Unlocking the secrets of plant cell walls

Fanny Trifilieff: Why study wood in particular?

Aude Lereu: The wood industry is a sustainable development issue that meets the needs of many traditional industrial sectors such as construction, the paper industry and heating, as well as more recent sectors such as the extraction of biofuels and the manufacture of biodegradable, environmentally-friendly bioplastics. Wood remains a renewable source as long as it is harvested in a sustainable manner. One of the wood industry's major preoccupations is therefore to study and better understand wood's mechanisms in order to exploit them more effectively. Access to cell walls, at the nanometer scale, reveals the chemical and physical properties of wood, and thus enables us to better understand its mechanisms. This is where we come in, using our expertise in nanoscience and nanotechnology.

F.T: What technique was used to analyze plant cell walls?

A.L: We used a technique known as "near-field optical microscopy", based on the interaction of the cell wall with a nanometric tip brought close to the sample. Light is then directed onto the tip-wall assembly. It is absorbed differently by the layers of the plant wall, depending on their chemical composition. In addition to absorption, we can also measure the proportion of reflected light. Access to these two parameters enables us to trace optical dielectric constants at wall level non-destructively and in situ, i.e. without touching the wood's internal structure. This technique makes it possible to simultaneously measure the sample's topography, chemical composition, optical properties and some of its mechanical properties at the nanometer scale.

F.T: What prospects do these results offer the wood industry?

A.L: In plant engineering, we use chemical or physical processes to modify wood during its growth in order to give it specific properties. A great deal of research is underway to observe and better understand these modifications to the cell wall, so that we can take advantage of them. Using the technique employed here, we were able for the first time to assess the local internal optical properties of the plant cell wall, while taking into account the impact of structure and chemical properties. Our results were obtained from poplar samples, but can be applied to all types of plant materials or biomaterials. They offer perspectives towards plant engineering with the development and use of new (meta-)materials of plant origin.