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Shed new light on heartwood formation

Project Leader
Felhofer Martin, Project Leader
Duration:
01.08.2017-31.10.2020
Programme:
Doktorand(inn)enprogramm der ÖAW (DOC)
Type of Research
Basic Research

Further information: bionami.at

Staff
Gierlinger Notburga, Sub Projectleader
Felhofer Martin, Project Staff (bis 30.06.2022)
BOKU Research Units
Institute of Biophysik
Funded by
Österreichische Akademie der Wissenschaften, Dr. Ignaz- Seipel Platz, 1010 Wien, Austria
Abstract
Due to global warming an increase of average temperatures is expected, which will affect tree populations in Austrian forests. More drought resistant species such as oak and pine will adapt, which are known to accumulate higher contents of extractives in their inner “heartwood”. Some of these extractive components are known to enhance the trees natural durability by protecting against microbial attacks. Apart of the fact that heartwood is essential for a long-living tree, these more durable heartwoods are desired for construction applications and might give access to valuable add-on products in a biorefinery process. On the other hand in the paper and timber industry the presence of extractives is not always welcome as technical processes may be hindered and have to be adapted.
Heartwood formation has been studied since a long time. High variabilities among species, within single trees and under different environmental conditions have shown the complexity of this natural drying and impregnation process. Up to know, the chemical characterization has been mainly achieved by using different wet-chemical and chromatographic analysis. The context and relation to the wood microstructure is lost and often not all components are solved as changes in composition might need other treatment conditions and interactions with other cell wall polymers might occur. Still a knowledge gap exists on the distribution of these extractives on the micro- and nano scale and their interaction with other wood components. Are they mainly accumulated in the place of biosynthesis in the ray parenchyma cells or also transported to and impregnated in the fiber, tracheid and vessel cell walls? Is it a fast process or an ongoing slow polymerization process with changes in time and age?
With this project these knowledge gaps will be filled by investigating native never dried heartwood samples by state of the art microspectroscopic in-situ approaches. Fluorescence microscopy will give an overview of the distribution of the phenolic compounds and Raman microscopy deliver a more detailed picture on the chemical composition in context with the microstructure as well as TOF-SIMS microscopy. Co-located ESEM will elucidate the ultrastructure of the changing cell walls during heartwood formation. With these approaches the we will 1) monitor heartwood formation of pine, douglas fir and oak trees by following the extractives from biosynthesis to the cell wall impregnation, 2) Assess the interactions of the extractives with other cell wall components and 3) determine the role of drying during the formation of heartwood and for a kind of “self-sealing” effect observed in some preliminary experiments.
The results will reveal new insights into the biology of heartwood due to the detailed in-situ studies on the extractive distribution in context with the micro-and nanostructure as well as changes, solubilities and interactions. Furthermore in comparison to the natural dry falling of the tracheids the effects induced by artificial drying and thus important characteristics of wood as an industrial raw material will be derived. This will break new scientific grounds in the field of plant physiology (tree ageing), biomimetic plant protection mechanisms (decay resistance, “self-sealing”), but also regarding optimization of industrial applications and processes and the valorisation of add-on products in new biorefinery concepts.
Keywords
Materials physics; Microanalysis; Natural product chemistry; Botany; Wood research; Nanoanalytics; Wood industry; Renewable resources;
extractives; heartwood formation; microspectroscopy; Raman-Imaging; cell wall;
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