Our results indicate that the observed course of vascular bundles with fiber caps cannot only be a result of physiological need for water and nutrient supply but are interpreted in terms of mechanical constraints acting on the branching region. In addition, the used 3D cine technique and coupled 3D reconstruction provide a valuable tool for botanists working in the field of anatomy.

The branching of arborescent (tree‐like) monocotyledonous plants of the genus Dracaena or of columnar cacti differ considerably from that observed in other dicotyledonous or gymnosperm trees. The investigated ramifications exhibit distinctive morphological and anatomical features. In arborescent monocotyledons the side branches are attached to the main stem by a fiber‐reinforced tissue newly formed during secondary growth, clasping the main stem and finally resulting in a “flange‐mounted” structure. In the case of columnar cacti the most obvious feature is the pronounced constriction at the attachment point of the branches that is also mirrored in the lignified vascular tissue. One might argue that these characteristic morphological and anatomical features in regions exposed to high mechanical stresses represent structural weaknesses. However, the outer shape and the inner structures of the ramifications cause considerable stability and structural integrity of the stem‐branch connection under static and dynamic loading. Our results allow concluding that load‐adaptation in ramified plant structures is a result of a combination of optimization in outer shape and fiber arrangement within the ramifications. Numerical methods simulating the mechanical behavior based on data obtained from the studied plants support this assumption. A deeper understanding of the outer shape of the connection between shoot and branch as well as of the arrangement of the lignified vascular tissues in the branching region, may contribute toward alternative concepts for branched technical light‐weight‐structures. In particular for braided fiber‐reinforced composites this biomimetic approach might help to keep the demand on the available design space as small as possible.

We investigated the different processes involved in spore liberation in the polypod fern Adiantum peruvianum (Pteridaceae). Sporangia are being produced on the undersides of so-called false indusia, which are situated at the abaxial surface of the pinnule margins, and become exposed by a desiccation-induced movement of these pinnule flaps. The complex folding kinematics and functional morphology of false indusia are being described, and we discuss scenarios of movement initiation and passive hydraulic actuation of these structures. High-speed cinematography allowed for analyses of fast sporangium motion and for tracking ejected spores. Separation and liberation of spores from the sporangia are induced by relaxation of the annulus (the ‘throwing arm’ of the sporangium catapult) and conservation of momentum generated during this process, which leads to sporangium bouncing. The ultra-lightweight spores travel through air with a maximum velocity of ~5 m s-1, and a launch acceleration of ~6300g is measured. In some cases, the whole sporangium, or parts of it, together with contained spores break away from the false indusium and are shed as a whole. Also, spores can stick together and form spore clumps. Both findings are discussed in the context of wind dispersal.

The junctions between stems and branches in arborescent monocotyledons and columnar cacti are structurally and functionally poorly understood to date. Therefore, the functional anatomy and morphology of these junctions as well as the arrangement and biomechanics of mechanically relevant tissues were investigated. Both plant groups share distinctive anatomical features. Due to restricted secondary growth, newly formed tissues connecting stem and branch clasp around the main shoot, resulting in a “flange-mounted” structure. In addition, an indentation or a distinct necking forming a specific shape characterizes the area of attachment. As a result, the distribution of mechanical stresses is modified by increasing the resistance against high stresses upon static and presumably also upon dynamic loading. The mechanically important fibrous bundles or wood lamellae are collinearly aligned with the occurring stresses leading to a lateral shift of the stress trajectories and a shape adjustment. This particular branching type shows a remarkable potential to improve joints in braided fiber-reinforced composites. In the near future, a fully automated fabrication of biomimetic branched composites will be possible. First promising demonstrators have already been produced on lab scale.

The manufacturing of nodal elements and/or ramifications with an optimised force flow is one of the major challenges in many areas of fibre-reinforced composite technology. Examples are hubs of wind-power plants, branching points of framework constructions in the building industry, aerospace, ramified vein prostheses in medical technology and the connecting nodes of axel carriers. Addressing this problem requires the adaptation of innovative manufacturing techniques and the implementation of novel mechanically optimised fibrereinforced structures. Consequently, the potential of hierarchically structured plant ramifications as concept generators for innovative, biomimetic branched fibre-reinforced composites was assessed by morphological and biomechanical analyses. Promising biological models were found in monocotyledons with anomalous secondary growth, i.e. Dracaena and Freycinetia, as well as in columnar cacti, such as Oreocereus and Corryocactus. These plants possess ramifications with a pronounced fibre matrix structure and a special hierarchical stem organization, which markedly differ from that of other woody plants by consisting of isolated fibres and/or wood strands running in a partially lignified parenchymatous matrix. The angles of the Y-and T-shaped ramifications in plants resemble those of the branched technical structures. Our preliminary investigations confirm that the ramifications possess mechanical properties that are promising for technical applications, such as a benign fracture behaviour, a good oscillation damping caused by high energy dissipation, and a high potential for lightweight construction. The results demonstrate the high potential for a successful technical transfer and will lead to the development of concepts for producing demonstrators in the lab-bench and pilot plant scales that already incorporate solutions inspired by nature.