Analysis and experimentation on ecosystems

Volatile organic compounds (VOC) emitted from terrestrial vegetation constitute complex olfactory environments (odorscapes) and play major roles in the interactions between organisms. Insects for instance, extract essential cues for their reproduction from their olfactory environment. Plant VOC production and emission are affected by environmental parameters, such heat and drought. As part of ODORSCAPE, a research program funded by French ANR, the effects of combined elevated atmospheric ozone and CO2 concentrations on plant VOC production are studied, by assessing the stress-induced variations in the VOC emissions and in the corresponding biosynthesis pathways. Two crops representative of temperate agro-ecosystems, maize and poplar, are considered in this study. For CO2, 400 ppm or 800 ppm are applied to plants, starting at the germination step for maize and at the acclimatization step for poplar, while 30 ppb or 110 ppb of ozone are applied on fully developed plants, during 6h of the photoperiod, for 2 weeks. At the end of the four treatment combinations, photosynthetic and gas exchange parameters, and VOC emissions are measured and will be related to changes in the potential activity of key enzymes in the major VOC biosynthetic pathways (such as the lipoxygenase, mevalonate and methylerythritol phosphate pathways) and carbon fixing metabolisms (RubisCO and PEP carboxylase). This will allow us to evaluate the extent of photosynthetic carbon allocation toward VOC biosynthesis pathways in response to both elevated ozone and CO2. In addition, the stress-induced odorscapes will be tested for their effects on olfaction of herbivorous insects at gene, neural coding and behavior levels. Together, the results of this multidisciplinary project should reveal new aspects of the ecological consequences of climate change.