

Evidence for Hydraulic Vulnerability Segmentation and Lack of Xylem Refilling under Tension1[OPEN

PubMed Central

Charrier, Guillaume; Choat, Brendan; Delmas, Chloe E. L.; Domec, Jean-Christophe; King, Andrew; Lenoir, Nicolas

2016-01-01

The vascular system of grapevine (Vitis spp.) has been reported as being highly vulnerable, even though grapevine regularly experiences seasonal drought. Consequently, stomata would remain open below water potentials that would generate a high loss of stem hydraulic conductivity via xylem embolism. This situation would necessitate daily cycles of embolism repair to restore hydraulic function. However, a more parsimonious explanation is that some hydraulic techniques are prone to artifacts in species with long vessels, leading to the overestimation of vulnerability. The aim of this study was to provide an unbiased assessment of (1) the vulnerability to drought-induced embolism in perennial and annual organs and (2) the ability to refill embolized vessels in two Vitis species X-ray micro-computed tomography observations of intact plants indicated that both Vitis vinifera and Vitis riparia were relatively vulnerable, with the pressure inducing 50% loss of stem hydraulic conductivity = −1.7 and −1.3 MPa, respectively. In V. vinifera, both the stem and petiole had similar sigmoidal vulnerability curves but differed in pressure inducing 50% loss of hydraulic conductivity (−1.7 and −1 MPa for stem and petiole, respectively). Refilling was not observed as long as bulk xylem pressure remained negative (e.g. at the apical part of the plants; −0.11 ± 0.02 MPa) and change in percentage loss of conductivity was 0.02% ± 0.01%. However, positive xylem pressure was observed at the basal part of the plant (0.04 ± 0.01 MPa), leading to a recovery of conductance (change in percentage loss of conductivity = −0.24% ± 0.12%). Our findings provide evidence that grapevine is unable to repair embolized xylem vessels under negative pressure, but its hydraulic vulnerability segmentation provides significant protection of the perennial stem. PMID:27613852

Ceratocystis smalleyi colonization of bitternut hickkory and host responses in the xylem

Treesearch

J.-H. Park; J. Juzwik

2014-01-01

Colonization of Carya cordiformis sapwood by Ceratocystis smalleyi and subsequent host defence responses following artificial inoculation were investigated using anatomical and histological techniques. Hyphae of C. smalleyi were observed in all sapwood xylem features confirming the ability of the pathogen to...

Resistance to alveolar shape change limits range of force propagation in lung parenchyma.

PubMed

Ma, Baoshun; Smith, Bradford J; Bates, Jason H T

2015-06-01

We have recently shown that if the lung parenchyma is modeled in 2 dimensions as a network of springs arranged in a pattern of repeating hexagonal cells, the distortional forces around a contracting airway propagate much further from the airway wall than classic continuum theory predicts. In the present study we tested the hypothesis that this occurs because of the negligible shear modulus of a hexagonal spring network. We simulated the narrowing of an airway embedded in a hexagonal network of elastic alveolar walls when the hexagonal cells of the network offered some resistance to a change in shape. We found that as the forces resisting shape change approach about 10% of the forces resisting length change of an individual spring the range of distortional force propagation in the spring network fell of rapidly as in an elastic continuum. We repeated these investigations in a 3-dimensional spring network composed of space-filling polyhedral cells and found similar results. This suggests that force propagation away from a point of local parenchymal distortion also falls off rapidly in real lung tissue. Copyright © 2015 Elsevier B.V. All rights reserved.

Drought tolerance, xylem sap abscisic acid and stomatal conductance during soil drying: a comparison of young plants of four temperate deciduous angiosperms.

PubMed

Loewenstein, Nancy J.; Pallardy, Stephen G.

1998-07-01

Patterns of water relations, xylem sap abscisic acid (ABA) concentration ([ABA]) and stomatal aperture were compared in drought-sensitive black walnut (Juglans nigra L.) and black willow (Salix nigra Marsh.), less drought-sensitive sugar maple (Acer saccharum Marsh.) and drought-tolerant white oak (Quercus alba L.). Strong correlations among reduction in predawn water potential, increase in xylem sap [ABA] and stomatal closure were observed in all species. Stomatal response was more highly correlated with xylem [ABA] than with ABA flux. Xylem sap pH and ion concentrations appeared not to play a major role in the stomatal response of these species. Stomata were more sensitive to relative changes in [ABA] in drought-sensitive black walnut and black willow than in sugar maple and white oak. In the early stages of drought, increased [ABA] in the xylem sap of black walnut and black willow was probably of root origin and provided a signal to the shoot of the water status of the roots. In sugar maple and white oak, leaf water potential declined with the onset of stomatal closure, so that stomatal closure also may have occurred in response to the change in leaf water potential.

Evidence for xylem adaptations to drought in ancient Cordaites of the Carboniferous

NASA Astrophysics Data System (ADS)

Medeiros, J. S.; Hewins, C.; Serbet, R.; Taylor, T. N.; Taylor, E. L.; Ward, J. K.

2013-12-01

Ancient land plants faced the same challenges to growth and survival as modern land plants, including the need to resist xylem embolisms imposed by drought in order to main water supply to leaves. Cordaites, considered to be ancestors of the conifers, were some of the first trees on Earth and are often described as the most drought resistant plants in the North American landscape from the Late Missisipian (~320 MYA) to the early Permian (~250 MYA). Cordaites were common in both mires and dry uplands, however, suggesting considerable variation in drought tolerance, but neither the extent of this variation nor the particular xylem features associated with dryland habitats have been previously examined. We measured xylem anatomical traits including tracheid diameter (D) and wall thickness (t), for Cordaites roots and stems from three sites in Central North America: What Cheer IA, Sahara IL and Lewis Creek KY. From these data we calculated mechanical strength (t/b), which was used to estimate vulnerability to drought embolism (P50) based on comparisons with modern plants. In addition, we used the model of Wilson et al. (2008) to calculate the specific conductivity (Ksp), a measure of xylem water transport capacity. D and Ksp of Cordaites stems were similar to that typical of modern conifers but t/b tended to be lower. However, Cordaites exhibited significant variation in D, t, Ksp and t/b across sites. Stem P50 estimated from comparisons with modern plants ranged from approximately -4 at Lewis Creek to as low as -7 MPa at Sahara. We also found differences between stems and roots for Cordaites. Compared to stems, roots had larger D and higher Ksp, but lower t and t/b, resulting in a P50 ranging from approximately -2 to -4 MPa. In the roots of Sahara Cordaites, lower t/b in roots was a result of both significantly larger conduits and significantly thinner conduit walls compared to stems. Thus, hydraulic segmentation in Cordaites could have facilitated their survival in

Investigating differences in the root to shoot transfer and xylem sap solubility of organic compounds between zucchini, squash and soybean using a pressure chamber method.

PubMed

Garvin, Naho; Doucette, William J; White, Jason C

2015-07-01

A pressure chamber method was used to examine differences in the root to shoot transfer and xylem sap solubility of caffeine (log Kow=-0.07), triclocarban (log Kow=3.5-4.2) and endosulfan (log Kow=3.8-4.8) for zucchini (cucurbita pepo ssp pepo), squash (cucurbita pepo ssp ovifera), and soybean (glycine max L.). Transpiration stream concentration factors (TSCF) for caffeine (TSCF=0.8) were statistically equivalent for all plant species. However, for the more hydrophobic endosulfan and triclocarban, the TSCF values for zucchini (TSCF=0.6 and 0.4, respectively) were 3 and 10 times greater than the soybean and squash (TSCF=0.2 and 0.05, respectively). The difference in TSCF values was examined by comparing the measured solubilities of caffeine, endosulfan and triclocarban in deionized water to those in soybean and zucchini xylem saps using a modified shake flask method. The measured solubility of organic contaminants in xylem sap has not previously been reported. Caffeine solubilities in the xylem saps of soybean and zucchini were statistically equal to deionized water (21500mgL(-1)) while endosulfan and triclocarban solubilities in the zucchini xylem sap were significantly greater (0.43 and 0.21mgL(-1), respectively) than that of the soybean xylem sap (0.31 and 0.11mgL(-1), respectively) and deionized water (0.34 and 0.11mgL(-1), respectively). This suggests that the enhanced root to shoot transfer of hydrophobic organics reported for zucchini is partly due to increased solubility in the xylem sap. Further xylem sap characterization is needed to determine the mechanism of solubility enhancement. Copyright © 2014 Elsevier Ltd. All rights reserved.

In vivo Visualization of the Water-refilling Process in Xylem Vessels Using X-ray Micro-imaging

PubMed Central

Lee, Sang-Joon; Kim, Yangmin

2008-01-01

Background and Aims Xylem vessels containing gases (embolized) must be refilled with water if they are to resume transport of water through the plant, so refilling is of great importance for the maintenance of water balance in plants. However, the refilling process is poorly understood because of inadequate examination methods. Simultaneous measurements of plant anatomy and vessel refilling are essential to elucidate the mechanisms involved. In the present work, a new technique based on phase-contrast X-ray imaging is presented that visualizes, in vivo and in real time, both xylem anatomy and refilling of embolized vessels. Methods With the synchrotron X-ray micro-imaging technique, the refilling of xylem vessels of leaves and a stem of Phyllostachys bambusoides with water is demonstrated under different conditions. The technique employs phase contrast imaging of X-ray beams, which are transformed into visible light and are photographed by a charge coupled device camera. X-ray images were captured consecutively at every 0·5 s with an exposure time of 10 ms. Key Results The interface (meniscus) between the water and gas phases in refilling the xylem vessels is displayed. During refilling, the rising menisci in embolized vessels showed repetitive flow, i.e. they temporarily stopped at the end walls of the vessel elements while gas bubbles were removed. The meniscus then passed through the end wall at a faster rate than the speed of flow in the main vessels. In the light, the speed of refilling in a specific vessel was slower than that in the dark, but this rate increased again after repeated periods in darkness. Conclusions Real-time, non-destructive X-ray micro-imaging is an important, useful and novel technique to study the relationship between xylem structure and the refilling of embolized vessels in intact plants. It provides new insight into understanding the mechanisms of water transport and the refilling of embolized vessels, which are not understood well

Xylem Resin in the Resistance of the Pinaceae to Bark Beetles

Treesearch

Richard H. Smith

1972-01-01

Xylem resin of Pinaceae is closely linked with their resistance and suseptibility to tree-killing bark beetles. This review of the literature on attacking adults suggests that all three resistance mechanisms proposed by Painter -- preference, antibiosis, and tolerance -- are active in this relationship: preference by attraction, repellency, and synergism; antibiosis...

Leaf vein xylem conduit diameter influences susceptibility to embolism and hydraulic decline

USDA-ARS?s Scientific Manuscript database

Ecosystems worldwide are facing increasingly severe and prolonged droughts during which hydraulic failure from drought-induced embolism can lead to organ or whole plant death. Understanding the determinants of xylem failure across species is critical especially in leaves, the engine of plant growth....

BOREAS RSS-17 Xylem Flux Density Measurements at the SSA-OBS Site

NASA Technical Reports Server (NTRS)

Zimmerman, Reiner; Way, JoBea; McDonald, Kyle; Nickeson, Jaime (Editor); Hall, Forrest G. (Editor); Smith, David E. (Technical Monitor)

2000-01-01

As part of its efforts to determine environmental and phenological states from radar imagery, the Boreal Ecosystem-Atmosphere Study (BOREAS) Remote Sensing Science (RSS)-17 team collected in situ tree xylem flow measurements for one growing season on five Picea mariana (black spruce) trees. The data were collected to obtain information on the temporal and spatial variability in water uptake by trees in the Southern Study Area-Old Black Spruce (SSA-OBS) stand in the BOREAS SSA. Temporally, the data were collected in 30-minute intervals for 120 days from 31 May 1994 until 27 September 1994. The data are stored in tabular ASCII files. The xylem flux data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

Water transport properties of the grape (V. vinifera L.) pedicel during fruit development: Insights into xylem anatomy and function using microtomography

USDA-ARS?s Scientific Manuscript database

Xylem flow into the fruit decline at the onset of ripening (i.e. veraison) in grapes, and current literature suggests that there is an increase in hydraulic resistance in the pedicel at this time. However, it is unknown how pedicel hydraulic properties change developmentally in relation to xylem an...

Resistance to Dutch Elm Disease Reduces Presence of Xylem Endophytic Fungi in Elms (Ulmus spp.)

PubMed Central

Martín, Juan A.; Witzell, Johanna; Blumenstein, Kathrin; Rozpedowska, Elzbieta; Helander, Marjo; Sieber, Thomas N.; Gil, Luis

2013-01-01

Efforts to introduce pathogen resistance into landscape tree species by breeding may have unintended consequences for fungal diversity. To address this issue, we compared the frequency and diversity of endophytic fungi and defensive phenolic metabolites in elm (Ulmus spp.) trees with genotypes known to differ in resistance to Dutch elm disease. Our results indicate that resistant U. minor and U. pumila genotypes exhibit a lower frequency and diversity of fungal endophytes in the xylem than susceptible U. minor genotypes. However, resistant and susceptible genotypes showed a similar frequency and diversity of endophytes in the leaves and bark. The resistant and susceptible genotypes could be discriminated on the basis of the phenolic profile of the xylem, but not on basis of phenolics in the leaves or bark. As the Dutch elm disease pathogen develops within xylem tissues, the defensive chemistry of resistant elm genotypes thus appears to be one of the factors that may limit colonization by both the pathogen and endophytes. We discuss a potential trade-off between the benefits of breeding resistance into tree species, versus concomitant losses of fungal endophytes and the ecosystem services they provide. PMID:23468900

Response pattern of amino compounds in phloem and xylem of trees to soil drought depends on drought intensity and root symbiosis.

PubMed

Liu, X-P; Gong, C-M; Fan, Y-Y; Eiblmeier, M; Zhao, Z; Han, G; Rennenberg, H

2013-01-01

This study aimed to identify drought-mediated differences in amino nitrogen (N) composition and content of xylem and phloem in trees having different symbiotic N(2)-fixing bacteria. Under controlled water availability, 1-year-old seedlings of Robinia pseudoacacia (nodules with Rhizobium), Hippophae rhamnoides (symbiosis with Frankia) and Buddleja alternifolia (no such root symbiosis) were exposed to control, medium drought and severe drought, corresponding soil water content of 70-75%, 45-50% and 30-35% of field capacity, respectively. Composition and content of amino compounds in xylem sap and phloem exudates were analysed as a measure of N nutrition. Drought strongly reduced biomass accumulation in all species, but amino N content in xylem and phloem remained unaffected only in R. pseudoacacia. In H. rhamnoides and B. alternifolia, amino N in phloem remained constant, but increased in xylem of both species in response to drought. There were differences in composition of amino compounds in xylem and phloem of the three species in response to drought. Proline concentrations in long-distance transport pathways of all three species were very low, below the limit of detection in phloem of H. rhamnoides and in phloem and xylem of B. alternifolia. Apparently, drought-mediated changes in N composition were much more connected with species-specific changes in C:N ratios. Irrespective of soil water content, the two species with root symbioses did not show similar features for the different types of symbiosis, neither in N composition nor in N content. There was no immediate correlation between symbiotic N fixation and drought-mediated changes in amino N in the transport pathways. © 2012 German Botanical Society and The Royal Botanical Society of the Netherlands.

A Plumber's-Eye View of Xylem Water Transport in Woody Plants

ERIC Educational Resources Information Center

Martinez-Vilalta, Jordi; Pinol, Josep

2004-01-01

We present a practical for university-level students aimed at measuring and comparing xylem hydraulic properties of co-existing plant species. After sampling branches of several woody species in the field, their main hydraulic properties were measured using a simple set-up. Hydraulic conductivity ("K[subscript h]") was calculated as the ratio…

Are flowers vulnerable to xylem cavitation during drought?

PubMed

Zhang, Feng-Ping; Brodribb, Timothy J

2017-05-17

Water stress is known to cause xylem cavitation in the leaves, roots and stems of plants, but little is known about the vulnerability of flowers to xylem damage during drought. This is an important gap in our understanding of how and when plants become damaged by water stress. Here we address fundamental questions about if and when flowers suffer cavitation damage, using a new technique of cavitation imaging to resolve the timing of cavitation in water-stressed flower petals compared with neighbouring leaves. Leaves and flowers from a sample of two herbaceous and two woody eudicots were exposed to a severe water stress while the spatial and temporal propagation of embolism through veins was recorded. Although in most cases water potentials inducing 50% embolism of herbaceous flower veins were more negative than neighbouring leaves, there was no significant difference between the average vulnerability of leaves and petals of herbaceous species. In both woody species, petals were more vulnerable to cavitation than leaves, in one case by more than 3 MPa. Early cavitation and subsequent damage of flowers in the two woody species would thus be expected to precede leaf damage during drought. Similar cavitation thresholds of flowers and leaves in the herb sample suggest that cavitation during water shortage in these species will occur simultaneously among aerial tissues. Species-specific differences in the cavitation thresholds of petals provide a new axis of variation that may explain contrasting flowering ecology among plant species. © 2017 The Author(s).

Leaf morphology of 40 evergreen and deciduous broadleaved subtropical tree species and relationships to functional ecophysiological traits.

PubMed

Kröber, W; Heklau, H; Bruelheide, H

2015-03-01

We explored potential of morphological and anatomical leaf traits for predicting ecophysiological key functions in subtropical trees. We asked whether the ecophysiological parameters stomatal conductance and xylem cavitation vulnerability could be predicted from microscopy leaf traits. We investigated 21 deciduous and 19 evergreen subtropical tree species, using individuals of the same age and from the same environment in the Biodiversity-Ecosystem Functioning experiment at Jiangxi (BEF-China). Information-theoretic linear model selection was used to identify the best combination of morphological and anatomical predictors for ecophysiological functions. Leaf anatomy and morphology strongly depended on leaf habit. Evergreen species tended to have thicker leaves, thicker spongy and palisade mesophyll, more palisade mesophyll layers and a thicker subepidermis. Over 50% of all evergreen species had leaves with multi-layered palisade parenchyma, while only one deciduous species (Koelreuteria bipinnata) had this. Interactions with leaf habit were also included in best multi-predictor models for stomatal conductance (gs ) and xylem cavitation vulnerability. In addition, maximum gs was positively related to log ratio of palisade to spongy mesophyll thickness. Vapour pressure deficit (vpd) for maximum gs increased with the log ratio of palisade to spongy mesophyll thickness in species having leaves with papillae. In contrast, maximum specific hydraulic conductivity and xylem pressure at which 50% loss of maximum specific xylem hydraulic conductivity occurred (Ψ50 ) were best predicted by leaf habit and density of spongy parenchyma. Evergreen species had lower Ψ50 values and lower maximum xylem hydraulic conductivities. As hydraulic leaf and wood characteristics were reflected in structural leaf traits, there is high potential for identifying further linkages between morphological and anatomical leaf traits and ecophysiological responses. © 2014 German Botanical Society

Altitudinal variations of ground tissue and xylem tissue in terminal shoot of woody species: implications for treeline formation.

PubMed

Chen, Hong; Wang, Haiyang; Liu, Yanfang; Dong, Li

2013-01-01

1. The terminal shoot (or current-year shoot), as one of the most active parts on a woody plant, is a basic unit determining plant height and is potentially influenced by a variety of environmental factors. It has been predicted that tissues amount and their allocation in plant stems may play a critical role in determining plant size in alpine regions. The primary structure in terminal shoots is a key to our understanding treeline formation. The existing theories on treeline formation, however, are still largely lacking of evidence at the species level, much less from anatomy for the terminal shoot. 2. The primary structures within terminal shoot were measured quantitatively for 100 species from four elevation zones along the eastern slope of Gongga Mountain, southwestern China; one group was sampled from above the treeline. An allometric approach was employed to examine scaling relationships interspecifically, and a principal components analysis (PCA) was performed to test the relation among primary xylem, ground tissue, species growth form and altitude. 3. The results showed that xylem tissue size was closely correlated with ground tissue size isometrically across species, while undergoing significant y- or/and x-intercept shift in response to altitudinal belts. Further, a conspicuous characteristic of terminal shoot was its allocation of contrasting tissues between primary xylem and ground tissues with increasing elevation. The result of the PCA showed correlations between anatomical variation, species growth form/height classes and environment. 4. The current study presents a comparative assessment of the allocation of tissue in terminal shoot across phylogenically and ecologically diverse species, and analyzes tissue, function and climate associations with plant growth forms and height classes among species. The interspecific connection between primary xylem ratio and plant size along an elevation gradient suggests the importance of primary xylem in explaining

Altitudinal Variations of Ground Tissue and Xylem Tissue in Terminal Shoot of Woody Species: Implications for Treeline Formation

PubMed Central

Chen, Hong; Wang, Haiyang; Liu, Yanfang; Dong, Li

2013-01-01

1. The terminal shoot (or current-year shoot), as one of the most active parts on a woody plant, is a basic unit determining plant height and is potentially influenced by a variety of environmental factors. It has been predicted that tissues amount and their allocation in plant stems may play a critical role in determining plant size in alpine regions. The primary structure in terminal shoots is a key to our understanding treeline formation. The existing theories on treeline formation, however, are still largely lacking of evidence at the species level, much less from anatomy for the terminal shoot. 2. The primary structures within terminal shoot were measured quantitatively for 100 species from four elevation zones along the eastern slope of Gongga Mountain, southwestern China; one group was sampled from above the treeline. An allometric approach was employed to examine scaling relationships interspecifically, and a principal components analysis (PCA) was performed to test the relation among primary xylem, ground tissue, species growth form and altitude. 3. The results showed that xylem tissue size was closely correlated with ground tissue size isometrically across species, while undergoing significant y- or/and x-intercept shift in response to altitudinal belts. Further, a conspicuous characteristic of terminal shoot was its allocation of contrasting tissues between primary xylem and ground tissues with increasing elevation. The result of the PCA showed correlations between anatomical variation, species growth form/height classes and environment. 4. The current study presents a comparative assessment of the allocation of tissue in terminal shoot across phylogenically and ecologically diverse species, and analyzes tissue, function and climate associations with plant growth forms and height classes among species. The interspecific connection between primary xylem ratio and plant size along an elevation gradient suggests the importance of primary xylem in explaining

Unique growth strategy in the Earth's first trees revealed in silicified fossil trunks from China.

PubMed

Xu, Hong-He; Berry, Christopher M; Stein, William E; Wang, Yi; Tang, Peng; Fu, Qiang

2017-11-07

Cladoxylopsida included the earliest large trees that formed critical components of globally transformative pioneering forest ecosystems in the Mid- and early Late Devonian (ca. 393-372 Ma). Well-known cladoxylopsid fossils include the up to ∼1-m-diameter sandstone casts known as Eospermatopteris from Middle Devonian strata of New York State. Cladoxylopsid trunk structure comprised a more-or-less distinct cylinder of numerous separate cauline xylem strands connected internally with a network of medullary xylem strands and, near the base, externally with downward-growing roots, all embedded within parenchyma. However, the means by which this complex vascular system was able to grow to a large diameter is unknown. We demonstrate-based on exceptional, up to ∼70-cm-diameter silicified fossil trunks with extensive preservation of cellular anatomy from the early Late Devonian (Frasnian, ca. 374 Ma) of Xinjiang, China-that trunk expansion is associated with a cylindrical zone of diffuse secondary growth within ground and cortical parenchyma and with production of a large amount of wood containing both rays and growth increments concentrically around individual xylem strands by normal cambia. The xylem system accommodates expansion by tearing of individual strand interconnections during secondary development. This mode of growth seems indeterminate, capable of producing trees of large size and, despite some unique features, invites comparison with secondary development in some living monocots. Understanding the structure and growth of cladoxylopsids informs analysis of canopy competition within early forests with the potential to drive global processes. Published under the PNAS license.

Cadmium uptake and xylem loading are active processes in the hyperaccumulator Sedum alfredii.

PubMed

Lu, Ling-li; Tian, Sheng-ke; Yang, Xiao-e; Li, Ting-qiang; He, Zhen-li

2009-04-01

Sedum alfredii is a well known cadmium (Cd) hyperaccumulator native to China; however, the mechanism behind its hyperaccumulation of Cd is not fully understood. Through several hydroponic experiments, characteristics of Cd uptake and translocation were investigated in the hyperaccumulating ecotype (HE) of S. alfredii in comparison with its non-hyperaccumulating ecotype (NHE). The results showed that at Cd level of 10 microM measured Cd uptake in HE was 3-4 times higher than the implied Cd uptake calculated from transpiration rate. Furthermore, inhibition of transpiration rate in the HE has no essential effect on Cd accumulation in shoots of the plants. Low temperature treatment (4 degrees C) significantly inhibited Cd uptake and reduced upward translocation of Cd to shoots for 9 times in HE plants, whereas no such effect was observed in NHE. Cadmium concentration was 3-4-fold higher in xylem sap of HE, as compared with that in external uptake solution, whereas opposite results were obtained for NHE. Cadmium concentration in xylem sap of HE was significantly reduced by the addition of metabolic inhibitors, carbonyl cyanide m-chlorophenylhydrazone (CCCP) and 2,4-dinitrophenol (DNP), in the uptake solutions, whereas no such effect was noted in NHE. These results suggest that Cd uptake and translocation is an active process in plants of HE S. alfredii, symplastic pathway rather than apoplastic bypass contributes greatly to root uptake, xylem loading and translocation of Cd to the shoots of HE, in comparison with the NHE plants.

Xylogenesis in zinnia (Zinnia elegans) cell cultures: unravelling the regulatory steps in a complex developmental programmed cell death event.

PubMed

Iakimova, Elena T; Woltering, Ernst J

2017-04-01

Physiological and molecular studies support the view that xylogenesis can largely be determined as a specific form of vacuolar programmed cell death (PCD). The studies in xylogenic zinnia cell culture have led to many breakthroughs in xylogenesis research and provided a background for investigations in other experimental models in vitro and in planta . This review discusses the most essential earlier and recent findings on the regulation of xylem elements differentiation and PCD in zinnia and other xylogenic systems. Xylogenesis (the formation of water conducting vascular tissue) is a paradigm of plant developmental PCD. The xylem vessels are composed of fused tracheary elements (TEs)-dead, hollow cells with patterned lignified secondary cell walls. They result from the differentiation of the procambium and cambium cells and undergo cell death to become functional post-mortem. The TE differentiation proceeds through a well-coordinated sequence of events in which differentiation and the programmed cellular demise are intimately connected. For years a classical experimental model for studies on xylogenesis was the xylogenic zinnia (Zinnia elegans) cell culture derived from leaf mesophyll cells that, upon induction by cytokinin and auxin, transdifferentiate into TEs. This cell system has been proven very efficient for investigations on the regulatory components of xylem differentiation which has led to many discoveries on the mechanisms of xylogenesis. The knowledge gained from this system has potentiated studies in other xylogenic cultures in vitro and in planta. The present review summarises the previous and latest findings on the hormonal and biochemical signalling, metabolic pathways and molecular and gene determinants underlying the regulation of xylem vessels differentiation in zinnia cell culture. Highlighted are breakthroughs achieved through the use of xylogenic systems from other species and newly introduced tools and analytical approaches to study the

What HR-CT imaging can teach us about xylem structure and function

USDA-ARS?s Scientific Manuscript database

It is well established that plant xylem is composed of a complex and interconnected system of vascular elements, but little is known about how the three-dimensional (3D) organization of this network influences properties such as plant hydraulics (Tyree & Zimmermann, 2002), and few studies have measu...

Hydraulic safety margins and embolism reversal in stems and leaves: why are conifers and angiosperms so different?

PubMed

Johnson, Daniel M; McCulloh, Katherine A; Woodruff, David R; Meinzer, Frederick C

2012-10-01

Angiosperm and coniferous tree species utilize a continuum of hydraulic strategies. Hydraulic safety margins (defined as differences between naturally occurring xylem pressures and pressures that would cause hydraulic dysfunction, or differences between pressures resulting in loss of hydraulic function in adjacent organs (e.g., stems vs. leaves) tend to be much greater in conifers than angiosperms and serve to prevent stem embolism. However, conifers tend to experience embolism more frequently in leaves and roots than angiosperms. Embolism repair is thought to occur by active transport of sugars into empty conduits followed by passive water movement. The most likely source of sugar for refilling is from nonstructural carbohydrate depolymerization in nearby parenchyma cells. Compared to angiosperms, conifers tend to have little parenchyma or nonstructural carbohydrates in their wood. The ability to rapidly repair embolisms may rely on having nearby parenchyma cells, which could explain the need for greater safety margins in conifer wood as compared to angiosperms. The frequent embolisms that occur in the distal portions of conifers are readily repaired, perhaps due to the abundant parenchyma in leaves and roots, and these distal tissues may act as hydraulic circuit breakers that prevent tension-induced embolisms in the attached stems. Frequent embolisms in conifer leaves may also be due to weaker stomatal response to changes in ambient humidity. Although there is a continuum of hydraulic strategies among woody plants, there appear to be two distinct 'behaviors' at the extremes: (1) embolism prevention and (2) embolism occurrence and subsequent repair. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Mixed xylem and phloem sap ingestion in sheath-feeders as normal dietary behavior: Evidence from the leafhopper Scaphoideus titanus.

PubMed

Chuche, Julien; Sauvion, Nicolas; Thiéry, Denis

2017-10-01

In phytophagous piercing-sucking insects, salivary sheath-feeding species are often described as xylem- or phloem-sap feeding specialists. Because these two food sources have very different characteristics, two feeding tactics are often associated with this supposed specialization. Studying the feeding behavior of insects provides substantial information on their biology, ecology, and evolution. Furthermore, study of feeding behavior is of primary importance to elucidate the transmission ability of insects that act as vectors of plant pathogens. In this study, we compared the durations of ingestion performed in xylem versus phloem by a leafhopper species, Scaphoideus titanus Ball, 1932. This was done by characterizing and statistically analyzing electrical signals recorded using the electropenetrography technique, derived from the feeding behaviors of males and females. We identified three groups of S. titanus based on their feeding behavior: 1) a group that reached the phloem quickly and probed for a longer time in phloem tissue than the other groups, 2) a group that reached the xylem quickly and probed for a longer time in xylem tissue than the other groups, and 3) a group where individuals did not ingest much sap. In addition, the numbers and durations of waveforms representing ingestion of xylem and phloem saps differed significantly depending on the sex of the leafhopper, indicating that the two sexes exhibit different feeding behaviors. Males had longer phloem ingestion events than did females, which indicates that males are greater phloem feeders than females. These differences are discussed, specifically in relation to hypotheses about evolution of sap feeding and phytoplasma transmission from plant to plant. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of combined drought and heavy metal stresses on xylem structure and hydraulic conductivity in red maple (Acer rubrum L.).

PubMed

de Silva, Nayana Dilini Gardiyehewa; Cholewa, Ewa; Ryser, Peter

2012-10-01

The effects of heavy metal stress, drought stress, and their combination on xylem structure in red maple (Acer rubrum) seedlings were investigated in an outdoor pot experiment. As metal-contaminated substrate, a mixture of 1.5% slag with sand was used, with Ni, Cu, Co, and Cr as the main contaminants. Plants grown on contaminated substrate had increased leaf metal concentrations. The two stresses reduced plant growth in an additive manner. The effects of metal and drought stresses on xylem characteristics were similar to each other, with a reduced proportion of xylem tissue, reduced conduit density in stems, and reduced conduit size in the roots. This resulted, in both stems and roots, in reductions in hydraulic conductance, xylem-specific conductivity, and leaf-specific conductivity. The similarity of the responses to the two stresses suggests that the plants' response to metals was actually a drought response, probably due to the reduced water uptake capacity of the metal-exposed roots. The only plant responses specific to metal stress were decreasing trends of stomatal density and chlorophyll content. In conclusion, the exposure to metals aggravates water stress in an additive manner, making the plants more vulnerable to drought.

Disruption of the rice nitrate transporter OsNPF2.2 hinders root-to-shoot nitrate transport and vascular development

PubMed Central

Li, Yuge; Ouyang, Jie; Wang, Ya-Yun; Hu, Rui; Xia, Kuaifei; Duan, Jun; Wang, Yaqin; Tsay, Yi-Fang; Zhang, Mingyong

2015-01-01

Plants have evolved to express some members of the nitrate transporter 1/peptide transporter family (NPF) to uptake and transport nitrate. However, little is known of the physiological and functional roles of this family in rice (Oryza sativa L.). Here, we characterized the vascular specific transporter OsNPF2.2. Functional analysis using cDNA-injected Xenopus laevis oocytes revealed that OsNPF2.2 is a low-affinity, pH-dependent nitrate transporter. Use of a green fluorescent protein tagged OsNPF2.2 showed that the transporter is located in the plasma membrane in the rice protoplast. Expression analysis showed that OsNPF2.2 is nitrate inducible and is mainly expressed in parenchyma cells around the xylem. Disruption of OsNPF2.2 increased nitrate concentration in the shoot xylem exudate when nitrate was supplied after a deprivation period; this result suggests that OsNPF2.2 may participate in unloading nitrate from the xylem. Under steady-state nitrate supply, the osnpf2.2 mutants maintained high levels of nitrate in the roots and low shoot:root nitrate ratios; this observation suggests that OsNPF2.2 is involved in root-to-shoot nitrate transport. Mutation of OsNPF2.2 also caused abnormal vasculature and retarded plant growth and development. Our findings demonstrate that OsNPF2.2 can unload nitrate from the xylem to affect the root-to-shoot nitrate transport and plant development. PMID:25923512

Catecholamine transport in isolated lung parenchyma of pig

PubMed Central

Goldie, Roy G.; Paterson, James W.

1982-01-01

1 Lung parenchyma strips of the pig incubated at 37°C with [3H]-(-)-noradrenaline ([3H]-NA) or [3H]-(±)-isoprenaline ([3H]-Iso), accumulated radioactivity via saturable, high affinity uptake processes. Apparent saturation constants (Km) for [3H]-NA and [3H]-Iso were 1.34 × 10-6 M and 1.63 × 10-6 M respectively, while apparent transport maxima (Vmax) were 4.86 and 1.63 × 10-9 mol min-1 g-1 respectively. 2 Cellular accumulation of radioactivity from radiolabelled catecholamines was greatly reduced by lowering the temperature to 7°C, pretreatment with ouabain (100 μM), phentolamine (15 μM) or phenoxybenzamine (80 μM). However, accumulation of radioactivity derived from (3H]-NA was inhibited selectively by cocaine (10 μM) and desipramine (1 μM), while normetanephrine (80 μM) and 3-O-methylisoprenaline (50 μM) caused much greater reductions in cellular radioactivity from [3H]-Iso than from (3H]-NA. Taken together with information from kinetic studies, the results indicate that these amines are transported by separate uptake processes. 3 Cocaine (50 μM) which selectively reduced [3H]-NA transport, had no significant effect on the sensitivity (EC50) of isolated parenchyma lung strips of the pig to the contractile effects of cumulative concentrations of NA. The catechol-O-methyl transferase (COMT) inhibitor, U-0521 (60 μM), also failed to alter the potency of NA, while normetanephrine (80 μM) caused a 2 fold decrease in potency. 4 Phentolamine (15 μM), which reduced the cellular accumulation of radioactivity derived from [3H]-Iso by 64%, caused a small potentiation of Iso-induced relaxations of porcine lung strips. Normetanephrine (80 μM) and 3-O-methylisoprenaline (50 μM), which also depressed the accumulation of cellular radioactivity from [3H]-Iso by > 50%, caused rightward shifts in Iso concentration-effect curves as a result of β-adrenoceptor blockade. In sharp contrast, cortisol (80 μM) and U-0521 (60 μM), which caused smaller reductions in the

Relationships between xylem vessel characteristics, calculated axial hydraulic conductance and size-controlling capacity of peach rootstocks

PubMed Central

Tombesi, Sergio; Johnson, R. Scott; Day, Kevin R.; DeJong, Theodore M.

2010-01-01

Background and Aims Previous studies indicate that the size-controlling capacity of peach rootstocks is associated with reductions of scion water potential during mid-day that are caused by the reduced hydraulic conductance of the rootstock. Thus, shoot growth appears to be reduced by decreases in stem water potential. The aim of this study was to investigate the mechanism of reduced hydraulic conductance in size-controlling peach rootstocks. Methods Anatomical measurements (diameter and frequency) of xylem vessels were determined in shoots, trunks and roots of three contrasting peach rootstocks grown as trees, each with different size-controlling characteristics: ‘Nemaguard’ (vigorous), ‘P30-135’ (intermediate vigour) and ‘K146-43’ (substantially dwarfing). Based on anatomical measurements, the theoretical axial xylem conductance of each tissue type and rootstock genotype was calculated via the Poiseuille–Hagen law. Key Results Larger vessel dimensions were found in the vigorous rootstock (‘Nemaguard’) than in the most dwarfing one (‘K146-43’) whereas vessels of ‘P30-135’ had intermediate dimensions. The density of vessels per xylem area in ‘Nemaguard’ was also less than in ‘P30-135’and ‘K146-43’. These characteristics resulted in different estimated hydraulic conductance among rootstocks: ‘Nemaguard’ had higher theoretical values followed by ‘P30-135’ and ‘K146-43’. Conclusions These data indicate that phenotypic differences in xylem anatomical characteristics of rootstock genotypes appear to influence hydraulic conductance capacity directly, and therefore may be the main determinant of dwarfing in these peach rootstocks. PMID:19939979

Static and dynamic bending has minor effects on xylem hydraulics of conifer branches (Picea abies, Pinus sylvestris)

PubMed Central

Mayr, Stefan; Bertel, Clara; Dämon, Birgit; Beikircher, Barbara

2014-01-01

The xylem hydraulic efficiency and safety is usually measured on mechanically unstressed samples, although trees may be exposed to combined hydraulic and mechanical stress in the field. We analysed changes in hydraulic conductivity and vulnerability to drought-induced embolism during static bending of Picea abies and Pinus sylvestris branches as well as the effect of dynamic bending on the vulnerability. We hypothesized this mechanical stress to substantially impair xylem hydraulics. Intense static bending caused an only small decrease in hydraulic conductance (−19.5 ± 2.4% in P. abies) but no shift in vulnerability thresholds. Dynamic bending caused a 0.4 and 0.8 MPa decrease of the water potential at 50 and 88% loss of conductivity in P. sylvestris, but did not affect vulnerability thresholds in P. abies. With respect to applied extreme bending radii, effects on plant hydraulics were surprisingly small and are thus probably of minor eco-physiological importance. More importantly, results indicate that available xylem hydraulic analyses (of conifers) sufficiently reflect plant hydraulics under field conditions. PMID:24697679

Ultrasonic emissions during ice nucleation and propagation in plant xylem.

PubMed

Charrier, Guillaume; Pramsohler, Manuel; Charra-Vaskou, Katline; Saudreau, Marc; Améglio, Thierry; Neuner, Gilbert; Mayr, Stefan

2015-08-01

Ultrasonic acoustic emission analysis enables nondestructive monitoring of damage in dehydrating or freezing plant xylem. We studied acoustic emissions (AE) in freezing stems during ice nucleation and propagation, by combining acoustic and infrared thermography techniques and controlling the ice nucleation point. Ultrasonic activity in freezing samples of Picea abies showed two distinct phases: the first on ice nucleation and propagation (up to 50 AE s(-1) ; reversely proportional to the distance to ice nucleation point), and the second (up to 2.5 AE s(-1) ) after dissipation of the exothermal heat. Identical patterns were observed in other conifer and angiosperm species. The complex AE patterns are explained by the low water potential of ice at the ice-liquid interface, which induced numerous and strong signals. Ice propagation velocities were estimated via AE (during the first phase) and infrared thermography. Acoustic activity ceased before the second phase probably because the exothermal heating and the volume expansion of ice caused decreasing tensions. Results indicate cavitation events at the ice front leading to AE. Ultrasonic emission analysis enabled new insights into the complex process of xylem freezing and might be used to monitor ice propagation in natura. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

First extensive microscopic study of butternut defense mechanisms following inoculation with the canker pathogen Ophiognomonia clavigignenti-juglandacearum reveals compartmentalization of tissue damage.

PubMed

Rioux, Danny; Blais, Martine; Nadeau-Thibodeau, Nicholas; Lagacé, Marie; DesRochers, Pierre; Klimaszewska, Krystyna; Bernier, Louis

2018-05-11

Ophiognomonia clavigignenti-juglandacearum (Oc-j) endangers the survival of butternut (Juglans cinerea) throughout its native range. While screening for disease resistance, we found that artificial inoculations of 48 butternut seedlings with Oc-j induced the expression of external symptoms, but only after a period of dormancy. Before dormancy, compartmentalized tissues such as necrophylactic periderms (NPs) and xylem reaction zones (RZs) contributed to limiting pathogen invasion. Phenols were regularly detected in RZs, often in continuity with NPs during wound closure, and confocal microscopy revealed their presence in parenchyma cells, vessel plugs and cell walls. Vessels were blocked with tyloses and gels, particularly those present in RZs. Suberin was also detected in cells formed over the affected xylem by the callus at the inoculation point, in a few tylosis walls, and in longitudinal tubes that formed near NPs. Following dormancy, in all inoculated seedlings but one, defensive barriers were breached by Oc-j and then additional ones were produced in response to this new invasion. The results of this histopathological study indicate that trees inoculated in selection programs to test butternut canker resistance should go through at least one period of dormancy and that asymptomatic individuals should be dissected to better assess how they defend themselves against Oc-j.

Interpreting the Climatic Effects on Xylem Functional Traits in Two Mediterranean Oak Species: The Role of Extreme Climatic Events.

PubMed

Rita, Angelo; Borghetti, Marco; Todaro, Luigi; Saracino, Antonio

2016-01-01

In the Mediterranean region, the widely predicted rise in temperature, change in the precipitation pattern, and increase in the frequency of extreme climatic events are expected to alter the shape of ecological communities and to affect plant physiological processes that regulate ecosystem functioning. Although change in the mean values are important, there is increasing evidence that plant distribution, survival, and productivity respond to extremes rather than to the average climatic condition. The present study aims to assess the effects of both mean and extreme climatic conditions on radial growth and functional anatomical traits using long-term tree-ring time series of two co-existing Quercus spp. from a drought-prone site in Southern Italy. In particular, this is the first attempt to apply the Generalized Additive Model for Location, Scale, and Shape (GAMLSS) technique and Bayesian modeling procedures to xylem traits data set, with the aim of (i) detecting non-linear long-term responses to climate and (ii) exploring relationships between climate extreme and xylem traits variability in terms of probability of occurrence. This study demonstrates the usefulness of long-term xylem trait chronologies as records of environmental conditions at annual resolution. Statistical analyses revealed that most of the variability in tree-ring width and specific hydraulic conductivity might be explained by cambial age. Additionally, results highlighted appreciable relationships between xylem traits and climate variability more than tree-ring width, supporting also the evidence that the plant hydraulic traits are closely linked to local climate extremes rather than average climatic conditions. We reported that the probability of extreme departure in specific hydraulic conductivity (Ks) rises at extreme values of Standardized Precipitation Index (SPI). Therefore, changing frequency or intensity of extreme events might overcome the adaptive limits of vascular transport, resulting

Interpreting the Climatic Effects on Xylem Functional Traits in Two Mediterranean Oak Species: The Role of Extreme Climatic Events

PubMed Central

Rita, Angelo; Borghetti, Marco; Todaro, Luigi; Saracino, Antonio

2016-01-01

In the Mediterranean region, the widely predicted rise in temperature, change in the precipitation pattern, and increase in the frequency of extreme climatic events are expected to alter the shape of ecological communities and to affect plant physiological processes that regulate ecosystem functioning. Although change in the mean values are important, there is increasing evidence that plant distribution, survival, and productivity respond to extremes rather than to the average climatic condition. The present study aims to assess the effects of both mean and extreme climatic conditions on radial growth and functional anatomical traits using long-term tree-ring time series of two co-existing Quercus spp. from a drought-prone site in Southern Italy. In particular, this is the first attempt to apply the Generalized Additive Model for Location, Scale, and Shape (GAMLSS) technique and Bayesian modeling procedures to xylem traits data set, with the aim of (i) detecting non-linear long-term responses to climate and (ii) exploring relationships between climate extreme and xylem traits variability in terms of probability of occurrence. This study demonstrates the usefulness of long-term xylem trait chronologies as records of environmental conditions at annual resolution. Statistical analyses revealed that most of the variability in tree-ring width and specific hydraulic conductivity might be explained by cambial age. Additionally, results highlighted appreciable relationships between xylem traits and climate variability more than tree-ring width, supporting also the evidence that the plant hydraulic traits are closely linked to local climate extremes rather than average climatic conditions. We reported that the probability of extreme departure in specific hydraulic conductivity (Ks) rises at extreme values of Standardized Precipitation Index (SPI). Therefore, changing frequency or intensity of extreme events might overcome the adaptive limits of vascular transport, resulting

Chronological Sequence of Leaf Phenology, Xylem and Phloem Formation and Sap Flow of Quercus pubescens from Abandoned Karst Grasslands

PubMed Central

Lavrič, Martina; Eler, Klemen; Ferlan, Mitja; Vodnik, Dominik; Gričar, Jožica

2017-01-01

Intra-annual variations in leaf development, radial growth, including the phloem part, and sap flow have rarely been studied in deciduous trees from drought-prone environments. In order to understand better the chronological order and temporal course of these processes, we monitored leaf phenology, xylem and phloem formation and sap flow in Quercus pubescens from abandoned karst grasslands in Slovenia during the growing season of 2014. We found that the initial earlywood vessel formation started before bud opening at the beginning of April. Buds started to open in the second half of April and full leaf unfolding occurred by the end of May. LAI values increased correspondingly with leaf development. About 28% of xylem and 22% of phloem annual increment were formed by the time of bud break. Initial earlywood vessels were fully lignified and ready for water transport, indicating that they are essential to provide hydraulic conductivity for axial water flow during leaf development. Sap flow became active and increasing contemporarily with leaf development and LAI values. Similar early spring patterns of xylem sap flow and LAI denoted that water transport in oaks broadly followed canopy leaf area development. In the initial 3 weeks of radial growth, phloem growth preceded that of xylem, indicating its priority over xylem at the beginning of the growing season. This may be related to the fact that after bud break, the developing foliage is a very large sink for carbohydrates but, at the same time, represents a small transpirational area. Whether the interdependence of the chronological sequence of the studied processes is fixed in Q. pubescens needs to be confirmed with more data and several years of analyses, although the ‘correct sequence’ of processes is essential for synchronized plant performance and response to environmental stress. PMID:28321232

Subtle volume differences in brain parenchyma of children surviving medulloblastoma

NASA Astrophysics Data System (ADS)

Reddick, Wilburn E.; Mulhern, Raymond K.; Elkin, T. David; Glass, John O.; Langston, James W.

1998-07-01

The overriding incentive for accurate quantification of the functional status of children treated for brain tumors emerges from the clinician's desire to balance the efficacy and chronic toxicity of therapies used for the developing child. A hybrid combination of the Kohonen self-organizing map (SOM) for segmentation and a multilayer backpropagation (MLBP) neural network for classification removes observer variances to yield a reproducible and accurate identification of tissues. A group of 17 volunteers and 77 patients from a larger ongoing study of pediatric patients with brain tumors were used to investigate the sensitivity of segmented volumes to determine atrophy as measured by two radiologists. The atrophy study revealed a significant relationship for brain parenchyma, CSF and white matter volumes with atrophy while gray matter had no significant relationship. Brain parenchyma and subsequently white matter were found to be inversely proportional to increasing grades of atrophy. An additional study compared fifteen age-matched patients treated with irradiation and surgery with patients treated with surgery alone. The age-matched study of patients demonstrated that brain volumes in the irradiated patients were significantly decreased compared to those treated with surgery alone. Further investigation of this difference revealed that white matter was significantly reduced while gray matter was relatively unchanged.

Soil water and xylem chemistry in declining sugar maple stands in Pennsylvania

Treesearch

David R. DeWalle; Bryan R. Swistock; William E. Sharpe

1999-01-01

Evidence is accumulating that decline of sugar maple, Acer saccharum Marsh., in northern Pennsylvania may be related to overall site fertility as reflected in the chemistry of soil water and bolewood xylem. In this paper we discuss factors related to varying site fertility, including effects of soil liming, past glacialion, topographic position and...

Temporal dynamics of stem expansion and contraction in savanna trees: withdrawal and recharge of stored water.

PubMed

Scholz, Fabian C; Bucci, Sandra J; Goldstein, Guillermo; Meinzer, Frederick C; Franco, Augusto C; Miralles-Wilhelm, Fernando

2008-03-01

Relationships between diel changes in stem expansion and contraction and discharge and refilling of stem water storage tissues were studied in six dominant Neotropical savanna (cerrado) tree species from central Brazil. Two stem tissues were studied, the active xylem or sapwood and the living tissues located between the cambium and the cork, made up predominantly of parenchyma cells (outer parenchyma). Outer parenchyma and sapwood density ranged from 320 to 410 kg m(-3) and from 420 to 620 kg m(-3), respectively, depending on the species. The denser sapwood tissues exhibited smaller relative changes in cross-sectional area per unit change in water potential compared with the outer parenchyma. Despite undergoing smaller relative changes in cross-sectional area, the sapwood released about 3.5 times as much stored water for a given change in area as the outer parenchyma. Cross-sectional area decreased earlier in the morning in the outer parenchyma than in the sapwood with lag times up to 30 min for most species. The relatively small lag time between dimensional changes of the two tissues suggested that they were hydraulically well connected. The initial morning increase in basal sap flow lagged about 10 to 130 min behind that of branch sap flow. Species-specific lag times between morning declines in branch and main stem cross-sectional area were a function of relative stem water storage capacity, which ranged from 16 to 31% of total diurnal water loss. Reliance on stored water to temporarily replace transpirational losses is one of the homeostatic mechanisms that constrain the magnitude of leaf water deficits in cerrado trees.

Invasion of xylem of mature tree stems by Phytophthora ramorum and P. kernoviae

Treesearch

Anna Brown; Clive Brasier

2008-01-01

The aetiology and frequency of Phytophthoras in discoloured xylem tissue beneath phloem lesions was investigated in a range of broadleaved trees infected with P. ramorum, P. kernoviae and several other Phytophthoras. Isolation was attempted from the inner surface of 81, 6 x 4 cm sterilised...

Are needles of Pinus pinaster more vulnerable to xylem embolism than branches? New insights from X-ray computed tomography.

PubMed

Bouche, Pauline S; Delzon, Sylvain; Choat, Brendan; Badel, Eric; Brodribb, Timothy J; Burlett, Regis; Cochard, Hervé; Charra-Vaskou, Katline; Lavigne, Bruno; Li, Shan; Mayr, Stefan; Morris, Hugh; Torres-Ruiz, José M; Zufferey, Vivian; Jansen, Steven

2016-04-01

Plants can be highly segmented organisms with an independently redundant design of organs. In the context of plant hydraulics, leaves may be less embolism resistant than stems, allowing hydraulic failure to be restricted to distal organs that can be readily replaced. We quantified drought-induced embolism in needles and stems of Pinus pinaster using high-resolution computed tomography (HRCT). HRCT observations of needles were compared with the rehydration kinetics method to estimate the contribution of extra-xylary pathways to declining hydraulic conductance. High-resolution computed tomography images indicated that the pressure inducing 50% of embolized tracheids was similar between needle and stem xylem (P50 needle xylem  = -3.62 MPa, P50 stem xylem  = -3.88 MPa). Tracheids in both organs showed no difference in torus overlap of bordered pits. However, estimations of the pressure inducing 50% loss of hydraulic conductance at the whole needle level by the rehydration kinetics method were significantly higher (P50 needle  = -1.71 MPa) than P50 needle xylem derived from HRCT. The vulnerability segmentation hypothesis appears to be valid only when considering hydraulic failure at the entire needle level, including extra-xylary pathways. Our findings suggest that native embolism in needles is limited and highlight the importance of imaging techniques for vulnerability curves. © 2015 John Wiley & Sons Ltd.

Test of the 'glymphatic' hypothesis demonstrates diffusive and aquaporin-4-independent solute transport in rodent brain parenchyma.

PubMed

Smith, Alex J; Yao, Xiaoming; Dix, James A; Jin, Byung-Ju; Verkman, Alan S

2017-08-21

Transport of solutes through brain involves diffusion and convection. The importance of convective flow in the subarachnoid and paravascular spaces has long been recognized; a recently proposed 'glymphatic' clearance mechanism additionally suggests that aquaporin-4 (AQP4) water channels facilitate convective transport through brain parenchyma. Here, the major experimental underpinnings of the glymphatic mechanism were re-examined by measurements of solute movement in mouse brain following intracisternal or intraparenchymal solute injection. We found that: (i) transport of fluorescent dextrans in brain parenchyma depended on dextran size in a manner consistent with diffusive rather than convective transport; (ii) transport of dextrans in the parenchymal extracellular space, measured by 2-photon fluorescence recovery after photobleaching, was not affected just after cardiorespiratory arrest; and (iii) Aqp4 gene deletion did not impair transport of fluorescent solutes from sub-arachnoid space to brain in mice or rats. Our results do not support the proposed glymphatic mechanism of convective solute transport in brain parenchyma.

Test of the 'glymphatic' hypothesis demonstrates diffusive and aquaporin-4-independent solute transport in rodent brain parenchyma

PubMed Central

Yao, Xiaoming; Dix, James A; Jin, Byung-Ju

2017-01-01

Transport of solutes through brain involves diffusion and convection. The importance of convective flow in the subarachnoid and paravascular spaces has long been recognized; a recently proposed ‘glymphatic’ clearance mechanism additionally suggests that aquaporin-4 (AQP4) water channels facilitate convective transport through brain parenchyma. Here, the major experimental underpinnings of the glymphatic mechanism were re-examined by measurements of solute movement in mouse brain following intracisternal or intraparenchymal solute injection. We found that: (i) transport of fluorescent dextrans in brain parenchyma depended on dextran size in a manner consistent with diffusive rather than convective transport; (ii) transport of dextrans in the parenchymal extracellular space, measured by 2-photon fluorescence recovery after photobleaching, was not affected just after cardiorespiratory arrest; and (iii) Aqp4 gene deletion did not impair transport of fluorescent solutes from sub-arachnoid space to brain in mice or rats. Our results do not support the proposed glymphatic mechanism of convective solute transport in brain parenchyma. PMID:28826498

Control of xylem Na+ loading and transport to the shoot in rice and barley as a determinant of differential salinity stress tolerance.

PubMed

Ishikawa, Tetsuya; Shabala, Sergey

2018-05-15

Control of xylem Na + loading has often been named as the essential components of salinity tolerance mechanism. However, it is less clear to what extent the difference in this trait may determine differential salinity tolerance between species. In this study barley (Hordeum vulgare L. cv. CM72) and rice (Oryza sativa L. cv Dongjin) plants were grown under two levels of salinity. Na + and K + concentrations in the xylem sap, and shoot and root tissues were measured at different time points after stress onset. Salt-exposed rice plants prevented xylem Na + loading for several days, but failed to control this process in the longer term, ultimately resulting in a massive Na + shoot loading. Barley plants quickly increased xylem Na + concentration and its delivery to the shoot (most likely for the purpose of osmotic adjustment) but were able to reduce this process later on, keeping most of accumulated Na + in the root, thus maintaining non-toxic shoot Na + level. Rice plants increased shoot K + concentration, while barley plants maintained higher root K + concentration. Control of xylem Na + loading is remarkably different between rice and barley; this difference may differentiate the extent of the salinity tolerance between species. This trait should be investigated in more details to be used in the breeding programs aimed to improve salinity tolerance in crops. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Metabolic Profiling of Xylem Sap from Pierce’s Disease Resistant and Susceptible Grapevines

USDA-ARS?s Scientific Manuscript database

Pierce’s Disease (PD) of grapevines is caused by a gram-negative, xylem-limited bacterium Xylella fastidiosa (Xf). All Vitis vinifera-based cultivars are highly susceptible to Xf infection. However, some grape species from the southern United States such as V. arizonica, V. Shuttleworthii, and Musca...

Stomatal regulation based on competition for water, stochastic rainfall, and xylem hydraulic vulnerability - a new theoretical model

NASA Astrophysics Data System (ADS)

Lu, Y.; Duursma, R.; Farrior, C.; Medlyn, B. E.

2016-12-01

Stomata control the exchange of soil water for atmospheric CO2, which is one of the most important resource trade-offs for plants. This trade-off has been studied a lot but not in the context of competition. Based on the theory of evolutionarily stable strategy, we search for the uninvadable (or the ESS) response of stomatal conductance to soil water content under stochastic rainfall, with which the dominant plant population should never be invaded by any rare mutants in the water competition due to a higher fitness. In this study, we define the fitness as the difference between the long-term average photosynthetic carbon gain and a carbon cost of stomatal opening. This cost has traditionally been considered an unknown constant. Here we extend this framework by assuming it as the energy required for xylem embolism refilling. With regard to the refilling process, we explore 2 questions 1) to what extent the embolized xylem vessels can be repaired via refilling; and 2) whether this refilling is immediate or has a time delay following the formation of xylem embolism. We compare various assumptions in a total of 5 scenarios and find that the ESS exists only if the xylem damage can be repaired completely. Then, with this ESS, we estimate annual vegetation photosynthesis and water consumption and compare them with empirical results. In conclusion, this study provides a different insight from the existing empirical and mechanistic models as well as the theoretical models based on the optimization theory. In addition, as the model result is a simple quantitative relation between stomatal conductance and soil water content, it can be easily incorporated into other vegetation function models.

Polyphenols in ceratocystis minor infected Pinus Taeda: fungal metabolites, phloem, and xylem phenols

Treesearch

R.W. Hemingway; G.W. McGraw; S.J. Barras

1977-01-01

Since Ceratocystis minor is central to the death of pines infested by southern pine beetles, changes in polyphenols of infected loblolly pine were examined with regard to accumulation of fungal metabolites and changes in concentrations of fungitoxic and fungistatic phloem and xylem constitutents. C. minor grown in liquid culture...

Polyphenols in Ceratocystis minor infected Pinus taeda: fungal metabolites, phloem and xylem phenols

Treesearch

Richard W. Hemingway; Gerald W. McGraw; Stanley J. Barras

1977-01-01

Since Ceratocystis minor is central to the death of pines infested by southern pine beetles, changes in polyphenols of infected loblolly pine were examined with regard to accumulation of fungal metabolites and changes in concentrations of fungitoxic and fungistatic phloem and xylem constitutents. C. minor grown in liquid culture...

Root-to-shoot Cd translocation via the xylem is the major process determining shoot and grain cadmium accumulation in rice

PubMed Central

Uraguchi, Shimpei; Mori, Shinsuke; Kuramata, Masato; Kawasaki, Akira; Arao, Tomohito; Ishikawa, Satoru

2009-01-01

Physiological properties involved in divergent cadmium (Cd) accumulation among rice genotypes were characterized using the indica cultivar ‘Habataki’ (high Cd in grains) and the japonica cultivar ‘Sasanishiki’ (low Cd in grains). Time-dependence and concentration-dependence of symplastic Cd absorption in roots were revealed not to be responsible for the different Cd accumulation between the two cultivars because root Cd uptake was not greater in the Cd-accumulating cultivar ‘Habataki’ compared with ‘Sasanishiki’. On the other hand, rapid and greater root-to-shoot Cd translocation was observed in ‘Habataki’, which could be mediated by higher abilities in xylem loading of Cd and transpiration rate as a driving force. To verify whether different abilities in xylem-mediated shoot-to-root translocation generally account for the genotypic variation in shoot Cd accumulation in rice, the world rice core collection, consisting of 69 accessions which covers the genetic diversity of almost 32 000 accessions of cultivated rice, was used. The results showed strong correlation between Cd levels in xylem sap and shoots and grains among the 69 rice accessions. Overall, the results presented in this study revealed that the root-to-shoot Cd translocation via the xylem is the major and common physiological process determining the Cd accumulation level in shoots and grains of rice plants. PMID:19401409

Improving xylem hydraulic conductivity measurements by correcting the error caused by passive water uptake.

PubMed

Torres-Ruiz, José M; Sperry, John S; Fernández, José E

2012-10-01

Xylem hydraulic conductivity (K) is typically defined as K = F/(P/L), where F is the flow rate through a xylem segment associated with an applied pressure gradient (P/L) along the segment. This definition assumes a linear flow-pressure relationship with a flow intercept (F(0)) of zero. While linearity is typically the case, there is often a non-zero F(0) that persists in the absence of leaks or evaporation and is caused by passive uptake of water by the sample. In this study, we determined the consequences of failing to account for non-zero F(0) for both K measurements and the use of K to estimate the vulnerability to xylem cavitation. We generated vulnerability curves for olive root samples (Olea europaea) by the centrifuge technique, measuring a maximally accurate reference K(ref) as the slope of a four-point F vs P/L relationship. The K(ref) was compared with three more rapid ways of estimating K. When F(0) was assumed to be zero, K was significantly under-estimated (average of -81.4 ± 4.7%), especially when K(ref) was low. Vulnerability curves derived from these under-estimated K values overestimated the vulnerability to cavitation. When non-zero F(0) was taken into account, whether it was measured or estimated, more accurate K values (relative to K(ref)) were obtained, and vulnerability curves indicated greater resistance to cavitation. We recommend accounting for non-zero F(0) for obtaining accurate estimates of K and cavitation resistance in hydraulic studies. Copyright © Physiologia Plantarum 2012.

Variations in xylem embolism susceptibility under drought between intact saplings of three walnut species.

PubMed

Knipfer, Thorsten; Barrios-Masias, Felipe H; Cuneo, Italo F; Bouda, Martin; Albuquerque, Caetano P; Brodersen, Craig R; Kluepfel, Daniel A; McElrone, Andrew J

2018-05-30

A germplasm collection containing varied Juglans genotypes holds potential to improve drought resistance of plant materials for commercial production. We used X-ray computed microtomography to evaluate stem xylem embolism susceptibility/repair in relation to vessel anatomical features (size, arrangement, connectivity and pit characteristics) in 2-year-old saplings of three Juglans species. In vivo analysis revealed interspecific variations in embolism susceptibility among Juglans microcarpa, J. hindsii (both native to arid habitats) and J. ailantifolia (native to mesic habitats). Stem xylem of J. microcarpa was more resistant to drought-induced embolism as compared with J. hindsii and J. ailantifolia (differences in embolism susceptibility among older and current year xylem were not detected in any species). Variations in most vessel anatomical traits were negligible among the three species; however, we detected substantial interspecific differences in intervessel pit characteristics. As compared with J. hindsii and J. ailantifolia, low embolism susceptibility in J. microcarpa was associated with smaller pit size in larger diameter vessels, a smaller area of the shared vessel wall occupied by pits, lower pit frequency and no changes in pit characteristics as vessel diameters increased. Changes in amount of embolized vessels following 40 days of re-watering were minor in intact saplings of all three species highlighting that an embolism repair mechanism did not contribute to drought recovery. In conclusion, our data indicate that interspecific variations in drought-induced embolism susceptibility are associated with species-specific pit characteristics, and these traits may provide a future target for breeding efforts aimed at selecting walnut germplasm with improved drought resistance.

EGFRvIII-specific chimeric antigen receptor T cells migrate to and kill tumor deposits infiltrating the brain parenchyma in an invasive xenograft model of glioblastoma.

PubMed

Miao, Hongsheng; Choi, Bryan D; Suryadevara, Carter M; Sanchez-Perez, Luis; Yang, Shicheng; De Leon, Gabriel; Sayour, Elias J; McLendon, Roger; Herndon, James E; Healy, Patrick; Archer, Gary E; Bigner, Darell D; Johnson, Laura A; Sampson, John H

2014-01-01

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults and is uniformly lethal. T-cell-based immunotherapy offers a promising platform for treatment given its potential to specifically target tumor tissue while sparing the normal brain. However, the diffuse and infiltrative nature of these tumors in the brain parenchyma may pose an exceptional hurdle to successful immunotherapy in patients. Areas of invasive tumor are thought to reside behind an intact blood brain barrier, isolating them from effective immunosurveillance and thereby predisposing the development of "immunologically silent" tumor peninsulas. Therefore, it remains unclear if adoptively transferred T cells can migrate to and mediate regression in areas of invasive GBM. One barrier has been the lack of a preclinical mouse model that accurately recapitulates the growth patterns of human GBM in vivo. Here, we demonstrate that D-270 MG xenografts exhibit the classical features of GBM and produce the diffuse and invasive tumors seen in patients. Using this model, we designed experiments to assess whether T cells expressing third-generation chimeric antigen receptors (CARs) targeting the tumor-specific mutation of the epidermal growth factor receptor, EGFRvIII, would localize to and treat invasive intracerebral GBM. EGFRvIII-targeted CAR (EGFRvIII+ CAR) T cells demonstrated in vitro EGFRvIII antigen-specific recognition and reactivity to the D-270 MG cell line, which naturally expresses EGFRvIII. Moreover, when administered systemically, EGFRvIII+ CAR T cells localized to areas of invasive tumor, suppressed tumor growth, and enhanced survival of mice with established intracranial D-270 MG tumors. Together, these data demonstrate that systemically administered T cells are capable of migrating to the invasive edges of GBM to mediate antitumor efficacy and tumor regression.

Xylem anisotropy and water transport--a model for the double sawcut experiment

Treesearch

Paul J. Schulte; David G. Costa

2010-01-01

Early experiments with overlapping cuts to the stems of trees demonstrated that lateral flow within the stem must be possible to allow such trees to maintain water flow to their leaves. We present a mathematical approach to considering lateral flow in stems by treating the xylem as an anisotropic medium for flow and develop an expression of its conductivity in the form...

Vascular Cell Induction Culture System Using Arabidopsis Leaves (VISUAL) Reveals the Sequential Differentiation of Sieve Element-Like Cells.

PubMed

Kondo, Yuki; Nurani, Alif Meem; Saito, Chieko; Ichihashi, Yasunori; Saito, Masato; Yamazaki, Kyoko; Mitsuda, Nobutaka; Ohme-Takagi, Masaru; Fukuda, Hiroo

2016-06-01

Cell differentiation is a complex process involving multiple steps, from initial cell fate specification to final differentiation. Procambial/cambial cells, which act as vascular stem cells, differentiate into both xylem and phloem cells during vascular development. Recent studies have identified regulatory cascades for xylem differentiation. However, the molecular mechanism underlying phloem differentiation is largely unexplored due to technical challenges. Here, we established an ectopic induction system for phloem differentiation named Vascular Cell Induction Culture System Using Arabidopsis Leaves (VISUAL). Our results verified similarities between VISUAL-induced Arabidopsis thaliana phloem cells and in vivo sieve elements. We performed network analysis using transcriptome data with VISUAL to dissect the processes underlying phloem differentiation, eventually identifying a factor involved in the regulation of the master transcription factor gene APL Thus, our culture system opens up new avenues not only for genetic studies of phloem differentiation, but also for future investigations of multidirectional differentiation from vascular stem cells. © 2016 American Society of Plant Biologists. All rights reserved.

Understanding the role of the cytoskeleton in wood formation in angiosperm trees: hybrid aspen (Populus tremula x P. tremuloides) as the model species.

PubMed

Chaffey, Nigel; Barlow, Peter; Sundberg, Björn

2002-03-01

The involvement of microfilaments and microtubules in the development of the radial and axial components of secondary xylem (wood) in hybrid aspen (Populus tremula L. x P. tremuloides Michx.) was studied by indirect immunofluorescent localization techniques. In addition to cambial cells, the differentiated cell types considered were early- and late-wood vessel elements, axial parenchyma, normal-wood fibers and gelatinous fibers, and contact and isolation ray cells. Microfilaments were rare in ray cambial cells, but were abundant and axially arranged in their derivatives once cell elongation had begun, and persisted in that orientation in mature ray cells. Microfilaments were axially arranged in fusiform cambial cells and persisted in that orientation in all xylem derivatives of those cells. Microtubules were randomly oriented in ray and fusiform cells of the cambial zone. Dense arrays of parallel-aligned microtubules were oriented near axially in the developing gelatinous fibers, but at a wide range of angles in normal-wood fibers. Ellipses of microfilaments were associated with pit development in fiber cells and isolation ray cells. Rings of co-localized microtubules and microfilaments were associated with developing inter-vessel bordered pits and vessel-contact ray cell contact pits, and, in the case of bordered pits, these rings decreased in diameter as the over-arching pit border increased in size. Although only microtubules were seen at the periphery of the perforation plate of vessel elements, a prominent meshwork of microfilaments overlaid the perforation plate itself. A consensus view of the roles of the cytoskeleton during wood formation in angiosperm trees is presented.

Lung parenchyma at maturity is influenced by postnatal growth but not by moderate preterm birth in sheep.

PubMed

Maritz, Gert; Probyn, Megan; De Matteo, Robert; Snibson, Ken; Harding, Richard

2008-01-01

We have recently shown that moderate preterm birth, in the absence of respiratory support, altered the structure of lung parenchyma in young lambs, but the long-term effects are unknown. To determine whether structural changes persist to maturity, and whether postnatal growth affects lung structure at maturity in sheep. At approximately 1.2 years after birth, lung parenchyma of sheep born 14 days before term (n = 7) was stereologically compared with that of controls born at term (n = 8, term approx. 146 days). Preterm birth per se had no significant effect on lung volume, alveolar number and size, and thicknesses of the alveolar walls and blood-gas barrier. After combining the preterm and term groups, we examined the effects of postnatal growth rates on lung parenchyma. Slower-growing sheep (SG; n = 7: 4 preterm, 3 term) were compared with faster-growing sheep (FG; n = 8: 3 preterm, 5 term). At approximately 1.2 years, the right lung volume, relative to body weight, was significantly lower in SG than FG sheep (p < 0.05) and alveolar number was significantly lower by approximately 44%. The total alveolar internal surface area of the right lung of SG sheep was 38% smaller than in FG sheep; it was also significantly lower when related to both lung and body weight. Our data suggest that moderate preterm birth does not cause persistent alterations in lung parenchyma. However, slow postnatal growth in low-birth-weight sheep results in smaller lungs with fewer alveoli and a lower alveolar surface area relative to body weight. Copyright (c) 2007 S. Karger AG, Basel.

Transgenic poplars with reduced lignin show impaired xylem conductivity, growth efficiency and survival

Treesearch

Steven L. Voelker; Barbara Lachenbruch; Frederick C. Meinzer; Peter Kitin; Steven H. Strauss

2011-01-01

We studied xylem anatomy and hydraulic architecture in 14 transgenic insertion events and a control line of hybrid poplar (Populus spp.) that varied in lignin content. Transgenic events had different levels of down-regulation of two genes encoding 4-coumarate:coenzyme A ligase (4CL). Two-year-old trees were characterized after...

High-resolution confocal imaging of wall ingrowth deposition in plant transfer cells: Semi-quantitative analysis of phloem parenchyma transfer cell development in leaf minor veins of Arabidopsis.

PubMed

Nguyen, Suong T T; McCurdy, David W

2015-04-23

Transfer cells (TCs) are trans-differentiated versions of existing cell types designed to facilitate enhanced membrane transport of nutrients at symplasmic/apoplasmic interfaces. This transport capacity is conferred by intricate wall ingrowths deposited secondarily on the inner face of the primary cell wall, hence promoting the potential trans-membrane flux of solutes and consequently assigning TCs as having key roles in plant growth and productivity. However, TCs are typically positioned deep within tissues and have been studied mostly by electron microscopy. Recent advances in fluorophore labelling of plant cell walls using a modified pseudo-Schiff-propidium iodide (mPS-PI) staining procedure in combination with high-resolution confocal microscopy have allowed visualization of cellular details of individual tissue layers in whole mounts, hence enabling study of tissue and cellular architecture without the need for tissue sectioning. Here we apply a simplified version of the mPS-PI procedure for confocal imaging of cellulose-enriched wall ingrowths in vascular TCs at the whole tissue level. The simplified mPS-PI staining procedure produced high-resolution three-dimensional images of individual cell types in vascular bundles and, importantly, wall ingrowths in phloem parenchyma (PP) TCs in minor veins of Arabidopsis leaves and companion cell TCs in pea. More efficient staining of tissues was obtained by replacing complex clearing procedures with a simple post-fixation bleaching step. We used this modified procedure to survey the presence of PP TCs in other tissues of Arabidopsis including cotyledons, cauline leaves and sepals. This high-resolution imaging enabled us to classify different stages of wall ingrowth development in Arabidopsis leaves, hence enabling semi-quantitative assessment of the extent of wall ingrowth deposition in PP TCs at the whole leaf level. Finally, we conducted a defoliation experiment as an example of using this approach to statistically

Wood cell-wall structure requires local 2D-microtubule disassembly by a novel plasma membrane-anchored protein.

PubMed

Oda, Yoshihisa; Iida, Yuki; Kondo, Yuki; Fukuda, Hiroo

2010-07-13

Plant cells have evolved cortical microtubules, in a two-dimensional space beneath the plasma membrane, that regulate patterning of cellulose deposition. Although recent studies have revealed that several microtubule-associated proteins facilitate self-organization of transverse cortical microtubules, it is still unknown how diverse patterns of cortical microtubules are organized in different xylem cells, which are the major components of wood. Using our newly established in vitro xylem cell differentiation system, we found that a novel microtubule end-tracking protein, microtubule depletion domain 1 (MIDD1), was anchored to distinct plasma membrane domains and promoted local microtubule disassembly, resulting in pits on xylem cell walls. The introduction of RNA interference for MIDD1 resulted in the failure of local microtubule depletion and the formation of secondary walls without pits. Conversely, the overexpression of MIDD1 reduced microtubule density. MIDD1 has two coiled-coil domains for the binding to microtubules and for the anchorage to plasma membrane domains, respectively. Combination of the two coils caused end tracking of microtubules during shrinkage and suppressed their rescue events. Our results indicate that MIDD1 integrates spatial information in the plasma membrane with cortical microtubule dynamics for determining xylem cell wall pattern. Copyright 2010 Elsevier Ltd. All rights reserved.

Anti-transpirant activity in xylem sap from flooded tomato (Lycopersicon esculentum Mill.) plants is not due to pH-mediated redistributions of root- or shoot-sourced ABA.

PubMed

Else, Mark A; Taylor, June M; Atkinson, Christopher J

2006-01-01

In flooded soils, the rapid effects of decreasing oxygen availability on root metabolic activity are likely to generate many potential chemical signals that may impact on stomatal apertures. Detached leaf transpiration tests showed that filtered xylem sap, collected at realistic flow rates from plants flooded for 2 h and 4 h, contained one or more factors that reduced stomatal apertures. The closure could not be attributed to increased root output of the glucose ester of abscisic acid (ABA-GE), since concentrations and deliveries of ABA conjugates were unaffected by soil flooding. Although xylem sap collected from the shoot base of detopped flooded plants became more alkaline within 2 h of flooding, this rapid pH change of 0.5 units did not alter partitioning of root-sourced ABA sufficiently to prompt a transient increase in xylem ABA delivery. More shoot-sourced ABA was detected in the xylem when excised petiole sections were perfused with pH 7 buffer, compared with pH 6 buffer. Sap collected from the fifth oldest leaf of "intact" well-drained plants and plants flooded for 3 h was more alkaline, by approximately 0.4 pH units, than sap collected from the shoot base. Accordingly, xylem [ABA] was increased 2-fold in sap collected from the fifth oldest petiole compared with the shoot base of flooded plants. However, water loss from transpiring, detached leaves was not reduced when the pH of the feeding solution containing 3-h-flooded [ABA] was increased from 6.7 to 7.1 Thus, the extent of the pH-mediated, shoot-sourced ABA redistribution was not sufficient to raise xylem [ABA] to physiologically active levels. Using a detached epidermis bioassay, significant non-ABA anti-transpirant activity was also detected in xylem sap collected at intervals during the first 24 h of soil flooding.

Direct micro-CT observation confirms the induction of embolism upon xylem cutting under tension

USDA-ARS?s Scientific Manuscript database

We used two different Synchrotron-based micro-CT facilities (SLS: Swiss Light Source, Villigen, Switzerland, and ALS: Advanced Light Source, Berkeley, CA USA) to test the excision artifact described by Wheeler et al. (2013). Specifically, we examined the impact of cutting xylem under tension and und...

Quantitative computed tomography of lung parenchyma in patients with emphysema: analysis of higher-density lung regions

NASA Astrophysics Data System (ADS)

Lederman, Dror; Leader, Joseph K.; Zheng, Bin; Sciurba, Frank C.; Tan, Jun; Gur, David

2011-03-01

Quantitative computed tomography (CT) has been widely used to detect and evaluate the presence (or absence) of emphysema applying the density masks at specific thresholds, e.g., -910 or -950 Hounsfield Unit (HU). However, it has also been observed that subjects with similar density-mask based emphysema scores could have varying lung function, possibly indicating differences of disease severity. To assess this possible discrepancy, we investigated whether density distribution of "viable" lung parenchyma regions with pixel values > -910 HU correlates with lung function. A dataset of 38 subjects, who underwent both pulmonary function testing and CT examinations in a COPD SCCOR study, was assembled. After the lung regions depicted on CT images were automatically segmented by a computerized scheme, we systematically divided the lung parenchyma into different density groups (bins) and computed a number of statistical features (i.e., mean, standard deviation (STD), skewness of the pixel value distributions) in these density bins. We then analyzed the correlations between each feature and lung function. The correlation between diffusion lung capacity (DLCO) and STD of pixel values in the bin of -910HU <= PV < -750HU was -0.43, as compared with a correlation of -0.49 obtained between the post-bronchodilator ratio (FEV1/FVC) measured by the forced expiratory volume in 1 second (FEV1) dividing the forced vital capacity (FVC) and the STD of pixel values in the bin of -1024HU <= PV < -910HU. The results showed an association between the distribution of pixel values in "viable" lung parenchyma and lung function, which indicates that similar to the conventional density mask method, the pixel value distribution features in "viable" lung parenchyma areas may also provide clinically useful information to improve assessments of lung disease severity as measured by lung functional tests.

Tomato Ribonuclease LX with the Functional Endoplasmic Reticulum Retention Motif HDEF Is Expressed during Programmed Cell Death Processes, Including Xylem Differentiation, Germination, and Senescence1

PubMed Central

Lehmann, Karin; Hause, Bettina; Altmann, Dorit; Köck, Margret

2001-01-01

We have studied the subcellular localization of the acid S-like ribonuclease (RNase) LX in tomato (Lycopersicon esculentum Mill.) cells using a combination of biochemical and immunological methods. It was found that the enzyme, unexpectedly excluded from highly purified vacuoles, accumulates in the endoplasmic reticulum. The evidence that RNase LX is a resident of the endoplasmic reticulum (ER) is supported by an independent approach showing that the C-terminal peptide HDEF of RNase LX acts as an alternative ER retention signal in plants. For functional testing, the cellular distribution of chimeric protein constructs based on a marker protein, Brazil nut (Bertholletia excelsa) 2S albumin, was analyzed immunochemically in transgenic tobacco (Nicotiana tabacum) plants. Here, we report that the peptide motif is necessary and sufficient to accumulate 2S albumin constructs of both vacuolar and extracellular final destinations in the ER. We have shown immunochemically that RNase LX is specifically expressed during endosperm mobilization and leaf and flower senescence. Using immunofluorescence, RNase LX protein was detected in immature tracheary elements, suggesting a function in xylem differentiation. These results support a physiological function of RNase LX in selective cell death processes that are also thought to involve programmed cell death. It is assumed that RNase LX accumulates in an ER-derived compartment and is released by membrane disruption into the cytoplasma of those cells that are intended to undergo autolysis. These processes are accompanied by degradation of cellular components supporting a metabolic recycling function of the intracellular RNase LX. PMID:11598219

Maximum height in a conifer is associated with conflicting requirements for xylem design

Treesearch

Jean-Chrisophe Domec; Barbara Lachenbruch; Frederick Meinzer; David R. Woodruff; Jeffrey M. Warren; Katherine A. McCulloh

2008-01-01

Despite renewed interest in the nature of limitations on maximum tree height, the mechanisms governing ultimate and species-specific height limits are not yet understood, but they likely involve water transport dynamics. Tall trees experience increased risk of xylem embolism from air-seeding because tension in their water column increases with height owing to path-...

Synchrotron X-ray microtomography of xylem embolism in Sequoia sempervirens saplings during cycles of drought and recovery.

PubMed

Choat, Brendan; Brodersen, Craig R; McElrone, Andrew J

2015-02-01

The formation of emboli in xylem conduits can dramatically reduce hydraulic capacity and represents one of the principal mechanisms of drought-induced mortality in woody plants. However, our understanding of embolism formation and repair is constrained by a lack of tools to directly and nondestructively measure these processes at high spatial resolution. Using synchrotron-based microcomputed tomography (microCT), we examined embolism in the xylem of coast redwood (Sequoia sempervirens) saplings that were subjected to cycles of drought and rewatering. Embolism formation was observed occurring by three different mechanisms: as tracheids embolizing in wide tangential bands; as isolated tracheids in seemingly random events; and as functional groups connected to photosynthetic organs. Upon rewatering, stem water potential recovered to predrought stress levels within 24 h; however, no evidence of embolism repair was observed even after a further 2 wk under well-watered conditions. The results indicate that intertracheid air seeding is the primary mechanism by which embolism spreads in the xylem of S. sempervirens, but also show that a small number of tracheids initially become gas-filled via another mechanism. The inability of S. sempervirens saplings to reverse drought-induced embolism is likely to have important ecological impacts on this species. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

A case of mistaken identity: CD11c-eYFP(+) cells in the normal mouse brain parenchyma and neural retina display the phenotype of microglia, not dendritic cells.

PubMed

Dando, Samantha J; Naranjo Golborne, Cecilia; Chinnery, Holly R; Ruitenberg, Marc J; McMenamin, Paul G

2016-08-01

Under steady-state conditions the central nervous system (CNS) is traditionally thought to be devoid of antigen presenting cells; however, putative dendritic cells (DCs) expressing enhanced yellow fluorescent protein (eYFP) are present in the retina and brain parenchyma of CD11c-eYFP mice. We previously showed that these mice carry the Crb1(rd8) mutation, which causes retinal dystrophic lesions; therefore we hypothesized that the presence of CD11c-eYFP(+) cells within the CNS may be due to pathology associated with the Crb1(rd8) mutation. We generated CD11c-eYFP Crb1(wt/wt) mice and compared the distribution and immunophenotype of CD11c-eYFP(+) cells in CD11c-eYFP mice with and without the Crb1(rd8) mutation. The number and distribution of CD11c-eYFP(+) cells in the CNS was similar between CD11c-eYFP Crb1(wt/wt) and CD11c-eYFP Crb1(rd8/rd8) mice. CD11c-eYFP(+) cells were distributed throughout the inner retina, and clustered in brain regions that receive input from the external environment or lack a blood-brain barrier. CD11c-eYFP(+) cells within the retina and cerebral cortex of CD11c-eYFP Crb1(wt/wt) mice expressed CD11b, F4/80, CD115 and Iba-1, but not DC or antigen presentation markers, whereas CD11c-eYFP(+) cells within the choroid plexus and pia mater expressed CD11c, I-A/I-E, CD80, CD86, CD103, DEC205, CD8α and CD135. The immunophenotype of CD11c-eYFP(+) cells and microglia within the CNS was similar between CD11c-eYFP Crb1(wt/wt) and CD11c-eYFP Crb1(rd8/rd8) mice; however, CD11c and I-A/I-E expression was significantly increased in CD11c-eYFP Crb1(rd8/rd8) mice. This study demonstrates that the overwhelming majority of CNS CD11c-eYFP(+) cells do not display the phenotype of DCs or their precursors and are most likely a subpopulation of microglia. GLIA 2016. GLIA 2016;64:1331-1349. © 2016 Wiley Periodicals, Inc.

Plant fluid proteomics: Delving into the xylem sap, phloem sap and apoplastic fluid proteomes

USDA-ARS?s Scientific Manuscript database

The phloem sap, xylem sap and apoplastic fluid play key roles in long and short distance transport of signals and nutrients, and act as a barrier against local and systemic pathogen infection. Among other components, these plant fluids contain proteins which are likely to be important players in the...

Plant fluid proteomics: Delving into the xylem sap, phloem sap and apoplastic fluid proteomes

USDA-ARS?s Scientific Manuscript database

The phloem sap, xylem sap and apoplastic fluid play key roles in long and short distance transport of signals and nutrients, and act as a barrier against local and systemic pathogen infection. Among other components, these plant fluids contain proteins, which are likely to be important players in th...

Chromium localization in plant tissues of Lycopersicum esculentum Mill using ICP-MS and ion microscopy (SIMS)

NASA Astrophysics Data System (ADS)

Mangabeira, Pedro Antonio; Gavrilov, Konstantin L.; Almeida, Alex-Alan Furtado de; Oliveira, Arno Heeren; Severo, Maria Isabel; Rosa, Tiago Santana; Silva, Delmira da Costa; Labejof, Lise; Escaig, Françoise; Levi-Setti, Riccardo; Mielke, Marcelo Schramm; Loustalot, Florence Grenier; Galle, Pierre

2006-03-01

High-resolution imaging secondary ion mass spectrometry (HRI-SIMS) in combination with inductively coupled plasma mass spectrometry (ICP-MS) were utilised to determine specific sites of chromium concentration in tomato plant tissues (roots, stems and leaves). The tissues were obtained from plants grown for 2 months in hydroponic conditions with Cr added in a form chromium salt (CrCl 3·6H 2O) to concentrations of 25 and 50 mg/L. The chemical fixation procedure used permit to localize only insoluble or strongly bound Cr components in tomato plant tissue. In this work no quantitative SIMS analysis was made. HRI-SIMS analysis revealed that the transport of chromium is restricted to the vascular system of roots, stems and leaves. No Cr was detected in epidermis, palisade parenchyma and spongy parenchyma cells of the leaves. The SIMS-300 spectra obtained from the tissues confirm the HRI-SIMS observations. The roots, and especially walls of xylem vessels, were determined as the principal site of chromium accumulation in tomato plants.

Effects of dormancy progression and low-temperature response on changes in the sorbitol concentration in xylem sap of Japanese pear during winter season.

PubMed

Ito, Akiko; Sugiura, Toshihiko; Sakamoto, Daisuke; Moriguchi, Takaya

2013-04-01

In order to elucidate which physiological event(s) are involved in the seasonal changes of carbohydrate dynamics during winter, we examined the effects of different low temperatures on the carbohydrate concentrations of Japanese pear (Pyrus pyrifolia (Burm.) Nakai). For four winter seasons, large increases in the sorbitol concentration of shoot xylem sap occurred during mid- to late December, possibly due to the endodormancy completion and low-temperature responses. When trees were kept at 15 °C from 3 November to 3 December in order to postpone the initiation and completion of chilling accumulation that would break endodormancy, sorbitol accumulation in xylem sap was always higher from trees with sufficient chilling accumulation than from trees that received insufficient chilling. However, an additional increase in xylem sap sorbitol occurred around late December in trees regardless of whether their chilling accumulation naturally progressed or was postponed. To examine different temperature effects more closely, we compared the carbohydrate concentrations of trees subjected to either 6 or 0 °C treatment. The sorbitol concentration in xylem sap tremendously increased at 0 °C treatment compared with 6 °C treatment. However, an additional increase in xylem sap sorbitol occurred at both the temperatures when sufficient chilling accumulated with a peak coinciding with the peak expression in shoots of the sorbitol transporter gene (PpSOT2). Interestingly, the total carbohydrate concentration of shoots tremendously increased with exposure to 0 °C compared with exposure to 6 °C, but was not affected by the amount of accumulated chilling. Instead, as chilling accumulated the ratio of sorbitol to total soluble sugars in shoots increased. We presumed that carbohydrates in the shoot tissues may be converted to sorbitol and loaded into the xylem sap so that the sorbitol accumulation patterns were synchronized with the progression of dormancy, whereas the total

Magnetic resonance imaging of water ascent in embolized xylem vessels of grapevine stem segments

Treesearch

Mingtao Wang; Melvin T. Tyree; Roderick E. Wasylishen

2013-01-01

Temporal and spatial information about water refilling of embolized xylem vessels and the rate of water ascent in these vessels is critical for understanding embolism repair in intact living vascular plants. High-resolution 1H magnetic resonance imaging (MRI) experiments have been performed on embolized grapevine stem segments while they were...

Investigating xylem embolism formation, refilling and water storage in tree trunks using frequency domain reflectometry.

PubMed

Hao, Guang-You; Wheeler, James K; Holbrook, N Michele; Goldstein, Guillermo

2013-05-01

Trunks of large trees play an important role in whole-plant water balance but technical difficulties have limited most hydraulic research to small stems, leaves, and roots. To investigate the dynamics of water-related processes in tree trunks, such as winter embolism refilling, xylem hydraulic vulnerability, and water storage, volumetric water content (VWC) in the main stem was monitored continuously using frequency domain moisture sensors in adult Betula papyrifera trees from early spring through the beginning of winter. An air injection technique was developed to estimate hydraulic vulnerability of the trunk xylem. Trunk VWC increased in early spring and again in autumn, concurrently with root pressure during both seasons. Diurnal fluctuations and a gradual decrease in trunk VWC through the growing season were observed, which, in combination with VWC increase after significant rainfall events and depletion during periods of high water demand, indicate the importance of stem water storage in both short- and long-term water balance. Comparisons between the trunk air injection results and conventional branch hydraulic vulnerability curves showed no evidence of 'vulnerability segmentation' between the main stem and small branches in B. papyrifera. Measurements of VWC following air injection, together with evidence from air injection and xylem dye perfusion, indicate that embolized vessels can be refilled by active root pressure but not in the absence of root pressure. The precise, continuous, and non-destructive measurement of wood water content using frequency domain sensors provides an ideal way to probe many hydraulic processes in large tree trunks that are otherwise difficult to investigate.

Investigating xylem embolism formation, refilling and water storage in tree trunks using frequency domain reflectometry

PubMed Central

Hao, Guang-You; Wheeler, James K.; Holbrook, N. Michele; Goldstein, Guillermo

2013-01-01

Trunks of large trees play an important role in whole-plant water balance but technical difficulties have limited most hydraulic research to small stems, leaves, and roots. To investigate the dynamics of water-related processes in tree trunks, such as winter embolism refilling, xylem hydraulic vulnerability, and water storage, volumetric water content (VWC) in the main stem was monitored continuously using frequency domain moisture sensors in adult Betula papyrifera trees from early spring through the beginning of winter. An air injection technique was developed to estimate hydraulic vulnerability of the trunk xylem. Trunk VWC increased in early spring and again in autumn, concurrently with root pressure during both seasons. Diurnal fluctuations and a gradual decrease in trunk VWC through the growing season were observed, which, in combination with VWC increase after significant rainfall events and depletion during periods of high water demand, indicate the importance of stem water storage in both short- and long-term water balance. Comparisons between the trunk air injection results and conventional branch hydraulic vulnerability curves showed no evidence of ‘vulnerability segmentation’ between the main stem and small branches in B. papyrifera. Measurements of VWC following air injection, together with evidence from air injection and xylem dye perfusion, indicate that embolized vessels can be refilled by active root pressure but not in the absence of root pressure. The precise, continuous, and non-destructive measurement of wood water content using frequency domain sensors provides an ideal way to probe many hydraulic processes in large tree trunks that are otherwise difficult to investigate. PMID:23585669

Cell water potential, osmotic potential, and turgor in the epidermis and mesophyll of transpiring leaves : Combined measurements with the cell pressure probe and nanoliter osmometer.

PubMed

Nonami, H; Schulze, E D

1989-01-01

Water potential, osmotic potential and turgor measurements obtained by using a cell pressure probe together with a nanoliter osmometer were compared with measurements obtained with an isopiestic psychrometer. Both types of measurements were conducted in the mature region of Tradescantia virginiana L. leaves under non-transpiring conditions in the dark, and gave similar values of all potentials. This finding indicates that the pressure probe and the osmometer provide accurate measurements of turgor, osmotic potentials and water potentials. Because the pressure probe does not require long equilibration times and can measure turgor of single cells in intact plants, the pressure probe together with the osmometer was used to determine in-situ cell water potentials, osmotic potentials and turgor of epidermal and mesophyll cells of transpiring leaves as functions of stomatal aperture and xylem water potential. When the xylem water potential was-0.1 MPa, the stomatal aperture was at its maximum, but turgor of both epidermal and mesophyll cells was relatively low. As the xylem water potential decreased, the stomatal aperture became gradually smaller, whereas turgor of both epidermal and mesophyll cells first increased and afterward decreased. Water potentials of the mesophyll cells were always lower than those of the epidermal cells. These findings indicate that evaporation of water is mainly occurring from mesophyll cells and that peristomatal transpiration could be less important than it has been proposed previously, although peristomatal transpiration may be directly related to regulation of turgor in the guard cells.

Synchrotron microtomography of xylem embolism in Sequoia sempervirens seedlings during cycles of drought and recovery

USDA-ARS?s Scientific Manuscript database

The formation of emboli in xylem conduits can dramatically reduce hydraulic capacity and represents one of the principal mechanisms of drought induced mortality in woody plants. Some angiosperm species possess a mechanism to rapidly repair embolism by dissolving gas back into solution. However, it i...

Hydraulic efficiency and coordination with xylem resistance to cavitation, leaf function, and growth performance among eight unrelated Populus deltoidesxPopulus nigra hybrids.

PubMed

Fichot, Régis; Chamaillard, Sylvain; Depardieu, Claire; Le Thiec, Didier; Cochard, Hervé; Barigah, Têtè S; Brignolas, Franck

2011-03-01

Tests were carried out to determine whether variations in the hydraulic architecture of eight Populus deltoides×Populus nigra genotypes could be related to variations in leaf function and growth performance. Measurements were performed in a coppice plantation on 1-year-old shoots under optimal irrigation. Hydraulic architecture was characterized through estimates of hydraulic efficiency (the ratio of conducting sapwood area to leaf area, A(X):A(L); leaf- and xylem-specific hydraulic conductance of defoliated shoots, k(SL) and k(SS), respectively; apparent whole-plant leaf-specific hydraulic conductance, k(plant)) and xylem safety (water potential inducing 50% loss in hydraulic conductance). The eight genotypes spanned a significant range of k(SL) from 2.63  kg s(-1) m(-2) MPa(-1) to 4.18  kg s(-1) m(-2) MPa(-1), variations being mostly driven by k(SS) rather than A(X):A(L). There was a strong trade-off between hydraulic efficiency and xylem safety. Values of k(SL) correlated positively with k(plant), indicating that high-pressure flowmeter (HPFM) measurements of stem hydraulic efficiency accurately reflected whole-plant water transport efficiency of field-grown plants at maximum transpiration rate. No clear relationship could be found between hydraulic efficiency and either net CO(2) assimilation rates, water-use efficiency estimates (intrinsic water-use efficiency and carbon isotope discrimination against (13)C), or stomatal characteristics (stomatal density and stomatal pore area index). Estimates of hydraulic efficiency were negatively associated with relative growth rate. This unusual pattern, combined with the trade-off observed between hydraulic efficiency and xylem safety, provides the rationale for the positive link already reported between relative growth rate and xylem safety among the same eight P. deltoides×P. nigra genotypes.

The brain parenchyma has a type I interferon response that can limit virus spread.

PubMed

Drokhlyansky, Eugene; Göz Aytürk, Didem; Soh, Timothy K; Chrenek, Ryan; O'Loughlin, Elaine; Madore, Charlotte; Butovsky, Oleg; Cepko, Constance L

2017-01-03

The brain has a tightly regulated environment that protects neurons and limits inflammation, designated "immune privilege." However, there is not an absolute lack of an immune response. We tested the ability of the brain to initiate an innate immune response to a virus, which was directly injected into the brain parenchyma, and to determine whether this response could limit viral spread. We injected vesicular stomatitis virus (VSV), a transsynaptic tracer, or naturally occurring VSV-derived defective interfering particles (DIPs), into the caudate-putamen (CP) and scored for an innate immune response and inhibition of virus spread. We found that the brain parenchyma has a functional type I interferon (IFN) response that can limit VSV spread at both the inoculation site and among synaptically connected neurons. Furthermore, we characterized the response of microglia to VSV infection and found that infected microglia produced type I IFN and uninfected microglia induced an innate immune response following virus injection.

Limitations in the hydraulic pathway: Effects of xylem embolisms on sap velocity and flow

USDA-ARS?s Scientific Manuscript database

Sap flow in plants takes place in the xylem, a hydraulic system that is usually under negative pressure and in which gas and liquid phases are separated by nanoporous, fibrous pit membranes. It has long been known that this system is at risk of drawing gas nanobubbles through these membranes into th...

N. plumbaginifolia zeaxanthin epoxidase transgenic lines have unaltered baseline ABA accumulations in roots and xylem sap, but contrasting sensitivities of ABA accumulation to water deficit.

PubMed

Borel, C; Audran, C; Frey, A; Marion-Poll, A; Tardieu, F; Simonneau, T

2001-03-01

A series of transgenic lines of Nicotiana plumbaginifolia with modified expression of zeaxanthin epoxidase gene (ZEP) provided contrasting ABA accumulation in roots and xylem sap. For mild water stress, concentration of ABA in the xylem sap ([ABA](xylem)) was clearly lower in plants underexpressing ZEP mRNA (complemented mutants and antisense transgenic lines) than in wild-type. In well-watered conditions, all lines presented similar [ABA](xylem) and similar ABA accumulation rates in detached roots. Plants could, therefore, be grown under normal light intensities and evaporative demand. Both ZEP mRNA abundance and ABA accumulation rate in roots increased with water deficit in all transgenic lines, except in complemented aba2-s1 mutants in which the ZEP gene was controlled by a constitutive promoter which does not respond to water deficit. These lines presented no change in root ABA content either with time or dehydration. The increase in ZEP mRNA abundance in roots with decreasing RWC was more pronounced in detached roots than in whole plants, suggesting a difference in mechanism. In all transgenic lines, a linear relationship was observed between predawn leaf water potential and [ABA](xylem), which could be reproduced in several experiments in the greenhouse and in the growth chamber. It is therefore possible to represent the effect of the transformation by a single parameter, thereby allowing the use of a quantitative approach to assist understanding of the behaviour of transgenic lines.

Intervessel connectivity and relationship with patterns of lateral water exchange within and between xylem sectors in seven xeric shrubs from the great Sahara desert.

PubMed

Halis, Youcef; Mayouf, Rabah; Benhaddya, Mohamed Lamine; Belhamra, Mohamed

2013-03-01

The main objective of this study was to evaluate the role of intervessel contacts in determining the patterns of hydraulic integration both within and between xylem sectors. The degree of intervessel contacts and the lateral exchange capability within and between sectors were examined and correlated in different xeric shrubs. A dye injection method was used to detect the connections between vessels; an apoplastic dye was sucked through a known number of vessels and its distribution in the xylem network was followed. Hydraulic techniques were used to measure axial and tangential conductivity both within and between xylem sectors. The intra- and inter-sector integration indexes were then determined as the ratio of tangential to axial conductance. Species differed significantly in the degree of intervessel contacts, intra- and inter-sector integration index. In all cases, hydraulic integration was observed to be higher within sector than between sectors. From the correlation analyses, the intervessel contacts showed a very weak relationship with inter-sector integration index and a strong positive relationship with intra-sector integration index. Results suggested that (1) the factors affecting patterns of lateral flow within xylem sectors might be relatively different from those between sectors. (2) The degree of intervessel contacts was a major determinant of hydraulic integration within the same xylem sector. (3) Intervessel connectivity alone was a poor predictor of hydraulic integration between different sectors, implying a significant contribution of other anatomical, physiological and environmental factors in determining the patterns of integrated-sectored transport within woody stems.

Characterization of xylan in the early stages of secondary cell wall formation in tobacco bright yellow-2 cells.

PubMed

Ishii, Tadashi; Matsuoka, Keita; Ono, Hiroshi; Ohnishi-Kameyama, Mayumi; Yaoi, Katsuro; Nakano, Yoshimi; Ohtani, Misato; Demura, Taku; Iwai, Hiroaki; Satoh, Shinobu

2017-11-15

The major polysaccharides present in the primary and secondary walls surrounding plant cells have been well characterized. However, our knowledge of the early stages of secondary wall formation is limited. To address this, cell walls were isolated from differentiating xylem vessel elements of tobacco bright yellow-2 (BY-2) cells induced by VASCULAR-RELATED NAC-DOMAIN7 (VND7). The walls of induced VND7-VP16-GR BY-2 cells consisted of cellulose, pectic polysaccharides, hemicelluloses, and lignin, and contained more xylan and cellulose compared with non-transformed BY-2 and uninduced VND7-VP16-GR BY-2 cells. A reducing end sequence of xylan containing rhamnose and galaturonic acid- residues is present in the walls of induced, uninduced, and non-transformed BY-2 cells. Glucuronic acid residues in xylan from walls of induced cells are O-methylated, while those of xylan in non-transformed BY-2 and uninduced cells are not. Our results show that xylan changes in chemical structure and amounts during the early stages of xylem differentiation. Copyright © 2017 Elsevier Ltd. All rights reserved.

A comprehensive strategy for identifying long-distance mobile peptides in xylem sap.

PubMed

Okamoto, Satoru; Suzuki, Takamasa; Kawaguchi, Masayoshi; Higashiyama, Tetsuya; Matsubayashi, Yoshikatsu

2015-11-01

There is a growing awareness that secreted pemediate organ-to-organ communication in higher plants. Xylem sap peptidomics is an effective but challenging approach for identifying long-distance mobile peptides. In this study we developed a simple, gel-free purification system that combines o-chlorophenol extraction with HPLC separation. Using this system, we successfully identified seven oligopeptides from soybean xylem sap exudate that had one or more post-transcriptional modifications: glycosylation, sulfation and/or hydroxylation. RNA sequencing and quantitative PCR analyses showed that the peptide-encoding genes are expressed in multiple tissues. We further analyzed the long-distance translocation of four of the seven peptides using gene-encoding peptides with single amino acid substitutions, and identified these four peptides as potential root-to-shoot mobile oligopeptides. Promoter-GUS analysis showed that all four peptide-encoding genes were expressed in the inner tissues of the root endodermis. Moreover, we found that some of these peptide-encoding genes responded to biotic and/or abiotic factors. These results indicate that our purification system provides a comprehensive approach for effectively identifying endogenous small peptides and reinforce the concept that higher plants employ various peptides in root-to-shoot signaling. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

Differences in xylem and leaf hydraulic traits explain differences in drought tolerance among mature Amazon rainforest trees.

PubMed

Powell, Thomas L; Wheeler, James K; de Oliveira, Alex A R; da Costa, Antonio Carlos Lola; Saleska, Scott R; Meir, Patrick; Moorcroft, Paul R

2017-10-01

Considerable uncertainty surrounds the impacts of anthropogenic climate change on the composition and structure of Amazon forests. Building upon results from two large-scale ecosystem drought experiments in the eastern Brazilian Amazon that observed increases in mortality rates among some tree species but not others, in this study we investigate the physiological traits underpinning these differential demographic responses. Xylem pressure at 50% conductivity (xylem-P 50 ), leaf turgor loss point (TLP), cellular osmotic potential (π o ), and cellular bulk modulus of elasticity (ε), all traits mechanistically linked to drought tolerance, were measured on upper canopy branches and leaves of mature trees from selected species growing at the two drought experiment sites. Each species was placed a priori into one of four plant functional type (PFT) categories: drought-tolerant versus drought-intolerant based on observed mortality rates, and subdivided into early- versus late-successional based on wood density. We tested the hypotheses that the measured traits would be significantly different between the four PFTs and that they would be spatially conserved across the two experimental sites. Xylem-P 50 , TLP, and π o , but not ε, occurred at significantly higher water potentials for the drought-intolerant PFT compared to the drought-tolerant PFT; however, there were no significant differences between the early- and late-successional PFTs. These results suggest that these three traits are important for determining drought tolerance, and are largely independent of wood density-a trait commonly associated with successional status. Differences in these physiological traits that occurred between the drought-tolerant and drought-intolerant PFTs were conserved between the two research sites, even though they had different soil types and dry-season lengths. This more detailed understanding of how xylem and leaf hydraulic traits vary between co-occuring drought-tolerant and

Cellulase and cell differentiation in Acer pseudoplatanus.

PubMed

Sheldrake, A R

1970-06-01

Homogenates of differentiating xylem and phloem tissue have higher cellulase activities than cambial samples; the highest activity is always found in phloem. Callus tissue, in which no vascular differentiation occurs, contains only low cellulase activity. The results suggest that cellulase is involved in vascular differentiation. Different pH optima of cellulase activity were found: in cambium, xylem and phloem tissue, cellulase activity with an optimum at about pH 5.9 is predominantly membrane-bound; it is sedimentable at 100,000 g and releasable by Triton X-100. The same may be true of activity with an optimum at pH 5.3. Phloem tissue also contains a soluble, cytoplasmic cellulase of high activity at pH 7.1, and xylem tissue contains cytoplasmic cellulase with an optimum at pH 6.5. Low cellulase activity with a pH optimum similar to that of xylem homogenates was found in xylem sap. Cellulase activity in abscission zones increases greatly just before leaf abscission. Abscission zone cellulase has two pH optima, et 5.3 and 5.9; both activities are increased by Triton treatment of homogenates. The possible existence of several different cellulases forming part of a cellulase complex, and the rôle of the enzymes in hydrolysing wall material during cell differentiation are discussed.

Expression profile of small RNAs in Acacia mangium secondary xylem tissue with contrasting lignin content - potential regulatory sequences in monolignol biosynthetic pathway

PubMed Central

2011-01-01

Background Lignin, after cellulose, is the second most abundant biopolymer accounting for approximately 15-35% of the dry weight of wood. As an important component during wood formation, lignin is indispensable for plant structure and defense. However, it is an undesirable component in the pulp and paper industry. Removal of lignin from cellulose is costly and environmentally hazardous process. Tremendous efforts have been devoted to understand the role of enzymes and genes in controlling the amount and composition of lignin to be deposited in the cell wall. However, studies on the impact of downregulation and overexpression of monolignol biosynthesis genes in model species on lignin content, plant fitness and viability have been inconsistent. Recently, non-coding RNAs have been discovered to play an important role in regulating the entire monolignol biosynthesis pathway. As small RNAs have critical functions in various biological process during wood formation, small RNA profiling is an important tool for the identification of complete set of differentially expressed small RNAs between low lignin and high lignin secondary xylem. Results In line with this, we have generated two small RNAs libraries from samples with contrasting lignin content using Illumina GAII sequencer. About 10 million sequence reads were obtained in secondary xylem of Am48 with high lignin content (41%) and a corresponding 14 million sequence reads were obtained in secondary xylem of Am54 with low lignin content (21%). Our results suggested that A. mangium small RNAs are composed of a set of 12 highly conserved miRNAs families found in plant miRNAs database, 82 novel miRNAs and a large proportion of non-conserved small RNAs with low expression levels. The predicted target genes of those differentially expressed conserved and non-conserved miRNAs include transcription factors associated with regulation of the lignin biosynthetic pathway genes. Some of these small RNAs play an important role in

Expression profile of small RNAs in Acacia mangium secondary xylem tissue with contrasting lignin content - potential regulatory sequences in monolignol biosynthetic pathway.

PubMed

Ong, Seong Siang; Wickneswari, Ratnam

2011-11-30

Lignin, after cellulose, is the second most abundant biopolymer accounting for approximately 15-35% of the dry weight of wood. As an important component during wood formation, lignin is indispensable for plant structure and defense. However, it is an undesirable component in the pulp and paper industry. Removal of lignin from cellulose is costly and environmentally hazardous process. Tremendous efforts have been devoted to understand the role of enzymes and genes in controlling the amount and composition of lignin to be deposited in the cell wall. However, studies on the impact of downregulation and overexpression of monolignol biosynthesis genes in model species on lignin content, plant fitness and viability have been inconsistent. Recently, non-coding RNAs have been discovered to play an important role in regulating the entire monolignol biosynthesis pathway. As small RNAs have critical functions in various biological process during wood formation, small RNA profiling is an important tool for the identification of complete set of differentially expressed small RNAs between low lignin and high lignin secondary xylem. In line with this, we have generated two small RNAs libraries from samples with contrasting lignin content using Illumina GAII sequencer. About 10 million sequence reads were obtained in secondary xylem of Am48 with high lignin content (41%) and a corresponding 14 million sequence reads were obtained in secondary xylem of Am54 with low lignin content (21%). Our results suggested that A. mangium small RNAs are composed of a set of 12 highly conserved miRNAs families found in plant miRNAs database, 82 novel miRNAs and a large proportion of non-conserved small RNAs with low expression levels. The predicted target genes of those differentially expressed conserved and non-conserved miRNAs include transcription factors associated with regulation of the lignin biosynthetic pathway genes. Some of these small RNAs play an important role in epigenetic silencing

Identification of Maize Silicon Influx Transporters

PubMed Central

Mitani, Namiki; Yamaji, Naoki; Ma, Jian Feng

2009-01-01

Maize (Zea mays L.) shows a high accumulation of silicon (Si), but transporters involved in the uptake and distribution have not been identified. In the present study, we isolated two genes (ZmLsi1 and ZmLsi6), which are homologous to rice influx Si transporter OsLsi1. Heterologous expression in Xenopus laevis oocytes showed that both ZmLsi1 and ZmLsi6 are permeable to silicic acid. ZmLsi1 was mainly expressed in the roots. By contrast, ZmLsi6 was expressed more in the leaf sheaths and blades. Different from OsLsi1, the expression level of both ZmLsi1 and ZmLsi6 was unaffected by Si supply. Immunostaining showed that ZmLsi1 was localized on the plasma membrane of the distal side of root epidermal and hypodermal cells in the seminal and crown roots, and also in cortex cells in lateral roots. In the shoots, ZmLsi6 was found in the xylem parenchyma cells that are adjacent to the vessels in both leaf sheaths and leaf blades. ZmLsi6 in the leaf sheaths and blades also exhibited polar localization on the side facing towards the vessel. Taken together, it can be concluded that ZmLsi1 is an influx transporter of Si, which is responsible for the transport of Si from the external solution to the root cells and that ZmLsi6 mainly functions as a Si transporter for xylem unloading. PMID:18676379

Water Flow through Xylem: An Investigation of a Fluid Dynamics Principle Applied to Plants

ERIC Educational Resources Information Center

Rice, Stanley A.; McArthur, John

2004-01-01

A study was conducted to prove that a large blood or xylem vessel could conduct 256 times more fluid than a vessel or a pipe that is four times smaller. The result of this study proved that if arteriosclerosis causes an artery to loose half its effective diameter, the blood flow would be reduced by fifteen-sixteenths.

Pulmonary parenchyma segmentation in thin CT image sequences with spectral clustering and geodesic active contour model based on similarity

NASA Astrophysics Data System (ADS)

He, Nana; Zhang, Xiaolong; Zhao, Juanjuan; Zhao, Huilan; Qiang, Yan

2017-07-01

While the popular thin layer scanning technology of spiral CT has helped to improve diagnoses of lung diseases, the large volumes of scanning images produced by the technology also dramatically increase the load of physicians in lesion detection. Computer-aided diagnosis techniques like lesions segmentation in thin CT sequences have been developed to address this issue, but it remains a challenge to achieve high segmentation efficiency and accuracy without much involvement of human manual intervention. In this paper, we present our research on automated segmentation of lung parenchyma with an improved geodesic active contour model that is geodesic active contour model based on similarity (GACBS). Combining spectral clustering algorithm based on Nystrom (SCN) with GACBS, this algorithm first extracts key image slices, then uses these slices to generate an initial contour of pulmonary parenchyma of un-segmented slices with an interpolation algorithm, and finally segments lung parenchyma of un-segmented slices. Experimental results show that the segmentation results generated by our method are close to what manual segmentation can produce, with an average volume overlap ratio of 91.48%.

Coexisting oak species, including rear-edge populations, buffer climate stress through xylem adjustments.

PubMed

Granda, E; Alla, A Q; Laskurain, N A; Loidi, J; Sánchez-Lorenzo, A; Camarero, J J

2018-02-01

The ability of trees to cope with climate change is a pivotal feature of forest ecosystems, especially for rear-edge populations facing warm and dry conditions. To evaluate current and future forests threats, a multi-proxy focus on the growth, anatomical and physiological responses to climate change is needed. We examined the long-term xylem adjustments to climate variability of the temperate Quercus robur L. at its rear edge and the sub-Mediterranean Quercus pyrenaica Willd. Both species coexist at a mesic (ME, humid and warmer) and a xeric (XE, dry and cooler) site in northern Spain, the latter experiencing increasing temperatures in recent decades. We compared xylem traits at each site and assessed their trends, relationships and responses to climate (1960-2008). Traits included basal area increment, earlywood vessel hydraulic diameter, density and theoretical-specific hydraulic conductivity together with latewood oxygen (δ18O) stable isotopes and δ13C-derived water-use efficiency (iWUE). Quercus robur showed the highest growth at ME, likely through enhanced cambial activity. Quercus pyrenaica had higher iWUE at XE compared with ME, but limited plasticity of anatomical xylem traits was found for the two oak species. Similar physiological performance was found for both species. The iWUE augmented in recent years especially at XE, likely explained by stomatal closure given the increasing δ18O signal in response to drier and sunnier growing seasons. Overall, traits were more correlated at XE than at ME. The iWUE improvements were linked to higher growth up to a threshold (~85 μmol mol-1) after which reduced growth was found at XE. Our results are consistent with Q. pyrenaica and Q. robur coexisting at the central and dry edge of the climatic species distribution, respectively, showing similar responses to buffer warmer conditions. In fact, the observed adjustments found for Q. robur point towards growth stability of similar rear-edge oak populations under

Assessment of xylem phenology: a first attempt to verify its accuracy and precision.

PubMed

Lupi, C; Rossi, S; Vieira, J; Morin, H; Deslauriers, A

2014-01-01

This manuscript aims to evaluate the precision and accuracy of current methodology for estimating xylem phenology and tracheid production in trees. Through a simple approach, sampling at two positions on the stem of co-dominant black spruce trees in two sites of the boreal forest of Quebec, we were able to quantify variability among sites, between trees and within a tree for different variables. We demonstrated that current methodology is accurate for the estimation of the onset of xylogenesis, while the accuracy for the evaluation of the ending of xylogenesis may be improved by sampling at multiple positions on the stem. The pattern of variability in different phenological variables and cell production allowed us to advance a novel hypothesis on the shift in the importance of various drivers of xylogenesis, from factors mainly varying at the level of site (e.g., climate) at the beginning of the growing season to factors varying at the level of individual trees (e.g., possibly genetic variability) at the end of the growing season.

Proteomics of plasma membranes from poplar trees reveals tissue distribution of transporters, receptors, and proteins in cell wall formation.

PubMed

Nilsson, Robert; Bernfur, Katja; Gustavsson, Niklas; Bygdell, Joakim; Wingsle, Gunnar; Larsson, Christer

2010-02-01

By exploiting the abundant tissues available from Populus trees, 3-4 m high, we have been able to isolate plasma membranes of high purity from leaves, xylem, and cambium/phloem at a time (4 weeks after bud break) when photosynthesis in the leaves and wood formation in the xylem should have reached a steady state. More than 40% of the 956 proteins identified were found in the plasma membranes of all three tissues and may be classified as "housekeeping" proteins, a typical example being P-type H(+)-ATPases. Among the 213 proteins predicted to be integral membrane proteins, transporters constitute the largest class (41%) followed by receptors (14%) and proteins involved in cell wall and carbohydrate metabolism (8%) and membrane trafficking (8%). ATP-binding cassette transporters (all members of subfamilies B, C, and G) and receptor-like kinases (four subfamilies) were two of the largest protein families found, and the members of these two families showed pronounced tissue distribution. Leaf plasma membranes were characterized by a very high proportion of transporters, constituting almost half of the integral proteins. Proteins involved in cell wall synthesis (such as cellulose and sucrose synthases) and membrane trafficking were most abundant in xylem plasma membranes in agreement with the role of the xylem in wood formation. Twenty-five integral proteins and 83 soluble proteins were exclusively found in xylem plasma membranes, which identifies new candidates associated with cell wall synthesis and wood formation. Among the proteins uniquely found in xylem plasma membranes were most of the enzymes involved in lignin biosynthesis, which suggests that they may exist as a complex linked to the plasma membrane.

Comparison of stem morphology and anatomy of two alfalfa clonal lines exhibiting divergent cell wall composition.

PubMed

Gronwald, John W; Bucciarelli, Bruna

2013-08-30

In previous research, two alfalfa clonal lines (252 and 1283) were identified that exhibited environmentally stable differences in stem cell walls. Compared with stems of 1283, stems of 252 have a higher cell wall concentration and greater amounts of lignin and cellulose but reduced levels of pectic sugar residues. These results suggest greater deposition of secondary xylem and a reduction in pith in stems of 252 compared with 1283. The stem morphology and anatomy of first-cut and second-cut harvests of field-grown 1283 and 252 were examined. For both harvests, stems of 1283 were thicker and had a higher leaf/stem ratio compared with stems of 252. Stem cross-sections of both genotypes were stained for lignin, and the proportions of stem area that were pith and secondary xylem were measured using ImageJ. Stems of 252 exhibited greater deposition of secondary xylem and a reduction in pith proportion compared with stems of 1283 for the first-cut harvest, but this difference was not statistically significant for the second-cut harvest. The results indicate that the proportions of secondary xylem and pith are not environmentally stable in these two genotypes and hence cannot be the sole basis for the differences in cell wall concentration/composition. © 2012 Society of Chemical Industry.

Frost drought in conifers at the alpine timberline: xylem dysfunction and adaptations.

PubMed

Mayr, Stefan; Hacke, Uwe; Schmid, Peter; Schwienbacher, Franziska; Gruber, Andreas

2006-12-01

Drought stress can cause xylem embolism in trees when the water potential (psi) in the xylem falls below specific vulnerability thresholds. At the alpine timberline, frost drought is known to cause excessive winter embolism unless xylem vulnerability or transpiration is sufficiently reduced to avoid critical psi. We compared annual courses of psi and embolism in Picea abies, Pinus cembra, Pinus mugo, Larix decidua, and Juniperus communis growing at the timberline vs. low altitude. In addition, vulnerability properties and related anatomical parameters as well as wood density (D(t)) and wall reinforcement (wall thickness related to conduit diameter) were studied. This allowed an estimate of stress intensities as well as a detection of adaptations that reduce embolism formation. At the alpine timberline, psi was lowest during winter with corresponding embolism rates of up to 100% in three of the conifers studied. Only Pinus cembra and Larix decidua avoided winter embolism due to moderate psi. Minor embolism was observed at low altitude where the water potentials of all species remained within a narrow range throughout the year. Within species, differences in psi50 (psi at 50% loss of conductivity) at high vs. low altitude were less than 1 MPa. In Picea abies and Pinus cembra, psi50 was more negative at the timberline while, in the other conifer species, psi50 was more negative at low altitude. Juniperus communis exhibited the lowest (-6.4 +/- 0.04 MPa; mean +/- SE) and Pinus mugo the highest psi50 (-3.34 +/- 0.03 MPa). In some cases, D(t) and tracheid wall reinforcement were higher than in previously established relationships of these parameters with psi50, possibly because of mechanical demands associated with the specific growing conditions. Conifers growing at the alpine timberline were exposed to higher drought stress intensities than individuals at low altitude. Frost drought during winter caused high embolism rates which were probably amplified by freeze

A noninvasive optical system for the measurement of xylem and phloem sap flow in woody plants of small stem size.

PubMed

Helfter, Carole; Shephard, Jonathon D; Martinez-Vilalta, Jordi; Mencuccini, Maurizio; Hand, Duncan P

2007-02-01

Over the past 70 years, heat has been widely used as a tracer for estimating the flow of water in woody and herbaceous plants. However, most commercially available techniques for monitoring whole plant water use are invasive and the measurements are potentially flawed because of wounding of the xylem tissue. The study of photosynthate transport in the phloem remains in its infancy, and little information about phloem transport rates is available owing to the fragility of the vascular tissue. The aim of our study was to develop a compact, stand-alone non-invasive system allowing for direct detection of phloem and xylem sap movement. The proposed method uses a heat pulse as a tracer for sap flow. Heat is applied to the surface of the stem with a near-infrared laser source, and heat propagation is monitored externally by means of an infrared camera. Heat pulse velocities are determined from the thermometric data and related to the more useful quantity, mass flow rate. Simulation experiments on the xylem tissue of severed silver birch (Betula pendula Roth.) branch segments were performed to assess the feasibility of the proposed approach, highlight the characteristics of the technique and outline calibration strategies. Good agreement between imposed and measured flow rates was achieved leading to experimentation with live silver birch and oak (Quercus robur L.) saplings. It was demonstrated that water flow through xylem vessels can be monitored non-invasively on an intact stem with satisfactory accuracy despite simultaneous sugar transport in the phloem. In addition, it was demonstrated that the technique allows for unequivocal detection of phloem flow velocities.

BRANCH JUNCTIONS AND THE FLOW OF WATER THROUGH XYLEM IN DOUGLAS-FIR AND PONDEROSA PINE STEMS

EPA Science Inventory

Water flowing through the xylem of most plants from the roots to the leaves must pass through junctions where branches have developed from the main stem. These junctions have been studied as both flow constrictions and components of a hydraulic segmentation mechanism to protect ...

The dynamic pipeline: hydraulic capacitance and xylem hydraulic safety in four tall conifer species

Treesearch

Katherine A. McCulloh; Daniel M. Johnson; Frederick C. Meinzer; David R. Woodruff

2013-01-01

Recent work has suggested that plants differ in their relative reliance on structural avoidance of embolism versus maintenance of the xylem water column through dynamic traits such as capacitance, but we still know little about how and why species differ along this continuum. It is even less clear how or if different parts of a plant vary along this spectrum. Here we...

Different cation stresses affect specifically osmotic root hydraulic conductance, involving aquaporins, ATPase and xylem loading of ions in Capsicum annuum, L. plants.

PubMed

Cabañero, Francisco J; Carvajal, Micaela

2007-10-01

In order to study the effect of nutrient stress on water uptake in pepper plants (Capsicum annuum L.), the excess or deficiency of the main cations involved in plant nutrition (K(+), Mg(2+), Ca(2+)) and two different degrees of salinity were related to the activity of plasma membrane H(+)-ATPase, the pH of the xylem sap, nutrient flux into the xylem (J(s)) and to a number of parameters related to water relations, such as root hydraulic conductance (L(0)), stomatal conductance (g(s)) and aquaporin activity. Excess of K(+), Ca(+) and NaCl produced a toxic effect on L(0) while Mg(2+) starvation produced a positive effect, which was in agreement with aquaporin functionality, but not with ATPase activity. The xylem pH was altered only by Ca treatments. The results obtained with each treatment could suggest that detection of the quality of the nutrient supply being received by roots can be related to aquaporins functionality, but also that each cation stress triggers specific responses that have to be assessed individually.

Xylem- and phloem-based transport of CuO nanoparticles in maize (Zea mays L.).

PubMed

Wang, Zhenyu; Xie, Xiaoyan; Zhao, Jian; Liu, Xiaoyun; Feng, Wenqiang; White, Jason C; Xing, Baoshan

2012-04-17

This work reports on the toxicity of CuO nanoparticles (NPs) to maize (Zea mays L.) and their transport and redistribution in the plant. CuO NPs (100 mg L(-1)) had no effect on germination, but inhibited the growth of maize seedlings; in comparison the dissolved Cu(2+) ions and CuO bulk particles had no obvious effect on maize growth. CuO NPs were present in xylem sap as examined by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS), showing that CuO NPs were transported from roots to shoots via xylem. Split-root experiments and high-resolution TEM observation further showed that CuO NPs could translocate from shoots back to roots via phloem. During this translocation, CuO NPs could be reduced from Cu (II) to Cu (I). To our knowledge, this is the first report of root-shoot-root redistribution of CuO NPs within maize. The current study provides direct evidence for the bioaccumulation and biotransformation of CuO NPs (20-40 nm) in maize, which has significant implications on the potential risk of NPs and food safety.

Fully automatized renal parenchyma volumetry using a support vector machine based recognition system for subject-specific probability map generation in native MR volume data.

PubMed

Gloger, Oliver; Tönnies, Klaus; Mensel, Birger; Völzke, Henry

2015-11-21

In epidemiological studies as well as in clinical practice the amount of produced medical image data strongly increased in the last decade. In this context organ segmentation in MR volume data gained increasing attention for medical applications. Especially in large-scale population-based studies organ volumetry is highly relevant requiring exact organ segmentation. Since manual segmentation is time-consuming and prone to reader variability, large-scale studies need automatized methods to perform organ segmentation. Fully automatic organ segmentation in native MR image data has proven to be a very challenging task. Imaging artifacts as well as inter- and intrasubject MR-intensity differences complicate the application of supervised learning strategies. Thus, we propose a modularized framework of a two-stepped probabilistic approach that generates subject-specific probability maps for renal parenchyma tissue, which are refined subsequently by using several, extended segmentation strategies. We present a three class-based support vector machine recognition system that incorporates Fourier descriptors as shape features to recognize and segment characteristic parenchyma parts. Probabilistic methods use the segmented characteristic parenchyma parts to generate high quality subject-specific parenchyma probability maps. Several refinement strategies including a final shape-based 3D level set segmentation technique are used in subsequent processing modules to segment renal parenchyma. Furthermore, our framework recognizes and excludes renal cysts from parenchymal volume, which is important to analyze renal functions. Volume errors and Dice coefficients show that our presented framework outperforms existing approaches.

Fully automatized renal parenchyma volumetry using a support vector machine based recognition system for subject-specific probability map generation in native MR volume data

NASA Astrophysics Data System (ADS)

Gloger, Oliver; Tönnies, Klaus; Mensel, Birger; Völzke, Henry

2015-11-01

In epidemiological studies as well as in clinical practice the amount of produced medical image data strongly increased in the last decade. In this context organ segmentation in MR volume data gained increasing attention for medical applications. Especially in large-scale population-based studies organ volumetry is highly relevant requiring exact organ segmentation. Since manual segmentation is time-consuming and prone to reader variability, large-scale studies need automatized methods to perform organ segmentation. Fully automatic organ segmentation in native MR image data has proven to be a very challenging task. Imaging artifacts as well as inter- and intrasubject MR-intensity differences complicate the application of supervised learning strategies. Thus, we propose a modularized framework of a two-stepped probabilistic approach that generates subject-specific probability maps for renal parenchyma tissue, which are refined subsequently by using several, extended segmentation strategies. We present a three class-based support vector machine recognition system that incorporates Fourier descriptors as shape features to recognize and segment characteristic parenchyma parts. Probabilistic methods use the segmented characteristic parenchyma parts to generate high quality subject-specific parenchyma probability maps. Several refinement strategies including a final shape-based 3D level set segmentation technique are used in subsequent processing modules to segment renal parenchyma. Furthermore, our framework recognizes and excludes renal cysts from parenchymal volume, which is important to analyze renal functions. Volume errors and Dice coefficients show that our presented framework outperforms existing approaches.

Linking Xylem Hydraulic Conductivity and Vulnerability to the Leaf Economics Spectrum—A Cross-Species Study of 39 Evergreen and Deciduous Broadleaved Subtropical Tree Species

PubMed Central

Kröber, Wenzel; Zhang, Shouren; Ehmig, Merten; Bruelheide, Helge

2014-01-01

While the fundamental trade-off in leaf traits related to carbon capture as described by the leaf economics spectrum is well-established among plant species, the relationship of the leaf economics spectrum to stem hydraulics is much less known. Since carbon capture and transpiration are coupled, a close connection between leaf traits and stem hydraulics should be expected. We thus asked whether xylem traits that describe drought tolerance and vulnerability to cavitation are linked to particular leaf traits. We assessed xylem vulnerability, using the pressure sleeve technique, and anatomical xylem characteristics in 39 subtropical tree species grown under common garden conditions in the BEF-China experiment and tested for correlations with traits related to the leaf economics spectrum as well as to stomatal control, including maximum stomatal conductance, vapor pressure deficit at maximum stomatal conductance and vapor pressure deficit at which stomatal conductance is down-regulated. Our results revealed that specific xylem hydraulic conductivity and cavitation resistance were closely linked to traits represented in the leaf economic spectrum, in particular to leaf nitrogen concentration, as well as to log leaf area and leaf carbon to nitrogen ratio but not to any parameter of stomatal conductance. The study highlights the potential use of well-known leaf traits from the leaf economics spectrum to predict plant species' drought resistance. PMID:25423316

Linking xylem hydraulic conductivity and vulnerability to the leaf economics spectrum--a cross-species study of 39 evergreen and deciduous broadleaved subtropical tree species.

PubMed

Kröber, Wenzel; Zhang, Shouren; Ehmig, Merten; Bruelheide, Helge

2014-01-01

While the fundamental trade-off in leaf traits related to carbon capture as described by the leaf economics spectrum is well-established among plant species, the relationship of the leaf economics spectrum to stem hydraulics is much less known. Since carbon capture and transpiration are coupled, a close connection between leaf traits and stem hydraulics should be expected. We thus asked whether xylem traits that describe drought tolerance and vulnerability to cavitation are linked to particular leaf traits. We assessed xylem vulnerability, using the pressure sleeve technique, and anatomical xylem characteristics in 39 subtropical tree species grown under common garden conditions in the BEF-China experiment and tested for correlations with traits related to the leaf economics spectrum as well as to stomatal control, including maximum stomatal conductance, vapor pressure deficit at maximum stomatal conductance and vapor pressure deficit at which stomatal conductance is down-regulated. Our results revealed that specific xylem hydraulic conductivity and cavitation resistance were closely linked to traits represented in the leaf economic spectrum, in particular to leaf nitrogen concentration, as well as to log leaf area and leaf carbon to nitrogen ratio but not to any parameter of stomatal conductance. The study highlights the potential use of well-known leaf traits from the leaf economics spectrum to predict plant species' drought resistance.

18O Spatial Patterns of Vein Xylem Water, Leaf Water, and Dry Matter in Cotton Leaves

PubMed Central

Gan, Kim Suan; Wong, Suan Chin; Yong, Jean Wan Hong; Farquhar, Graham Douglas

2002-01-01

Three leaf water models (two-pool model, Péclet effect, and string-of-lakes) were assessed for their robustness in predicting leaf water enrichment and its spatial heterogeneity. This was achieved by studying the 18O spatial patterns of vein xylem water, leaf water, and dry matter in cotton (Gossypium hirsutum) leaves grown at different humidities using new experimental approaches. Vein xylem water was collected from intact transpiring cotton leaves by pressurizing the roots in a pressure chamber, whereas the isotopic content of leaf water was determined without extracting it from fresh leaves with the aid of a purpose-designed leaf punch. Our results indicate that veins have a significant degree of lateral exchange with highly enriched leaf water. Vein xylem water is thus slightly, but progressively enriched in the direction of water flow. Leaf water enrichment is dependent on the relative distances from major veins, with water from the marginal and intercostal regions more enriched and that next to veins and near the leaf base more depleted than the Craig-Gordon modeled enrichment of water at the sites of evaporation. The spatial pattern of leaf water enrichment varies with humidity, as expected from the string-of-lakes model. This pattern is also reflected in leaf dry matter. All three models are realistic, but none could fully account for all of the facets of leaf water enrichment. Our findings acknowledge the presence of capacitance in the ground tissues of vein ribs and highlight the essential need to incorporate Péclet effects into the string-of-lakes model when applying it to leaves. PMID:12376664

Tree-ring anatomy and carbon isotope ratio show both direct and legacy effects of climate on bimodal xylem formation in Pinus pinea.

PubMed

Castagneri, Daniele; Battipaglia, Giovanna; von Arx, Georg; Pacheco, Arturo; Carrer, Marco

2018-04-24

Understanding how climate affects xylem formation is critical for predicting the impact of future conditions on tree growth and functioning in the Mediterranean region, which is expected to face warmer and drier conditions. However, mechanisms of growth response to climate at different temporal scales are still largely unknown, being complicated by separation between spring and autumn xylogenesis (bimodal temporal pattern) in most species such as Mediterranean pines. We investigated wood anatomical characteristics and carbon stable isotope composition in Mediterranean Pinus pinea L. along tree-ring series at intra-ring resolution to assess xylem formation processes and responses to intra-annual climate variability. Xylem anatomy was strongly related to environmental conditions occurring a few months before and during the growing season, but was not affected by summer drought. In particular, the lumen diameter of the first earlywood tracheids was related to winter precipitation, whereas the size of tracheids produced later was influenced by mid-spring precipitation. Diameter of latewood tracheids was associated with precipitation in mid-autumn. In contrast, tree-ring carbon isotope composition was mostly related to climate of the previous seasons. Earlywood was likely formed using both recently and formerly assimilated carbon, while latewood relied mostly on carbon accumulated many months prior to its formation. Our integrated approach provided new evidence on the short-term and carry-over effects of climate on the bimodal temporal xylem formation in P. pinea. Investigations on different variables and time scales are necessary to disentangle the complex climate influence on tree growth processes under Mediterranean conditions.

Comparing renal function preservation after laparoscopic radio frequency ablation assisted tumor enucleation and laparoscopic partial nephrectomy for clinical T1a renal tumor: using a 3D parenchyma measurement system.

PubMed

Zhu, Liangsong; Wu, Guangyu; Huang, Jiwei; Wang, Jianfeng; Zhang, Ruiyun; Kong, Wen; Xue, Wei; Huang, Yiran; Chen, Yonghui; Zhang, Jin

2017-05-01

To compare the renal function preservation between laparoscopic radio frequency ablation assisted tumor enucleation and laparoscopic partial nephrectomy. Data were analyzed from 246 patients who underwent laparoscopic radio frequency ablation assisted tumor enucleation and laparoscopic partial nephrectomy for solitary cT1a renal cell carcinoma from January 2013 to July 2015. To reduce the intergroup difference, we used a 1:1 propensity matching analysis. The functional renal parenchyma volume preservation were measured preoperative and 12 months after surgery. The total renal function recovery and spilt GFR was compared. Multivariable logistic analysis was used for predictive factors for renal function decline. After 1:1 propensity matching, each group including 100 patients. Patients in the laparoscopic radio frequency ablation assisted tumor enucleation had a smaller decrease in estimate glomerular filtration rate at 1 day (-7.88 vs -20.01%, p < 0.001), 3 months (-2.31 vs -10.39%, p < 0.001), 6 months (-2.16 vs -7.99%, p = 0.015), 12 months (-3.26 vs -8.03%, p = 0.012) and latest test (-3.24 vs -8.02%, p = 0.040), also had better functional renal parenchyma volume preservation (89.19 vs 84.27%, p < 0.001), lower decrease of the spilt glomerular filtration rate (-9.41 vs -17.13%, p < 0.001) at 12 months. The functional renal parenchyma volume preservation, warm ischemia time and baseline renal function were the important independent factors in determining long-term functional recovery. The laparoscopic radio frequency ablation assisted tumor enucleation technology has unique advantage and potential in preserving renal parenchyma without ischemia damage compared to conventional laparoscopic partial nephrectomy, and had a better outcome, thus we recommend this technique in selected T1a patients.

Xylem specific activation of 5' upstream regulatory region of two NAC transcription factors (MusaVND6 and MusaVND7) in banana is regulated by SNBE-like sites.

PubMed

Negi, Sanjana; Tak, Himanshu; Ganapathi, T R

2018-01-01

Deposition of secondary cell wall in the xylem elements is controlled by a subgroup of NAC (NAM, ATAF, CUC) family, known as vascular-related NAC transcription factors (VNDs). In the present study, we analyzed the 5' upstream regulatory region of two banana NAC transcription factors (MusaVND6 and MusaVND7) for tissue specific expression and presence of 19-bp secondary-wall NAC binding element (SNBE)-like motifs. Transgenic banana plants of Musa cultivar Rasthali harboring either PMusaVND7::GUS or PMusaVND6::GUS showed specific GUS (β-D-Glucuronidase) activity in cells of the xylem tissue. Approximately 1.2kb promoter region of either MusaVND6 or MusaVND7 showed presence of at least two SNBE-like motifs. This 1.2kb promoter region was retarded in a gel shift assay by three banana VND protein (VND1,VND2 and VND3). The banana VND1-VND3 could also retard the mobility of isolated SNBE-like motifs of MusaVND6 or MusaVND7 in a gel shift assay. Transcript levels of MusaVND6 and MusaVND7 were elevated in transgenic banana overexpressing either banana VND1, VND2 or VND3. Present study suggested a probable regulation of banana VND6 and VND7 expression through direct interaction of banana VND1- VND3 with SNBE-like motifs. Our study also indicated two promoter elements for possible utilization in cell wall modifications in plants especially banana, which is being recently considered as a potential biofuel crop.

Spatial distribution of xylem embolisms in the stems of Pinus thunbergii at the threshold of fatal drought stress.

PubMed

Umebayashi, Toshihiro; Morita, Toshimitsu; Utsumi, Yasuhiro; Kusumoto, Dai; Yasuda, Yuko; Haishi, Tomoyuki; Fukuda, Kenji

2016-10-01

Although previous studies have suggested that branch dieback and whole-plant death due to drought stress occur at 50-88% loss of stem hydraulic conductivity (P 50 and P 88 , respectively), the dynamics of catastrophic failure in the water-conducting pathways in whole plants subjected to drought remain poorly understood. We examined the dynamics of drought stress tolerance in 3-year-old Japanese black pine (Pinus thunbergii Parl.). We nondestructively monitored (i) the spatial distribution of drought-induced embolisms in the stem at greater than P 50 and (ii) recovery from embolisms following rehydration. Stem water distributions were visualized by cryo-scanning electron microscopy. The percentages of both embolized area and loss of hydraulic conductivity showed similar patterns of increase, although the water loss in xylem increased markedly at -5.0 MPa or less. One seedling that had reached 72% loss of the water-conducting area survived and the xylem water potential recovered to -0.3 MPa. We concluded that Japanese black pines may need to maintain water-filled tracheids within earlywood of the current-year xylem under natural conditions to avoid disconnection of water movement between the stem and the tops of branches. It is necessary to determine the spatial distribution of embolisms around the point of the lethal threshold to gain an improved understanding of plant survival under conditions of drought. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Genetic diversity of root anatomy in wild and cultivated Manihot species.

PubMed

Bomfim, N N; Graciano-Ribeiro, D; Nassar, N M A

2011-04-05

An anatomical study of roots was conducted on two wild Manihot species, namely M. glaziovii and M. fortalezensis, and two cassava varieties, M. esculenta Crantz variety UnB 201 and M. esculenta variety UnB 122, to identify taxonomic differences in primary growth. Anatomical characters of cassava roots have been rarely investigated. Their study may help cassava breeders to identify varieties with economically important characters, such as tolerance to drought. We investigated tap and lateral adventitious roots of two specimens of each clone or species. Free-hand cross-sections of roots were drawn; these had been clarified with 20% sodium hypochlorite solution, stained with 1% safranin-alcian blue ethanolic solution, dehydrated in ethanol series and butyl acetate and mounted in synthetic resin. Anatomical differences among Manihot species and varieties were found in the epidermal and exodermal cell shape and wall thickness, content of cortical parenchyma, and number of xylem poles. Wall thickness of the epidermis and exodermis of tap root were similar in all species, while in the lateral root there were differences in cell shape and wall thickness. Epidermal cells with thick walls were found in the tap root of all species and in lateral roots of cassava varieties. This character is apparently associated with tolerance to drought and disease. The variation in the number of xylem poles of cassava varieties was larger (4-8) than in wild species (4-6), and appears to support the hybrid origin of cassava.

In Situ Visualization of the Dynamics in Xylem Embolism Formation and Removal in the Absence of Root Pressure: A Study on Excised Grapevine Stems1[OPEN

PubMed Central

Knipfer, Thorsten; Cuneo, Italo F.; Brodersen, Craig R.; McElrone, Andrew J.

2016-01-01

Gas embolisms formed during drought can disrupt long-distance water transport through plant xylem vessels, but some species have the ability to remove these blockages. Despite evidence suggesting that embolism removal is linked to the presence of vessel-associated parenchyma, the underlying mechanism remains controversial and is thought to involve positive pressure generated by roots. Here, we used in situ x-ray microtomography on excised grapevine stems to determine if embolism removal is possible without root pressure, and if the embolism formation/removal affects vessel functional status after sample excision. Our data show that embolism removal in excised stems was driven by water droplet growth and was qualitatively identical to refilling in intact plants. When stem segments were rehydrated with H2O after excision, vessel refilling occurred rapidly (<1 h). The refilling process was substantially slower when polyethylene glycol was added to the H2O source, thereby providing new support for an osmotically driven refilling mechanism. In contrast, segments not supplied with H2O showed no refilling and increased embolism formation. Dynamic changes in liquid/wall contact angles indicated that the processes of embolism removal (i.e. vessel refilling) by water influx and embolism formation by water efflux were directly linked to the activity of vessel-associated living tissue. Overall, our results emphasize that root pressure is not required as a driving force for vessel refilling, and care should be taken when performing hydraulics measurements on excised plant organs containing living vessel-associated tissue, because the vessel behavior may not be static. PMID:27208267

Xylem specific activation of 5’ upstream regulatory region of two NAC transcription factors (MusaVND6 and MusaVND7) in banana is regulated by SNBE-like sites

PubMed Central

2018-01-01

Deposition of secondary cell wall in the xylem elements is controlled by a subgroup of NAC (NAM, ATAF, CUC) family, known as vascular-related NAC transcription factors (VNDs). In the present study, we analyzed the 5’ upstream regulatory region of two banana NAC transcription factors (MusaVND6 and MusaVND7) for tissue specific expression and presence of 19-bp secondary-wall NAC binding element (SNBE)-like motifs. Transgenic banana plants of Musa cultivar Rasthali harboring either PMusaVND7::GUS or PMusaVND6::GUS showed specific GUS (β-D-Glucuronidase) activity in cells of the xylem tissue. Approximately 1.2kb promoter region of either MusaVND6 or MusaVND7 showed presence of at least two SNBE-like motifs. This 1.2kb promoter region was retarded in a gel shift assay by three banana VND protein (VND1,VND2 and VND3). The banana VND1-VND3 could also retard the mobility of isolated SNBE-like motifs of MusaVND6 or MusaVND7 in a gel shift assay. Transcript levels of MusaVND6 and MusaVND7 were elevated in transgenic banana overexpressing either banana VND1, VND2 or VND3. Present study suggested a probable regulation of banana VND6 and VND7 expression through direct interaction of banana VND1- VND3 with SNBE-like motifs. Our study also indicated two promoter elements for possible utilization in cell wall modifications in plants especially banana, which is being recently considered as a potential biofuel crop. PMID:29438404

Correlation of neurocognitive function and brain parenchyma volumes in children surviving cancer

NASA Astrophysics Data System (ADS)

Reddick, Wilburn E.; White, Holly A.; Glass, John O.; Mulhern, Raymond K.

2002-04-01

This research builds on our hypothesis that white matter damage and associated neurocognitive symptoms, in children treated for cancer with cranial spinal irradiation, spans a continuum of severity that can be reliably probed using non-invasive MR technology. Quantitative volumetric assessments of MR imaging and psychological assessments were obtained in 40 long-term survivors of malignant brain tumors treated with cranial irradiation. Neurocognitive assessments included a test of intellect (Wechsler Intelligence Test for Children, Wechsler Adult Intelligence Scale), attention (Conner's Continuous Performance Test), and memory (California Verbal Learning Test). One-sample t-tests were conducted to evaluate test performance of survivors against age-adjusted scores from the test norms; these analyses revealed significant impairments in all apriori selected measures of intelligence, attention, and memory. Partial correlation analyses were performed to assess the relationships between brain tissues volumes (normal appearing white matter (NAWM), gray matter, and CSF) and neurocognitive function. Global intelligence (r = 0.32, p = 0.05) and global attentional (r = 0.49, p < 0.01) were significantly positively correlated with NAWM volumes, whereas global memory was significantly positively correlated with overall brain parenchyma (r = 0.38, p = 0.04). We conclude that quantitative assessment of MR examinations in survivors of childhood cancer treated with cranial irradiation reveal that loss of NAWM is associated with decreased intellectual and attentional deficits, whereas overall parenchyma loss, as reflected by increased CSF and decreased white matter, is associated with memory-related deficits.

Effects of selective bile duct ligation on liver parenchyma in young animals: histologic and molecular evaluations.

PubMed

Tannuri, Ana Cristina A; Coelho, Maria Cecília M; de Oliveira Gonçalves, Josiane; Santos, Maria Mercês; Ferraz da Silva, Luiz Fernando; Bendit, Israel; Tannuri, Uenis

2012-03-01

The mechanisms of increased collagen production and liver parenchyma fibrosis are poorly understood. These phenomena are observed mainly in children with biliary obstruction (BO), and in a great number of patients, the evolution to biliary cirrhosis and hepatic failure leads to the need for liver transplantation before adolescence. However, pediatric liver transplantation presents with biliary complications in 20% to 30% of cases in the postoperative period. Intra- or extrahepatic stenosis of bile ducts is frequent and may lead to secondary biliary cirrhosis and the need for retransplantation. It is unknown whether biliary stenosis involving isolated segments or lobes may affect the adjacent nonobstructed lobes by paracrine or endocrine means, leading to fibrosis in this parenchyma. Therefore, the present study aimed to create an experimental model of selective biliary duct ligation in young animals with a subsequent evaluation of the histologic and molecular alterations in liver parenchyma of the obstructed and nonobstructed lobes. After a pilot study to standardize the surgical procedures, weaning rats underwent ligation of the bile ducts of the median, left lateral, and caudate liver lobes. The bile duct of the right lateral lobe was kept intact. To avoid intrahepatic biliary duct collaterals neoformation, the parenchymal connection between the right lateral and median lobes was clamped. The animals were divided into groups according to the time of death: 1, 2, 3, 4, and 8 weeks after surgical procedure. After death, the median and left lateral lobes (with BO) and the right lateral lobe (without BO [NBO]) were harvested separately. A group of 8 healthy nonoperated on animals served as controls. Liver tissues were subjected to histologic evaluation and quantification of the ductular proliferation and of the portal fibrosis. The expressions of smooth muscle α-actin (α-SMA), desmin, and transforming growth factor β1 genes were studied by molecular analyses

In Situ Visualization of the Dynamics in Xylem Embolism Formation and Removal in the Absence of Root Pressure: A Study on Excised Grapevine Stems.

PubMed

Knipfer, Thorsten; Cuneo, Italo F; Brodersen, Craig R; McElrone, Andrew J

2016-06-01

Gas embolisms formed during drought can disrupt long-distance water transport through plant xylem vessels, but some species have the ability to remove these blockages. Despite evidence suggesting that embolism removal is linked to the presence of vessel-associated parenchyma, the underlying mechanism remains controversial and is thought to involve positive pressure generated by roots. Here, we used in situ x-ray microtomography on excised grapevine stems to determine if embolism removal is possible without root pressure, and if the embolism formation/removal affects vessel functional status after sample excision. Our data show that embolism removal in excised stems was driven by water droplet growth and was qualitatively identical to refilling in intact plants. When stem segments were rehydrated with H2O after excision, vessel refilling occurred rapidly (<1 h). The refilling process was substantially slower when polyethylene glycol was added to the H2O source, thereby providing new support for an osmotically driven refilling mechanism. In contrast, segments not supplied with H2O showed no refilling and increased embolism formation. Dynamic changes in liquid/wall contact angles indicated that the processes of embolism removal (i.e. vessel refilling) by water influx and embolism formation by water efflux were directly linked to the activity of vessel-associated living tissue. Overall, our results emphasize that root pressure is not required as a driving force for vessel refilling, and care should be taken when performing hydraulics measurements on excised plant organs containing living vessel-associated tissue, because the vessel behavior may not be static. © 2016 American Society of Plant Biologists. All Rights Reserved.

Two phloem nitrate transporters, NRT1.11 and NRT1.12, are important for redistributing xylem-borne nitrate to enhance plant growth.

PubMed

Hsu, Po-Kai; Tsay, Yi-Fang

2013-10-01

This study of the Arabidopsis (Arabidopsis thaliana) nitrate transporters NRT1.11 and NRT1.12 reveals how the interplay between xylem and phloem transport of nitrate ensures optimal nitrate distribution in leaves for plant growth. Functional analysis in Xenopus laevis oocytes showed that both NRT1.11 and NRT1.12 are low-affinity nitrate transporters. Quantitative reverse transcription-polymerase chain reaction and immunoblot analysis showed higher expression of these two genes in larger expanded leaves. Green fluorescent protein and β-glucuronidase reporter analyses indicated that NRT1.11 and NRT1.12 are plasma membrane transporters expressed in the companion cells of the major vein. In nrt1.11 nrt1.12 double mutants, more root-fed (15)NO3(-) was translocated to mature and larger expanded leaves but less to the youngest tissues, suggesting that NRT1.11 and NRT1.12 are required for transferring root-derived nitrate into phloem in the major veins of mature and larger expanded leaves for redistributing to the youngest tissues. Distinct from the wild type, nrt1.11 nrt1.12 double mutants show no increase of plant growth at high nitrate supply. These data suggested that NRT1.11 and NRT1.12 are involved in xylem-to-phloem transfer for redistributing nitrate into developing leaves, and such nitrate redistribution is a critical step for optimal plant growth enhanced by increasing external nitrate.

Relationships among foliar phenology, radial growth rate, and xylem density in a young Douglas-fir plantation

Treesearch

Warren D. Devine; Constance A. Harrington

2009-01-01

We related intraannual patterns in radial growth rate and xylem density to foliar phenology and second growth flushes in a young Douglas-fir plantation in western Washington. Three foliar maturity classes were defined: (1) shoots and needles elongating; (2) elongation complete, needles maturing; and (3) needles mature. Diameter growth rate had two peaks, one about the...

Spatial and temporal patterns of xylem sap pH derived from stems and twigs of Populus deltoides L.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aubrey, Doug P.; Boyles, Justin G.; Krysinsky, Laura S.

2011-02-12

Xylem sap pH (pHX) is critical in determining the quantity of inorganic carbon dissolved in xylem solution from gaseous [CO2] measurements. Studies of internal carbon transport have generally assumed that pHX derived from stems and twigs is similar and that pHX remains constant through time; however, no empirical studies have investigated these assumptions. If any of these assumptions are violated, potentially large errors can be introduced into calculations of dissolved CO 2 in xylem and resulting estimates of internal carbon transport.Wetested the validity of assumptions related to pHX in Populus deltoides L. with a series of non-manipulative experiments. The pHXmore » derived from stems and twigs was generally similar and remained relatively constant through a diel period. The only exception was that pHX derived from lower stem sections at night was higher than that derived from twigs. The pHX derived from stems was similar on clear days when solar radiation and vapor pressure deficit (VPD) were similar, but higher on an overcast day when solar radiation and VPD were lower. Similarly, cloudy conditions immediately before an afternoon thunderstorm increased pHX derived from twigs. The pHX derived from twigs remained similar when measured on sunny afternoons between July and October. Our results suggest that common assumptions of pHX used in studies of internal carbon transport appear valid for P. deltoides and further suggest pHX is influenced by environmental factors, such as solar radiation and VPD that affect transpiration rates.« less

Xylem transport and gene expression play decisive roles in cadmium accumulation in shoots of two oilseed rape cultivars (Brassica napus).

PubMed

Wu, Zhichao; Zhao, Xiaohu; Sun, Xuecheng; Tan, Qiling; Tang, Yafang; Nie, Zhaojun; Hu, Chengxiao

2015-01-01

Cadmium (Cd) is a toxic metal which harms human health through food chains. The mechanisms underlying Cd accumulation in oilseed rape are still poorly understood. Here, we investigated the physiological and genetic processes involved in Cd uptake and transport of two oilseed rape cultivars (Brassica napus). L351 accumulates more Cd in shoots but less in roots than L338. A scanning ion-selective electrode technique (SIET) and uptake kinetics of Cd showed that roots were not responsible for the different Cd accumulation in shoots since L351 showed a lower Cd uptake ability. However, concentration-dependent and time-dependent dynamics of Cd transport by xylem showed L351 exhibited a superordinate capacity of Cd translocation to shoots. Additionally, the Cd concentrations of shoots and xylem sap showed a great correlation in both cultivars. Furthermore, gene expression levels related to Cd uptake by roots (IRT1) and Cd transport by xylem (HMA2 and HMA4) were consistent with the tendencies of Cd absorption and transport at the physiological level respectively. In other words, L351 had stronger gene expression for Cd transport but lower for Cd uptake. Overall, results revealed that the process of Cd translocation to shoots is a determinative factor for Cd accumulation in shoots, both at physiological and genetic levels. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

[The structure of vegetative organs, and saponins histochemical localization and content comparization in Polygala sibirica L].

PubMed

Teng, Hong Mei; Fang, Min Feng; Hu, Zheng Hai

2009-02-01

Anatomical, histochemical and phytochemistry methods were used to investigate the structure of vegetative organs, and saponins localization and dynamic changes in Polygala sibirica L. The root consisted of developed periderm and secondary vascular. The secondary phloem was thick, and mainly composed of parenchyma. There were well-developed vessels and fibers in the secondary xylem. The stem was composed of epidermis, cortex and vascular bundle. The ring of sclerenchymatous cells lied between cortex and phloem might be the apoplastic protective screen which could protect the stem from drought. The leaf was bifacial one. The root and stem possessed characteristics adapting to arid environment. Histochemical localization results showed that saponins distributed in secondary phloem and phelloderm of root, in epidermis, cortex and phloem of stem, mainly in mesophyll of leaf. It displayed that saponins accumulated mainly in parenchyma cells of vegetative organs, among of which, the secondary phloem was the main storage site. The HPLC results also showed that the saponins accumulated in all the vegetative organs of Polygala sibirica L., with higher content in roots and lower content in the aerial part that included stems and leaves. The study indicated the aerial part of Polygala sibirica L. also had medicinal value. The saponins content had dynamic variance at the developmental stage, the crude drug should be gathered at period from April to May.

An auxin-induced β-type endo-1,4-β-glucanase in poplar is involved in cell expansion and lateral root formation.

PubMed

Yu, Liangliang; Li, Qiong; Zhu, Yingying; Afzal, Muhammad Saddique; Li, Laigeng

2018-05-01

PtrGH9A7, a poplar β-type endo-1,4-β-glucanase gene induced by auxin, promotes both plant growth and lateral root development by enhancing cell expansion. Endo-1,4-β-glucanase (EGase) family genes function in multiple aspects of plant growth and development. Our previous study found that PtrCel9A6, a poplar EGase gene of the β subfamily, is specifically expressed in xylem tissue and is involved in the cellulose biosynthesis required for secondary cell wall formation (Yu et al. in Mol Plant 6:1904-1917, 2013). To further explore the functions and regulatory mechanism of β-subfamily EGases, we cloned and characterized another poplar β-type EGase gene PtrGH9A7, a close homolog of PtrCel9A6. In contrast to PtrCel9A6, PtrGH9A7 is predominantly expressed in parenchyma tissues of the above-ground part; in roots, PtrGH9A7 expression is specifically restricted to lateral root primordia at all stages from initiation to emergence and is strongly induced by auxin application. Heterologous overexpression of PtrGH9A7 promotes plant growth by enhancing cell expansion, suggesting a conserved role for β-type EGases in 1,4-β-glucan chains remodeling, which is required for cell wall loosening. Moreover, the overexpression of PtrGH9A7 significantly increases lateral root number, which might result from improved lateral root primordium development due to enhanced cell expansion. Taken together, these results demonstrate that this β-type EGase induced by auxin signaling has a novel role in promoting lateral root formation as well as in enhancing plant growth.

Ralstonia solanacearum uses inorganic nitrogen metabolism for virulence, ATP production, and detoxification in the oxygen-limited host xylem environment.

PubMed

Dalsing, Beth L; Truchon, Alicia N; Gonzalez-Orta, Enid T; Milling, Annett S; Allen, Caitilyn

2015-03-17

Genomic data predict that, in addition to oxygen, the bacterial plant pathogen Ralstonia solanacearum can use nitrate (NO3(-)), nitrite (NO2(-)), nitric oxide (NO), and nitrous oxide (N2O) as terminal electron acceptors (TEAs). Genes encoding inorganic nitrogen reduction were highly expressed during tomato bacterial wilt disease, when the pathogen grows in xylem vessels. Direct measurements found that tomato xylem fluid was low in oxygen, especially in plants infected by R. solanacearum. Xylem fluid contained ~25 mM NO3(-), corresponding to R. solanacearum's optimal NO3(-) concentration for anaerobic growth in vitro. We tested the hypothesis that R. solanacearum uses inorganic nitrogen species to respire and grow during pathogenesis by making deletion mutants that each lacked a step in nitrate respiration (ΔnarG), denitrification (ΔaniA, ΔnorB, and ΔnosZ), or NO detoxification (ΔhmpX). The ΔnarG, ΔaniA, and ΔnorB mutants grew poorly on NO3(-) compared to the wild type, and they had reduced adenylate energy charge levels under anaerobiosis. While NarG-dependent NO3(-) respiration directly enhanced growth, AniA-dependent NO2(-) reduction did not. NO2(-) and NO inhibited growth in culture, and their removal depended on denitrification and NO detoxification. Thus, NO3(-) acts as a TEA, but the resulting NO2(-) and NO likely do not. None of the mutants grew as well as the wild type in planta, and strains lacking AniA (NO2(-) reductase) or HmpX (NO detoxification) had reduced virulence on tomato. Thus, R. solanacearum exploits host NO3(-) to respire, grow, and cause disease. Degradation of NO2(-) and NO is also important for successful infection and depends on denitrification and NO detoxification systems. The plant-pathogenic bacterium Ralstonia solanacearum causes bacterial wilt, one of the world's most destructive crop diseases. This pathogen's explosive growth in plant vascular xylem is poorly understood. We used biochemical and genetic approaches to show

Ultrasound-mediated delivery and distribution of polymeric nanoparticles in the normal brain parenchyma of a metastatic brain tumour model

PubMed Central

Baghirov, Habib; Snipstad, Sofie; Sulheim, Einar; Berg, Sigrid; Hansen, Rune; Thorsen, Frits; Mørch, Yrr; Åslund, Andreas K. O.

2018-01-01

The treatment of brain diseases is hindered by the blood-brain barrier (BBB) preventing most drugs from entering the brain. Focused ultrasound (FUS) with microbubbles can open the BBB safely and reversibly. Systemic drug injection might induce toxicity, but encapsulation into nanoparticles reduces accumulation in normal tissue. Here we used a novel platform based on poly(2-ethyl-butyl cyanoacrylate) nanoparticle-stabilized microbubbles to permeabilize the BBB in a melanoma brain metastasis model. With a dual-frequency ultrasound transducer generating FUS at 1.1 MHz and 7.8 MHz, we opened the BBB using nanoparticle-microbubbles and low-frequency FUS, and applied high-frequency FUS to generate acoustic radiation force and push nanoparticles through the extracellular matrix. Using confocal microscopy and image analysis, we quantified nanoparticle extravasation and distribution in the brain parenchyma. We also evaluated haemorrhage, as well as the expression of P-glycoprotein, a key BBB component. FUS and microbubbles distributed nanoparticles in the brain parenchyma, and the distribution depended on the extent of BBB opening. The results from acoustic radiation force were not conclusive, but in a few animals some effect could be detected. P-glycoprotein was not significantly altered immediately after sonication. In summary, FUS with our nanoparticle-stabilized microbubbles can achieve accumulation and displacement of nanoparticles in the brain parenchyma. PMID:29338016

Transcriptomic analysis of wound xylem formation in Pinus canariensis.

PubMed

Chano, V; Collada, C; Soto, A

2017-12-04

Woody plants, especially trees, usually must face several injuries caused by different agents during their lives. Healing of injuries in stem and branches, affecting the vascular cambium and xylem can take several years. In conifers, healing takes place mainly from the remaining vascular cambium in the margin of the wound. The woundwood formed in conifers during healing usually presents malformed and disordered tracheids as well as abundant traumatic resin ducts. These characteristics affect its functionality as water conductor and its technological properties. In this work we analyze for the first time the transcriptomic basis of the formation of traumatic wood in conifers, and reveal some differences with normal early- and late-wood. Microarray analysis of the differentiating traumatic wood, confirmed by quantitative RT-PCR, has revealed alterations in the transcription profile of up to 1408 genes during the first period of healing. We have grouped these genes in twelve clusters, according to their transcription profiles, and have distinguished accordingly two main phases during this first healing. Wounding induces a complete rearrangement of the transcriptional program in the cambial zone close to the injuries. At the first instance, radial growth is stopped, and a complete set of defensive genes, mostly related to biotic stress, are induced. Later on, cambial activity is restored in the lateral borders of the wound, even at a high rate. During this second stage certain genes related to early-wood formation, including genes involved in cell wall formation and transcription factors, are significantly overexpressed, while certain late-wood related genes are repressed. Additionally, significant alterations in the transcription profile of abundant non annotated genes are reported.

Role of the node in controlling traffic of cadmium, zinc, and manganese in rice

PubMed Central

Yamaguchi, Noriko; Ishikawa, Satoru; Abe, Tadashi; Baba, Koji; Terada, Yasuko

2012-01-01

Heavy metals are transported to rice grains via the phloem. In rice nodes, the diffuse vascular bundles (DVBs), which enclose the enlarged elliptical vascular bundles (EVBs), are connected to the panicle and have a morphological feature that facilitates xylem-to-phloem transfer. To find a mechanism for restricting cadmium (Cd) transport into grains, the distribution of Cd, zinc (Zn), manganese (Mn), and sulphur (S) around the vascular bundles in node I (the node beneath the panicle) of Oryza sativa ‘Koshihikari’ were compared 1 week after heading. Elemental maps of Cd, Zn, Mn, and S in the vascular bundles of node I were obtained by synchrotron micro-X-ray fluorescence spectrometry and electron probe microanalysis. In addition, Cd K-edge microfocused X-ray absorption near-edge structure analyses were used to identify the elements co-ordinated with Cd. Both Cd and S were mainly distributed in the xylem of the EVB and in the parenchyma cell bridge (PCB) surrounding the EVB. Zn accumulated in the PCB, and Mn accumulated around the protoxylem of the EVB. Cd was co-ordinated mainly with S in the xylem of the EVB, but with both S and O in the phloem of the EVB and in the PCB. The EVB in the node retarded horizontal transport of Cd toward the DVB. By contrast, Zn was first stored in the PCB and then efficiently transferred toward the DVB. Our results provide evidence that transport of Cd, Zn, and Mn is differentially controlled in rice nodes, where vascular bundles are functionally interconnected. PMID:22291135

Analysis of spatial and temporal dynamics of xylem refilling in Acer rubrum L. using magnetic resonance imaging.

PubMed

Zwieniecki, Maciej A; Melcher, Peter J; Ahrens, Eric T

2013-01-01

We report results of an analysis of embolism formation and subsequent refilling observed in stems of Acer rubrum L. using magnetic resonance imaging (MRI). MRI is one of the very few techniques that can provide direct non-destructive observations of the water content within opaque biological materials at a micrometer resolution. Thus, it has been used to determine temporal dynamics and water distributions within xylem tissue. In this study, we found good agreement between MRI measures of pixel brightness to assess xylem liquid water content and the percent loss in hydraulic conductivity (PLC) in response to water stress (P50 values of 2.51 and 2.70 for MRI and PLC, respectively). These data provide strong support that pixel brightness is well correlated to PLC and can be used as a proxy of PLC even when single vessels cannot be resolved on the image. Pressure induced embolism in moderately stressed plants resulted in initial drop of pixel brightness. This drop was followed by brightness gain over 100 min following pressure application suggesting that plants can restore water content in stem after induced embolism. This recovery was limited only to current-year wood ring; older wood did not show signs of recovery within the length of experiment (16 h). In vivo MRI observations of the xylem of moderately stressed (~-0.5 MPa) A. rubrum stems revealed evidence of a spontaneous embolism formation followed by rapid refilling (~30 min). Spontaneous (not induced) embolism formation was observed only once, despite over 60 h of continuous MRI observations made on several plants. Thus this observation provide evidence for the presence of naturally occurring embolism-refilling cycle in A. rubrum, but it is impossible to infer any conclusions in relation to its frequency in nature.

Analysis of spatial and temporal dynamics of xylem refilling in Acer rubrum L. using magnetic resonance imaging

PubMed Central

Zwieniecki, Maciej A.; Melcher, Peter J.; Ahrens, Eric T.

2013-01-01

We report results of an analysis of embolism formation and subsequent refilling observed in stems of Acer rubrum L. using magnetic resonance imaging (MRI). MRI is one of the very few techniques that can provide direct non-destructive observations of the water content within opaque biological materials at a micrometer resolution. Thus, it has been used to determine temporal dynamics and water distributions within xylem tissue. In this study, we found good agreement between MRI measures of pixel brightness to assess xylem liquid water content and the percent loss in hydraulic conductivity (PLC) in response to water stress (P50 values of 2.51 and 2.70 for MRI and PLC, respectively). These data provide strong support that pixel brightness is well correlated to PLC and can be used as a proxy of PLC even when single vessels cannot be resolved on the image. Pressure induced embolism in moderately stressed plants resulted in initial drop of pixel brightness. This drop was followed by brightness gain over 100 min following pressure application suggesting that plants can restore water content in stem after induced embolism. This recovery was limited only to current-year wood ring; older wood did not show signs of recovery within the length of experiment (16 h). In vivo MRI observations of the xylem of moderately stressed (~-0.5 MPa) A. rubrum stems revealed evidence of a spontaneous embolism formation followed by rapid refilling (~30 min). Spontaneous (not induced) embolism formation was observed only once, despite over 60 h of continuous MRI observations made on several plants. Thus this observation provide evidence for the presence of naturally occurring embolism-refilling cycle in A. rubrum, but it is impossible to infer any conclusions in relation to its frequency in nature. PMID:23885258

Cloning, Developmental, and Tissue-Specific Expression of Sucrose:Sucrose 1-Fructosyl Transferase from Taraxacum officinale. Fructan Localization in Roots1

PubMed Central

Van den Ende, Wim; Michiels, An; Van Wonterghem, Dominik; Vergauwen, Rudy; Van Laere, André

2000-01-01

Sucrose:sucrose 1-fructosyl transferase (1-SST) is the key enzyme initiating fructan synthesis in Asteraceae. Using reverse transcriptase-PCR, we isolated the cDNA for 1-SST from Taraxacum officinale. The cDNA-derived amino acid sequence showed very high homology to other Asteracean 1-SSTs (Cichorium intybus 86%, Cynara scolymus 82%, Helianthus tuberosus 80%), but homology to 1-SST from Allium cepa (46%) and Aspergillus foetidus (18%) was much lower. Fructan concentrations, 1-SST activities, 1-SST protein, and mRNA concentrations were compared in different organs during vegetative and generative development of T. officinale plants. Expression of 1-SST was abundant in young roots but very low in leaves. 1-SST was also expressed at the flowering stages in roots, stalks, and receptacles. A good correlation was found between northern and western blots showing transcriptional regulation of 1-SST. At the pre-flowering stage, 1-SST mRNA concentrations and 1-SST activities were higher in the root phloem than in the xylem, resulting in the higher fructan concentrations in the phloem. Fructan localization studies indicated that fructan is preferentially stored in phloem parenchyma cells in the vicinity of the secondary sieve tube elements. However, inulin-like crystals occasionally appeared in xylem vessels. PMID:10806226

Casting light on xylem vulnerability in an herbaceous species reveals a lack of segmentation.

PubMed

Skelton, Robert P; Brodribb, Timothy J; Choat, Brendan

2017-04-01

Finding thresholds at which loss of plant functionality occurs during drought is critical for predicting future crop productivity and survival. Xylem resistance to embolism has been suggested as a key trait associated with water-stress tolerance. Although a substantial literature exists describing the vulnerability of woody stems to embolism, leaves and roots of herbaceous species remain under-represented. Also, little is known about vulnerability to embolism at a whole-plant scale or propagation of embolism within plants. New techniques to view the process of embolism formation provide opportunities to resolve long-standing questions. Here, we used multiple visual techniques, including X-ray micro-computed tomography and the optical vulnerability method, to investigate the spread of embolism within intact stems, leaves and roots of Solanum lycopersicum (common tomato). We found that roots, stems and leaves of tomato plants all exhibited similar vulnerability to embolism, suggesting that embolism rapidly propagates among tissues. Although we found scarce evidence for differentiation of xylem vulnerability among tissues at the scale of the whole plant, within a leaf the midrib embolized at higher water potentials than lower order veins. Substantial overlap between the onset of cavitation and incipient leaf damage suggests that cavitation represents a substantial damage to plants, but the point of lethal cavitation in this herbaceous species remains uncertain. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Seasonal abundance and spatio-temporal distribution of dominant xylem fluid-feeding hemiptera in vineyards of central Texas and surrounding habitats.

PubMed

Lauzière, Isabelle; Sheather, Simon; Mitchell, Forrest

2008-08-01

A survey of xylem fluid-feeding insects (Hemiptera) exhibiting potential for transmission of Xylella fastidiosa, the bacterium causing Pierce's disease of grapevine, was conducted from 2004 to 2006 in the Hill Country grape growing region of central Texas. Nineteen insect species were collected from yellow sticky traps. Among these, two leafhoppers and one spittlebug comprised 94.57% of the xylem specialists caught in this region. Homalodisca vitripennis (Germar), Graphocephala versuta (Say), and Clastoptera xanthocephala Germar trap catches varied significantly over time, with greatest counts usually recorded between May or June and August and among localities. A comparison of insect counts from traps placed inside and outside vineyards indicated that G. versuta is always more likely captured on the vegetation adjacent to the vineyard. C. xanthocephala was caught inside the vineyard during the summer. Between October and December, the natural habitat offers more suitable host plants, and insects were absent from the vineyards after the first freezes. H. vitripennis was caught in higher numbers inside the vineyards throughout the grape vegetative season. However, insects were also caught in the habitat near the affected crop throughout the year, and residual populations overwintering near vineyards were also recorded. This study shed new light on the fauna of xylem fluid-feeding insects of Texas. These results also provide critical information to vineyard managers for timely applications of insecticides before insect feeding and vectoring to susceptible grapevines.

Drought-induced xylem cavitation and hydraulic deterioration: risk factors for urban trees under climate change?

PubMed

Savi, Tadeja; Bertuzzi, Stefano; Branca, Salvatore; Tretiach, Mauro; Nardini, Andrea

2015-02-01

Urban trees help towns to cope with climate warming by cooling both air and surfaces. The challenges imposed by the urban environment, with special reference to low water availability due to the presence of extensive pavements, result in high rates of mortality of street trees, that can be increased by climatic extremes. We investigated the water relations and xylem hydraulic safety/efficiency of Quercus ilex trees growing at urban sites with different percentages of surrounding impervious pavements. Seasonal changes of plant water potential and gas exchange, vulnerability to cavitation and embolism level, and morpho-anatomical traits were measured. We found patterns of increasing water stress and vulnerability to drought at increasing percentages of impervious pavement cover, with a consequent reduction in gas exchange rates, decreased safety margins toward embolism development, and increased vulnerability to cavitation, suggesting the occurrence of stress-induced hydraulic deterioration. The amount of impermeable surface and chronic exposure to water stress influence the site-specific risk of drought-induced dieback of urban trees under extreme drought. Besides providing directions for management of green spaces in towns, our data suggest that xylem hydraulics is key to a full understanding of the responses of urban trees to global change. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Xylem formation can be modeled statistically as a function of primary growth and cambium activity.

PubMed

Huang, Jian-Guo; Deslauriers, Annie; Rossi, Sergio

2014-08-01

Primary (budburst, foliage and shoot) growth and secondary (cambium and xylem) growth of plants play a vital role in sequestering atmospheric carbon. However, their potential relationships have never been mathematically quantified and the underlying physiological mechanisms are unclear. We monitored primary and secondary growth in Picea mariana and Abies balsamea on a weekly basis from 2010 to 2013 at four sites over an altitudinal gradient (25-900 m) in the eastern Canadian boreal forest. We determined the timings of onset and termination through the fitted functions and their first derivative. We quantified the potential relationships between primary growth and secondary growth using the mixed-effects model. We found that xylem formation of boreal conifers can be modeled as a function of cambium activity, bud phenology, and shoot and needle growth, as well as species- and site-specific factors. Our model reveals that there may be an optimal mechanism to simultaneously allocate the photosynthetic products and stored nonstructural carbon to growth of different organs at different times in the growing season. This mathematical link can bridge phenological modeling, forest ecosystem productivity and carbon cycle modeling, which will certainly contribute to an improved prediction of ecosystem productivity and carbon equilibrium. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

How reliable are methods to assess xylem vulnerability to cavitation? The issue of 'open vessel' artifact in oaks.

PubMed

Martin-StPaul, N K; Longepierre, D; Huc, R; Delzon, S; Burlett, R; Joffre, R; Rambal, S; Cochard, H

2014-08-01

Three methods are in widespread use to build vulnerability curves (VCs) to cavitation. The bench drying (BD) method is considered as a reference because embolism and xylem pressure are measured on large branches dehydrating in the air, in conditions similar to what happens in nature. Two other methods of embolism induction have been increasingly used. While the Cavitron (CA) uses centrifugal force to induce embolism, in the air injection (AI) method embolism is induced by forcing pressurized air to enter a stem segment. Recent studies have suggested that the AI and CA methods are inappropriate in long-vesselled species because they produce a very high-threshold xylem pressure for embolism (e.g., P50) compared with what is expected from (i) their ecophysiology in the field (native embolism, water potential and stomatal response to xylem pressure) and (ii) the P50 obtained with the BD method. However, other authors have argued that the CA and AI methods may be valid because they produce VCs similar to the BD method. In order to clarify this issue, we assessed VCs with the three above-mentioned methods on the long-vesselled Quercus ilex L. We showed that the BD VC yielded threshold xylem pressure for embolism consistent with in situ measurements of native embolism, minimal water potential and stomatal conductance. We therefore concluded that the BD method provides a reliable estimate of the VC for this species. The CA method produced a very high P50 (i.e., less negative) compared with the BD method, which is consistent with an artifact related to the vessel length. The VCs obtained with the AI method were highly variable, producing P50 ranging from -2 to -8.2 MPa. This wide variability was more related to differences in base diameter among samples than to differences in the length of samples. We concluded that this method is probably subject to an artifact linked to the distribution of vessel lengths within the sample. Overall, our results indicate that the CA

Water relations of coastal and estuarine Rhizophora mangle: xylem pressure potential and dynamics of embolism formation and repair.

PubMed

Melcher, P J; Goldstein, G; Meinzer, F C; Yount, D E; Jones, T J; Holbrook, N M; Huang, C X

2001-01-01

Physiological traits related to water transport were studied in Rhizophora mangle (red mangrove) growing in coastal and estuarine sites in Hawaii. The magnitude of xylem pressure potential (P x ), the vulnerability of xylem to cavitation, the frequency of embolized vessels in situ, and the capacity of R. mangle to repair embolized vessels were evaluated with conventional and recently developed techniques. The osmotic potential of the interstitial soil water (π sw ) surrounding the roots of R. mangle was c. -2.6±5.52×10 -3 and -0.4±6.13×10 -3  MPa in the coastal and estuarine sites, respectively. Midday covered (non-transpiring) leaf water potentials (Ψ L ) determined with a pressure chamber were 0.6-0.8 MPa more positive than those of exposed, freely-transpiring leaves, and osmotic potential of the xylem sap (π x ) ranged from -0.1 to -0.3 MPa. Consequently, estimated midday values of P x (calculated by subtracting π x from covered Ψ L ) were about 1 MPa more positive than Ψ L determined on freely transpiring leaves. The differences in Ψ L between covered and transpiring leaves were linearly related to the transpiration rates. The slope of this relationship was steeper for the coastal site, suggesting that the hydraulic resistance was larger in leaves of coastal R. mangle plants. This was confirmed by both hydraulic conductivity measurements on stem segments and high-pressure flowmeter studies made on excised leafy twigs. Based on two independent criteria, loss of hydraulic conductivity and proportions of gas- and liquid-filled vessels in cryo-scanning electron microscope (cryo-SEM) images, the xylem of R. mangle plants growing at the estuarine site was found to be more vulnerable to cavitation than that of plants growing at the coastal site. However, the cryo-SEM analyses suggested that cavitation occurred more readily in intact plants than in excised branches that were air-dried in the laboratory. Cryo-SEM analyses also revealed that, in both sites

Measurement of imidacloprid in xylem fluid from eastern hemlock (Tsuga canadensis) by derivitization/GC/MS and ELISA

Treesearch

Anthony Lagalante; Peter Greenbacker; Jonathan Jones; Richard Turcotte; Bradley Onken

2007-01-01

Imidacloprid is a nonvolatile insecticide and its direct quantification is not possible by gas chromatography. In order to ascertain imidacloprid levels in soil and trunk injection treated trees, a sensitive and selective method has been developed using GC/MS to measure the imidacloprid levels in xylem fluid exudates. In May 2005, a stand of hemlock trees in West...

Zinc compartmentation in root, transport into xylem, and absorption into leaf cells in the hyperaccumulating species of Sedum alfredii Hance.

PubMed

Yang, Xiaoe; Li, Tingqiang; Yang, Juncheng; He, Zhenli; Lu, Lingli; Meng, Fanhua

2006-06-01

Sedum alfredii Hance can accumulate Zn in shoots over 2%. Leaf and stem Zn concentrations of the hyperaccumulating ecotype (HE) were 24- and 28-fold higher, respectively, than those of the nonhyperaccumulating ecotype (NHE), whereas 1.4-fold more Zn was accumulated in the roots of the NHE. Approximately 2.7-fold more Zn was stored in the root vacuoles of the NHE, and thus became unavailable for loading into the xylem and subsequent translocation to shoot. Long-term efflux of absorbed 65Zn indicated that 65Zn activity was 6.8-fold higher in shoots but 3.7-fold lower in roots of the HE. At lower Zn levels (10 and 100 microM), there were no significant differences in 65Zn uptake by leaf sections and intact leaf protoplasts between the two ecotypes except that 1.5-fold more 65Zn was accumulated in leaf sections of the HE than in those of the NHE after exposure to 100 microM for 48 h. At 1,000 microM Zn, however, approximately 2.1-fold more Zn was taken up by the HE leaf sections and 1.5-fold more 65Zn taken up by the HE protoplasts as compared to the NHE at exposure times >16 h and >10 min, respectively. Treatments with carbonyl cyanide m-chlorophenylhydrazone (CCCP) or ruptured protoplasts strongly inhibited 65Zn uptake into leaf protoplasts for both ecotypes. Citric acid and Val concentrations in leaves and stems significantly increased for the HE, but decreased or had minimal changes for the NHE in response to raised Zn levels. These results indicate that altered Zn transport across tonoplast in the root and stimulated Zn uptake in the leaf cells are the major mechanisms involved in the strong Zn hyperaccumulation observed in S. alfredii H.

Herbicides in vineyards reduce grapevine root mycorrhization and alter soil microorganisms and the nutrient composition in grapevine roots, leaves, xylem sap and grape juice.

PubMed

Zaller, Johann G; Cantelmo, Clemens; Santos, Gabriel Dos; Muther, Sandrina; Gruber, Edith; Pallua, Paul; Mandl, Karin; Friedrich, Barbara; Hofstetter, Ingrid; Schmuckenschlager, Bernhard; Faber, Florian

2018-06-03

Herbicides are increasingly applied in vineyards worldwide. However, not much is known on potential side effects on soil organisms or on the nutrition of grapevines (Vitis vinifera). In an experimental vineyard in Austria, we examined the impacts of three within-row herbicide treatments (active ingredients: flazasulfuron, glufosinate, glyphosate) and mechanical weeding on grapevine root mycorrhization; soil microorganisms; earthworms; and nutrient concentration in grapevine roots, leaves, xylem sap and grape juice. The three herbicides reduced grapevine root mycorrhization on average by 53% compared to mechanical weeding. Soil microorganisms (total colony-forming units, CFU) were significantly affected by herbicides with highest CFUs under glufosinate and lowest under glyphosate. Earthworms (surface casting activity, density, biomass, reproduction) or litter decomposition in soil were unaffected by herbicides. Herbicides altered nutrient composition in grapevine roots, leaves, grape juice and xylem sap that was collected 11 months after herbicide application. Xylem sap under herbicide treatments also contained on average 70% more bacteria than under mechanical weeding; however, due to high variability, this was not statistically significant. We conclude that interdisciplinary approaches should receive more attention when assessing ecological effects of herbicides in vineyard ecosystems.

Up-regulation of abscisic acid signaling pathway facilitates aphid xylem absorption and osmoregulation under drought stress.

PubMed

Guo, Huijuan; Sun, Yucheng; Peng, Xinhong; Wang, Qinyang; Harris, Marvin; Ge, Feng

2016-02-01

The activation of the abscisic acid (ABA) signaling pathway reduces water loss from plants challenged by drought stress. The effect of drought-induced ABA signaling on the defense and nutrition allocation of plants is largely unknown. We postulated that these changes can affect herbivorous insects. We studied the effects of drought on different feeding stages of pea aphids in the wild-type A17 of Medicago truncatula and ABA signaling pathway mutant sta-1. We examined the impact of drought on plant water status, induced plant defense signaling via the abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA) pathways, and on the host nutritional quality in terms of leaf free amino acid content. During the penetration phase of aphid feeding, drought decreased epidermis/mesophyll resistance but increased mesophyll/phloem resistance of A17 but not sta-1 plants. Quantification of transcripts associated with ABA, JA and SA signaling indicated that the drought-induced up-regulation of ABA signaling decreased the SA-dependent defense but increased the JA-dependent defense in A17 plants. During the phloem-feeding phase, drought had little effect on the amino acid concentrations and the associated aphid phloem-feeding parameters in both plant genotypes. In the xylem absorption stage, drought decreased xylem absorption time of aphids in both genotypes because of decreased water potential. Nevertheless, the activation of the ABA signaling pathway increased water-use efficiency of A17 plants by decreasing the stomatal aperture and transpiration rate. In contrast, the water potential of sta-1 plants (unable to close stomata) was too low to support xylem absorption activity of aphids; the aphids on sta-1 plants had the highest hemolymph osmolarity and lowest abundance under drought conditions. Taken together this study illustrates the significance of cross-talk between biotic-abiotic signaling pathways in plant-aphid interaction, and reveals the mechanisms leading to alter

Up-regulation of abscisic acid signaling pathway facilitates aphid xylem absorption and osmoregulation under drought stress

PubMed Central

Guo, Huijuan; Sun, Yucheng; Peng, Xinhong; Wang, Qinyang; Harris, Marvin; Ge, Feng

2016-01-01

The activation of the abscisic acid (ABA) signaling pathway reduces water loss from plants challenged by drought stress. The effect of drought-induced ABA signaling on the defense and nutrition allocation of plants is largely unknown. We postulated that these changes can affect herbivorous insects. We studied the effects of drought on different feeding stages of pea aphids in the wild-type A17 of Medicago truncatula and ABA signaling pathway mutant sta-1. We examined the impact of drought on plant water status, induced plant defense signaling via the abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA) pathways, and on the host nutritional quality in terms of leaf free amino acid content. During the penetration phase of aphid feeding, drought decreased epidermis/mesophyll resistance but increased mesophyll/phloem resistance of A17 but not sta-1 plants. Quantification of transcripts associated with ABA, JA and SA signaling indicated that the drought-induced up-regulation of ABA signaling decreased the SA-dependent defense but increased the JA-dependent defense in A17 plants. During the phloem-feeding phase, drought had little effect on the amino acid concentrations and the associated aphid phloem-feeding parameters in both plant genotypes. In the xylem absorption stage, drought decreased xylem absorption time of aphids in both genotypes because of decreased water potential. Nevertheless, the activation of the ABA signaling pathway increased water-use efficiency of A17 plants by decreasing the stomatal aperture and transpiration rate. In contrast, the water potential of sta-1 plants (unable to close stomata) was too low to support xylem absorption activity of aphids; the aphids on sta-1 plants had the highest hemolymph osmolarity and lowest abundance under drought conditions. Taken together this study illustrates the significance of cross-talk between biotic-abiotic signaling pathways in plant-aphid interaction, and reveals the mechanisms leading to alter

Sanio's laws revisited. Size-dependent changes in the xylem architecture of trees.

PubMed

Mencuccini, Maurizio; Hölttä, Teemu; Petit, Giai; Magnani, Federico

2007-11-01

Early observations led Sanio [Wissen. Bot., 8, (1872) 401] to state that xylem conduit diameters and lengths in a coniferous tree increase from the apex down to a height below which they begin to decrease towards the tree base. Sanio's law of vertical tapering has been repeatedly tested with contradictory results and the debate over the scaling of conduit diameters with distance from the apex has not been settled. The debate has recently acquired new vigour, as an accurate knowledge of the vertical changes in wood anatomy has been shown to be crucial to scaling metabolic properties to plant and ecosystem levels. Contrary to Sanio's hypothesis, a well known model (MST, metabolic scaling theory) assumes that xylem conduits monotonically increase in diameter with distance from the apex following a power law. This has been proposed to explain the three-fourth power scaling between size and metabolism seen across plants. Here, we (i) summarized available data on conduit tapering in trees and (ii) propose a new numerical model that could explain the observed patterns. Data from 101 datasets grouped into 48 independent profiles supported the notions that phylogenetic group (angiosperms versus gymnosperms) and tree size strongly affected the vertical tapering of conduit diameter. For both angiosperms and gymnosperms, within-tree tapering also varied with distance from the apex. The model (based on the concept that optimal conduit tapering occurs when the difference between photosynthetic gains and wall construction costs is maximal) successfully predicted all three major empirical patterns. Our results are consistent with Sanio's law only for large trees and reject the MST assumptions that vertical tapering in conduit diameter is universal and independent of rank number.

Tissue-dependent differences in the asynchronous appearance of mast cells in normal mice and in congenic mast cell-deficient mice after infusion of normal bone marrow cells

PubMed Central

DU, T; FRIEND, D S; AUSTEN, K F; KATZ, H R

1996-01-01

The time courses of the appearance of tissue mast cells in six sites were compared in normal WBB6F1-+/+ mice (+/+) and in congenic mast cell-deficient WBB6F1-W/Wv mice (W/Wv) that received an intravenous infusion of bone marrow cells from +/+mice (BM→W/Wv). As assessed by morphometric analysis of Carnoy's solution-fixed, methylene blue-stained tissue sections, the density of mast cells in the stomach mucosa, stomach submucosa, and spleen of +/+ mice reached maximal levels by 8 weeks of age, whereas the density of mast cells in the skin, extraparenchymal airway walls, and lung parenchyma did not reach maximal levels until 18 weeks of age. When 8-week-old W/Wv mice were infused with 2×107 bone marrow cells from +/+ mice, mast cells appeared in the stomach mucosa and submucosa after 2.5 weeks, in the spleen and extraparenchymal airway walls after 5 weeks, and in the lung parenchyma after 10 weeks. Twenty weeks after bone marrow infusion, the mast cell densities in the spleen, stomach mucosa, and stomach submucosa were seven-, 13-, and five-fold greater, respectively, than those in age-matched +/+ mice, but were eight-, two-, and five-fold lower in the skin, extraparenchymal airway walls, and lung parenchyma, respectively. Thus, those tissues that in +/+ mice reached maximal mast cell densities earlier exhibited abnormally high mast cell densities in BM→W/Wv mice, and those that reached maximal mast cell densities later in +/+ mice had abnormally low mast cell densities in BM→W/Wv mice. Immunological and inflammatory responses are often compared in W/Wv and BM→W/Wv mice to assess mast cell dependency. Our results indicate that the capacity to restore a mast cell-dependent response in a particular tissue of the latter mice may relate to the local mast cell density and whether the immunological challenge activates mast cells only in that tissue or systematically with attendant widespread release of proinflammatory mediators. PMID:8565318

Maximum height in a conifer is associated with conflicting requirements for xylem design.

PubMed

Domec, Jean-Christophe; Lachenbruch, Barbara; Meinzer, Frederick C; Woodruff, David R; Warren, Jeffrey M; McCulloh, Katherine A

2008-08-19

Despite renewed interest in the nature of limitations on maximum tree height, the mechanisms governing ultimate and species-specific height limits are not yet understood, but they likely involve water transport dynamics. Tall trees experience increased risk of xylem embolism from air-seeding because tension in their water column increases with height because of path-length resistance and gravity. We used morphological measurements to estimate the hydraulic properties of the bordered pits between tracheids in Douglas-fir trees along a height gradient of 85 m. With increasing height, the xylem structural modifications that satisfied hydraulic requirements for avoidance of runaway embolism imposed increasing constraints on water transport efficiency. In the branches and trunks, the pit aperture diameter of tracheids decreases steadily with height, whereas torus diameter remains relatively constant. The resulting increase in the ratio of torus to pit aperture diameter allows the pits to withstand higher tensions before air-seeding but at the cost of reduced pit aperture conductance. Extrapolations of vertical trends for trunks and branches show that water transport across pits will approach zero at a heights of 109 m and 138 m, respectively, which is consistent with historic height records of 100-127 m for this species. Likewise, the twig water potential corresponding to the threshold for runaway embolism would be attained at a height of approximately 107 m. Our results suggest that the maximum height of Douglas-fir trees may be limited in part by the conflicting requirements for water transport and water column safety.

A cell-cell signaling sensor is required for virulence and insect transmission of Xylella fastidiosa.

PubMed

Chatterjee, Subhadeep; Wistrom, Christina; Lindow, Steven E

2008-02-19

Cell-cell signaling in Xylella fastidiosa, a xylem-colonizing plant pathogenic bacterium, mediated by a fatty acid Diffusible Signaling Factor (DSF), is required to colonize insect vectors and to suppress virulence to grape. Here, we show that a hybrid two-component regulatory protein RpfC is involved in negative regulation of DSF synthesis by RpfF in X. fastidiosa. X. fastidiosa rpfC mutants hyperexpress rpfF and overproduce DSF and are deficient in virulence and movement in the xylem vessels of grape. The expression of the genes encoding the adhesins FimA, HxfA, and HxfB is much higher in rpfC mutants, which also exhibit a hyperattachment phenotype in culture that is associated with their inability to migrate in xylem vessels and cause disease. rpfF mutants deficient in DSF production have the opposite phenotypes for all of these traits. RpfC is also involved in the regulation of other signaling components including rpfG, rpfB, a GGDEF domain protein that may be involved in intracellular signaling by modulating the levels of cyclic-di-GMP, and the virulence factors tolC and pglA required for disease. rpfC mutants are able to colonize the mouthparts of insect vectors and wild-type strains but are not transmitted as efficiently to new host plants, apparently because of their high levels of adhesiveness. Because of the conflicting contributions of adhesiveness and other traits to movement within plants and vectoring to new host plants, X. fastidiosa apparently coordinates these traits in a population-size-dependent fashion involving accumulation of DSF.

Fast-growing Acer rubrum differs from slow-growing Quercus alba in leaf, xylem and hydraulic trait coordination responses to simulated acid rain.

PubMed

Medeiros, Juliana S; Tomeo, Nicholas J; Hewins, Charlotte R; Rosenthal, David M

2016-08-01

We investigated the effects of historic soil chemistry changes associated with acid rain, i.e., reduced soil pH and a shift from nitrogen (N)- to phosphorus (P)-limitation, on the coordination of leaf water demand and xylem hydraulic supply traits in two co-occurring temperate tree species differing in growth rate. Using a full-factorial design (N × P × pH), we measured leaf nutrient content, water relations, leaf-level and canopy-level gas exchange, total biomass and allocation, as well as stem xylem anatomy and hydraulic function for greenhouse-grown saplings of fast-growing Acer rubrum (L.) and slow-growing Quercus alba (L.). We used principle component analysis to characterize trait coordination. We found that N-limitation, but not P-limitation, had a significant impact on plant water relations and hydraulic coordination of both species. Fast-growing A. rubrum made hydraulic adjustments in response to N-limitation, but trait coordination was variable within treatments and did not fully compensate for changing allocation across N-availability. For slow-growing Q. alba, N-limitation engendered more strict coordination of leaf and xylem traits, resulting in similar leaf water content and hydraulic function across all treatments. Finally, low pH reduced the propensity of both species to adjust leaf water relations and xylem anatomical traits in response to nutrient manipulations. Our data suggest that a shift from N- to P-limitation has had a negative impact on the water relations and hydraulic function of A. rubrum to a greater extent than for Q. alba We suggest that current expansion of A. rubrum populations could be tempered by acidic N-deposition, which may restrict it to more mesic microsites. The disruption of hydraulic acclimation and coordination at low pH is emphasized as an interesting area of future study. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

A biomechanical perspective on the role of large stem volume and high water content in baobab trees (Adansonia spp.; Bombacaceae).

PubMed

Chapotin, Saharah Moon; Razanameharizaka, Juvet H; Holbrook, N Michele

2006-09-01

The stems of large trees serve in transport, storage, and support; however, the degree to which these roles are reflected in their morphology is not always apparent. The large, water-filled stems of baobab trees (Adansonia spp.) are generally assumed to serve a water storage function, yet recent studies indicate limited use of stored water. Through an analysis of wood structure and composition, we examined whether baobab morphology reflects biomechanical constraints rather than water storage capacity in the six Madagascar baobab species. Baobab wood has a high water content (up to 79%), low wood density (0.09-0.17 g · cm(-3)), high parenchyma content (69-88%), and living cells beyond 35 cm into the xylem from the cambium. Volumetric construction cost of the wood is several times lower than in more typical trees, and the elastic modulus approaches that of parenchyma tissue. Safety factors calculated from estimated elastic buckling heights were low, indicating that baobabs are not more overbuilt than other temperate and tropical trees, yet the energy investment in stem material is comparable to that in temperate deciduous trees. Furthermore, the elastic modulus of the wood decreases with water content, such that excessive water withdrawal from the stem could affect mechanical stability.

A structural review of foliar glands in Passiflora L. (Passifloraceae)

PubMed Central

da Costa Silva, Delmira; Flavia de Albuquerque Melo-de-Pinna, Gladys

2017-01-01

Extrafloral glands in Passifloraceae species have aroused the interest of many researchers because of their wide morphological diversity. The present work analyzed the foliar glands on 34 species of Passiflora from samples containing glands in the petiole and foliar blade fixed in 50% solution of formaldehyde-ethanol-acetic acid and stored in a 70% ethanol solution. For anatomical analyses, part of the material was embedded in Paraplast, longitudinally sectioned and double stained with safranin and astra blue. Scanning electron microscopy analysis was also carried out. To analyze the presence of sugars in the secretion of foliar glands, a glucose strip test was used. Based on the results of morphological, anatomical and glucose strip tests, the foliar secretory glands in Passiflora can be grouped into two categories: Type I glands, defined as nectaries, can be elevated or flattened, and can have a sugar content high enough to be detected by the glucose strip test analysis. Type II glands are elevated and did not show a positive reaction to the glucose strip test. From an anatomical viewpoint, glands characterized as extrafloral nectaries show a multistratified secretory epidermis, typically followed by two flat layers of nectariferous parenchyma with dense content. Internal to these layers, vascular bundles are immersed in the subsecretory parenchyma and terminate in phloem cells. On the other hand, type II glands show a single layer of elongated secretory epidermal cells. Internal to this single layer, parenchyma and vascular tissue with both phloem and xylem elements can be observed. The analyzed species show a wide diversity of gland shape and distribution, and the combined analysis of morphology, anatomy and preliminary tests for the presence of glucose in the exudate in different Passiflora subgenera suggests the occurrence of two categories of glands: nectaries and resin glands. PMID:29136029

Infarction and Laceration of Liver Parenchyma Caused by Wedged CO{sub 2} Venography Before TIPS Insertion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Theuerkauf, Ingo; Strunk, Holger; Brensing, Karl August

2001-01-15

We describe the fatal outcome of an elective TIPS procedure performed in a 43-year-old man with alcoholic cirrhosis. Wedged hepatic venography with CO{sub 2} was the reason for infarction and laceration of liver parenchyma resulting in a subcapsular hematoma and subsequent intra-abdominal bleeding. This is the first report of this complication after the use of CO{sub 2} in a cirrhotic patient.

Loss of water transport capacity due to xylem cavitation in roots of two CAM succulents.

PubMed

Linton, M J; Nobel, P S

1999-11-01

Loss of axial hydraulic conductance as a result of xylem cavitation was examined for roots of the Crassulacean acid metabolism (CAM) succulents Agave deserti and Opuntia ficus-indica. Vulnerability to cavitation was not correlated with either root size or vessel diameter. Agave deserti had a mean cavitation pressure of -0.93 ± 0.08 MPa by both an air-injection and a centrifugal method compared to -0.70 ± 0.02 MPa by the centrifugal method for O. ficus-indica, reflecting the greater tolerance of the former species to low water potentials in its native habitat. Substantial xylem cavitation would occur at a soil water potential of -0.25 MPa, resulting in a predicted 22% loss of conductance for A. deserti and 32% for O. ficus-indica. For an extended drought of 3 mo, further cavitation could cause a 69% loss of conductance for A. deserti and 62% for O. ficus-indica. A model of axial hydraulic flow based upon the cavitation response of these species predicted that water uptake rates are far below the maximum possible, owing to the high root water potentials of these desert succulents. Despite various shoot adaptations to aridity, roots of A. deserti and O. ficus-indica are highly vulnerable to cavitation, which partially limits water uptake in a wet soil but helps reduce water loss to a drying soil.

Water transport through tall trees: A vertically-explicit, analytical model of xylem hydraulic conductance in stems.

PubMed

Couvreur, Valentin; Ledder, Glenn; Manzoni, Stefano; Way, Danielle A; Muller, Erik B; Russo, Sabrina E

2018-05-08

Trees grow by vertically extending their stems, so accurate stem hydraulic models are fundamental to understanding the hydraulic challenges faced by tall trees. Using a literature survey, we showed that many tree species exhibit continuous vertical variation in hydraulic traits. To examine the effects of this variation on hydraulic function, we developed a spatially-explicit, analytical water transport model for stems. Our model allows Huber ratio, stem-saturated conductivity, pressure at 50% loss of conductivity, leaf area, and transpiration rate to vary continuously along the hydraulic path. Predictions from our model differ from a matric flux potential model parameterized with uniform traits. Analyses show that cavitation is a whole-stem emergent property resulting from nonlinear pressure-conductivity feedbacks that, with gravity, cause impaired water transport to accumulate along the path. Because of the compounding effects of vertical trait variation on hydraulic function, growing proportionally more sapwood and building tapered xylem with height, as well as reducing xylem vulnerability only at branch tips while maintaining transport capacity at the stem base, can compensate for these effects. We therefore conclude that the adaptive significance of vertical variation in stem hydraulic traits is to allow trees to grow tall and tolerate operating near their hydraulic limits. This article is protected by copyright. All rights reserved.

Characterization of histological subtypes of clear cell renal cell carcinoma using contrast-enhanced ultrasound (CEUS).

PubMed

Reimann, R; Rübenthaler, J; Hristova, P; Staehler, M; Reiser, M; Clevert, D A

2015-10-16

The aim of this study was to analyze the histological subtypes of clear cell renal cell carcinoma (RCC) examined by means of contrast-enhanced ultrasound (CEUS) and a second generation blood pool agent (SonoVue®, Bracco, Milan, Italy) during the pre-operative phase. 29 patients with histologically proven subtypes of clear cell RCC were examined. A total of three patients were diagnosed with highly differentiated clear cell RCC, 21 out of 29 cases with moderately differentiated clear cell RCC and five out of 29 patients had insufficiently differentiated clear cell RCC. An experienced radiologist examined the patients with CEUS. The following parameters were analyzed: maximum signal intensity (PEAK), time elapsed until PEAK is reached (MTT), local blood flow (RBF), area under the time intensity curve (AUC) and the signal intensity (SI) during the course of time. For the groups all comparisons are made based on healthy renal parenchyma. In the clear cell RCC significant differences (significance level p < 0.05) between cancerous tissue and the healthy renal parenchyma were noticed in all four parameters. Therefore, the clear cell RCC stands out due to its reduced blood volume. However, it reached the PEAK reading relatively rapidly and its signal intensity was always lower than that of the healthy renal parenchyma. In the arterial phase retarded absorption of the contrast agent was observed, followed by fast washing out of the contrast agent bubbles.In all three histological subgroups no significant differences were noticed in PEAK and SI. However, the diagrams showed the possible bias, that the group of the insufficiently differentiated clear cell RCC had the highest PEAK-value and the highest signal intensity when compared with highly and moderately differentiated clear cell RCC. Our study suggests that CEUS may be an additional tool for non-invasive characterisation and differentiation of the three histological subtypes of clear cell RCC. Furthermore, it seems

Xylem and Leaf Functional Adjustments to Drought in Pinus sylvestris and Quercus pyrenaica at Their Elevational Boundary

PubMed Central

Fernández-de-Uña, Laura; Rossi, Sergio; Aranda, Ismael; Fonti, Patrick; González-González, Borja D.; Cañellas, Isabel; Gea-Izquierdo, Guillermo

2017-01-01

Climatic scenarios for the Mediterranean region forecast increasing frequency and intensity of drought events. Consequently, a reduction in Pinus sylvestris L. distribution range is projected within the region, with this species being outcompeted at lower elevations by more drought-tolerant taxa such as Quercus pyrenaica Willd. The functional response of these species to the projected shifts in water availability will partially determine their performance and, thus, their competitive success under these changing climatic conditions. We studied how the cambial and leaf phenology and xylem anatomy of these two species responded to a 3-year rainfall exclusion experiment set at their elevational boundary in Central Spain. Additionally, P. sylvestris leaf gas exchange, water potential and carbon isotope content response to the treatment were measured. Likewise, we assessed inter-annual variability in the studied functional traits under control and rainfall exclusion conditions. Prolonged exposure to drier conditions did not affect the onset of xylogenesis in either of the studied species, whereas xylem formation ceased 1–3 weeks earlier in P. sylvestris. The rainfall exclusion had, however, no effect on leaf phenology on either species, which suggests that cambial phenology is more sensitive to drought than leaf phenology. P. sylvestris formed fewer, but larger tracheids under dry conditions and reduced the proportion of latewood in the tree ring. On the other hand, Q. pyrenaica did not suffer earlywood hydraulic diameter changes under rainfall exclusion, but experienced a cumulative reduction in latewood width, which could ultimately challenge its hydraulic performance. The phenological and anatomical response of the studied species to drought is consistent with a shift in resource allocation under drought stress from xylem to other sinks. Additionally, the tighter stomatal control and higher intrinsic water use efficiency observed in drought-stressed P. sylvestris

Xylem and Leaf Functional Adjustments to Drought in Pinus sylvestris and Quercus pyrenaica at Their Elevational Boundary.

PubMed

Fernández-de-Uña, Laura; Rossi, Sergio; Aranda, Ismael; Fonti, Patrick; González-González, Borja D; Cañellas, Isabel; Gea-Izquierdo, Guillermo

2017-01-01

Climatic scenarios for the Mediterranean region forecast increasing frequency and intensity of drought events. Consequently, a reduction in Pinus sylvestris L. distribution range is projected within the region, with this species being outcompeted at lower elevations by more drought-tolerant taxa such as Quercus pyrenaica Willd. The functional response of these species to the projected shifts in water availability will partially determine their performance and, thus, their competitive success under these changing climatic conditions. We studied how the cambial and leaf phenology and xylem anatomy of these two species responded to a 3-year rainfall exclusion experiment set at their elevational boundary in Central Spain. Additionally, P. sylvestris leaf gas exchange, water potential and carbon isotope content response to the treatment were measured. Likewise, we assessed inter-annual variability in the studied functional traits under control and rainfall exclusion conditions. Prolonged exposure to drier conditions did not affect the onset of xylogenesis in either of the studied species, whereas xylem formation ceased 1-3 weeks earlier in P. sylvestris . The rainfall exclusion had, however, no effect on leaf phenology on either species, which suggests that cambial phenology is more sensitive to drought than leaf phenology. P. sylvestris formed fewer, but larger tracheids under dry conditions and reduced the proportion of latewood in the tree ring. On the other hand, Q. pyrenaica did not suffer earlywood hydraulic diameter changes under rainfall exclusion, but experienced a cumulative reduction in latewood width, which could ultimately challenge its hydraulic performance. The phenological and anatomical response of the studied species to drought is consistent with a shift in resource allocation under drought stress from xylem to other sinks. Additionally, the tighter stomatal control and higher intrinsic water use efficiency observed in drought-stressed P. sylvestris

A quorum sensing-defective mutant of Pectobacterium carotovorum ssp. brasiliense 1692 is attenuated in virulence and unable to occlude xylem tissue of susceptible potato plant stems.

PubMed

Moleleki, Lucy Novungayo; Pretorius, Rudolph Gustav; Tanui, Collins Kipngetich; Mosina, Gabolwelwe; Theron, Jacques

2017-01-01

Pectobacterium carotovorum ssp. brasiliense 1692 (Pcb1692) is an important emerging pathogen of potatoes causing blackleg in the field and soft rot during post-harvest storage. Blackleg diseases involve the bacterial colonization of vascular tissue and the formation of aggregates, also known as biofilms. To understand the role of quorum sensing in vascular colonization by Pcb1692, we generated a Pcb1692ΔexpI mutant strain. Inactivation of expI led to the reduced production of plant cell wall-degrading enzymes (PCWDEs), the inability to produce acyl homoserine lactone (AHL) and reduced virulence in potato tubers and stems. Complementation of the mutant strain with the wild-type expI gene in trans successfully restored AHL and PCWDE production as well as virulence. Transmission electron microscopy and in vitro motility assays demonstrated hyperpiliation and loss of flagella and swimming motility in the mutant strain compared with the wild-type Pcb1692. Furthermore, we noted that, in the early stages of infection, Pcb1692 wild-type cells had intact flagella which were shed at the later stages of infection. Confocal laser microscopy of PcbΔexpI-inoculated plants showed that the mutant strain tended to aggregate in intercellular spaces, but was unable to transit to xylem tissue. On the contrary, the wild-type strain was often observed forming aggregates within xylem tissue of potato stems. Gene expression analyses confirmed that flagella are part of the quorum sensing regulon, whereas fimbriae and pili appear to be negatively regulated by quorum sensing. The relative expression levels of other important putative virulence genes, such as those encoding different groups of PCWDEs, were down-regulated in the mutant compared with the wild-type strain. © 2016 BSPP and John Wiley & Sons Ltd.

Radiologic imaging of the renal parenchyma structure and function.

PubMed

Grenier, Nicolas; Merville, Pierre; Combe, Christian

2016-06-01

Radiologic imaging has the potential to identify several functional and/or structural biomarkers of acute and chronic kidney diseases that are useful diagnostics to guide patient management. A renal ultrasound examination can provide information regarding the gross anatomy and macrostructure of the renal parenchyma, and ultrasound imaging modalities based on Doppler or elastography techniques can provide haemodynamic and structural information, respectively. CT is also able to combine morphological and functional information, but the use of CT is limited due to the required exposure to X-ray irradiation and a risk of contrast-induced nephropathy following intravenous injection of a radio-contrast agent. MRI can be used to identify a wide range of anatomical and physiological parameters at the tissue and even cellular level, such as tissue perfusion, oxygenation, water diffusion, cellular phagocytic activity, tissue stiffness, and level of renal filtration. The ability of MRI to provide valuable information for most of these parameters within a renal context is still in development and requires more clinical experience, harmonization of technical procedures, and an evaluation of reliability and validity on a large scale.

Freezing pattern and frost killing temperature of apple (Malus domestica) wood under controlled conditions and in nature.

PubMed

Pramsohler, Manuel; Hacker, Jürgen; Neuner, Gilbert

2012-07-01

The freezing pattern and frost killing temperatures of apple (Malus domestica Borkh.) xylem were determined by differential thermal analysis and infrared differential thermal analysis (IDTA). Results from detached or attached twigs in controlled freezing experiments and during natural field freezing of trees were compared. Non-lethal freezing of apoplastic water in apple xylem as monitored during natural winter frosts in the field occurred at -1.9 ± 0.4 °C and did not change seasonally. The pattern of whole tree freezing was variable and specific to the environmental conditions. On detached twigs high-temperature freezing exotherms (HTEs) occurred 2.8 K below the temperature observed under natural frosts in the field with a seasonal mean of -4.7 ± 0.5 °C. Microporous apple xylem showed freezing without a specific pattern within a few seconds in IDTA images during HTEs, which is in contrast to macroporous xylem where a 2D freezing pattern mirrors anatomical structures. The pith tissue always remained unfrozen. Increasing twig length increased ice nucleation temperature; for increased twig diameter the effect was not significant. In attached twigs frozen in field portable freezing chambers, HTEs were recorded at a similar mean temperature (-4.6 ± 1.0 °C) to those for detached twigs. Upon lethal intracellular freezing of apple xylem parenchyma cells (XPCs) low-temperature freezing exotherms (LTEs) can be recorded. Low-temperature freezing exotherms determined on detached twigs varied significantly between a winter minimum of -36.9 °C and a summer maximum -12.7 °C. Within the temperature range wherein LTEs were recorded by IDTA in summer (-12.7 ± 0.5 to -20.3 ± 1.1 °C) various tiny clearly separated discontinuous freezing events could be detected similar to that in other species with contrasting XPC anatomy. These freezing events appeared to be initially located in the primary and only later in the secondary xylem. During the LTE no

Persistent T2*-hypointensity of the liver parenchyma after irradiation to the SPIO-accumulated liver: An imaging marker for responses to radiotherapy in hepatic malignancies.

PubMed

Furuta, Toshihiro; Yamaguchi, Masayuki; Minami, Manabu; Ohtomo, Kuni; Fujii, Hirofumi

2017-01-01

To determine whether T2*-weighted MRI has the ability to visualize the irradiated liver parenchyma and liver tumor after irradiation to the previously superparamagnetic iron oxide (SPIO)-accumulated liver. We examined 24 liver tumor-bearing rats. Nine rats (Group 1) received 20 µmol Fe/kg SPIO and subsequent 70-Gy irradiation to the tumor-bearing liver lobe. Four rats (Group 2) received SPIO and sham irradiation. Six rats (Group 3) received saline and irradiation. Finally, five rats (Group 4) received saline and sham irradiation. We acquired sequential 3 Tesla T2*-weighted images of the liver on day 7, and assessed MR image findings including signal intensity of the tumors and tumor-bearing liver lobes. In six rats in Group 1, tumors shrunk by 39-100% (303-0 mm 3 ), and severely, well-defined hypointense irradiated areas were observed. In the other two rats, tumors enlarged by 25 and 172% (595 and 1148 mm 3 ), and hypointense rings surrounded the tumors. The normalized relative signal intensity of the irradiated areas was significantly lower than that of the tumor (0.53 ± 0.06 versus 0.94 ± 0.06; P < 0.05). The severely, well-defined hypointense areas were not observed in the other groups. Histologically, necrotic regions dominated and minimal nonnecrotic tumor cells remained in irradiated areas. The number of CD68-positive cells was higher in irradiated areas than in nonirradiated areas. T2*-weighted MR imaging visualized the irradiated liver parenchyma as markedly, well-defined hypointense areas and liver cancer lesions as hyperintense areas only when SPIO was administered before irradiation. The visualization of the hypointense area was associated with tumor regression after irradiation. 2 J. Magn. Reson. Imaging 2017;45:303-312. © 2016 International Society for Magnetic Resonance in Medicine.

Pattern of xylem phenology in conifers of cold ecosystems at the Northern Hemisphere.

PubMed

Rossi, Sergio; Anfodillo, Tommaso; Čufar, Katarina; Cuny, Henri E; Deslauriers, Annie; Fonti, Patrick; Frank, David; Gričar, Jožica; Gruber, Andreas; Huang, Jian-Guo; Jyske, Tuula; Kašpar, Jakub; King, Gregory; Krause, Cornelia; Liang, Eryuan; Mäkinen, Harri; Morin, Hubert; Nöjd, Pekka; Oberhuber, Walter; Prislan, Peter; Rathgeber, Cyrille B K; Saracino, Antonio; Swidrak, Irene; Treml, Václav

2016-11-01

The interaction between xylem phenology and climate assesses forest growth and productivity and carbon storage across biomes under changing environmental conditions. We tested the hypothesis that patterns of wood formation are maintained unaltered despite the temperature changes across cold ecosystems. Wood microcores were collected weekly or biweekly throughout the growing season for periods varying between 1 and 13 years during 1998-2014 and cut in transverse sections for assessing the onset and ending of the phases of xylem differentiation. The data set represented 1321 trees belonging to 10 conifer species from 39 sites in the Northern Hemisphere and covering an interval of mean annual temperature exceeding 14 K. The phenological events and mean annual temperature of the sites were related linearly, with spring and autumnal events being separated by constant intervals across the range of temperature analysed. At increasing temperature, first enlarging, wall-thickening and mature tracheids appeared earlier, and last enlarging and wall-thickening tracheids occurred later. Overall, the period of wood formation lengthened linearly with the mean annual temperature, from 83.7 days at -2 °C to 178.1 days at 12 °C, at a rate of 6.5 days °C -1 . April-May temperatures produced the best models predicting the dates of wood formation. Our findings demonstrated the uniformity of the process of wood formation and the importance of the environmental conditions occurring at the time of growth resumption. Under warming scenarios, the period of wood formation might lengthen synchronously in the cold biomes of the Northern Hemisphere. © 2016 John Wiley & Sons Ltd.

Tissue and cell-type co-expression networks of transcription factors and wood component genes in Populus trichocarpa.

PubMed

Shi, Rui; Wang, Jack P; Lin, Ying-Chung; Li, Quanzi; Sun, Ying-Hsuan; Chen, Hao; Sederoff, Ronald R; Chiang, Vincent L

2017-05-01

Co-expression networks based on transcriptomes of Populus trichocarpa major tissues and specific cell types suggest redundant control of cell wall component biosynthetic genes by transcription factors in wood formation. We analyzed the transcriptomes of five tissues (xylem, phloem, shoot, leaf, and root) and two wood forming cell types (fiber and vessel) of Populus trichocarpa to assemble gene co-expression subnetworks associated with wood formation. We identified 165 transcription factors (TFs) that showed xylem-, fiber-, and vessel-specific expression. Of these 165 TFs, 101 co-expressed (correlation coefficient, r > 0.7) with the 45 secondary cell wall cellulose, hemicellulose, and lignin biosynthetic genes. Each cell wall component gene co-expressed on average with 34 TFs, suggesting redundant control of the cell wall component gene expression. Co-expression analysis showed that the 101 TFs and the 45 cell wall component genes each has two distinct groups (groups 1 and 2), based on their co-expression patterns. The group 1 TFs (44 members) are predominantly xylem and fiber specific, and are all highly positively co-expressed with the group 1 cell wall component genes (30 members), suggesting their roles as major wood formation regulators. Group 1 TFs include a lateral organ boundary domain gene (LBD) that has the highest number of positively correlated cell wall component genes (36) and TFs (47). The group 2 TFs have 57 members, including 14 vessel-specific TFs, and are generally less correlated with the cell wall component genes. An exception is a vessel-specific basic helix-loop-helix (bHLH) gene that negatively correlates with 20 cell wall component genes, and may function as a key transcriptional suppressor. The co-expression networks revealed here suggest a well-structured transcriptional homeostasis for cell wall component biosynthesis during wood formation.

Parametric imaging of clear cell and papillary renal cell carcinoma using contrast-enhanced ultrasound (CEUS).

PubMed

Rübenthaler, J; Reimann, R; Hristova, P; Staehler, M; Reiser, M; Clevert, D A

2015-10-16

The aim of this study was to analyse clear cell and papillary renal cell carcinoma (RCC) examined with contrast-enhanced ultrasound (CEUS) and a second generation blood pool agent (SonoVue®, Bracco, Milan, Italy) before clinical intervention. A total of 41 patients with histologically proven subtypes of RCC were examined. 29 patients had a clear cell RCC and 12 patients showed a papillary RCC. Average size in the clear cell RCC group was 6.07 cm and 1.88 cm in the papillary RCC group. An experienced radiologist examined all patients with CEUS. The following parameters were analysed: maximum signal intensity (PEAK), time elapsed until PEAK is reached (MTT), local blood flow (RBF), area under the time intensity curve (AUC) and the signal intensity (SI) during the course of time. For both groups all comparisons were made based on healthy renal parenchyma. In the clear cell RCC significant differences (significance level p < 0.05) between cancerous tissue and the healthy renal parenchyma were noticed in all four parameters. The clear cell RCC showed a significant reduced blood volume. It reached the PEAK reading relatively rapidly and its signal intensity was always lower than that of the healthy renal parenchyma. In the arterial phase retarded absorption of the contrast agent was observed, followed by fast washing out of the contrast agent bubbles.In the papillary RCC group, significant findings as to PEAK and RBF as well as a slightly significant difference as to AUC were recorded. The papillary RCC had a lower blood supply and reached its PEAK reading later. Its signal intensity was also reduced. The signal intensity of papillary NCC was significantly lower compared with clear cell RCC; absorption and washing out of the contrast agent was delayed. CEUS seems to be an useful additional method to clinically differentiate between clear cell and papillary RCC. In daily clinical use, patients with contraindication for other imaging methods, especially the

Fluconazole penetration in cerebral parenchyma in humans at steady state.

PubMed Central

Thaler, F; Bernard, B; Tod, M; Jedynak, C P; Petitjean, O; Derome, P; Loirat, P

1995-01-01

We studied fluconazole penetration in the brain in five patients who had a deep cerebral tumor whose removal required the excision of healthy brain tissue. Plasma and brain samples were simultaneously obtained after oral ingestion of 400 mg of fluconazole daily for 4 days (90% of steady state). Fluconazole penetration in healthy cerebral parenchyma was determined. Plasma and brain samples were assayed by high-pressure liquid chromatography. Concentrations in plasma and brain tissue were 13.5 +/- 5.5 micrograms/ml and 17.6 +/- 6.6 micrograms/g, respectively. The average ratio of concentrations in the brain and plasma (four patients) was 1.33 (range, 0.70 to 2.39). Despite the lack of data concerning the penetration of fluconazole in brain abscesses, these results should permit the use of a daily dose of 400 mg of fluconazole in prospective clinical studies that evaluate the effectiveness of this drug in the treatment of brain abscesses due to susceptible species of fungi. PMID:7625804

Senescence-Induced Serotonin Biosynthesis and Its Role in Delaying Senescence in Rice Leaves1[C][W][OA

PubMed Central