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author:("masseter, Tom")
1.  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.
PMCID: PMC3813340  PMID: 24132310
columnar cacti; functional anatomy; branching; finite-element analysis; biomimetics
2.  Trap diversity and evolution in the family Droseraceae 
Plant Signaling & Behavior  2013;8(7):e24685.
We review trapping mechanisms in the carnivorous flowering plant family Droseraceae (order Caryophyllales). Its members are generally known to attract, capture, retain and digest prey animals (mainly arthropods) with active snap-traps (Aldrovanda, Dionaea) or with active sticky flypaper traps (Drosera) and to absorb the resulting nutrients. Recent investigations revealed how the snap-traps of Aldrovanda vesiculosa (waterwheel plant) and Dionaea muscipula (Venus’ flytrap) work mechanically and how these apparently similar devices differ as to their functional morphology and shutting mechanics. The Sundews (Drosera spp.) are generally known to possess leaves covered with glue-tentacles that both can bend toward and around stuck prey. Recently, it was shown that there exists in this genus a higher diversity of different tentacle types and trap configurations than previously known which presumably reflect adaptations to different prey spectra. Based on these recent findings, we finally comment on possible ways for intrafamiliar trap evolution.
PMCID: PMC3907454  PMID: 23603942
Aldrovanda; carnivorous plant; catapult-flypaper-trap; Dionaea; Drosera; sticky flypaper trap; snap-trap
3.  Ultra-fast underwater suction traps 
Carnivorous aquatic Utricularia species catch small prey animals using millimetre-sized underwater suction traps, which have fascinated scientists since Darwin's 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.
PMCID: PMC3151700  PMID: 21325323
bladderwort; carnivorous/insectivorous plants; suction mechanism; functional morphology; fluid dynamics; Utricularia
4.  Catapulting Tentacles in a Sticky Carnivorous Plant 
PLoS ONE  2012;7(9):e45735.
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.
PMCID: PMC3458893  PMID: 23049849
5.  Functional morphology, biomechanics and biomimetic potential of stem–branch connections in Dracaena reflexa and Freycinetia insignis  
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.
PMCID: PMC3148042  PMID: 21977429
Biomimetics; branching; Dracaena reflexa; Freycinetia insignis; monocotyledons
6.  Quantitative and qualitative changes in primary and secondary stem organization of Aristolochia macrophylla during ontogeny: functional growth analysis and experiments 
Journal of Experimental Botany  2008;59(11):2955-2967.
The anatomy of young and old stems of Aristolochia macrophylla has been investigated for a better understanding of how secondary growth processes cause changes in the stem anatomy of a lianescent plant. In A. macrophylla, following an increase in volume of secondary vascular tissues, the cortical tissues are deformed and the outer sclerenchymatous cylinder ruptures. Morphometric measurements prove that the inner zone of the cortical parenchymatous tissue is compressed prior to the rupture of the outer sclerenchymatous cylinder. After the rupture has occurred, the radial width of the inner primary cortex slightly increases again. This could be caused by strain relaxation, suggesting that the inner primary cortex mechanically behaves similarly to cellular technical foam rubbers. Two different experiments were undertaken to test the outer cortical cylinders mechanically. The outer cortical cylinders comprise the outer sclerenchymatous cortical tissue and a collenchymatous sheath underneath the epidermis and the epidermis. In a first experiment, transverse compression loads were applied to the outside of the cortical cylinders causing ovalization of the cylinder until failure. This experiment allowed the Young's Modulus of the outer cortical cylinders to be determined. In a second set of experiments, radial hydraulic pressure was applied to the inside of the cortical cylinders, mimicking the mechanical effects of internal growth processes. The increase of the internal pressure finally led to rupture of the cortical cylinders. The circumferential stresses acting on the inner surface of the cortical cylinders were calculated. These data allow quantitative estimates of the radial and circumferential pressures effected by vascular secondary growth processes during ontogeny in A. macrophylla stems. The experimental results further indicate that the outer sclerenchymatous cylinder is the main contributor to mechanical stability of young A. macrophylla stems.
PMCID: PMC2504350  PMID: 18573799
Aristolochia macrophylla; biomechanics; ontogeny; primary organization; secondary growth; vine

Results 1-6 (6)