Meeting Abstract
S7.3 Tuesday, Jan. 6 The Plant Cell Wall Acts as a Sophisticated Mechanical Device BURGERT, I*; FRATZL, P; Max-Planck-Institute of Colloids and Interfaces, Potsdam, Germany; Max-Planck-Institute of Colloids and Interfaces, Potsdam, Germany ingo.burgert@mpikg.mpg.de
Plants are hierarchically organised and possess remarkable mechanical properties. The unique performance of plant biomaterials is based on sustained optimization processes of the organism, which become obvious in the shape of the organs and in the adapted molecular structure. Depending on tissue function, plant cells are formed in various ways with respect to shape, thickness and arrangement of cell wall layers, orientation of the cellulose microfibrils as well as chemical composition. At the molecular level cell walls consist of a few nanometer thick semi-crystalline cellulose fibrils embedded in amorphous matrix polymers such as hemicelluloses, pectins or lignin. The orientation of the parallel cellulose microfibrils in the cell wall, known as microfibril angle (MFA) is one of the main parameter to adjust their mechanical properties. The talk will focus on the mechanical performance of plant cell walls and their stress generation capacities which allow the actuation of organ movement. Particular attention will be paid to organ movements due to moisture changes in cell walls which do not require any metabolism and are controlled by the architecture of the cell walls by means of the orientation of stiff cellulose fibrils embedded in swellable matrix polymers. This general principle by which active gels can be directed in their swelling behaviour by stiff fibres distributed in a suitable way makes humidity-based actuation systems in plants particularly interesting for biomimetic materials research. Recent findings on the stress generation in tension wood (hardwoods) and compression wood (softwoods) which enable trees to orient leaning stems and branches, and the bending movement of wheat awns which provide motility to the seed in a daily cycle are presented.
