Probabilistic health risk of volatile organic compounds (VOCs): Comparison among different commuting modes in Guangzhou,China

Probabilistic risk assessment was conducted to evaluate health risks caused by eight volatile organic compounds (VOCs) (benzene, toluene, xylene, ethylbenzene, styrene, formaldehyde, acetaldehyde, and acrolein) in five commuting modes (car, air-conditioned bus, non-air-conditioned bus, subway, and bicycle) in Guangzhou. Monte Carlo method and the contribution to variance method were applied to obtain the more scientific evaluation results and the more influential variables. The results revealed that the carcinogenic risk of air-conditioned bus and car were the highest, followed by bicycle, non-air-conditioned bus, and subway. The probability of the risk exceeding 10^?6 was approximately 90%, 62%, 62%, 91%, and 92%, respectively. Moreover, the noncarcinogenic risk of air-conditioned bus and car were the highest, followed by non-air-conditioned bus, bicycle, and subway. It indicated that subway, non-air-conditioned bus, and bicycle are better commuting choices for city dwellers to reduce health risks and alleviate traffic pressure. Formaldehyde, benzene, and acrolein contribute to a significant proportion in health risk and should be the prior controlled organic pollutants. Sensitivity analysis suggests that exposure time is the most influential parameter for carcinogenic and noncarcinogenic risk, followed by concentrations of VOCs in air and exposure duration.     

Making sense of nectar scents: the effects of nectar secondary metabolites on floral visitors of Nicotiana attenuata

Flowers produce a plethora of secondary metabolites but only nectar sugars, floral pigments and headspace volatiles have been examined in the context of pollinator behavior. We identify secondary metabolites in the headspace and nectar of glasshouse- and field-grown Nicotiana attenuata plants, infer within-flower origins by analyzing six flower parts, and compare the attractiveness of 16 constituents in standardized choice tests with two guilds of natural pollinators (Manducasexta moths and Archilochus alexandri and Selasphorus rufus hummingbirds) and one nectar thief (Solenopsis xyloni ants) to determine whether nectar metabolites can 'filter' flower visitors: only two could. Moths responded more strongly than did hummingbirds to headspace presentation of nicotine and benzylacetone, the most abundant repellent and attractant compounds, respectively. For both pollinators, nectar repellents decreased nectaring time and nectar volume removed, but increased visitation number, particularly for hummingbirds. Fewer ants visited if the nectar contained repellents. To determine whether nicotine reduced nectar removal rates in nature, we planted transformed, nicotine-silenced plants into native populations in Utah over 2 years. Plants completely lacking nicotine in their nectar had 68-70% more nectar removed per night by the native community of floral visitors than did wild-type plants. We hypothesize that nectar repellents optimize the number of flower visitors per volume of nectar produced, allowing plants to keep their nectar volumes small.     

杉木挥发性有机物释放特征研究

为了明确杉木(Cunninghamialanceolata)挥发性有机物(VOCs)的成分组成和含量的变化规律,采用动态顶空采集法和热脱附-气质联用(TDS-GC-MS)技术,对杉木释放的VOCs成分组成和相对含量的季节性变化进行分析。结果表明,杉木释放的VOCs中共鉴定出60种化合物,一年中释放的化合物种数随季节变化呈先升后降的趋势,夏季释放种类最多,达42种。检测到的烷烃类、醛类、酯类和醇类化合物种类最多,占检测到的化合物总种类数的73.33%。春季杉木释放的VOCs以醇类化合物为主,总相对含量为27.19%;夏季以萜烯类化合物为主,总相对含量为17.29%;秋季以醛类化合物为主,总相对含量为23.55%。综上,杉木具有一定的康养功效,夏季是在杉木林中进行康养活动的最佳时期。     

Action of jasmonates in plant stress responses and development — Applied aspects

Jasmonates (JAs) are lipid-derived compounds acting as key signaling compounds in plant stress responses and development. The JA co-receptor complex and several enzymes of JA biosynthesis have been crystallized, and various JA signal transduction pathways including cross-talk to most of the plant hormones have been intensively studied. Defense to herbivores and necrotrophic pathogens are mediated by JA. Other environmental cues mediated by JA are light, seasonal and circadian rhythms, cold stress, desiccation stress, salt stress and UV stress. During development growth inhibition of roots, shoots and leaves occur by JA, whereas seed germination and flower development are partially affected by its precursor 12-oxo-phytodienoic acid (OPDA). Based on these numerous JA mediated signal transduction pathways active in plant stress responses and development, there is an increasing interest in horticultural and biotechnological applications. Intercropping, the mixed growth of two or more crops, mycorrhization of plants, establishment of induced resistance, priming of plants for enhanced insect resistance as well as pre- and post-harvest application of JA are few examples. Additional sources for horticultural improvement, where JAs might be involved, are defense against nematodes, biocontrol by plant growth promoting rhizobacteria, altered composition of rhizosphere bacterial community, sustained balance between growth and defense, and improved plant immunity in intercropping systems. Finally, biotechnological application for JA-induced production of pharmaceuticals and application of JAs as anti-cancer agents were intensively studied.     

Formation of 2′-5′ Phosphodiester Linkages in Polyribonucleotides

Unlike technical grade yeast RNA, which was confirmed to contain several per cent of 2′–5′ phosphodiester linkages, RNA prepared from different kinds of commercial yeast in a cold room consisted exclusively of 3′–5′ phosphodiester linkages. Heat treatment of the 3′–5′ linked RNA solution resulted in partial isomerization of the internucleotide linkage of the polynucleotide chain (C₃′-C₅′->C₂′-C₅′). The isomerization of RNA occurred in the presence of water, at high temperature, and under acidic conditions. Treatment of dry RNA at 100°C for 2hr did not result in any detectable isomerization. The isomerization was actually observed in yeast RNA when yeast cells suspended in sodium chloride solution were heated. It is concluded therefore that 2′-5′ phosphodiester linkages found in technical grade RNA had been formed neither at a step of precipitating RNA with acid nor at a step of drying RNA, but had been formed at a step of heat extraction of RNA from yeast. When 0.1 % poly (A) solution, pH 4.8, was heated for 20 hr in a boiling water bath, the isomerization proceeded during the first 6hr, and finally reached about 37%, irrespective of chain length.     

Chemodiversity in the Fingerprint Analysis of Volatile Organic Compounds (VOCs) of 35 Old and 7 Modern Apple Cultivars Determined by Proton‐Transfer‐Reaction Mass Spectrometry (PTR‐MS) in Two Different Seasons

Volatile organic compounds (VOCs) are chemical species that play an important role in determining the characteristic aroma and flavor of fruits. Apple (Malus × domestica Borkh .) cultivars differ in their aroma and composition of VOCs. To determine varietal differences in the aroma profiles, VOCs emitted by 7 modern and 35 old apple cultivars were analyzed using Proton Transfer Reaction Mass Spectrometry (PTR‐MS). PTR‐MS is a rapid, reproducible, and non‐destructive spectrometric technique for VOC analysis of single fruits, developed for direct injection analysis. In the present study, we analyzed the differences in the emission of VOCs from single fruits at harvest and after a storage period of 60±10 days, followed by 3 d of shelf life. Our results show that VOC profile differences among apple cultivars were more pronounced after storage than at harvest. Furthermore, chemodiversity was higher in old cultivars compared to modern cultivars, probably due to their greater genetic variability. Our data highlight the importance of storage and shelf life are crucial for the development of the typical aroma and flavor of several apple cultivars. The validity of the method is demonstrated by comparison of two different harvest years.     

Diversity of Physiological and Biochemical Characters of Microdochium Fungi

The biological characterization of Microdochium majus, M. nivale, and M. seminicola strains with wide geographical origins showed the diversity of their pathogenic properties and metabolite compounds, allowing them to exist in their habitats. Significant differences in the ability of Microdochium fungi to cause lesions on wheat and oat leaves were found. The intensity of symptoms depended on the species and substrate origin of the strains. On average M. seminicola strains were able to cause less leaf necrosis than M. majus and M. nivale. The volatile organic compound (VOC) profile of Microdochium fungi included 29 putative fungal metabolites. The spectrum of the identified VOCs in M. seminicola strains was much richer than that in M. majus and M. nivale strains. In addition, the strains of M. seminicola emitted at least six sesquiterpenes. Mycotoxin analysis by HPLC/MS/MS revealed that the analyzed Microdochium strains did not produce any toxic metabolites typically produced by filamentous fungi.     

Root damage to apple plants by cockchafer larvae induces a change in volatile signals below‐ and above‐ground

Volatile organic compounds (VOCs) mediate communication between plants and insects. Plants under insect herbivore attack release VOCs either at the site of attack or systemically, indicating within‐plant communication. Some of these VOCs, which may be induced only upon herbivore attack, recruit parasitoids and predatory insects to feed on the attacking insects. Moreover, some plants are able to ‘eavesdrop’ on herbivore‐induced plant volatiles (HIPVs) to prime themselves against impending attack; such eavesdropping exemplifies plant–plant communication. In apple orchards, the beetle Melolontha melolontha L. (Coleoptera: Scarabaeidae) is an important insect pest whose larvae live and feed on roots for about 4 years. In this study, we investigated whether the feeding activity of M. melolontha larvae (1) alters the volatile profile of apple roots, (2) induces the release of HIPVs systemically in the leaves, and (3) whether infested plants communicate to neighbouring non‐infested conspecifics through HIPVs. To answer these questions, we collected constitutive VOCs from intact M9 roots as well as M. melolontha larvae‐damaged roots using a newly designed ‘rhizobox’, to collect root‐released volatiles in situ, without damaging the plant root system. We also collected VOCs from the leaf‐bearing shoots of M9 whose roots were under attack by M. melolontha larvae and from shoots of neighbouring non‐infested conspecifics. Gas chromatography‐mass spectrometry analysis showed that feeding activity of M. melolontha larvae induces the release of specific HIPVs; for instance, camphor was found in the roots only after larvae caused root damage. Melolontha melolontha also induced the systemic release of methyl salicylate and (E,E)‐α‐farnesene from the leaf‐bearing shoots. Methyl salicylate and (E,E)‐α‐farnesene were also released by the shoots of non‐infested neighbouring conspecifics. These phenomena indicate the induction of specific VOCs below‐ and above‐ground upon M. melolontha larvae feeding on apple roots as well as plant–plant communication in apple plants.