Short Poster Lecture
Efficient seed dispersal simultaneously enables plants to colonize new habitats while ensuring optimal growth conditions and excluding competition with the mother plant for nutrients and light. Various different mechanisms have evolved to guarantee efficient and successful seed dispersal in plants. The distribution of the seeds of wild oat (Avena sterilis) rely on humidity-driven twisting and bending of the awns. The awns constitute a propagation apparatus for the seeds to move along the ground and eventually to pierce the topsoil. The aim of this study is to characterize the composition, microstructure, and architecture of the awns. We seek to identify structural principles on several hierarchical levels that induce the movement. This is addressed by polarized light microscopy (PolScope), light and fluorescence microscopy coupled with the application of diverse histochemical stains, and by scanning electron microscopy (SEM). We further isolate tissue pieces and single cells and follow their hygroscopic movement. Preliminary results show that the awn is constituted of two concentric cell layers. The outer layer is moderately lignified and pectinized. The cell walls are built of cells of cellulose microfibrils oriented at a relatively large angle in relation to the cell's long axis. In contrast, the central layer contains heavily lignin modifications, lower level of pectin, and a lower cellulose microfibril angle. The specific organization of these layers generate a combined movement, exerting the twisting of the awn as a unit. Future experiments will aim to imitate structures studied by incorporating cellulose nanostructures into hydrogels. We will thus artificially transfer the movement mechanism from the single cell level to a macroscopic scale.