This week’s leafis going to be more about bark than the dogwood (Cornus spp., Cornaceae), but I couldn’t resist the title and am delighted with the stunning graphic from @Lidan Beck.
Tree trunks broaden by lateral cell division in two rings of “cambium”. Vascular cambium provides the vessels that connect the photosynthetically-active leaves with the roots. The cells towards the inside form water-conducting xylem cells that are fortified by lignin polymerised from phenolic acids. These cells quickly lose metabolic function but continue to conduct water. The oldest, innermost cells may eventually disintegrate completely causing hollowing of the trunk.
Immediate outside the vascular cambium is the phloem, providing vessels that transport metabolites between leaves and roots. Phloem is the innermost layer of tree bark. It issurrounded by metabolically-active, phytochemical-rich cortex. In young stems, the outermost layer is epidermis. In trees this is replaced by “periderm”, layers of cork produced by another ring of dividing cells, the cork cambium that produces the co Like most cells in the tree trunk, the cork is fortified with lignin, but its most distinctive component is called suberin, a natural polyester of long-chain fatty acids (suberin acids) and glycerol. Suberin seals the tree trunk against water loss and protects against microbes and insects.
Besides providing metabolic precursors for lignin and suberin, tree bark cortex is a rich source of medicinal compounds. For dogwood specifically, the bark is rich in phytochemicals and the tree may have got its name from its use to treat dog mange. In addition, extracts of dogwood fruit might help reduce skin irritation.
Nevertheless, one of best uses humans have found for tree bark is as a natural gas-impervious, waterproof sealant, and the best tree for this is not the dogwood but Quercus suber, the cork oak.
Cheers!
References
𓃡 Begley, E. (2015). Bark: From abstract art to aspirin. Arnoldia, 72(3),2-13. https://arboretum.harvard.edu/stories/bark-from-abstract-art-to-aspirin/
𓃡Graça J. (2015). Suberin: the biopolyester at the frontier of plants. Frontiers in chemistry, 3, 62. https://doi.org/10.3389/fchem.2015.00062
𓃡 KhanA et al (2022). Phytochemical Profiling, Anti-Inflammatory, Anti-Oxidant and In-Silico Approach of Cornus macrophylla Bioss (Bark). Molecules(Basel, Switzerland), 27(13), 4081. https://doi.org/10.3390/molecules27134081
𓃡 Hydrophilic Dogwood Extracts as Materials for Reducing the Skin Irritation Potential of Body Wash Cosmetics. Molecules (Basel, Switzerland), 22(2), 320. https://doi.org/10.3390/molecules22020320
