Epicuticular Wax Research Articles

Pollen and Leaf Micromorphological Characteristics of Spiny Almonds (Prunus subgenus Amygdalus) in Iran.

This study investigates the micromorphological characteristics of pollen grains and leaf epidermal cells from 20 accessions across four species of spiny almonds using scanning electron microscopy. Thirteen quantitative traits of pollen grains, including exine sculpturing, were analyzed alongside qualitative features such as shape, exine sculpture type, and aperture type. Additionally, four quantitative and five qualitative features of the leaf epidermis were examined, focusing on cuticular ornamentation patterns, types of epicuticular wax, and stomatal measurements. The pollen grains were found to be isopolar monads, radially symmetric, medium-sized, varying from prolate spheroidal to prolate, and exhibiting 3-colporate to 3-colpate structures. The exine sculpturing was generally striate with short and long ridges, with or without perforations, and could be classified into three types. Notably, in the Isfahan population of Prunus lycioides and the North Khorasan population of Prunus spinosissima, the exine sculpture types were distinctly different, being rugulate and reticulate, respectively. Multivariate statistical analysis identified equatorial diameter, colpus length and width, and ridge width as key diagnostic markers for species identification within spiny almonds. Principal component analysis and hierarchical clustering further highlighted the significance of stomatal length, cuticular ornamentation patterns, and epicuticular wax types in differentiating among taxa. We conclude that groupings recognized in recent classifications of the subgenus Amygdalus (spiny almonds) remain challenging to delineate solely based on palynological data, as diverse pollen types are present across different clades and subclades. Furthermore, micromorphological leaf traits proved valuable in distinguishing certain spiny almond taxa, and the traits of epidermal cells may reflect the ecological adaptations of spiny almond species.

A Review on the Utilization of Epicuticular Wax from Plant Samples as a Hydrophobic Surface Coating Agent

A Review on the Utilization of Epicuticular Wax from Plant Samples as a Hydrophobic Surface Coating Agent

Arabidopsis DREB26/ERF12 and its close relatives regulate cuticular wax biosynthesis under drought stress condition.

Land plants have evolved a hydrophobic cuticle on the surface of aerial organs as an adaptation to ensure survival in terrestrial environments. Cuticle is mainly composed of lipids, namely cutin and intracuticular wax, with epicuticular wax deposited on plant surface. The composition and permeability of cuticle have a large influence on its ability to protect plants against drought stress. However, the regulatory mechanisms underlying cuticular wax biosynthesis in response to drought stress have not been fully elucidated. Here, we identified three AP2/ERF transcription factors (DREB26/ERF12, ERF13 and ERF14) involved in the regulation of water permeability of the plant surface. Transmission electron microscopy revealed thicker cuticle on the leaves of DREB26-overexpressing (DREB26OX) plants, and thinner cuticle on the leaves of transgenic plants expressing SRDX repression domain-fused DREB26 (DREB26SR). Genes involved in cuticular wax formation were upregulated in DREB26OX and downregulated in DREB26SR. The levels of very-long chain (VLC) alkanes, which are a major wax component, increased in DREB26OX leaves and decreased in DREB26SR leaves. Under dehydration stress, water loss was reduced in DREB26OX and increased in DREB26SR. The erf12/13/14 triple mutant showed delayed growth, decreased leaf water content, and reduced drought-inducible VLC alkane accumulation. Taken together, our results indicate that the DREB26/ERF12 and its closed family members, ERF13 and ERF14, play an important role in cuticular wax biosynthesis in response to drought stress. The complex transcriptional cascade involved in the regulation of cuticular wax biosynthesis under drought stress conditions is discussed.

Impact of saflufenacil and glyphosate-based herbicides on the morphoanatomical and development of Enterolobium contortisiliquum (Vell.) Morong (Fabaceae): new insights into a non-target tropical tree species.

The unregulated use and improper management of herbicides can cause negative effects on non-target species and promote changes in biological communities. Therefore, the current study is aimed at understanding morphoanatomical responses and effects on seedling development induced by the herbicides glyphosate and saflufenacil in Enterolobium contortisiliquum, a non-target tropical species. The plants were cultivated in a greenhouse and subjected to herbicides at doses of 0, 160, 480, and 1440g a.e ha-1 for glyphosate, and 0, 25, 50, and 100g a.i ha-1 for saflufenacil. We conducted visual and morphological assessments over 90days post-application. Leaf samples were collected 12days after the application for anatomical analysis, and we also performed a micromorphometric analysis of the leaf tissues. Biomarkers of phytotoxicity were identified in plants exposed to both herbicides, even at the lowest doses, including in leaves without visual symptoms. The main morphological alterations were the decrease in growth, stem diameter, and dry mass. Furthermore, the leaves and stems visually exhibited chlorosis and necrosis. Both herbicides triggered anatomical modifications such as significant changes (p < 0.05) in the thickness of leaf tissues, hypertrophy, cell collapse, and changes in epicuticular waxes. However, the alterations induced by glyphosate were more widespread compared to saflufenacil, encompassing alterations in the root system. We confirmed that the different mechanisms of action of each herbicide and the existence of an underground reserve system in this species are intrinsically linked to the morphological and developmental responses described. Our findings suggest that E. contortisiliquum could be a potential bioindicator species for these herbicides in the environment, even at concentrations lower than those typically recommended for field application.

A critical review of the factors influencing pre‐harvest sprouting of wheat

AbstractPre‐harvest sprouting (PHS) is a global issue affecting a multitude of crops, including wheat (Triticum aestivum L.). The combination of conducive conditions and a lack of genetic seed dormancy results in the sprouting of intact grain at or prior to harvesting. The initiation of germination synthesizes gibberellic acid resulting in the activation of the alpha‐amylase synthesis via a calcium‐dependent signal transduction pathway. Alpha‐amylase synthesized via this pathway degrades the endosperm, decreasing bread‐making quality. A commonly used indicator for bread‐making quality is the Hagberg Falling Number. Environmental, phenotypic, genetic, and management factors influence the susceptibility of wheat to PHS. Rainfall, temperature, and relative humidity are commonly associated with PHS. The combination of these conditions results in the greatest severity of PHS. Morphological features such as awns and epicuticular waxes may increase the quantity of rainfall retained against the grain, increasing the risk of PHS. Similarly, management factors such as fertilization and fungicide application also may increase the risk of PHS occurring. Further research is necessary to understand the mechanisms and impact of management factors on PHS. Additionally, further investigations are needed to explore how environmental and genotypic interactions affect PHS susceptibility.

Response of the flag leaf for Moroccan bread wheat varieties in the field, highlighting its biochemical composition in its resistance mechanism against yellow rust

This investigation aimed to assess the responsiveness of fourteen Moroccan bread wheat varieties to yellow rust induced by Puccinia striiformis tritici (Pst) in comparison with a susceptible variety ‘Amal’ through natural inoculation in the field, employing a Randomized Complete Block Design (RCBD). A comprehensive evaluation, encompassing 20 variables related to epidemiological, phenological, morphological, and physicochemical parameters, was conducted. In elucidating the role of the leaf in wheat resistance to stripe rust, the mineral and organic composition was scrutinized using sophisticated molecular detection techniques—Fourier Transform Infrared Spectroscopy (FTIR) and Atomic Absorption Spectroscopy (AAS). These two methodologies, recognized for their efficacy, facilitated the measurement of varying concentrations of lipids and carboxylic esters in the epicuticular wax on the adaxial flag leaf. Additionally, the quantity of essential minerals was determined. The outcomes revealed distinct responses among bread wheat varieties to stripe rust, with ‘Faiza’, ‘Bandera’, and ‘Resulton’ demonstrating heightened resistance, manifesting severity values below 15%. Conversely, ‘Amal’ exhibited the lowest level of resistance. Furthermore, lipid concentration reached its pinnacle in ‘Faiza’, ‘Bandera’ and ‘Resulton’ while ‘Amal’ displayed the lowest lipid levels. Severity exhibited a very weak correlation with Zn, weak correlations with Cu, and moderate correlations with Ca and K (p&lt;0.05). This study provides valuable insights guiding future research endeavours aimed at enhancing the genetic traits of these elite cultivars for integration into Morocco’s cereals program.

Occurrences of Deposited Polycyclic Aromatic Hydrocarbons in Wax of Plant Leaves Using Laser Scanning Microscopy and Gas Chromatography–Mass Spectrometry

The knowledge of the deposition fate of ambient polycyclic aromatic hydrocarbons (PAHs) on plant leaves is limited. To fill in this knowledge gap, this study strives to observe the intermolecular complex between the polycyclic aromatic hydrocarbons and epicuticular wax of plant leaves using laser scanning microscopy. Epicuticular wax refers to a type of organic mixture that covers the outermost layer of leaves. The leaves of 20 tree species were collected in Beijing in July 2023. The concentrations of 31 PAHs were quantified by gas chromatography–mass spectrometry. Furthermore, the intermolecular complexes of polycyclic aromatic hydrocarbons and epicuticular wax were found with a fluorescence spectrofluorometer and laser scanning microscopy. The levels of total PAHs across 20 tree species ranged from 12.4 ng g−1 to 68.4 ng g−1. Differences in the amounts of total PAHs across tree leaves were observed, which may be ascribed to the differences in leaf surface across tree types. The higher concentration of low-molecular-weight PAHs was found in leaves compared to high-molecular-weight PAHs. The fluorescence spectrofluorometer identified the formation of a new intermolecular complex with fluorescence emission at an excitation wavelength of 340 nm between PAHs and epicuticular wax relative to PAHs. We used laser scanning microscopy with a 405 nm laser for excitation to observe the new intermolecular complex of PAHs and epicuticular wax on the stomata and epicuticular wax of leaves. This study found the intermolecular complex of PAHs on the surface of leaves in situ, which provides important information about the deposition fate of ambient PAHs.

Impact of phenology, brown midrib (BMR), seed treatment, and herbivory on epicuticular wax content and fall armyworm (Spodoptera frugiperda) feeding in sorghum-sudangrass (Sorghum xdrummondii)

In crop production, management strategies have historically relied upon chemical control to mitigate insect pest pressures. As resistance to pesticides grows at an alarming rate, and as non-target effects are found more frequently, the search for sustainable, novel pest management strategies has become more important. Plants are equipped with diverse physical and chemical defenses against insect pests. Among these physical defenses, epicuticular waxes serve as an important first line of defense. Yet, how these chemical control methods such as seed treatment affects epicuticular waxes is underexplored. Brown midrib (BMR) is a host-plant trait from a recessive gene that affects the monolignol biosynthetic pathway, reducing lignin content, and presents as a gene of interest for evaluation as a form of pest management. Sorghum-sudangrass, Sorghum x drummondii, is an economically important forage crop with BMR; however, the effects of BMR have primarily been studied in animal agriculture and its effects on insects is largely unknown. In addition, how BMR affects epicuticular waxes is also unknown. This study aims to understand how the quantity of epicuticular wax in Sorghum x drummondii is affected by chemical control (seed treatments), BMR, phenological stages, and how wax affects a polyphagous, destructive pest, fall armyworm, Spodoptera frugiperda (FAW). Through wax quantification and FAW feeding induction and wax added artificial diet experiments, we show that while BMR and seed treatment does not affect wax content, plant phenology affects wax, and wax is induced by FAW feeding and has negative consequences for caterpillar growth.

Effects of Different Shade Treatments on the Epidermal Wax Deposition of Hosta Genotypes with Different Glaucousness of Leaf Surface

Epidermal wax is strategically situated at the interface between plants and air; therefore, it plays a key role in plants’ interactions with their surroundings. It is also unstable and susceptible to light intensity. Hosta plants are shade-loving herbs with admirable flowers and leaves. Hosta ‘Halcyon’ and Hosta ensata F. Maek. are two species of Hosta with a glaucous and a glossy appearance, respectively. Light intensity can affect the composition of epicuticular wax on the leaf surface, which influences the leaf color phenotype and ornamental value. In this paper, the crystal micromorphology, content, and components of epicuticular wax on the leaves of two species of Hosta under different light conditions (10%-, 30%-, 50%-, 70%-, and 100%-intensity sunlight, relative light intensity (RLI)) have been studied using pot experiments. The results indicate that the epicuticular wax crystals of H. ‘Halcyon’ and H. ensata are tubular and platelet-like, respectively. The wax crystals of H. ‘Halcyon’ melted and formed a thick crust under 100% RLI, and those of H. ensata melted and formed a thick crust under 70% and 100% RLI conditions. The primary ingredients of the epicuticular wax of the two species of Hosta contained primary alcohols, alkanes, fatty acids, and esters; β-diketones were only detected in H. ‘Halcyon’. The quantity of epicuticular wax of H. ‘Halcyon’ reduced at first and then increased with an RLI increase, achieving its lowest value at 50% RLI, but that of H. ensata declined little by little. The amounts of C28 primary alcohols, C31 alkanes, and C18 fatty acids were significantly higher than those of other carbon atoms in the two genotypes of Hosta. The C31β-diketones content decreased with the increase in light intensity, which caused the white frost phenotype to gradually weaken in H. ‘Halcyon’.

The dominant white color trait of the melon fruit rind is associated with epicuticular wax accumulation.

Microscopic analyses and chemical profiling demonstrate that the white rind phenotype in melon fruit is associated with the accumulation of n-alkanes, fatty alcohols, aldehydes and wax esters. Serving as an indicator of quality, the rind (or external) color of fruit directly affects consumer choice. A fruit's color is influenced by factors such as the levels of pigments and deposited epicuticular waxes. The latter produces a white-grayish coating often referred to as "wax bloom". Previous reports have suggested that some melon (Cucumis melo L.) accessions may produce wax blooms, where a dominant white rind color trait was genetically mapped to a major locus on chromosome 7 and suggested to be inherited as a single gene named Wi. We here provide the first direct evidence of the contribution of epicuticular waxes to the dominant white rind trait in melon fruit. Our light and electron microscopy and gas chromatography-mass spectrometry (GC-MS) comparative analysis of melon accessions with white or green rinds reveals that the rind of melon fruit is rich in epicuticular waxes. These waxes are composed of various biochemical classes, including fatty acids, fatty alcohols, aldehydes, fatty amides, n-alkanes, tocopherols, triterpenoids, and wax esters. We show that the dominant white rind phenotype in melon fruit is associated with increased accumulation of n-alkanes, fatty alcohols, aldehydes and wax esters, which are linked with the deposition of crystal-like wax platelets on their surfaces. Together, this study broadens the understanding of natural variation in an important quality trait of melon fruit and promotes the future identification of the causative gene for the dominant white rind trait.

A Comparative Morphological and Anatomical Study of Juniperus communis L., J. sibirica Burgsd., and J. pygmaea K. Koch from Bulgaria.

Of the six juniper species found in the Bulgarian flora, three of the species have controversial taxonomic positions. Juniperus pygmaea K. Koch and J. sibirica Burgsd. exhibit similar morphological characteristics to J. communis L. in terms of leaves and female cones (galbuli). This is one of the reasons why, in the recent taxonomic developments, J. pygmaea and J. sibirica were united in a common variety of J. communis, namely, J. communis var. saxatilis. However, such a grouping of species in the Flora of Bulgaria has not been adopted. This study aimed to evaluate the degrees of similarity or difference in the structure of the leaves, galbuli, seeds, and pollen of J. communis, J. sibirica, and J. pygmaea using the methods of comparative anatomy by light microscope (LM) and scanning electron microscopy (SEM) observations and complex morphological measurements. The working hypothesis of this study was that the three species would show a different degree of similarity with each other, which would clarify their taxonomic rank. The morphological parameters revealed differences between the length/width ratio of galbuli and seed length of the three species, while leaf characteristics (length and width) showed a stronger resemblance between J. sibirica and J. pygmaea. Furthermore, a greater distinction between the leaves and galbili of J. communis and J. sibirica was found. The SEM analyses showed variations in the seed shape and spermoderm among the three species. The shape of J. communis seeds was oval and elongated, while J. pygmaea seeds were pear-shaped, and J. sibirica seeds were triangular-rhombic. The length and height of striations were diverse on seed spermoderm in the three species. The epicuticular waxes of leaves, located on the tips of the anticlinal walls of the elongated epidermal cells in J. pygmaea and J. communis, were oval, while they formed raised comb-like crystals in J. sibirica. The morphological, anatomical, and SEM analysis affirmed the accepted taxonomic status of J. communis and J. sibirica as independent species within the Bulgarian flora. Based on most of the analyzed parameters, J. pygmaea exhibits significant similarity with J. sibirica. Additionally, the similar habitats of these two species support the determination of J. pygmaea as a variety or form of J. sibirica rather than J. communis (J. sibirica forma pygmaea).

Herbarium specimens as tools for exploring the evolution of fatty acid-derived natural products in plants.

Plants synthesize natural products via lineage-specific offshoots of their core metabolic pathways, including fatty acid synthesis. Recent studies have shed light on new fatty acid-derived natural products and their biosynthetic pathways in disparate plant species. Inspired by this progress, we set out to develop tools for exploring the evolution of fatty-acid derived products. We sampled multiple species from all major clades of euphyllophytes, including ferns, gymnosperms, and angiosperms (monocots and eudicots), and we show that the compositional profiles (though not necessarily the total amounts) of fatty-acid derived surface waxes from preserved plant specimens are consistent with those obtained from freshly collected tissue in a semi-quantitative and sometimes quantitative manner. We then sampled herbarium specimens representing 57 monocot species to assess the phylogenetic distribution and evolution, of two fatty acid-derived natural products found in that clade: beta-diketones and alkylresorcinols. These chemical data, combined with analyses of 26 monocot genomes, revealed a co-occurrence (though not necessarily a causal relationship) between whole genome duplication and the evolution of diketone synthases from an ancestral alkylresorcinol synthase-like polyketide synthase. Limitations of using herbarium specimen wax profiles as proxies for those of fresh tissue seem likely to include effects from loss of epicuticular wax crystals, effects from preservation techniques, and variation in wax chemical profiles due to genotype or environment. Nevertheless, this work reinforces the widespread utility of herbarium specimens for studying leaf surface waxes (and possibly other chemical classes) and reveals some of the evolutionary history of fatty acid-derived natural products within monocots.

First line of defence: Eucalyptus leaf waxes influence infection by an aggressive fungal leaf pathogen.

Leaf epicuticular waxes provide important anatomical and chemical defences against fungi that infect leaves. In this study we analysed the leaf wax composition of Eucalyptus grandis × Eucalyptus urophylla hybrids with contrasting susceptibilities to Teratosphaeria leaf blight (TLB) caused by Teratosphaeria destructans, one of the most important foliar diseases of Eucalyptus. The Eucalyptus cuticular wax was extracted from non-inoculated and inoculated genotypes with different levels of susceptibility to TLB and analysed by gas chromatography-mass spectrometry. The results showed that a triterpenoid, cycloartenol (CAS), was abundant in a resistant genotype and that hexanedioic acid content increased in the resistant genotypes in response to T. destructans infection. In contrast, palmitic acid was significantly more abundant in the inoculated highly susceptible genotype. In-vitro and in-planta T.destructans spore germination assays with pure compounds, showed that CAS and hexanedioic acid significantly inhibited spore germination. Application of these two compounds to the leaves of a susceptible host also significantly increased resistance to infection. In contrast, palmitic acid promoted spore germination and, when applied to the leaves of a resistant genotype, increased colonization by the pathogen. This is the first study providing insights into differences in the leaf wax composition of hosts with different levels of susceptibility to T. destructans. It also showed that leaf wax compounds can modulate spore germination and, ultimately, host resistance to infection.

Sex, flies and flower trap: Trapping trichomes and their function in pollination

Abstract Trapping trichomes, a common trait found in protogynous trap flowers, are thought to enable interaction with pollinators, promoting both pollen removal and fruit set. However, this hypothesis has yet to be empirically confirmed. In this study, we experimentally tested whether trapping trichomes favour male and female functions in trap flowers. Using protogynous South American Aristolochia esperanzae trap flowers, we observed the temporal variation in both sexual functions and associated them with the wilting of the flower and trapping trichomes. Next, we described the trapping trichomes features associated with the capture, entrapment and release of pollinators. Finally, we used manipulative experiments involving trapping trichome removal to quantify their influence on pollinator entrapment, pollen removal and fruit set. While flowers wilted after the end of the female phase, the trapping trichomes only wilted some hours after pollen presentation, promoting a delay in the exit of pollinators, so they carried pollen. Trapping trichomes features, such as a density gradient towards the interior of the tube, unidirectional orientation and epicuticular waxes, may be important in the capture and entrapment of pollinators. Trapping trichome removal decreased drastically the probability of pollinator entrapment and pollen removal, leading to no fruit set. These results indicate that the evolution and maintenance of trapping trichomes in trap flowers probably occurred through selective pressures from both sexual functions and highlight their role in the functioning of this highly phenotypically specialized pollination system. Read the free Plain Language Summary for this article on the Journal blog.

Effect of light-induced changes in leaf anatomy on intercellular and cellular components of mesophyll resistance for CO2 in Fagus sylvatica.

Mesophyll resistance for CO2 diffusion (rm) is one of the main limitations for photosynthesis and plant growth. Breeding new varieties with lower rm requires knowledge of its distinct components. We tested new method for estimating the relative drawdowns of CO2 concentration (c) across hypostomatous leaves of Fagus sylvatica. This technique yields values of the ratio of the internal CO2 concentrations at the adaxial and abaxial leaf side, cd/cb, the drawdown in the intercellular air space (IAS), and intracellular drawdown between IAS and chloroplast stroma, cc/cbd. The method is based on carbon isotope composition of leaf dry matter and epicuticular wax isolated from upper and lower leaf sides. We investigated leaves from tree-canopy profile to analyse the effects of light and leaf anatomy on the drawdowns and partitioning of rm into its inter- (rIAS) and intracellular (rliq) components. Validity of the new method was tested by independent measurements of rm using conventional isotopic and gas exchange techniques. 73% of investigated leaves had adaxial epicuticular wax enriched in 13C compared to abaxial wax (by 0.50‰ on average), yielding 0.98 and 0.70 for average of cd/cb and cc/cbd, respectively. The rIAS to rliq proportion were 5.5:94.5% in sun-exposed and 14.8:85.2% in shaded leaves. cc dropped to less than half of the atmospheric value in the sunlit and to about two-thirds of it in shaded leaves. This method shows that rIAS is minor but not negligible part of rm and reflects leaf anatomy traits, i.e. leaf mass per area and thickness.

Wax Patterns, Textural Properties, and Quality Attributes of Two Eggplant (Solanum melongena L.) Cultivars during Storage

Two eggplant cultivars (Brigitte and Dalong) were stored under ambient conditions for 8 days to examine the postharvest quality and shelf life. Results indicated that the respiration rate, firmness and springiness, and nutritional quality of both eggplant cultivars decreased with the extension of shelf life. On the contrary, opposite trends were observed in weight loss, gumminess, and chewiness of eggplant fruits. In addition, the weight loss of ‘Brigitte’ eggplant fruits was 3.3% and 6.9% lower compared with ‘Dalong’ eggplant fruits at 4 and 8 days after storage. Thicknesses of epidermal cells and the stratum corneum, the epicuticular wax content of ‘Brigitte eggplant fruits increased by 42.9%, 766.7%, and 58.8% compared with ‘Dalong’ eggplant fruits, respectively, with a concomitant increase in the dense wax layer structure. In conclusion, the storage tolerance of ‘Brigitte’ eggplant fruits was higher than that of ‘Dalong’ eggplant fruits due to the higher epicuticular wax content and dense wax layer structure.

A GC-MS Metabolic Study on Lipophilic Compounds in the Leaves of Common Wheat Triticum aestivum L.

Common wheat (Triticum aestivum L.) is one of the most valuable cereal crops worldwide. This study examined leaf extracts of 30 accessions of T. aestivum and its subspecies using 48 h maceration with methanol by GC-MS and GCxGC-MS. The plants were grown from seeds of the wheat genetics collection of the Wheat Genetics Sector of the Institute of Cytology and Genetics, SB RAS. The analysis revealed 263 components of epicuticular waxes, including linear and branched alkanes, aliphatic alcohols, aldehydes, ketones, β-diketones, carboxylic acids and their derivatives, mono- and diterpenes, phytosterols, and tocopherols. Hierarchical cluster analysis and principal component analysis were used to identify and visualize the differences between the leaf extracts of different wheat cultivars. Three clusters were identified, with the leading components being (1) octacosan-1-ol, (2) esters of saturated and unsaturated alcohols, and (3) fatty acid alkylamides, which were found for the first time in plant extracts. The results highlight the importance of metabolic studies in understanding the adaptive mechanisms and increasing wheat resistance to stress factors. These are crucial for breeding new-generation cultivars with improved traits.

Anisotropic Superhydrophobic Properties Replicated from Leek Leaves.

A bio-inspired approach to fabricate robust superhydrophobic (SHB) surfaces with anisotropic properties replicated from a leek leaf is presented. The polydimethylsiloxane (PDMS) replica surfaces exhibit anisotropic wetting, anti-icing, and light scattering properties due to microgrooves replicated from leek leaves. Superhydrophobicity is achieved by a novel modified candle soot (CS) coating that mimics leek's epicuticular wax. The resulting surfaces show a contact angle (CA) difference of ≈30° in the directions perpendicular and parallel to the grooves, which is similar to the anisotropic properties of the original leek leaf. The coated replica is durable, withstanding cyclic bending tests (up to 10 000 cycles) and mechanical sand abrasion (up to 60g of sand). The coated replica shows low ice adhesion (10kPa) after the first cycle; and then, increases to ≈70kPa after ten icing-shearing cycles; while, anisotropy in ice adhesion becomes more evident with more cycles. In addition, the candle soot-coated positive replica (CS-coated PR) demonstrates a transmittance of ≈73% and a haze of ≈65% at the wavelength of 550nm. The results show that the properties depend on the replicated surface features of the leek leaf, which means that the leek leaf appears to be a highly useful template for bioinspired surfaces.

Relationship between Salmonella enterica attachment and leaf hydrophobicity, roughness, and epicuticular waxes: a focus on 30 baby-leaf salads.

The first step in the contamination of leafy vegetables by human pathogens is their attachment to the leaf surface. The success of this is influenced strongly by the physical and chemical characteristics of the surface itself (number and size of stomata, presence of trichomes and veins, epicuticular waxes, hydrophobicity, etc.). This study evaluated the attachment of Salmonella enterica to 30 baby-leaf salads and tested whether the differences found among them were related to the following leaf traits: hydrophobicity, roughness, and epicuticular waxes. Differences in susceptibility to contamination by S. enterica were found between the 30 baby-leaf salads investigated. The lowest attachment was found in wild lettuce (Lactuca serriola L.) and lamb's lettuce 'Trophy F1' (Valerianella locusta [L.] Laterr.), with values of 1.63 ± 0.39 Log(CFU/cm2) and 1.79 ± 0.54 Log(CFU/cm2), respectively. Attachment was correlated with hydrophobicity (measured as contact angle) (r = -0.39) and epicuticular waxes (r = -0.81) but not with roughness (r = 0.24). The most important wax components for attachment were alcohols and, in particular, the three-dimensional (3D) wax crystals of C26 alcohol, but fatty acids probably also had a role. Both these compounds increased hydrophobicity. The presence of thymol, whose antimicrobial properties are well known, was found in lamb's lettuce. The findings of this study can help to predict and control the attachment and contamination of leafy salads by enterobacteria. They also provide useful information for breeding programs aiming to develop cultivars that are less susceptible to human pathogens, enhancing the food safety of vegetables. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The Greasy Pole Syndrome in Alliaria petiolata (Brassicaceae): The Pubescence and Wax Coverage on Stems Reduce Invasion by Lasius niger Ants.

To reduce negative effects of floral visitation by ants, which do not serve as reliable cross-pollinators, some plants have developed a non-floral, stem-based defense mechanism called greasy pole syndrome. In the present study, we examined the effects of two surface features (trichomes and three-dimensional epicuticular wax coverage) on stems of Alliaria petiolata plants on visiting frequencies, travelled distances, and running velocities of Lasius niger ants. The experiments were performed with stem samples prepared from different (apical and basal) stem portions showing different surface morphologies (smooth control, covered by wax and trichomes + wax, respectively). The control, mechanically wiped stem samples lacking any surface features were significantly more often visited by ants, where they travelled significantly longer distances and moved with significantly higher velocities, compared to the intact stems. The apical and basal stem portions showed no significant differences in the measured parameters. Based on data obtained, we conclude about the main contribution of the wax to the greasy pole function of the A. petiolata stem via reduction of ant adhesion to the wax-bearing stem surface, whereas trichomes presumably serve as the first barrier for ants approaching usually from the ground level and protect the fragile wax coverage from an excessive deterioration.