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•Chemical heterogeneity is a common challenge in the application of biomaterials such as wood.•Chemical imaging methods unravel spatial heterogeneity in wood on different length ...scales.•These methods can quantify the chemical distribution in treated wood on macroscopic and cellular levels.•Combining imaging methods provides a holistic insight into structure–property relations of biomaterials.
An inhomogeneous chemical distribution can be problematic in many biomaterial applications, including wood impregnation. Since wood is a hierarchically structured material, the chemical distribution must be considered on different length scales. Here, a combination of imaging methods revealed the distribution of phenol–formaldehyde resin in impregnation-treated European beech wood within the scale of several millimeters or larger (macroscopic) and the micron scale (cellular level). The macroscopic resin distribution was quantified by hyperspectral near-infrared (NIR) image regression. A partial least square regression model accurately predicted the resin content in the range of 0–30 % with average prediction errors of ≤0.93 % for calibration and the test set. The cellular resin distribution was investigated by mapping the UV absorbance in selected regions of interest at high lateral resolution using UV microspectrophotometry (UMSP). The application of both imaging techniques to board sections revealed a process-dependent resin distribution. NIR image regression quantified the drying-induced migration of resin toward the board surfaces. UMSP measurements in selected regions revealed that this resin migration also affected the resin distribution across cell walls. Overall, the results demonstrate the potential of combining chemical imaging techniques to quantify process-dependent heterogeneity and to develop efficient treatments for wood and other biomaterials.
Currently, there is an increasing interest in Mexico to grow teak in large-scale plantations. Teak is recognized for its natural durability combined with high mechanical strength. The present study ...aims at determining the quantitative and qualitative properties of teak wood for several age classes and provenances, originating mainly from three localities of south eastern Mexico, while the focus was on the extractives and the natural durability of teak samples. The percentage of heartwood (hW) formed by the plantation trees was within the range reported elsewhere for the corresponding age classes, while the hW% was in relation with the tree height and age. Further trends observed were: lower topo-chemical absorbance that was measured by ultraviolet microspectrophotometry (UMSP) of the inner hW compared to the outer hW; no clear correlation between the age and origin and the extractives’ composition accumulated in the hW; abundant presence of tectoquinone irrespective of the age and provenance; and finally, high resistance against white rot (WR) and brown rot (BR) fungi regardless of the age or provenance.
• Background and Aims The effect of heating and cooling on cambial activity and cell differentiation in part of the stem of Norway spruce (Picea abies) was investigated. • Methods A heating ...experiment (23–25 °C) was carried out in spring, before normal reactivation of the cambium, and cooling (9–11 °C) at the height of cambial activity in summer. The cambium, xylem and phloem were investigated by means of light- and transmission electron microscopy and UV-microspectrophotometry in tissues sampled from living trees. • Key Results Localized heating for 10 d initiated cambial divisions on the phloem side and after 20 d also on the xylem side. In a control tree, regular cambial activity started after 30 d. In the heat-treated sample, up to 15 earlywood cells undergoing differentiation were found to be present. The response of the cambium to stem cooling was less pronounced, and no anatomical differences were detected between the control and cool-treated samples after 10 or 20 d. After 30 d, latewood started to form in the sample exposed to cooling. In addition, almost no radially expanding tracheids were observed and the cambium consisted of only five layers of cells. Low temperatures reduced cambial activity, as indicated by the decreased proportion of latewood. On the phloem side, no alterations were observed among cool-treated and non-treated samples. • Conclusions Heating and cooling can influence cambial activity and cell differentiation in Norway spruce. However, at the ultrastructural and topochemical levels, no changes were observed in the pattern of secondary cell-wall formation and lignification or in lignin structure, respectively.
The aim of this study was to visualize non-enzymatic oxidative degradation damages in the initial decay stage of the brown rot fungus Rhodonia placenta degradation in furfuryl alcohol (FA) modified ...wood cell walls and untreated wood cell walls of radiata pine (Pinus radiata) sapwood. A decay test with small wood blocks (1.5 × 1.5 × 5 mm³) of untreated and furfurylated radiata pine selected from two different furfurylation processes was performed until the first mass loss occurred. The samples were exposed to the brown rot fungus R. placenta, monitored by light microscopy and analyzed topochemically by cellular UV microspectrophotometry (UMSP). The results showed that the FA modification process directly influenced: i) the fungal colonization and hyphal growth, ii) the spectral UV behavior, and iii) degradation patterns of the entire cell wall layers. For the first time, UMSP area scans and selective line scans of individual cell wall regions provide topochemical insights into oxidative degradation at the initial decay stage of furfuryl alcohol-modified P. radiata visualizing oxidative degradation in situ. Knowledge of the initial decay stage of brown rot degradation in FA-modified wood compared to untreated wood extends our understanding of the brown rot decay processes of cell wall compounds.
•Initial brown rot decay in untreated and furfuryl alcohol modified radiata pine.•Light microscopy studies of hyphal colonization in modified and untreated wood.•Cellular UV microspectrophotometry (UMSP) monitoring over 18 days.•Topochemical insights into individual cell wall layers at the initial decay phase.•Visualization of non-enzymatic oxidative degradation pattern insitu.
Cedrelinga cateniformis (tornillo) is a timber species of the South American Amazon Basin. In its natural distribution area, the wood has various local uses, such as furniture, art work, door and ...window frames, and light construction. In order to promote this lesser known species for high valued applications on the international market, wood anatomical, topochemical and physical/mechanical studies were carried out to characterize the wood properties. The topochemical distribution of the lignin and phenolic extractives in the tissue were studied by means of cellular UV microspectrophotometry (UMSP). The results of the structural and topochemical analyses were compared with the interrelation of certain anatomical and subcellular structures as well as the chemical composition with regard to the physical and mechanical properties. The natural durability of the mature heartwood was analyzed according to the European Standards and is resulting in a durability class 1 against basidiomycetes. Based on the findings of the comprehensive investigations concerning physical and biological features, e.g. the dimensional stability and durability, Cedrelinga cateniformis is ideally suited as a substitute for overexploited tropical woods currently used in Europe for wooden window frames and other above ground outdoor applications and thus can contribute to increase the value-added production in Peruvian forests.
Abstract To broaden the knowledge about the chemical changes at the cell wall level of differently modified tropical hardwoods, heat-treated and N-methylol melamine (NMM)-treated samples of koto ( ...Pterygota macrocarpa ) and limba ( Terminalia superba ) were prepared. UV microspectrophotometry (UMSP) was applied at 278 and 240 nm as specific wavelengths to analyze chemical alterations of the samples caused by heat and NMM treatment, respectively. The absorbance of koto exceeded that of limba before and after treatment, potentially due to the higher extractive content of the former. Regardless of the wood species, the absorbance of the samples increased with increasing intensity of the NMM treatment. Additionally, the absorbance of lignin within the spectrum of 230–350 nm was altered due to the NMM treatment. The functionality of applying specific wavelengths for the analysis of different modification methods of wood was proven. However, the comparison with literature did not show differences in the absorbance, which could be assigned to the characteristics of tropical hardwoods.
Archaeological wood of 13 excavated oak piles from five historical bridge generations in Bavaria, dated from 1447 to 1787, was investigated by means of light microscopy (LM) and cellular ...UV-microspectrophotometry (UMSP) to study the ageing and natural resistance of the excavated wood. Furthermore, the mineral content of the ancient wood was determined to evaluate the impact of mineral inclusions on microbial resistance, tested using a mini block fungal test. The LM and UMSP analyses revealed well preserved cell wall structures and no significant modification of the lignin composition and distribution in predominant parts of the piles. Slight microbial decay caused by soft rot and erosion bacteria was only detectable at the outermost millimetres of individual piles. The fungal mini block tests yielded mass losses of ancient oak samples between 15% and 30%, independent of their analysed mineral content. The results provided evidence that the fungal resistance of the investigated ancient wood is mainly determined from the special soil with its high mineral content.
The topochemical distribution of lignin in vascular bundles separated from different radial positions of Mexican coconut wood stems (
) has been studied with focus on the relationship between the ...degree of lignification and tensile strength properties. The cellular lignin distribution was analyzed by UV-microspectrophotometry (UMSP) scanning at 280 nm of sections of vascular bundles (VBs) of 1 μm thickness. The fibers of the VBs with high tensile strength reveal a relatively low UV-absorbance at 280 nm (A
0.39), whereas the VBs with low tensile strength display the highest A
(0.59). The S
of fiber walls are characterized by the typical lamellar structure with increasing lignin contents from the cell lumen towards the compound middle lamellae (CML). The A
data of CMLs are higher (0.67 to 0.87) than those of the S
wall layers. Overall, the A
values of S
of fibers walls within single VBs of coconut are in the range of 0.36 to 0.59.
Thermal modification (TM) of wood has occupied a relatively narrow but stable niche as an alternative for chemical wood protection. There are different technological solutions for TM and not all ...details of their effects on wood tissue have been understood. The one-stage hydrothermal modification (HTM) at elevated vapour pressure essentially changes the wood’s composition and structure. In the present paper, the changes in three hardwood lignins (alder, aspen, and birch) were observed within the cell wall by means of cellular UV microspectrophotometry. The lignin absorbances in the compound middle lamella (CML) of unmodified wood are 1.7- to 2.0-fold higher than those in the fibre S2 layer. The woods were modified in the temperature range from 140 to 180°C, while in the lower temperature range (140°C/1 h), the UV absorbances are little affected. Essential changes occur in the range of 160–180°C and the UV data reflect these by absorbtion changes, while the absorbances at 278 nm rise with factors around 2 more in the S2 layer than in the CML. The absorbance increments are interpreted as polycondensation reactions with furfural and other degradation products of hemicelluloses with the lignin moiety of the cell wall.
In addition to lignin, grass cell walls are characterized by the presence of hydroxycinnamic acids that play a significant role in cross-linking polymers into a cohesive network, and pretreatments ...are required to overcome the recalcitrance of lignocelluloses prior to enzymatic bioconversion of polysaccharides. The effects of dilute acid and ammonium hydroxide pretreatments were studied on the chemical composition and enzymatic saccharification of
Miscanthus
internodes fragments. The hydroxycinnamic acid content was reduced after both pretreatments, while lignin got enriched in condensed linked structures. In addition, dilute acid pretreatment was effective in decreasing xylan content of
Miscanthus
, while ammonia treatment induced a marked swelling effect on the cell walls of parenchyma, vascular sclerenchyma, and epidermal sclerenchyma. The phenol distribution at the cell level was estimated using UV transmission microspectrophotometry. Internode cell walls displayed different UV spectra according to the cell type. However, the secondary cell walls had similar UV spectra after pretreatment, whereas spectra recorded at the cell corner region displayed variations according to cell type and pretreatment. Acid pretreatment was more efficient than ammonia to improve the conversion of polysaccharides by a
Trichoderma
cellulolytic cocktail. Although pretreatments achieved moderate saccharification yields, the secondary cell walls were altered at some pit regions of the vascular sclerenchyma whereas parenchyma appeared recalcitrant. Variations in the UV spectra of enzyme-digested cell walls suggest pretreatment-dependent heterogeneity of the phenolic distribution in the more recalcitrant cell walls.
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