Cell Wall Level Research Articles

Histochemical and gene expression changes in Cannabis sativa hypocotyls exposed to increasing concentrations of cadmium and zinc

Hemp (Cannabis sativa L.) is a versatile crop that produces cellulosic bast fibres used in textiles and biocomposites. Is also finds use in phytoremediation, being a good candidate for the cultivation on marginal lands, such as those contaminated by heavy metals (HMs). HMs like cadmium (Cd) and zinc (Zn) are known to affect plant growth and impair the biosynthesis of cellulose and lignin at the cell wall level. Since cellulose is the major component in the gelatinous layer of bast fibres, HMs can impact the structure of hemp fibres and, consequently, their mechanical properties. This study investigates how varying concentrations of Cd and Zn in the soil affect the bast fibres of hemp plantlets. The chosen model is the hypocotyl, as it is ideal for studying bast fibre development: it exhibits a temporal separation between the elongation and thickening phases within a short period of approximately three weeks. C. sativa plantlets were grown for 20 days, and the hypocotyls sampled to perform histochemical observations, gene expression analysis, as well as to quantify biomass yield and Cd/Zn accumulation. Hemp plantlets grown in soils with the three highest Zn concentrations were smaller than the control group, whereas no decrease in size was observed under elevated Cd concentrations. However, at the highest Cd concentration, the root system exhibited enhanced development, accompanied by a significant increase in dry weight across all the concentrations tested. The quantification of Cd and Zn showed that the roots were the main organs accumulating HMs. Cd at the two highest concentrations decreased significantly the lumen area of bast fibres and increased their cell wall thickness. Zn decreased significantly the lumen area, but it did not impact the thickness of the cell wall at the highest concentration. Cd also increased the number of secondary fibres. Immunohistochemistry highlighted a different pattern of crystalline cellulose distribution with a signal that was less homogeneous in the presence of Cd and Zn. Gene expression analysis revealed changes in transcripts encoding cellulose synthases, fasciclin-like arabinogalactan proteins, class III peroxidases. The results obtained shed light on the molecular response and bast fibre histological changes occurring in young hemp plants exposed to Cd and Zn.

Identification and characterization of a novel Haematococcus pluvialis strain resistant to Paraphysoderma sedebokerense infection

The commercial culture of Haematococcus pluvialis is threatened by the pathogen Paraphysoderma sedebokerense, leading to substantial losses in the natural astaxanthin industry. This study successfully identified a novel H. pluvialis strain WBG-26, which exhibited high resistance to P. sedebokerense in both laboratory and open raceway ponds. Comparative analysis showed that the resistant strain WBG-26 had a thicker cell wall and lower levels of specific monosaccharides which may be closely related to resistance. RNA-sequencing analysis revealed differential gene expression profiles, with 29 up-regulated and 25 down-regulated genes identified as crucial for resistance. Using bioinformatics analysis, we identified several potential resistance genes and resistance-related genes, such as those encoding receptor-like kinases, leucine-rich repeat, transcription factors, CAZymes, and heat shock proteins, which may play critical roles in defense response. This study represents a comprehensive investigation of multiple defense mechanisms of microalgae, providing insights into breeding disease-resistant microalgal strains for biotechnological applications.

A comparative study of the cell wall level delignification behaviour of four Nordic hardwoods during kraft pulping

Abstract Wood is a heterogeneous material with significant variation among species. This inherent complexity poses a challenge to the continuous expansion of our understanding of the kraft process; yet previous pulping research has mainly been limited to a few species. This study investigates variations among some less studied species and their cell wall level delignification behaviour during kraft pulping. Ground wood of birch, beech, aspen, and alder were pulped at near-constant composition and temperature conditions. Minor, yet significant, differences in the rates of their delignification were observed: aspen had a pronounced fast rate during the initial stage, whereas alder delignified more slowly relative to its high initial lignin content. The dissolution of xylan was substantially faster for birch. In contrast, no substantial differences were detected between the species in the molecular weight and structure of the dissolved wood components, suggesting that the different delignification behaviours stem from variations in the residual phase. The molecular weight distribution of dissolved lignin was uniform during the initial stage of pulping, which is indicative of rapid and extensive fragmentation. Subsequently, the weight increased continuously for the remainder of the process, suggesting that the mass transfer within the cell wall influenced the overall delignification kinetics.

Revealing spatial distribution and accessibility of cell wall polymers in bamboo through chemical imaging and mild chemical treatments

Understanding the distribution and accessibility of polymers within plant cell walls is crucial for addressing biomass recalcitrance in lignocellulosic materials. In this work, Imaging Fourier Transform Infrared (FTIR) and Raman spectroscopy, coupled with targeted chemical treatments, were employed to investigate cell wall polymer distribution in two bamboo species at both tissue and cell wall levels. Tissue-level Imaging FTIR revealed significant disparities in the distribution and chemical activity of cell wall polymers between the fibrous sheath and fibrous strand. At the cell wall level, Imaging Raman spectroscopy delineated a distinct difference between the secondary wall and intercellular layer, with the latter containing higher levels of lignin, hydroxycinnamic acid (HCA), and xylan, and lower cellulose. Mild acidified sodium chlorite treatment led to partial removal of lignin, HCA, and xylan from the intercellular layer, albeit to a lesser extent than alkaline treatment, indicating susceptibility of these polymers to chemical treatment. In contrast, lignin in the secondary wall exhibited limited reactivity to acidified sodium chlorite but was slightly removed by alkaline treatment, suggesting stable chemical properties with slight alkaline intolerance. These findings provide valuable insights into the inherent design mechanism of plant cells and their efficient utilization.

Comparative Studies on Tensile Mechanical Properties of Water-Saturated Earlywood and Latewood within the Same Growth Ring from Masson Pine

The tensile mechanical behavior of water-saturated earlywood (EW) and latewood (LW) within the same growth ring of Masson pine (Pinus massoniana) was investigated in the hydrothermal environment and discussed with respect to the density and microfibril angle (MFA) of the wood specimens. The tensile modulus, tensile strength, and strain at failure of EW and LW in the longitudinal (L) and tangential (T) directions were determined at different temperature levels ranging from 30 °C to 80 °C. Major differences in the tensile mechanical properties were found between EW and LW in the L and T directions. Compared to LW, EW showed a smaller density and a larger MFA, resulting in a lower tensile modulus, lower tensile strength, and higher strain at failure. Compared to the L specimens, the T specimens showed lower tensile modulus, lower tensile strength, and higher strain at failure. As the hygrothermal temperature increased, the MFAs, tensile modulus, and tensile strength of EW and LW specimens decreased, except for the MFAs of LW, while the strain at failure of the specimens showed the opposite trend. Variations in the tensile mechanical behavior between EW and LW were mainly influenced by the density and MFA of the specimens, and are closely associated with the hydrothermal softening properties of wood. These findings contribute to a further understanding of the structural–mechanical relationships of Masson pine wood at the cell wall level, and provide a scientific basis for the better utilization of plantation softwood in the hydrothermal environment.

Brassinosteroid decreases cadmium accumulation via regulating gibberellic acid accumulation and Cd fixation capacity of root cell wall in rice (Oryza sativa)

The precise mechanism behind the association between plants' reactions to cadmium (Cd) stress and brassinosteroid (BR) remains unclear. In the current investigation, Cd stress quickly increased the endogenous BR concentration in the rice roots. Exogenous BR also increased the hemicellulose level in the root cell wall, which in turn increased its capacity to bind Cd. Simultaneously, the transcription level of genes responsible for root Cd absorption was decreased, including Natural Resistance-Associated Macrophage Protein 1/5 (OsNRAMP1/5) and a major facilitator superfamily gene called OsCd1. Ultimately, the increased expression of Heavy Metal ATPase 3 (OsHMA3) and the decreased expression of OsHMA2, which was in charge of separating Cd into vacuoles and translocating Cd to the shoots, respectively, led to a decrease in the amount of Cd that accumulated in the rice shoots. In contrast, transgenic rice lines overexpressing OsGSK2 (a negative regulator in BR signaling) accumulated more Cd, while OsGSK2 RNA interference (RNAi) rice line accumulated less Cd. Furthermore, BR increased endogenous Gibberellic acid (GA) level, and applying GA could replicate its alleviative effect. Taken together, BR decreased Cd accumulation in rice by mediating the cell wall’s fixation capacity to Cd, which might relied on the buildup of the GA.

Influence of myoinositol on post-ripening and softening of Prunus salicina ‘Wushan plum’

To investigate the impact of myoinositol (MI) immersion treatment on the storage characteristics of Prunus salicina ‘Wushan Plum’, we assessed myoinositol content, ascorbic acid content, weight loss, decay rate, alteration in color, titratable acidity (TA), soluble solids (TSS), firmness, cell wall metabolism-related compounds, enzyme activities, and levels of gene expression throughout a 15-day storage period at 25 °C. The results revealed that MI treatment could increase myoinositol and ascorbic acid contents of fruit during the pre-storage period, effectively delay the color transformation and decay progression of P. salicina ‘Wushan Plum’ while maintaining elevated levels of TA and TSS. Furthermore, it suppressed the increase in weight loss and the decline in firmness. Notably, the delay in softening was more pronounced in the group treated with 100 mg L−1 MI compared to other groups. MI treatment regulated the expression levels of various genes associated with cell wall metabolism, which resulted in reduced activities of polygalacturonase (PG), pectate lyase (PL), pectin methylesterase (PME), cellulase (Cx), and β-glucosidase (β-Glu), and increased activities of phenylalanine ammonia-lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD). Furthermore, MI treatment maintained higher levels of covalently bound pectin (CSP), cellulose, and lignin, while decreasing the levels of water-soluble pectin (WSP) in the fruit. As a result, MI treatment could delay the depolymerization of cell wall polysaccharides and further delay the quality deterioration of P. salicina ‘Wushan Plum’ fruits under ambient storage environment and prolong the storage period.

A novel polyethylene nanopackaging combined with ozone fumigation delayed the browning and softening of Agaricus bisporus during postharvest storage

To elucidate the effect and mechanism of a novel polyethylene nanopackaging combined with ozone fumigation (O3 +NA) on delaying browning and softening of Agaricus bisporus during postharvest storage, quality changes under different treatments at low temperature over 18 d in storage were analyzed at the sensory, physiological and biochemical levels. It showed that, compared with ozone fumigation (O3), commercial polyethylene packaging (PE) and no packaging, O3 +NA improved the storage quality of mushrooms mainly by reducing the browning index, while maintaining firmness and whiteness. In comparison to the control group, O3 +NA increased the activities of antioxidant enzymes and reduced the accumulation of reactive oxygen species (ROS), thus maintaining the better antioxidant activity of A. bisporus. This combined treatment not only inhibited the activity of enzymes related to browning but also maintained low levels of cell wall degrading enzymes activity, which restricted the softening of A. bisporus during storage. Therefore, O3 +NA improved the storage quality of mushrooms. Compared with conventional commercial PE film packaging, O3 +NA prolonged the shelf-life of mushroom at low temperature by 6–9 d, providing an effective composite preservation technology.

Sucrose and Mannans Affect Arabidopsis Shoot Gravitropism at the Cell Wall Level.

Gravitropism is the plant organ bending in response to gravity. Gravitropism, phototropism and sufficient mechanical strength define the optimal position of young shoots for photosynthesis. Etiolated wild-type Arabidopsis seedlings grown horizontally in the presence of sucrose had a lot more upright hypocotyls than seedlings grown without sucrose. We studied the mechanism of this effect at the level of cell wall biomechanics and biochemistry. Sucrose strengthened the bases of hypocotyls and decreased the content of mannans in their cell walls. As sucrose is known to increase the gravitropic bending of hypocotyls, and mannans have recently been shown to interfere with this process, we examined if the effect of sucrose on shoot gravitropism could be partially mediated by mannans. We compared cell wall biomechanics and metabolomics of hypocotyls at the early steps of gravitropic bending in Col-0 plants grown with sucrose and mannan-deficient mutant seedlings. Sucrose and mannans affected gravitropic bending via different mechanisms. Sucrose exerted its effect through cell wall-loosening proteins, while mannans changed the walls' viscoelasticity. Our data highlight the complexity of shoot gravitropism control at the cell wall level.

Microscopic and nanoscale mechanical properties of tonkin cane bamboo measured by advanced AFM methods

Bamboo is a natural composite material with a high strength-to-weight ratio traditionally used in various consumer products as well as in building and modern advanced and sustainable manufacturing technology. While its macroscopic mechanical properties are well known, nanoscale studies of the mechanical properties of the hierarchical structure of bamboo at the level of individual cells and cell walls are lacking. Here we use different AFM-based methods to analyse the mechanical properties of individual bamboo fibres that are the foundation of the hierarchical structure at the nanoscale. The elastic modulus of the fiber in the outer region varies from 7.5 to 8.9 GPa, while that of the inner fiber ranges between 4.1 and 6.1 GPa. The results demonstrate that the fibre stiffness varies in nanoscale regions between fibre interior and the fibre wall and strongly depends on the position of the individual bamboo fibre within the culm. Outer fibres with high cellulose fibril density and low lignin level show low adhesion interaction force (13.5%) in the interface between cellulose and lignin/hemicellulose matrix, hence, resulting in low plastic deformation energy release during mechanical deformation. The implications of the interrelation of plasticity, lignin level, and adhesion force are discussed for the application of bamboo as a high-performance, renewable, and sustainable material.

Exploring Lignification Complexity in Plant Cell Walls with Airyscan Super-resolution Microscopy and Bioorthogonal Chemistry.

In this paper, we present the use of multiplex click/bioorthogonal chemistry combined with super-resolution Airyscan microscopy to track biomolecules in living systems with a focus on studying lignin formation in plant cell walls. While laser scanning confocal microscopy (LSCM) provided insights into the tissue-scale dynamics of lignin formation and distribution in our previous reports, its limited resolution precluded an in-depth analysis of lignin composition at the unique cell wall or substructure level. To overcome this limitation, we explored the use of Airyscan microscopy, which, among the super-resolution techniques available, offers an optimal balance between performance, cost, accessibility, and ease of implementation. Our study demonstrates that a triple labeling strategy using copper-catalyzed azide-alkyne cycloaddition (CuAAC), strain-promoted azide-alkyne cycloaddition (SPAAC), and inverse electronic-demand Diels-Alder cycloaddition (IEDDA) to label modified lignin metabolic precursors can be combined with Airyscan microscopy to reveal the zones of active lignification at the single cell level with improved sensitivity and resolution. This approach enables insights into the lignin composition in wall substructures, such as pits or in wall layers that are otherwise not distinguishable by classical LSCM. Our work emphasizes the importance of studying lignin formation in plant cell walls and demonstrates the potential of combining bioorthogonal chemistry and super-resolution microscopy techniques for studying biomolecules in living systems.

Utjecaj sadržaja vode u drvu na strukturnu cjelovitost drva pri dinamičkim opterećenjima

The majority of mechanical wood properties are negatively affected by wood moisture within the hygroscopic range, disregarding the stress relaxation of wood at very low moisture contents (MC). In contrast, the structural integrity and thus the brittleness of wood appears to be positively affected by moisture. This study aimed at examining the effect of wood MC on the structural integrity of wood between the oven-dry state and MC well above cell wall saturation (CWS), i.e., at approx. 100 %. For both softwood (Picea abies) and hardwoods (Fagus sylvatica and Quercus robur), the structural integrity was assessed on the basis of the Resistance to Impact Milling (RIM) originating from High-Energy Multiple Impact (HEMI) tests. RIM increased with increasing MC in the hygroscopic range, which might be explained by stress relaxation and ‘gluing effects’ inside the cell wall polymer structure, resulting from a growing network of hydrogen bonds on cell wall level. Increasing MC above CWS caused a slight decrease of RIM in the selected hardwood species, whereas no significant change in RIM was observed when MC varied in the range from CWS to approx. 100 % for the softwood species Norway spruce.

The biomechanical role of the functionally graded microfibrils in the wood cell wall

The cellulose microfibril in the wood cell wall possesses a functionally graded structure, the biomechanical contribution of which is unclear. At the molecular scale, we analyze the heterogeneous crystallinity of the microfibril and characterize its stiffness gradient with the help of molecular dynamics. The determined stiffness profile is then upscaled to the cell wall level, based on which a shear-lag analytical model is developed to reveal the load transfer mechanism in the cell wall. We find that the presence of the stiffness gradient can significantly alleviate the stress concentration on the interface by reducing the interfacial shear stress up to 70%. The analysis on the debonding procedure shows profoundly enhanced debonding resistance of the cell wall due to the graded structure. Moreover, we identify a novel “dual debonding” mode, meaning that the debonding initiates and propagates in both the edge and inner regions of the interface until the two debonded regions join each other, which is much more complex than the edge debonding mode exhibited by the conventional fiber-reinforced composites. The stress alleviating effect, together with the special debonding mode, profoundly postpones the interfacial debonding of the material, leading to a significantly enhanced debonding resistance. A discussion on the structural profile of the microfibril shows that the special “dual debonding” mode can only be achieved with specific stiffness gradients. In all, we believe our work helps to unravel the biomechanical role of the microfibril in the wood cell wall, and builds the theoretical foundation for tailoring the bio-inspired composites reinforced by functionally graded fibers.

Effects of co-fermentation on the release of ferulic acid and the rheological properties of whole wheat dough

In order to improve the poor rheological properties and stability of whole wheat dough (WWD) caused by bran, the co-fermentation technology by Lactobacillus plantarum LB-1 and yeast was used to release ferulic acid (FA) extensively in whole wheat flour and the effect of FA on the rheological qualities of WWD without fermentation was studied, aiming to improve the rheological properties of WWD with FA. The FA content, released extensively by the co-fermentation technology (1307.65 ± 10.26 μg/g), was significantly higher (P＜0.05) than the traditional yeast fermentation (548.51 ± 12.78 μg/g) due to the production of higher levels of cell wall degrading enzymes and organic acids, which could significantly improve the viscoelasticity of WWD. Meanwhile, the resistance to extension of WWDFY was 14.28% higher than that of WWDY, and the extensibility of WWDFY 9.68% better than that of WWDYL. And the WWDFY showed a better recovery stability, a higher hardness, larger elasticity and better water holding capacity compared to WWDY. The results indicated that FA could significantly modify the rheological properties of WWD, providing a theoretical basis for producing whole wheat products with desirable quality.

Importance of Cell Wall Permeability and Cell Wall Degrading Enzymes during Infection of Botrytis cinerea in Hazelnut

The Botrytis bunch mold, Botrytis cinerea pathogen is a necrotrophic ascomycete that infects hundreds of plant species, including hazelnut. B. cinerea produces toxins that induce cell wall degrading enzymes. In the current research work, we used eight hazelnut varieties and recorded their resistance levels in response to B. cinerea infection. Results showed that different varieties respond differently to B. cinerea infection. Disease index analysis revealed the resistance level of eight hazelnut varieties in the order of DW > OZ > L3 > PZ > XD1 > YZ > L1 > QX. Moreover, cell membrane permeability as well as the activities of cell wall degrading enzymes were measured. The increased level of cell wall degrading enzymes facilitates the fungal pathogens’ ability to colonize plants and cause infection. According to the results obtained through enzyme analysis, the hazelnut varieties L1 and QX, which were proved to be highly susceptible against B. cinerea, had the highest cell wall degrading enzyme production. DW and OZ, which were revealed to be resistant varieties through disease index data, also showed relatively lower activity of degrading enzymes as compared to other varieties. Our comparison analysis between the disease index and enzyme production confirms that disease occurrence and plant susceptibility strongly depend upon cell wall permeability. Our enzyme activity results validated the resistance order revealed by disease index assessment results (DW > OZ > L3 > PZ > XD1 > YZ > L1 > QX), and varieties DW and OZ were found to be the most resistant, while QX and L1 were found to be the most susceptible varieties against B. cinerea infection. Our study lays the foundation to further explore other factors involved in grey mold resistance in hazelnut.

Synchrotron X-ray measurements of cellulose in the cell wall of aged wood under uniaxial loading

Abstract The purpose of this study is to examine the effect of wood aging on the mechanical behavior at the cell-wall level. Synchrotron X-ray diffraction (XRD) measurements were performed to investigate the mechanical behavior of cellulose in the S2 layer of aged wood from a 250-year-old attic cabin beam. XRD measurements under uniaxial loading were performed on the cellulose (004) plane; the results were compared with those of recent wood. The cellulose in aged wood exhibited a delayed response to both tensile and compressive loading compared with recent wood. Under compressive loading, cellulose showed an increase in maximum strain and a significant increase in the variation of cellulose orientation angle, indicating that it may exhibit buckling-like meandering behavior. These results could be explained based on the decrease in hemicellulose content in the cell wall due to wood aging. In other words, the results suggested that an amorphous material in the cell wall affected the mechanical behavior of wood at the cell-wall level.

Viscoelastic behavior of softwood based on a multiscale computational homogenization

In the present study, a numerical multiscale model is made to show how the hierarchical structure of softwood affect its macroscopic viscoelastic properties. The performance of the model is demonstrated for two softwood species — Norway spruce and Japanese cypress, whose creep behavior has been characterized experimentally. The results show that by using the same transversely isotropic viscous properties of the cell wall for both species, it is possible to predict creep deformation relatively close to experimental creep measurements for both species. Assuming that the variability is larger on the microstructural level (density, cell-wall geometry, microfibril angle, composition of wood tissues) than on the cell-wall level, it is possible to predict the macroscopic creep behavior based on the microstructural parameters alone. Such predictions can potentially save cost and time, since creep characterization in all material directions is demanding.

The Struggle to End a Millennia-Long Pandemic: Novel Candidate and Repurposed Drugs for the Treatment of Tuberculosis.

This article provides an encompassing review of the current pipeline of putative and developed treatments for tuberculosis, including multidrug-resistant strains. The review has organized each compound according to its site of activity. To provide context, mention of drugs within current recommended treatment regimens is made, thereafter followed by discussion on recently developed and upcoming molecules at established and novel targets. The review is designed to provide a clinically applicable understanding of the compounds that are deemed most currently relevant, including those already under clinical study and those that have shown promising pre-clinical results. An extensive review of the efficacy and safety data for key contemporary drugs already incorporated into treatment regimens, such as bedaquiline, pretomanid, and linezolid, is provided. The three levels of the bacterial cell wall (mycolic acid, arabinogalactan, and peptidoglycan layers) are highlighted and important compounds designed to target each layer are delineated. Amongst others, the highly optimistic and potent anti-mycobacterial activity of agents such as BTZ-043, PBTZ 169, and OPC-167832 are emphasized. The evolving spectrum of oxazolidinones, such as sutezolid, delpazolid, and TBI-223, all aiming to exceed the efficacy achieved with linezolid yet offer a safer alternative to the potential toxicity, are reviewed. New and exciting prospective agents with novel mechanisms of impact against TB, including 3-aminomethyl benzoxaboroles and telacebec, are underscored. We describe new diaryloquinolines in development, striving to build on the immense success of bedaquiline. Finally, we discuss some of these compounds that have shown encouraging additive or synergistic benefit when used in combination, providing some promise for the future in treating this ancient scourge.

Are γ-terpinene, 1,8-cineole, p-coumaric acid, and quercetin active against wild-type and non-wild-type Sporothrix brasiliensis to itraconazole?

The emergence of itraconazole (ITZ)-resistant Sporothrix brasiliensis in feline and canine cases in southern Brazil has hampered the clinical cure of animal sporotrichosis, encouraging the search for therapeutic alternatives. The promising use of plants extracts from Lamiaceae family is known; however, there are no studies with its major compounds, as γ-terpinene (γTER), 1,8-cineole (1,8CIN), p-coumaric acid (pCOU), and quercetin (QUER). For the first time, we evaluated the antifungal, synergistic, cytotoxic activities and action mechanism of these compounds against S. brasiliensis. For this, 28 S. brasiliensis from cats (n = 24) and dogs (n = 4) and standard strains of S. brasiliensis and S. schenckii (n = 4) were tested by M38-A2 (CLSI), revealing non-wild-type (WT) isolates to ITZ on 54.2% (13/24) and 75% (03/04) of feline and canine isolates, respectively. Of the compounds, γTER stood out against all isolates (MIC/MFC 0.75 to > 3mg/ml; MIC50 3mg/ml). However, 1,8CIN, pCOU, and QUER showed little or no activity (MIC50 > 3mg/ml). Thus, γTER was selected for checkerboard assay, whose combination with ITZ showed synergistic (WT isolates) and indifferent (non-WT isolates) interaction. For action mechanism (sorbitol protection and ergosterol effect), γTER acted in membrane by complexing with fungal ergosterol and at the cell wall level, showing two possible pathways as antifungal target. Finally, cytotoxicity (MTT assay) showed that γTER was the safest compound on MDBK cells, even at a concentration of 3mg/ml (90.16%). Our findings support that γTER is a potent antifungal candidate for the control of sporotrichosis, including against non-WT S. brasiliensis.

Wood-Water Relations Affected by Anhydride and Formaldehyde Modification of Wood.

The moisture uptake of wood is influenced by accessible hydroxyl groups acting as sorption sites and the water-available cell wall space. To what extent do these mechanisms control the moisture uptake in wood needs to be addressed. For this purpose, we modified sorption site density and cell wall space by wood treatments with acetic anhydride or formaldehyde and investigated their effects on moisture uptake. Chemical changes at the cell wall level caused by the treatments were first determined by confocal Raman imaging. Following this, the deuterium exchange method was used to gravimetrically measure the hydroxyl accessibility, while the moisture uptake and the consequent swelling of the wood were determined by dynamic measurements of mass and dimensions within the hygroscopic range. The results showed that the effectiveness in reducing the moisture content of untreated wood across the hygroscopic range differed between the anhydride- and formaldehyde-modified wood. We also observed a poor correlation of accessible hydroxyl concentration in formaldehyde-modified wood with weight percentage gain and water uptake. Moreover, the dynamic mass and dimension analysis indicated that the reduction in swelling in formalized wood was affected by an unidentified mechanism in addition to reduced moisture content.