Diurnal changes in the concentrations of 2-phenylethyl β-D-glucopyranoside and the corresponding volatile aglycone in the tissue and headspace of Trifolium repens L. florets

Distinct synchronous diurnal rhythms were detected in the concentrations of phenethyl alcohol and phenethyl acetate in the tissue of blooming Trifolium repens florets. Corresponding rhythmic oscillations were observed for the same two compounds in the floral headspace. Maximum content of the volatiles in the tissue and headspace was observed 3–9 h after initiation of the photophase. The concentrations of phenethyl alcohol and phenethyl acetate in the tissue increased significantly during floral development. At full bloom the tissue contained amounts sufficient to support 2–3 h of emission. Several observations suggested that esterification of phenethyl alcohol was the source for phenethyl acetate. Trimethylsilyl derivatization and enzymatic hydrolysis of fractionated flower extracts identified 2‐phenylethyl β‐d ‐glucopyranoside as the major glucoside in the florets. The pool of glucosides increased significantly during floral development and at full bloom 97% of the phenethyl alcohol was bound as glucoside. The concentration of 2‐phenylethyl β‐d ‐glucopyranoside did not vary in a rhythmic diurnal manner. The dynamics among the diurnal rhythmic phenomena in the tissue and headspace and the fraction of volatiles bound as glucosides is discussed.     

Identification of plant semiochemicals and evaluation of their interactions with early spring insect pests of asparagus

Information is lacking on the chemical ecology of asparagus, and knowledge about the effects of its volatile emissions on its associated early season pest species is completely absent. The current study aimed to (1) evaluate whether the asparagus miner responds to asparagus volatiles, (2) identify and compare the changes in asparagus host plant volatiles from mechanical and chewing damage by the black cutworm, a temporally co-occurring species with the asparagus miner, and (3) assess how asparagus volatiles affect asparagus miner populations in the field. Results indicated that asparagus miners were significantly attracted to healthy asparagus stems when compared to clean air. Damaged asparagus headspace volatiles were quantitatively and qualitatively different from healthy plants. Volatile baits elicited a range of responses, but their effects were inconsistent between sampling years and phenology-dependent. Overall, we demonstrated that the chemical ecology of asparagus may be altered by its pest community, and volatiles identified from asparagus may impact the behavior of the asparagus miner.     

Behavioural and electrophysiological responses of Triatoma dimidiata nymphs to conspecific faecal volatiles

The behavioural and electrophysiological (electroantennography) responses of the first two instars of Triatoma dimidiata (Hemiptera: Reduviidae) Latreille to fresh and dry faecal headspace volatile extracts from fifth instar conspecific nymphs and synthetic compounds were analysed in this study. Recently emerged nymphs (3–5 days) aggregated around filter paper impregnated with dry faeces and around filter paper impregnated with extracts from both fresh and dry faeces. Older first instars (10–15 days) and second instars aggregated around filter paper impregnated with fresh and dry faeces, and their respective headspace extracts. Dry faecal volatile extracts elicited the strongest antennal responses, followed by fresh faecal extracts. Gas chromatography?mass spectrometry analysis of dried faecal headspace volatiles demonstrated the presence of 12 compounds: 2‐ethyl‐1‐hexanol, 1,2,4‐trimethylbenzene, n ‐octadecane, n ‐nonadecane, n ‐eicosane, n ‐heneicosane, n ‐tricosane, n ‐pentaeicosane, n ‐hexaeicosane, n ‐octaeicosane, nonanal, and 4‐methyl quinazoline. In fresh faecal headspace extracts, only nonanal was clearly detected, although there were other trace compounds, including several unidentified sesquiterpenes. Four of the 11 compounds tested individually elicited aggregation behaviour at concentrations of 100 ng/µL and 1 µg/µL. A blend containing these four components also mediated the aggregation of nymphs. These volatiles may be valuable for developing monitoring methods and designing sensitive strategies to detect and measure T. dimidiata infestation.     

Analysis of Headspace of Root of Levisticum officinale

The headspace of root of Levistlcum officinale was subjected to adsorb by means of XAD 4. The chemical components of the headspace obtained were analysed by GC/MS and GC/FTIR. 64 compounds have been seperated, of which 20 compounds were identified. The main compounds were monc, terpenoids and sesquiterpenoids, such as β-phellandrens (16.47%), citronellal (12.85%) and ligustilide (20.94%) etc.     

贴梗海棠挥发性成分研究(英文)

首次采用顶空固相微萃取结合气质联用技术提取并分析了贴梗海棠花蕾和花的挥发油成分。结果发现,邻苯二甲酸二(2-乙基己基)酯在花蕾开放的过程中,含量从24.67%下降到1.77%,而己二酸二(2-乙基己基)酯的含量则从0%增加到47.23%,表明在贴梗海棠花蕾开放的过程中,在植物体内多种酶的共同作用下,二者存在着生物转化,依据此结果,我们提出邻苯二甲酸二(2-乙基己基)酯与二酸二(2-乙基己基)酯在贴梗海棠开放过程中生物转化假说。     

Characterisation of volatile organic compounds in stemwood using solid-phase microextraction

Solid-phase microextraction (SPME), hydrodistillation and dynamic headspace combined with GC and GC-MS were applied and compared for the analysis of volatile organic compounds (VOCs) from coniferous wood. The SPME conditions (type of fibre, size of wood sample, temperature and exposure time) were optimised, and more than 100 VOCs and semi-volatile compounds extracted and identified from the sapwood and heartwood of Norway spruce (Picea abies). The total number of mono- and sesquiterpenes eluted and identified was similar for the SPME and hydrodistillation methods, but more semi-volatile compounds were released by hydrodistillation. By applying dynamic headspace at room temperature, it was possible to analyse only the most volatile compounds. The qualitative composition of VOCs was similar in spruce sapwood and heartwood, although Z-beta-ocimene occurred only in sapwood while fenchol was present only in heartwood. SPME sampling coupled with GC, applied here to the analysis of VOCs released from stemwood of firs for the first time, is a convenient, sensitive, fast, solvent-free and simple method for the determination of wood volatiles. The technique requires much smaller sample amounts compared with hydrodistillation, and the total amount of VOCs extracted and identified is higher than that obtained by hydrodistillation or dynamic headspace. The relative ratios of the main mono- and sesquiterpenes and -terpenoids were similar using the SPME-GC and hydrodistillation methods.     

Attraction of pepper weevil to volatiles from damaged pepper plants

Pioneer herbivorous insects may find their host plants through a combination of visual and constitutive host‐plant volatile cues, but once a site has been colonized, feeding damage changes the quantity and quality of plant volatiles released, potentially altering the behavior of conspecifics who detect them. Previous work on the pepper weevil, Anthonomus eugenii Cano (Coleoptera: Curculionidae), demonstrated that this insect can detect and orient to constitutive host plant volatiles released from pepper [Capsicum annuum L. (Solanaceae)]. Here we investigated the response of the weevil to whole plants and headspace collections of plants damaged by conspecifics. Mated weevils preferred damaged flowering as well as damaged fruiting plants over undamaged plants in a Y‐tube olfactometer. They also preferred volatiles from flowering and fruiting plants with actively feeding weevils over plants with old feeding damage. Both sexes preferred volatiles from fruiting plants with actively feeding weevils over flowering plants with actively feeding weevils. Females preferred plants with 48 h of prior feeding damage over plants subjected to weevil feeding for only 1 h, whereas males showed no preference. When attraction to male‐ and female‐inflicted feeding damage was compared in the Y‐tube, males and females showed no significant preference. Wind tunnel plant assays and four‐choice olfactometer assays using headspace volatiles confirmed the attraction of weevils to active feeding damage on fruiting plants. In a final four‐choice olfactometer assay using headspace collections, we tested the attraction of mated males and virgin and mated females to male and female feeding damage. In these headspace volatile assays, mated females again showed no preference for male feeding; however, virgin females and males preferred the headspace volatiles of plants fed on by males, which contained the male aggregation pheromone in addition to plant volatiles. The potential for using plant volatile lures to improve pepper weevil monitoring and management is discussed.     

Blow fly responses to semiochemicals produced by decaying carcasses

Volatiles from mouse carcasses in decay stages ranging from fresh to 33 days old were used to investigate oriented flight and landings in male and female blow flies of Calliphora vicina Robineau‐Desvoidy (Diptera: Calliphoridae). Oriented flight increased significantly from 36% towards fresh carcasses to 68%, 61% and 65% towards carcasses aged 3 days, 6 days and 9 days, respectively. Carcasses aged 20 days and 33 days were significantly less attractive, achieving 51% and 41% attraction, respectively. No differences emerged between the sexes in oriented flight, but a significant increase in female landings at the most attractive carcasses was observed. Headspace collections from the different stages of decay showed a succession in the volatile profile emitted from the carcasses and identified nine chemicals which peak in quantity in concurrence with the most attractive stages of decay. Three of these chemicals also showed dose–response effects as indicated by a significant correlation between the amount present and the proportion of flies responding. Blow flies are important pests and efficient traps are needed. The significant interaction between fly sex and carcass age highlights behavioural differences between male and female blow flies which can be exploited in blow fly trapping. Three new volatile chemicals, butylated hydroxyl toluene, 3‐hydroxy‐2‐butanone and nonanal, emitted from dead mice are suggested as potential attractants.     

A robust,simple, high‐throughput technique for time‐resolved plant volatile analysis in field experiments

Plant volatiles (PVs) mediate interactions between plants and arthropods, microbes and other plants, and are involved in responses to abiotic stress. PV emissions are therefore influenced by many environmental factors, including herbivore damage, microbial invasion, and cues from neighboring plants, and also light regime, temperature, humidity and nutrient availability. Thus, an understanding of the physiological and ecological functions of PVs must be based on measurements reflecting PV emissions under natural conditions. However, PVs are usually sampled in the artificial environments of laboratories or climate chambers. Sampling of PVs in natural environments is difficult, being limited by the need to transport, maintain and provide power to instruments, or use expensive sorbent devices in replicate. Ideally, PVs should be measured in natural settings with high replication, spatio‐temporal resolution and sensitivity, and modest costs. Polydimethylsiloxane (PDMS), a sorbent commonly used for PV sampling, is available as silicone tubing for as little as 0.60 € m^?1 (versus 100–550 € each for standard PDMS sorbent devices). Small pieces of silicone tubing (STs) of various lengths from millimeters to centimeters may be added to any experimental setting and used for headspace sampling, with little manipulation of the organism or headspace. STs have sufficiently fast absorption kinetics and large capacity to sample plant headspaces over a timescale of minutes to hours, and thus can produce biologically meaningful ‘snapshots’ of PV blends. When combined with thermal desorption coupled to GC–MS (a 40‐year‐old widely available technology), use of STs yields reproducible, sensitive, spatio‐temporally resolved quantitative data from headspace samples taken in natural environments.     

Toward a controllable headspace composition—Growth,development, and headspace of a micropropagatedPrunus rootstock in different containers

The body and closure device of a tissue culture container are of paramount importance in the determination of the headspace composition, and influence plant growth and development. In fact, the container determines gas exchange with the environment quantitatively and qualitatively. When exchange occurred via permeability, we demonstrated that a properly controlled container atmosphere (CA) cannot be obtained because accumulation and/or depletion of gases occur; modified atmosphere (MA) is then a better term. Our experiments also gave information about a) gas exchange mechanisms and b) the influence of headspace composition on plant growth and development. These are prerequisites for the understanding and final control of the headspace composition. Three containers, differing in their gas exchange mechanism, were evaluated. This paper also considered that even under “controlled” culture conditions (container, environment, explant weight, etc.) variations from container to container are registered, probably due to the explant itself.