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Bactrocera bryoniae is a polyphagous and economically significant fruit fly found in Indonesia, Papua New Guinea and Australia. To understand chemical-mediated sexual communication, and the potential for novel pheromone-based attractants for monitoring and mass-trapping of B. bryoniae, rectal gland exudates and emissions from sexually mature males and females were investigated. Gas chromatography–mass spectrometry showed that male rectal glands contained six compounds, of which 1,7-dioxaspiro[5,5]undecane elicited electroantennographic (EAD) and electropalpographic (EPD) responses in both sexes, ethyl 3-acetoxybutanoate elicited EPD responses in both sexes, N-(3-methylbutyl)acetamide elicited EAD response from males and 4-hydroxy-1,7-dioxaspiro[5.5]undecane elicited EAD responses in males and females and EPD responses in females. Female rectal glands contained 23 compounds with the esters ethyl laurate and ethyl myristate as major components. Amongst the female rectal gland constituents, ethyl laurate, ethyl myristate and ethyl palmitate elicited EAD responses in males and females, N-(3-methylbutyl)acetamide elicited EAD responses in males only, (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane elicited EAD responses in males and EPD responses in females, and 2,7-dimethyl-1,6-dioxaspiro[4.5]decane, (E,E)-2-ethyl-7-methyl-1,6-dioxaspiro[4.5]decane, (E,E)-2-ethyl-8-methyl-1,7-dioxaspiro[5.5]undecane, (Z,Z)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, (E,E)-2-propyl-8-methyl-1,7-dioxaspiro[5.5]undecane and ethyl caprate elicited EPD responses in females only. Y-tube bioassays indicated that male rectal gland extracts and headspace volatiles attracted females and males, while female rectal gland extracts and headspace volatiles only attracted males. The results suggest that ethyl 3-acetoxybutanoate, 1,7-dioxaspiro[5,5]undecane and 4-hydroxy-1,7-dioxaspiro[5.5]undecane may be components of male-produced sex pheromone in B. bryoniae while (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, N-(3-methylbutyl)acetamide, ethyl laurate, ethyl myristate and ethyl palmitate may be components of female-produced sex pheromone. Ethyl 3-acetoxybutanoate, N-(3-methylbutyl) acetamide, 1,7-dioxaspiro[5,5]undecane and 4-hydroxy-1,7-dioxaspiro[5.5]undecane may be components of male aggregation pheromone. These findings contribute to the understanding of pheromone communication in B. bryoniae and provide a foundation for developing pheromone-based monitoring and control methods.

Diverse methods have been used to sample insect semiochemicals. Sampling methods can differ in efficiency and affinity and this can introduce significant biases when interpreting biological patterns. We compare common methods used to sample tephritid fruit fly rectal gland volatiles (‘pheromones’), focusing on Queensland fruit fly, Bactrocera tryoni. Solvents of different polarity, n-hexane, dichloromethane and ethanol, were compared using intact and crushed glands. Polydimethylsiloxane, polydimethylsiloxane/divinylbenzene and polyacrylate were compared as adsorbents for solid phase microextraction. Tenax-GR and Porapak Q were compared as adsorbents for dynamic headspace sampling. Along with compounds previously reported for B. tryoni, we detected five previously unreported compounds in males, and three in females. Dichloromethane extracted more amides while there was no significant difference between the three solvents in extraction of spiroacetals except for (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane for which n-hexane extracted higher amount than both dichloromethane and ethanol. Ethanol failed to contain many of the more volatile compounds. Crushed rectal gland samples provided higher concentrations of extracted compounds than intact rectal gland samples, but no compounds were missed in intact samples. Of solid phase microextraction fibers, polyacrylate had low affinity for spiroacetals, ethyl isobutyrate and ethyl-2-methylbutanoate. Polydimethylsiloxane was more efficient for spiroacetals while type of fiber did not affect the amounts of amides and esters. In dynamic headspace sampling, Porapak was more efficient for ethyl isobutyrate and spiroacetals, while Tenax was more efficient for other esters and amides, and sampling time was a critical factor. Biases that can be introduced by sampling methods are important considerations when collecting and interpreting insect semiochemical profiles.

We report on the vapor pressures at ambient temperatures of seven attractants of Bactrocera, Dacus, and Zeugodacus fruit flies—raspberry ketone, cuelure, raspberry ketone trifluoroacetate, methyl e...

Pheromones are biologically important in fruit fly mating systems, and also have potential applications as attractants or mating disrupters for pest management. Bactrocera kraussi (Hardy) (Diptera: Tephritidae) is a polyphagous pest fruit fly for which the chemical profile of rectal glands is available for males but not for females. There have been no studies of the volatile emissions of either sex or of electrophysiological responses to these compounds. The present study (i) establishes the chemical profiles of rectal gland contents and volatiles emitted by both sexes of B. kraussi by gas chromatography–mass spectrometry (GC–MS) and (ii) evaluates the detection of the identified compounds by gas chromatography–electroantennogram detection (GC–EAD) and –electropalpogram detection (GC–EPD). Sixteen compounds are identified in the rectal glands of male B. kraussi and 29 compounds are identified in the rectal glands of females. Of these compounds, 5 were detected in the headspace of males and 13 were detected in the headspace of females. GC–EPD assays recorded strong signals in both sexes against (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, 2-ethyl-7-mehtyl-1,6-dioxaspiro[4.5]decane isomer 2, (E,Z)/(Z,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, and (Z,Z)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane. Male antennae responded to (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, 2-methyl-6-pentyl-3,4-dihydro-2H-pyran, 6-hexyl-2-methyl-3,4-dihydro-2H-pyran, 6-oxononan-1-ol, ethyl dodecanoate, ethyl tetradecanoate and ethyl (Z)-hexadec-9-enoate, whereas female antennae responded to (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane and 2-methyl-6-pentyl-3,4-dihydro-2H-pyran only. These compounds are candidates as pheromones mediating sexual interactions in B. kraussi.

Passiflora maliformis is an introduced plant in Australia but its flowers are known to attract the native Jarvis&rsquo, s fruit fly, Bactrocera jarvisi (Tryon). The present study identifies and quantifies likely attractant(s) of male B. jarvisi in P. maliformis flowers. The chemical compositions of the inner and outer coronal filaments, anther, stigma, ovary, sepal, and petal of P. maliformis were separately extracted with ethanol and analyzed using gas chromatography-mass spectrometry (GC-MS). Polyisoprenoid lipid precursors, fatty acids and their derivatives, and phenylpropanoids were detected in P. maliformis flowers. Phenylpropanoids included raspberry ketone, cuelure, zingerone, and zingerol, although compositions varied markedly amongst the flower parts. P. maliformis flowers were open for less than one day, and the amounts of some of the compounds decreased throughout the day. The attraction of male B. jarvisi to P. maliformis flowers is most readily explained by the presence of zingerone in these flowers.

Bactrocera frauenfeldi (Schiner) (Diptera: Tephritidae) is a polyphagous fruit fly pest species that is endemic to Papua New Guinea and has become established in several Pacific Islands and Australia. Despite its economic importance for many crops and the key role of chemical-mediated sexual communication in the reproductive biology of tephritid fruit flies, as well as the potential application of pheromones as attractants, there have been no studies investigating the identity or activity of rectal gland secretions or emission profiles of this species. The present study (1) identifies the chemical profile of volatile compounds produced in rectal glands and released by B. frauenfeldi, (2) investigates which of the volatile compounds elicit an electroantennographic or electropalpographic response, and (3) investigates the potential function of glandular emissions as mate-attracting sex pheromones. Rectal gland extracts and headspace collections from sexually mature males and females of B. frauenfeldi were analysed by gas chromatography-mass spectrometry. Male rectal glands contained (E,E)-2-ethyl-8-methyl-1,7-dioxaspiro [5.5]undecane as a major component and (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane as a moderate component. Minor components included palmitoleic acid, palmitic acid, and ethyl oleate. In contrast, female rectal glands contained (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane and ethyl laurate as major components, ethyl myristate and ethyl palmitoleate as moderate components, and 18 minor compounds including amides, esters, and spiroacetals. Although fewer compounds were detected from the headspace collections of both males and females than from the gland extractions, most of the abundant chemicals in the rectal gland extracts were also detected in the headspace collections. Gas chromatography coupled electroantennographic detection found responses to (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane from the antennae of both male and female B. frauenfeldi. Responses to (E,E)-2-ethyl-8-methyl-1,7-dioxaspiro[5.5]undecane were elicited from the antennae of females but not males. The two spiroacetals also elicited electropalpographic responses from both male and female B. frauenfeldi. Ethyl caprate and methyl laurate, found in female rectal glands, elicited responses in female antennae and palps, respectively. Y-maze bioassays showed that females were attracted to the volatiles from male rectal glands but males were not. Neither males nor females were attracted to the volatiles from female rectal glands. Our findings suggest (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane and (E,E)-2-ethyl-8-methyl-1,7-dioxaspiro[5.5]undecane as components of a sex-attracting pheromone in B. frauenfeldi.

Tephritid fruit flies are amongst the most significant horticultural pests globally and male chemical lures are important for monitoring and control. Zingerone has emerged as a unique male fruit fly lure that can attract dacine fruit flies that are weakly or non-responsive to methyl eugenol and cuelure. However, the key features of zingerone that mediate this attraction are unknown. As Jarvis’s fruit fly, Bactrocera jarvisi (Tryon), is strongly attracted to zingerone, we evaluated the response of B. jarvisi to 37 zingerone analogues in a series of field trials to elucidate the functional groups involved in attraction. The most attractive analogues were alkoxy derivatives, with isopropoxy being the most attractive, followed by ethoxy and trifluoromethoxy analogues. All of the phenolic esters tested were also attractive with the response typically decreasing with increasing size of the ester. Results indicate that the carbonyl group, methoxy group, and phenol of zingerone are key sites for the attraction of B. jarvisi and identify some constraints on the range of structural modifications that can be made to zingerone without compromising attraction. These findings are important for future work in developing and optimising novel male chemical lures for fruit flies.

Plants undergoing heat and low-CO2 stresses emit large amounts of volatile isoprenoids compared with those in stress-free conditions. One hypothesis posits that the balance between reducing power availability and its use in carbon assimilation determines constitutive isoprenoid emission rates in plants and potentially even their maximum emission capacity under brief periods of stress. To test this, we used abiotic stresses to manipulate the availability of reducing power. Specifically, we examined the effects of mild to severe drought on photosynthetic electron transport rate (ETR) and net carbon assimilation rate (NAR) and the relationship between estimated energy pools and constitutive volatile isoprenoid emission rates in two species of eucalypts: Eucalyptus occidentalis (drought tolerant) and Eucalyptus camaldulensis (drought sensitive). Isoprenoid emission rates were insensitive to mild drought, and the rates increased when the decline in NAR reached a certain species-specific threshold. ETR was sustained under drought and the ETR-NAR ratio increased, driving constitutive isoprenoid emission until severe drought caused carbon limitation of the methylerythritol phosphate pathway. The estimated residual reducing power unused for carbon assimilation, based on the energetic status model, significantly correlated with constitutive isoprenoid emission rates across gradients of drought (r 2 > 0.8) and photorespiratory stress (r 2 > 0.9). Carbon availability could critically limit emission rates under severe drought and photorespiratory stresses. Under most instances of moderate abiotic stress levels, increased isoprenoid emission rates compete with photorespiration for the residual reducing power not invested in carbon assimilation. A similar mechanism also explains the individual positive effects of low-CO2, heat, and drought stresses on isoprenoid emission.

Light-dependent de novo volatile isoprene emission by terrestrial plants (approximately 2% of carbon fixed during photosynthesis) contributes as much as 0.5 PgC/year to the global carbon cycle. Although most plant taxa exhibit either constitutive or inducible monoterpene emissions, the evolution of isoprene emission capacity in multiple lineages has remained unexplained. Based on the predominant occurrence of isoprene emission capacity in long-lived, fast-growing woody plants; the relationship between 'metabolic scope' of tree genera and their species richness; and the proposed role of high growth rates and long generation times in accelerating molecular evolution, we hypothesise that long-lived plant genera with inherently high speciation rates have repeatedly acquired and lost the capacity to emit isoprene in their evolutionary history.

The chemical composition of a gas phase and secondary organic aerosol (SOA) mixture from toluene photooxidation in NOx was determined. Aerosol from toluene photooxidation was generated in a smog chamber and was collected onto glass fibre filters along with those gas phase compounds which adhered to the filter. The filter bound organic material was extracted, derivatised with O-2,3,4,5,6-pentafluorobenzyl hydroxylamine (PFBHA) and N,O-bistrimethylsilyl-trifluoroacetamide (BSTFA), then analysed using gas chromatography-mass spectrometry (GC–MS). Compound identification was aided by the use of isotopically-labelled toluene. The effect of humidity on product formation was investigated by raising water vapour concentration in one experiment. Sixty compounds were identified, of which twenty had not been identified from toluene photooxidation previously. Small carboxylic acids and dicarbonyls provided the highest proportion of identifiable compounds by relative response. The use of water to extract the filter samples resulted in much higher relative responses for oxocarboxylic acids, such as glyoxylic acid and pyruvic acid, than has been observed in previous studies. The formation of levulinic acid was determined to be due to the reaction of water with aromatic photooxidation products in the gas phase or particle phase of the chamber experiment. Nuclear magnetic resonance (NMR) was used to determine the functional groups of water-extracted organic material, which indicated that the water-soluble components were comprised of compounds which contain similar functional groups, primarily alcohols and carboxylic acids.

The banana fruit fly, Bactrocera musae (Tryon) (Diptera: Tephritidae), is an economically important pest endemic to Australia and mainland Papua New Guinea. The chemistry of its rectal glands, and the volatiles emitted during periods of sexual activity, has not been previously reported. Using gas chromatography&ndash, mass spectrometry (GC-MS), we find that male rectal glands contain ethyl butanoate, N-(3-methylbutyl) acetamide, ethyl laurate and ethyl myristate, with ethyl butanoate as the major compound in both rectal gland and headspace volatile emissions. Female rectal glands contain four major compounds, ethyl laurate, ethyl myristate, ethyl palmitate and (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, as well as 11 minor compounds. For both male and female B. musae, all compounds found in the headspace were also present in the rectal gland extracts, suggesting that the rectal gland is the main source of the headspace volatiles. Gas chromatography&ndash, electroantennography (GC-EAD) of rectal gland extracts confirms that male antennae respond to male-produced ethyl laurate and female-produced (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, while female antennae respond to male-produced ethyl butanoate but no female-produced compounds. This is an important step in understanding the volatiles involved in the chemical communication of B. musae, their functional significance, and potential application.

The Queensland fruit fly, Bactrocera tryoni (Froggatt) (Q-fly), is a major horticultural pest in Eastern Australia. Effective monitoring, male annihilation technique (MAT) and mass trapping (MT) are all important for control and require strong lures to attract flies to traps or toxicants. Lure strength is thought to be related in part to volatility, but little vapour pressure data are available for most Q-fly lures. Raspberry ketone (4-(4-hydroxyphenyl)-2-butanone) and analogs that had esters (acetyl, difluoroacetyl, trifluoroacetyl, formyl, propionyl) and ethers (methyl ether, trimethylsilyl ether) in replacement of the phenolic group, and in one case also had modification of the 2-butanone side chain, were measured for their vapour pressures by differential scanning calorimetry (DSC), and their attractiveness to Q-fly was assessed in small cage environmentally controlled laboratory bioassays. Maximum response of one category of compounds, containing both 2-butanone side chain and ester group was found to be higher than that of the other group of compounds, of which either of 2-butanone or ester functionality was modified. However, linear relationship between vapour pressure and maximum response was not significant. The results of this study indicate that, while volatility may be a factor in lure effectiveness, molecular structure is the dominating factor for the series of molecules investigated.

The photooxidation of fuel vapour was investigated in a smog chamber and simulated using three chemical mechanisms, the Master Chemical Mechanism (MCMv3.1), SAPRC-99 and the Carbon Bond chemical mechanism (CB05). Three varieties of fuel were used, unleaded petrol (ULP) and two ULP-ethanol blends which contained 5% and 10% ethanol (E5, E10). The fuel vapours were introduced into the chamber using two methods, by injecting the vapours from wholly evaporated fuel directly, and by injecting the headspace vapour from fuel equilibrated at 38 °C. The chamber experiments were simulated using the selected mechanisms and comparisons made with collected experimental data. The SAPRC-99 mechanism reproduced Δ(O 3 –NO) more accurately for almost all fuel types and injection modes, with negligible model error for both injection modes. The average model error for MCM simulations was −16% and for CB05 the average model error was −34%. The predictions for the CB05 mechanism varied depending on injection mode, the Δ(O 3 –NO) model error for wholly evaporated experiments was −44%, compared to −24% for headspace vapour experiments. The difference in aromatic content between experiments of different injection modes was likely to be the cause of the difference in model error for CB05. The model error for all headspace experiments was dependent upon the initial carbon monoxide concentrations. The results for Δ(O 3 –NO) were matched by the prediction of other key products, with formaldehyde predicted to within 20% by both SAPRC and the MCM. The addition of ethanol to the base SAPRC mechanism altered the predictions of Δ(O 3 –NO) by less than 2%. Changes observed in the concentrations of formaldehyde and acetaldehyde were consistent with the expected yields from ethanol oxidation.

The updated SAPRC-07 mechanism was evaluated against data from experiments performed in the CSIRO smog chamber. The mechanism predictions have been compared to experimental results as well as predictions by SAPRC-99. Experiments were performed using either toluene or m -xylene in the presence of NO x at sub-0.1 ppmv concentrations. For the majority of m -xylene experiments, the modelled Δ(O 3 –NO) concentration was within 20% of observed values for both SAPRC mechanisms. However during the oxidation of toluene the production of radicals was poorly predicted, with final Δ(O 3 –NO) concentration under-predicted by up to 60%. The predictions of major oxidants from isoprene oxidation were in good agreement with observed values. For the NO x -limited conditions however, the ozone concentration predicted by both mechanisms were under-predicted by approximately 20% in the five experiments tested. The performance of the SAPRC-07 mechanism was also evaluated against twelve evaporated fuel experiments. Two types of evaporative mode experiments were performed: headspace evaporated fuel and wholly evaporated fuel. The major difference was a significantly higher concentration of aromatic hydrocarbons and larger alkane products in wholly evaporated fuels. For headspace evaporated fuel experiments both SAPRC mechanisms were in good agreement with experimental results. For wholly evaporated experiments the average Δ(O 3 –NO) model error was −25% with SAPRC-07 compared to less than −5% for SAPRC-99. Updates to the photolysis data for dicarbonyls, the light source used and the experimental conditions under which these experiments were performed are possible causes for the discrepancy between SAPRC-99 and -07 predictions for wholly evaporated experiments.

Environmental contextChemical mechanisms are an important component of predictive air quality models that are developed using smog chambers. In smog chamber experiments, UV lamps are often used to simulate sunlight, and the choice of lamp can influence the obtained data, leading to differences in model predictions. We investigate the effect of various UV lamps on the prediction accuracy of a key mechanism in atmospheric chemistry. AbstractA new smog chamber was constructed at CSIRO following the decommissioning of the previous facility. The new chamber has updated instrumentation, is 35 % larger, and has been designed for chemical mechanism and aerosol formation studies. To validate its performance, characterisation experiments were conducted to determine wall loss and radical formation under irradiation by UV lamps. Two different types of blacklights commonly used in indoor chambers are used as light sources, and the results using these different lamps are investigated. Gas-phase results were compared against predictions from the latest version of the SAPRC chemical mechanism. The SAPRC mechanism gave accurate results for hydrocarbon reaction and oxidation formation for propene and o-xylene experiments, regardless of the light source used, with variations in ozone concentrations between experiment and modelled results typically less than 10 % over 6-h irradiation. The SAPRC predictions for p-xylene photooxidation showed overprediction in the rate of oxidation, although no major variations were determined in mechanism results for different blacklight sources. Additionally, no significant differences in the yields of aerosol arising from new particle formation were discernible regardless of the light source used under these conditions.

A rapid and sensitive fluorescence-based bioassay for determination of indoleamine 2,3-dioxygenase (IDO) activity has been developed. This assay relies on the quantification of the amount of kynurenine produced in the assay medium by fluorescence and complements the standard absorbance and high-performance liquid chromatography (HPLC) assay methods. The fluorescence method has limits of detection similar to those of the standard assay methods. Measured activities of IDO, including in the presence of tryptophan-based inhibitors, were in statistical agreement with the absorbance and HPLC assay methods. The fluorescence-based assay was also suitable for assessment of IDO inhibition by compounds that are incompatible with the absorbance method.

Environmental contextQueensland fruit fly is a major pest of fruits and vegetables in eastern Australia, sometimes causing complete loss of unprotected crops. Odours that attract fruit flies can help control these pests and this study investigated how six fruit fly species smell these chemicals. The strength of fly responses to tested odours gives insight into the way flies smell and provides information for making better attractants, potentially reducing insecticide use. AbstractThe Queensland fruit fly (Bactrocera tryoni, Q-fly) is a major horticultural pest in eastern Australia. The deployment of male lures comprises an important component of several detection and control strategies for this pest. A novel fluorinated analogue of raspberry ketone (RK), raspberry ketone trifluoroacetate (RKTA), has been developed with the aim of further improving Q-fly control. RKTA elicited strong electroantennogram (EAG) responses from Q-flies whereas cuelure (CL) and melolure (ML) responses were not significantly greater than a negative control. Further experimentation showed that RKTA also elicited EAG response from five other fruit fly species, included flies known to be strongly attracted to CL (B. neohumeralis, B. kraussi and B. frauenfeldi), weakly attracted to CL (B. jarvisi), or non-responsive to CL (Zeugodacus cucumis), whereas seven other compounds, RK, CL, ML, raspberry ketone difluoroacetate, raspberry ketone monofluoroacetate, anisyl acetone and trimethylsilyl raspberry ketone, elicited only weak responses comparable with a negative control. However, fly EAG responses to RKTA are likely due at least in part to trifluoroethanoic acid, which is a hydrolysis product of RKTA and elicited strong EAG responses from all six species when tested alone. Furthermore, whereas ethanoic acid, methanoic acid and trifluoroethanoic acid all elicited strong EAG responses in Q-flies, the only corresponding RK ester to elicit an EAG response was RKTA, suggesting that RKTA hydrolyses quickly, whereas CL and ML do not. This is in contrast to the idea that CL readily hydrolyses on contact with atmospheric moisture, an assertion that has been made in the literature repeatedly.

Estimates made by the Intergovernmental Panel on Climate Change (IPCC) and the Australian National Greenhouse Gas Inventory Committee (NGGIC) suggest that grazed pastures are substantial anthropogenic sources of nitrous oxide (N2O), contributing 28% of all anthropogenic N2O emissions globally and >43% for Australia. These estimates are based almost wholly on extrapolations of enclosure experiments to the field scale and uncertainty levels are high. Verification with direct field measurements is needed. This paper reports micrometeorological studies of N2O emissions from Australian grazed pastures made at the same location on a variety of space scales. They included a mass-balance study employing a small test plot approximately 0.05 ha in area in which 14 sheep were grazed, tower-based flux measurements representing areas between 25 ha and 5 km2 and convective boundary-layer budgets representing regions of order 100 km2. The mass-balance study, which was considered to be the most reliable micrometeorological approach, gave an average emission over 8 days of 1.87 g N2O–N head−1 d−1 corresponding to 11.5% of the nitrogen (N) voided by the animals in urine and dung. However, the data set included two days after rain on which emissions were an order of magnitude larger than on the other days in the study. For the latter, the emission of N2O accounted for 3.9% of the N excreted. Although uncertainty levels remain high due to large temporal and spatial variability, the micrometeorological measurements suggested that N2O emissions might be considerably larger than those predicted by NGGIC algorithms which use emission factors of 0.4% for urine and 1.25% for dung, but appear to be predicted more closely by IPCC algorithms which use 2% for both. The study has indicated ways to improve the precision of relevant micrometeorological approaches.

Methane emissions from a flock of 14, 1-year old sheep grazing on a grass and legume pasture were measured using a micrometeorological mass-balance method and a sulphur hexaflouride (SF 6 ) tracer technique. The former measured the mean emission, over 45 min intervals, from all the sheep within a fenced 24 m×24 m enclosure, from the enrichment of methane (CH 4 ) in air as it passed over the sheep. The tracer technique measured emissions from a subset of 7 individual animals over 24 h periods from measurements of CH 4 and SF 6 concentrations in air exhaled by the sheep, and from the known rate of release of SF 6 from small permeation tubes placed in the animals’ rumens. Both methods gave highly similar results for 4 out of 5 days. When the species composition of dietary intake was steady during the last two days of measurement, the mean emission rate from the mass-balance method was 11.9±1.5 (SEM) g CH 4 sheep -1 d -1 , while the rate from the tracer technique was 11.7±0.4 (SEM) g CH 4 sheep -1 d -1 . These rates are for sheep with mean live mass of 27 kg, with a measured dry matter intake of 508 g sheep -1 d -1 and pasture dry matter digestibility of 69.5%. There was close agreement between these measurements and estimates from algorithms used to predict methane emissions from sheep for the Australian National Greenhouse Gas Inventory.

Two dimensional manganese stearate films incorporating radioactive 54 Mn have been produced using the Langmuir–Blodgett technique. Low temperature nuclear orientation measurements on these films show a degree of magnetic order even in zero applied magnetic field; a result which is discussed in relation to the Mermin–Wagner theorem which rules out ordering of Heisenberg spins in low dimensional systems with continuously symmetric interactions.

The surface pressure-area isotherms of monolayers of several phospholipids are markedly altered by the presence of phosphotungstate ions in the aqueous subphase at low values of pH (Gorwyn, D.; Barnes, G. T. Langmuir 1990, 6, 222). These changes have now been studied by grazing incidence synchrotron X-ray diffraction. Where the monolayer was in a condensed monolayer state the 2 theta scans revealed a single peak consistent with hexagonal packing of the acyl chains despite the diacyl structure of the phospholipids. Addition of phosphotungstate to the subphase at pH 2 caused this peak to disappear, suggesting a disruption of the regular chain packing, and examination of the concomitant surface pressure-area isotherms showed that there had been a transition from a condensed to an expanded phase.

Queensland fruit fly (Q-fly), Bactrocera tryoni (Froggatt), is a major insect pest of horticultural crops in Australia. Cuelure is the most commonly used attractant for monitoring as well as for management of Q-fly populations through the male annihilation technique and mass trapping. There has been some concern that cuelure is susceptible to hydrolysis, which would limit its usefulness under conditions of high humidity and give rise to inconsistent fly population monitoring. To give some insight into the hydrolysis of cuelure and two closely related compounds, melolure and a newly developed lure, 4-(4-(2,2,2-trifluoroacetoxy)phenyl)-2-butanone (RKTA), the kinetics of hydrolysis of these compounds were quantitatively investigated by gas chromatography–flame ionization detection. From the experimental data, we found the hydrolysis half-lives of cuelure, melolure, and RKTA, at a water concentration of 25 mol L–1, to be ~20 days, 22 h, and 1.2 min respectively. When extrapolated to a water concentration of 1.3 mmol L–1, corresponding to atmospheric conditions of 100 % relative humidity at 25°C, the half-lives are ~1660, ~51, and ~1.4 years respectively.

Rotational tunnelling of ammonia in the two-dimensional metal–ammonia solid solutions formed by high-stage caesium graphite intercalates is reported and used to define the adsorption site structure in these systems. Different stages and stoichiometries CnCs(NH3)x have been measured for 1.5 < T/K < 90 using high-resolution neutron scattering to obtain the dependence on stage and temperature of the tunnelling energies. Prominent transitions at 89 µeV (high fillings) and at 89 and 126 µeV (low fillings) indicate sensitivity to the ammonia content with multiple adsorption sites and threefold symmetry for the hindering potential. The activation energy for quenching the 89 µeV transitions is 6 meV, corresponding to a major peak in the vibrational density of states but not the expected E01 torsional transition energy. The bearing of these results on recent theories for the temperature dependence of tunnelling is discussed.

The effect of drought on plant isoprene emission varies tremendously across species and environments. It was recently shown that an increased ratio of photosynthetic electron transport rate (ETR) to net carbon assimilation rate (NAR) consistently supported increased emission under drought. In this commentary, we highlight some of the physiological aspects of drought tolerance that are central to the observed variability. We briefly discuss some of the issues that must be addressed in order to refine our understanding of plant isoprene emission response to drought and increasing global temperature.

Continuous records of isotope behaviour in the environment are invaluable to understanding mass and energy fluxes. Although techniques such as isotope ratio mass spectrometry provide high precision data, they are not well suited to the analysis of a large number of samples and are currently restricted to use in the laboratory. Fourier transform infrared spectrometers are relatively cheap and sufficiently portable and robust to be taken into the field to collect continuous records of gas-phase isotope behaviour. Several examples of the application of this technique will be presented. One data set provides half-hourly determinations of vertical profiles of D/H in water vapour above agricultural fields over a 3-week period; the same infrared spectra can also be used to determine 13C/12C in CO2. The technique has also been applied to the study of CO2 in ambient air and in a limestone cave system. Some of the features and complications associated with the method will also be considered.

We have used FTIR spectroscopy for high precision trace gas analysis combined with micrometeorological flux-gradient and chamber methods to measure the fluxes of trace gases CO2, CH4, N2O and CO between agricultural soils and the atmosphere. In flux gradient measurements, vertical profiles of the trace gases were measured every 30 minutes from the ground to 22 m. When combined with independent micrometeorological measurements of heat, water vapor and radiative fluxes, trace gas fluxes from the underlying surface could be determined. In chamber measurements, a closed chamber was placed over the soil surface and the air in the chamber monitored continuously by FTIR spectroscopy. Fluxes were calculated from the time rate of change of concentrations in the chamber after closure. The FTIR measurements were fully automated and ran reliably for several weeks, routinely obtaining precision of 0.1–0.5%.

The interactions of myelin basic protein with micelles of lysophosphatidylcholine detergents of different acyl chain lengths were investigated by circular dichroism (CD), small-angle X-ray scattering, Fourier transform infrared spectroscopy (FT-IR), and 1H, 13C and 31P nuclear magnetic resonance spectroscopy (NMR). Circular dichroic, FT-IR, and 1H NMR measurements indicated that the conformational changes induced in the protein molecules by association with micelles depended on the acyl chain length of the detergents. Size is one of the physical properties of micelles which is a function of the length of the acyl chains. The radii of gyration of detergent micelles in complexes with the protein measured by small-angle X-ray scattering indicated that the average size of the micelles was a quadratic function of the acyl chain length. The dependence of the protein conformational changes on micelle size was used to ascertain the order in which different protein segments associate with the detergents. Several procedures were employed to change the fluidity of micelles formed with detergents of given acyl chain lengths. The conformational changes observed on the MBP molecule by varying the micelle properties without changing the length of the chain, suggested that the changes depended on the size and fluidity of the micelles.

The stoichiometry of dodecylphosphocholine/palmitoyllysophosphatidic acid/myelin basic protein complexes and the location of the protein in the micelles have been investigated by electron paramagnetic resonance, ultracentrifugation, small-angle X-ray scattering, 31P, 13C, and 1H nuclear magnetic resonance spectroscopy, and electron microscopy. Ultracentrifugation measurements indicated that well-defined complexes are formed by association of one protein molecule with approximately 133 detergent molecules. The spin-labels 5-, 12-, and 16-doxylstearate have been incorporated into detergent/protein aggregates. Electron paramagnetic resonance spectral parameters and 13C and 1H nuclear magnetic resonance relaxation times showed that the addition of myelin basic protein does not affect the environment and location of the labels or the organization of the micelles. Previous results suggesting that the protein lies primarily near the surface of the micelles have been confirmed by comparing 13C spectra of the detergents with and without protein with spectra of detergent/protein aggregates containing the spin labels. Electron micrographs of the complexes taken by using the freeze-fracture technique revealed the presence of particles with an estimated radius about three times the radius of the micelles measured by small-angle X-ray scattering. The structural integrity of the complexes appears to be based on intramolecular protein interactions as well as protein-detergent interactions.

Ion solvation and association behaviour has been studied for solutions of lithium perchlorate and lithium nitrate in N,N-dimethylformamide (DMF) methanol and ethanol. The techniques of Raman spectroscopy and multinuclear n.m.r. have been employed, and in some studies the cation has been caged in the cryptand Kryptofix 221. Solvation in DMF was examined through quantitative analysis of the OCN bending vibrational band of the DMF in the Raman spectra. A range of univalent and divalent cations was employed and solvation numbers and some information on solvation geometries were obtained. In alcohol solutions determination of solvation numbers was not possible but the involvement of Li+ and NO–3 produced observable spectroscopic changes, while the ClO–4 anion appeared to have only a weak solvation. Evidence for at least two associated species was obtained for both salts in DMF and ethanol and the concentration dependence of the species was determined. In methanol association was much less with the behaviour approaching that observed in aqueous solution.