Search

The effect of light exposure on the steroidal glycoalkaloid content of Solanum phureja tubers has been investigated and compared with that in domesticated potato (Solanum tuberosum) tubers. The results indicated that the increase in the concentration of solanidine-based glycoalkaloids, alpha-solanine and alpha-chaconine was broadly similar in both species. However, in the S. phureja tubers, light exposure also induced the synthesis of tomatidenol-based glycoalkaloids. These have been identified as alpha- and beta-solamarine. These glycoalkaloids were not detected in tubers continually stored in darkness.

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 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.

Polymer entrainment combined with solvent elution or thermal desorption, steam distillation and solvent surface extractions has been applied to leaves from midge-resistant and -susceptible blackcurrant cultivars. Irrespective of the methods used, the predominant compounds detected were terpene hydrocarbons, but only minor quantitative differences were found in the relative concentrations of the individual mono- and sesqui-terpenes identified. Both steam distillation and thermal desorption resulted in the formation of a number of artefacts, whilst the use of polymer entrainment revealed the presence of a number of compounds, including a homoterpene not detected by either steam distillation or leaf surface solvent extraction. The relative merits of the various methods used are discussed in relation to their potential value for the identification and quantification of leaf surface volatiles. Copyright © 1999 John Wiley & Sons, Ltd.

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.

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. © 1997 Elsevier Science Ltd. All rights reserved

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.

A method for the separation and identification of complex mixtures of more than 50 different intact esters in epicuticular wax of swede, Brassica napus var. rapifera cv. Doon Major, using combined gas chromatography-mass spectrometry (GC-MS) has been developed. The esters were separated at temperatures of up to 350°C by automatic pressure programming (for capillary GC) or by manually increasing helium carrier gas pressure (for GC-MS) in order to maintain flow at high temperatures. Esters in the range C41-C50 were detected, with regular repeating acid/alcohol combinations. Individual acid and alcohol moieties were identified from [RCO2H2]+ ions in the mass spectra of intact esters and, following trans-esterification and silylation, from the mass spectral and chromatographic characteristics of the methyl esters of the acid components (C14-C23) and trimethylsilyl derivatives of the alcohol components (C23-C31). The major compounds were doubly branched C44 and C46 esters, composed of anteiso-C17/anteiso-C27 (32.7%), anteiso-C17/anteiso-C29 (11.9%) and anteiso-C19/anteiso-C27 (13.1%) acid/alcohol combinations, respectively, singly branched C43 and C45 esters, composed of n-C16/anteiso-C27 (8.5%), anteiso-C17/n-C26 (3.9%), n-C18/anteiso-C27 (6.8%), anteiso-C17/n-C28 (2.3%) and anteiso-C19/n-C26 (1.6%), were minor components.

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.

Thermal desorption coupled to capillary gas chromatography-mass spectrometry has been used to identify volatile chemicals released from the flowers of five varieties of oilseed rape. An entrainment apparatus for volatile headspace analysis is described. The major classes of compound found were organic sulphides, C4 substituted compounds, aldehydes and terpenes. The possible role of these compounds in the human allergic-type response associated with oilseed rape is discussed.

Flower volatiles from four raspberry cultivars and wild hawthorn were entrained on the porous polymers Haysep Q and Tenax TA. These were analysed by thermal desorption-gas chromatography-mass spectrometry. The major classes of compound identified included aliphatic and aromatic aldehydes, ketones, alcohols and esters, monoterpenes, sesquiterpenes, and a number of unusual nitrogen compounds. The volatile profiles of the flowers of the four raspberry cultivars exhibited only minor differences. Volatiles from the flowers of hawthorn, although similar in many respects, contained proportionately lower levels of terpenoids, but elevated levels of benzaldehyde, 3-pyridine carboxaldehyde, 4-methoxybenzaldehyde and 4-methoxybenzoic acid methyl ester.

A rapid capillary gas chromatographic method has been developed for screening coriander fruits for petroselinic acid content. The method also permits determination of the concentrations of the other major long-chain fatty acids present in coriander oil and allows an estimate of the total oil content of the sample to be determined. The method is applicable at the single fruit level and the results of analysing the constituent husk and embryo fractions have shown significant differences between their fatty acid compositions.

The phenylpropenoic acids, cinnamic, p -coumaric, ferulic, sinapic and caffeic, were photodimerized either singly or in pairs and were subjected to gas chromatographic and mass spectrometric analyses of their trimethylsilyl derivatives. Sinapic acid and five combinations of pairs gave only a single peak when analysed on two gas chromatographic columns, while all the rest gave two peaks. Mass spectrometdc analysis showed that, for most combinations, a dimer in the head-to-tail configuration was the major product but significant amounts of some dimers in the head-to-head configuration were produced. For most dimers, the molecular ion was evident in the spectrum while the configuration of the cyclobutane ring was established by the fragments formed from symmetrical and asymmetrical splitting.

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 α- and β-amyrins.

Potential evapotranspirometers and various evaporation pans are commonly used to estimate potential evapotranspiration. These instruments are expensive, large, difficult to install and use. A black Bellani plate atmometer is suggested as a simple instrument to replace these large tanks. It consists of a black, porous, ceramic plate, mounted on a glazed ceramic cup. The plate surface is kept moist by the water held in the cup. Evaporation from this surface is a measure of the drying ability of the air and is called "latent evaporation". Comparisons of various evaporimeters have shown the Bellani atmometer to be accurate and responsive to meteorological variables.Latent evaporation was compared with open-pan evaporation (from a 4-foot diameter buried tank) at several sites across Canada. Latent evaporation was also compared with evapotranspiration from irrigated field plots and evapotranspirometer tanks. The conversion factor of 0.0034 inches of evapotranspiration from irrigated fields, and 0.0032 inches of open-pan evaporation for each cubic centimetre of latent evaporation has been tentatively established. Latent evaporation and moisture block methods have shown excellent agreement in scheduling irrigation.

not available

not available