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PubMed1977

Comparison of vegetative anatomy of piperales. I. Juvenile xylem of twigs.

Medullary bundles of Piperaceae resemble those of Ranunculaceae. The nature of tracheary elements of primary xylem suggests that Houttuynia cordata (Saururaceae), Piper cubeba (Piperaceae) and Chloranthus officinalis (Chloranthaceae) are of lower evolutionary status than others. Among these three, P. cubeba shows stratification of secondary xylem, a specialized character. Lateral wall of metaxylem tracheary elements and distribution of bundles of Peperomia, suggest their primitive status and distinctness, supporting separation of "Peperomiacea:" (of NOVAK). Piper cubeba, Houttuynia and Chloranthus bear one important Ranunculaceous character: scalariform perforation in primary vessels. Primitive species of Peperomia carry probably another Ranunculaceous character, i.e., many circles of medullary bundles. Shape and pattern of vascular bundles of Piper cubeba, Houttuynia and Chloranthus are similar. Other species of Piper show modifications. Peperomia represents another distinct pattern.

Plants↗
PubMed2006

Diurnal differences in the supply of glucomannans and xylans to innermost surface of cell walls at various developmental stages from cambium to mature xylem in Cryptomeria japonica.

We investigated the diurnal differences in the innermost surface of tracheid cell walls at various developmental stages from cambium to mature xylem. Cryptomeria japonica saplings were cultivated in a growth chamber with a light cycle set at 14 h of light and 10 h of darkness. Samples were collected from the saplings during both the light and dark periods. The innermost surface of cell walls was immunogold-labeled with anti-glucomannan or anti-xylan antiserum and was observed by field emission scanning electron microscopy. Diurnal differences in the aspect of the innermost surface of cell walls were seen only in S(2)-layer-forming tracheids; cellulose microfibrils were clearly evident during the light period, and amorphous material containing glucomannans and xylans was prevalent during the dark period. Cellulose microfibrils were present at the primary-wall formation and S(1)-layer-forming stages, and many warts were observed in the mature tracheids, regardless of the time of sampling. The densities of labeled glucomannans on the innermost surface of cell walls in S(1)- and S(2)-forming tracheids and of labeled xylans in S(2)-forming tracheids during the dark period were significantly higher than those during the light period. These results suggest a diurnal periodicity in the supply of cell wall matrix containing hemicellulose to the innermost surface of developing secondary walls.

Cell Wall↗
PubMed1964

THE DEVELOPMENT OF THE SECONDARY WALL OF THE XYLEM IN ACER PSEUDOPLATANUS.

The development of the spirally thickened xylem element from a cambium initial of sycamore Acer pseudoplatanus has been traced by means of electron microscopy. The narrow elongated cambial initial undergoes considerable expansion in all dimensions. The cytoplasm at this stage is distributed in a thin skin between the cell wall and a large vacuole. No correlation has been observed between the distribution of any organelle and the pattern of the eventual thickenings. After the sites of thickening deposition have become apparent, the most conspicuous feature of the cell is the proliferation of Golgi bodies and vesicles. It is suggested that the material of the developing thickenings stems from direct apposition of the material in the Golgi vesicles. After glutaraldehyde fixation, microtubules (200 to 220 A in diameter) are seen to be sited in specific relation to the thickenings, the orientation of the tubules mirroring that of the fibrils seen in the thickenings. Possible reasons for absence of an observable pattern in the expanded but relatively undifferentiated cell are given, and the possible roles of the Golgi apparatus and microtubules in the thickening production are discussed

Acer↗
PubMed2005

Drought effects on hydraulic conductivity and xylem vulnerability to embolism in diverse species and provenances of Mediterranean cedars.

We studied hydraulic traits of young plants of the Mediterranean cedar species Cedrus atlantica (Endl.) G. Manetti ex Carrière (Luberon, France), C. brevifolia (Hook. f.) Henry (Cyprus), C. libani A. Rich (Hadeth El Jebbe, Lebanon) and C. libani (Armut Alani, Turkey). With an optimum water supply, no major differences were observed among species or provenances in either stem hydraulic conductivity (Ks) or leaf specific conductivity (Kl) measured on the main shoot. A moderate soil drought applied for 10 weeks induced marked acclimation through a reduction in Ks, particularly in the Lebanese provenance of C. libani, and a decrease in tracheid lumen size in all species. Cedrus atlantica, which had the smallest tracheids, was the species most vulnerable to embolism: a 50% loss in hydraulic conductivity (PsiPLC50) occurred at a water potential of -4.4 MPa in the well-watered treatment, and at -6.0 MPa in the moderate drought treatment. In the other species, PsiPLC50 was unaffected by moderate soil drought, and only declined sharply at water potentials between -6.4 and -7.5 MPa in both irrigation treatments. During severe drought, Ks of twigs and stomatal conductance (g(s)) were measured simultaneously as leaf water potential declined. For all species, lower vulnerability to embolism based on loss of Ks was recorded on current-year twigs. The threshold for stomatal closure (10% of maximum g(s)) was reached at a predawn water potential (Psi(pd)) of -2.5 MPa in C. atlantica (Luberon) and at -3.1 MPa in C. libani (Lebanon), whereas the other provenance and species had intermediate Psi(pd) values. Cedrus brevifolia, with a Psi(pd) (-3.0 MPa) close to that of C. libani (Lebanon), had the highest stomatal conductance of the study species. The importance of a margin of safety between water potential causing stomatal closure and that causing xylem embolism induction is discussed.

Cedrus↗
PubMed2006

Scaling of angiosperm xylem structure with safety and efficiency.

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 that cavitation pressure was not related to mean pit membrane porosity.

Biological Transport↗
PubMed2007

Variability with xylem depth in sap flow in trunks and branches of mature olive trees.

Knowledge of sap flow variability in tree trunks is important for up-scaling transpiration from the measuring point to the whole-tree and stand levels. Natural variability in sap flow, both radial and circumferential, was studied in the trunks and branches of mature olive trees (Olea europea L., cv Coratina) by the heat field deformation method using multi-point sensors. Sapwood depth ranged from 22 to 55 mm with greater variability in trunks than in branches. Two asymmetric types of sap flow radial patterns were observed: Type 1, rising to a maximum near the mid-point of the sapwood; and Type 2, falling continuously from a maximum just below cambium to zero at the inner boundary of the sapwood. The Type 1 pattern was recorded more often in branches and smaller trees. Both types of sap flow radial patterns were observed in trunks of the sample trees. Sap flow radial patterns were rather stable during the day, but varied with soil water changes. A decrease in sap flow in the outermost xylem was related to water depletion in the topsoil. We hypothesized that the variations in sap flow radial pattern in a tree trunk reflects a vertical distribution of water uptake that varies with water availability in different soil layers.

Circadian Rhythm↗
PubMed2001

Theoretical analysis of systematic errors introduced by a pedicel-girdling technique used to estimate separately the xylem and phloem flows.

The water budget of fruits was analysed by means of a biophysical model of fruit growth, built and calibrated recently for peaches [Prunus persica (L.) Batsch]. This analysis was applied to the evaluation of systematic errors introduced by a pedicel-girdling method (with the observations being treated by means of a subtractive technique) used to separate the contributions of xylem and phloem flow to the total water inflow to the fruit. The flows were considered as solution transport through composite membranes and were calculated by means of equations drawn from non-equilibrium thermodynamics. The total inflow of water was simulated as dependent on the water status in the tree. The hourly time step was used for the simulation. The flows obtained by simulation of the pedicel-girdled fruit were compared with those found by simulation of the intact-pedicel fruit. The error introduced by the pedicel-girdling technique was evaluated theoretically and was shown to vary during the day, ranging from very small (relative error of 3-7%) at the period when the rate of fruit growth is maximal to 100% when the fruit volume does not change. The vascular flows obtained from the "girdling experiments" are discussed in relation to the possible theoretically estimated errors.

Biological Transport↗
PubMed1991

Seasonal changes in the concentration of the major storage protein and its mRNA in xylem ray cells of poplar trees.

In the autumn large amounts of a major storage protein accumulate in the woody stem of poplar trees. This protein is stored in xylem ray cells during the winter season and is degraded in late spring. The accumulation of this protein is preceded by a dramatic but transient appearance of the corresponding mRNA. Thus, the seasonal change in the mRNA content appears to be a crucial event for the storage of nitrogen in the stem. The amino acid sequence of the storage protein has been deduced from the nucleotide sequence of a full-length cDNA. The cDNA shows a nucleotide sequence similarity of approximately 75% with two published cDNA sequences of poplar which represent transcripts that accumulate systemically in leaves of poplar trees in response to wounding.

Amino Acid Sequence↗
PubMed2004

Indirect immunofluorescence microscopy for direct detection of Xylella fastidiosa in xylem sap.

The plant pathogen Xylella fastidiosa is the causative agent of a number of diseases of economically important crops, including Pierce's disease that affects grapevines. Using a commercially available antibody specific for X. fastidiosa, we have established a protocol for microscopic identification of the bacterium by indirect immunofluorescence. This antibody clearly labels an uncharacterized antigen concentrated at a single pole of X. fastidiosa cells, but does not react with a non- Xylella control. This technique was also performed successfully on xylem exudates from several different plant genera and correlated well with standard enzyme-linked immunosorbent assay tests. These results establish a novel method for in situ assessment of X. fastidiosa infection from host plants.

Asteraceae↗
PubMed2005

A fasciclin-domain containing gene, ZeFLA11, is expressed exclusively in xylem elements that have reticulate wall thickenings in the stem vascular system of Zinnia elegans cv Envy.

The vascular cylinder of the mature stem of Zinnia elegans cv Envy contains two anatomically distinct sets of vascular bundles, stem bundles and leaf-trace bundles. We isolated a full-length cDNA of ZeFLA11, a fasciclin-domain-containing gene, from a zinnia cDNA library derived from in vitro cultures of mesophyll cells induced to form tracheary elements. Using RNA in situ hybridization, we show that ZeFLA11 is expressed in the differentiating xylem vessels with reticulate type wall thickenings and adjacent parenchyma cells of zinnia stem bundles, but not in the leaf-trace bundles that deposit spiral thickenings. Our results suggest a function for this cell-surface GPI-anchored glycoprotein in secondary wall deposition during differentiation of metaxylem tissue with reticulate vessels.

Amino Acid Sequence↗
PubMed2005

Zinc compartmentation in root, transport into xylem, and absorption into leaf cells in the hyperaccumulating species of Sedum alfredii Hance.

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.

Amino Acids↗
PubMed1994

Purification of an acidic coniferin-hydrolysing beta-glucosidase from developing xylem of Pinus banksiana.

Two cytosolic, acidic (pI 3.8) glycoproteins (M(r) 110,000 and 90,000) from lignifying xylem of Pinus banksiana were electrophoretically isolated and confirmed by combined gas chromatography-mass spectrometry to be capable of hydrolysing E-coniferin to trans-coniferyl alcohol. These isoenzymes yielded identical N-terminal sequences having negligible homology with documented glucosidases, suggesting that they constitute a novel form of beta-glucosidase.

Amino Acid Sequence↗
PubMedDate not supplied

The regulation from guaiacyl to syringyl lignin in the differentiating xylem of Robinia pseudoacacia.

13C- and deuterium (D)-labeled ferulic acid and sinapic acid ([8-(13)C, 3-OCD3]-ferulic acid and [8-(13)C, 3,5-OCD3]-sinapic acid) were administered to robinia (Robinia pseudoacacia L.) shoots. To estimate the distribution of the label from administrated ferulic or sinapic acid, continuous 50-microm-thick tangential sections cut from the cambium of robinia were subjected to lignin chemical analysis by the DFRC method. Labeled ferulic acid was incorporated into guaiacyl and syringyl lignin. The incorporation of labeled ferulic acid into syringyl units was observed only in the later stage of lignification. Labeled sinapic acid was incorporated into syringyl lignin in the early stage and the later stage of lignification. In general, syringyl lignin was deposited in the later stage of cell wall lignification. Thus, the incorporation of sinapic acid to syringyl lignin in the early stage of lignification was abnormal. Taken together, the aromatic ring-modifying reactions (the conversion from guaiacyl to syringyl moiety, including the hydroxylation and methylation) were more important for the regulation of the sinapyl alcohol biosynthesis than the reducing reactions (the reduction of acids to alcohols) in the differentiating xylem.

Lignin↗
PubMedDate not supplied

Formation of macromolecular lignin in ginkgo xylem cell walls as observed by field emission scanning electron microscopy.

Formation of macromolecular lignin in ginkgo cell walls. In the lignifying process of xylem cell walls, macromolecular lignin is formed by polymerization of monolignols on the pectic substances, hemicellulose and cellulose microfibrils that have deposited prior to the start of lignification. Observation of lignifying secondary cell walls of ginkgo tracheids by field emission scanning electron microscopy suggested that lignin-hemicellulose complexes are formed as tubular bead-like modules surrounding the cellulose microfibrils (CMFs), and that the complexes finally fill up the space between CMFs. The size of one tubular bead-like module in the middle layer of the secondary wall (S2) was tentatively estimated to be about 16+/-2 nm in length, about 25+/-1 nm in outer diameter, with a wall thickness of 4+/-2 nm; the size of the modules in the outer layer of the secondary wall (S1) was larger and they were thicker-walled than that in the middle layer (S2). Aggregates of large globular modules were observed in the cell corner and compound middle lamella. It was suggested that the structure of non-cellulosic polysaccharides and mode of their association with CMFs may be important factors controlling the module formation and lignin concentration in the different morphological regions of the cell wall.

Cell Wall↗
PubMed2004

Molecular basis for the evolution of xylem lignification.

The lignification of xylem is an adaptive trait of great significance. Gymnosperms and angiosperms share an ancient, conserved set of enzymes that are regulated by a conserved transcription factor and that are responsible for the formation of guaiacyl lignin. Angiosperms have evolved at least two enzymes that catalyze the production of syringyl lignin. Association genetics is now being used to explore the adaptive significance of sequence variation in the genes that encode these monolignol biosynthetic enzymes.

Cycadopsida↗
PubMed1986

Identification of a new, naturally occurring, non proteic amino acid in xylem sap of Pisum sativum.

The xylem sap of nitrogen-fixing Pisum Sativum cv Homesteader has been examined by capillary gas chromatography and by gas chromatography mass spectrometry in both electron-impact and chemical ionization modes following the formation of N-heptafluorobutyryl isobutyl ester derivatives. One of the compounds thus detected had a mass of 389 and contained chlorine, one carboxylic acid group and a nitrogen atom. High-resolution mass spectrometry indicated that there were no other hetero atoms present in the molecule. The composition was determined to be C4H8NO2Cl. This composition can be explained only in terms of a chloroamino butyric acid.

Amino Acids↗
PubMed1997

Rhamnogalacturonan I from xylem differentiating zones of Cryptomeria japonica.

Rhamnogalacturonan I (RG-I) was isolated from the pectin of the cell wall of xylem differentiating zones of sugi (Cryptomeria japonica D. Don, gymnosperm) by digesting with endo-alpha-1,4-polygalacturonase followed by gel-permeation chromatography. Structure of RG-I was characterized by glycosyl composition and glycosyl linkage analyses, partial acid hydrolysis, and lithium (Li)-treatment in ethylenediamine. The oligosaccharides produced by partial acid hydrolysis showed the backbone of RG-I to be a disaccharide repeating unit of --> 4)-alpha-D-GalpA-(1-->2)-alpha-L-Rhap-(1-->. Arabian and oligogalactosyl side chains were attached at O-4 of rhamnosyl residues of the backbone. Glycosyl composition and glycosyl linkage analyses suggested that the structures and/or the distribution of the arabinan sidechains of sugi RG-I were different from those of sycamore (angiosperm) RG-I.

Carbohydrate Conformation↗
PubMed2003

A tomato xylem sap protein represents a new family of small cysteine-rich proteins with structural similarity to lipid transfer proteins.

The coding sequence of a major xylem sap protein of tomato was identified with the aid of mass spectrometry. The protein, XSP10, represents a novel family of extracellular plant proteins with structural similarity to plant lipid transfer proteins. The XSP10 gene is constitutively expressed in roots and lower stems. The decline of XSP10 protein levels in tomato infected with a fungal vascular pathogen may reflect breakdown or modification by the pathogen.

Amino Acid Sequence↗