Swollen Cell Walls Research Articles

Short-term high temperature with shear produces tomato suspensions with desirable rheological properties

This research introduced a modified technology processing whole tomatoes for producing superior tomato suspensions using a twin-screw continue processor at a high temperature with shear for a short period of time (manually feeding rate of 1 kg/min, rotating speed 120 rpm). The effect of temperature (100, 90, and 75 °C) with the presence of shear on rheological properties of tomato suspensions was analyzed. High temperature (100 °C) sheared tomato suspension had desirable viscosity and yield stress, which were significantly higher than the suspensions processed at 90 and 75 °C. The desirable rheological properties of high temperature sheared tomato suspension can be explained by high volume of suspended particles and high viscosity of continuous serum phase. Upon heat treatment with shear at 100 °C, the heat-induced hydration and swelling of tomato cell wall resulted in large particle sizes and promoted the release of solutes to the serum. • High temperature (100 °C) short-term shear produced superior tomato suspensions. • Shear at 100 °C on whole tomatoes resulted in high viscosity, G′, and yield stress. • Superior quality of tomato suspension related to swollen cell wall and viscous serum. • Short-term shear at 100 °C caused high solid content in tomato serum. • An efficient and effective tomato processing method was successfully developed.

Development of extracts obtained from yerba mate leaves with different industrial processing steps: Antimicrobial capacity, antioxidant properties, and induced damage

This study was aimed at developing a yerba mate extract (YME) intended to be used as food additive with antioxidant and antimicrobial capacity. For the extraction, yerba mate (Ilex paraguariensis, St Hill) leaves collected from three industrial processing steps (green, unaged-canchada, and aged-canchada) were used. The aged-canchada YME exhibited higher theobromine, chlorogenic acid, caffeic acid, caffeine, and kaempferol than green YME. It was selected for further analyses as it showed the highest polyphenol content (PC = 3.7 ± 0.3 mg GAE/ml) and total antioxidant activity (TAA) by DDPH (573 ± 4 mg Trolox Eq/ml) while possessed the lowest minimum inhibitory (MIC) and minimum bactericidal (MBC) concentrations in culture media against E. coli and S. Enteritidis. Additionally, its MBC value was validated in a green juice. Moreover, aged-canchada YME addition (0.04%wt/vol) doubled PC, TAADPPH, and TAAABTS in the juice blend. Transmission electron microscopy images of E. coli cells exposed to the aged-canchada extract revealed severe cell damage encompassing direct rupture of outer structures with efflux of inner cell content, formation of vacuoles, vesicles, and swollen cell walls. In conclusion, the aged-canchada YME may be used as a food additive with the main purpose of increasing the concentration of bioactive compounds and contributing to the overall antimicrobial activity in the food product. Practical applications There is an increasing demand for the use of plant-based antimicrobials and/or antioxidant properties as a total or partial replacement of synthetic preservatives which are usually related to the appearance of allergies and other health issues. The present work investigated the potential use of an aged-canchada yerba mate extract, obtained by ultrasound, as a food additive. This extract exhibited the highest antimicrobial activity against relevant bacteria compared to other extracts obtained from different industrial stages. The extract added to a green juice doubled its concentration of antioxidants, thus positively contributing to the daily intake of these health-promoting compounds.

The mechanism of rain cracking of sweet cherry fruit

Sweet cherry (Prunus avium L.) cracking is a severe limitation in production worldwide. It is thought to be caused by excessive water uptake and a subsequent increase in turgor. When a critical threshold is exceeded (‘critical turgor’) the fruit is believed to crack. Experimental evidence supporting this wide spread concept is lacking. Instead, published data question the critical turgor hypothesis and an alternative explanation must be thought of. This mini review summarizes experimental research published in the last two decades that resulted in an alternative explanation of sweet cherry fruit cracking, the so called Zipper hypothesis. According to this hypothesis, cracking is the result of a series of events that ultimately propagate a crack through skin and flesh and ‘unzip’ the fruit. It is based on the following sequence of events: Tension (stress) develops in the skin during stage III growth and particularly in the cuticle due to a downregulation of genes involved in cutin and wax synthesis. Stress in the skin results in strain and microcracks in the cuticle. Furthermore, surface wetness on and high humidity above the strained cuticle aggravates microcracking. Microcracking impairs the cuticle’s barrier function and focuses water uptake in a particular region of the fruit surface. Water bypasses the cuticle, penetrates into the fruit and moves to sites where water potential is most negative. These are the large thin-walled parenchyma cells of the outer mesocarp that have a more negative osmotic potential than the small thick walled epidermal and hypodermal cells. Water uptake causes individual cells to burst. As a consequence, cell content leaks into the apoplast. Major constituents of sweet cherry such as glucose, fructose and malic acid now occur in the apoplast at comparable concentrations as in the symplast. The consequences are several fold: First, cell turgor decreases and is entirely lost when epidermal cells plasmolyse in the juice from the flesh. Second, malic acid extracts cell wall bound Ca, weakens cell walls and increases the permeability of plasma membranes causing a chain reaction of leakage of adjacent cells. The leakage of cells and the loss of the (low) turgor results in swelling of cell walls, in particular of the pectin middle lamella. Swollen cell walls have decreased stiffness, fracture tension and cell adhesion resulting in the separation of neighbouring cells along their cell walls. The tension generated by the strain of the skin is now sufficient to cause the cells to separate along their swollen walls and to rupture the skin. This process continues at the crack tip where the stress concentrates and causes the crack to elongate. The skin ‘unzips’ in the same way like a ‘zipper’ or a ‘ladder’ that propagates in a piece of knitted fabric.

Bound Water Content and Pore Size Distribution in Swollen Cell Walls Determined by NMR Technology

Nuclear magnetic resonance (NMR) relaxation time distributions can provide detailed information about the moisture in wood. In this paper, the bound water content and pore size distributions in swollen cell wall of two kinds of softwoods (Pinus sylvestris and Cunninghamia lanceolata) and three kinds of hardwoods (Populus sp., Fraxinus excelsior L., and Ochroma lagopus) were determined by NMR cryoporometry. The total bound water content of swollen cell wall almost exceeds 35%, based on dry mass, which is obviously higher than the fiber saturation point (FSP) (appr. 30%) measured by the extrapolation method. The bound water content of different species is consistent with the hypothesis that with the decrease of basic density, the more bound water could be contained in wood. The proportion of the pore diameter smaller than 1.59 nm is higher than 70%, and the proportion of the pore diameter larger than 4 nm is no more than 10%.

Comparative Anatomy of Ovules in Galinsoga, Solidago and Ratibida (Asteraceae)

Abstract Many Asteraceae species have been introduced into horticulture as ornamental or interesting exotic plants. Some of them, including Solidago and Galinsoga, are now aggressive weeds; others such as Ratibida are not. Special modifications of the ovule tissue and the occurrence of nutritive tissue have been described in several Asteraceae species, including invasive Taraxacum species. This study examined whether such modifications might also occur in other genera. We found that the three genera examined - Galinsoga (G. quadriradiata), Solidago (S. canadensis, S. rigida, S. gigantea) and Ratibida (R. pinnata) - differed in their nutritive tissue structure. According to changes in the integument, we identified three types of ovules in Asteraceae: “Taraxacum” type (recorded in Taraxacum, Bellis, Solidago, Chondrilla), with well-developed nutritive tissue having very swollen cell walls of spongy structure; “Galinsoga” type (in Galinsoga), in which the nutritive tissue cells have more cyto-plasm and thicker cell walls than the other integument parenchyma cells, and in which the most prominent character of the nutritive tissue cells is well-developed rough ER; and “Ratibida” type (in Ratibida), in which the nutritive tissue is only slightly developed and consists of large highly vacuolated cells. Our study and future investigations of ovule structure may be useful in phylogenetic analyses.

Impact of the industrial freezing process on selected vegetables — Part I. Structure, texture and antioxidant capacity

In this work, the impact of the industrial freezing process on structure, texture and total antioxidant capacity was studied using green asparagus stems, zucchini and green beans. Samples were analysed as raw/uncooked, blanched, raw/boiled and industrially frozen/boiled.A consistent damage of the vegetable tissue was revealed by the histological analysis on vegetables boiled after freezing. The cells appeared to be dehydrated, contracted and separated at different levels depending on the anatomical structure of each vegetable.The initial textural quality was partially retained in all blanched vegetables, and enhanced in cut tested asparagus stems, in relation to the action of phenolic acids at cell wall level. Raw/boiled and industrially frozen/boiled asparagus stems exhibited comparable forces of penetration and cut tests. On the other hand, zucchini, both raw and frozen, completely softened after boiling making the texture measurement impossible. Industrially frozen/boiled green beans showed higher values of cut and penetration forces, probably due to a higher presence of swollen cell walls, in comparison to those raw/boiled.Blanching and boiling significantly increased the ferric reducing antioxidant power values of asparagus stems and green beans compared to uncooked/raw samples, while boiling after the freezing process significantly deprived both vegetables of the initial antioxidant capacity. On the other hand, boiling the frozen zucchini proved to be detrimental to the antioxidant capacity.In conclusion, manufacturers and researchers should join together to develop specific industrial freezing process conditions according to the matrix of each vegetable.

Mechanical properties of water hyacinth fibers – polyester composites before and after immersion in water

This study reported moisture absorption of untreated and treated individual water hyacinth (WH) fibers as well as comparison the mechanical properties of WH fibers – unsaturated polyester (UPR) matrix composites after and before immersion in water. The result shows that the individual WH fibers treated with various alkali concentration did not exhibit significantly decreases of their moisture absorption. SEM photograph in cross section of the treated WH fibers shows swollen cell wall containing more nano and micro hollows. Tensile and flexure strength of the wet composite samples are lower than that of dried ones. However, increases volume fraction of the WH fibers in UPR matrix affected slightly on enhancement mechanical properties of the composite samples.

“Stump Horizon” in the Bílina Mine (Most Basin, Czech Republic) — GC–MS, optical and electron microscopy in identification of wood biological origin

Numerous coalified tree stumps remained preserved in-situ in the so-called “Stump Horizon” (the palaeontologic horizon No. 31), which represents clayey overburden of the main coal seam in the Bílina open cast mine in the Most Basin (Czech Republic). The petrological and chemical composition, palaeobotanical origin and preservation of 24 selected tree stumps were studied by optical and scanning electron microscopy and gas chromatography–mass spectrometry (GC–MS). Composition of the fossil wood is dominated by ulminite, particularly texto-ulminite B. Textinite forms up to 38vol.% in the decomposed tree stumps. Corpohuminite dominates in bark and root tissues. Partly gelified and deformed woody tissues contain both corpohuminite and resinite fillings. Random reflectance of ulminite ranges from 0.33% to 0.39% and carbon content from 49wt.% to 78wt.%. Samples represent pure woody material with small admixtures of clay minerals, siderite, and very rare pyrite. Observations by scanning electron microscopy revealed various levels of deformed secondary xylem with more or less swollen cell walls, conspicuous tracheids, uniseriate rays of a different height, and round or cylinder-like resin or corpohuminite bodies. According to our results and other published data the wood might belong to Glyptostroboxylon and Taxodioxylon genera that are supposed to belong to Glyptostrobus and Quasisequoia plants respectively, representatives of the coniferous family Cupressaceae. The biomarker composition in the extracts of the fossil wood includes sesquiterpenoids (α-cedrane, drimane, eudesmane), diterpenoids (abietane, fichtelite, 16α(H)-phyllocladane) and their degraded compounds. The terpenoids are derived from precursors produced by the source plants and microorganisms. The terpenoid signatures support a relationship to the Cupressaceae family with input of microbial species. These characteristics were identical for all studied samples. Significant variations have been observed in sesquiterpenoid α-cedrane and diterpenoid 16α(H)-phyllocladane contents.

Down-regulation of UDP-glucuronic Acid Biosynthesis Leads to Swollen Plant Cell Walls and Severe Developmental Defects Associated with Changes in Pectic Polysaccharides

UDP-glucose dehydrogenase (UGD) plays a key role in the nucleotide sugar biosynthetic pathway, as its product UDP-glucuronic acid is the common precursor for arabinose, xylose, galacturonic acid, and apiose residues found in the cell wall. In this study we characterize an Arabidopsis thaliana double mutant ugd2,3 that lacks two of the four UGD isoforms. This mutant was obtained from a cross of ugd2 and ugd3 single mutants, which do not show phenotypical differences compared with the WT. In contrast, ugd2,3 has a strong dwarfed phenotype and often develops seedlings with severe root defects suggesting that the UGD2 and UGD3 isoforms act in concert. Differences in its cell wall composition in comparison to the WT were determined using biochemical methods indicating a significant reduction in arabinose, xylose, apiose, and galacturonic acid residues. Xyloglucan is less substituted with xylose, and pectins have a reduced amount of arabinan side chains. In particular, the amount of the apiose containing side chains A and B of rhamnogalacturonan II is strongly reduced, resulting in a swollen cell wall. The alternative pathway to UDP-glucuronic acid with the key enzyme myo-inositol oxygenase is not up-regulated in ugd2,3. The pathway also does not complement the ugd2,3 mutation, likely because the supply of myo-inositol is limited. Taken together, the presented data underline the importance of UDP GlcA for plant primary cell wall formation.

An investigation of the cell wall ultrastructure of the sapwood of ten Greek wood species by means of chemical modification

The aim of this study was to investigate the cell wall ultrastructure of the sapwood of ten Greek wood species using chemical modification. Reactions with different sized anhydride molecules were performed on oven-dry samples in the presence of water-free xylene, which does not swell the cell wall. Reactions were also performed under identical conditions, but on wood samples that had been dried under solvent exchange conditions, thereby retaining the swollen cell wall pore structure. The results indicated that the diameters of the micropores in the cell wall of oven dried ash and elm are smaller than 0.80 nm and larger than 0.74 nm, those of beech, fir, Douglas fir, hornbeam and pine (Pinus nigra) smaller than 0.74 nm and larger than 0.66 nm, whereas those of maple, poplar, pine (Pinus sylvestris) are smaller than 0.66 nm.

Characterisation of the undissolved residuals in CMC-solutions

The undissolved fibre and gel residuals that had not completely reacted to form fully dissolved carboxymethyl cellulose (CMC) ID the production of CMC were studied to clarify the reactivity of wood components ID the pulp. The undissolved residuals, the pulp and the CMC were therefore analysed on the fibre level, the cell-wall level and the chemical composition level. The results may be interpreted as indicating that the presence of undissolved residuals ID the CMC was not due to any chemical difference. The undissolved residuals were shown to consist mainly of swollen cell wall parts and some whole wood cells, mainly thick-walled compression wood and summerwood cells. They react more slowly ID the mercerisation and etherification, probably because of a greater diffusion resistance due to their larger dimensions or to a more dense structure. These cells are assumed to be less accessible for chemical penetration, but they may also contain supramolecular structures that slow down the CMC reaction.

Determination of surface area and pore volume of holocellulose and chemically modified wood flour using the nitrogen adsorption technique

Very low surface area (ca. 0.5 m2/g) and a low pore volume (ca. 0.002 cm3/g) have been obtained for oven dried wood, using the nitrogen adsorption technique. The microporous structure of wood flour was partially preserved by the solvent exchange drying (SED) employed in this study, in particular when toluene was used as a final solvent. However, the resulted surface area (ca. 6 m2/g) and a pore volume values (ca. 0.015 cm3/g) indicated that such a structure is in no way representative of a fully swollen cell wall. By using solvent exchange drying (SED), it is possible to preserve the swollen pore structure of holocellulose samples. However, with samples which contain significant amounts of lignin, such as native wood, it is not possible to prevent re-collapse of the pores. This problem arises because as micropore swelling occurs, the surrounding lignin network of the cell wall is stretched. When the molecules occupying the micropores are removed, the lignin returns to its original configuration, re-collapsing the micropores in the process. Chemical modification resulted in significant reduction in surface area and pore volume, possibly a result of pore blocking by the large acyl group.

Application of Microbial Genes to Recalcitrant Biomass Utilization and Environmental Conservation

Recent papers concerning the application of microbial genes to recalcitrant biomass utilization and environmental conservation are reviewed. Microbial genes have been integrated and expressed in plants and microorganisms. When cellulose-degrading enzyme genes are expressed in rice plants, the transgenic plants exhibit swollen cell walls which increases the digestibility of rice straw in the rumen. When genes encoding aromatic compound-degrading enzymes are expressed in plants, it is expected that aromatic compounds contaminating soil would be degraded during the growth of the transgenic plants. The former transgenic plants are utilized as feed and the latter for phytoremediation. Dockerin and cohesin interactions occurring in the cellulase complex, cellulosome, are applied to the construction of artificial enzyme complexes and protein purification by expressing the genes in transformed bacteria and/or silkworms, respectively. In the case of the forced expression of bacterial genes encoding chitinase and/or hydrogenase in the wild-type bacteria, chitin degradation and hydrogen gas production in the transformed bacteria occur at much higher rates than in the wild type.

The penetration of epoxy resin into plant fibre cell walls increases the stiffness of plant fibre composites

A treatment is described that enables epoxy resin to penetrate into the cell walls of plant fibres. This ensures a very good interface in the cured composites, mimicking the way that interfaces are formed in animal and plant materials. The treatment involves swelling the plant cell walls with urea solution, washing out the excess urea and then replacing the water with alcohol in a graded series. Epoxy resin can then penetrate into the swollen cell wall and mix with the alcohol. The alcohol is probably driven off during curing of the resin. This treatment increased the stiffness of composites made from flax fibres and epoxy resin.

Boron nutrition of cultured tobacco BY-2 cells. III. Characterization of the boron-rhamnogalacturonan II complex in cells acclimated to low levels of boron.

Cultured cells of tobacco (Nicotiana tabacum L.) BY-2 which could propagate at the same rate as the parent cells (1 mg B liter(-1)) under a lower level of boron (0.01 mg B liter(-1)) were obtained. The selected cells had swollen cell walls. In the parent cells, all the RG-II occurred as a B-RG-II complex, however, two-thirds of the RG-II occurred in a monomeric form in the selected cells.

Planing frozen hydrated plant specimens for SEM observation and EDX microanalysis.

A procedure is described for forming a flat face on a frozen piece of plant tissue, which may then be observed fully-hydrated or lightly etched, and coated or uncoated with a metal film, in scanning electron microscopy (SEM). The frozen sample was planed with a glass knife at -80 degrees C in a cryo-ultramicrotome. The sections were discarded, and the planed block face placed on the cold stage in the microscope column, either for observation uncoated at low kV, or for light etching (-90 degrees C) to reveal the cell outlines. If a higher accelerating voltage was needed, the face was given an evaporative coating of Al in the cryo-preparation chamber and returned to the column. The advantages of the planed face over the usual fracture face are illustrated: imaging at a chosen rather than a chance position; clearer cellular and subcellular detail; preservation of hydrated gels like mucilage and swollen cell walls; the possibility of making serial parallel sections through the same piece of tissue; opportunities for accurate morphometric analyses on the planed face; capacity to produce longitudinal sections; preservation of very delicate structures that are destroyed by fixation and drying. A major advantage of the Al-coated planed face is the increased accuracy of energy-dispersive X-ray (EDX) microanalyses on a smooth rather than a rough surface. Tests are included which show that neither the light etching employed, nor successive planing, interferes with the analyses of elements in the frozen face.

THREE METHODS OF STUDYING CAPILLARY STRUCTURE AS APPLIED TO WOOD

Three different physical methods for studying the capillary structure of porous materials are developed and applied to the study of the fine effective continuous capillary structure of wood. The three characteristic capillary properties measured are, (1) the ratio of effective capillary cross section to the effective length, (2) the average effective capillary radius, and (3) the maximum effective capillary radius. Some of the important characteristics of the porous structure of wood are briefly presented in order to show that the major part of the void structure, the fiber cavities, have very little to do with the permeability of wood. The pores in the pit membranes which connect the adjacent fiber cavities are shown to be the structure effective in controlling permeability of wood. The pores in the pit membranes in general, are below microscopic visibility, thus necessitating other means of study. The ratio of the effective capillary cross section to the effective capillary length is determined from electrical resistance measurements of strong salt solutions filling the void structure and from the specific resistance of the salt solutions in bulk. Strong salt solutions are used in order to make the surface conductivity negligible as well as the conductivity of the swollen cell wall. The average effective capillary radius is determined by combining the results of the preceeding measurements with results obtained from hydrostatic flow studies of a continuous water phase extending through the section. Poiseuille's law is used for the calculations. A differential pressure drop apparatus was devised for these measurements in which the flow of liquid through a standard capillary tube and the test specimen connected in series is determined by measuring the pressure drop through each. The maximum effective capillary radius is determined by measuring the gas pressure required to overcome the effect of the surface tension of water in the capillary systems. The data show the large differences between the fine capillary structure of heartwood and of sapwood.