Influence of abiotic stress factors on VOCs emission from Portuguese rice paddy fields: relation with increased climate change

Dissertação para obtenção do Grau de Mestre em Engenharia do Ambiente Perfil de Gestão de Sistemas Ambientais

Plants are emitting chemical-signals to the atmosphere in response to stress factors - Volatile Organic Compounds (VOCs). VOCs have higher influence on atmosphere chemistry: they are acting as photochemical precursors in tropospheric ozone formation. Present work studies VOCs emission released by rice (Oryza sativa L cv. Aríete) cycle in paddy fields, in aleatory schemes with three replicates, in two separate soil plots with different textures (silty clay and loamy sand), studying open field conditions and open top chambers (OTCs) under influence of treatments with induced abiotic stress (increase temperature and simultaneously temperature and CO2 atmospheric concentration enhancement). VOCs were extracted from plant by solid phase micro extraction (SPME) and stem distillation extraction (SDE), and analyzed by gas chromatography coupled to mass spectrometry (GC/MS) using two GC capillary columns with different polarities, one non-polar (DB-5) and other polar (DB-WAX). A total of 33 VOCs using a non-polar column and 22 VOCs using a polar column, in both set of results were identified the three main classes of compounds: green leaf volatiles (GLV), monoterpenes and sesquiterpenes. Between rice cycle VOCs vary their trend and on vegetative stage were observed more VOCs, followed by ripening and lesser on reproductive. Silty clay soil demonstrated higher amount of VOCs released if compared with loamy sand texture. Between OTCs, more compounds were released by increasing temperature than simultaneously temperature and CO2. In Intergovernmental Panel for Climate Change (IPCC) scenarios with emergent trend of increasing temperature and CO2 atmospheric concentration, two effects are inherent to rice VOCs emission, one negative with higher emission related with temperature and other positive with less emission associated CO2. Field data measurements addictions in air quality models will help achievements of realistic previsions and better understand the effect of climate change in air quality on a global scale.

Portuguese Foundation for Science and Technology; FCT-UNL and partners from INIAV and UTAD, on a project named PTDC/AGR-AAM/102529/2008