Chemical characterization of cork, phloem and wood from different Quercus suber provenances and trees

Abstract

Sustainability of cork oak (Quercus suber) forests is threatened by biotic and abiotic factors and characterization of potentially differing genetic resources has therefore gained importance. This work addresses the chemical variation of the three tissues of cork oak stems – cork, phloem and wood – in relation to tree and provenance, looking for genetic chemical diversity and for physiological derived differences. The three tissues differ with cork clearly differentiating regarding summative composition, component ratios and monomeric composition. Cork is the only tissue where suberin is present (42.3% o.d. mass) as the main cell wall component, and it has a high content of extractives (11.7%) with significant proportion of lipophilic compounds. Phloem is more lignified than wood (38.0% vs. 23.4%) and has less polysaccharides (49.1% vs. 64.6%) with glucose-to-other sugars relation of 1:1.3 in phloem and 1:0.7 in wood. Analytical pyrolysis showed that lignification is a heterogeneous process and the lignin monomeric composition depends on tissue and cell type: cork lignin has a H:G:S ratio of 1:2.5:0.3 and S/G ratio of 0.12, while phloem and wood lignins have mainly G and S units with a S/G ratio of respectively 1.1 and 2.3. No significant differences were found between the three provenances, but some chemical variation occurred between the trees within a provenance. NIR spectroscopy and principal component analysis differentiated cork, phloem and wood, while the dispersion within each group highlighted the significant tree variability, while provenances were a non-significant factor of chemical variation.

Microbiome Associated with the Mycangia of Female and Male Adults of the Ambrosia Beetle Platypus cylindrus Fab. (Coleoptera: Curculionidae)

“…The last two are lignocellulosic tissues with moderate content of extractives. Moreover, wood has the highest content of polysaccharides [54]. In our study, we observed a pattern in the distribution of specific bacteria in male mycangia of P. cylindrus, according to the different wood material of the gallery's parts built by the insects (Figure 6).…”

Cork and Cork Stoppers: Quality and Performance

“…Lignin is an aromatic cross-linked polymer that represents on average 22% of the cork dry mass and is responsible for the structural rigidity of the cells and their resistance to compression [29]. Cork lignin is mostly constituted of G units (guaiacyl units) with an important proportion of H units (hydroxyphenyl units) and minor contents of S units (syringyl units) (H:G:S 1:2.5:0.3, S/G 0.12) [31].…”

“…The cellulose and hemicelluloses are less representative and amount up to 16.2% of the cell wall structural components [31]. Hemicelluloses are mainly composed of arabinoxylans with a significant proportion of galactose including uronic acids.…”

“…Hemicelluloses are mainly composed of arabinoxylans with a significant proportion of galactose including uronic acids. The suberin-to-lignin ratio is 2.0, and the cellulose-to-hemicellulose ratio, determined by the ratio of glucose to other sugars, is 1:1.2 [27,29,31].…”

Cork Oak Endophytic Fungi as Potential Biocontrol Agents against Biscogniauxia mediterranea and Diplodia corticola

“…The synthesis of cork, a homogeneous tissue of phellem cells, depends on the activity of the cork cambium, which covers the trunk and branches of cork oak. Due to the interesting and unique set of physical, biological and chemical properties, such as sealing and insulating features, cork is mainly used for the production of bottle stoppers [ 3 ]. Every year, 80% of worldwide produced cork comes from the Iberian Peninsula, in which Portugal is responsible for almost half of the total global production [ 2 , 4 ].…”