Mechanical Defense Research Articles

Capturing the micro-communities: Insights into biogenesis and architecture of bacterial biofilms.

Biofilm is an assemblage of microorganisms embedded within the extracellular matrix that provides mechanical stability, nutrient absorption, antimicrobial resistance, cell-cell interactions, and defence against host immune system. Various biomolecules such as lipids, carbohydrates, protein polymers (amyloid), and eDNA are present in the matrix playing significant role in determining the distinctive properties of biofilm. The formation of biofilms contributes to resistance against antimicrobial therapy in most of the human infections and exacerbates existing diseases. Therefore, this field requires several state-of-the-art techniques to fully understand the 3-D organization of biofilms, their cell behaviour and responses to pharmaceutical treatments. Here, we explore the assembly and regulation of biofilm biogenesis in the context of matrix components and highlight the significance of high-resolution imaging and analysing techniques for monitoring complex biofilm architecture. Our review also emphasizes the novelty and advancements in techniques to visualise biofilm structure and composition, providing valuable insights to understand biofilm-related infections.

Pangolin scales as adaptations for innate immunity against pathogens

BackgroundPangolins are the only mammals that have overlapping scales covering most of their bodies, and they play a crucial role in the ecosystem, biological research, and human health and disease. Previous studies indicated pangolin scale might provide an important mechanical defense to themselves. The origin and exact functions of this unique trait remain a mystery. Using a multi-omics analysis approach, we report a novel functional explanation for how mammalian scales can provide host–pathogen defense.ResultsOur data suggest that pangolin scales have a sophisticated structure that could potentially trap pathogens. We identified numerous proteins and metabolites exhibiting antimicrobial activity, which could suggest a role for scales in pathogen defense. Notably, we found evidence suggesting the presence of exosomes derived from diverse cellular origins, including mesenchymal stem cells, immune cells, and keratinocytes. This observation suggests a complex interplay where various cell types may contribute to the release of exosomes and antimicrobial compounds at the interface between scales and viable tissue. These findings indicate that pangolin scales may serve as a multifaceted defense system, potentially contributing to innate immunity. Comparisons with human nail and hair revealed pangolin-specific proteins that were enriched in functions relating to sensing, immune responses, neutrophil degranulation, and stress responses. We demonstrated the antimicrobial activity of key pangolin scale components on pathogenic bacteria by antimicrobial assays.ConclusionsThis study identifies a potential role of pangolin scales and implicates scales, as possible determinants of pathogen defense due to their structure and contents. We indicate for the first time the presence of exosomes in pangolin scales and propose the new functions of scales and their mechanisms. This new mechanism could have implications for multiple fields, including providing interesting new research directions and important insights that can be useful for synthesizing and implementing new biomimetic antimicrobial approaches.

Exploring Novel Genomic Loci and Candidate Genes Associated with Plant Height in Bulgarian Bread Wheat via Multi-Model GWAS.

In the context of crop breeding, plant height (PH) plays a pivotal role in determining straw and grain yield. Although extensive research has explored the genetic control of PH in wheat, there remains an opportunity for further advancements by integrating genomics with growth-related phenomics. Our study utilizes the latest genome-wide association scan (GWAS) techniques to unravel the genetic basis of temporal variation in PH across 179 Bulgarian bread wheat accessions, including landraces, tall historical, and semi-dwarf modern varieties. A GWAS was performed with phenotypic data from three growing seasons, the calculated best linear unbiased estimators, and the leveraging genotypic information from the 25K Infinium iSelect array, using three statistical methods (MLM, FarmCPU, and BLINK). Twenty-five quantitative trait loci (QTL) associated with PH were identified across fourteen chromosomes, encompassing 21 environmentally stable quantitative trait nucleotides (QTNs), and four haplotype blocks. Certain loci (17) on chromosomes 1A, 1B, 1D, 2A, 2D, 3A, 3B, 4A, 5B, 5D, and 6A remain unlinked to any known Rht (Reduced height) genes, QTL, or GWAS loci associated with PH, and represent novel regions of potential breeding significance. Notably, these loci exhibit varying effects on PH, contribute significantly to natural variance, and are expressed during seedling to reproductive stages. The haplotype block on chromosome 6A contains five QTN loci associated with reduced height and two loci promoting height. This configuration suggests a substantial impact on natural variation and holds promise for accurate marker-assisted selection. The potentially novel genomic regions harbor putative candidate gene coding for glutamine synthetase, gibberellin 2-oxidase, auxin response factor, ethylene-responsive transcription factor, and nitric oxide synthase; cell cycle-related genes, encoding cyclin, regulator of chromosome condensation (RCC1) protein, katanin p60 ATPase-containing subunit, and expansins; genes implicated in stem mechanical strength and defense mechanisms, as well as gene regulators such as transcription factors and protein kinases. These findings enrich the pool of semi-dwarfing gene resources, providing the potential to further optimize PH, improve lodging resistance, and achieve higher grain yields in bread wheat.

Secretory Cells in Halla parthenopeia (Oenonidae): Potential Implications for the Feeding and Defence Strategies of a Carnivorous Burrowing Polychaete.

Carnivorous polychaetes are known to bear diversified and often unique anatomical and behavioural adaptations for predation and defence. Halla parthenopeia, a species known to be a specialized predator of clams, thrives in the soft bottoms of the Mediterranean Sea, holding potential for polyculture and biotechnology due to the secretion of bioactive compounds. Our objective was to provide a comprehensive description of H. parthenopeia's anatomy and microanatomy, shedding light on the relation between morphology and habitat, chemical defences, and feeding behaviour. The pharynx, housing maxillae and mandibles connected to an extensive mucus gland, occupies a considerable portion of the worm's length, reaching beyond the oesophagus. This unique gland is responsible for secreting the feeding mucus, which immobilizes and aids in the digestion of clams probably acting as a vehicle of bioactive compounds synthesized by specialized serous cells in the mouth. Moreover, H. parthenopeia combines behavioural tactics, such as burrowing, and anatomical defences to evade predators. Examination of its epidermis revealed a thick cuticle layer and abundant mucocytes secreting locomotion mucus, both of which save the worm from mechanical harm during movement. When it is preyed upon, the worm can release a substantial amount of Hallachrome, a toxic anthraquinone produced by specific cells in its distal region. This pigment, with its known antimicrobial properties, likely acts as a chemical shield in case of injury. The results suggest that the ability of H. parthenopeia to prey on bivalves and to provide mechanical protection plus defence against pathogens rely on its ability to secrete distinct types of mucus. The interplay between highly specialized microanatomical features and complex behaviours underscores its adaptation as a predator in marine benthic environments.

Reduced palatability, fast flight, and tails: decoding the defence arsenal of Eudaminae skipper butterflies in a Neotropical locality.

Prey often rely on multiple defences against predators, such as flight speed, attack deflection from vital body parts, or unpleasant taste, but our understanding on how often and why they are co-exhibited remains limited. Eudaminae skipper butterflies use fast flight and mechanical defences (hindwing tails), but whether they use other defences like unpalatability (consumption deterrence) and how these defences interact have not been assessed. We tested the palatability of 12 abundant Eudaminae species in Peru, using training and feeding experiments with domestic chicks. Further, we approximated the difficulty of capture based on flight speed and quantified it by wing loading. We performed phylogenetic regressions to find any association between multiple defences, body size, and habitat preference. We found a broad range of palatability in Eudaminae, within and among species. Contrary to current understanding, palatability was negatively correlated with wing loading, suggesting that faster butterflies tend to have lower palatability. The relative length of hindwing tails did not explain the level of butterfly palatability, showing that attack deflection and consumption deterrence are not mutually exclusive. Habitat preference (open or forested environments) did not explain the level of palatability either, although butterflies with high wing loading tended to occupy semi-closed or closed habitats. Finally, the level of unpalatability in Eudaminae is size dependent. Larger butterflies are less palatable, perhaps because of higher detectability/preference by predators. Altogether, our findings shed light on the contexts favouring the prevalence of single versus multiple defensive strategies in prey.

Predation, but not herbivory, declines with elevation in a tropical rainforest

AbstractNaturally, insect herbivore populations are controlled by their plant hosts and predators. These ‘bottom-up’ and ‘top-down’ controls influence leaf area lost to herbivory. Bottom-up control of herbivory may be driven by leaf nutrients and plant defences. Top-down control can be driven by abundance and species richness of natural enemies, host or prey specificity, and predation strategies (e.g., active searching or sit-and-wait ‘ambush’ predation). The relative importance of bottom-up and top-down controls is unresolved but likely to vary spatially and temporally and under different environmental conditions such as changing temperature. We surveyed leaf carbon and nitrogen, leaf area loss, and attacks on plasticine caterpillars across a tropical elevational gradient in Xishuangbanna, Yunnan Provence, China. We show that predatory foraging activity decreases with elevation and temperature, whereas leaf nutrients and leaf area loss from herbivory remains more or less constant. Predation patterns were driven by ants, which are thermophiles and therefore more active, abundant, and diverse at warmer, lower elevations. Leaf nutritional values are important in driving herbivory patterns as herbivory was stable across this gradient, but other factors such as mechanical defences and herbivore-induced plant volatiles demand further study. Elevational studies provide insight into how ecosystem function will shift under climate change. As increasing temperatures following climate change allows predatory groups like ants to exploit higher elevations, top-down control in high elevation habitats could increase, resulting in re-wiring of these ecologically sensitive communities. At the same time, top-down control at lower elevations may be at risk if critical thermal maxima for natural enemies are exceeded.

Correction to: 'Pollen chemical and mechanical defences restrict host-plant use by bees' (2024), by Rivest et al.

Correction to: 'Pollen chemical and mechanical defences restrict host-plant use by bees' (2024), by Rivest et al.

Pollen chemical and mechanical defences restrict host-plant use by bees.

Plants produce an array of chemical and mechanical defences that provide protection against many herbivores and pathogens. Putatively defensive compounds and structures can even occur in floral rewards: for example, the pollen of some plant taxa contains toxic compounds or possesses conspicuous spines. Yet little is known about whether pollen defences restrict host-plant use by bees. In other words, do bees, like other insect herbivores, tolerate the defences of their specific host plants while being harmed by non-host defences? To answer this question, we compared the effects of a chemical defence from Lupinus (Fabaceae) pollen and a putative mechanical defence (pollen spines) from Asteraceae pollen on larval survival of nine bee species in the tribe Osmiini (Megachilidae) varying in their pollen-host use. We found that both types of pollen defences reduce larval survival rate in some bee species. These detrimental effects were, however, mediated by host-plant associations, with bees being more tolerant of the pollen defences of their hosts, relative to the defences of plant taxa exploited by other species. This pattern strongly suggests that bees are adapted to the pollen defences of their hosts, and that host-plant use by bees is constrained by their ability to tolerate such defences.

Comprehensive analysis of silicon impact on defense and metabolic responses in rice exposed to herbivory stress.

Silicon (Si) uptake is generally beneficial for plants that need protection from insect herbivores. In pursue of mechanisms involved in Si-mediated defense, we comprehensively explored the impact of Si on several defensive and metabolic traits in rice exposed to simulated and real herbivory of Mythimna loreyi Duponchel larvae. Hydroponic experiments showed that Si-deprived rice supplemented with Si 72 h prior to insect infestation were similarly resistant to larvae as plants continuously grown in Si-containing media. Both Si and herbivory altered primary metabolism in rice, including the levels of several sugars, amino acids, and organic acids. While the accumulation of sugars was generally positively correlated with Si presence, multiple amino acids showed a negative correlation trend with Si supplementation. The levels of secondary metabolites, including isopentylamine, p-coumaroylputrescine and feruloylputrescine, were typically higher in the leaves of Si-supplemented plants exposed to herbivory stress compared to Si-deprived plants. In addition, simulated herbivory treatment in Si-supplemented plants induced more volatile emissions relative to Si-deprived plants, which was consistent with the increased transcripts of key genes involved in volatile biosynthesis. In ecological interactions, Si alone did not affect the oviposition choice of M. loreyi but gravid females showed a significant preference for simulated herbivory-treated/Si-deprived compared to Si-supplemented plants. Our data suggest that apart from mechanical defense, Si may affect rice metabolism in multiple ways that might enhance/modulate defense responses of rice under herbivory stress.

Soil cadmium pollution facilitated the invasion of alligator weed through enhanced herbivore resistance and competitive ability over a congeneric species.

A number of invasive plant species, such as Alternanthera philoxeroides, have been documented to be able to accumulate trace metal elements in their tissues. Since metal accumulation in plants can serve as a defence against herbivores, we hypothesized that metal pollution will increase herbivore resistance of metal-accumulating invasive plant species and such a benefit will grant them a competitive advantage over local co-occurring plants. In this study, we compared the differences in plant growth and herbivore feeding preference between A. philoxeroides and its native congener Alternanthera sessilis in single and mixed cultures with and without soil cadmium (Cd) pollution. The results showed that A. philoxeroides plants were more tolerant to Cd stress and accumulated more Cd in the leaves than A. sessilis. Cd exposure increased the resistance of A. philoxeroides against a specialist and a generalist herbivore compared withA. sessilis. Competition experiments indicated that Cd stress largely increased the competitive advantage of A. philoxeroides over A. sessilis with or without herbivore pressures. The differences in herbivore resistance between the two plant species under soil Cd stress are most likely due to the deterring effect of Cd accumulation and Cd-enhanced mechanical defences rather than changes in leaf specialized metabolites.

Effects of metal amendment and metalloid supplementation on foliar defences are plant accession-specific in the hyperaccumulator Arabidopsis halleri.

Soil pollution by metals and metalloids as a consequence of anthropogenic industrialisation exerts a seriously damaging impact on ecosystems. However, certain plant species, termed hyperaccumulators, are able to accumulate extraordinarily high concentrations of these metal(loid)s in their aboveground tissues. Such hyperaccumulation of metal(loid)s is known to act as a defence against various antagonists, such as herbivores and pathogens. We investigated the influences of metal(loid)s on potential defence traits, such as foliar elemental, organic and mechanical defences, in the hyperaccumulator plant species Arabidopsis halleri (Brassicaceae) by artificially amending the soil with common metallic pollutants, namely cadmium (Cd) and zinc (Zn). Additionally, unamended and metal-amended soils were supplemented with the metalloid silicon (Si) to study whether Si could alleviate metal excess. Individuals originating from one non-/low- and two moderately to highly metal-contaminated sites with different metal concentrations (hereafter called accessions) were grown for eight weeks in a full-factorial design under standardised conditions. There were significant interactive effects of metal amendment and Si supplementation on foliar concentrations of certain elements (Zn, Si, aluminium (Al), iron (Fe), potassium (K) and sulfur (S), but these were accession-specific. Profiles of glucosinolates, characteristic organic defences of Brassicaceae, were distinct among accessions, and the composition was affected by soil metal amendment. Moreover, plants grown on metal-amended soil contained lower concentrations of total glucosinolates in one of the accessions, which suggests a potential trade-off between inorganic defence acquisition and biosynthesis of organic defence. The density of foliar trichomes, as a proxy for the first layer of mechanical defence, was also influenced by metal amendment and/or Si supplementation in an accession-dependent manner. Our study highlights the importance of examining the effects of co-occurring metal(loid)s in soil on various foliar defence traits in different accessions of a hyperaccumulating species.

Epiphanes brachionus spinosa from a temporary habitat in the Chihuahuan Desert: Morphological response to Asplanchna and control of sexual reproduction

Abstract The rotifer Epiphanes brachionus spinosa occurs in shallow temporary waters with hydroperiods up to several months in the Chihuahuan Desert (U.S.A. and Mexico). Clonal populations from one such habitat were initiated from stem females hatched from fertilised resting eggs in flooded dried sediment, and cultured with the alga Cryptomonas erosa at 19°C in a photoperiod (L:D 16:8). Experiments show that the rotifer has: (1) a morphological response to the predatory rotifer Asplanchna, with which it can co‐occur; and (2) an early and constant propensity for sex and resting‐egg production during population development. Stem females, and females from later generations, have two posterior spines. Measurements of live juveniles and adults indicate that spine length increases isometrically during postnatal growth. Presence of live Asplanchna brightwellii, or its kairomone in Asplanchna‐conditioned medium, significantly increase spine length. In one clone, spine lengths of juvenile Epiphanes from cultures with or without live Asplanchna were, respectively, c. 40 and c. 27 μm. In that clone, spine lengths of adult Epiphanes in cultures with or without Asplanchna kairomone were, respectively, c. 54 and c. 37 μm. In another clone, these spine lengths were, respectively, c. 44 and c. 36 μm. Asplanchna‐induced spine elongation may act as a mechanical defence against capture and ingestion by the predator. Sexual reproduction in E. brachionus spinosa populations is initiated soon after populations develop from stem females and then continues at a rate allowing both population growth by female parthenogenesis and production of resting eggs. Resting eggs hatched after 6–12 days at 19°C. Stem females were amictic (producing daughters parthenogenetically) but produced some daughters that were mictic (producing haploid males parthenogenetically or fertilised resting eggs). In subsequent generations tested 2–7 weeks after hatching of stem females, amictic females from three clonal populations produced similar proportions of mictic daughters (mean c. 0.25) when cultured singly in large volumes (15 and 40 ml) or a small one (1.5 ml). Mictic‐female production is probably automatic and controlled by an endogenous mechanism, rather than specifically induced by crowding or some other environmental factor. Early and continuous sexual reproduction assures production of resting eggs throughout short and unpredictable hydroperiods.

Integrated Multiomics and Synergistic Functional Network Revealed the Mechanism in the Tolerance of Different Ecotypes of Salvia miltiorrhiza Bge. to Doxycycline Pollution.

Tetracycline pollution in soil irreversibly damages the biosafety of plants by inhibiting the mitochondrial function. Some traditional Chinese medicine (TCM) plants, such as Salvia miltiorrhiza Bunge, have a strong tolerance to mitochondrial damage. We comprehensively compared the doxycycline (DOX) tolerances of two ecotypes of S. miltiorrhiza in the Sichuan and Shandong provinces and found that the Sichuan ecotype had a lower yield reduction, more stable accumulation of medicinal ingredients, higher mitochondrial integrity, and a more robust antioxidant system. The synergetic response networks under DOX pollution of both ecotypes were constructed using RNA sequencing and ultrahigh-performance liquid chromatography-tandem mass spectrometry. The differentiation of the downstream pathways of aromatic amino acids (AAAs) produced variations in the DOX tolerance of S. miltiorrhiza in different regions. The Sichuan ecotype maintained redox homeostasis and xylem development by activating salvianolic acid and indole biosynthesis, while the Shandong ecotype balanced chemical and mechanical defenses by regulating the flavonoid biosynthesis. Rosmarinic acid, a downstream AAA molecule, maintains the mitochondrial homeostasis of plant seedlings under DOX pollution by targeting the ABCG28 transporter. We also highlight the significance of downstream AAA small molecules in guiding the development of bio-based environmental pollution remediation agents.

Genome-Wide Identification and Expression Analysis of Dendrocalamus farinosus CCoAOMT Gene Family and the Role of DfCCoAOMT14 Involved in Lignin Synthesis.

As the main component of plant cell walls, lignin can not only provide mechanical strength and physical defense for plants, but can also be an important indicator affecting the properties and quality of wood and bamboo. Dendrocalamus farinosus is an important economic bamboo species for both shoots and timber in southwest China, with the advantages of fast growth, high yield and slender fiber. Caffeoyl-coenzyme A-O-methyltransferase (CCoAOMT) is a key rate-limiting enzyme in the lignin biosynthesis pathway, but little is known about it in D. farinosus. Here, a total of 17 DfCCoAOMT genes were identified based on the D. farinosus whole genome. DfCCoAOMT1/14/15/16 were homologs of AtCCoAOMT1. DfCCoAOMT6/9/14/15/16 were highly expressed in stems of D. farinosus; this is consistent with the trend of lignin accumulation during bamboo shoot elongation, especially DfCCoAOMT14. The analysis of promoter cis-acting elements suggested that DfCCoAOMTs might be important for photosynthesis, ABA/MeJA responses, drought stress and lignin synthesis. We then confirmed that the expression levels of DfCCoAOMT2/5/6/8/9/14/15 were regulated by ABA/MeJA signaling. In addition, overexpression of DfCCoAOMT14 in transgenic plants significantly increased the lignin content, xylem thickness and drought resistance of plants. Our findings revealed that DfCCoAOMT14 can be a candidate gene that is involved in the drought response and lignin synthesis pathway in plants, which could contribute to the genetic improvement of many important traits in D. farinosus and other species.

The fruit morphometric variation and fruit type evolution of the stone oaks (Fagaceae, Lithocarpus)

BackgroundThe great species diversity of Lithocarpus is associated with interspecific fruit morphological variation, represented by acorn (AC) and enclosed receptacle (ER) fruit types. Species representing both fruit types co-occur in the same forests and share two distribution centers in southern China and southeastern Asia. The predation selection hypothesis suggests that the fruit morphological mechanical trade-off between two fruit types could represent divergent dispersal strategies under varied predation pressures. By integrating phylogenetic construction with fruit morphometric study, we tried to verify the predation selection hypothesis and elucidate the fruit type evolution of Lithocarpus, which is critical in interpreting the distribution and diversification of the genus.ResultsWe identified the functional trade-off between the two fruit types: ER species have bigger seeds which are enclosed mainly by receptacle representing stronger physical defense; whereas the seeds of AC species are smaller and enclosed mainly by thin pericarp representing lower mechanical protection. Despite some reversals from ER back to AC, the ancestral state reconstruction in combination with thermal analysis supports the hypothesis that ER is the derived fruit type from AC-like ancestors independently across all clades.ConclusionOur results support the predation selection hypothesis by verifying the mechanical trade-off between the two fruit types. We propose a divergent selection theory for the two fruit types: the seed size and mechanical defense of AC species become smaller, whereas those of ER species become larger and require more morphological modifications in the receptacle. This signified the importance of the receptacle in differentiating the two fruit types and in the fruit morphological modification through evolutionary time. We found that the ER-type species evolved independently in all clades and across varied climates from tropical to warm temperate regions. As ER fruits are products of convergent evolution, we propose to examine the predation and dispersal variation between two fruit types in the future to verify whether predation selection is the reason behind fruit type evolution of the stone oaks.

Structure vs. chemistry: Alternate mechanisms for controlling leaf microbiomes.

The analysis of phyllosphere microbiomes traditionally relied on DNA extracted from whole leaves. To investigate the microbial communities on the adaxial (upper) and abaxial (lower) leaf surfaces, swabs were collected from both surfaces of two garden plants, Rhapis excelsa and Cordyline fruticosa. Samples were collected at noon and midnight and at five different locations to investigate if the phyllosphere microbial communities change with time and location. The abaxial surface of Rhapis excelsa and Cordyline fruticosa had fewer bacteria in contrast to its adaxial counterpart. This observation was consistent between noon and midnight and across five different locations. Our co-occurrence network analysis further showed that bacteria were found almost exclusively on the adaxial surface while only a small group of leaf blotch fungi thrived on the abaxial surface. There are higher densities of stomata on the abaxial surface and these openings are vulnerable ports of entry into the plant host. While one might argue about the settling of dust particles and microorganisms on the adaxial surface, we detected differences in reactive chemical activities and microstructures between the adaxial and abaxial surfaces. Our results further suggest that both plant species deploy different defence strategies to deter invading pathogens on the abaxial surface. We hypothesize that chemical and mechanical defence strategies evolved independently for harnessing and controlling phyllosphere microbiomes. Our findings have also advanced our understanding that the abaxial leaf surface is distinct from the adaxial surface and that the reduced microbial diversity is likely a consequence of plant-microbe interactions.

Experimental Study on the Tridacna squamosa Shell: Distinctive Structure and Mechanical Behavior.

Tridacna squamosa, Lamarck, 1819 (Bivalvia Cardiida Cardiidae, known as the fluted giant clam) is one of the largest-sized bivalve shells, which is equipped with a strong and tough bioceramic shell to effectively protect itself from the attack of predators. To better understand the mechanical defense mechanism, the relationship between the microstructure, composition, and mechanical properties of the Tridacna squamosa shell was investigated. We find that the Tridacna squamosa shell is composed of aragonite CaCO3 and a small portion of organic matter, which are well-arranged, assembling a multiscale, inhomogeneous, and anisotropic structure. Three levels of microstructure units are identified, including the smallest aragonite rods, medium sheets, and block-like lamellae. Such multiscale structures are the main contributor to creating abundant fracture surfaces much larger than the case for single mineral components, leading to multiple toughening mechanisms observed in Vickers indentation experiments, such as pulled-out of mineral platelet and crack deflection. The material inhomogeneity in the cross-sectional direction indicates that the material is stronger at the inner layer than that at the outer layer, which also facilitates an effective defense against the predator attack. This study may provide insights into the design of biomaterials with the desired mechanical properties.

No evident sex-biased herbivory but phenological and interannual variation in Fuchsia parviflora (Onagraceae) a dioecious Neotropical shrub

Herbivory may have a great impact in plants, reducing plant biomass and fitness. Herbivory patterns may differ among genders in dioecious species, affecting male and female plants differentially, and it has been suggested this is a consequence of differences in resource allocation among genders. In this study, we evaluated herbivory intensity and mechanical defenses among genders during two years and during different phenological stages in populations of Fuchsia parviflora, a dioecious shrub. We also evaluated generalist and specialist herbivore gender preferences through a cafeteria experiment. No evident herbivory patterns were detected among genders using both the proportion of leaves affected by herbivory and the proportion of leaf area removed, except during one year in two populations where females had a significantly higher proportion of leaves affected by herbivory. This pattern is similar to the specialist herbivore preference detected in the cafeteria experiment. We also found significant differences in herbivory intensity among phenological stages, populations, and years, highlighting the relevance of continuous sampling to depict the general patterns of herbivory in dioecious plants.

Influence of Abiotic and Biotic Stressors on the Sensitivity Defenses of Mimosa striglliosa

In plants, chemical and mechanical traits are involved in the defense against environmental stressors. In the case of Mimosa plants, touch-sensitive responses through leaf-closure provide a unique form of mechanical defense. While past research has shown that the impacts of stressors such as competition or short-term drought may cause the chemical defenses in plants to increase or decrease, it is unknown how the interaction of these stressors may influence the efficiency of touch-sensitive responses. In this study, we hypothesized that the touch-sensitive responses of Mimosa strigillosa would strongly differ from regularly watered individuals when subjected to short-term drought. Additionally, we hypothesized that competition would hinder the touch-sensitive response, particularly from competitors in closely related taxa. To test these hypotheses, an experimental design was performed with three competition groups of Mimosa. In each competition group, half of the individuals were subjected to drought conditions. Plants were then subjected to a tactile stimulus in a greenhouse environment, with the degree of leaf closure being measured as an estimate of recovery. Drought was found to be a significant factor of both the rate of change of leaf closure, and the degree of leaf closure.

The effect of structural curvature on the load-bearing characteristics of biomechanical elements

Miniature, sharped-edge, curved-shape biomechanical elements appear in various biological systems and grant them diverse functional capabilities, such as mechanical defense, venom injection, and frictional support. While these biomechanical elements demonstrate diverse curved shapes that span from slightly curved needle-like elements (e.g., stingers), through moderately curved anchor-like elements (e.g., claws), to highly curved hook-like elements (e.g., fangs)—the curvature effect on the load-bearing capabilities of these biomechanical elements are yet mostly unknown. Here, we employ structural-mechanical modeling to explore the relationships between the curved shapes of biomechanical elements on their local deformation mechanisms, overall elastic stiffness, and reaction forces on a target surface. We found that the curvature of the biomechanical element is a prime modulator of its load-bearing characteristics that substantially affect its functional capabilities. Slightly curved elements are preferable for penetration states with optimal load-bearing capabilities parallel to their tips but possess high directional sensitivity and degraded capabilities for scratching states; contrary, highly curved elements are suitable for combined penetration-scratching states with mild directional sensitivity and optimal load-bearing capabilities in specialized angular orientation to their tips. These structural-mechanical principles are tightly linked to the intrinsic functional roles of biomechanical elements in diverse natural systems, and their synthetic realizations may promote new engineering designs of advanced biomedical injections, functional surfaces, and micromechanical devices.