Drought and resprouting plants

Many species have the ability to resprout vegetatively after a substantial loss of biomass induced by environmental stress, including drought. Many of the regions characterised by ecosystems where resprouting is common are projected to experience more frequent and intense drought during the 21st Century. However, in assessments of ecosystem response to drought disturbance there has been scant consideration of the resilience and post-drought recovery of resprouting species. Systematic differences in hydraulic and allocation traits suggest that resprouting species are more resilient to drought-stress than nonresprouting species. Evidence suggests that ecosystems dominated by resprouters recover from disturbance more quickly than ecosystems dominated by nonresprouters. The ability of resprouters to avoid mortality and withstand drought, coupled with their ability to recover rapidly, suggests that the impact of increased drought stress in ecosystems dominated by these species may be small. The strategy of resprouting needs to be modelled explicitly to improve estimates of future climate-change impacts on the carbon cycle, but this will require several important knowledge gaps to be filled before resprouting can be properly implemented.

Parasitoids select plants more heavily infested with their caterpillar hosts: a new approach to aid interpretation of plant headspace volatiles

Plants produce volatile organic compounds (VOCs) in response to herbivore attack, and these VOCs can be used by parasitoids of the herbivore as host location cues. We investigated the behavioural responses of the parasitoid Cotesia vestalis to VOCs from a plant–herbivore complex consisting of cabbage plants (Brassica oleracea) and the parasitoids host caterpillar, Plutella xylostella. A Y-tube olfactometer was used to compare the parasitoids' responses to VOCs produced as a result of different levels of attack by the caterpillar and equivalent levels of mechanical damage. Headspace VOC production by these plant treatments was examined using gas chromatography–mass spectrometry. Cotesia vestalis were able to exploit quantitative and qualitative differences in volatile emissions, from the plant–herbivore complex, produced as a result of different numbers of herbivores feeding. Cotesia vestalis showed a preference for plants with more herbivores and herbivore damage, but did not distinguish between different levels of mechanical damage. Volatile profiles of plants with different levels of herbivores/herbivore damage could also be separated by canonical discriminant analyses. Analyses revealed a number of compounds whose emission increased significantly with herbivore load, and these VOCs may be particularly good indicators of herbivore number, as the parasitoid processes cues from its external environment

Volatile profile of Spanish Cistus plants as sources of antimicrobials for industrial applications

Cistus is a plant genus traditionally used in folk medicine as remedy for several microbial disorders and infections. The abundance of Cistus spp. in the Iberian Peninsula together with their ability to renew after wildfire contribute to their profitability as suppliers of functional ingredients. The aim of this study was to provide a comprehensive characterization of the volatile profile of different Cistus plants grown in Spain:Cistus ladanifer L., Cistus albidus L., Cistus salviifolius L., and Cistus clusii Dunal (the latter has not been studied before). A system combining headspace solid-phase microextraction and gas chromatography coupled to mass spectrometry (HS-SPME-GC–MS) was implemented; thereby, the volatile compounds were extracted and analyzed in a fast, reliable and environment-friendly way. A total of 111 volatile compounds were identified, 28 of which were reported in Cistus for the first time. The most abundant components of the samples (mono and sesquiterpenes) have been previously reported as potent antimicrobial agents. Therefore, this work reveals the potential use of the Cistus spp. studied as natural sources of antimicrobial compounds for industrial production of cosmeceuticals, among other applications.

Understanding 2H/1H systematics of leaf wax n-alkanes in coastal plants at Stiffkey saltmarsh, Norfolk, UK

Interpretation of sedimentary n-alkyl lipid d2H data is complicated by a limited understanding of factors controlling interspecies variation in biomarker 2H/1H composition. To distinguish between the effects of interrelated environmental, physical and biochemical controls on the hydrogen isotope composition of n-alkyl lipids, we conducted linked d2H analyses of soil water, xylem water, leaf water and n-alkanes from a range of C3 and C4 plants growing at a UK saltmarsh (i) across multiple sampling sites, (ii) throughout the 2012 growing season, and (iii) at different times of the day. Soil waters varied isotopically by up to 35& depending on marsh sub-environment, and exhibited site-specific seasonal shifts in d2H up to a maximum of 31 per mil. Maximum interspecies variation in xylem water was 38 per mil, while leaf waters differed seasonally by a maximum of 29 per mil. Leaf wax n-alkane 2H/1H, however, consistently varied by over 100 per mil throughout the 2012 growing season, resulting in an interspecies range in the ewax/leaf water values of -79 per mil to –227 per mil. From the discrepancy in the magnitude of these isotopic differences, we conclude that mechanisms driving variation in the 2H/1H composition of leaf water, including (i) spatial changes in soil water 2H/1H, (ii) temporal changes in soil water 2H/1H, (iii) differences in xylem water 2H/1H, and (iv) differences in leaf water evaporative 2H-enrichment due to varied plant life forms, cannot explain the range of n-alkane d2H values we observed. Results from this study suggests that accurate reconstructions of palaeoclimate regimes from sedimentary n-alkane d2H require further research to constrain those biological mechanisms influencing species-specific differences in 2H/1H fractionation during lipid biosynthesis, in particular where plants have developed biochemical adaptations to water-stressed conditions. Understanding how these mechanisms interact with environmental conditions will be crucial to ensure accurate interpretation of hydrogen isotope signals from the geological record.