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Séminaire de Suryendu Dutta (géochimiste organicien à l’Indian Institute of Technology à Bombay)

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Séminaire de Suryendu Dutta, géochimiste organicien à l’Indian Institute of Technology à Bombay au LOG au SN5

Date : 27 juin 2018 à 13h30

Lieu : Bâtiment SN5 Salle 27/28

Résumé :

Plants are master chemists. They synthesize a wide range of natural products that have fundamental physiological and ecological processes. Based on their biosynthetic origins these natural products can be divided into three major groups : the terpenoids, the alkaloids and the phenylpropanoids. The terpenoids are synthesized by plants where they serve as primary metabolites involved in growth and developments or as secondary metabolites that play an important role in the interaction of the plant with its biotic environments. The last two decades, have seen considerable progress in elucidating plant terpenoid biosynthetic pathways at the gene and enzyme levels. However, the geological evolution of these natural products remains poorly understood.
Palaeogegraphic model suggests that the Indian plate was separated from Gondwana during Late Jurassic and started moving towards the northern hemisphere during the Early Cretaceous and remained as an island continent during the entire Cretaceous until it collided with Asia in Early Eocene at ca. 50 Ma.
A brief outline on evolution of plant terpenoids from Permian to Eocene on the Indian continent will be discussed during the presentation. The Permian coals are characterized by tricyclic and teracyclic diterpenoids. The possible source of these compounds is primitive conifers.
The molecular composition of Jurassic and early Cretaceous sediments suggests that the vegetation was contributed by conifers (e.g. Arucariaceace, Podocarpaceae) during the period. A remarkable shift of floral association from Cretaceous to early Palaeogene period in western India is observed in the biomarker assemblages. Drastic reduction of coniferous vegetation and proliferation of angiosperms in early Palaeogene are observed in the present study. The terpenoid signatures of early Palaeogene lignites suggest that the western India was covered by widespread thick closed rain forests thriving under the influence of tropical climate. Biomarker signature of mangroves is also observed in early Palaeogene sediments. The importance of monoterpenoids and sesquiterpenoids in palaeoecology will also be discussed.