Amorphous Wax Research Articles

Alterations in paraffin wax crystal networks induced by asphaltenes and pour point depressants, investigated by atomic force microscopy

Wax crystallization in pipelines in cold environments is a key factor affecting flow assurance during crude oil production. Polar crude oil components, such as asphaltenes, and polymeric pour point depressants (PPDs) have been demonstrated to interact with wax during gelation and crystallization through complex formation during nucleation or crystal growth alteration which leads to co-crystallization. This study introduces a methodology based on atomic force microscopy (AFM) to characterize features of solid surfaces precipitated from model wax, wax-PPD, wax-asphaltene and asphaltene systems. Height data collected from AFM measurements enabled the quantification of modifications in crystal sizes and shapes induced by the presence of asphaltenes and PPDs. The 2D Fourier transform of the height was used to generate statistics for the frequency of height amplitude, revealing information about the pore size and the height patterns. A stiffness/elasticity analysis was used to calculate the Young Modulus of the upper layers. In wax and wax-asphaltene systems, two nano-scale layers with different Young Modulus profiles emerged. The nano-scale layer on the top was softer and corresponded to more amorphous wax crystal networks with trapped dissolved wax. The nano-scale layer on the bottom was stiffer, comprising of more crystalline structures, corresponding to wax crystals with lower deviations from full crystallinity, with properties independent of asphaltene concentration. A bilayer did not form in the presence of PPD, which prevented the formation of amorphous phases with trapped dissolved wax or gel. After a methodology for model systems was established, the focus moved to systems based on production wax i.e. recovered from deposits. This was complemented by a comparison between model precipitation conditions and precipitation by cold finger, resembling industrial processes. Results highlighted the effect of change in chemical composition on topography, elasticity and adhesion of the surface. AFM provided new insights into wax crystallization patterns in the presence of inhibitors, which can be used to quantify the extent of wax-inhibitor interactions and project it on production systems. The method could be used to explain macro-scale rheological properties of oils during flow assurance in the future.

Diffusion of volatile organics and water in the epicuticular waxes of petunia petal epidermal cells.

Plant cuticles are a mixture of crystalline and amorphous waxes that restrict the exchange of molecules between the plant and the atmosphere. The multicomponent nature of cuticular waxes complicates the study of the relationship between the physical and transport properties. Here, a model cuticle based on the epicuticular waxes of Petunia hybrida flower petals was formulated to test the effect of wax composition on diffusion of water and volatile organic compounds (VOCs). The model cuticle was composed of an n-tetracosane (C24 H50 ), 1-docosanol (C22 H45 OH), and 3-methylbutyl dodecanoate (C17 H34 O2 ), reflecting the relative chain length, functional groups, molecular arrangements, and crystallinity of the natural waxes. Molecular dynamics simulations were performed to obtain diffusion coefficients for compounds moving through waxes of varying composition. Simulated VOC diffusivities of the model system were found to highly correlate with in vitro measurements in isolated petunia cuticles. VOC diffusivity increased up to 30-fold in completely amorphous waxes, indicating a significant effect of crystallinity on cuticular permeability. The crystallinity of the waxes was highly dependent on the elongation of the lattice length and decrease in gap width between crystalline unit cells. Diffusion of water and higher molecular weight VOCs were significantly affected by alterations in crystalline spacing and lengths, whereas the low molecular weight VOCs were less affected. Comparison of measured diffusion coefficients from atomistic simulations and emissions from petunia flowers indicates that the role of the plant cuticle in the VOC emission network is attributed to the differential control on mass transfer of individual VOCs by controlling the composition, amount, and dynamics of scent emission.

Iminopyridine Ni(II) Catalysts Affording Oily Hyperbranched Ethylene Oligomers and/or Crystalline Polyethylenes Depending on the Reaction Conditions: Possible Role of In Situ Catalyst Structure Modifications

Nickel-based ethylene polymerization catalysts have unique features, being able to produce macromolecules with a variable content of branches, resulting in polymers ranging from semicrystalline plastics to elastomers to hyperbranched amorphous waxes and oils. In addition to Brookhart’s α-diimine catalysts, iminopyridine Ni(II) complexes are among the most investigated systems. We report that Ni(II) complexes bearing aryliminopyridine ligands with bulky substituents both at the imino moiety and in the 6-position of pyridine afford either hyperbranched low molecular weight polyethylene oils or prevailingly linear crystalline polyethylenes or both, depending on the ligand structure and the reaction conditions. The formation of multiple active species in situ is suggested by analysis of the post-polymerization catalyst residues, showing the partial reduction of the imino function. Some related arylaminopyridine Ni(II) complexes were also synthesized and tested, showing a peculiar behavior, i.e., the number of branches of the produced polyethylenes increases while ethylene pressure increases.

Wax-assisted crack-free transfer of monolayer CVD graphene: Extending from standalone to supported copper substrates

The transfer of CVD graphene grown on catalytic copper with an additional supporting substrate is different from that grown on the standalone copper foils, and the flexible polymer-based transfer supports are not quite suitable. For this purpose, we invented a wax-assisted crack-free graphene transfer method by taking advantage of the low polarity, high rigidity, and molecular-mixing nature of wax. Unlike other small-molecule transfer supports, the amorphous wax effectively mitigates the interfacial thermal stress caused by phase transition, enabling a clean and integral graphene transfer. Microscopic and spectroscopic characterizations reveal less doping defects of the wax-transferred graphene than its PMMA-transferred counterpart, demonstrating great electric properties with high electron and hole mobilities. Consequently, this new transfer method provides a universal solution for CVD graphene grown on various substrates, and paves the way for further extending their applications.

Microstructural and histochemical characteristics of Lycium barbarum L. fruits used in folk herbal medicine and as functional food

Lycium barbarum L. fruits, referred to as functional food, have long been used in traditional and folk herbal medicine due to their therapeutic properties. The fruit microstructure was analysed using light, scanning and transmission electron microscopes. The distribution of bioactive compounds in drupe tissues was assessed with histochemical and fluorescence assays. The analysis of the microstructure has shown that the fruit is covered by a skin with an amorphous cuticle and a layer of amorphous epicuticular waxes on the surface. The skin is composed of a single-layered epidermis with thickened walls and one layer of hypodermis with slightly thickened periclinal walls. The pericarp cells contain different types of chromoplasts, which most often contained exhibited reticulotubules/fibrils of carotenoid pigments and phytoferritine deposits. The results of the histochemical assays demonstrated that the secondary metabolites with high phytotherapeutic importance were located in all layers of the pericarp and seeds and, specifically, in the drupe exocarp and endocarp. The phytochemicals were represented by polysaccharides (LBP), lipid compounds (carotenoids, essential oils, sesquiterpenes, steroids), polyphenols (tannins and flavonoids), and alkaloids. This study, which is the first report of the microstructure and localisation of bioactive compounds in wolfberries, is a valuable complement of phytochemical analyses and can be helpful for enhancement of the therapeutic effect of the fruit as well as preliminary assessment of the medicinal potential in the search for new pharmaceuticals. Detailed anatomical studies are crucial for exploration of determinants of fruit quality and useful for identification of diagnostic taxonomic traits.

FIRST INSIGHTS INTO MICROMORPHOLOGY OF NEEDLE EPICUTICULAR WAXES OF SOUTH-EASTERN EUROPEAN PINUS NIGRA J. F. ARNOLD POPULATIONS

This is the fi rst insight into the fi ne structure of the epicuticular wax crystalloids found on the adaxial surfaces of needles from three Pinus nigra subspecies (ssp. nigra, ssp. banatica (Borbás) Novák, and ssp. pallasiana (Lamb.) Holmboe) growing wild in the south-eastern Europe. In general, the main wax crystalloids in P. nigra taxa were tubules, fairly dense, with reticular aspect and restricted to suprastomatal chambers. The P. nigra needles have amorphous wax - smooth layers, granules, alone tubes lying on the surface, tubes slightly fused to each other, tubes fused together, and longitudinally aggregated rodlets. The only diff erence between the studied P. nigra samples was related to the presence of longitudinally aggregated rodlets in the medial part of adaxial needle surfaces. The micromorphological characters found using SEM are compared and discussed from fundamental and applicative aspects.

Postharvest changes in LIN5-down-regulated plants suggest a role for sugar deficiency in cuticle metabolism during ripening

The cell wall invertase gene (LIN5) was reported to be a key enzyme influencing sugar uptake of tomato (Solanum lycopersicum) fruit. It was additionally revealed to be a key regulator of total soluble solids content in fruit as well as for reproductive development, being mainly involved in flower development, early fruit and seed development but also in ripening. Here, we demonstrate that silencing of the LIN5 gene promotes changes affecting fruit cuticle development which has a direct effect on postharvest properties. Transformants were characterized by reduced transpirational water loss in mature fruits accompanied by several other changes in the cuticle. Quantitative chemical composition, coupled with microscopy of isolated cuticle fruits revealed that the cuticle of the transformants were characterized by an increase of the thickness as well as significant increase in the content of cuticle components (cutin, phenolic compounds, and waxes). Furthermore, detailed analysis of the waxes revealed that the transformants displayed changes in waxes composition, showing higher levels of n-alkanes and triterpenoids which can shift the proportion of crystalline and amorphous waxes and change the water flux through the cuticle. Expression of the genes involved in cuticle biosynthesis indicated that LIN5 influences the biosynthesis of components of the cuticle, indicating that this process is coupled to sugar uploading via a mechanism which links carbon supply with the capacity for fruit expansion.

Effect of Ultrasound-Assisted Osmotic Dehydration Pretreatment on Drying Kinetics and Effective Moisture Diffusivity of Mirabelle Plum

Conventional air drying of plum is a slow and energy-intensive process because of its waxy skin having low permeability to moisture. Ultrasound application in drying foodstuffs aims at reducing the time needed to process and improve the quality characteristics of dried product. In this study, the effect of ultrasound-assisted osmotic dehydration pretreatment on drying kinetics and effective moisture diffusivity of Mirabelle plum during drying was examined. Pretreatments including ultrasonication time at two levels (10 and 30 min), osmotic solution concentration at two levels (50 and 70% sucrose) and immersion time in osmotic solution at four levels (60, 120, 180 and 240 min) were performed. Results showed that application of ultrasound-assisted osmotic dehydration pretreatment can lead to a significant increase in effective moisture diffusivity (from 5.84 × 10−9 to 7.36 × 10−9 m2/s) resulting in a 20% decrease in drying time, and thus involving a higher energy saving and preserving heat labile nutrients. Practical Applications The Mirabelle plum is appreciated by consumers for its health benefits. Drying is among the most popular methods to prolong its shelf life. The Mirabelle plum's skin consists of an underlying amorphous wax layer adjacent to the cuticle proper, together with crystalline granules of wax protruding from the surface. The waxy skin has a low permeability to moisture that increases drying time leading to possible quality deteriorations. Therefore, any pretreatment for plum drying processes that decreases drying time by reducing the initial moisture content and preserves the prune (dried plum) quality is of considerable interest. Methodologies such as ultrasound-assisted osmotic dehydration can be implemented as an alternative pretreatment to reduce drying time and, consequently, processing costs. This study provides information on the effects of operating conditions (sonication time, concentration of osmotic solution and immersion time in the osmotic solution) on drying kinetics, total processing time and effective moisture diffusivity.

Solvent Effects on the Ultrastructure and Chemical Composition of Cuticular Wax and Its Potential Bioactive Role Against Alternaria alternata in Pingguoli Pear

Effects of different polarity solvents on the ultrastructure and chemical composition of cuticular wax in Pingguoli pear as well as their bioactive role against Alternaria alternate were studied and the results showed that the highest wax content was extracted with chloroform, and its wax content was up to 322.2 μg cm−2. Long-chain fatty acids predominated in menthol extracts and n-alkanes were predominant in wax extracted with ether, chloroform and n-hexane. Pingguoli pear fruit surface was covered by a smooth and amorphous wax layer with small, scattered crystal. The morphology of recrystallized wax in vitro after removal with different solvents was not similar to that of the intact fruit surface. Removal of cuticular wax with various solvents significantly enhanced A. alternata infection, except for wax removed by methanol. The solvent extracts of methanol and chloroform stimulated the spore germination and mycelium growth of A. alternata, but the ether and n-hexane extracts showed antifungal activity.

Particulate pollutants are capable to ‘degrade’ epicuticular waxes and to decrease the drought tolerance of Scots pine (Pinus sylvestris L.)

Air pollution causes the amorphous appearance of epicuticular waxes in conifers, usually called wax ‘degradation’ or ‘erosion’, which is often correlated with tree damage symptoms, e.g., winter desiccation. Previous investigations concentrated on wax chemistry, with little success. Here, we address the hypothesis that both ‘wax degradation’ and decreasing drought tolerance of trees may result from physical factors following the deposition of salt particles onto the needles.Pine seedlings were sprayed with dry aerosols or 50 mM solutions of different salts. The needles underwent humidity changes within an environmental scanning electron microscope, causing salt expansion on the surface and into the epistomatal chambers. The development of amorphous wax appearance by deliquescent salts covering tubular wax fibrils was demonstrated. The minimum epidermal conductance of the sprayed pine seedlings increased.Aerosol deposition potentially ‘degrades’ waxes and decreases tree drought tolerance. These effects have not been adequately considered thus far in air pollution research.

Development of flexible zein–wax composite and zein–fatty acid blend films for controlled release of lysozyme

The aim of this study was controlled release of lysozyme by modification of hydrophobicity and morphology of zein films using composite and blend film making methods. The incorporation of beeswax, carnauba or candelilla wax into films at 5% (w/w) of zein gave composite films containing amorphous wax particles, while incorporation of oleic acid into film at 5% of zein caused formation of blend films containing many spherical zein capsules within their matrix. The lysozyme release rates of composites reduced as the melting point of waxes increased. The composites and blends showed 2.5 to 17 fold lower lysozyme release rates than controls. The films were effectively plasticized by using catechin. The catechin also provided antioxidant activity of films (up to 69μmol Trolox/cm2) and contributed to their controlled release properties by reducing film porosity. The films showed antimicrobial activity against Listeria innocua. This work showed the possibility of obtaining advanced edible films having flexibility, antimicrobial and antioxidant activity and controlled release properties.

The structure of the fruit peel in two varieties of Malus domestica Borkh. (Rosaceae) before and after storage

The structure of fruit peel of two apple varieties ‘Szampion’ and ‘Jonagold’ was investigated using light microscopy as well as scanning and transmission electron microscopy. The samples were taken immediately after harvest and after 6-month controlled atmosphere storage. The Szampion and Jonagold fruit differed in terms of the surface type, number of lenticels, thickness of the cuticular epithelium, height of epidermal cells and thickness of the hypodermis as well as the amount of crystalline wax and the number of microcracks formed on the fruit surface. The 6-month storage resulted in fruit weight loss, increased numbers and depth of microcracks, thickening of the amorphous wax layer and enhanced production of platelet forms of crystalline wax, which filled the microcracks abundantly. Compared with Jonagold, the Szampion fruit exhibited a fewer lenticels, a bigger number of microcracks, smaller amounts of crystalline wax and more substantial weight loss. The apple varieties studied had a reticulate–lamellate cuticle, and at harvest, the epidermal and hypodermal cells contained numerous amyloplasts filled with starch grains, which were not found after the storage period. Additionally, after storage, the cell protoplasts in the apple peel displayed a disorganised structure, and their vacuoles contained fragments of cell membranes, intravacuolar precipitates and deposits, and spherical bodies. The results may facilitate better understanding of changes occurring in fruits of Szampion and Jonagold during storage and help choose the best storage conditions to reduce loss of weight and prevent impairment of fruit quality.

Cutin plays a role in differentiation of endosperm-derived callus of kiwifruit

Cutin fluorescence, after auramine O treatment, was detected on the surface of organogenic areas (protuberances) of endosperm derived callus induced on Murashige and Skoog medium with thidiazuron (0.5mgl(-1)) in darkness. Electron micrographs of the protuberances revealed cuticle, visible as a dark-staining layer, and amorphous waxes on the cell wall. In some cases the cells of the epidermis-like layer and shoot buds at early stages of development showed thick and characteristically wavy cutin. This waviness corresponds with the wrinkled appearance of the cell wall as observed by scanning electron microscopy. The role of multivesicular bodies in cutin production and transfer to the plasma membrane is discussed.

Epicuticular wax on stomata of damaged silver fir trees (Abies alba Mili.)

Condition of epistomatal wax on the abaxial surface of the current and previous-year needles of damaged silver fir trees (<em>Abies alba</em> Mill.), both from the polluted Risnjak and "clean" Donja Dobra sites in Gorski Kotar region, both influenced by pollutants coming from Europe, during two years, three times a year, were examined with Scanning Electron Microscope. In the course of time the wax tubules on the epistomatal rims of stomata in polluted, but also in "clean" needles surface, become fused and agglomerated rapidly to various extents of morphologically different types of amorphous wax crusts, primarily compact and particulate ones. This process begins very early, especially in polluted Risnjak site, and may be interpreted as a possible result of air pollution. However, the recrystalization, or production of new tubules, also appears relatively quickly in mostly cases. Quantitative estimations indicate a very large total amount of amorphous wax crusts in the current-year needles, and a very high percentage of the same wax in previous-year needles. Amorphous wax crusts cover stomatal pores, as well as the rims, disturbing the normal gas exchange. Statistically there is a signicant tendency of increase in wax degradation in the needles of the polluted site in comparison with those of the unpolluted one, but there is an insignificant wax degradation among the needles of damaged trees within each site. These results confirmed most of the research done in our preliminary report.

Effect of 3 years' free-air exposure to elevated ozone on mature Norway spruce ( Picea abies (L.) Karst.) needle epicuticular wax physicochemical characteristics

We examined the effect of ozone (O 3) on Norway spruce ( Picea abies) needle epicuticular wax over three seasons at the Kranzberg Ozone Fumigation Experiment. Exposure to 2× ambient O 3 ranged from 64.5 to 74.2 μl O 3 l −1 h AOT40, and 117.1 to 123.2 nl O 3 l −1 4th highest daily maximum 8-h average O 3 concentration. The proportion of current-year needle surface covered by wax tubes, tube aggregates, and plates decreased ( P = 0.011) under 2× O 3. Epistomatal chambers had increased deposits of amorphous wax. Proportion of secondary alcohols varied due to year ( P = 0.004) and O 3 treatment ( P = 0.029). Secondary alcohols were reduced by 9.1% under 2× O 3. Exposure to 2× O 3 increased ( P = 0.037) proportions of fatty acids by 29%. Opposing trends in secondary alcohols and fatty acids indicate a direct action of O 3 on wax biosynthesis. These results demonstrate O 3-induced changes in biologically important needle surface characteristics of 50-year-old field-grown trees.

Progress in the study on genes encoding enzymes involved in bio-synthesis of very long chain fatty acids and cuticular wax in plants

Very long chain fatty acids (VLCFAs) play a comprehensive role in organisms. They are essential biological components in seed storage triacylglycerols (TAGs), membrane lipids, and sphingolipids. They also serve as precursors of wax layer compounds. The cuticle covers the aerial surface of land plants, which consists of cutin and wax. The wax, including amorphous intracuticular wax embedded in cutin polymer and epicuticular wax crystalloids that cover the outer plant surface, plays crucial roles in plant growth and development, and adaptation to environment. Biosynthesis of VLCFAs is catalyzed by the fatty acyl-CoA elongase, a membrane-bound enzymatic complex containing 3-ketoacyl-CoA synthase (KCS), 3-ketoacyl-CoA reductase (KCR), 3-hydroxacyl-CoA dehydratase (HCD), and trans-2, 3-enoyl-CoA reductase (ECR). Very long chain fatty acid wax precursors flux into cuticular wax biosynthetic pathways through acyl reduction and decarbonylation, and then are converted to all kinds of wax components. This article reviews the functions of VLCFAs and cuticular wax, and the recent progress in cloning and characterization of genes encoding enzymes involved in catalyzing VLCFAs and cuticular wax biosynthesis. The problems existing in researches of wax genes are also discussed.

Wax Inhibition by Comb-like Polymers: Support of the Incorporation−Perturbation Mechanism from Molecular Dynamics Simulations

Deposition of wax on a cold surface is a serious problem in oil production. Progress in developing more effective wax inhibitors has been impeded by the lack of an established mechanism connecting the molecular structure to inhibitor efficiency. Some comb-like polymers having long alkyl side chains are known to decrease the rate of wax formation. Among several possible mechanisms, we investigate here the incorporation-perturbation mechanism. According to this mechanism, the inhibitor molecules in oil are preferentially partitioned (incorporation) toward the wax-rich (amorphous) wax deposits (soft wax), which then serves as a perturbation to slow down the ordering transition of soft amorphous wax into more stable but problematic hard wax crystals. Indeed, molecular dynamics simulations on an effective inhibitor molecule in both the oil phase and in the amorphous wax phase support the idea that the oil-to-wax partition of the inhibitor is energetically favorable. With the inhibitor molecule embedded, the structure of wax crystal is disturbed, significantly decreasing the order and significantly lowering the cohesive energy density relative to that of the pure wax crystal, supporting the slower transition from soft wax to hard wax. Thus, in the presence of an effective wax inhibitor, crystallization (formation of hard wax) is slowed dramatically, so that there is time to flush out the soft wax with a high-pressure flow inside the pipeline. This suggests design principles for developing improved wax inhibitors.

Total internal reflection Raman spectroscopy of barley leaf epicuticular waxes in vivo

The use of total internal reflection (TIR)-Raman spectroscopy to examine cuticular wax layers in vivo at the surface of barley leaves ( Hordeum vulgare L. cultivar Pastoral) is demonstrated. The limited penetration depth (40 nm) of the evanescent wave compared to the thickness of the wax layer eliminates problems arising from fluorescence from underlying pigments. Epicuticular wax crystals are observed to be more crystalline than the amorphous wax layer, which is analysed after removal of the wax crystals by cellulose acetate stripping. Carotenoids are detected as trace species in the cuticular waxes.

Accelerators Increase Permeability of Cuticles for the Lipophilic Solutes Metribuzin and Iprovalicarb but Not for Hydrophilic Methyl Glucose

Effects of diethylsuberate (DESU), tributyl phosphate (TBP), and monodisperse ethoxylated alcohols (EAs) on rate constants of penetration (k) of model solutes across astomatous cuticular membranes isolated from Madagascar ivy (Stephanotis floribunda) and pear (Pyrus communis) leaves were studied. Model solutes (selected on the basis of their octanol/water partition coefficients, K(ow)) were iprovalicarb (log K(ow) = 3.18), metribuzin (log K(ow) = 1.60), and methyl glucose (MG) (log K(ow) = -3.0). K(ow) varied by more than 6 orders of magnitude. Accelerators had wax/water partition coefficients (log K(ww)) ranging from 1.75 (DESU) to 4.32 (C(12)E(2)), and their equilibrium concentrations in Stephanotis wax varied from 0 to about 160 g kg(-)(1). Accelerators increase solute mobility in cuticles by increasing fluidity of cutin and waxes. This effect was quantified by plotting log k versus the accelerator concentration in wax. With the lipophilic solutes metribuzin and iprovalicarb, these plots were linear. Slopes of these plots characterize the intrinsic activities of the accelerators, and they decreased in the order DESU (0.029) > TBP (0.015) > EAs (0.01). Using these intrinsic activities, the effects of accelerators on rate constants of penetration can be calculated for any accelerator concentration in wax. For instance, at 50 g kg(-)(1), rate constants for lipophilic solutes increased by factors of 28 (DESU), 5.6 (TBP), and 3.2 (C(12)E(n)()), respectively. Permeability of cuticles for the hydrophilic MG was not increased by DESU, TBP, C(12)E(2), and C(12)E(4), while C(12)E(6) and C(12)E(8) increased it. Small hydrophilic solutes such as MG can access aqueous pores in cuticles, and this pathway is not affected by changes in fluidity of amorphous waxes. After rate constants of penetration of ionic CaCl(2) were compared with those for nonionic MG, it was concluded that 60% of the MG diffused across aqueous pores, while 40% used an alternative pathway. Because the solubility of MG in wax is extremely low, it is unlikely that MG diffused along the lipophilic pathway used by metribuzin and iprovalicarb. This agrees with the observation that DESU and TBP had no effect on rate constants for MG. An alternative pathway of unknown properties is suggested. It is speculated that C(12)E(6) and C(12)E(8) sorbed in cuticles might have generated a polar pathway for MG.

Leaf Epicuticular Wax and Cuticle Ultrastructure of Four Eucalyptus Species and Their Hybrids

Leaf epicuticular wax and cuticle ultrastructure were assessed in four eucalypt species Eucalyptus platypus, Eucalyptus spathulata, Eucalyptus yalatensis and Eucalyptus viridis, and in their interspecific hybrid progeny. In parent species, epicuticular wax appeared as digitate‐edged platelets. Leaves of E. yalatensis showed parallel‐stacked platelets and abundant surface wax cover, while other species showed random or parallel‐oriented platelets forming a less dense cover. Distinct cuticular papillae were evident on E. yalatensis leaves but not in the other species. Leaf surfaces of E. platypus and E. spathulata were indistinguishable. Epistomatal cavities were present in all species and were lined with digitate‐edged platelets, except for those in E. viridis leaves, which contained amorphous wax. Subsurface cuticular channels connecting epistomatal cavities were detected in some species. The wax and cuticle morphology of E. \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amss...