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Arundo donax L. (Arundinoideae subfamily, Poaceae family) is a sub-tropical and temperate climate reed that grows in arid and semi-arid environmental conditions, from eastern China to the Mediterranean basin, suggesting potential adaptations at the epicuticular level. A thorough physical-chemical examination of the adaxial and abaxial surfaces of A. donax leaf was performed herein in an attempt to track such chemophenetic adaptations. This sort of approach is of the utmost importance for the current debate about the hypothetical invasiveness of this species in the Mediterranean basin versus its natural colonization along the Plio-Pleistocene period. We concluded that the leaf surfaces contain, apart from stomata, prickles, and long, thin trichomes, and silicon-rich tetralobate phytolits. Chemically, the dominating elements in the leaf ashes are oxygen and potassium; minor amounts of calcium, silicon, magnesium, phosphorous, sulphur, and chlorine were also detected. In both surfaces the epicuticular waxes (whose density is higher in the adaxial surface than in the abaxial surface) form randomly orientated platelets, with irregular shape and variable size, and aggregated rodlets with variable diameter around the stomata. In the case of green mature leaves, the dominating organic compounds of the epicuticular waxes of both surfaces are triterpenoids. Both surfaces feature identical hydrophobic behaviour, and exhibit the same total transmittance, total reflectance, and absorption of incident light. The above findings suggest easy growth of the plant, remarkable epidermic robustness of the leaf, and control of water loss. These chemophenetic characteristics and human influence support a neolithization process of this species along the Mediterranean basin. [ABSTRACT FROM AUTHOR]

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Cuticular wax is one of the important factors affecting the storability of fruits and vegetables. Thus, Munage grape was used as material in this study, and response surface methodology was used to optimize the process parameters of extracting cuticular wax from grapes by soaking in organic solvent. At the same time, the components and content of the cuticular wax were identified and analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that on the basis of single factor, the optimum conditions of wax extraction optimized by response surface methodology were as follows: The mixing ratio of dichloromethane and hexane was 3:1 mL/mL, the liquid-solid ratio was 2:1 mL/g, and the extraction time was 7.5 min. Under the optimal extraction conditions, the wax extraction amount was 43.60±1.04 mg/100 g, which was 0.98% difference from the predicted value of response surface. A total of 61 compounds were identified in epidermal wax, including 13 kinds of fatty acids, 13 kinds of hydrocarbon compounds, 10 kinds of alcohols, 9 kinds of esters, 5 kinds of aldehydes, 4 kinds of terpenoids, and 7 kinds of unclassified compounds. The relative content of fatty acids was the highest, accounting for 58.06% of the total wax content. This provided a theoretical reference for the further study of the relationship between the composition of cuticular wax in grapes and postharvest qualities of fruits.

The cuticle with its superimposed epicuticular waxes represents the barrier of all aboveground parts of higher plant primary tissues. Epicuticular waxes have multiple effects on the interaction of plants with their living and non-living environment, whereby their shape, dimension, arrangement, and chemical composition play significant roles. Here, the ability of self-assembly of wax after isolation from the leaves was used to develop a small-scale wax-coated artificial leaf surface with the chemical composition and wettability of wheat (Triticum aestivum) leaves. By thermal evaporation of extracted plant waxes and adjustment of the evaporated wax amounts, the wettability and chemical character of the microstructure of the surface of wheat leaves were transferred onto a technical surface. For the use of these artificial leaves as a test system for biotic (e.g., germination of fungal pathogens) and non-biotic (e.g., applied surfactants) interactions on natural leaf surfaces, the chemical composition and the wetting behavior should be the same in both. Therefore, the morphology, chemistry, and wetting properties of natural and artificial surfaces with recrystallized wax structures were analyzed by scanning electron microscopy, gas chromatography–mass spectrometry, and by the determination of water contact angles, contact angle hysteresis, and tilting angles. Wheat leaves of different ages were covered exclusively with wax platelets. The extracted wheat wax was composed of alcohols, aldehydes, esters, and acids. The main component was 1-octacosanol. The waxes recrystallized as three-dimensional structures on the artificial surfaces. The three tested wetting parameters resembled the ones of the natural surface, providing an artificial surface with the chemical information of epicuticular waxes and the wetting properties of a natural leaf surface.

This document is a corrigendum for an article titled "Leaf surfaces and neolithization - the case of Arundo donax L." published in Frontiers in Plant Science. The corrigendum addresses an error in the acknowledgments section of the original article, specifically regarding funding sources. The corrected statement provides accurate information about the funding received for the research. The authors apologize for the error and clarify that it does not affect the scientific conclusions of the article. [Extracted from the article]

Arundo donax L. (Arundinoideae subfamily, Poaceae family) is a sub-tropical and temperate climate reed that grows in arid and semi-arid environmental conditions, from eastern China to the Mediterranean basin, suggesting potential adaptations at the epicuticular level. A thorough physical-chemical examination of the adaxial and abaxial surfaces of A. donax leaf was performed herein in an attempt to track such chemophenetic adaptations. This sort of approach is of the utmost importance for the current debate about the hypothetical invasiveness of this species in the Mediterranean basin versus its natural colonization along the Plio-Pleistocene period. We concluded that the leaf surfaces contain, apart from stomata, prickles, and long, thin trichomes, and silicon-rich tetralobate phytolits. Chemically, the dominating elements in the leaf ashes are oxygen and potassium; minor amounts of calcium, silicon, magnesium, phosphorous, sulphur, and chlorine were also detected. In both surfaces the epicuticular waxes (whose density is higher in the adaxial surface than in the abaxial surface) form randomly orientated platelets, with irregular shape and variable size, and aggregated rodlets with variable diameter around the stomata. In the case of green mature leaves, the dominating organic compounds of the epicuticular waxes of both surfaces are triterpenoids. Both surfaces feature identical hydrophobic behaviour, and exhibit the same total transmittance, total reflectance, and absorption of incident light. The above findings suggest easy growth of the plant, remarkable epidermic robustness of the leaf, and control of water loss. These chemophenetic characteristics and human influence support a neolithization process of this species along the Mediterranean basin. [ABSTRACT FROM AUTHOR]

Arundo donax L. (Arundinoideae subfamily, Poaceae family) is a sub-tropical and temperate climate reed that grows in arid and semi-arid environmental conditions, from eastern China to the Mediterranean basin, suggesting potential adaptations at the epicuticular level. A thorough physical-chemical examination of the adaxial and abaxial surfaces of A. donax leaf was performed herein in an attempt to track such chemophenetic adaptations. This sort of approach is of the utmost importance for the current debate about the hypothetical invasiveness of this species in the Mediterranean basin versus its natural colonization along the Plio-Pleistocene period. We concluded that the leaf surfaces contain, apart from stomata, prickles, and long, thin trichomes, and silicon-rich tetralobate phytolits. Chemically, the dominating elements in the leaf ashes are oxygen and potassium; minor amounts of calcium, silicon, magnesium, phosphorous, sulphur, and chlorine were also detected. In both surfaces the epicuticular waxes (whose density is higher in the adaxial surface than in the abaxial surface) form randomly orientated platelets, with irregular shape and variable size, and aggregated rodlets with variable diameter around the stomata. In the case of green mature leaves, the dominating organic compounds of the epicuticular waxes of both surfaces are triterpenoids. Both surfaces feature identical hydrophobic behaviour, and exhibit the same total transmittance, total reflectance, and absorption of incident light. The above findings suggest easy growth of the plant, remarkable epidermic robustness of the leaf, and control of water loss. These chemophenetic characteristics and human influence support a neolithization process of this species along the Mediterranean basin.

Pivotal barrier properties of the hydrophobic plant cuticle covering aerial plant surfaces depend on its physicochemical composition. Among plant species and organs, compounds of this boundary layer between the plant interior and the environment vary considerably but cuticle-related studies comparing different organs from the same plant species are still scarce. Thus, this study focused on the cuticle profiles of Physalis peruviana, Physalis ixocarpa, Alkekengi officinarum, and Nicandra physalodes species. Inflated fruiting calyces enveloping fruitsmake Physalis, Alkekengi, and Nicandra highly recognizable genera among the Solanoideae subfamily. Although the inflation of fruiting calyces is well discussed in the literature still little is known about their post- floral functionalities. Cuticular composition, surface structure, and barrier function were examined and compared in fully expanded amphistomatous leaves, ripe astomatous fruits, and fully inflated hypostomatous fruiting calyces. Species- and organ-specific abundances of non-glandular and glandular trichomes revealed high structural diversity, covering not only abaxial and adaxial leaf surfaces but also fruiting calyx surfaces, whereas fruits were glabrous. Cuticular waxes, which limit non-stomatal transpiration, ranged from <1 μg cm−2 on P. peruviana fruiting calyces and N. physalodes fruits to 22 μg cm−2 on P. peruviana fruits. Very-long-chain aliphatic compounds, notably n- alkanes, iso-, and anteiso-branched alkanes, alkanols, alkanoic acids, and alkyl esters, dominated the cuticular wax coverages (≥86%). Diversity of cuticular wax patterns rose from leaves to fruiting calyces and peaked in fruits. The polymeric cutin matrix providing the structural framework for cuticular waxes was determined to range from 81 μg cm−2 for N. physalodes to 571 μg cm−2 for A. officinarum fruits. Cuticular transpiration barriers were highly efficient, with water permeabilities being ≤5 × 10−5 m s−1. Only the cuticular water permeability of N. physalodes fruits was 10 × 10−5 m s−1 leading to their early desiccation and fruits that easily split, whereas P. peruviana, P. ixocarpa, and A. officinarum bore fleshy fruits for extended periods after maturation. Regarding the functional significance, fruiting calyces establish a physicochemical shield that reduces water loss and enables fruit maturation within a protective microclimate, and promotes different seed dispersal strategies among plant species investigated. [ABSTRACT FROM AUTHOR]

The cuticle-covered surface forms the interface between plant parts, including fruits, and their environment. The physical and chemical properties of fruit surfaces profoundly influence plant-frugivore interactions by shaping the susceptibility and suitability of the host for the attacker. Grapevine (Vitis vinifera , Vitaceae) serves as one of the various host plants of the spotted wing drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae), which is invasive in several parts of the world and can cause major crop losses. The susceptibility of wine towards this pest species differs widely among varieties. The objective of our study was to identify physical and chemical traits of the berry surface that may explain the differences in susceptibility of five grape varieties to D. suzukii. Both preferences of adult D. suzukii and offspring performance on intact versus dewaxed (epicuticular wax layer mechanically removed) grape berries were investigated in dual-choice assays. Moreover, the morphology and chemical composition of cuticular waxes and cutin of the different varieties were analyzed. Bioassays revealed that the epicuticular wax layer of most tested grape varieties influenced the preference behavior of adult flies; even less susceptible varieties became more susceptible after removal of these waxes. In contrast, neither offspring performance nor berry skin firmness were affected by the epicuticular wax layer. The wax morphology and the composition of both epi- and intracuticular waxes differed pronouncedly, especially between more and less susceptible varieties, while cutin was dominated by ω-OH-9/10-epoxy-C18 acid and the amount was comparable among varieties within sampling time. Our results highlight the underestimated role of the epicuticular surface and cuticle integrity in grape susceptibility to D. suzukii. [ABSTRACT FROM AUTHOR]

Summary: The plant cuticle is the first physical barrier between land plants and their terrestrial environment. It consists of the polyester scaffold cutin embedded and sealed with organic, solvent‐extractable cuticular waxes. Cuticular wax ultrastructure and chemical composition differ with plant species, developmental stage and physiological state. Despite this complexity, cuticular wax consistently serves a critical role in restricting nonstomatal water loss. It also protects the plant against other environmental stresses, including desiccation, UV radiation, microorganisms and insects. Within the broader context of plant responses to abiotic and biotic stresses, our knowledge of the explicit roles of wax crystalline structures and chemical compounds is lacking. In this review, we summarize our current knowledge of wax biosynthesis and regulation in relation to abiotic and biotic stresses and stress responses. [ABSTRACT FROM AUTHOR]

Abstract A method to extract apple peel wax was developed using the dispersive solvent extraction technique and applied to four apple cultivars (Royal Gala, Pink Lady®, Red Delicious, and Granny Smith). Different variables of the method were optimized, namely type and volume of extraction and dispersive solvents, ionic strength, and use of ultrasound. Extracts were evaluated as gravimetric yield of wax and composition as determined by gas chromatography. Optimized conditions provided yields higher than 95%. In a repeatability assay, the relative standard deviation for the extracted wax content was <3%. Thirty-one wax compounds were identified, among them fatty acids, hydrocarbons, sterols, and terpenes. Fatty acids were the major constituents in the analyzed extracts. N-alkane, nonacosane, and triterpene ursolic acid were also significant constituents. The method allows the determination of the total peel wax content and the different constituents of this fraction from distinct apple cultivars. Graphical abstract Unlabelled Image Highlights • A novel extraction method was developed for apple peel wax characterization. • High efficiency and reduced solvent volume were found in proposed method. • The method provided a detailed cuticle profile for Malus domestica Borkh. • Peel wax composition of four different apple cultivars were characterized. [ABSTRACT FROM AUTHOR]

Sedum albumis a succulent plant, with phenotypic variability resulting in delimitation of a number of taxa with diverse taxonomic recognition. We analyzed the taxa fromSedum albumin broad sense (S. album,S. micranthum,S. athoumandS. serpentini) from Balkan Peninsula, to check whether the variability of their epidermal structures and epicuticular wax composition corresponds to their taxonomic reliability. Epidermal structures and epicuticular waxes were analyzed using light and scanning electron microscopy, gas chromatography-mass spectrometry and gas chromatography-flame ionization detector chromatography and multivariate statistical techniques. Analyses of studied taxa have shown that significant systematic characters include adaxial epidermal and guard cell length, stomatal frequency and subsidiary cells area on abaxial epidermis. The content ofn-alkanes C29, C30, C27, C32and C33was shown to be valuable criterion for their phytochemical delimitation. The comparison of epicuticular wax microstructures has shown no significant differences. Results indicate presence of two (micromorphology) or three (phytochemistry) well-defined groups of populations, withS. serpentinimanifesting a considerable level of separation toward the others.Sedum athoumhave shown weak to moderate degree of differentiation, whileS. micranthumhas shown general resemblance toS. album. [ABSTRACT FROM PUBLISHER]

Cuticular waxes act as a protective barrier against environmental stresses. In the present study, we investigated developmental and genotypic variation in wax formation of cabbage lines, with a view to understand the related morphology, genetics and biochemistry. Our studies revealed that the relative expression levels of wax biosynthetic genes in the first-formed leaf of the highest-wax line remained constantly higher but were decreased in other genotypes with leaf aging. Similarly, the expression of most of the tested genes exhibited decrease from the inner leaves to the outer leaves of 5- month-old cabbage heads in the low-wax lines in contrast to the highest-wax line. In 10-week-old plants, expression of wax biosynthetic genes followed a quadratic function and was generally increased in the early developing leaves but substantially decreased at the older leaves. The waxy compounds in all cabbage lines were predominately C29- alkane, -secondary alcohol, and -ketone. Its deposition was increased with leaf age in 5-month-old plants. The high-wax lines had dense, prominent and larger crystals on the leaf surface compared to low-wax lines under scanning electron microscopy. Principal component analysis revealed that the higher expression of LTP2 genes in the lowest-wax line and the higher expression of CER3 gene in the highest-wax line were probably associated with the comparatively lower and higher wax content in those two lines, respectively. This study furthers our understanding of the relationships between the expression of wax biosynthetic genes and the wax deposition in cabbage lines. Highlight: In cabbage, expression of wax-biosynthetic genes was generally decreased in older and senescing leaves, while wax deposition was increased with leaf aging, and C29-hydrocarbon was predominant in the wax crystals. [ABSTRACT FROM AUTHOR]

The brightness and color of lemon fruit directly determine its commodity value. Ethylene (ETH) and gibberellic acid (GA 3) treatment are widely adopted to achieve postharvest uniform peel color, which may affect fruit surface brightness. Fruit brightness is closely associated with cuticular wax. However, little is known about how ETH and GA 3 treatment affect cuticular wax metabolism in lemon fruit. Here, we treated green lemon fruit with ethephon and GA 3 solution, and analyzed the changes in wax crystal morphology, chemical composition and expression levels of wax-related genes during storage. ETH increased the density and size of platelet-like wax crystals. Moreover, ETH accelerated cuticular wax accumulation, particularly alkanes and aldehydes, while GA 3 inhibited these processes. ETH treatment increased the total wax content by 56% after four-day storage, particularly very-long-chain (VLC) alkanes (by 83%), while GA 3 decreased the total wax content by 53% after fourteen-day storage, particularly VLC alkanes (by 56%). The main differentially expressed genes, including those involved in total wax accumulation (KCS19–1 and KCS19–2) and transformation of VLC aldehydes to VLC alkanes (CER1–1 and CER3) , were up-regulated by ETH treatment while down-regulated by GA 3 treatment. In summary, ETH accelerates and GA 3 inhibits the accumulation of total wax, VLC aldehydes and VLC alkanes. I In addition, ETH and GA 3 treatment have little effect on the intrinsic quality, but can alter the membrane lipid property and oxidase activity of fruit. • Ethylene increases the density and size of platelet-like wax crystals. • Ethylene and GA 3 change the cuticular wax metabolism of lemon. • Ethylene accelerates and GA 3 inhibits cuticular wax accumulation. • Ethylene upregulated and GA 3 downregulated genes related to wax accumulation. • ETH and GA 3 treatment change lemon peel membrane lipid property and oxidase activity. [ABSTRACT FROM AUTHOR]

Navel orange ( Citrus sinensis [L.] Osbeck) fruit surfaces contain substantial quantities of cuticular waxes, which have important eco-physiological roles, such as water retention and pathogen defense. The wax constituents of ripe navel orange have been studied in various reports, while the wax changes occurring during fruit development and the molecular mechanism underlying their biosynthesis/export have not been investigated. Recently, we reported a spontaneous bud mutant from the wild-type (WT) 'Newhall' Navel orange. This mutant displayed unusual glossy fruit peels and was named 'glossy Newhall' (MT). In this study, we compared the developmental profiles of the epicuticular and intracuticular waxes on the WT and MT fruit surfaces. The formation of epicuticular wax crystals on the navel orange surface was shown to be dependent on the accumulation of high amounts of aliphatic wax components with trace amounts of terpenoids. In sharp contrast, the underlying intracuticular wax layers have relatively low concentrations of aliphatic wax components but high concentrations of cyclic wax compounds, especially terpenoids at the late fruit developmental stages. Our work also showed that many genes that are involved in wax biosynthesis and export pathways were down-regulated in MT fruit peels, leading to a decrease in aliphatic wax component amounts and the loss of epicuticular wax crystals, ultimately causing the glossy phenotype of MT fruits. [ABSTRACT FROM AUTHOR]

Sugarcane ( Saccharum officinarum L.) wax that contains policosanol (a mixture of long-chain alcohols), is widely known to have beneficial effects on human health. In order to investigate differences in the composition and content of sugarcane wax in different sugarcane cultivars, the wax, policosanol, and long-chain aldehyde composition of eight sugarcane cultivars were examined. The wax composition of sugarcane was analyzed using HPLC coupled with an evaporative light scattering detector (ELSD). Sugarcane waxes were comprised of 55-60% aldehyde and sterol esters, 32-40% alcohol, and small amounts of TAG, acid, and plant sterols. Additionally, the composition of policosanol and long-chain aldehydes was determined using GC-FID and their mass fragment compounds were identified using GC-MS. The highest content of policosanol and long-chain aldehyde compounds (500 mg and 600 mg/100 g rind, respectively), was found in the hand-peeled rind of the Ni 22 sugarcane cultivar. The content of these compounds increased up to 72% during sugarcane maturation from October to January. This study indicated that the composition and content of wax, policosanol, and long-chain aldehydes may vary depending on the cultivar of the sugarcane and the specific part of the sugarcane analyzed, as well as on the degree of sugarcane maturity. Practical applications: Different sugarcane cultivars have been evaluated in terms of their usefulness as a source of policosanol, which is a valuable wax component that may have beneficial effects on human health. Policosanol is the common name that refers to a group of long-chain (C20-C30) aliphatic primary alcohols that are of great interest since their effects include reduction of platelet aggregation, reduction of low-density lipoprotein levels in blood, inhibition of cholesterol synthesis, and prevention of atherosclerosis development, and which also display ergogenic properties. The present study detailed the wax composition, including that of policosanol and long-chain aldehydes, of sugarcanes of different cultivars. The results of this study could provide a basis for selection of sugarcane cultivars in agricultural areas for wax or policosanol production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cuticular wax morphology in glossy (GT) bilberry differs from wildtype (WT) bilberry. • Proportion of triterpenoids is higher but fatty acids and ketones lower in GT fruit. • Composition of cuticular wax changes during development similarly in WT and GT fruit. • Wax chemical composition affects epicuticular wax morphology in bilberry. • Peel-specific expression reveals genes in bilberry cuticular wax biosynthesis. In this study, cuticular wax load, its chemical composition, and biosynthesis, was studied during development of wild type (WT) bilberry fruit and its natural glossy type (GT) mutant. GT fruit cuticular wax load was comparable with WT fruits. In both, the proportion of triterpenoids decreased during fruit development concomitant with increasing proportions of total aliphatic compounds. In GT fruit, a higher proportion of triterpenoids in cuticular wax was accompanied by a lower proportion of fatty acids and ketones compared to WT fruit as well as lower density of crystalloid structures on berry surfaces. Our results suggest that the glossy phenotype could be caused by the absence of rod-like structures in GT fruit associated with reduction in proportions of ketones and fatty acids in the cuticular wax. Especially CER26-like, FAR2, CER3-like, LTP, MIXTA , and BAS genes showed fruit skin preferential expression patterns indicating their role in cuticular wax biosynthesis and secretion. [ABSTRACT FROM AUTHOR]