Chemical composition of the epicuticular and intracuticular wax layers on adaxial sides of Rosa canina leaves

The Role of Fatty Acids from Plant Surfaces in the Infectivity of Colletotrichum fioriniae

Aqueous extracts derived from flowers stimulate germination, secondary conidiation, and appressorial formation of various latent fruit rotting fungi. Even raindrops passing over flowers accumulate sufficient activity to influence the infectivity of fruit rotting fungi. Using a spore germination bioassay, high levels of bioactivity were found in chloroform extracts from plant tissues, implicating the nonpolar components of the cuticle. The fatty acid (FA) and fatty acid methyl ester (FAME) composition (C9-C20) of blueberry and cranberry tissues as well as aqueous flower extracts were characterized using a gas chromatography-mass spectrometry (GC-MS) method. The FAs and FAMEs found in the plant extracts were then tested for bioactivity using a spore germination bioassay. The C16:0 and C18:2 FAs and FAMEs, as well as the C18:0 FAME and the C20:0 FA, all stimulated appressorial formation while the C10:0 FA stimulated secondary conidiation. The C10:0 and C16:0 FAs were the only two bioactive components also identified from the aqueous floral extracts of both blueberry and cranberry and are therefore considered as contributors to the bioactivity observed in these extracts. The aqueous extracts from surfaces other than flowers showed little or no activity, and it is speculated that the movement of FAs may be related to the level of polymerization and cutin polyester development in flowers versus other plant organs. This study highlights the importance of the bloom period for infection and that the apparent effects on host susceptibility may therefore depend on the availability of specific FAs or combinations thereof.

Investigating the Effects of Temperature, Relative Humidity, Leaf Collection Date, and Foliar Penetration on Leaf-Air Partitioning of Chlorpyrifos

Leaf-air partition coefficient (K_leaf-air) values are needed to understand and predict pesticide volatilization and persistence in agroecosystems. The objectives of this work were to measure K_leaf-air values and foliar penetration for the insecticide chlorpyrifos (as an active ingredient alone and in a pesticide formulation) on alfalfa (lucerne) leaves at a range of temperatures and relative humidities and when using leaves collected in different summer months. K_leaf-air values were measured using a solid-phase fugacity meter. A portion of the leaves were also used for foliar penetration experiments. K_leaf-air values for chlorpyrifos as an active ingredient alone decreased with temperature, while the effects of temperature on chlorpyrifos in the formulation were negligible. No correlations between K_leaf-air values and relative humidity were observed. Foliar penetration increased with temperature for chlorpyrifos both as an active ingredient and in the formulation. Increasing foliar penetration with temperature is attributed to increasing diffusion into inner leaf layers. Both volatilization and foliar penetration affect the measured K_leaf-air values, so understanding the link between these processes is necessary to predict K_leaf-air values. The leaf collection date had a substantial effect on the measured K_leaf-air values, highlighting the need for a better understanding of the role of leaf properties on K_leaf-air.

Vicariance Between Cercis siliquastrum L. and Ceratonia siliqua L. Unveiled by the Physical-Chemical Properties of the Leaves' Epicuticular Waxes

Classically, vicariant phenomena have been essentially identified on the basis of biogeographical and ecological data. Here, we report unequivocal evidences that demonstrate that a physical-chemical characterization of the epicuticular waxes of the surface of plant leaves represents a very powerful strategy to get rich insight into vicariant events. We found vicariant similarity between Cercis siliquastrum L. (family Fabaceae, subfamily Cercidoideae) and Ceratonia siliqua L. (family Fabaceae, subfamily Caesalpinoideae). Both taxa converge in the Mediterranean basin (C. siliquastrum on the north and C. siliqua across the south), in similar habitats (sclerophyll communities of maquis) and climatic profiles. These species are the current representation of their subfamilies in the Mediterranean basin, where they overlap. Because of this biogeographic and ecological similarity, the environmental pattern of both taxa was found to be very significant. The physical-chemical analysis performed on the epicuticular waxes of C. siliquastrum and C. siliqua leaves provided relevant data that confirm the functional proximity between them. A striking resemblance was found in the epicuticular waxes of the abaxial surfaces of C. siliquastrum and C. siliqua leaves in terms of the dominant chemical compounds (1-triacontanol (C30) and 1-octacosanol (C28), respectively), morphology (intricate network of randomly organized nanometer-thick and micrometer-long plates), wettability (superhydrophobic character, with water contact angle values of 167.5 ± 0.5° and 162 ± 3°, respectively), and optical properties (in both species the light reflectance/absorptance of the abaxial surface is significantly higher/lower than that of the adaxial surface, but the overall trend in reflectance is qualitatively similar). These results enable us to include for the first time C. siliqua in the vicariant process exhibited by C. canadensis L., C. griffithii L., and C. siliquastrum.

Soluble cuticular wax composition and antimicrobial activity of the fruits of Chaenomeles species and an interspecific hybrid

Plants of the genus Chaenomeles Lindl. (Rosaceae) naturally grow in Southeast Asia and represent the richest resource of biologically active compounds with beneficial properties for humans. Plants of C. japonica (Thunb.) Lindl. and C. speciosa (Sweet) Nakai species, and interspecific hybrid C. × superba (Frahm) Rehder (C. japonica × C. speciosa, Superba group) have been successfully introduced in the steppe zone of Ukraine and bear fruits. In this study, we evaluated chemical composition of fruit cuticular waxes and antimicrobial activity of fruit extracts. The soluble waxes were characterized using gas chromatography-mass spectrometry (GC-MS), and 26–36 compounds, representing 91.7–96.6% of the total soluble cuticular waxes, were identified. Waxes of Chaenomeles fruits belonged to six classes, namely fatty acids, alcohols, aldehydes, esters, ethers and alkanes. Aldehydes 7-hexadecenal and heptacosanal, and alkanes hexatriacontane and tetrapentacontane were the main constituents in the soluble cuticular waxes of C. speciosa and C. × superba fruits, accounting for more than half of the total contents. However, alkane tetrapentacontane, alcohol 8,10-hexadecadien-1-ol and heptacosanal prevailed in C. japonica fruit waxes. Isopropanolic fruit extracts exhibited dose-dependent antimicrobial activity against four Gram-negative bacteria, five Gram-positive bacteria and one fungal strain in the disc diffusion assay. In general, extracts from the Chaenomeles fruits demonstrated higher activity against Gram+ bacteria than Gram- strains. The strongest inhibiting activity was shown against Staphylococcus epidermidis (by the fruit extracts of C. × superba and C. speciosa), Micrococcus lysodeikticus and Candida albicans (both by C. × superba fruit extract). Results of the study confirmed accumulation of the bioactive compounds in the fruit waxes of different Chaenomeles species and antimicrobial ability of Chaenomeles fruits as well. These findings revealed the bioactive compounds in fruit cuticular waxes and suggested health-promoting properties of introduced Chaenomeles species.

Soluble cuticular wax composition and antimicrobial activity of the fruits of Chaenomeles species and an interspecific hybrid

Plants of the genus Chaenomeles Lindl. (Rosaceae) naturally grow in Southeast Asia and represent the richest resource of biologically active compounds with beneficial properties for humans. Plants of C. japonica (Thunb.) Lindl. and C. speciosa (Sweet) Nakai species, and interspecific hybrid C. × superba (Frahm) Rehder (C. japonica × C. speciosa, Superba group) have been successfully introduced in the steppe zone of Ukraine and bear fruits. In this study, we evaluated chemical composition of fruit cuticular waxes and antimicrobial activity of fruit extracts. The soluble waxes were characterized using gas chromatography-mass spectrometry (GC-MS), and 26–36 compounds, representing 91.7–96.6% of the total soluble cuticular waxes, were identified. Waxes of Chaenomeles fruits belonged to six classes, namely fatty acids, alcohols, aldehydes, esters, ethers and alkanes. Aldehydes 7-hexadecenal and heptacosanal, and alkanes hexatriacontane and tetrapentacontane were the main constituents in the soluble cuticular waxes of C. speciosa and C. × superba fruits, accounting for more than half of the total contents. However, alkane tetrapentacontane, alcohol 8,10-hexadecadien-1-ol and heptacosanal prevailed in C. japonica fruit waxes. Isopropanolic fruit extracts exhibited dose-dependent antimicrobial activity against four Gram-negative bacteria, five Gram-positive bacteria and one fungal strain in the disc diffusion assay. In general, extracts from the Chaenomeles fruits demonstrated higher activity against Gram+ bacteria than Gram- strains. The strongest inhibiting activity was shown against Staphylococcus epidermidis (by the fruit extracts of C. × superba and C. speciosa), Micrococcus lysodeikticus and Candida albicans (both by C. × superba fruit extract). Results of the study confirmed accumulation of the bioactive compounds in the fruit waxes of different Chaenomeles species and antimicrobial ability of Chaenomeles fruits as well. These findings revealed the bioactive compounds in fruit cuticular waxes and suggested health-promoting properties of introduced Chaenomeles species.

GC-MS analysis of cuticular waxes and evaluation of antioxidant and antimicrobial activity of Chaenomeles cathayensis and Ch. × californica fruits

Fruit extracts of the Chaenomeles species are a rich source of compounds having health-promoting properties, while their distribution between the species and cultivars varies significantly depending on both genotype and environmental threats. This study aimed at discovering antioxidant and antimicrobial potential of the secondary metabolites of fruit and waxes of fruit cuticular of introduced Ch. cathayensis and Ch. × californica plants. The sum of detected polyphenols in the isopropanolic fruit extracts varied slightly between the species, while significant excesses in indices were seen for both species peel extracts as compared to pulp extracts. Antimicrobial assays carried out by disc diffusion method showed notable activity of the fruit peel and pulp extracts of both species against all tested Gram-negative and Gram-positive bacterial strains, and two Candida strains as well. Pseudomonas aeruginosa strain was the most resistant to the action of both fruit extracts, especially peel extracts of Ch. cathayensis fruits. As identified by gas chromatography-mass spectrometry (GC-MS) assays, chloroformic extracts from the fruits of cuticular waxes of Ch. cathayensis and Ch. × californica contained six prevailing fractions: aldehydes, alkanes, alcohols, esters, fatty acids and various terpenoids. The predominant compounds were tetrapentacontane (21.8% of total amount) and heptacosanal (23.1% of total), respectively in the cuticular waxes of Ch. cathayensis and Ch. × californica. Cinnamaldehyde, cis-9-hexadecenal, hexadecanoic acid, oleic acid, olean-12-ene-3,28-diol (3. beta), lupeol, diisooctyl phthalate, 9-octadecenoic acid, 1,2,3-propanetriyl ester, 1,3,12-nonadecatriene-5,14-diol and some other identified compounds are well-known for their bioactivity, indicating the feasibility of studying the antimicrobial potential of plant fruits.

Developmental pattern of grapevine (Vitis vinifera L.) berry cuticular wax: Differentiation between epicuticular crystals and underlying wax

The grapevine berry surface is covered by a cuticle consisting of cutin and various lipophilic wax compounds. The latter build the main barrier for transpirational water loss and protect the fruit against environmental factors e.g. pests, mechanical impacts or radiation. The integrety of the fruit surface is one important key factor for post-harvest quality and storage of fruits. Nonetheless, the developmental pattern of cuticular wax was so far only investigated for a very limited number of fruits. Therefore, we performed comparative investigations on the compositional and morphological nature of epicuticular wax crystals and underlying wax during fruit development in Vitis vinifera. The main compound oleanolic acid belongs to the pentacyclic triterpenoids, which occur very early in the development in high amounts inside the cuticle. The amount increases until veraison and decreases further during ripening. In general, very-long chain aliphatic (VLCA) compounds are present in much smaller amounts and alcohols and aldehydes follow the same trend during development. In contrast, the amount of fatty acids constantly increases from fruit set to ripening while wax esters only occur in significant amount at veraison and increase further. Wax crystals at the fruit surface are solely composed of VLCAs and the morphology changes during development according to the compositional changes of the VLCA wax compounds. The remarkable compositional differences between epicuticular wax crystals and the underlying wax are important to understand in terms of studying grape-pest interactions or the influence of environmental factors, since only wax crystals directly face the environment.

Compositional, structural and functional cuticle analysis of Prunus laurocerasus L. sheds light on cuticular barrier plasticity

Barrier properties of the hydrophobic plant cuticle depend on its physicochemical composition. The cuticular compounds vary considerably among plant species but also among organs and tissues of the same plant and throughout developmental stages. As yet, these intraspecific modifications at the cuticular wax and cutin level are only rarely examined. Attempting to further elucidate cuticle profiles, we analysed the adaxial and abaxial surfaces of the sclerophyllous leaf and three developmental stages of the drupe fruit of Prunus laurocerasus, an evergreen model plant native to temperate regions. According to gas chromatographic analyses, the cuticular waxes contained primarily pentacyclic triterpenoids dominated by ursolic acid, whereas the cutin biopolyester mainly consisted of 9/10,ω-dihydroxy hexadecanoic acid. Distinct organ- and side-specific patterns were found for cuticular lipid loads, compositions and carbon chain length distributions. Compositional variations led to different structural and functional barrier properties of the plant cuticle, which were investigated further microscopically, infrared spectroscopically and gravimetrically. The minimum water conductance was highlighted at 1 × 10^-5 m s^-1 for the perennial, hypostomatous P. laurocerasus leaf and at 8 × 10^-5 m s^-1 for the few-month-living, stomatous fruit suggesting organ-specific cuticular barrier demands.

High mass resolution, spatial metabolite mapping enhances the current plant gene and pathway discovery toolbox

Understanding when and where metabolites accumulate provides important cues to the gene function. Mass spectrometry imaging (MSI) enables in situ temporal and spatial measurement of a large assortment of metabolites, providing mapping information regarding their cellular distribution. To describe the current state and technical advances using MSI in plant sciences, we employed MSI to demonstrate its significant contribution to the study of plant specialised metabolism. We show that coupling MSI with: (1) RNA interference (RNAi), (2) virus induced gene silencing (VIGS), (3) agroinfiltration or (4) samples derived from plant natural variation provides great opportunities to understand the accurate gene-metabolite relationship and discover novel gene-associated metabolites. This was exemplified in three plant species (i.e. tomato, tobacco and wheat) by mapping the distribution of metabolites possessing a range of polarities. In particular, we demonstrated that MSI is able to spatially map an entire metabolic pathway, including intermediates and final products, in the intricate biosynthetic route to tomato fruit steroidal glycoalkaloids. We therefore envisage MSI as a key component of the metabolome analysis arsenal employed in plant gene discovery strategies.

Environmentally responsive QTL controlling surface wax load in switchgrass

KEY MESSAGE

Quantitation of leaf surface wax on a population of switchgrass identified three significant QTL present across six environments that contribute to leaf glaucousness and wax composition and that show complex genetic × environmental (G × E) interactions. The C4 perennial grass Panicum virgatum (switchgrass) is a native species of the North American tallgrass prairie. This adaptable plant can be grown on marginal lands and is useful for soil and water conservation, biomass production, and as a forage. Two major switchgrass ecotypes, lowland and upland, differ in a range of desirable traits, and the responsible underlying loci can be localized efficiently in a pseudotestcross design. An outbred four-way cross (4WCR) mapping population of 750 F2 lines was used to examine the genetic basis of differences in leaf surface wax load between two lowland (AP13 and WBC) and two upland (DAC and VS16) tetraploid cultivars. The objective of our experiments was to identify wax compositional variation among the population founders and to map underlying loci responsible for surface wax variation across environments. GCMS analyses of surface wax extracted from 4WCR F0 founders and F1 hybrids reveal higher levels of wax in lowland genotypes and show quantitative differences of β-diketones, primary alcohols, and other wax constituents. The full mapping population was sampled over two seasons from four field sites with latitudes ranging from 30 to 42 °N, and leaf surface wax was measured. We identified three high-confidence QTL, of which two displayed significant G × E effects. Over 50 candidate genes underlying the QTL regions showed similarity to genes in either Arabidopsis or barley known to function in wax synthesis, modification, regulation, and transport.

Chemical profiles of cuticular waxes on various organs of Sorghum bicolor and their antifungal activities

Sorghum bicolor is widely cultivated in arid and semi-arid areas. This paper reports the chemical profiles of cuticular waxes on adaxial and abaxial sides of common leaf, flag leaf, sheath and stem from six sorghum cultivars and the variations of leaf cuticular waxes at seedling, jointing and filling stages. Then, the bioassay of leaf and sheath wax were evaluated against Penicillium sp and Alternaria alternata. The six sorghum cultivars had similar wax profiles. In total, eight wax compounds were identified, including fatty acids, aldehydes, primary alcohols, alkanes, secondary alcohols, ketones, sterols and minor triterpenoids. Leaf wax coverage increased from 2.2 to 3.1 μg/cm² at seedling stages to 6.5-14.0 μg/cm² at jointing and filling stages, respectively. The relative abundance of primary alcohols decreased from 51 to 62% at seedling stage to 17-33% at jointing stage whereas alkanes increased from 5-9% to 19-33%. Leaf was dominated with alkanes (28.4%) and aldehydes (28.4%), sheath with acids (42.8%), and stem with aldehydes (80.8%). Epicuticular wax of leaf and sheath contained higher proportions of alkanes whereas the intracuticular waxes contained higher proportions of sterols. The leaf wax improved the growth of Penicillium but reduced that of A. alternaria, whereas sheath wax reduced the growth of Penicillium but unchanged A. alternaria. The detailed sorghum wax profiles improve our understanding of the physiological roles of these waxes and their diversified potential usages in industries.

Structure-function analysis of the maize bulliform cell cuticle and its potential role in dehydration and leaf rolling

The hydrophobic cuticle of plant shoots serves as an important interaction interface with the environment. It consists of the lipid polymer cutin, embedded with and covered by waxes, and provides protection against stresses including desiccation, UV radiation, and pathogen attack. Bulliform cells form in longitudinal strips on the adaxial leaf surface, and have been implicated in the leaf rolling response observed in drought-stressed grass leaves. In this study, we show that bulliform cells of the adult maize leaf epidermis have a specialized cuticle, and we investigate its function along with that of bulliform cells themselves. Bulliform cells displayed increased shrinkage compared to other epidermal cell types during dehydration of the leaf, providing a potential mechanism to facilitate leaf rolling. Analysis of natural variation was used to relate bulliform strip patterning to leaf rolling rate, providing further evidence of a role for bulliform cells in leaf rolling. Bulliform cell cuticles showed a distinct ultrastructure with increased cuticle thickness compared to other leaf epidermal cells. Comparisons of cuticular conductance between adaxial and abaxial leaf surfaces, and between bulliform-enriched mutants versus wild-type siblings, showed a correlation between elevated water loss rates and presence or increased density of bulliform cells, suggesting that bulliform cuticles are more water-permeable. Biochemical analysis revealed altered cutin composition and increased cutin monomer content in bulliform-enriched tissues. In particular, our findings suggest that an increase in 9,10-epoxy-18-hydroxyoctadecanoic acid content, and a lower proportion of ferulate, are characteristics of bulliform cuticles. We hypothesize that elevated water permeability of the bulliform cell cuticle contributes to the differential shrinkage of these cells during leaf dehydration, thereby facilitating the function of bulliform cells in stress-induced leaf rolling observed in grasses.

Epicuticular wax lipid composition of endemic European Betula species in a simulated ontogenetic/diagenetic continuum and its application to chemotaxonomy and paleobotany

Plants are excellent climate indicators and their macro-remains or pollen accumulating in geological archives serve as recorders of environmental change. In Europe birch trees contribute importantly to Holocene plant successions. They constitute the dwarf species Betula nana and B. humilis, representing colder and two tree birches, B. pubescens and B. pendula indicative of more temperate climate. Birch pollen is highly similar preventing species differentiation. We obtained unambiguous chemotaxonomic differentiation of four European birch species via cuticular wax lipids. Dominating lipid classes in recent epicuticular birch waxes were n-alkanes (nC₂₃ to nC₃₃), n-alcohols and n-alkanoic acids (nC₂₀ to nC₃₂), and long-chain wax ester (nC₃₆ to nC₄₈) differing in amount and distribution. After plant senescence and in geological archives lipids undergo diagenetic alteration modifying the distributions found in recent plants. Long-chain wax esters via hydrolysis release bound n-alcohols and n-fatty acids, adding to their free analogues. Simulated release of bound lipids increased the pool of n-alcohol and n-fatty acids up to 400%. Such modification of primary lipid patterns is unaccounted for in most paleovegetation studies. Proceeding diagenesis, e.g. by decarboxylation will convert these functionalized primary and secondary lipids into their corresponding n-alkanes, the compound class mostly applied in paleoenvironment reconstruction. The simulated n-alkane pattern changed significantly, evidenced by an increase of mid-chain (nC_23,nC₂₅) homologues. Release of bound lipids may not only alter molecular but also isotopic composition, which may cause errors in paleoclimate reconstruction. We assessed the potential contribution of secondary (free lipid decarboxylation) and tertiary (bound lipid decarboxylation) wax metabolites and compared the cumulative n-alkane patterns with birch n-alkane distributions reported in the literature. Two statistically different patterns were separated, one dominated by primary, the other by secondary and tertiary formed n-alkanes. This may explain the inconsistency in previous birch wax analysis reported and needs consideration in paleoenvironment reconstruction.

A Permeable Cuticle, Not Open Stomata, Is the Primary Source of Water Loss From Expanding Leaves

High rates of water loss in young, expanding leaves have previously been attributed to open stomata that only develop a capacity to close once exposed to low humidity and high abscisic acid (ABA) levels. To test this model, we quantified water loss through stomata and cuticle in expanding leaves of Quercus rubra. Stomatal anatomy and density were observed using scanning electron microscopy. Leaves of Q. rubra less than 5 days after emergence have no stomata; therefore, water loss from these leaves must be through the cuticle. Once stomata develop, they are initially covered in a cuticle and have no outer cuticular ledge, implying that the majority of water lost from leaves in this phase of expansion is through the cuticle. Foliar ABA levels are high when leaves first expand and decline exponentially as leaves expand. Once leaves have expanded to maximum size, ABA levels are at a minimum, an outer cuticular ledge has formed on most stomata, cuticular conductance has declined, and most water loss is through the stomata. Similar sequences of events leading to stomatal regulation of water loss in expanding leaves may be general across angiosperms.

Exogenous hormones influence Brassica napus leaf cuticular wax deposition and cuticle function

Background

Cuticular waxes cover plant surface and play important roles in protecting plants from abiotic and biotic stresses. The variations of wax deposition and chemical compositions under changing environments have been shown to be related to plant adaptations. However, it is still not clear whether the wax depositions could be adjusted to increase plant adaptations to stressed conditions.

Methods

In this study, exogenous methyl jasmonate (MeJA), the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) and salicylic acid (SA) were applied to test their effects on cuticular wax deposition in two Brassica napus cultivars, Zhongshuang 9 (ZS9, low wax coverage ) and Yuyou 19 (YY19, high wax coverage). Next, we measured the water loss rate and the transcriptional expression of genes involved in wax biosynthesis as well as genes related to disease defense.

Results

Seven wax compound classes, including fatty acids, aldehydes, alkanes, secondary alcohols, ketones, and unbranched as well as branched primary alcohols, were identified in B. napus leaf wax mixtures. MeJA, SA and ACC treatments had no significant effect on total wax amounts in YY19, whereas ACC reduced total wax amounts in ZS9. Overall, hormone treatments led to an increase in the amounts of aldehydes and ketones, and a decrease of secondary alcohol in ZS9, whereas they led to a decrease of alkane amounts and an increase of secondary alcohol amounts in YY19. Concomitantly, both cultivars also exhibited different changes in cuticle permeability, with leaf water loss rate per 15 min increased from 1.57% (averaged across treatments) at 1.57% (averaged across treatments) at 15 min to 3.12% at 30 min for ZS9 (except for ACC treated plant) and decreased for YY19. MeJA-treated plants of both cultivars relatively had higher water loss rate per 15 min when compared to other treatments. Conclusion. Our findings that B. napus leaf wax composition and cuticle permeability are altered by exogenous SA, MeJA and ACC suggest that the hormone treatments affect wax composition, and that the changes in wax profiles would cause changes in cuticle permeability.

Evaluation of the Foliar Damage That Threatens a Millennial-Age Tree, Araucaria araucana (Molina) K. Koch, Using Leaf Waxes

A. araucana is an endemic species of the temperate forests from Chile and Argentina; protected in both countries and categorized as in danger of extinction. Individuals of this species have begun to show foliar damage (i.e., discoloration) in branches and upper parts. The discoloration begins from the base to the top and from the trunk to the branches with necrotic rings appearing; in some cases causing death; and is currently attributed to an as yet unknown disease. This study focuses on the first protective layer of plants against environmental stress and pathogens; known as leaf waxes. The abundance and distribution of three classes of leaf waxes (long chain fatty acids; alkanes and alcohols) were measured in healthy individuals of A. araucana from different sites and individuals that present foliar damage (sick individuals). In the case of sick individuals; their leaf waxes were measured considering the level of leaf damage; that is; leaves without; medium and full foliar damage. The most abundant class of leaf wax in both sick and healthy individuals was fatty acids; followed by alkanes and then alcohols; with common dominant chains; C28 fatty acid; C29 alkane and C24 alcohol. Sick individuals have higher abundances of alkanes and alcohols than healthy individuals. The leaves of sick individuals have lower values of distribution indices (the carbon preference index of fatty acids and average chain length of alkanes) as foliar damage increases that are interpreted as a reduction of in vivo biosynthesis of waxes. This is the first evidence of A. araucana response to a still unknown disease that is killing individuals of this endemic species.

Linseed Essential Oil - Source of Lipids as Active Ingredients for Pharmaceuticals and Nutraceuticals

Linseed - also known as flaxseed - is known for its beneficial effects on animal health attributed to its composition. Linseed comprises linoleic and α-linolenic fatty acids, various dietary fibers and lignans, which are beneficial to health because they reduce the risk of cardiovascular diseases, as well as cancer, decreasing the levels of cholesterol and relaxing the smooth muscle cells in arteries increasing the blood flow. Essential fatty acids from flax participate in several metabolic processes of the cell, not only as structuring components of the cell membrane but also as storage lipids. Flax, being considered a functional food, can be consumed in a variety of ways, including seeds, oil or flour, contributing to basic nutrition. Several formulations containing flax are available on the market in the form of e.g. capsules and microencapsulated powders having potential as nutraceuticals. This paper revises the different lipid classes found in flaxseeds and their genomics. It also discusses the beneficial effects of flax and flaxseed oil and their biological advantages as ingredients in pharmaceuticals and in nutraceuticals products.

An appraisal of cuticular wax of Calotropis procera (Ait.) R. Br.: Extraction, chemical composition, biosafety and application

Plastic and polythene as hydrophobic materials become a grave concern due to their non-biodegradable nature, cumbersome recycling and waste management. Cuticular wax derived from Calotropis procera is explored as an eco-friendly and safe hydrophobic material. The effects of duration of exposure to solvent, solvent type, size and side of the leaf on cuticular wax yield have been studied. Leaf with the smallest area (10 cm²-25 cm²) was found to be the most suitable to isolate the wax. GC-MS analysis of the wax revealed that the wax consists of mainly esters, alkane and alkene. Mitochondrial reductase (MTT) and lactate dehydrogenase (LDH) assay have been carried out on M5S cell line at various concentrations and the results indicate that up to 1 μg/ml (acetone as solvent) and 3 μg/ml (chloroform as solvent) use of wax has no toxic effect. To evaluate the hydrophobic potential of the wax in developing hydrophobic paper water regains and contact angle has been measured. The gain in hydrophobicity of the paper is evident from the rise in contact angle (≥90˚) of paper coated with wax. Scanning electron micrograph and FTIR spectra generated physical and chemical evidence of coating of wax on paper.

Chemical composition and water permeability of the cuticular wax barrier in rose leaf and petal: A comparative investigation

Cuticular wax is the main transpiration barrier against uncontrolled water loss for all aerial plant organs. This study presents water permeability and chemical composition of the cuticle on the petals and leaves of two cultivars of Rosa chinensis ('Movie star' and 'Tineke'). Numerous cultivar- and organ-specific differences, such as the water permeability and total cuticular wax, were detected among rose petals and leaves. Overall, the permeability to water is higher in petals than in leaves, varying between 1.8 × 10^-5 m s^-1 ('Tineke' leaves) and 1.0 × 10^-4 m s^-1 ('Tineke' petals). The cuticular wax coverage ranges from 4.9 μg cm^-2 ('Tineke' petals) to 13.2 μg cm^-2 ('Movie star' petals). The most prominent components of the waxes are n-alkanes with the odd-numbered chain lengths C₂₇ and C₂₉ in petals, and C₃₁ and C₃₃ in leaves. The lower water permeability of leaves is deduced to be associated with the higher weighted average chain length of their acyclic cuticular waxes. This study on transpiration via the cuticular wax barrier of the leaf and petal of rose provides further insight to link the chemical composition to the cuticular transpiration barrier properties.

Lipids: Source of Static Electricity of Regenerative Natural Substances and Nondestructive Energy Harvesting

It is familiar to everyone that human skin and hair easily lose electrons and cause static electricity as they undergo friction with other materials. Such natural regenerative substances take a high ranking in the triboelectric series. Even though the static electricity of regenerative natural substances has been a long-term curiosity in human history, it is not yet clear which of their components causes the positive static charges. This study reveals that lipid layers on the surface of regenerative substances (skin, hair, leaves, cells) and even synthetic lipids are responsible for this positive static electricity and shows that it is possible to manufacture lipid-based triboelectric nanogenerators (TENGs). Using the characteristic that lipids on leaves regenerate within a few hours, lipids from living tree leaves are collected, and lipid-based nondestructive TENGs are fabricated. The concept of energy-harvesting vines is also presented, which can generate electricity when they are wrapped loosely on living tree branches. This study suggests how to harvest electricity while preserving nature as it is.

The problem of misidentification between edible and poisonous wild plants: Reports from the Mediterranean area

Today, in many European countries, people are looking for wild edible plants to experience new tastes and flavors, by following the new trend of being green and environmentally friendly. Young borage and spinach leaves can be easily confused by inexpert pickers with those of other plants, including poisonous ones, such as Mandragora autumnalis Bertol. (mandrake) or Digitalis purpurea L. (foxglove), common in southern and northern Italy respectively. In the last twenty years, several cases of intoxication by accidental ingestion of mandrake and foxglove have been reported. The purpose of this work was to perform a pharmacognostic characterization of young leaves from borage, mandrake, foxglove and spinach, by micro-morphological, molecular and phytochemical techniques. The results showed that each of the three techniques investigated could be sufficient alone to provide useful information for the identification of poisonous species helping the medical staff to manage quickly the poisoned patients. However, the multi-disciplinary approach proposed could be very useful to asses the presence of poisonous plants in complex matrices, to build a database containing morphological, molecular and phytochemical data for the identification of poisonous species or in forensic toxicology, given their increasingly frequent use due to their low cost and relatively common availability.

Mechanical properties of cuticles and their primary determinants

Cuticles envelope primary surfaces of the above-ground portion of plants. They function as barriers to water movement and to gas exchange, and in pathogen defense. To serve as a barrier on growing organs, cuticles must remain intact but at the same time must accommodate ongoing growth. Minimizing cuticle failure has stimulated significant research on the cuticle's mechanical properties. The objective here is to review the literature on the mechanical properties of isolated fruit and leaf cuticles. Cuticles are viscoelastic polymers. Viscoelasticity results mainly from the cutin matrix. Impregnation by waxes, flavonoids, and cutan increases stiffness and strength but decreases extensibility. On the inner side, the cutin matrix is impregnated by cell wall polysaccharides, which are responsible for its elastic behavior. Across species, the maximum forces sustainable by hydrated cuticles in uniaxial tensile tests averaged 0.82 N (range 0.15-1.63 N), the maximum stresses averaged 13.2 MPa (range 2.0-29.0 MPa), the maximum strains averaged 8.8% (range 1.6-28.0%), and the moduli of elasticity averaged 224 MPa (range 60-730 MPa). Among the environmental factors, high temperature and hydration both decreased stiffness. Therefore, the mechanical properties of cuticles in vivo depend largely on the relative proportions of their constituents. These proportions change during development and are also affected by environmental factors such as temperature.

Surfactant-induced enhancement of droplet adhesion in superhydrophobic soybean (Glycine max L.) leaves

This study performed with soybean (Glycine max L.), one of the most important crops for human and animal nutrition, demonstrates that changes in the leaf surface structure can increase the adhesion of applied droplets, even on superhydrophobic leaves, to reduce undesirable soil contamination by roll-off of agrochemical formulations from the plant surfaces. The wettability and morphology of soybean (Glycine max L.) leaf surfaces before and after treatment with six different surfactants (Agnique^® SBO10 and five variations of nonionic surfactants) have been investigated. The leaf surface structures show a hierarchical organization, built up by convex epidermal cells (microstructure) and superimposed epicuticular platelet-shaped wax crystals (micro- to nanostructure). Chemical analysis of the epicuticular wax showed that 1-triacontanol (C₃₀H₆₁OH) is the main wax component of the soybean leaf surfaces. A water contact angle (CA) of 162.4° (σ = 3.6°) and tilting angle (TA) of 20.9° (σ = 10.0°) were found. Adherence of pure water droplets on the superhydrophobic leaves is supported by the hydrophilic hairs on the leaves. Agnique^® SBO10 and the nonionic surfactant XP ED 75 increased the droplet adhesion and caused an increase of the TA from 20.9° to 85° and 90°, respectively. Scanning electron microscopy showed that surfactants with a hydrophilic-lipophilic balance value below 10 caused a size reduction of the epicuticular wax structures and a change from Cassie-Baxter wetting to an intermediate wetting regime with an increase of droplet adhesion.

Arabidopsis ketoacyl-CoA synthase 16 (KCS16) forms C36 /C38 acyl precursors for leaf trichome and pavement surface wax

The aliphatic waxes sealing plant surfaces against environmental stress are generated by fatty acid elongase complexes, each containing a β-ketoacyl-CoA synthase (KCS) enzyme that catalyses a crucial condensation forming a new C─C bond to extend the carbon backbone. The relatively high abundance of C₃₅ and C₃₇ alkanes derived from C₃₆ and C₃₈ acyl-CoAs in Arabidopsis leaf trichomes (relative to other epidermis cells) suggests differences in the elongation machineries of different epidermis cell types, possibly involving KCS16, a condensing enzyme expressed preferentially in trichomes. Here, KCS16 was found expressed primarily in Arabidopsis rosette leaves, flowers and siliques, and the corresponding protein was localized to the endoplasmic reticulum. The cuticular waxes on young leaves and isolated leaf trichomes of ksc16 loss-of-function mutants were depleted of C₃₅ and C₃₇ alkanes and alkenes, whereas expression of Arabidopsis KCS16 in yeast and ectopic overexpression in Arabidopsis resulted in accumulation of C₃₆ and C₃₈ fatty acid products. Taken together, our results show that KCS16 is the sole enzyme catalysing the elongation of C₃₄ to C₃₈ acyl-CoAs in Arabidopsis leaf trichomes and that it contributes to the formation of extra-long compounds in adjacent pavement cells.

Low vapor pressure deficit reduces glandular trichome density and modifies the chemical composition of cuticular waxes in silver birch leaves

Cuticular wax layer is the first barrier against the outside environment and the first defense encountered by herbivores and pathogens. The effects of environmental factors on cuticular chemistry, and on the formation of glandular trichomes that account for the storage and secretion of lipophilic compounds to the leaf surface are poorly understood. Low vapor pressure deficit (VPD) has shown to reduce the nitrogen (N) status of plants. Thus, we studied the effects of elevated air humidity, indicated as VPD, and the effect of N fertilization on cuticular waxes and glandular trichome density in silver birch (Betula pendula Roth). Experiments were carried out in growth chambers with juvenile plants and in a long-term field experiment with older trees. Low VPD reduced the glandular trichome density in both experiments, in chamber and in field. The contents of the major triterpenoid and flavonoid aglycones correlated positively with glandular trichome density, which supports the role of trichomes in the exudation of secondary compounds to the leaf surface. A closer examination of the cuticular wax chemistry in the chamber experiment revealed that low VPD and N supply affected the composition of cuticular waxes, but not the total wax content. The deposition of different wax compounds followed a co-ordinated pattern in birch leaves, but different compound groups varied in their responses to N fertilization and low VPD. Low VPD reduced the hydrophobicity of cuticular waxes, as demonstrated by lower alkane content and less hydrophobic flavonoid profile in low VPD than in high VPD. Reduced hydrophobicity of the wax layer is presumed to increase leaf wettability. Together with reduced trichome density in low VPD it may enhance the susceptibility of trees to fungal pathogens and herbivores. High N supply under low VPD reduced the effect of low VPD on the cuticular wax composition. Total fatty acid content and the expression of β-amyrin synthase were lower under high N supply than under moderate N supply irrespective of VPD treatment. Nitrogen availability and decreasing VPD will modify leaf surface properties in silver birch and thereby affect tree defence against abiotic and biotic stress factors that emerge under climate change.

Cuticular Waxes of Arabidopsis thaliana Shoots: Cell-Type-Specific Composition and Biosynthesis

It is generally assumed that all plant epidermis cells are covered with cuticles, and the distinct surface geometries of pavement cells, guard cells, and trichomes imply functional differences and possibly different wax compositions. However, experiments probing cell-type-specific wax compositions and biosynthesis have been lacking until recently. This review summarizes new evidence showing that Arabidopsis trichomes have fewer wax compound classes than pavement cells, and higher amounts of especially long-chain hydrocarbons. The biosynthesis machinery generating this characteristic surface coating is discussed. Interestingly, wax compounds with similar, long hydrocarbon chains had been identified previously in some unrelated species, not all of them bearing trichomes.

Identification of Polyketides in the Cuticular Waxes of Triticum aestivum cv. Bethlehem

Cuticular waxes are complex mixtures consisting mostly of very-long-chain aliphatics with single, primary functional groups. However, the waxes of many plant species also include aliphatics with one or more functional groups residing on subterminal or mid-chain carbons. In the present work, the cuticular wax mixtures from flag leaf blades and peduncles of Triticum aestivum cv. Bethlehem were analyzed in a search for novel wax constituents with in-chain functionalities, potentially of polyketide origin. The structures of compounds belonging to six different compound classes were elucidated using gas chromatography-mass spectrometry of various derivatives. Among them, a series of 2,4-ketols was identified, with odd carbon numbers ranging from C₂₅ to C₃₇ and peaking at C₃₃. The analogous C₃₃ 2,4-diketone was identified as well, together with a pair of co-eluting C₃₁ mid-chain β-ketol isomers (16-hydroxyhentriacontan-14-one and 14-hydroxyhentriacontan-16-one), a pair of co-eluting C₃₀ mid-chain α-ketol isomers (15-hydroxytriacontan-14-one and 14-hydroxytriacontan-15-one), the corresponding C₃₀ 14,15-diketone, and a pair of co-eluting C₃₁ ketones (hentriacontan-14-one and hentriacontan-16-one). All newly discovered structures contain ketone functional groups, with similar C₁₃H₂₇ and C₁₅H₃₁ alkyl chains on either side of the functionalities, thus resembling the previously reported very-long-chain β-diketones dominating the wheat wax mixtures. Based on these structural characteristics, possible biosynthetic pathways leading to the newly identified polyketide-like compounds are proposed.

Composition of the epicuticular waxes coating the adaxial side of Phyllostachys aurea leaves: Identification of very-long-chain primary amides

The present study presents comprehensive chemical analyses of cuticular wax mixtures of the bamboo Phyllostachys aurea. The epicuticular and intracuticular waxes were sampled selectively from the adaxial side of leaves on young and old plants and investigated by gas chromatography-mass spectrometry and flame ionization detection. The epi- and intracuticular layers on young and old leaves had wax loads ranging from 1.7 μg/cm(2) to 1.9 μg/cm(2). Typical very-long-chain aliphatic wax constituents were found with characteristic chain length patterns, including alkyl esters (primarily C48), alkanes (primarily C29), fatty acids (primarily C28 and C16), primary alcohols (primarily C28) and aldehydes (primarily C30). Alicyclic wax components were identified as tocopherols and triterpenoids, including substantial amounts of triterpenoid esters. Alkyl esters, alkanes, fatty acids and aldehydes were found in greater amounts in the epicuticular layer, while primary alcohols and most terpenoids accumulated more in the intracuticular wax. Alkyl esters occurred as mixtures of metamers, combining C20 alcohol with various acids into shorter ester homologs (C36C40), and a wide range of alcohols with C22 and C24 acids into longer esters (C42C52). Primary amides were identified, with a characteristic chain length profile peaking at C30. The amides were present exclusively in the epicuticular layer and thus at or near the surface, where they may affect plant-herbivore or plant-pathogen interactions.

Localization of the Transpiration Barrier in the Epi- and Intracuticular Waxes of Eight Plant Species: Water Transport Resistances Are Associated with Fatty Acyl Rather Than Alicyclic Components

Plant cuticular waxes play a crucial role in limiting nonstomatal water loss. The goal of this study was to localize the transpiration barrier within the layered structure of cuticles of eight selected plant species and to put its physiological function into context with the chemical composition of the intracuticular and epicuticular wax layers. Four plant species (Tetrastigma voinierianum, Oreopanax guatemalensis, Monstera deliciosa, and Schefflera elegantissima) contained only very-long-chain fatty acid (VLCFA) derivatives such as alcohols, alkyl esters, aldehydes, and alkanes in their waxes. Even though the epicuticular and intracuticular waxes of these species had very similar compositions, only the intracuticular wax was important for the transpiration barrier. In contrast, four other species (Citrus aurantium, Euonymus japonica, Clusia flava, and Garcinia spicata) had waxes containing VLCFA derivatives, together with high percentages of alicyclic compounds (triterpenoids, steroids, or tocopherols) largely restricted to the intracuticular wax layer. In these species, both the epicuticular and intracuticular waxes contributed equally to the cuticular transpiration barrier. We conclude that the cuticular transpiration barrier is primarily formed by the intracuticular wax but that the epicuticular wax layer may also contribute to it, depending on species-specific cuticle composition. The barrier is associated mainly with VLCFA derivatives and less (if at all) with alicyclic wax constituents. The sealing properties of the epicuticular and intracuticular layers were not correlated with other characteristics, such as the absolute wax amounts and thicknesses of these layers.

Confocal laser scanning microscopy elucidation of the micromorphology of the leaf cuticle and analysis of its chemical composition

Electron microscopy techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM) have been invaluable tools for the study of the micromorphology of plant cuticles. However, for electron microscopy, the preparation techniques required may invariably introduce artefacts in cuticle preservation. Further, there are a limited number of methods available for quantifying the image data obtained through electron microscopy. Therefore, in this study, optical microscopy techniques were coupled with staining procedures and, along with SEM were used to qualitatively and quantitatively assess the ultrastructure of plant leaf cuticles. Leaf cryosections of Triticum aestivum (wheat), Zea mays (maize), and Lupinus angustifolius (lupin) were stained with either fat-soluble azo stain Sudan IV or fluorescent, diarylmethane Auramine O and were observed under confocal laser scanning microscope (CLSM). For all the plant species tested, the cuticle on the leaf surfaces could be clearly resolved in many cases into cuticular proper (CP), external cuticular layer (ECL), and internal cuticular layer (ICL). Novel image data analysis procedures for quantifying the epicuticular wax micromorphology were developed, and epicuticular waxes of L. angustifolius were described here for the first time. Together, application of a multifaceted approach involving the use of a range of techniques to study the plant cuticle has led to a better understanding of cuticular structure and provides new insights into leaf surface architecture.

Very-long-chain 3-hydroxy fatty acids, 3-hydroxy fatty acid methyl esters and 2-alkanols from cuticular waxes of Aloe arborescens leaves

The present work aimed at a comprehensive chemical characterization of the cuticular wax mixtures covering leaves of the monocot species Aloe arborescens. The wax mixtures were found to contain typical aliphatic compound classes in characteristic chain length distributions, including alkanes (predominantly C31), primary alcohols (predominantly C28), aldehydes (predominantly C32), fatty acid methyl esters (predominantly C28) and fatty acids (bimodal distribution around C32 and C28). Alkyl esters ranging from C42 to C52 were identified, and found to mainly contain C28 alcohol linked to C16-C20 acids. Three other homologous series were identified as 3-hydroxy fatty acids (predominantly C28), their methyl esters (predominantly C28), and 2-alkanols (predominantly C31). Based on structural similarities and homolog distributions, the biosynthetic pathways leading to these novel wax constituents can be hypothesized. Further detailed analyses showed that the A. arborescens leaf was covered with 15 μg/cm(2) wax on its adaxial side and 36 μg/cm(2) on the abaxial side, with 3:2 and 1:1 ratios between epicuticular and intracuticular wax layers on each side, respectively. Terpenoids were found mainly in the intracuticular waxes, whereas very-long-chain alkanes and fatty acids accumulated to relatively high concentrations in the epicuticular wax, hence near the true surface of the leaf.

Trimethylamine (fishy odor) adsorption by biomaterials: effect of fatty acids, alkanes, and aromatic compounds in waxes

Thirteen plant leaf materials were selected to be applied as dried biomaterial adsorbents for polar gaseous trimethylamine (TMA) adsorption. Biomaterial adsorbents were efficient in adsorbing gaseous TMA up to 100% of total TMA (100 ppm) within 24 h. Sansevieria trifasciata is the most effective plant leaf material while Plerocarpus indicus was the least effective in TMA adsorption. Activated carbon (AC) was found to be lower potential adsorbent to adsorb TMA when compared to biomaterial adsorbents. As adsorption data, the Langmuir isotherm supported that the gaseous TMA adsorbed monolayer on the adsorbent surface and was followed pseudo-second order kinetic model. Wax extracted from plant leaf could also adsorb gaseous TMA up to 69% of total TMA within 24 h. Another 27-63% of TMA was adsorbed by cellulose and lignin that naturally occur in high amounts in plant leaf. Subsequently, the composition appearing in biomaterial wax showed a large quantity of short-chain fatty acids (≤C18) especially octadecanoic acid (C18), and short-chain alkanes (C12-C18) as well as total aromatic components dominated in the wax, which affected TMA adsorption. Hence, it has been demonstrated that plant biomaterial is a superior biosorbent for TMA removal.

Electrochemistry-based chemotaxonomy in plants using the voltammetry of microparticles methodology

Characterization of vegetal taxa is achievedviacharacteristic voltammetric features displayed by leaf extracts.

Metabolic and functional diversity of saponins, biosynthetic intermediates and semi-synthetic derivatives

Saponins are widely distributed plant natural products with vast structural and functional diversity. They are typically composed of a hydrophobic aglycone, which is extensively decorated with functional groups prior to the addition of hydrophilic sugar moieties, to result in surface-active amphipathic compounds. The saponins are broadly classified as triterpenoids, steroids or steroidal glycoalkaloids, based on the aglycone structure from which they are derived. The saponins and their biosynthetic intermediates display a variety of biological activities of interest to the pharmaceutical, cosmetic and food sectors. Although their relevance in industrial applications has long been recognized, their role in plants is underexplored. Recent research on modulating native pathway flux in saponin biosynthesis has demonstrated the roles of saponins and their biosynthetic intermediates in plant growth and development. Here, we review the literature on the effects of these molecules on plant physiology, which collectively implicate them in plant primary processes. The industrial uses and potential of saponins are discussed with respect to structure and activity, highlighting the undoubted value of these molecules as therapeutics.

Natural insect and plant micro-/nanostructsured surfaces: an excellent selection of valuable templates with superhydrophobic and self-cleaning properties

Insects and plants are two types of organisms that are widely separated on the evolutionary tree; for example, plants are mostly phototrophic organisms whilst insects are heterotrophic organisms. In order to cope with environmental stresses, their surfaces have developed cuticular layers that consist of highly sophisticated structures. These structures serve a number of purposes, and impart useful properties to these surfaces. These two groups of organisms are the only ones identified thus far that possess truly superhydrophobic and self-cleaning properties. These properties result from their micro- and nano-scale structures, comprised of three-dimensional wax formations. This review analyzes the surface topologies and surface chemistry of insects and plants in order to identify the features common to both organisms, with particular reference to their superhydrophobic and self-cleaning properties. This information will be valuable when determining the potential application of these surfaces in the design and manufacture of superhydrophobic and self-cleaning devices, including those that can be used in the manufacture of biomedical implants.

Interaction of organic solvents with the epicuticular wax layer of wheat leaves

After foliar application, compounds that are not absorbed into leaves can be removed from the leaf surface by dipping or rinsing in dilutions of organic solvents in water. However, interactions between solvent mixtures and the epicuticular wax layer have received little attention, and information on potential physical and chemical intactness of the plant surface following application of solvents is limited. In this study, wheat leaves were dipped in organic solvents at different dilutions with water, and the major component of the leaf epicuticular wax layer, 1-octacosanol, was analyzed to assess damage to the wax layer. Dipping leaves in dilutions of organic solvent higher than 60% by volume resulted in only negligible or low levels of 1-octacosanol extraction, while no 1-octacosanol was detected in any mixtures containing less than 40% organic solvent. Furthermore, analysis of leaf surfaces by scanning electron microscopy showed structural intactness of the epicuticular wax layer when organic solvent mixtures were used. Therefore, our results demonstrate that the epicuticular wax layer of wheat leaves is not altered physically or chemically by organic solvent solutions up to 40% by volume. These findings validate the use of solvent washing procedures to assess unabsorbed compounds on wheat leaf surfaces.

Molecular organization of the nanoscale surface structures of the dragonfly Hemianax papuensis wing epicuticle

The molecular organization of the epicuticle (the outermost layer) of insect wings is vital in the formation of the nanoscale surface patterns that are responsible for bestowing remarkable functional properties. Using a combination of spectroscopic and chromatographic techniques, including Synchrotron-sourced Fourier-transform infrared microspectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS) depth profiling and gas chromatography-mass spectrometry (GCMS), we have identified the chemical components that constitute the nanoscale structures on the surface of the wings of the dragonfly, Hemianax papuensis. The major components were identified to be fatty acids, predominantly hexadecanoic acid and octadecanoic acid, and n-alkanes with even numbered carbon chains ranging from C14 to C30. The data obtained from XPS depth profiling, in conjunction with that obtained from GCMS analyses, enabled the location of particular classes of compounds to different regions within the epicuticle. Hexadecanoic acid was found to be a major component of the outer region of the epicuticle, which forms the surface nanostructures, and was also detected in deeper layers along with octadecanoic acid. Aliphatic compounds were detected throughout the epicuticle, and these appeared to form a third discrete layer that was separate from both the inner and outer epicuticles, which has never previously been reported.

Nanostructured liquid crystalline particles as an alternative delivery vehicle for plant agrochemicals

Agrochemical spray formulations applied to plants are often mixed with surfactants that facilitate delivery of the active ingredient. However, surfactants cause phytotoxicity and off-target effects in the environment. We propose the use of nanostructured liquid crystalline particles (NLCP) as an alternative to surfactant-based agrochemical delivery. For this, we have compared the application of commercial surfactants, di (2-ethylhexyl) sulfosuccinate and alkyl dimethyl betaine, with NLCP made from phytantriol, at concentrations of 0.1%, 1% and 5% on the adaxial surface of leaves of four plant species Ttriticum aestivum (wheat), Zea mays (maize), Lupinus angustifolius (lupin), and Arabidopsis thaliana. In comparison with the application of surfactants there was less phytotoxicity on leaves of each species following treatment with NLCP. Following treatment of leaves with NLCP analysis of cuticular wax micromorphology revealed less wax solubilization in the monocot species. The results clearly show that there are advantages in the use of NLCP rather than surfactants for agrochemical delivery.

Stomatal encryption by epicuticular waxes as a plastic trait modifying gas exchange in a Mediterranean evergreen species (Quercus coccifera L.)

The adaptive benefit of stomatal crypts remains a matter of controversy. This work studies the effect on gas exchange of cuticular rims that overarch the stomatal pore in the Mediterranean species Quercus coccifera L. growing under Mediterranean (lower relative humidities and high summer temperatures) or oceanic conditions (higher daily relative humidities and mild temperatures). After microscopic assessment of the leaf surfaces and stomatal architecture, the impact of the cuticular 'cup' on gas exchange was evaluated by employing three-dimensional finite element models. Here, we provide evidence for a high plasticity of the Q. coccifera cuticular cup, with much larger vents under oceanic conditions compared to small vents under Mediterranean conditions. This structure adds a substantial fixed resistance thereby strongly decreasing gas exchange under Mediterranean conditions. The cuticular cup, which also increases leaf internal humidity, might buffer the rapid changes in vapour pressure deficit (VPD) often observed under Mediterranean conditions. Since water loss of guard and adjacent epidermal cells regulates stomatal aperture, we suggest that this structure allows an efficient regulation of stomatal conductance and optimum use of resources under high VPD. This study provides evidence that plasticity of stomatal architecture can be an important structural component of hydraulic adaptation to different climate conditions.

Composition and physiological function of the wax layers coating Arabidopsis leaves: β-amyrin negatively affects the intracuticular water barrier

Plants prevent dehydration by coating their aerial, primary organs with waxes. Wax compositions frequently differ between species, organs, and developmental stages, probably to balance limiting nonstomatal water loss with various other ecophysiological roles of surface waxes. To establish structure-function relationships, we quantified the composition and transpiration barrier properties of the gl1 mutant leaf waxes of Arabidopsis (Arabidopsis thaliana) to the necessary spatial resolution. The waxes coating the upper and lower leaf surfaces had distinct compositions. Moreover, within the adaxial wax, the epicuticular layer contained more wax and a higher relative quantity of alkanes, whereas the intracuticular wax had a higher percentage of alcohols. The wax formed a barrier against nonstomatal water loss, where the outer layer contributed twice as much resistance as the inner layer. Based on this detailed description of Arabidopsis leaf waxes, structure-function relationships can now be established by manipulating one cuticle component and assessing the effect on cuticle functions. Next, we ectopically expressed the triterpenoid synthase gene AtLUP4 (for lupeol synthase4 or β-amyrin synthase) to compare water loss with and without added cuticular triterpenoids in Arabidopsis leaf waxes. β-Amyrin accumulated solely in the intracuticular wax, constituting up to 4% of this wax layer, without other concomitant changes of wax composition. This triterpenoid accumulation caused a significant reduction in the water barrier effectiveness of the intracuticular wax.