G. W. Robertson

Effects of environment on the composition of epicuticular wax esters from kale and swede

Abstract The composition of intact leaf epicuticular wax esters of two individual genotypes each of kale and swede grown indoors (I) and outdoors (O) at SCRI, Scotland, and outdoors at Wadenswil in Switzerland (S), were determined by GC-mass spectrometry. For all genotypes (I, O, S) esters were found to consist of unbranched ( n- ) and branched anteiso - ( a- ) and iso - ( i- ) components in the a : a , a : i , i : a , a : n , n : a , n : n and i / n : n / i acid-alcohol combinations. Esterification was non-random, n : n and doubly branched br -/ br - combinations were favoured over mixed n -/ br - combinations. Combinations with extremes of acid and alcohol chain-length were generally uncommon, although longer-chain alcohols were more predominant in some swede esters. There were considerable compositional differences between indoor-grown plants (I) and those grown outdoors (O and S). In general, i : n / n : i , i : a and a : i esters were relatively more abundant in (O and S) and n : n and n : a esters were more abundant in (I), whereas a : n and a : a esters were of similar abundance in all (I, O and S). Generally, (I)-grown plants were found to have proportionally more esters of longer chain-length and (O, S)-grown plants proportionally more esters of shorter chain-length. For kale a : a , n : n , a : n and n : a esters, this was particularly related to variation in alcohol chain-length. There were also major compositional differences between kale and swede esters, long-acid-short-alcohol combinations were more prominent in the former, while short-acid-long-alcohol combinations dominated in the latter.

Changes in the chemical composition of volatiles released by the flowers and fruits of the red raspberry (Rubus idaeus) cultivar glen prosen

Volatiles at various stages of inflorescence development, bud formation, flowering, fruit formation and ripening of a red raspberry, were entrained on the porous polymer Tenax TA and analysed by thermal desorption-gas chromatography-mass spectrometry. Major classes of compound identified included aliphatic and aromatic hydrocarbons, aldehydes, ketones, alcohols and esters, monoterpenes and sesquiterpenes. As the inflorescences matured, levels of green leaf volatiles such as trans-β-ocimene and cis-3-hexenyl acetate declined and the monoterpenes, α-pinene, camphene, β-myrcene and limonene increased. During fruit ripening several additional compounds appeared including α- and β-ionone, α- and β-phellandrene and hexanoic acid ethylester. Ethyl acetate at 12–18% was the major detectable volatile product of the ripe fruit.

Ecological biochemistryEffects of environment on the composition of epicuticular wax from kale and swede

The composition of leaf epicuticular waxes of two genotypes each of kale and swede were determined by gas chromatography-mass spectrometry. Plants were grown indoors (I) and outdoors (O) at SCRI, Scotland, and outdoors at Wadenswil in Switzerland (S). Epicuticular waxes from outdoor-grown plants (O and S) were found to have higher proportions of n-alkanes, octacosanoic acid, primary alcohols and long-chain esters but lower proportions of aldehydes, ketones, ketols and secondary alcohols than waxes from (I)-grown plants. Outdoor-grown plants were also found to have proportionally more shorter chain length compounds and indoor-grown plants proportionally more compounds of longer chain length. Variations in wax composition between genotypes of a species and between species were also observed. Differences in leaf surface wax ultrastructure, between species, and between different growth conditions were detected using scanning electron microscopy. The possible role of leaf wax chemicals in the antixenotic resistance to the turnip root fly, Delia floralis, of certain genotypes was also considered.

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

Abstract 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.

Epicuticular waxes and volatiles from faba bean (Vicia faba) flowers

Abstract The floral bouquet of faba bean flowers was shown to be a complex mixture of some 27 identifiable compounds. In addition to the ubiquitous mono and sesquiterpenes, the porous-polymer entrained volatiles included a diverse range of phenylpropenoids which together accounted for over 7% of the total. Cinnamyl alcohol was also found to be the most abundant free alcohol in the epicuticular wax of faba bean flowers. Two new classes of epicuticular wax esters consisting of saturated C16, C18, C20, C22 and C24 fatty acids esterified with the phenylpropenoid, cinnamyl alcohol and with the diterpene, phytol have been identified.

A comparison of the composition of epicuticular wax from red raspberry (Rubus idaeus L.) and hawthorn (Crataegus monogyna Jacq.) flowers.

Epicuticular waxes have been characterised from the flowers of raspberry and hawthorn, on both of which adult raspberry beetles (Byturus tomentosus) can feed. The flower wax from both species had similar alkane profiles and also contained long-chain alcohols, aldehydes and fatty acids. The range of the carbon numbers detected for these classes of compounds was broadly similar in both but the relative amounts of each differed between species. Raspberry flower wax also contained fatty acid methyl esters, a group of compounds that has rarely been detected in plant epicuticular waxes, however, these were not observed in hawthorn flower wax. Long-chain alcohol-fatty acid esters with carbon numbers ranging from C36 to C48 were also detected in both plant species. However, an examination of their constituent acids indicated that in hawthorn the esters based on the C16 fatty acid predominated, whilst in raspberry flower wax, esters based on the C20 fatty acid were most abundant. Both species also contained pentacyclic triterpenoids, which accounted for, on average, over 16 and 48% of the total wax extracted from raspberry and hawthorn flowers respectively. In the former, ursolic and oleanolic acids accounted for over 90% of the pentacyclic triterpenes, whilst hawthorn flower wax, in addition to containing these acids, also contained high relative concentrations of both free and esterified alpha- and beta-amyrins.

The identification of potential aeroallergen/irritant(s) from oilseed rape (Brassica napus spp. oleifera): volatile organic compounds emitted during flowering progression

Volatile organic compounds emitted by growing intact oilseed rape plants have been detected using an entrainment apparatus enabling volatile headspace analysis by thermal desorption coupled to capillary gas chromatography‐mass spectrometry. In total, 22 volatile compounds were identified as being emitted during the flowering period. The main constituents were α‐farnesene (a sesquiterpene); β‐myrcene (a monoterpene); linalool (a monoterpene alcohol) and the ‘green leaf’ volatile (E)‐3‐hexen‐1‐ol acetate. These compounds constituted between 50 and 87% (mean 68%) of the total volatiles emitted in all of the entrainments carried out with flowering oilseed rape plants. The remaining constituents consisted of a range of compounds including other terpenoids, the characteristic ‘green leaf’ volatile (E)‐3‐hexen‐1‐ol, short chain alcohols and ketones, organic sulphides and nitrogen‐containing compounds. These were generally present as minor constituents but some plant entrainments revealed that higher relative amounts could be emitted. This was particularly apparent for dimethyl disulphide, 3‐methyl‐2‐pentanone, 3‐hydroxy‐2‐butanone, sabinene, isomyrcenol and (E)‐3‐hexen‐1‐ol. The possible role of the 22 compounds in respiratory mucosa and conjunctiva irritation associated with airborne releases from oilseed rape is discussed.

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

Abstract Epicuticular waxes from two cultivars of red raspberry ( Rubus idaeus ) were collected from the newly emerging crown leaves, and also from the group of four more mature leaves immediately below the crown. One cultivar, Autumn Bliss, was identified as aphid-resistant, and the other, Malling Jewel, as aphid-susceptible following bioassay with the large raspberry aphid, Amphorophora idaei , just prior to collection of the wax. Biological activity was primarily associated with the more mature leaves. Epicuticular wax esters consisted predominantly of long-chain aliphatic compounds in which even-carbon-number acids were esterified to even-carbon-number alcohols. Lesser amounts of odd-carbon-number esters were also present. The acid : alcohol combinations of the major esters were C 38 : 14 : 24, 16 : 22, 20 : 18; C 40 : 14 : 26, 16 : 24, 18 : 22, 20 : 20; C 42 : 16 : 26, 20 : 22; 22 : 20, C 44 : 20 : 24, 22 : 22, 24 : 20; C 46 : 20 : 26, 22 : 24, 24 : 22; C 48 : 20 : 28, 22 : 26, 24 : 24, 26 : 22; C 50 : 20 : 30, 22 : 28, 24 : 26, 26 : 24, 28 : 22 and C 52 : 22 : 30, 24 : 28, 26 : 26. Terpenyl esters were also present and these consisted of α - and β -amyrin and cycloartenol esterified to C 16 , C 18 and C 20 acids. Compositional differences between the more mature leaves which may relate to resistance to A. idaei were higher levels of cycloartenyl esters and α -amyryl esters in wax from the resistant cultivar Bliss. There were also differences between the cultivars in the distribution of individual alkyl esters and their component acids and alcohols. Esters with longer acid : shorter alcohol combinations were more abundant in Jewel than Bliss. There were compositional differences between leaves at the different developmental stages. Alkyl esters were more abundant and cycloartenyl esters were not detected in wax from the immature leaves. Small amounts of an unusual class of triacylglycerol were found only on leaves of the aphid-susceptible cultivar, Jewel, which had been subject to bioassay with raspberry aphid. These compounds, which have a C 6 acid at C-2 of the glycerol backbone, were derived from the aphid, and are the major component in the insect’s cornicle secretions. The triacylglycerols probably arise from the presence on the leaf surface of shed aphid skins, or by incorporation of cornicle fluid into the leaf wax. The abundance of aphid triacylglycerols on the leaf surface may provide a measure of aphid-susceptibility.

Floral volatiles of the sweet pea Lathyrus odoratus

Abstract The volatile components of the floral fragrances from three sweet pea cultivars have been determined using polymer entrainment and solvent elution, combined with gas-chromatography–mass spectrometry. A total of 48 compounds were detected in quantifiable amounts, 41 of which were common to all three cultivars. The most abundant compounds were consistently found to be ( E )-β-ocimene and linalool.

The fatty acid composition of the seeds ofGinkgo biloba

The fatty acid composition of seeds ofGinkgo biloba has been examined by a combination of capillary gas chromatography, silver ion high-performance liquid chromatography and gas chromatography/mass spectrometry. Some of the fatty acids identified are unusual in plants and were rather different from those reported earlier. These include ananteiso-methyl branched fatty acid, 14-methylhexadecanoic acid, 5,9-octadecadienoic acid, and 5,9,12-octadecatrienoic acid. Fourier-transform infrared spectroscopy confirmed that all of the double bonds were of thecis-configuration.