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• W150079172 abstract "Aquesta tesis es centra en descriure els nivells de la fitotoxicitat de lO3 a Catalunya. En un primer bloc vam descriure els patrons temporals i espacials daquesta fitotoxicitat, i en un segon bloc vam estudiar quines son les causes que la produeixen des duna perspectiva ecofisiologica.1.Seguiment de la fitotoxicitat de lO3 en zones rurals de CatalunyaEs van estudiar les variacions geografiques, estacionals i anuals en la taxa de dany en plantes de tabac (Nicotiana tabacum Bel-W3) i les seves relacions amb les condicions meteorologiques. Tant les concentracions dozo com els danys foliars van ser maxims al final de la primavera/principis destiu. Les concentracions mes altes del contaminant es van detectar a la costa, pero es van detectar majors sensibilitats a la toxicitat de lO3 a les estacions de muntanya. Les concentracions dO3 presentaven bones correlacions amb el dany foliar. Malgrat aixo els danys observats presentaven una amplia varianca en la resposta a escala local, de manera que nomes un 11 % era explicat per lO3. La resposta de les plantes de tabac a les concentracions dO3 i per tant la seva capacitat com a bioindicadors depenia de les condicions ambientals, principalment daquelles que afecten al comportament estomatic com ara el VPD.La integracio i categoritzacio dels valors de dany foliar obtinguts arreu del territori i dels anys de seguiment va mostrar una forta relacio (99 % de la varianca) amb les concentracions dO3 expressades com valors dAOT20. Aixi, i a escala regional N. tabacum cv. Bel-W3 es va mostrar com un bon bioindicador de les concentracions dO3.Tenint en compte els resultats obtinguts de la resposta daquesta especie, proposem el valor d AOT40 (concentracio dO3 acumulada per sobre del llindar de 40 ppbv en condicions diurnes) de 1.28 ppmv·h acumulat per periodes quinzenals, com un llindar a partir del qual podrien produir-se danys en especies sensibles a Catalunya.2. Respostes ecofisiologiques a lO3De lexposicio de Quercus ilex subsp. ilex, Quercus ilex subsp. Ballota, Olea europaea cv. sylvestris i Ceratonia siliqua a diferents concentracions dO3 en condicions controlades (OTC) es varen observar diferents efectes de lO3 sobre lecofisiologia daquestes especies. Durant el segon any dexposicio leficiencia fotoquimica maxima, Fv/Fm, va decreixer en les plantes fumigades especialment en els periodes mes estressants en els sistemes mediterranis (hivern i estiu). En canvi durant el primer any dexposicio si que es va observar un increment en el d13C en dos de les especies estudiades, un increment que es va mantenir en el segon any nomes en C. siliqua. Totes les especies estudiades van presentar reduccions en el contingut de clorofil·la durant el primer any dexposicio, pero aquest efecte no es va mantenir durant el segon any. Les elevades concentracions dO3 van produir canvis en les caracteristiques anatomiques i morfologiques de les fulles dalgunes especies, especialment en el LMA (massa foliar per unitat darea especifica) i el gruix del mesofil. Durant el segon any dexposicio es van detectar disminucions en el contingut de N i un increment en d15N en totes les especies, segurament provocat per un canvi en el patro de retranslocacio lligat a una acceleracio en la senescencia.Els resultats mostren una gradacio en la sensibilitat a l O3 segons lespecie. Les dues subespecies de Q. ilex van presentar la major sensibilitat a lO3 ja que, a concentracions ambientals lO3 va produir canvis en les concentracions de N, de d15N, de clorofil·la, en larea foliar, en LMA i la biomassa. Tot i aixi, sota condicions de fumigacio C. siliqua es va presentar una disminucio del 24%, seguida de les dues subespecies de Q. ilex (12-17%) i dO. europaea (ns).These thesis is focused in the ozone phytotoxicity levels in Catalonia. In a first block we have make a temporal and spatial description of ozone phytotoxicity levels in Catalonia and in a second block we have studied what causes it below an ecophysiological perspective.1. Ozone phytotoxicity levels in CataloniaThe ozone (O3) phytotoxicity in rural areas of Catalonia (N.E. Spain) and the biomonitoring capacity of Bel-W3 tobacco (Nicotiana tabacum) cultivars were assessed by determining the percentage of leaf area injured by ozone in plants of this cultivar exposed from spring to autumn since 1995 to 1999. The study was conducted simultaneously on nine field sites where ground level ozone concentrations and meteorological parameters were continuously monitored. Geographical, seasonal and annual variations of ozone damage rate and their links with meteorological conditions were studied. Ozone concentrations and leaf damage increased at the end of spring and the beginning of summer. Coastal sites generally presented higher O3 concentrations than inland and mountain sites. These mountain sites were the most sensitive ones to ozone toxicity. The ozone concentrations correlated well with ozone injury. However, at this local scale the ozone levels did not fully account for all the observed injury (only 11%). The response of tobacco plants to ozone concentrations and therefore its biomonitoring capacity depended also on different environmental conditions, mainly those linked to stomatal behaviour such as VPD. The categorisation of leaf damage in 10% intervals and its averaging throughout the whole study period and the whole region, strongly improved (99% of variance accounted) the relationship with ozone concentrations expressed as AOT20 (accumulated over a cut off of 20 ppbv). Nicotiana tabacum cv. Bel-W3 is thus a very good biomonitor of ozone concentrations in the long term at the regional scale. Taking into account the phytotoxical response of this sensitive tobacco cultivar, we propose the 1.28 ppmv·h biweekly AOT40 (with a solar radiation threshold of 50 W m-2) as a damage threshold level for sensitive species.2. Ecophysiologycal Ozone effects in four Mediterranean taxa.Four Mediterranean tree taxa: Quercus ilex subsp. ilex, Quercus ilex subsp. ballota, Olea europaea and Ceratonia siliqua, were exposed to different ozone (O3) concentrations in open top chambers (OTCs) during two years. Three treatments were applied: charcoal-filtered air (CF), non-filtered air (NF) and non-filtered air plus 40 ppbv of O3 (NF+). The photochemical maximal efficiency, Fv/Fm, decreased in NF+ plants during the second year of exposure, especially during the most stressful Mediterranean seasons (winter and summer). An increase of _13C was found in three of the four studied species during the first year of exposure. This finding was only maintained in C. siliqua during the second year. Decreases in the chlorophyll content were detected during the first year of fumigations in all the studied species, but not during the second year. The NF+ treatment induced changes in foliar anatomical characteristics, especially in LMA (leaf mass area) and spongy parenchyma thickness, which increased in some species. A reduction in N content and an increase in d15N were found in all species during the second year when exposed in the NF+ OTCs, suggesting a change in their retranslocation pattern linked to an acceleration of leaf senescence, as also indicated by the above mentioned biochemical and anatomical foliar changes. The two Q. ilex subspecies were the most sensitive species since the changes in N concentration, d15N, chlorophyll, leaf area, LMA and biomass occurred at ambient O3 concentrations. However, C. siliqua was the most responsive species (24% biomass reduction) when exposed to the NF+ treatment, followed by the two Q. ilex subspecies (12-17%) and O. europaea (ns)." @default.
• W150079172 created "2016-06-24" @default.
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• W150079172 date "2004-03-10" @default.
• W150079172 modified "2023-09-24" @default.
• W150079172 title "La fitotoxicitat de l'ozó a Catalunya. Bioindicació i ecofisiologia" @default.
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