Ultrastructural observations on pit membrane alterations and associated effects in elm xylem tissues infected by Ceratocystis ulmi

1978 ◽  
Vol 56 (20) ◽  
pp. 2567-2588 ◽  
Author(s):  
G. B. Ouellette
Keyword(s):  
Protective Layer ◽  
Cavity Formation ◽  
Bordered Pit ◽  
Fibrillar Material ◽  
Host Cytoplasm ◽  
Pit Membrane ◽  
Bordered Pits ◽  
Parenchyma Cells

Gradations in the degree of pit membrane alteration in tissues infected by Ceratocystis ulmi (Buism.) C. Moreau and collected at various intervals after inoculation are described. Membranes of bordered pit pairs are coated and apparently impregnated with bands or masses of osmiophilic material; this coating may be thick and stratified and the pit cavities completely occluded. Similar osmiophilic material also occurs in decreasing amounts over and within membranes of simple or half-bordered pits and within the adjacent protective layer. Various degrees of distention and cavity formation in these pit membranes are associated with the osmiophilic material. Products released into vessels from disintegrating pit membranes seem to be sparse. Host cytoplasm in contiguous parenchyma cells can have diverse reactions.Examination of specimens at various angles established the interrelationship between osmiophilic material and remnants of pit membranes. Variously oriented lamellar-like structures and a fibrillar material intermixed with a more amorphous one characterize the osmiophilic material. The significance of these observations is discussed.

Torus Structure and Development in Species of Daphne

IAWA Journal ◽  
1990 ◽  
Vol 11 (4) ◽  
pp. 401-412 ◽  
Author(s):  
Roland R. Dute ◽  
Ann E. Rushing ◽  
James W. Perry
Keyword(s):  
Tracheary Element ◽  
Tracheary Elements ◽  
Bordered Pit ◽  
Fibrillar Material ◽  
Pit Membrane ◽  
Parenchyma Cells ◽  
Daphne Odora

A torus is present in intervascular pit membranes in the wood of Daphne odora and D. cneorum, but not in D. mezereum. In the two former species, each torus is surrounded by a margo consisting of fibrillar material in a tightly woven pattern. Tori are of greater diameter than pit apertures and completely occlude the apertures during aspiration. Evidence from D. odora indicates that torus deposition is spatially associated with vesicles and a plexus of microtubules, and does not begin until pit border formation is complete. The material deposited during torus synthesis also impregnates the wall of the pre-existing pit membrane. The plasmalemma often is closely appressed to the pit membrane at the site of the developing torus. In half-bordered pit pairs between tracheary elements and parenchyma cells, a torus thickening is deposited only on the side of the tracheary element. As in Osmanthus americanus, it is hypothesised that the presence of tori in species of Daphne prevents rupture of the pit membrane during aspiration.

The Protective Layer as an Extension of the Apoplast

IAWA Journal ◽  
1993 ◽  
Vol 14 (2) ◽  
pp. 163-171 ◽  
Author(s):  
J. R. Barnett ◽  
P. Cooper ◽  
Lynda J. Bonner
Keyword(s):  
Cell Wall ◽  
Protective Layer ◽  
Xylem Parenchyma ◽  
Pit Membrane ◽  
Parenchyma Cells ◽  
Deep Supercooling ◽  
Dying Cells ◽  
Tylose Formation ◽  
Universal Application

The protective layer between the cell wall and plasmalemma of xylem parenchyma cells has variously been suggested to be involved in protection of the protoplast from attack by autolytic enzymes from neighbouring, dying cells, tylose formation, deep supercooling of xylem, and strengthening of the pit. None of these ideas has universal application to all species in which parenchyma cells possess a protective layer. It is proposed instead, that the protective layer is primarily laid down in order to preserve apoplastic continuity around the protoplast of a lignified cell, bringing the entire plasmalemma surface, and not just that part of it in contact with the porous pit membrane, into contact with the apoplast. If this is so, then other functions may be coincidental, or have arisen secondarily.

Torus-Bearing Pit Membranes in Cercocarpus

IAWA Journal ◽  
2010 ◽  
Vol 31 (1) ◽  
pp. 53-66 ◽  
Author(s):  
Roland Dute ◽  
Jaynesh Patel ◽  
Steven Jansen
Keyword(s):  
Secondary Wall ◽  
Membrane Surface ◽  
Parenchyma Cell ◽  
Protective Layer ◽  
Wall Material ◽  
Tracheary Elements ◽  
Bordered Pit ◽  
Parenchyma Cells ◽  
Conducting Cell ◽  
Cell Ontogeny

Intervascular pit membranes of Cercocarpus possess torus thickenings. The thickenings, or pads, consist of lignified, secondary wall material. Torus pad deposition occurs late in cell ontogeny and is not associated with a microtubule plexus. Half-bordered pit pairs between tracheary elements and parenchyma cells often have a torus pad on the membrane surface facing the conducting cell. In contrast, a thick protective layer fills the pit cavity on the side of the parenchyma cell. Ontogeny of the torus thickenings in Cercocarpus represents a third mode of torus development in eudicots when compared to that occurring in Osmanthus/Daphne and Ulmus/Celtis.

An “Ultrafilter” in the Margo of Mature Bordered Pits?

1972 ◽  
Vol 30 ◽  
pp. 206-207
Author(s):  
I. B. Sachs ◽  
R. E. Kinney
Keyword(s):  
Surface Tension ◽  
Electron Microscope ◽  
Molecular Sieve ◽  
Pinus Strobus ◽  
Postmortem Changes ◽  
Sodium Chlorite ◽  
Bordered Pit ◽  
Pit Membrane ◽  
Bordered Pits ◽  
Surface Tension Forces

The micrographs illustrating this paper were obtained from never-dried springwood bordered pit-pairs of Pinus strobus L. Specimens were treated with acidified sodium chlorite in order to remove incrusting materials from the pit membrane. To prevent or reduce interfacial and surface tension forces and provide a view of bordered pit structure without postmortem changes, the specimens were further treated either by the critical point method of Weatherwax and Caulfield, a version of Anderson's method, or by a low temperature evaporation method using molecular sieve material at -40° C. to gently remove the alcohol, Arenberg, et al. For studying the pit membrane of bordered pit-pairs, neither technique seems to have an advantage, giving similar results.Light and electron microscope studies have established that structurally the bordered pit-pair membrane consists of a torus and a margo.

scholarly journals Immunocytochemical Evidence that Secretion of Pectin Occurs During Gel (Gum) and Tylosis Formation in Trees

1998 ◽  
Vol 88 (6) ◽  
pp. 494-505 ◽  
Author(s):  
D. Rioux ◽  
M. Nicole ◽  
M. Simard ◽  
G. B. Ouellette
Keyword(s):  
Protective Layer ◽  
Xylem Parenchyma ◽  
Pectic Polysaccharides ◽  
Future Studies ◽  
Protective Layers ◽  
Fibrillar Material ◽  
Causative Factors ◽  
Vessel Elements ◽  
Parenchyma Cells ◽  
Other Substances

During gel (gum) formation in angiosperm trees, fibrillar material accumulated in protective layers of xylem parenchyma cells before being secreted across half-bordered pit membranes into vessel elements. Immunogold labeling demonstrated that this fibrillar material was mainly composed of partially esterified pectic polysaccharides. The primary wall of expanding tyloses, an extension of the parenchyma protective layer, secreted similar pectic substances to completely block vessel elements. In most studies, these occluding structures were reported to be formed in response to causative factors such as aging processes, injuries, or infections. Current observations support the view that partial to complete embolism, which almost always accompanies these factors, might be the main cause triggering the formation of vessel occlusions. Whereas pectin seems to be the basic component of gels (gums) and of the external layer of tyloses, other substances, such as phenols, were also detected either as a part of these plugs or as accumulations beside them in vessels. Finally, it is proposed that the term ‘gel’ instead of ‘gum’ be used in future studies to describe the occluding material secreted by ray and paratracheal parenchyma cells.

Intercellular pathways in internodal metaxylem vessels of moso bamboo Phyllostachys edulis

IAWA Journal ◽  
2019 ◽  
Vol 40 (4) ◽  
pp. 871-883 ◽  
Author(s):  
Shuqin Zhang ◽  
Rong Liu ◽  
Caiping Lian ◽  
Junji Luo ◽  
Feng Yang ◽  
...  
Keyword(s):  
Xylem Sap ◽  
Environmental Scanning Electron Microscopy ◽  
Moso Bamboo ◽  
Size Difference ◽  
Adjacent Cell ◽  
Bordered Pit ◽  
Essential Components ◽  
Bordered Pits ◽  
Vessel Elements ◽  
Parenchyma Cells

ABSTRACT The flow of xylem sap in bamboo is closely associated with metaxylem vessels and the pits in their cell walls. These pits are essential components of the water-transport system and are key intercellular pathways for transverse permeation of treatment agents related to utilization. Observations of metaxylem vessels and pits in moso bamboo culm internodes were carried out using environmental scanning electron microscopy (ESEM) to examine mature bamboo fractures and resin casts. The results showed that bordered pits were distributed in relation to adjacent cell types with most pits between vessels and parenchyma cells and few pits between vessels and fibers of the bundle sheath. The pit arrangement was mainly opposite to alternate with apertures ranging from oval, flattened elliptical, or slit-like to coalescent. The vertical dimensions of inner apertures and outer apertures of the pits were about 0.9–2.7 μm and 1.1–3.8 μm, respectively. According to the relative position, and size difference between the inner apertures and their borders, the bordered pit shapes were categorized into three types, namely PI, PII and PIII (Fig. 3C). Half-bordered pit pairs were observed between vessels and direct contact parenchyma cells. Most vessel elements possessed simple perforation plates.

Wound Reaction of the Parenchyma in Betula

IAWA Journal ◽  
1990 ◽  
Vol 11 (4) ◽  
pp. 413-420 ◽  
Author(s):  
Uwe Schmitt ◽  
Walter Liese
Keyword(s):  
Betula Pendula ◽  
Structural Changes ◽  
Light And Electron Microscopy ◽  
Protective Layer ◽  
Xylem Parenchyma ◽  
Fibrillar Material ◽  
Pit Membrane ◽  
Wound Reaction ◽  
Simultaneous Loss ◽  
Perforation Plates

Reactions in the xylem parenchyma of Betula pendula Roth following wounding in late spring have been investigated by light and electron microscopy. Structural changes in contact parenchyma cells are described in relation to the formation of plugs in vessels and fibres. Swelling of the Protective Layer (PL) with a simultaneous loss in electron density appears first. Fibrillar material is then synthesised, which accumulates outside the cytoplasm between the plasmalemma and the modified PL. The PL now consists of loosely packed fibrils with a structure similar to the accumulating fibrillar material. After extrusion of fibrils through the pit membrane into the lumina of adjacent vessels a membranous layer on the scalariform perforation plates as well as plugs are formed; the latter are also built up in fibres. These reactions spread axially less extensively in cells near the cambium than in the more centrally located ones.

scholarly journals Bacterial Biodegradation of Extractives and Patterns of Bordered Pit Membrane Attack in Pine Wood

2000 ◽  
Vol 66 (12) ◽  
pp. 5201-5205 ◽  
Author(s):  
Todd A. Burnes ◽  
Robert A. Blanchette ◽  
Roberta L. Farrell
Keyword(s):  
Xanthomonas Campestris ◽  
Treated Wood ◽  
Wood Chips ◽  
Pulp Mills ◽  
Wood Extractives ◽  
Bordered Pit ◽  
Pine Wood ◽  
Pit Membrane ◽  
Pine Wood Chips ◽  
Ray Parenchyma Cells

ABSTRACT Wood extractives, commonly referred to as pitch, cause major problems in the manufacturing of pulp and paper. Treatment of nonsterile southern yellow pine chips for 14 days withPseudomonas fluorescens, Pseudomonas sp.,Xanthomonas campestris, and Serratia marcescens reduced wood extractives by as much as 40%. Control treatments receiving only water lost 11% of extractives due to the growth of naturally occurring microorganisms. Control treatments were visually discolored after the 14-day incubation, whereas bacterium-treated wood chips were free of dark staining. Investigations using P. fluorescens NRRL B21432 showed that all individual resin and fatty acid components of the pine wood extractives were substantially reduced. Micromorphological observations showed that bacteria were able to colonize resin canals, ray parenchyma cells, and tracheids. Tracheid pit membranes within bordered pit chambers were degraded after treatment with P. fluorescensNRRL B21432. P. fluorescens and the other bacteria tested appear to have the potential for biological processing to substantially reduce wood extractives in pine wood chips prior to the paper making process so that problems associated with pitch in pulp mills can be controlled.

Function and three-dimensional structure of intervessel pit membranes in angiosperms: a review

IAWA Journal ◽  
2019 ◽  
Vol 40 (4) ◽  
pp. 673-702 ◽  
Author(s):  
Lucian Kaack ◽  
Clemens M. Altaner ◽  
Cora Carmesin ◽  
Ana Diaz ◽  
Mirko Holler ◽  
...  
Keyword(s):  
Water Transport ◽  
Three Dimensional ◽  
Cellulose Microfibrils ◽  
Dimensional Structure ◽  
High Porosity ◽  
Dynamic Surface ◽  
Three Dimensional Structure ◽  
Pit Membrane ◽  
Bordered Pits ◽  
20 Nm

ABSTRACTPit membranes in bordered pits of tracheary elements of angiosperm xylem represent primary cell walls that undergo structural and chemical modifications, not only during cell death but also during and after their role as safety valves for water transport between conduits. Cellulose microfibrils, which are typically grouped in aggregates with a diameter between 20 to 30 nm, make up their main component. While it is clear that pectins and hemicellulose are removed from immature pit membranes during hydrolysis, recent observations of amphiphilic lipids and proteins associated with pit membranes raise important questions about drought-induced embolism formation and spread via air-seeding from gas-filled conduits. Indeed, mechanisms behind air-seeding remain poorly understood, which is due in part to little attention paid to the three-dimensional structure of pit membranes in earlier studies. Based on perfusion experiments and modelling, pore constrictions in fibrous pit membranes are estimated to be well below 50 nm, and typically smaller than 20 nm. Together with the low dynamic surface tensions of amphiphilic lipids at air-water interfaces in pit membranes, 5 to 20 nm pore constrictions are in line with the observed xylem water potentials values that generally induce spread of embolism. Moreover, pit membranes appear to show ideal porous medium properties for sap flow to promote hydraulic efficiency and safety due to their very high porosity (pore volume fraction), with highly interconnected, non-tortuous pore pathways, and the occurrence of multiple pore constrictions within a single pore. This three-dimensional view of pit membranes as mesoporous media may explain the relationship between pit membrane thickness and embolism resistance, but is largely incompatible with earlier, two-dimensional views on air-seeding. It is hypothesised that pit membranes enable water transport under negative pressure by producing stable, surfactant coated nanobubbles while preventing the entry of large bubbles that would cause embolism.

The fine structure of the pits of Eucalyptus regnans (F. Muell.) and their relation to the movement of liquids into the wood

1960 ◽  
Vol 8 (1) ◽  
pp. 51 ◽  
Author(s):  
J Cronshaw
Keyword(s):  
Secondary Wall ◽  
Structural Features ◽  
Cellulose Microfibrils ◽  
Primary Wall ◽  
Detailed Structure ◽  
Eucalyptus Regnans ◽  
Pit Membrane ◽  
Parenchyma Cells ◽  
Ray Parenchyma ◽  
Ray Parenchyma Cells

Observstion in the electron microscope of carbon replicas of the pits of vessels, ray parenchyma cells, fibres, and tracheids of Eucalyptus regnans has shown the detailed structure of the pit borders and the pit closing membranes. In all cases in the mature wood the primary wall is left apparently without modification as the pit membrane. Unlike the borders of the pits of fibre tracheids and tracheids, the pit borders of the vessels are not separate; the cellulose microfibrils of a border may be common to several pits. The pit borders of fibre traoheids and tracheids are developed as separate entities and have a structure similar to the pit borders of softwood tracheids. The structure of the secondary wall layers associated with the pits is described and related to the structure of the pits. The fine structural features of the pits, especially of the pit closing membranes, are discussed in relation to the movement of liquids into wood.

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