"Citrus plants are largely grown and economically valuable crops in densely inhabited and polluted Mediterranean areas. Citrus species produce and emit VOC (Volatile Organic Compounds) which enter gas-phase reactions leading to formation of dangerous levels of atmospheric ozone especially in the presence of anthropogenic pollutants. On the other hand, biogenic VOC destroy ozone at leaf level enhancing plant protection against the pollutant. CITROVOC is keyed at understanding the dual role of VOC emitted by Citrus in regulating ozone formation and deposition in Mediterranean areas that are plagued by high ozone episodes. A three-year study, at cellular, whole plant, and ecosystem level, is proposed to understand basic mechanisms leading to ozone interactions with BVOC, to quantify VOC-dependent ozone removal, and to scale up results at community level. Temporal and spatial variations of stomatal ozone uptake, and VOC-induced ozone destruction or ozone formation in the low troposphere will be assessed. The ozone-VOC chemistry will be studied as functions of genetics, phenology, environment, and agricultural practices. The outstanding expertise of the host Institutions, spanning from plant biology to atmospheric chemistry, will allow the applicant to consolidate the strong, interdisciplinary background needed to undertake complex and novel studies about biosphere-atmosphere interactions and their impact on a changing environment. CITROVOC results will usefully complement or upgrade VOC and pollution emission models, contributing to practices and policies for the improvement of air quality and plant protection."