Thermal modification of wood causes chemical changes that significantly affect the physical, mechanical and biological properties of wood; thus, it is essential to investigate these changes for better utilization of products. Fourier transform infrared spectroscopy and size exclusion chromatography were used for evaluation of chemical changes at thermal treatment of oak wood. Thermal modification was applied according to Thermowood process at the temperatures of 160, 180 and 210 °C, respectively. The results showed that hemicelluloses are less thermally stable than cellulose. Chains of polysaccharides split to shorter ones leading to a decrease of the degree of polymerization and an increase of polydispersity. At the highest temperature of the treatment (210 °C), also crosslinking reactions take place. At lower temperatures degradation reactions of lignin predominate, higher temperatures cause mainly condensation reactions and a molecular weight increase. Chemical changes in main components of thermally modified wood mainly affect its mechanical properties, which should be considered into account especially when designing various timber constructions.

The effect of chemical treatment of hemp hurds slices in three solutions (EDTA (Ethylenediaminetetraacetic acid), NaOH and Ca(OH)₂) on the properties of natural material was discussed in this paper. Changes in the morphology, chemical composition and structure as well as thermal stability of hemp hurds before and after their modification were investigated by using FTIR (Fourier transform infrared spectroscopy), XRD (X-ray powder diffraction analysis) and TG (thermogravimetry)/DSC (differential scanning calorimetry). Size exclusion chromatography (SEC) measurements were used for determination of degree of cellulose polymerization of hemp hurd samples. Chemical modification is related to the partial removal of non-cellulosic components of lignin, hemicellulose and pectin as well as waxes from the surface of hemp hurd slices. Another effect of the chemical treatment applied is connected with increasing the crystallinity index of cellulose determined by FTIR and XRD methods. Decrease in degree of cellulose polymerization and polydispersity index in chemically modified hemp hurds compared to the original sample was observed. Increase in thermal stability of treated hemp hurd was found. The most significant changes were observed in alkaline treated hemp hurds by NaOH.

Nano-FTIR and PeakForce quantitative nanomechanical mapping (PF QNM) are new AFM-based techniques that can be applied to plant tissues to get high-resolution spatial distribution of features that are unavailable from bulk characterization. This can be useful for finding changes to plant cell walls by processing technologies, mutations, or the environment. Three poplar hardwoods of varying recalcitrance and composition (high lignin, low lignin, and mutant) were investigated by nano-FTIR and PF QNM. Bulk characterization was carried out by conventional FTIR and NMR of isolated cellulose, hemicelluloses, and lignin. We found that in nano-FTIR spectra of secondary cell walls (SCW) and compound middle lamella (CML), 1162 and 1269 cm^–1 could distinctly identify polysaccharides and lignin, respectively. Spatial variability in the content of polysaccharides and lignin was significantly larger in CML than SCW for all three poplars. Cellulose has a disordered structure in CML in comparison to SCW. PF QNM showed that SCW had a higher modulus of elasticity than CML due to the presence of crystalline cellulose in SCW. Differences in the physicochemical properties between the SCW and CML of plants can be probed at nanoscale by these techniques.

Several polysaccharides augment plant growth and productivity and galvanise defence against pathogens. Such elicitors have ecological superiority over traditional growth regulators, considering their amplified biocompatibility, biodegradability, bioactivity, non-toxicity, ubiquity, and inexpensiveness. Chitosan is a chitin-derived polysaccharide that has recently been spotlighted among plant scientists. Chitosan supports plant growth and development and protects against microbial entities such as fungi, bacteria, viruses, nematodes, and insects. In this review, we discuss the current knowledge of chitosan’s antimicrobial and insecticidal potential with recent updates. These effects are further explored with the possibilities of chitosan’s active correspondence with phytohormones such as jasmonic acid (JA), salicylic acid (SA), indole acetic acid (IAA), abscisic acid (ABA), and gibberellic acid (GA). The stress-induced redox shift in cellular organelles could be substantiated by the intricate participation of chitosan with reactive oxygen species (ROS) and antioxidant metabolism, including hydrogen peroxide (H₂O₂), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). Furthermore, we propose how chitosan could be intertwined with cellular signalling through Ca²⁺, ROS, nitric oxide (NO), transcription factors (TFs), and defensive gene activation.