Biogenic volatile organic compound and respiratory CO₂ emissions after ¹³C-labeling: online tracing of C translocation dynamics in poplar plants

Background: Globally plants are the primary sink of atmospheric CO2, but are also the major contributor of a large spectrum of atmospheric reactive hydrocarbons such as terpenes (e.g. isoprene) and other biogenic volatile organic compounds (BVOC). The prediction of plant carbon (C) uptake and atmospheric oxidation capacity are crucial to define the trajectory and consequences of global environmental changes. To achieve this, the biosynthesis of BVOC and the dynamics of C allocation and translocation in both plants and ecosystems are important. Methodology: We combined tunable diode laser absorption spectrometry (TDLAS) and proton transfer reaction mass spectrometry (PTR-MS) for studying isoprene biosynthesis and following C fluxes within grey poplar (Populus x canescens) saplings. This was achieved by feeding either 13CO2 to leaves or 13C-glucose to shoots via xylem uptake. The translocation of 13CO2 from the source to other plant parts could be traced by 13C-labeled isoprene and respiratory 13CO2 emission. Principal Finding: In intact plants, assimilated 13CO2 was rapidly translocated via the phloem to the roots within 1 hour, with an average phloem transport velocity of 20.3±2.5 cm h21. 13C label was stored in the roots and partially reallocated to the plants’ apical part one day after labeling, particularly in the absence of photosynthesis. The daily C loss as BVOC ranged between 1.6% in mature leaves and 7.0% in young leaves. Non-isoprene BVOC accounted under light conditions for half of the BVOC C loss in young leaves and one-third in mature leaves. The C loss as isoprene originated mainly (76–78%) from recently fixed CO2, to a minor extent from xylem-transported sugars (7–11%) and from photosynthetic intermediates with slower turnover rates (8–11%). Conclusion: We quantified the plants’ C loss as respiratory CO2 and BVOC emissions, allowing in tandem with metabolic analysis to deepen our understanding of ecosystem C flux

BVOC fluxes from a bioenergy maize plantation

Germany, and other countries as well, intends to largely increase the plantation area for bioenergy production in the near future. Potential plant species that are likely to be intensively cultivated are corn, energy grasses, and woody crops, which might emit biogenic volatile organic compounds (BVOC) at higher rates than common agricultural species. Due to the reactivity of some BVOCs with oxidizing atmospheric compounds, future land-cover changes and the extension of plantation area might affect air quality and the formation of secondary organic aerosols with potential consequences for the local climate. In the current project, we measured the BVOC fluxes from maize plants on an agricultural site in Northeastern Germany using automated large chambers (5.625 m3) and online detection of BVOCs by proton transfer mass spectrometry (PTR-MS). BVOC fluxes were continuously followed for 7 weeks, from the flowering of the plants to the senescence stage. The highest fluxes were observed for sesquiterpenes, monoterpenes, and acetone during grain development and ripening. After the ripening process mainly monoterpenes and acetone still show substantial emission rates

Water droplet evaporation at high pressure and temperature levels - Part i: Experimental investigations of spray patterns at varied test conditions

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.Water injection into gas turbines is subject of investigations since decades, due to a high power and efficiency augmentation potential compared to the simple gas turbine cycle. Based on former research at ambient conditions, some technologies have already been realized, e.g. inlet fogging. Further applications of water injection at higher temperature and pressure levels are limited, because of few experimental data. In order to gain fundamental understanding at these boundary conditions, a novel test facility for droplet evaporation investigations has been built up at the University of Duisburg-Essen. The resulting spray patterns are recorded by a laser based measuring technology, Phase Doppler Particle Analyzer (PDPA). Part I of the paper treats the experimental setup of the test facility; in particular the laser based measuring technology, as well as the measurement results of the spray pattern produced from a nozzle at high pressure and temperature levels. The focus of the investigations is on the droplet evaporation process in dependence on parameter variation of the environmental conditions.dc201

Water droplet evaporation at high pressure and temperature levels – part II: comparison of experimental results with a 1D simulation

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.Water injection into gas turbines is subject of investigations since decades, due to a high power and efficiency augmentation potential compared to the simple gas turbine cycle. Based on former research at ambient conditions, some technologies have already been realized, e.g. inlet fogging. Further applications of water injection at higher temperature and pressure levels are limited, because of few experimental data. In order to gain fundamental understanding at these boundary conditions, a novel test facility for droplet evaporation investigations has been built up at the Department of Mechanical Engineering at University of Duisburg-Essen. The resulting spray patterns are recorded by a laser based measuring technology, Phase Doppler Particle Analyzer (PDPA). In this second part of the paper, experimental results from the test facility are compared to simulation results of a 1D- model for droplet evaporation. The focus of this investigation is on the accordance of the simulation results with the experimental data at high pressure and temperature levels.dc201

Isoprene interferes with the attraction of bodyguards by herbaceous plants

Isoprene is the most abundant volatile compound emitted by vegetation. It influences air chemistry and is part of plant defense against abiotic stresses. However, whether isoprene influences biotic interactions between plants and other organisms has not been investigated to date. Here we show a new effect of isoprene, namely its influence on interactions between plants and insects. Herbivory induces the release of plant volatiles that attract the herbivore's enemies, such as parasitic wasps, as a kind of bodyguard. We used transgenic isoprene-emitting Arabidopsis plants in behavioral, chemical, and electrophysiological studies to investigate the effects of isoprene on ecological interactions in 2 tritrophic systems. We demonstrate that isoprene is perceived by the chemoreceptors of the parasitic wasp Diadegma semiclausum and interferes with the attraction of this parasitic wasp to volatiles from herbivore-infested plants. We verified this repellent effect on D. semiclausum female wasps by adding external isoprene to the volatile blend of wild-type plants. In contrast, the antennae of the parasitic wasp Cotesia rubecula do not perceive isoprene and the behavior of this wasp was not altered by isoprene emission. In addition, the performance of the 2 examined lepidopteran herbivores (Pieris rapae and Plutella xylostella) was not affected by isoprene emission. Therefore, attraction of parasitic wasps to host-infested herbaceous plants in the neighborhood of high isoprene emitters, such as poplar or willow, may be hampered by the isoprene emission that repels plant bodyguard