Morphology, anatomy and sleep movements of Ludwigia sedoides.

The diurnal motion of higher plants, responding to the alternation of day and night, known as nyctinastic movements or "sleep movements", has been discussed frequently. We present the first description of the circadian rhythm of the water plant Ludwigia sedoides (Humb. & Bonpl.) H.Hara of the family Onagraceae, furthermore its morphology and anatomy. Our results indicate that the plant's movements are endogenous, although environmental factors certainly have an influence. The majority of plants with nyctinastic leaf movements have a pulvinus, as the crucial part of the plant enabling this movement. Although the basal section of the L. sedoides petiole is not swollen, the tissue functions similarly to a pulvinus. It consists of a central conducting tissue with thick-walled cells, which is surrounded by thin-walled motor cells that can undergo visible shrinking and swelling. Thus, the tissue functionally corresponds to a pulvinus. Examinations of cellular processes, like measurements of the turgor pressure in the petiole, need to be evaluated in future studies.

Hunting techniques and their harvest as indicators of mammal diversity and threat in Northern Angola.

Over-exploitation of wildlife especially bushmeat trade is the second most important threat to animal biodiversity. This also applies to Northern Angola but data on bushmeat and hunting techniques for this region are rare. Therefore, we study the most common hunting techniques, frequently captured species, and their economic value, and discuss the local resource use in relation to Angolan law and urgent global crises like the loss of biodiversity, the food supply in South African countries, and the risk of zoonoses. We recorded bushmeat hunting in 27 localities in the province of Uíge, accompanied hunters along their snare lines and interviewed additional 20 locals. Seven main types of snares and traps and their characteristics were defined. Hunters own on average 92 ± 128.7 snares and traps and capture about 25.3 ± 23.6 animals monthly. In total, respondents recognized 28 species of mammals of which one is considered as extinct and two as very rare. The majority of recorded species are hunted regularly. Rodents are most commonly caught followed by primates and duikers. Harvesting rates decrease with species' body size, leading to high economic value of and achievable prices for rare, large animals. Overall, our results document the hunting pressure on mammals and the persisting popularity of bushmeat in Northern Angola which poses an imminent threat to remaining mammal populations. Moreover, it endangers ecosystem integrity, rural livelihoods, and human health through the risk of new zoonoses. Our findings underscore the urgent need for sustainable solutions. The Angolan government should play a more active role in enforcing existing hunting legislation to reduce illegal bushmeat trade. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10344-021-01541-y.

Evolution of Class II TCP genes in perianth bearing Piperales and their contribution to the bilateral calyx in Aristolochia.

Controlled spatiotemporal cell division and expansion are responsible for floral bilateral symmetry. Genetic studies have pointed to class II TCP genes as major regulators of cell division and floral patterning in model core eudicots. Here we study their evolution in perianth-bearing Piperales and their expression in Aristolochia, a rare occurrence of bilateral perianth outside eudicots and monocots. The evolution of class II TCP genes reveals single-copy CYCLOIDEA-like genes and three paralogs of CINCINNATA (CIN) in early diverging angiosperms. All class II TCP genes have independently duplicated in Aristolochia subgenus Siphisia. Also CIN2 genes duplicated before the diversification of Saruma and Asarum. Sequence analysis shows that CIN1 and CIN3 share motifs with Cyclin proteins and CIN2 genes have lost the miRNA319a binding site. Expression analyses of all paralogs of class II TCP genes in Aristolochia fimbriata point to a role of CYC and CIN genes in maintaining differential perianth expansion during mid- and late flower developmental stages by promoting cell division in the distal and ventral portion of the limb. It is likely that class II TCP genes also contribute to cell division in the leaf, the gynoecium and the ovules in A. fimbriata.

Functional principles of baobab fruit pedicels - anatomy and biomechanics.

BACKGROUND AND AIMS: Fruit pedicels have to deal with increasing loads after pollination due to continuous growth of the fruits. Thus, they represent interesting tissues from a mechanical as well as a developmental point of view. However, only a few studies exist on fruit pedicels. In this study, we unravel the anatomy and structural-mechanical relationships of the pedicel of Adansonia digitata, reaching up to 90 cm in length. METHODS: Morphological and anatomical analyses included examination of stained cross-sections from various positions along the stalk as well as X-ray microtomography and scanning electron microscopy. For mechanical testing, fibre bundles derived from the mature pedicels were examined via tension tests. For establishing the structural-mechanical relationships, the density of the fibre bundles as well as their cellulose microfibril distribution and chemical composition were analysed. KEY RESULTS: While in the peduncle the vascular tissue and the fibres are arranged in a concentric ring-like way, this organization shifts to the polystelic structure of separate fibre bundles in the pedicel. The polystelic pedicel possesses five vascular strands that consist of strong bast fibre bundles. The fibre bundles have a Young's modulus of up to 5 GPa, a tensile strength of up to 400 MPa, a high density (>1 g cm-3) and a high microfibril angle of around 20°. CONCLUSIONS: The structural arrangement as well as the combination of high density and high microfibril angle of the bast fibre bundles are probably optimized for bearing considerable strain in torsion and bending while at the same time allowing for carrying high-tension loads.

Recalcitrant deep and shallow nodes in Aristolochia (Aristolochiaceae) illuminated using anchored hybrid enrichment.

Recalcitrant relationships are characterized by very short internodes that can be found among shallow and deep phylogenetic scales all over the tree of life. Adding large amounts of presumably informative sequences, while decreasing systematic error, has been suggested as a possible approach to increase phylogenetic resolution. The development of enrichment strategies, coupled with next generation sequencing, resulted in a cost-effective way to facilitate the reconstruction of recalcitrant relationships. By applying the anchored hybrid enrichment (AHE) genome partitioning strategy to Aristolochia using an universal angiosperm probe set, we obtained 231-233 out of 517 single or low copy nuclear loci originally contained in the enrichment kit, resulting in a total alignment length of 154,756bp to 160,150bp. Since Aristolochia (Piperales; magnoliids) is distantly related to any angiosperm species whose genome has been used for the plant AHE probe design (Amborella trichopoda being the closest), it serves as a proof of universality for this probe set. Aristolochia comprises approximately 500 species grouped in several clades (OTUs), whose relationships to each other are partially unknown. Previous phylogenetic studies have shown that these lineages branched deep in time and in quick succession, seen as short-deep internodes. Short-shallow internodes are also characteristic of some Aristolochia lineages such as Aristolochia subsection Pentandrae, a clade of presumably recent diversification. This subsection is here included to test the performance of AHE at species level. Filtering and subsampling loci using the phylogenetic informativeness method resolves several recalcitrant phylogenetic relationships within Aristolochia. By assuming different ploidy levels during bioinformatics processing of raw data, first hints are obtained that polyploidization contributed to the evolution of Aristolochia. Phylogenetic results are discussed in the light of current systematics and morphology.

The springtail cuticle as a blueprint for omniphobic surfaces.

Omniphobic surfaces found in nature have great potential for enabling novel and emerging products and technologies to facilitate the daily life of human societies. One example is the water and even oil-repellent cuticle of springtails (Collembola). The wingless arthropods evolved a highly textured, hierarchically arranged surface pattern that affords mechanical robustness and wetting resistance even at elevated hydrostatic pressures. Springtail cuticle-derived surfaces therefore promise to overcome limitations of lotus-inspired surfaces (low durability, insufficient repellence of low surface tension liquids). In this review, we report on the liquid-repellent natural surfaces of arthropods living in aqueous or temporarily flooded habitats including water-walking insects or water spiders. In particular, we focus on springtails presenting an overview on the cuticular morphology and chemistry and their biological relevance. Based on the obtained liquid repellence of a variety of liquids with remarkable efficiency, the review provides general design criteria for robust omniphobic surfaces. In particular, the resistance against complete wetting and the mechanical stability strongly both depend on the topographical features of the nano- and micropatterned surface. The current understanding of the underlying principles and approaches to their technological implementation are summarized and discussed.

Pollen structure visualization using high-resolution laboratory-based hard X-ray tomography.

A laboratory-based X-ray microscope is used to investigate the 3D structure of unstained whole pollen grains. For the first time, high-resolution laboratory-based hard X-ray microscopy is applied to study pollen grains. Based on the efficient acquisition of statistically relevant information-rich images using Zernike phase contrast, both surface- and internal structures of pine pollen - including exine, intine and cellular structures - are clearly visualized. The specific volumes of these structures are calculated from the tomographic data. The systematic three-dimensional study of pollen grains provides morphological and structural information about taxonomic characters that are essential in palynology. Such studies have a direct impact on disciplines such as forestry, agriculture, horticulture, plant breeding and biodiversity.

Plant pressure sensitive adhesives: similar chemical properties in distantly related plant lineages.

MAIN CONCLUSION: A mixture of resins based on aliphatic esters and carboxylic acids occurs in distantly related genera Peperomia and Roridula , serving different functions as adhesion in seed dispersal and prey capture. According to mechanical characteristics, adhesive secretions on both leaves of the carnivorous flypaper Roridula gorgonias and epizoochorous fruits of Peperomia polystachya were expected to be similar. The chemical analysis of these adhesives turned out to be challenging because of the limited available mass for analysis. Size exclusion chromatography and Fourier transform infrared spectroscopy were suitable methods for the identification of a mixture of compounds, most appropriately containing natural resins based on aliphatic esters and carboxylic acids. The IR spectra of the Peperomia and Roridula adhesive resemble each other; they correspond to that of a synthetic ethylene-vinyl acetate copolymer, but slightly differ from that of natural tree resins. Thus, the pressure sensitive adhesive properties of the plant adhesives are chemically proved. Such adhesives seem to appear independently in distantly related plant lineages, habitats, life forms, as well as plant organs, and serve different functions such as prey capture in Roridula and fruit dispersal in Peperomia. However, more detailed chemical analyses still remain challenging because of the small available volume of plant adhesive.

LC-MS- and (1)H NMR-Based Metabolomic Analysis and in Vitro Toxicological Assessment of 43 Aristolochia Species.

Species of Aristolochia are used as herbal medicines worldwide. They cause aristolochic acid nephropathy (AAN), a devastating disease associated with kidney failure and renal cancer. Aristolochic acids I and II (1 and 2) are considered to be responsible for these nephrotoxic and carcinogenic effects. A wide range of other aristolochic acid analogues (AAAs) exist, and their implication in AAN may have been overlooked. An LC-MS- and (1)H NMR-based metabolomic analysis was carried out on 43 medicinally used Aristolochia species. The cytotoxicity and genotoxicity of 28 Aristolochia extracts were measured in human kidney (HK-2) cells. Compounds 1 and 2 were found to be the most common AAAs. However, AA IV (3), aristolactam I (4), and aristolactam BI (5) were also widespread. No correlation was found between the amounts of 1 or 2 and extract cytotoxicity against HK-2 cells. The genotoxicity and cytotoxicity of the extracts could be linked to their contents of 5, AA D (8), and AA IIIa (10). These results undermine the assumption that 1 and 2 are exclusively responsible for the toxicity of Aristolochia species. Other analogues are likely to contribute to their toxicity and need to be considered as nephrotoxic agents. These findings facilitate understanding of the nephrotoxic mechanisms of Aristolochia and have significance for the regulation of herbal medicines.

Multi-scale simulation of plant stem reinforcement by brachysclereids: A case study in apple fruit peduncles.

Sclereid formation in addition to or in gaps of fragmented fibre rings is common in dicotyledonous plant stems. Whether this sclereid formation is force-triggered remains open so far. In fruit peduncles of several Malus species as modified plant stems, for example, the persistent fibre ring is displaced to the centre by formation of cortex parenchyma during growth. Parenchyma cells subsequently differentiate into an additional layer of brachysclereids, previously interpreted as an adaptation to continuously rising fruit loads. The present study pursues a multi-scale numerical modelling approach, to verify the important effect for different cellular architectures in both sclerenchyma categories on the stiffness of these tissues and the entire peduncle. First, different material properties are simulated analogue to plant tissues on the basis of three cell types. A regular three-dimensional and a random Voronoi microstructure combined with various mechanical cell wall parameters are applied. Using homogenisation simulations based on HILL's principle, numerical calculations predict a lower effective homogenised tissue stiffness of isodiametric brachysclereids compared to those of fibres, confirming experimentally obtained data from Malus fruit peduncles. Furthermore, a curved peduncle model with a complex arrangement of different material layers is generated. Diverse material sets are tested under three representative loadings, using an adaptive diffuse domain approach (AMDiS). The model explains the function of sclereids as considerable contributors to the stiffness against bending and tensile deformations, as well as torsion, especially in consequence of superimposed load conditions in the case of a curved plant stem.

The betrayed thief - the extraordinary strategy of Aristolochia rotunda to deceive its pollinators.

Pollination of several angiosperms is based on deceit. In such systems, the flowers advertise a reward that ultimately is not provided. We report on a previously unknown pollination/mimicry system discovered in deceptive Aristolochia rotunda (Aristolochiaceae). Pollinators were collected in the natural habitat and identified. Flower scent and the volatiles of insects (models) potentially mimicked were analyzed by chemical analytical techniques. Electrophysiological and behavioral tests on the pollinators identified the components that mediate the plant-pollinator interaction and revealed the model of the mimicry system. The main pollinators of A. rotunda were female Chloropidae. They are food thieves that feed on secretions of true bugs (Miridae) while these are eaten by arthropod predators. Freshly killed mirids and Aristolochia flowers released the same scent components that chloropids use to find their food sources. Aristolochia exploits these components to deceive their chloropid pollinators. Aristolochia and other trap flowers were believed to lure saprophilous flies and mimic brood sites of pollinators. We demonstrate for A. rotunda, and hypothesize for other deceptive angiosperms, the evolution of a different, kleptomyiophilous pollination strategy. It involves scent mimicry and the exploitation of kleptoparasitic flies as pollinators. Our findings suggest a reconsideration of plants assumed to show sapromyiophilous pollination.

Intercontinental long-distance dispersal of Canellaceae from the New to the Old World revealed by a nuclear single copy gene and chloroplast loci.

Canellales, a clade consisting of Winteraceae and Canellaceae, represent the smallest order of magnoliid angiosperms. The clade shows a broad distribution throughout the Southern Hemisphere, across a diverse range of dry to wet tropical forests. In contrast to their sister-group, Winteraceae, the phylogenetic relations and biogeography within Canellaceae remain poorly studied. Here we present the phylogenetic relationships of all currently recognized genera of Canellales with a special focus on the Old World Canellaceae using a combined dataset consisting of the chloroplast trnK-matK-trnK-psbA and the nuclear single copy gene mag1 (Maigo 1). Within Canellaceae we found high statistical support for the monophyly of Warburgia and Cinnamosma. However, we also found relationships that differ from previous studies. Cinnamodendron splitted into two clades, a South American clade and a second clade confined to the Antilles and adjacent areas. Cinnamodendron from the Antilles, as well as Capsicodendron, South American Cinnamodendron and Pleodendron were not monophyletic. Consequently, Capsicodendron should be included in the South American Cinnamodendron clade and the genus Pleodendron merged with the Cinnamodendron clade from the Antilles. We also found that Warburgia (restricted to mainland eastern Africa) together with the South American Cinnamodendron and Capsicodendron are sister to the Malagasy genus Cinnamosma. In addition to the unexpected geographical relationships, both biogeographic and molecular clock analyses suggest vicariance, extinction, and at least one intercontinental long-distance-dispersal event. Our dating result contrasts previous work on Winteraceae. Diversification of Winteraceae took place in the Paleocene, predating the Canellaceae diversification by 13 MA in the Eocene. The phylogenetic relationships for Canellaceae supported here offer a solid framework for a future taxonomic revision of the Canellaceae.

Ontogenetic tissue modification in Malus fruit peduncles: the role of sclereids.

BACKGROUND AND AIMS: Apple (Malus) fruit peduncles are highly modified stems with limited secondary growth because fruit ripening lasts only one season. They must reliably connect rather heavy fruits to the branch and cope with increasing fruit weight, which induces dynamic stresses under oscillating wind loads. This study focuses on tissue modification of these small, exposed structures during fruit development. METHODS: A combination of microscopic, static and dynamic mechanical tests, as well as Raman spectroscopy, was used to study structure-function relationships in peduncles of one cultivar and 12 wild species, representatively chosen from all sections of the genus Malus. Tissue differentiation and ontogenetic changes in mechanical properties of Malus peduncles were observed throughout one growing season and after successive removal of tissues. KEY RESULTS: Unlike in regular stems, the vascular cambium produces mainly phloem during secondary growth. Hence, in addition to a reduced xylem, all species developed a centrally arranged sclerenchyma ring composed of fibres and brachysclereids. Based on differences in cell-wall thickness, and proportions and arrangement of sclereids, two types of peduncle construction could be distinguished. Fibres provide an increased maximum tensile strength and contribute most to the overall axial rigidity of the peduncles. Sclereids contribute insignificantly to peduncle strength; however, despite being shown to have a lower elastic modulus than fibres, they are the most effective tissue in stiffening peduncles against bending. CONCLUSIONS: The experimental data revealed that sclereids originating from cortical parenchyma act as 'accessory' cells to enhance proportions of sclerenchyma during secondary growth in peduncles. The mechanism can be interpreted as an adaptation to continuously increasing fruit loads. Under oscillating longitudinal stresses, sclereids may be regarded as regulating elements between maintenance of stiffness and viscous damping, the latter property being attributed to the cortical parenchyma.

Major trends in stem anatomy and growth forms in the perianth-bearing Piperales, with special focus on Aristolochia.

BACKGROUND AND AIMS: The order Piperales has the highest diversity of growth forms among the earliest angiosperm lineages, including trees, shrubs, climbers and herbs. However, within the perianth-bearing Piperales (Asarum, Saruma, Lactoris, Hydnora, Prosopanche, Thottea and Aristolochia), climbing species only occur in the most species-rich genus Aristolochia. This study traces anatomical and morphological traits among these lineages, to detect trends in growth form evolution and developmental processes. METHODS: Transverse stem sections of different developmental stages of representatives of Asarum, Saruma, Lactoris, Hydnora, Thottea and Aristolochia were compared and anatomical traits were linked to growth form evolution. Biomechanical properties of representative climbers were determined in three-point bending tests and are discussed based on the anatomical observations. Growth form evolution of the perianth-bearing Piperales was reconstructed by ancestral character state reconstruction using Mesquite. KEY RESULTS: While species of Asarum and Saruma are exclusively herbaceous, species of the remaining genera show a higher diversity of growth habit and anatomy. This growth form diversity is accompanied by a more complex stem anatomy and appropriate biomechanical properties. The ancestral growth form of the perianth-bearing Piperales is reconstructed with either a shrub-like or herbaceous character state, while the following three backbone nodes in the reconstruction show a shrub-like character state. Accordingly, the climbing habit most probably evolved in the ancestor of Aristolochia. CONCLUSIONS: Since the ancestor of the perianth-bearing Piperales has been reconstructed with a herb- or shrub-like habit, it is proposed that the climbing habit is a derived growth form, which evolved with the diversification of Aristolochia, and might have been a key feature for its diversification. Observed anatomical synapomorphies, such as the perivascular fibres in Lactoris, Thottea and Aristolochia, support the phylogenetic relationship of several lineages within the perianth-bearing Piperales. In addition, the hypothesis that the vegetative organs of the holoparasitic Hydnoraceae are most probably rhizomes is confirmed.

Cell differentiation and tissue formation in the unique fruits of devil's claws (Martyniaceae).

• Premise of the study: Martyniaceae are characterized by capsules with two upwardly curved, horn-shaped extensions representing morphologically specialized epizoochorous fruits. Because the capsules are assumed to cling to hooves and ankles of large mammals, fiber arrangement and tissue combinations within the endocarp ensuring proper attachment to the vector's feet during transport are of particular interest. In this first detailed anatomical investigation, the functional adaptation of the fruits and their implications for the specific dispersal mode are provided. The peculiar fiber arrangement may also be of interest for future biomimetic composite materials.• Methods: Endocarp anatomy and details of tissue differentiation were examined in fruits of Ibicella lutea and Proboscidea louisianica subsp. fragrans combining light microscopy, SEM, and x-ray microtomography analysis.• Key results: While tips of the extensions are predominantly reinforced by longitudinally oriented fibers, in the middle segment these fibers are densely packed in individual bundles entwined and separated by transversely elongated cells. Within the capsule wall, the fiber bundles are embedded in a dense mesh of transversely oriented fibers that circularly reinforce and protect the loculus. This fibrous pericarp tissue develops within few days by localized cell divisions and intrusive growth of primarily isodiametric parenchyma cells in the pistil.• Conclusions: The study allows insight into a unique and complex example of functionally driven cell growth and tissue formation. Long-horned fruits of Martyniaceae obviously are highly specialized to epizoochorous dispersal, pointing to primary vector-related seed dispersal. The highly ordered arrangement of fibers results in a great mechanical firmness.

Chemical imitation of yeast fermentation by the drosophilid-pollinated deceptive trap-flower Aristolochia baetica (Aristolochiaceae).

Deceptive flowers, unlike in mutualistic pollination systems, mislead their pollinators by advertising rewards which ultimately are not provided. Although our understanding of deceptive pollination systems increased in recent years, the attractive signals and deceptive strategies in the majority of species remain unknown. This is also true for the genus Aristolochia, famous for its deceptive and fly-pollinated trap flowers. Representatives of this genus were generally assumed to be oviposition-site mimics, imitating vertebrate carrion or mushrooms. However, recent studies found a broader spectrum of strategies, including kleptomyiophily and imitation of invertebrate carrion. A different deceptive strategy is presented here for the western Mediterranean Aristolochia baetica L. We found that this species is mostly pollinated by drosophilid flies (Drosophilidae, mostly Drosophila spp.), which typically feed on fermenting fruit infested by yeasts. The flowers of A. baetica emitted mostly typical yeast volatiles, predominantly the aliphatic compounds acetoin and 2,3-butandiol, and derived acetates, as well as the aromatic compound 2-phenylethanol. Analyses of the absolute configurations of the chiral volatiles revealed weakly (acetoin, 2,3-butanediol) to strongly (mono- and diacetates) biased stereoisomer-ratios. Electrophysiological (GC-EAD) experiments and lab bioassays demonstrated that most of the floral volatiles, although not all stereoisomers of chiral compounds, were physiologically active and attractive in drosophilid pollinators; a synthetic mixture thereof successfully attracted them in field and lab bioassays. We conclude that A. baetica chemically mimics yeast fermentation to deceive its pollinators. This deceptive strategy (scent chemistry, pollinators, trapping function) is also known from more distantly related plants, such as Arum palaestinum Boiss. (Araceae) and Ceropegia spp. (Apocynaceae), suggesting convergent evolution. In contrast to other studies working on floral scents in plants imitating breeding sites, the present study considered the absolute configuration of chiral compounds.

Minimal peptide motif for non-covalent peptide-heparin hydrogels.

Reduction of complexity of the extracellular matrix (ECM) to a non-covalent structure with minimal chemically defined components represents an attractive avenue for understanding the biology of the ECM. The resulting system could lead to the design of tailor-made biomaterials that incorporate varying functionalities. Negatively charged glycosaminoglycans are the major components of the ECM. Their interaction with positively charged proteins is important for dynamic three-dimensional scaffold formation and function. We designed and screened minimal peptide motifs whose conjugates with polyethylene glycol interact with heparin to form non-covalent hydrogels. Here we show the structure/function relationship of the (RA)(n) and (KA)(n) motifs and determined that both basic residues and the heparin-induced α-helix formation are important for the assembly process. Simple rules allowed us to tune various aspects of the matrix system such as the gelation rates, biodegradability, rheological properties, and biofunctionality. The hydrogels can encapsulate cells and support cell survival.

Characterization of the basal angiosperm Aristolochia fimbriata: a potential experimental system for genetic studies.

BACKGROUND: Previous studies in basal angiosperms have provided insight into the diversity within the angiosperm lineage and helped to polarize analyses of flowering plant evolution. However, there is still not an experimental system for genetic studies among basal angiosperms to facilitate comparative studies and functional investigation. It would be desirable to identify a basal angiosperm experimental system that possesses many of the features found in existing plant model systems (e.g., Arabidopsis and Oryza). RESULTS: We have considered all basal angiosperm families for general characteristics important for experimental systems, including availability to the scientific community, growth habit, and membership in a large basal angiosperm group that displays a wide spectrum of phenotypic diversity. Most basal angiosperms are woody or aquatic, thus are not well-suited for large scale cultivation, and were excluded. We further investigated members of Aristolochiaceae for ease of culture, life cycle, genome size, and chromosome number. We demonstrated self-compatibility for Aristolochia elegans and A. fimbriata, and transformation with a GFP reporter construct for Saruma henryi and A. fimbriata. Furthermore, A. fimbriata was easily cultivated with a life cycle of just three months, could be regenerated in a tissue culture system, and had one of the smallest genomes among basal angiosperms. An extensive multi-tissue EST dataset was produced for A. fimbriata that includes over 3.8 million 454 sequence reads. CONCLUSIONS: Aristolochia fimbriata has numerous features that facilitate genetic studies and is suggested as a potential model system for use with a wide variety of technologies. Emerging genetic and genomic tools for A. fimbriata and closely related species can aid the investigation of floral biology, developmental genetics, biochemical pathways important in plant-insect interactions as well as human health, and various other features present in early angiosperms.

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.

Wetting resistance at its topographical limit: the benefit of mushroom and serif T structures.

Springtails (Collembola) are wingless arthropods adapted to cutaneous respiration in temporarily rain-flooded habitats. They immediately form a plastron, protecting them against suffocation upon immersion into water and even low-surface-tension liquids such as alkanes. Recent experimental studies revealed a high-pressure resistance of such plastrons against collapse. In this work, skin sections of Orthonychiurus stachianus are studied by transmission electron microscopy. The micrographs reveal cavity side-wall profiles with characteristic overhangs. These were fitted by polynomials to allow access for analytical and numerical calculations of the breakthrough pressure, that is, the barrier against plastron collapse. Furthermore, model profiles with well-defined geometries were used to set the obtained results into context and to develop a general design principle for the most robust surface structures. Our results indicate the decisive role of the sectional profile of overhanging structures to form a robust heterogeneous wetting state for low-surface-tension liquids that enables the omniphobicity. Furthermore, the design principles of mushroom and serif T structures pave the way for omniphobic surfaces with a high-pressure resistance irrespective of solid surface chemistry.