Tom Masselter

Ultra-fast underwater suction traps

Carnivorous aquatic Utricularia species catch small prey animals using millimetre-sized underwater suction traps, which have fascinated scientists since Darwins early work on carnivorous plants. Suction takes place after mechanical triggering and is owing to a release of stored elastic energy in the trap body accompanied by a very fast opening and closing of a trapdoor, which otherwise closes the trap entrance watertight. The exceptional trapping speed—far above human visual perception—impeded profound investigations until now. Using high-speed video imaging and special microscopy techniques, we obtained fully time-resolved recordings of the door movement. We found that this unique trapping mechanism conducts suction in less than a millisecond and therefore ranks among the fastest plant movements known. Fluid acceleration reaches very high values, leaving little chance for prey animals to escape. We discovered that the door deformation is morphologically predetermined, and actually performs a buckling/unbuckling process, including a complete trapdoor curvature inversion. This process, which we predict using dynamical simulations and simple theoretical models, is highly reproducible: the traps are autonomously repetitive as they fire spontaneously after 5–20 h and reset actively to their ready-to-catch condition.

Flectofin: a hingeless flapping mechanism inspired by nature

This paper presents a novel biomimetic approach to the kinematics of deployable systems for architectural purposes. Elastic deformation of the entire structure replaces the need for local hinges. This change becomes possible by using fibre-reinforced polymers (FRP) such as glass fibre reinforced polymer (GFRP) that can combine high tensile strength with low bending stiffness, thus offering a large range of calibrated elastic deformations. The employment of elasticity within a structure facilitates not only the generation of complex geometries, but also takes the design space a step further by creating elastic kinetic structures, here referred to as pliable structures. In this paper, the authors give an insight into the abstraction strategies used to derive elastic kinetics from plants, which show a clear interrelation of form, actuation and kinematics. Thereby, the focus will be on form-finding and simulation methods which have been adopted to generate a biomimetic principle which is patented under the name Flectofin®. This bio inspired hingeless flapping device is inspired by the valvular pollination mechanism that was derived and abstracted from the kinematics found in the Bird-Of-Paradise flower (Strelitzia reginae, Strelitziaceae).

Faster than their prey: new insights into the rapid movements of active carnivorous plants traps.

Plants move in very different ways and for different reasons, but some active carnivorous plants perform extraordinary motion: Their snap-, catapult- and suction traps perform very fast and spectacular motions to catch their prey after receiving mechanical stimuli. Numerous investigations have led to deeper insights into the physiology and biomechanics of these trapping devices, but they are far from being fully understood. We review concisely how plant movements are classified and how they follow principles that bring together speed, actuation and architecture of the moving organ. In particular, we describe and discuss how carnivorous plants manage to execute fast motion. We address open questions and assess the prospects for future studies investigating potential universal mechanisms that could be the basis of key characteristic features in plant movement such as stimulus transduction, post-stimulatory mechanical answers, and organ formation.

Catapulting Tentacles in a Sticky Carnivorous Plant

Among trapping mechanisms in carnivorous plants, those termed ‘active’ have especially fascinated scientists since Charles Darwin’s early works because trap movements are involved. Fast snap-trapping and suction of prey are two of the most spectacular examples for how these plants actively catch animals, mainly arthropods, for a substantial nutrient supply. We show that Drosera glanduligera, a sundew from southern Australia, features a sophisticated catapult mechanism: Prey animals walking near the edge of the sundew trigger a touch-sensitive snap-tentacle, which swiftly catapults them onto adjacent sticky glue-tentacles; the insects are then slowly drawn within the concave trap leaf by sticky tentacles. This is the first detailed documentation and analysis of such catapult-flypaper traps in action and highlights a unique and surprisingly complex mechanical adaptation to carnivory.

Biomechanical Reconstruction of the Carboniferous Seed Fern Lyginopteris oldhamia: Implications for Growth Form Reconstruction and Habit

The mechanical architecture of the Carboniferous seed fern Lyginopteris oldhamia is investigated from development stages including naturally decorticated stems. The growth form shows a relatively long semi‐self‐supporting phase of growth, with prolonged retention of the primary outer “dictyoxylon” cortex contributing significantly during early and mature growth. The outer cortex is retained on the stem despite significant secondary vascular growth via radial and tangential expansion and proliferation of interstitial parenchyma and longitudinal division of the radial bands of fibers. In the final stages of development, the outer “mechanical dictyoxylon” cortex is sloughed from the stem after periderm development in the inner cortex. Loss of the outer cortex results in a decrease in calculated bending stiffness. Calculations of mechanical stem properties based on the overall development indicate for a climber a comparatively stiff mechanical architecture that is comparable with certain types of extant lianas. Mechanisms that allow L. oldhamia to retain and then shed the outer cortex show developmental and mechanical strategies analogous to those of extant climbing plants. The study indicates that relatively sophisticated climbing stem architectures had already evolved by the Late Carboniferous.

Functional morphology and biomechanics of branch -stem junctions in columnar cacti

Branching in columnar cacti features morphological and anatomical characteristics specific to the subfamily Cactoideae. The most conspicuous features are the pronounced constrictions at the branch–stem junctions, which are also present in the lignified vascular structures within the succulent cortex. Based on finite-element analyses of ramification models, we demonstrate that these indentations in the region of high flexural and torsional stresses are not regions of structural weakness (e.g. allowing vegetative propagation). On the contrary, they can be regarded as anatomical adaptations to increase the stability by fine-tuning the stress state and stress directions in the junction along prevalent fibre directions. Biomimetic adaptations improving the functionality of ramifications in technical components, inspired, in particular, by the fine-tuned geometrical shape and arrangement of lignified strengthening tissues of biological role models, might contribute to the development of alternative concepts for branched fibre-reinforced composite structures within a limited design space.

Ontogenetic Reconstruction of the Carboniferous Seed Plant Lyginopteris oldhamia

Two developmental trajectories are hypothesized for growth of the aerial stem and branch system in Lyginopteris oldhamia. They include (1) a determinate single‐phase model, where the primary body decreases in size along the main stem or branches toward the apex, and (2) a less determinate two‐ or three‐phase model, where the primary body of stems and branches increases in size (epidogenesis), possibly maintaining a relatively constant maximal size (menetogenesis), and then diminishes in size (apoxogenesis) toward the apex. Developmental patterns of primary tissues (pith, primary xylem, inner and outer cortex) and secondary tissues (periderm and products of the bifacial vascular cambium, including wood and secondary phloem) are investigated within the context of each model. Primary tissues of inner and outer cortex as well as peridermal tissue initiated in the mid inner cortex show significant changes in response to growth of the bifacial vascular cambium. Patterns of development in both primary and secondary tissues indicate an overall development more consistent with epidogenetic, menetogenetic, and apoxogenetic phases of development. Evidence of epidogenesis is indicated by the presence of small primary bodies with (1) high levels of vascular cambial development and periderm and (2) high levels of compensatory enlargement of the outer primary cortex via tangential and radial deformation in addition to cellular proliferation. Following expansion of the wood cylinder, the outer primary cortex shows extended structural integrity and possible “self‐repair” during extreme straining of the outer cortex. Final development involves sloughing of the entire primary cortex and establishment of an entire layer of periderm enclosing the secondary phloem and wood.

Fastest predators in the plant kingdom: functional morphology and biomechanics of suction traps found in the largest genus of carnivorous plants

How can plants move without muscles, nerves and technical hinge analogies? Carnivorous bladderworts (Utricularia spp., Lentibulariaceae) perform one of the fastest movements known in the plant kingdom by capturing their prey (mainly small crustaceans) with suction traps. Capture lasts only half a millisecond, and animals are sucked into the trap with an acceleration of 600 g, which leaves no chance of escape. We review the current state of knowledge about these sophisticated trapping devices, highlight their biomechanical, functional-morphological and physiological peculiarities and discuss open questions for possible future studies.

Branching morphology of decapitated arborescent monocotyledons with secondary growth

UNLABELLED • PREMISE OF THE STUDY Dragon trees (Dracaenaceae) are arborescent monocotyledons with anomalous secondary growth and are able to branch, exhibiting a treelike habit. Studies of the morphology and anatomy of ramifications allow for a better understanding of the complex course and arrangement of the vascular bundles in the stem-branch attachment region for Dracaena and other arborescent monocots with anomalous secondary growth.• METHODS Morphological and anatomical analyses of ramifications induced in decapitated specimens of D. marginata and D. reflexa included serial sectioning, maceration, staining, and bleaching techniques as well as high and low resolution optical microscopy and three-dimensional (3D)-visualization techniques.• KEY RESULTS The use of innovative 3D reconstruction and high-resolution imaging revealed the extent of connections between branch and stem on various hierarchical levels in Dracaena A stem-clasping attachment of the side shoot was observed, which in more detail shows a strong regional dependence of course and connectivity of individual vascular bundles to the main stem. Consequently, the attachment of branch tissue is strongly limited to the outer periphery of the main stem.• CONCLUSIONS 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.

Functional morphology, biomechanics and biomimetic potential of stem-branch connections in Dracaena reflexa and Freycinetia insignis.

Summary Branching in plants is one of the most important assets for developing large arborescent growth forms with complex crowns. While the form and development of branching in gymnosperms and dicotyledonous trees is widely understood, very little is known about branching patterns and the structure of branch–stem-junctions in arborescent monocotyledons. For a better and quantitative understanding of the functional morphology of branch–stem-junctions in arborescent monocotyledons, we investigated the two species Dracaena reflexa and Freycinetia insignis. While D. reflexa is able to develop large arborescent forms with conspicuous crowns by anomalous secondary growth, F. insignis remains relatively small and is only capable of primary growth. Biomechanical investigations were performed by applying vertical loads up to rupture to lateral branches of both species. This allows the analysis of the fracture mechanics and the determination of the maximal force, stress and strain at rupture as well as the fracture toughness. Functional morphology was correlated with the mechanical behaviour of these plants and compared to data of other dicotyledonous trees. The high energy absorption found in the rupture process of lateral branches of D. reflexa and F. insignis makes them promising biological concept generators with a high potential for biomimetic implementation, i.e., for the development of branched fibre-reinforced technical composites. A wide range of constructional elements with branched (sub-)structures can be optimised by using solutions inspired by plant ramifications, e.g., in automotive and aerospace engineering, architecture, sports equipment and prosthetic manufacturing.