• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 7
  • 7
  • 3
  • 2
  • 1
  • Tagged with
  • 22
  • 6
  • 5
  • 5
  • 4
  • 4
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Um lugar ao sol : a influência do fator histórico sobre o nicho de luz e respostas ecofisiológicas de plantas com semente da floresta ombrófila mista

Fagundes, Paula Braga January 2013 (has links)
Em ambientes florestais, a luz é o recurso que com mais frequência limita o crescimento, a sobrevivência e a reprodução em plantas. Assim, a variação na disponibilidade de luz no sub-bosque influencia a composição local de espécies lenhosas, que se segregam em diferentes nichos de luz de acordo com suas preferências e tolerâncias, conferidas através de suas adaptações e plasticidade fenotípica. Os atributos das espécies atuais, além de serem adaptados ao ambiente onde vivem, são um legado de seus ancestrais, motivo pelo qual espécies mais próximas filogeneticamente, com frequência compartilham atributos semelhantes e, por consequência, ocupam nichos similares, padrão conhecido como conservação filogenética. Estudos recentes mostram que atributos funcionais relacionados à captação de luz teriam se diversificado através de diferentes grupos filogenéticos, conferindo a estes capacidades distintas para a conquista de novos ambientes de luz. Nosso trabalho teve como objetivo detectar a presença de padrões filogenéticos na distribuição e nas respostas ecofisiológicas de oito espécies lenhosas co-ocorrentes e de seus respectivos clados em um sub-bosque florestal, a partir da comparação do nicho de luz e do desempenho de plantas juvenis em resposta ao gradiente luminoso existente. Assim nossas hipóteses são de que 1) as espécies filogeneticamente próximas tem maior semelhança em estratégias adaptativas do que espécies filogeneticamente distantes; 2) a amplitude de nicho e 3) a plasticidade de atributos em resposta à luz aumentam em clados mais derivados. Os resultados apresentados aqui mostraram uma maior similaridade entre as espécies mais relacionadas do que entre aquelas que são filogeneticamente distantes, sugerindo conservação filogenética do nicho. Quanto à amplitude de nicho, também há uma influência filogenética, porém, contrário ao esperado, os clados mais antigos apresentaram um nicho mais amplo. Para a plasticidade dos atributos os resultados aqui apresentados mostram que não há padrões filogenéticos na plasticidade das respostas de espécies e clados estudados, sugerindo o efeito de outros fatores sobre a plasticidade das plantas, como efeitos ontogenéticos ou estresse ambiental. / In forest environments, light is the resource that most often limits the growth, survival and reproduction in plants. Thus, the variation in light availability, regarded as one of the most important resources for woody plants in the understory, results in differences in species composition, which segregate in different light niches according to their preferences and tolerances, conferred by their adaptations and phenotypic plasticity. Extant plant traits are not only adapted to the present environment, they are also a legacy from their ancestors and, for that reason, phylogenetically related species often share similar attributes and consequently occupy similar niches, pattern known as phylogenetic conservatism. Recent studies show that functional traits related to the capture of this resource have diversified across different phylogenetic groups, giving them distinct abilities to occupy new light environments. The present study aimed to detect the presence of phylogenetic patterns in species distribution along a light gradient and in ecophysiological responses of eight co-occurring woody species and their respective clades in a forest understory. This was accomplished by comparing the light niche of juvenile plants in response to the existing light gradient, as well as their physiological plasticity in response to understory light variations. We hypothesized that (1) phylogenetic related species have greater similarity of adaptive strategies, and consequently of their niche, than more distantly related ones; and that (2) the niche breadth is wider and (3) traits plasticity is greater in more recent than in more basal clades. The results presented here showed that there is a greater niche similarity between closely related species than between those that are phylogenetically distant, suggesting niche conservatism. Regarding to niche amplitude, there is also a phylogenetic influence but, contrary to our expectations, the older clades showed a greater niche breadth. For plasticity of selected plant traits, results showed no phylogenetic pattern for the studied species and clades, suggesting that other factors act on the phenotypic plasticity of plants, such as ontogenetic effects and/or environmental stress.
12

Um lugar ao sol : a influência do fator histórico sobre o nicho de luz e respostas ecofisiológicas de plantas com semente da floresta ombrófila mista

Fagundes, Paula Braga January 2013 (has links)
Em ambientes florestais, a luz é o recurso que com mais frequência limita o crescimento, a sobrevivência e a reprodução em plantas. Assim, a variação na disponibilidade de luz no sub-bosque influencia a composição local de espécies lenhosas, que se segregam em diferentes nichos de luz de acordo com suas preferências e tolerâncias, conferidas através de suas adaptações e plasticidade fenotípica. Os atributos das espécies atuais, além de serem adaptados ao ambiente onde vivem, são um legado de seus ancestrais, motivo pelo qual espécies mais próximas filogeneticamente, com frequência compartilham atributos semelhantes e, por consequência, ocupam nichos similares, padrão conhecido como conservação filogenética. Estudos recentes mostram que atributos funcionais relacionados à captação de luz teriam se diversificado através de diferentes grupos filogenéticos, conferindo a estes capacidades distintas para a conquista de novos ambientes de luz. Nosso trabalho teve como objetivo detectar a presença de padrões filogenéticos na distribuição e nas respostas ecofisiológicas de oito espécies lenhosas co-ocorrentes e de seus respectivos clados em um sub-bosque florestal, a partir da comparação do nicho de luz e do desempenho de plantas juvenis em resposta ao gradiente luminoso existente. Assim nossas hipóteses são de que 1) as espécies filogeneticamente próximas tem maior semelhança em estratégias adaptativas do que espécies filogeneticamente distantes; 2) a amplitude de nicho e 3) a plasticidade de atributos em resposta à luz aumentam em clados mais derivados. Os resultados apresentados aqui mostraram uma maior similaridade entre as espécies mais relacionadas do que entre aquelas que são filogeneticamente distantes, sugerindo conservação filogenética do nicho. Quanto à amplitude de nicho, também há uma influência filogenética, porém, contrário ao esperado, os clados mais antigos apresentaram um nicho mais amplo. Para a plasticidade dos atributos os resultados aqui apresentados mostram que não há padrões filogenéticos na plasticidade das respostas de espécies e clados estudados, sugerindo o efeito de outros fatores sobre a plasticidade das plantas, como efeitos ontogenéticos ou estresse ambiental. / In forest environments, light is the resource that most often limits the growth, survival and reproduction in plants. Thus, the variation in light availability, regarded as one of the most important resources for woody plants in the understory, results in differences in species composition, which segregate in different light niches according to their preferences and tolerances, conferred by their adaptations and phenotypic plasticity. Extant plant traits are not only adapted to the present environment, they are also a legacy from their ancestors and, for that reason, phylogenetically related species often share similar attributes and consequently occupy similar niches, pattern known as phylogenetic conservatism. Recent studies show that functional traits related to the capture of this resource have diversified across different phylogenetic groups, giving them distinct abilities to occupy new light environments. The present study aimed to detect the presence of phylogenetic patterns in species distribution along a light gradient and in ecophysiological responses of eight co-occurring woody species and their respective clades in a forest understory. This was accomplished by comparing the light niche of juvenile plants in response to the existing light gradient, as well as their physiological plasticity in response to understory light variations. We hypothesized that (1) phylogenetic related species have greater similarity of adaptive strategies, and consequently of their niche, than more distantly related ones; and that (2) the niche breadth is wider and (3) traits plasticity is greater in more recent than in more basal clades. The results presented here showed that there is a greater niche similarity between closely related species than between those that are phylogenetically distant, suggesting niche conservatism. Regarding to niche amplitude, there is also a phylogenetic influence but, contrary to our expectations, the older clades showed a greater niche breadth. For plasticity of selected plant traits, results showed no phylogenetic pattern for the studied species and clades, suggesting that other factors act on the phenotypic plasticity of plants, such as ontogenetic effects and/or environmental stress.
13

Um lugar ao sol : a influência do fator histórico sobre o nicho de luz e respostas ecofisiológicas de plantas com semente da floresta ombrófila mista

Fagundes, Paula Braga January 2013 (has links)
Em ambientes florestais, a luz é o recurso que com mais frequência limita o crescimento, a sobrevivência e a reprodução em plantas. Assim, a variação na disponibilidade de luz no sub-bosque influencia a composição local de espécies lenhosas, que se segregam em diferentes nichos de luz de acordo com suas preferências e tolerâncias, conferidas através de suas adaptações e plasticidade fenotípica. Os atributos das espécies atuais, além de serem adaptados ao ambiente onde vivem, são um legado de seus ancestrais, motivo pelo qual espécies mais próximas filogeneticamente, com frequência compartilham atributos semelhantes e, por consequência, ocupam nichos similares, padrão conhecido como conservação filogenética. Estudos recentes mostram que atributos funcionais relacionados à captação de luz teriam se diversificado através de diferentes grupos filogenéticos, conferindo a estes capacidades distintas para a conquista de novos ambientes de luz. Nosso trabalho teve como objetivo detectar a presença de padrões filogenéticos na distribuição e nas respostas ecofisiológicas de oito espécies lenhosas co-ocorrentes e de seus respectivos clados em um sub-bosque florestal, a partir da comparação do nicho de luz e do desempenho de plantas juvenis em resposta ao gradiente luminoso existente. Assim nossas hipóteses são de que 1) as espécies filogeneticamente próximas tem maior semelhança em estratégias adaptativas do que espécies filogeneticamente distantes; 2) a amplitude de nicho e 3) a plasticidade de atributos em resposta à luz aumentam em clados mais derivados. Os resultados apresentados aqui mostraram uma maior similaridade entre as espécies mais relacionadas do que entre aquelas que são filogeneticamente distantes, sugerindo conservação filogenética do nicho. Quanto à amplitude de nicho, também há uma influência filogenética, porém, contrário ao esperado, os clados mais antigos apresentaram um nicho mais amplo. Para a plasticidade dos atributos os resultados aqui apresentados mostram que não há padrões filogenéticos na plasticidade das respostas de espécies e clados estudados, sugerindo o efeito de outros fatores sobre a plasticidade das plantas, como efeitos ontogenéticos ou estresse ambiental. / In forest environments, light is the resource that most often limits the growth, survival and reproduction in plants. Thus, the variation in light availability, regarded as one of the most important resources for woody plants in the understory, results in differences in species composition, which segregate in different light niches according to their preferences and tolerances, conferred by their adaptations and phenotypic plasticity. Extant plant traits are not only adapted to the present environment, they are also a legacy from their ancestors and, for that reason, phylogenetically related species often share similar attributes and consequently occupy similar niches, pattern known as phylogenetic conservatism. Recent studies show that functional traits related to the capture of this resource have diversified across different phylogenetic groups, giving them distinct abilities to occupy new light environments. The present study aimed to detect the presence of phylogenetic patterns in species distribution along a light gradient and in ecophysiological responses of eight co-occurring woody species and their respective clades in a forest understory. This was accomplished by comparing the light niche of juvenile plants in response to the existing light gradient, as well as their physiological plasticity in response to understory light variations. We hypothesized that (1) phylogenetic related species have greater similarity of adaptive strategies, and consequently of their niche, than more distantly related ones; and that (2) the niche breadth is wider and (3) traits plasticity is greater in more recent than in more basal clades. The results presented here showed that there is a greater niche similarity between closely related species than between those that are phylogenetically distant, suggesting niche conservatism. Regarding to niche amplitude, there is also a phylogenetic influence but, contrary to our expectations, the older clades showed a greater niche breadth. For plasticity of selected plant traits, results showed no phylogenetic pattern for the studied species and clades, suggesting that other factors act on the phenotypic plasticity of plants, such as ontogenetic effects and/or environmental stress.
14

Gimnospermas eocretáceas da Formação Crato, bacia do Araripe, Nordeste do Brasil / Early Creatceous gymnosperms from the Crato Formation, Araripe Basin, Northeast Brazil

Paula Andrea Sucerquia Rendon 19 January 2007 (has links)
A Formação Crato, localizada na bacia do Araripe, Nordeste do Brasil, contém um dos registros fossíferos vegetais mais importantes do Cretáceo Inferior. Estes fósseis apresentam excelente estado de preservação, no geral, com pouca fragmentação, órgãos em conexão e estruturas epidérmicas e anatômicas delicadamente substituídas por óxidos de ferro. Como acontecia globalmente, as gimnospermas eram o grupo vegetal dominante na paleoflora eocretácea da Formação Crato, ocorrendo na forma de Bennettitales, Coniferales e Gnetales. As Bennettitales foram um componente aparentemente raro, estando representado pelas espécies Otozamites sp. e Zamites sp. Dentre as Coniferales, encontram-se as famílias Araucariaceae e Cheirolepidiaceae, as Araucariaceae registradas nas espécies Araucarites vulcanoi Duarte e Araucarites kunzmanni sp. nov.; as Cheirolepidiaceae, o grupo mais diverso, estão representadas pelas espécies Brachyphyllum obesum Heer, Brachyphyllum ponsi sp. nov., Brachyphyllum araripense sp. nov., Tomaxellia aff. T. biforme Archangelsky, Toxamellia aff. T. degiustoi e Pseudofrenelopsis sp. As Gnetales ocorrem na forma das espécies Limaephyton cratense gen. et sp. nov., Limaephyton duartei gen. et sp. nov. e Limaephytophyllum mohrium gen. et sp. nov. Características morfológicas, epidérmicas e anatômicas presentes nos macrofitofósseis da Formação Crato, evidenciam adaptações a um ambiente de baixa umidade. Esta flora se desenvolveu dentro da Região Equatorial, numa área intracontinental sob condições climáticas áridas e semi-áridas. / Crato Formation, located in the Araripe Basin, Northeastern Brazil, bears one of the most important Lower Cretaceous fóssil plant Record. The fossils have an excellent preservation, usually low fragmentated, with attached organs and epidermic and anatomic features delicatedly replaced by iron oxides. As it happens worldwide, gymnosperms were the dominant group in the Lower Cretaceous Crato Formation paleoflora, existing as Bennettitales, Coniferales e Gnetales. Bennettitales were an apparently scarce component, represented by the species Otozamites sp. and Zamites sp. Between the Coniferales, are the families Araucariaceae and Cheirolepidiaceae, the Araucariaceae recorded by the species Araucarites vulcanoi Duarte and Araucarites kunzmanni sp. nov.; Cheirolepidiaceae, the most diverse group, is registered by species Brachyphyllum obesum Heer, Brachyphyllum ponsi sp. nov., Brachyphyllum araripense sp. nov., Tomaxellia aff. T. biforme Archangelsky, Toxamellia aff. T. degiustoi e Pseudofrenelopsis sp. As Gnetales are documented by the species Limaephyton duartei gen. et sp. nov. and Limaephytophyllum mohrium gen. et sp. nov. Morphologic, epidermic and anatomic features founded in the plant fossils from Crato Formation, evidence low moisture environment adaptations. That flora was developed in the Equatorial Region, in an intracontinental area with arid to semi-arid climatic conditions.
15

A biosystematic survey of Sierra Lodgepole pine (Pinus contorta var. murrayana [Critchfield]) populations in the transverse and peninsular ranges of Southern California

Everett, Richard Gobin 01 January 1997 (has links)
No description available.
16

The Phylogeny of Land Plants: A Cladistic Analysis Based on Male Gametogenesis

Garbary, David J., Renzaglia, Karen S., Duckett, Jeffrey G. 01 September 1993 (has links)
A cladistic analysis was carried out to resolve phylogenetic pattern among bryophytes and other land plants. The analysis used 22 taxa of land plants and 90 characters relating to male gametogenesis. Coleochaete or Chara/Nitella were the outgroups in various analyses using HENNIG86, PAUP, and MacClade, and the land plant phylogeny was unchanged regardless of outgroup utilized. The most parsimonious cladograms from HENNIG86 (7 trees) have treelengths of 243 (C.I. = 0.58, R.I. = 0.82). Bryophytes are monophyletic as are hornworts, liverworts, and mosses, with hornworts identified as the sister group of a liverwort/moss assemblage. In vascular plants, lycophytes are polyphyletic and Selaginella is close to the bryophytes. Lycopodium is the sister group of the remaining vascular plants (minus Selaginella). Longer treelengths (over 250) are required to produce tree topologies in which either lycophytes are monophyletic or to reconstruct the paraphyletic bryophyte phylogeny of recent authors. This analysis challenges existing concepts of bryophyte phylogeny based on more classical data and interpretations, and provides new insight into land plant evolution.
17

Programmed cell death and genetic stability in conifer embryogenesis /

Helmersson, Andreas, January 2007 (has links) (PDF)
Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 5 uppsatser.
18

Prospecção, mapeamento e caracterização de depósitos fitofossilíferos da porção nordeste da bacia sedimentar do Paraíba (formação pedra de fogo, permiano)

CONCEIÇÃO, Domingas Maria da 19 February 2016 (has links)
Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-09-02T15:10:01Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação final.pdf: 8181941 bytes, checksum: 644c77808b1a817d56598a81727f0da5 (MD5) / Made available in DSpace on 2016-09-02T15:10:01Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação final.pdf: 8181941 bytes, checksum: 644c77808b1a817d56598a81727f0da5 (MD5) Previous issue date: 2016-02-19 / CAPEs / Os afloramentos fitofossilíferos da margem nordeste da Bacia Sedimentar do Parnaíba, em estratos do Permiano (Cisuraliano) da Formação Pedra de Fogo, ainda estão pouco estudados. Este trabalho visou o reconhecimento e análise de alguns dos afloramentos da margem supracitada, tendo se concentrado no estudo de áreas nos municípios de Altos, no Piauí, e de Duque Bacelar e Coelho Neto, no Maranhão. Em Altos, detectou-se em um único afloramento, uma associação autóctone?/parautóctone, dominada por grandes lenhos gimnospérmicos (com até 1,80 m de diâmetro). A área de Duque Bacelar e Coelho Neto apresentou mais de cinco afloramentos contendo associações formadas, especialmente, por lenhos gimnospérmicos de grande porte (de até 1,15 m de diâmetro), alguns em posição de vida, e, secundariamente, por caules de pteridófitas horizontalizados, e.g. Psaronius sp. (com até 5 m de comprimento). Análises espectroscópicas em amostras de fósseis do Maranhão apresentaram um elevado nível de sílica e a permanência residual de carbono amorfo, evidenciando nestes troncos um processo de permineralização por sílica. Foram confeccionadas lâminas petrográficas de troncos fósseis com o intuito de verificar o grau de preservação de tecidos e determinar o seu potencial para futuras análises taxonômicas. Finalmente, foi possível corroborar que as associações encontram-se inseridas em rochas lacustres da base da Formação Pedra de Fogo (Membro Sílex Basal), próximas ao contato com a infrajacente Formação Piauí (Carbonífero, Pensilvaniano). Esta observação contrasta com estudos anteriores, realizados na margem sudoeste da bacia, que referem o posicionamento dos fitofósseis na parte superior da Formação Pedra de Fogo (Membro Trisidela) ou, ainda, na sobrejacente Formação Motuca. / Petrified plant-bearing outcrops of lower Permian (Cisuralian) strata of the Pedra de Fogo Formation located in the northeastern margin of the Parnaíba Sedimentary Basin, are still poorly studied, and dominated mostly by gymnosperm trunks and, rarely, pteridophyte stems (Psaronius sp.). This work aimed prospection and analysis of some of the outcrops in the aforementioned margin of the basin, being focused on two new areas in the municipalities of Altos, Piauí state, and Duque Bacelar-Coelho Neto, Maranhão state. In Altos, an autochthonous?/parautochthonous assemblage dominated by huge gymnosperm trunks (reaching 1,8 m in diameter) was recorded in a single outcrop. The Duque Bacelar-Coelho Neto area evinced more than five exposures formed mostly by large gymnosperm trunks, some of them in life position (reaching 1,15 in diameter) and, less often, by pteridophyte stems in horizontal position, e.g. Psaronius sp. (reaching 5 m long). Invertebrate traces and stromatolites are exposed here too. Spectroscopic analyses in fossil samples from Maranhão showed a high concentration of silica and the residual presence of amorphous carbon, evincing a process of silica-permineralization. Petrographic thin-sections of fossil trunks were produced in order to verify the degree of tissue preservation and determinate its potential for future taxonomic analyses. Finally, it was possible to assess that these assemblages are placed within lacustrine rocks at the base of the Pedra de Fogo Formation (Sílex Basal Member), close to the contact with the underlying Piauí Formation (Carboniferous, Pennsylvanian). This observation contrasts with former studies made at the southwestern margin of the basin that refer the placement of fossil-plant horizons of the Pedra de Fogo Formation to the uppermost Trisidela Member or even to the overlying Motuca Formation.
19

Eocene-Miocene Carbon-Isotope and Floral Record From Brown Coal Seams in the Gippsland Basin of Southeast Australia

Holdgate, Guy R., McGowran, Brian, Fromhold, Tom, Wagstaff, Barbara E., Gallagher, Stephen J., Wallace, Malcolm W., Sluiter, Ian R., Whitelaw, Michael 01 January 2009 (has links)
The carbon-isotope and palynological record through 580 m thick almost continuous brown coal in southeast Australia's Gippsland Basin is a relatively comprehensive southern hemisphere Middle Eocene to Middle Miocene record for terrestrial change. The carbon isotope δ13Ccoal values of these coals range from - 27.7‰ to - 23.2. This isotopic variability follows gymnosperm/angiosperm fluctuations, where higher ratios coincide with heavier δ13C values. There is also long-term variability in carbon isotopes through time. From the Eocene greenhouse world of high gymnosperm-heavier δ13Ccoal values, there is a progressive shift to lighter δ13Ccoal values that follows the earliest (Oi1?) glacial events around 33 Ma (Early Oligocene). The overlying Oligocene-Early Miocene brown coals have lower gymnosperm abundance, associated with increased %Nothofagus (angiosperm), and lightening of isotopes during Oligocene cooler conditions. The Miocene palynological and carbon-isotope record supports a continuation to the Oligocene trends until around the late Early Miocene (circa 19 Ma) when a warming commenced, followed by an even stronger isotope shift around 16 Ma that peaked in the Middle Miocene when higher gymnosperm abundance and heavier isotopes prevailed. The cycle between the two major warm peaks of Middle Eocene and Middle Miocene was circa 30 Ma long. This change corresponds to a fall in inferred pCO2 levels for the same period. The Gippsland data suggest a link between gymnosperm abundance, long-term plant δ13C composition, climatic change, and atmospheric pCO2. Climatic deterioration in the Late Miocene terminated peat accumulation in the Gippsland Basin and no further significant coals formed in southeast Australia. The poor correspondence between this terrestrial isotope data and the marine isotope record is explained by the dominant control on δ13C by the gymnosperm/angiosperm abundance, although in turn this poor correspondence may reflect palaeoclimate control. From the brown coal seam dating, the coal appears to have accumulated during a considerable part of the allocated 30 Ma Cenozoic time period. These brown coal carbon isotope and palynological data appear to record a more gradual atmospheric carbon isotope change compared to the marine record.
20

Résines végétales actuelles et fossiles : origine, caractérisation chimique et évolution / Recent and fossil plant resins : origin, chemical characterization and evolution

Nohra, Youssef A. 14 December 2015 (has links)
Les travaux de cette thèse portent sur la caractérisation chimique des ambres provenant de plusieurs gisements d’âges et d’origines géographiques variés, dont certains sont inédits. Des protocoles identiques à tous les échantillons et combinant les analyses spectroscopiques (IR et RMN 13C) et chromatographiques (THM-CPG-SM) ont été appliqués, permettant d’identifier l’origine botanique des ambres et fournissant des indices pour la reconstitution des paléoenvironnements terrestres. La caractérisation chimique des gisements d’ambre du Jurassique supérieur (Kimméridgien) jusqu’au Crétacé supérieur (Santonien) du Liban, de Jordanie, du Congo, d’Equateur et de France, permet de proposer des biomarqueurs pour les résines de Cheirolepidiaceae, une famille exclusivement mésozoïque de Conifères. Une évolution des sources botaniques des résines produites durant le Mésozoïque et le Cénozoïque est alors discutée. Une production dominée par les familles de Conifères Araucariaceae et Cheirolepidiaceae est remarquée au Jurassique supérieur et Crétacé inférieur. La production au Crétacé supérieur est plutôt dominée par des Cupressaceae. Au Cénozoïque, les origines botaniques des ambres sont plus variées, et des familles d’Angiospermes sont à l’origine de nombreux gisements, dont l’ambre du Pérou produit par une Fabaceae. La production par des Conifères reste toutefois importante au Tertiaire, à l’exemple des ambres de Nouvelle-Zélande qui ont pour origine les Araucariaceae. Les données obtenues ont permis une ré-évaluation de la classification des ambres par Py-GC-MS. Ainsi, une nouvelle molécule dont la structure est inconnue encore, a été identifiée dans les chromatogrammes d’ambres de classe Ib et Ic, ajoutant un caractère discriminant entre ces deux sous-classes. Enfin, la relation âge / maturation des résines fossiles est discutée, qui dépend avant tout des conditions d’enfouissement des résines. Une large base de données moléculaires est ainsi établie pour un grand nombre de gisements d’âges et d’origines botaniques variés, qui permettra une comparaison globale dans les travaux futurs. / This work focuses on the chemical characterisation of amber from different outcrops from different localities, and varied ages. Some of these outcrops had never been studied. All the amber samples were analysed with the same analytical techniques. The combination of the data obtained from spectroscopic (IR and 13C NMR) and chromatographic (THM-GC-MS) analysis allows the identification of the botanical origin of the amber and provide some information, for the reconstruction of the palaeoenvironment. Biomarkers for the cheirolepidiaceous resins were proposed based on the chemical characterisation of different amber outcrops dating from the Upper Jurassic (Kimmeridgian) to the Upper Cretaceous (Santonian) from Lebanon, Jordan, Congo, Ecuador and France. The Cheirolepidiaceae familt was exclusively present in the Mesozoic era. Hence, the evolution of the botanical origins of the produced resins during the Mesozoic and Cenozoic eras was discussed. It seems that Araucariaceae and Cheirolepidiaceae were the dominant resin producing trees during the Upper Jurassic and the Lower Cretaceous. While, cupressaceous resiniferous plants were dominant during the Upper Cretaceous. Howerver, resins dating from the Cenozoic era, were produced by a wider variety of plants, as resiniferous families of Angiosperm intensively participated in the resin production, i.e. the Peruvian amber produced by Fabaceae. Conifer resins traces were also detected in the Tertiary, such as the amber from the Araucariaceae found in New Zealand. The obtained data allowed a re-evaluation of the classification of ambers by Py-GC-MS, leading to the discovery of a novel molecule. This molecule of an unknown structure brings a new discrimination factor between the classes Ib and Ic. Finally, the age / maturity relationship is showed to be dependent on the burial and the conservation conditions of the resins. A broad molecular database is established based a large group of amber outcrops from different ages, and having diverse botanical origins. This database could be used as a comparative platform for further work in the future.

Page generated in 0.078 seconds