Epicuticular waxes of Secale cereale and Triticale hexaploide leaves

Wax on leaves of rye and of hexaploid Triticale (60–70-day-old plants) contains hydrocarbons (6–8%), esters (10%), free alcohols (14-8%), free acids (3%), hentriacontane-14,16-dione (39–45%), 25 (S)-hydroxyhentriacontane-14,16-dione (13–11%) and unidentified (14–15%). Diesters (1–3%) are also present in rye wax. Compositions of hydrocarbons (C₂₇-C₃₃) and esters (C₂₈,C₅₈) are similar for both waxes. Free and combined alcohols of rye wax are mainly hexacosanol but alcohols of Triticale wax are mainly octacosanol. The composition of Triticale wax is close to that of its wheat parent Triticum durum (cv. Stewart 63). Esters of wax from ripe rye contain 58% of trans 2,3-unsaturated esters. *NRCC No. 14033.     

Glossy mutants of maize. VIII. Accumulation of fatty aldehydes in surface waxes of gl5 maize seedlings

In corn seedlings (Zea mays L.) homozygous for the mutation gl5, the surface waxes are characteristically altered. In this mutant the main wax constituents (83.5%) are aldehydes while in the normal waxes alcohols predominate (62.7%). Moreover, in the normal waxes aldehydes and alcohols are made up mainly of the C₃₂ term (99%), whereas in gl5 waxes the principal aldehyde is still C₃₂ (90.7%) but the free alcohol composition pattern is noticeably modified. Here the predominant terms are C₂₄, C₂₆, and C₂₈, with C₃₂ representing only 16.6% of the total. The results indicate that the mutant induces a block in the synthesis of fatty alcohols while accumulating fatty aldehydes, the substrates from which the alcohols originate.     

Surface wax of Andreaea and Pogonatum species

The mosses Andreaea rupestris, Pogonatum aloides and P. urnigerum contain surface waxes in amounts of 0.05–0.12% dry wt. The waxes consisted of esters (C₃₈-C₅₄), primary alcohols (C₂₀-C₃₂), free fatty acids (C₁₆-C₃₀), and alkanes (C₂₁-C₃₁). Additionally, aldehydes (C₂₂-C₃₀) were major constituents in the wax of P. urnigerum. The classes and their chain length distributions in the surface waxes of these mosses are comparable to those of epicuticular waxes of higher plants.     

Epicuticular waxes of Sorghum and some compositional changes with plant age

Epicuticular wax from mature plants of Sorghum bicolor SD-102 was compared with that from panicles and seedlings of the same variety at the fourth-fifth leaf stage of growth. The composition of wax from SD-102 panicles was quite different from that of mature leaf blades and sheaths. Free fatty alcohols were the dominant class of wax from SD-102 seedlings and C₃₂ was the major homologue of alcohols and aldehydes. For comparison purposes, the epicuticular waxes from whole plants of two other S. bicolor varieties, Alliance A and Martin A, grown up to the tasseling stage, have been analysed. The major wax components were free fatty acids. The typical chain lengths of aldehydes, free alcohols and free fatty acids were C₂₈ and C_30.p-Hydroxybenzaldehyde was not a wax component of the studied varieties of sorghum.     

Epicuticular waxes from Agropyron dasystachyum,agropyron riparium and Agropyron elongatum

Epicuticular waxes from whole plants of Agropyron dasystachyum var. psammophylum, A. riparium and A. elongatum contain hydrocarbons (5–8 %), long chain esters (12–15%) and free acids (2–5%). The major esters are C₃₄C₅₆ esters derived from C₁₆C₃₀ acids and alcohols (1-hexacosanol is the major alcohol) but C₃₁, C₃₃ and C₃₅ esters (3–11%) are also present. The latter esters are C₁₈ and C₂₀ acid esters of C₁₃ and C₁₅ 2-alkanols. A. dasystachyum wax contains 2% free alcohols, that of A. riparium contains 17% and that of A. elongatum 11% (1-hexacosanol is the major alcohol in each). Diesters (2%), C₈C₁₂ diols esterified by (E)-2-alkenoic acids, are present in A. riparium wax. Hentriacontane-14,16-dione is present: 29% in A. dasystachyum wax and 32% in A. riparium wax, but only 5% in A. elongatum wax. 25-Oxohentriacontane-14,16-dione forms 14% of A. dasystachyum wax and 27% of A. elongatum wax but the oxo β-diketones of A. riparium wax (5%) consist of both 10-oxo- and 25-oxohentriacontane-14,16-diones in the ratio 4:1. Hydroxy β-diketones of the waxes are 25- and 26-hydroxyhentriacontane-14,16-diones; in A. dasystachyum (20%) the ratio is 3:1, in A. elongatum (20%) the ratio is 9:1 but in A. riparium (5%) it is ca 1:2. The configuration of the hydroxyl group in the 26-hydroxy β-diketone is opposite to that in the 25-hydroxy derivative. The unusual composition of the oxygenated β-diketones of A. riparium confirms that this species should be regarded as separate from A. dasystachyum. Wax from A. elongatum also contains 4-hydroxy-25-oxohentriacontane-14,16-dione (4%) and an unusual oxo-β-ketol, 18-hydroxy-7,16-hentriacontanedione (2%), both these components are probably derived biosynthetically from the 25-oxo β-diketone which is the major component of this wax. Syntheses of racemic 18-hydroxy-7,16-hentriacontanedione and of a model β-ketol, 12-hydroxy-10-pentacosanone, are described.     

Identification of In-Chain-Functionalized Compounds and Methyl-Branched Alkanes in Cuticular Waxes of Triticum aestivum cv. Bethlehem

In this work, cuticular waxes from flag leaf blades and peduncles of Triticum aestivum cv. Bethlehem were investigated in search for novel wax compounds. Seven wax compound classes were detected that had previously not been reported, and their structures were elucidated using gas chromatography-mass spectrometry of various derivatives. Six of the classes were identified as series of homologs differing by two methylene units, while the seventh was a homologous series with homologs with single methylene unit differences. In the waxes of flag leaf blades, secondary alcohols (predominantly C₂₇ and C₃₃), primary/secondary diols (predominantly C₂₈) and esters of primary/secondary diols (predominantly C₅₀, combining C₂₈ diol with C₂₂ acid) were found, all sharing similar secondary hydroxyl group positions at and around C-12 or ω-12. 7- and 8-hydroxy-2-alkanol esters (predominantly C₃₅), 7- and 8-oxo-2-alkanol esters (predominantly C₃₅), and 4-alkylbutan-4-olides (predominantly C₂₈) were found both in flag leaf and peduncle wax mixtures. Finally, a series of even- and odd-numbered alkane homologs was identified in both leaf and peduncle waxes, with an internal methyl branch preferentially on C-11 and C-13 of homologs with even total carbon number and on C-12 of odd-numbered homologs. Biosynthetic pathways are suggested for all compounds, based on common structural features and matching chain length profiles with other wheat wax compound classes.     

Epicuticular wax of Eragrostis curvula

Epicuticular wax of Eragrostis curvula contains hydrocarbons (6%), esters (13%), acids (3%), alkanols (4%), tritriacontane-12,14-dione (47%), 5(S)-5-hydroxytritriacontane-12,14-dione (14%) as major components. The esters consist of triterpenol esters (42%) as well as alkanol esters. The free alkanols consist principally Of C₁₆C₃₂ components, resembling those of waxes from panicoid, and some other eragrostoid, grasses. Minor components are triterpenols (0.7%), triterpenones (0.5%), triacylglycerols (0.3%), secondary alkanols (0.1%) and 5-oxotritriacontane-12,14-dione (0.1%).     

Composition of the epicuticular and intracuticular wax layers on Kalanchoe daigremontiana (Hamet et Perr. de la Bathie) leaves

Epicuticular and intracuticular waxes from both adaxial and abaxial surfaces of the leaves of Kalanchoe daigremontiana were analyzed. All wax mixtures were found to contain approximately equal amounts of triterpenoids and very long chain fatty acid (VLCFA) derivatives. The triterpenoid fraction consisted of glutinol (8-19% of the total wax) and friedelin (4-9%), together with smaller amounts of glutanol, glutinol acetate, epifriedelanol, germanicol and β-amyrin. The VLCFA derivatives comprised C₂₇-C₃₅ alkanes (19-37% of the total wax), C₃₂-C₃₄ aldehydes (3-7%), C₃₂ and C₃₄ fatty acids (0.2-3%), C₂₆-C₃₆ primary alcohols (4-8%), and C₄₂-C₅₂ alkyl esters (2-9%). The wax layers were found to differ in triterpenoid amounts, with the intracuticular wax containing higher percentages of most triterpenoids than the epicuticular wax. Friedelin, the only triterpenoid ketone present, showed the opposite distribution with higher proportions in the epicuticular wax. VLCFA derivatives also accumulated to higher percentages in the epicuticular than in the intracuticular wax layer. Epicuticular wax crystals were observed on both the adaxial and abaxial leaf surfaces.     

Occurrence and Carbon Metabolism of Green Nonsulfur-like Bacteria in Californian and Nevada Hot Spring Microbial mats as Revealed by Wax Ester Lipid Analysis

Green nonsulfur-like bacteria (GNSLB) in Yellowstone hot spring microbial mats have been extensively studied and are thought to operate both as photoheterotrophs and photoautotrophs. Here we studied the occurrence and carbon metabolisms of GNSLB by analyzing the distribution and isotopic composition of their characteristic wax ester lipids in four Californian and Nevada hot spring microbial mats at a range of temperatures (37–96°C). The distribution of wax esters varied strongly with temperature. At temperatures between 50–60°C the wax ester composition in each of the four hot spring microbial mats was dominated by C₃₀ to C₃₆ wax esters, consisting of mixtures of C₁₅-C₁₈ n-alkyl and branched fatty acids and alcohols, typical for GNSLB. Stable carbon isotopic analysis showed that these wax esters were only depleted by 5 to 10‰ compared to dissolved inorganic carbon in the overlying water, suggesting that these GNSLB were mainly autotrophic. However, analysis of different depth layers of one microbial mat showed that these GNSLB wax esters were increasingly depleted in ¹³C with depth, suggesting that photoautotrophy mainly occurred in the top layer of the mat. ¹³C-depleted C₃₆-C₄₄ wax esters were found in one hot spring at high temperatures (77–96°C) and are likely derived from allochtonous plant waxes. At several lower temperature sites (35–40°C) the wax esters were predominantly composed of C₂₈, C₃₀ and C₃₂ wax esters consisting of mixtures of C₁₄-C₁₆ fatty acids and n-alkanols and were depleted in ¹³C by 15–20‰ relative to dissolved inorganic carbon, suggesting they may be derived from heterotrophic organisms. Our results indicate that autotrophic GNSLB occur widely in hot springs and that diverse groups of organisms contribute to the pool of wax ester lipids in hot spring environments.     

Wax composition of sargassum fulvellum

Sixty-seven compounds were characterized in the wax of Sargassum fulvellum. Characteristic components were the 5-methylhexyl esters of octanoic, decanoic, lauric, myristic, palmitic, palmitoleic, stearic, oleic, linoleic and linolenic, and the 2-ethylhexyl esters of the same acids. The wax of S. fulvellum contains hydrocarbons (1.6%), esters (21.8%), free acids (74.9%) and free alcohols (0.3%). The principal free alcohols range in chain length only from C₆ to C₇.     

The composition of external lipids from adult whiteflies,Bemisia tabaci and Trialeurodes vaporariorum

The total surface lipids, including the wax particles, of the adult whiteflies of Bemisia tabaci and Trialeurodes vaporariorum were characterized. At eclosion, there were similar amounts of long-chain hydrocarbons, aldehydes, alcohols and wax esters. Within a few hours post-eclosion, long-chain aldehydes and long-chain alcohols were the dominant surface lipid components, C₃₄ on B. tabaci and C₃₂ on T. vaporariorum. Hydrocarbons, mainly n-alkanes, were minor components of the surface lipids. The major wax esters were C₄₆ on B. tabaci and C₄₂ on T. vaporariorum. The major acid and alcohol moieties in the wax esters of B. tabaci were C₂₀ and C₂₆, respectively, and of T. vaporariorum were C₂₀ and C₂₂, respectively. Both B. tabaci and T. vaporariorum had a minor wax ester composed of the fatty acid C_18:1 esterified to the major alcohols, C₃₄ and C₃₂, respectively. Bemisia were readily distinguished from Trialeurodes based on the composition of their wax particles and/or their wax esters; however, no differentiating surface lipid components were detected between biotypes A and B of B. tabaci.     

Leaf wax of Triticum aestivum

Leaf waxes from spring wheat varieties Selkirk and Manitou contain hydrocarbons (6%, 10%), long chain esters (14%, 13%), free acids (5%, 8%), free alcohols (19%, 21%), β-diketone (16%, 20%), hydroxy β-diketones (8%, 10%), unidentified gum (29%, 16.5%) and minor amounts of diol diesters, glycerides and aldehydes. The major hydrocarbon is nonacosane and major esters are octacosyl esters of C₁₄–C₃₂ acids but C₂₀ and C₂₂ alcohol esters of trans 2-docosenoic and tetracosenoic acids are also present (Selkirk 20%, Manitou 10% of total esters). Previously unknown trans 2-docosen-1-ol is present as an ester (Selkirk 5%, Manitou 2.5% of total esters). Free acids are C₁₄–C₃₂ acids and trans 2-docosenoic and tetracosenoic acids (Selkirk 30%, Manitou 9% of free acids). Octacosanol is the principal free alcohol. Hentriacontane-14,16-dione is the β-diketone and the hydroxy β-diketones are a 1:1 mixture of 8- and 9- hydroxyhentriacontane-14,16-diones.     

Intraspecific Variation in the Epicuticular Wax Composition of Four Species of Chionochloa

Intraspecific variation in four New Zealand species of Chionochloa, C. flavescens, C. pallens, C. rigida; and C. rubra, was investigated by examining the major carbon chain lengths of fatty acids, alcohols, aldehydes, wax esters and alkanes of the epicuticular waxes. The major even-carbon chain lengths ranged generally from C₂₄ to C₃₂ in the acids, alcohols and aldehydes; C₂₉ to C₃₃ in the alkanes; and even-carbon chains between C₃₆ and C₅₂ in the wax esters. A computer program was used to calculate the degree of similarity between samples in terms of chain length distribution. In C. rigida eastern and western South Island localities were identified; in C. flavescens Canterbury and Nelson, western South Island and southern North Island regions were recognized; and C. pallens and C. rubra were divisible into four regions; Canterbury, Nelson, western South Island and southern North Island. The possible elongation-decarboxylation pathways and the specificity of the enzymes in the biosynthetic pathways of epicuticular wax synthesis suggest the possibility that the northwest Nelson region could be a biogenetic centre from which wax synthesis has diversified along three routes, one to the western South Island, another to eastern South Island and the third to southern North Island. Identification of each of the four species based on the distribution of the carbon chain lengths in the individual lipid fractions is impossible unless the locality of collection is known. Intraspecific variation in lipid composition is not coincident with patterns of variation already reported.     

Ontogenetic variations in the composition of peach leaf wax

The composition of the epicuticular waxes from the adaxial and abaxial surfaces of peach leaves varies considerably during one season's growth. Triterpenoid acids are major components 84–95% of the waxes from the youngest leaves but the proportions of these constituents decrease as the leaves expand. The waxes from the abaxial surfaces of fully expanded leaves consist primarily of hydrocarbons (C_22–C34) and triterpenoid acids, whereas the adaxial surface waxes also contain large proportions of primary alcohols (C₂₆-C₃₄) and esters (C₄₂-C₅₂). The latter include sitosteryl esters of hexacosanoic, octacosanoic and eicosanoic acids. Variations were also noted between fully expanded leaves of different ages, the abaxial surface waxes of the oldest leaves containing the highest proportions of hydrocarbons, whilst the wax from the adaxial surface of the corresponding leaves contained the largest amounts of esters, sitosterol and hydrocarbons.     

Specific inhibition of alkane synthesis with accumulation of very long chain compounds by dithioerythritol, dithiothreitol, and mercaptoethanol in Pisum sativum

Sodium [1-¹⁴C]acetate and [1-¹⁴C]stearic acid were readily incorporated into hydrocarbons, secondary alcohols, wax esters, aldehydes, primary alcohols, and fatty acids in young pea leaves (Pisum sativum). Dithioerythritol, dithiothreitol, and mercaptoethanol (but not glutathione and cysteine) severely inhibited the incorporation of labeled acetate into alkanes and secondary alcohols with accumulation of label in wax ester and aldehyde fractions. Detailed radio gas-chromatographic analyses of the fatty acids of both the surface lipid components and internal lipids showed that dithioerythritol and mercaptoethanol specifically inhibited n-hentriacontane (C₃₁) synthesis and caused accumulation of C₃₂ aldehyde, suggesting that the inhibition was at or near the terminal step in alkane biosynthesis, presumably decarboxylation. Trichloroacetate, at a concentration that inhibited C₃₁ alkane synthesis but not the synthesis of alcohols (C₂₆ and C₂₈) specifically inhibited the formation of C₃₂ aldehyde but not that of the C₂₆ or C₂₈ aldehyde. From these results, it is concluded that the C₃₂ aldehyde is derived from the C₃₂ acyl derivative which is the precursor of C₃₁ alkane.     

Composition of leaf epicuticular waxes of Pteridium subspecies

The leaf epicuticular waxes of two subspecies of Pteridium consisted principally of alkyl esters (92 %; C₄₀–C₅₀) together with small amounts of n-alkanols (2 %; C₂₄–C₃₂) and hydrocarbons (2%; C₂₇–C₃₁). The esters comprised C₂₂–C₃₂ alkanols randomly combined with C₂₀ – C₂₄ fatty acids.     

The chemical composition of the wax of the white wax scale,Ceroplastes destructor (Newstead)

The wax of the White Wax Scale [Ceroplastes destructor (Newstead)] is shown to consist principally of a mixture of esters formed from the C₂₆ and C₂₈ alcohols and acids, together with these acids and alcohols in an uncombined state. Paraffin hydrocarbons were not detected. There is a similarity in the composition of the wax secreted by the four members of the genus Ceroplastes which have been investigated.     

Epicuticular waxes of two sorghum varieties

The epicuticular waxes of the two sorghum varieties Alliance A and SD 102 have been analyzed, after separation of the leaf blades from the sheaths. The major constituents were found to be free fatty acids but small amounts of esters, aldehydes, alcohols, n-alkanes and sterols were also detected. The typical chain lengths of aldehydes, free alcohols and free fatty acids were C₂₈ and C₃₀.     

Epicuticular wax composition in relation to aphid infestation and resistance in red raspberry (Rubus idaeus L.)

Epicuticular waxes from the aphid-resistant red raspberry (Rubus idaeus) cultivar Autumn Bliss and the aphid-susceptible cultivar Malling Jewel were collected from the newly emerging crown leaves, and also from the group of four more mature leaves immediately below the crown. Resistance and susceptibility status of the leaves to infestation by the large raspberry aphid, Amphorophora idaei, were determined by bioassay with the insect just prior to collection of the wax. Analysis showed the waxes to consist of a complex mixture of free fatty acids; free primary alcohols and their acetates; secondary alcohols; ketones; terpenoids including squalene, phytosterols, tocopherol and amyrins; alkanes and long chain alkyl and terpenyl esters. Compositional differences which may relate to A. idaei-resistance status were noticeably higher levels of sterols, particularly cycloartenol, together with the presence of branched alkanes, and an absence of C₂₉ ketones and the symmetrical C₂₉ secondary alcohol in wax from the resistant cultivar Bliss. There were also differences between the cultivars in the distribution of individual amyrins and tocopherols and in the chain length distribution for homologues of fatty acids, primary alcohols and alkanes, and these may also be related to resistance to A. idaei. Emerging leaves had lower levels of primary alcohols and terpenes, but higher levels of long-chain alkyl esters, and in general, more compounds of shorter chain-length than the more mature leaves. During bioassay A. idaei displayed a preference to settle on the more mature leaves. This may be due to greater wax coverage and higher levels of the compounds of shorter chain length found in the newly emerged younger leaves at the crown of the plant.