Double Cell Wall Research Articles

Deformation of the compound middle lamella in spruce latewood by micro-pillar compression of double cell walls

The mechanical integrity of the interface between two adjacent cells in spruce late wood was studied by uniaxial compression of focused ion beam machined micro-pillars of double cell walls (DCW) containing the compound middle lamella (CML). The DCW reveals a lower yield strength and stiffness than the secondary cell wall (S2). Failure occurs by tearing of the interface between the first (S1) and second layers (S2) of the secondary cell wall exposing the internal arrangement of the microfibrils, while the CML remains intact.

Understanding trait interactions and their impacts on growth in Scots pine branches across Europe

Summary1. Plants exhibit a wide variety in traits at different organizational levels. Intraspecific and interspecific studies have potential to demonstrate functional relationships and trade‐offs amongst traits, with potential consequences for growth. However, the distinction between the correlative and functional nature of trait covariation presents a challenge because traits interact in complex ways.2. We present an intraspecific study on Scots pine branches and use functional multi‐trait concepts to organize and understand trait interactions and their impacts on growth. Branch‐level traits were assessed for 97 branches from 12 Scots pine sites across Europe.3. To test alternative hypotheses on cause–effect relationships between anatomical traits, hydraulic traits and branch growth, we measured for each branch: the tracheid hydraulic diameter, double cell wall thickness, cell lumen span area, wood density, cavitation vulnerability, wood‐specific hydraulic conductivity, the leaf area to sapwood area ratio and branch growth. We used mixed linear effect models and path models to show how anatomical traits determine hydraulic traits and, in turn, how those traits influence growth.4. Tracheid hydraulic diameter was the best predictor of cavitation vulnerability (R2 = 0·09 explained by path model) and specific conductivity (R2 = 0·19) amongst anatomical traits. Leaf area to sapwood area ratio had the strongest direct effect on branch growth (R2 = 0·19) and was positively associated with the tracheid hydraulic diameter (R2 = 0·22). A number of bivariate correlations between traits could be explained by these functional relationships amongst traits.5. The plasticity in tracheid hydraulic diameter (10.0–15.1 μm) and leaf area to sapwood area ratio (600–6051 cm2 cm−2) and the maintenance of a minimum leaf water potential (between −2 and −2·5 MPa) appear to drive the anatomical and hydraulic traits of Scots pine across Europe. These properties are major drivers of the functional trait network underlying the growth variation amongst pine branches and thus possibly contribute to the ecological success of pines at a local and continental scale.

Out-of-Plane Quasi-Static Compression of Aluminum Hexagonal Honeycomb Cores - a Finite Element Analysis

A finite element (FE) model of hexagonal honeycomb cores (HHCs) with single or double cell walls is framed based on the honeycomb cell array, to reproduce the compressive behavior under the quasi-static out-of-plane compression. The FE calculated deformation modes, deformation curves and values of quasi-static plateau stresses are presented in the forms of diagrams, compressive force-displacement curves and data tables, which are consistent with the existing experimental and theoretical calculated results. It is shown that the proposed FE analysis methodology is reliable.

Empirical models for radial and tangential fibre width in tree rings of Norway spruce in north-western Europe

Abstract Tracheid dimensions influence the quality of wood and that of pulp and paper. Both between- and within-ring variations are influenced by tree developmental stage, site, genetics, and forest management. To contribute to the knowledge in this regard, the radial and tangential tracheid dimensions on Norway spruce, defined as the lumens and double cell wall thickness, have been measured using a SilviScan device. Namely, 4947 annual rings from 35 trees from plantations in France, Norway, and Sweden were examined. Mixed-effects models were constructed concerning the radial and tangential tracheid widths for the total ring and in three within-ring compartments – earlywood (EW), transition wood (TW), and latewood (LW) – as functions of age, radius, height in the tree, and growth rate. Between-site and between-tree variations were also considered. The mean radial tracheid width was 34.2 μm (EW), 29.9 μm (TrW), and 22.1 μm (LW). The tangential tracheid width was on average 30.1 μm in all compartments. The radial and tangential tracheid widths in the rings and compartments increased from the pith to the bark and decreased with greater growth rates. Within a given ring, both properties decreased with height in the tree. The fixed part of the models of the radial tracheid width accounted for 68% (EW), 45% (TW), and 33% (LW) while for the models of the tangential fibre width it accounted for 42% of the variation in all compartments. Climate or hydraulic maintenance was hypothesised to be responsible for the variation of the radial tracheid width.

ENERGY ABSORPTION EFFICIENCY IN CELLULAR SOLIDS

In this paper, a new type of honeycomb structure is proposed to enhance the energy absorption capacity for a honeycomb structure, and investigated its energy absorption efficiency (absorbed energy per unit volume) by finite element method (FEM). This model has small arc-shaped parts on the double cell wall, and can be manufactured by a similar way of standard honeycomb structures. Also, the proposed structure has large rigidity of plastic bending without increasing the mass. In this paper, effects of geometrical properties on the energy absorption characteristics are discussed.

X-ray microdiffraction reveals the orientation of cellulose microfibrils and the size of cellulose crystallites in single Norway spruce tracheids

The microfibril angle (MFA) distribution and the size of cellulose crystallites in isolated double cell walls of Norway spruce (Picea abies [L.] Karst.) tracheids were determined by synchrotron X-ray microdiffraction using the reflections 200 and 004. Samples were 25 μm thick longitudinal sections of earlywood from annual rings 6–18 of several stems. The asymmetric MFA distributions extended from −20° to 90°. The mean MFA of tangential cell walls decreased from an average of 24° into 19° from the pith to the bark. The mode of the MFA distribution was about 10° smaller than the mean MFA. The standard deviation of the MFA distribution varied between 18° and 25°. The mean MFA and the mode of the MFA distribution were larger in radial than in tangential cell walls. MFA distributions of mature wood samples exhibited a separate small peak at around 90°. The average width and length of cellulose crystallites varied between 28.9–30.9 A and 192–284 A, respectively. Both increased slightly as a function of annual ring number from the pith up to the 15th annual ring. An irrigation–fertilisation treatment of some of the stems resulted in longer cellulose crystallites compared to the untreated stems.

Measuring resistant forms of two pathogenic protozoa (Giardia spp and Cryptosporidium spp) in two aquatic biotopes in Yaoundé (Cameroon)

Organisms of the genera Cryptosporidium and Giardia are enteric parasites that are responsible for cryptosporidiosis and giardiasis respectively. They are characterised by profuse diarrhoea, abdominal pain and cramping. The symptoms can be fatal for immunodepressed subjects and children because these are opportunistic pathogens. These pathogenic infections are rampant in developing countries due to the unhygienic and improper disposal of wastewater and the use of surface water as the major sources of potable water. Little information is available about the resistant forms of these microorganisms in the hydrosystems of Cameroon in particular and other sub-Saharan ecosystems in general. The aim of this research was to isolate, identify, and measure these forms of these emerging protozoa in the waste and surface waters of Yaoundé, Cameroon. Giardia spp cysts were identified by Lugol iodine staining, and the Cryptosporidium spp oocysts by the Ziehl-Neelsen technique. The cysts were oval in structure and varied in length from 7 um to 12.0 um. Axostyles were visible along the median line and nuclei were present. The oocysts were round in structure and varied in diameter from 4 um to 6 um. A double cell wall was seen in the apicomplexa. The highest concentrations of Giardia spp cysts were 560 cysts/L in the surface water and 650 cysts/L in the residual effluent, while the corresponding figures for Cryptosporidium spp were 1,110 oocysts/L in the stream and 1,500 oocysts/L in the effluent. The cyst and oocyst counts were higher in the direct effluent because they are released directly into the wastewater by feces, while they are diluted in the surface water, reducing their abundance. Turbidity has a significant effect (p<0.05) on the population dynamics of these microorganisms, thereby indicating the importance of suspended or colloidal particles in the dissemination of these pathogens in aquatic media. The suspended particles in the wastewater adsorb the oocysts and cysts, probably because of the interactions between the electric charges carried by suspended particles and those present at the surface of the parasites. The positive correlation observed between these parasites and ammonia may account for some of the die-off of these resistant forms, because ammonium ions in water are known to inactivate trophozoites and sporozoites present in cysts and oocysts. This may be due to the permeability of the protozoan membrane to the ammonium ion and other alkaline earth metals present in aqueous form in the biotope. These parasite forms in these media represent a considerable health risk to the inhabitants of the study zone who depend on this surface water for drinking. The small size of these parasitic forms, the nonfunctional water purification stations and ineffective water treatment systems expose the community to outbreaks of giardiasis and cryptosporidiosis.

Relationships of anatomical characteristics versus shrinkage and collapse properties in plantation-grown eucalypt wood from China

To explore the influence of the basic density on collapse-type shrinkage properties and to quantify the relationships of the main anatomical features with shrinkage and collapse properties, all above-mentioned parameters were determined and analyzed for three species of collapse-susceptible eucalypts, Eucalyptus urophylla, Eucalyptus grandis, and E. urophylla × E. grandis, planted in South China. The correlation coefficients were also determined and the corresponding regression equations were established with the anatomical parameters measured by using multiple linear regression. The results indicated that: (1) basic density was strongly positively linearly related to both unit tangential shrinkage (r = 0.970) and unit radial shrinkage (r = 0.959), weakly positively related to total shrinkage (r = 0.656 and 0.640 for tangential and radial, respectively), and weakly negatively related to residual collapse (r = 0.632 and 0.616 for tangential and radial, respectively). (2) The main factors affecting unit shrinkage were cell wall proportion (WP), microfibril angle (MFA), and double fiber cell wall thickness (DWT); factors playing an important role in total shrinkage were WP, ray parenchyma proportion (RP), and MFA, while RP had the highest effect on residual collapse (r = 0.949 and 0.860 for tangential and radial, respectively). (3) All corresponding regression models obtained were very suitable for the evaluation of relationships between the anatomical parameters and unit shrinkage, total shrinkage, and residual collapse, as measured using a moisture content of 28% as the fiber saturation point for all specimens.

Occurrence of Piscirickettsiosis-Like Syndrome in Tilapia in the Continental United States

From 2001 to 2003, tilapia (Oreochromis sp.) farms in Florida, California, and South Carolina experienced epizootics of a systemic disease causing mortality. The fish exhibited lethargy, occasional exophthalmia, and skin petechia. The gills were often necrotic, with a patchy white and red appearance. Grossly, the spleen and kidneys were granular with whitish irregular nodules throughout. Granulomatous infiltrates were observed in kidney, spleen, testes, and ovary tissues, but not in the liver. The granulomas contained pleomorphic coccoid bacteria, measuring 0.57 +/- 0.1 x 0.8 +/- 0.2 microm, that were Giemsa-positive, acid-fast-negative, and Gram-negative. The bacteria had a double cell wall, variable electron-dense and -lucent areas, and were present in the cytoplasm and within phagolysosomes. The syndrome was associated with cold stress and poor water conditions. These findings are consistent with an infectious process caused by a Piscirickettsia-like bacterium described previously in tilapia in Taiwan and Hawaii. This report involves the first identified cases of a piscirickettsiosis-like syndrome affecting tilapia in the continental United States.

Collapse-type shrinkage characteristics in plantation-grown eucalypts: I. Correlations of basic density and some structural indices with shrinkage and collapse properties

Collapse-type shrinkage is one of highly refractory drying defects in low-medium density plantation-grown eucalypt wood used as solid wood products. Basic density (BD), microfibril angle (MFA), double fibre cell wall thickness (DWT), proportion of ray parenchyma (RP), unit cell wall shrinkage, total shrinkage and residual collapse, which are associated with collapse-type shrinkage characteristics, were investigated by using simple regression method for three species of collapse-susceptibleEucalyptus urophyll,, E. grandis andE. urophylla×E.grandis, planted at Dong-Men Forest Farm in Guangxi autonomous region, China. The results indicated that: unit cell wall shrinkage had a extremely strong positive correlation with BD, moderately strong positive correlation with DWT, and a weakly or moderately negative correlation with RP and MFA; total shrinkage was positively correlated with BD, DWT and RP and negatively related to MFA, but not able to be predicted ideally by any examined factors alone owing to lower R2 value (R2≦0.5712); residual collapse was negatively correlated with BD and DWT, linearly positively correlated with MFA, and had strongly positive linear correlation with RP. It is concluded that BD can be used as single factor (R2≥0.9412) to predicate unit cell wall shrinkage and RP is the relatively sound indicator for predicting residual collapse

Characterization of a piscirickettsiosis-like disease in Hawaiian tilapia.

In 1994, tilapia (Oreochromis mossambicus and Sarotherodon melanotheron) in wild and farmed populations on Oahu, Hawaii, USA, began to die of an unknown disease that was similar but not identical to piscirickettsiosis in salmonids. Only tilapia were affected. Diseased tilapia often swam erratically and had trouble staying at depth. Scattered cutaneous haemorrhage and exophthalmia were often noted. In many cases, fish were found dead with no clinical signs. Gills exhibited epithelial hyperplasia with severe multifocal consolidation of secondary lamellae. Multiple granulomas were observed in the gills, spleen, kidney, choroid gland and testes, but not in the liver. Tilapia mortalities occurred only during the cooler months (October to April) of the year and were not recorded during the warmer months (May to September). The mortalities declined with each successive year, after the 1994 outbreak, and currently losses are sporadic. Oxytetracycline-medicated feed reduced mortality. Cytologic examination of blood smears revealed moderate to large numbers of Gram-negative, pleomorphic, intracellular bacteria in rare circulating monocytes. Histologically, some predilection for nervous tissue and brain was observed. When viewed with transmission electron microscopy, pleomorphic coccoid bacteria, measuring 0.56 +/- 0.14 x 0.7 +/- 0.20 microm, occurred free in the cytoplasm and within phagolysosomes. The organisms had a double cell wall, no defined nucleus and variable electron-dense and -lucent areas. Unlike Piscirickettsia salmonis, the agent of piscirickettsiosis, the Hawaiian tilapia Piscirickettsia-like organism (HTPLO) does not form craterform lesions in the liver and is active above 20 degrees C. HTPLO can be transmitted horizontally by cohabitation, and cold stress induces the syndrome in juvenile tilapia from farms where the disease is endemic.

Congo Red Effect on Cyst Viability and Cell Wall Structure of Encysting Entamoeba invadens

Background The cell wall of Entamoeba invadens cysts is composed of chitin microfibrils as the main structural component. It has been demonstrated in yeast that the chitin cell wall assembly is altered by dyes such as Congo red (CR) and Calcofluor. Methods The purpose of this work was to study the cell wall assembly under the effect of CR dye on encysting E. invadens by means of light and electron microscopy, after the amebas were subjected to the effect of 100–2,000 μg CR/mL. Experiments were performed either in BI-S-33 or in mLG media. Results Trophozoite growth was not inhibited by 100–1,000 μg/mL CR after 8 days of incubation in BI-S-33 medium. However, low levels of growth were observed with 2,000 μg/mL of dye. No significant differences in morphologically viable (hyaline) cyst production occurred after 24–48 h, when 100 μg CR/mL was used, while the highest concentration of CR (2,000 μg/mL) resulted in a significant decrease of hyaline cyst yield; dead cysts prevailed in cultures, particularly at 72 h of CR treatment. Differentiation of amebas incubated in the presence of 500–2,000 μg/mL CR produced abnormal chitin deposits, rendering irregularly thick or double cell walls, as shown by transmission and scanning electron microscopy. Cyst cultures obtained under 100 μg/mL CR produced as many trophozoites as did the control when they were incubated in BI-S-33, but only low numbers of trophozoites were found in culture cysts obtained under higher CR doses. Conclusion Our results suggest that CR affects E. invadens encystment, alters the cell wall formation, and also affects the cyst viability.

Heat transfer efficiency of metal honeycombs

The efficiency of micro-cell aluminium honeycombs in augmenting heat transfer in compact heat exchangers is evaluated using analytical models. For convective cooling, the overall heat transfer rate is found to be elevated by about two order of magnitudes when an open channel is designed with an aluminium honeycomb core. The performance is comparable to that achieved by using open-celled aluminium foams, but attributed to different mechanisms. At low Reynolds numbers (<2000) , the flow is essentially laminar in honeycombs, in contrast to the largely turbulent flow in metal foams; this deficiency in fluid dynamics is compensated for by the superior surface area density offered by honeycombs over foams. Another advantage of designing heat sinks with honeycombs is the relatively small pressure drop experienced and minimal noise generated by the laminar flow. The overall heat transfer rate of the heat sink is maximised when the cell morphology of the honeycomb is optimised. However, the optimal cell morphology is not constant but dependent upon the geometry and heat transfer condition of the heat sink as well as the type of convective cooling medium used. For air cooling, the optimal relative density of the honeycomb is about 0.1. Other related effects, such as cell orientation and double cell wall thickness, are discussed.

Tracheidenmorphologie der Atlaszeder in Abhängigkeit vom Kambialalter

The fibre morphology of Cedrus atlantica (Endl.) Manetti ex Carriere was investigated in six sample trees from a thinning stand (Catalonia/Spain) at the age of 34 years. The following tracheid variables were measured : double cell wall thickness, lumen diameter and length. A pith to cambium gradient was determined for all investigated tracheid variables at 2.5 m and 5.0 m tree height subdivided into increment zones, earlywood and latewoood.

Effects of chemical treatments on ultra-high-yield pulping 1. Fiber separation

Specially designed wood blocks from Norway spruce were used to study the nature of the fracture surfaces developed in shear using a tensile tester. In the case of the control (water-soaked blocks), the fracture in the latewood takes place mainly in the S1 layer while in the earlywood the fracture occurs across the double cell wall. After dilute alkali treatment, some earlywood cells also fracture in the S1 layer. For sulfite-treated samples, on the other hand, both earlywood and latewood fracture in the middle lamella.

Invasion and survival ofFusarium solaniin the dexamethasone-treated cornea of rabbits

Electron microscopic observations, as well as in vitro experiments, on experimental Fusarium solani keratitis of rabbits were performed to study the mode of fungal invasion into the corneal stroma, the interactions between F. solani and inflammatory cells under the influence of topical dexamethasone (DXM) treatment, and the survival mechanism of the fungi in the DXM-treated cornea. Electron microscopy showed that, while the fungus invaded into the corneal stroma, digestion of collagen fibrils occurred around the hyphae, where amorphous material was often noted. In DXM-nontreated cornea, the fungal hyphae were entrapped by pseudopodia of the neutrophils and destruction of the hyphae was noted on day 3 of infection, most hyphae having disappeared by day 7. In the DXM-treated cornea, however, neutrophils could not ingest and destroy the hyphae. In qualitative nitroblue tetrazolium (NBT)-reduction tests using rabbit peripheral blood neutrophils, DXM significantly suppressed the rate of NBT-reduction and the rate of adherence to the fungal microconidia. In the DXM-treated corneal lesions, a considerable increase in both number and size of fungal peroxisomes was noted. Furthermore, the hyphae, surrounded by neutrophils, showed double or triple cell wall formation or sometimes a hypha-in-hypha structure. Similar hypha-in-hypha structures were also observed when the organisms were treated in vitro with a fungistatic concentration of H2O2. We suggest that this special structure is a protective device produced for the survival of F. solani when subject to neutrophil attack in the DXM-treated cornea.

SEM and shrinkage analyses of Southern Pine wood following pyrolysis

Samples of Southern Pine (Pinus spp.) charred to 250°, 300°, 350°, 400° or 600°C in a flowing nitrogen atmosphere at rates of 1°, 10° and 50°C/min were examined using the scanning electron microscope to quantify changes in cross-sectional tracheid dimensions. The disappearance of discrete cell wall layers was time-dependent as opposed to strictly temperature-dependent. Tracheid diameters decreased in response to temperature and charring rate. Double cell wall thickness values also decreased in response to charring. This shrinkage was nearly isotropic. Below 300°C, latewood cells were more stable than earlywood cells. Above 300°C, the reverse was true. This was attributed to the probable circumferential arrangement of cellulose, hemicellulose, and lignin within the cell wall. The highest rate of thermal degradation was between 300° and 350°C.

Cross sectional dimensions of wood pulp fibers from softwood fiber counts

There are, on the average, about 300 fibers or tracheids per centimeter in both the tangential and radial directions in cross sections of softwoods when the counts are made over complete annual rings with the extremes varying from about 200 fibers per centimeter for redwood to about 400 fibers per centimeter for Alaska yellow cedar. Fiber widths, including half of surrounding middle lamella, range from about 50 μm for redwood to 25μm for Alaska yellow cedar, averaging about 33 μm. Average lumen widths vary but slightly with changes in the specific gravity of the wood whereas the double cell wall thickness varies directly with the specific gravity. Effects of pulping to different pulp yields on the fiber dimensions are calculated with the use of two newly developed equations. The theoretical thickness of completely collapsed pulp fibers is equal to their double cell wall thickness. Complete collapse rarely if ever occurs as it requires double fractures of the cell wall. In practice, collapse of fibers is incomplete so their thickness is usually two or more times the theoretical minimum.

Cell Dimensions and their Relationship to the Chemical Nature of the Lignin from the Wood of Broad-leaved Trees

The dimensions of the various structural elements of 14 samples of wood from 10 broad-leaved species were determined by ultraviolet and scanning electron microscopy. A relationship was found between the chemical structure of the lignins and the morphological characteristics of the woods. The ratio of the thickness of the double cell wall of the fibres to their width increased with the increasing syringyl content of the lignin. A similar increase with syringyl content of the lignin was noted for the ratio of the vessel wall thickness to the vessel width. It is suggested that these trends are related to the availability of oxygen during the lignification process.

Microspectrophotometric observations on the cell walls of Japanese radish ( Raphanus sativus) root infected by Peronospora parasitica

Fresh sections were cut, at 20 μm, of Japanese radish root infected by Peronospora parasitica. Parenchyma double cell walls, 2 to 3 μm wide, were observed with monochromatic beams of ultraviolet and visible radiation. High ultraviolet absorption in the diseased walls and slight absorption in the healthy walls were observed. A considerable ultraviolet absorption could still be demonstrated when the diseased walls were fractionated with a cold alkali solution. The recordings of absorbance across the diseased double wall indicated that higher lignin accumulation was present in the middle portion of the wall. Furthermore, the alkali-treated healthy wall could be dissolved in cuprammonium solutions whereas the diseased wall could not.