Atmospheric ozone action on multiple functions of volatile organic compounds from native plants

Abstract

Volatile organic compounds (VOCs) emitted by plants participate in numerous functions in the biological and chemical environment. They signal the interaction plant-insect and also act on the chemical defenses of plants and plant-plant communication. There is substantial evidence that plants attacked by insects induce the formation of new VOCs which are not produced by healthy plants.These volatiles, called inducible volatiles, are also sensed by herbivores and preys, acting as natural repellents. Also, the inducible volatiles participate in atmospheric chemistry, scavenging ozone and hydroxyl radicals as well as producing secondary organic aerosol. These processes can reduce the atmospheric levels of these volatiles so that the bouquet could no longer be sensed by the organisms. In this way, there might be the disruption and /or breakdown of trophic interactions and other ecological functions mediated by these compounds.The fragmentation of natural ecosystems leads to more native species being exposed to contaminated atmospheres and, therefore, there might be a better understanding of the contaminant effects in the ecological interactions. Ozone is a phytotoxic atmospheric pollutant of major worldwide concern, being ambiguous and present in concentrations of risk to the vegetal ecosystems. However, the VOCs emitted by plants are strongly reactive with ozone, generating subparticles which lead to the formation of secondary aerosol, made up of a mixture of organic complex containing semi-volatile compounds with similar chemical structures of the original volatile. Moreover, these particles can be deposited on the leaves themselves, preventing the stomatal opening and the release of more volatiles. Also, semi-volatiles from subparticles could have the same role in the interactions of those original volatiles. Thus, the action of ozone in the functions of volatiles in the environment can be either overwhelming or void, and this may also be dependent upon the adaptation of plants to the atmosphere. So, this fact could lead to the inactivation of the current VOC and /or the generation of the most active volatiles in ecological interactions and the less active ones in atmospheric chemistry. The project proposed aims to elucidate the action of ozone on ecological interactions mediated by volatile organic compounds from native plants, such as Astronium graveolens Jacq., Croton floribundus Spreng. and Piptadenia gonoacantha (Mart.) Macbr. Thus, the development of the project may help to understand the many questions about the disturbances in vegetal ecosystems promoted by the polluted atmosphere. (AU)