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.

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.

Pit Pairs With Tori in the Wood of Osmanthus Americanus (Oleaceae)

IAWA Journal ◽  
1987 ◽  
Vol 8 (3) ◽  
pp. 237-244 ◽  
Author(s):  
Roland R. Dute ◽  
Ann E. Rushing
Keyword(s):  
Middle Lamella ◽  
Radial Component ◽  
Wall Material ◽  
Sodium Chlorite ◽  
Variable Amount ◽  
Tracheary Elements ◽  
Bordered Pit ◽  
Compound Middle Lamella ◽  
Pit Membrane

Bordered pit pairs connecting tracheary elements in the wood of Osmanthus americanus (L.) Benth. ' Hook. ex Gray contained a torus in the pit membrane. This structure is approximately 2.5 μm in diameter, and is located at or near the centre of the pit membrane. The encrusting material of the torus could be removed by treatment with sodium chlorite. Thin seetions through theJorus showed it to consist of a pad of wall material appressed to either side of the compound middle lamella. The membrane surrounding the torus (the margo) consisted of fibrils and a variable amount of enc10sing matrix. The fibrils were generally c1oseIy packed and randomly oriented, although occasionally a radial component was also present. Aspiration of the pit membrane in air-dried material caused the torus to seal off one of the pit apertures. During this process the torus probably prevented rupture of the pit membrane at that site.

scholarly journals The aspiration of bordered pits in conifer wood

1972 ◽  
Vol 181 (1065) ◽  
pp. 395-406 ◽  
Keyword(s):  
Surface Tension ◽  
Hydrogen Bonding ◽  
Pinus Sylvestris ◽  
Growth Ring ◽  
Surface Tension Force ◽  
The Other ◽  
Liquid Meniscus ◽  
Pit Membrane ◽  
Bordered Pits ◽  
Conifer Wood

The variation of tension in a radial strand of a bordered pit membrane during drying has been derived theoretically from two approaches. One considers the mechanical extension of the strand, while the other considers the surface tension force caused by an annular liquid meniscus in the pit chamber. The tension has been calculated for pits in earlywood, in latewood and in regions near the earlywood-latewood boundary of a single growth ring in Pinus sylvestris L., using experimentally observed typical values for pit dimensions. The occurrence of aspiration of earlywood but not of latewood pits in air-seasoned wood is correctly predicted by the analysis, which also predicts that, contrary to accepted theory, earlywood pit membranes should be displaced and brought into contact with the pit border irrespective of the liquid present during drying. It is shown that this must involve considerable creep in the radial strands. Permanent aspiration must only occur when the liquid promotes bonding between the membrane and the border, and the probability that this is hydrogen bonding is discussed.

INFLUENCE OF SURFACE TENSION FORCES ON FILMWISE CONDENSATION INTENSITY

2016 ◽  
Vol 7 (1-2) ◽  
pp. 93-102
Author(s):  
Vasily Buz ◽  
Konstantin Goncharov ◽  
Henry F. Smirnov
Keyword(s):  
Surface Tension ◽  
Surface Tension Forces

On the defects of enamel coatings

2019 ◽  
pp. 145-150
Author(s):  
T. O. Soshina ◽  
V. R. Mukhamadyarovа
Keyword(s):  
Heat Treatment ◽  
Surface Tension ◽  
Electron Microscope ◽  
Enamel Coating ◽  
Surface Defects ◽  
Linear Expansion ◽  
Corrosion Properties ◽  
Treatment Conditions ◽  
Mechanical And Corrosion Properties ◽  
Coefficient Of Linear Expansion

The defects destroy the integrity of the enamel, and the paper examines the influence of the physical-mechanical and corrosion properties of frits and heat treatment on the defectiveness of the enamel coating. The surface defects were scanned by electron microscope. It has been established that the defectiveness of enamel coatings depends on the melting index, temperature coefficient of linear expansion, surface tension of the frits, and heat treatment conditions. When burning rate of the enamel coating decreases, the fine-meshed structure of the enamel changes, and the size of the defects decreases.

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.

Effects of surface tension and viscosity on airway reopening

1990 ◽  
Vol 69 (1) ◽  
pp. 74-85 ◽  
Author(s):  
D. P. Gaver ◽  
R. W. Samsel ◽  
J. Solway
Keyword(s):  
Surface Tension ◽  
Fluid Viscosity ◽  
Opening Pressure ◽  
Viscous Forces ◽  
Considerable Portion ◽  
Airway Opening ◽  
Wall Compliance ◽  
Large Opening ◽  
Surface Tension Forces ◽  
The Relationship

We studied airway opening in a benchtop model intended to mimic bronchial walls held in apposition by airway lining fluid. We measured the relationship between the airway opening velocity (U) and the applied airway opening pressure in thin-walled polyethylene tubes of different radii (R) using lining fluids of different surface tensions (gamma) and viscosities (mu). Axial wall tension (T) was applied to modify the apparent wall compliance characteristics, and the lining film thickness (H) was varied. Increasing mu or gamma or decreasing R or T led to an increase in the airway opening pressures. The effect of H depended on T: when T was small, opening pressures increased slightly as H was decreased; when T was large, opening pressure was independent of H. Using dimensional analysis, we found that the relative importance of viscous and surface tension forces depends on the capillary number (Ca = microU/gamma). When Ca is small, the opening pressure is approximately 8 gamma/R and acts as an apparent “yield pressure” that must be exceeded before airway opening can begin. When Ca is large (Ca greater than 0.5), viscous forces add appreciably to the overall opening pressures. Based on these results, predictions of airway opening times suggest that airway closure can persist through a considerable portion of inspiration when lining fluid viscosity or surface tension are elevated.

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.

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