The cell walls in plant tissues are made up of just four basic building blocks: cellulose, the main structural fiber of the plant kingdom, hemicellulose, lignin and pectin. Although the microstructure of plant cell walls varies in different types of plants, broadly speaking, cellulose fibers reinforce a matrix of hemicellulose and either pectin or lignin. The cellular structure of plants varies from the honeycomb-like cells of wood to the closed-cell, liquid-filled foam-like parenchyma cells of apples and potatoes. The arrangement of the four basic building blocks plant cell walls and the variations in cellular structure give rise to a remarkably wide range of mechanical properties: the Young’s moduli span 4 orders of magnitude while the compressive strengths span nearly 3 orders of magnitude. Here, we review the microstructure of both the cell wall and the cellular structure in four plant materials (wood, arborescent palm stems, bamboo and parenchyma) to explain the wide range in mechanical properties in plants..
Professor Lorna Gibson graduated in Civil Engineering from the University of Toronto and obtained her Ph.D. from the University of Cambridge. She was an Assistant Professor in Civil Engineering at the University of British Columbia for two years before moving to MIT where she is currently the Matoula S. Salapatas Professor of Materials Science and Engineering. Her research interests focus on the mechanics of materials with a cellular structure such as engineering honeycombs and foams, natural materials such as wood, palm and bamboo and medical materials such as trabecular bone and tissue engineering scaffolds. She is the co-author of Cellular Solids: Structure and Properties (with MF Ashby) and of Cellular Materials in Nature and Medicine (with MF Ashby and BA Harley). Recent projects include balsa as a model for bioinspired design of engineering materials; structural bamboo products, analogous to wood products such as oriented strandboard; and aerogels for thermal insulation. She teaches two subjects: Mechanical Behavior of Materials (also offered online through MITx as 3.032x) and Cellular Solids: Structure, Properties and Applications). She was recently named a MacVicar Faculty Fellow, MIT's top award for undergraduate teaching. She has served as Chair of the Faculty and Associate Provost at MIT.