Interactions entre la rhizodéposition de composés carbonés et la disponibilité en N minéral chez Lolium multiflorum aux stades végétatifs

Abstract : Our work focuses on the interactions between the release of carbon by roots and the nitrogen availability in the rhizosphere. Two main objectives have been established : to characterize the effect of nitrogen on rhizodeposition process and to evaluate the impact of rhizodeposition on the nitrogen internai cycle including the study of microbial communities. We worked on a meadow grass: Lolium multiflorum, grown in hydroponics or in non sterile soil. Rhizodeposition has been evaluated by direct measurements, by the labelling of photo-assimilates by 14C and by the use of a biosensor reporting on the carbon availability. Microbial biomass has been characterised through its size, its activity and the structures of its community. The internai cycle of nitrogen, was studied by the determination of the argininase activity, the balance sheet of nitrogen transformations and by evaluating the limiting factor of bacterial growth. Our results indicate, in hydroponics, that nitrogen increased the quantity of carbon released from roots. This has been modelled by the number of root branches and the root soluble carbon concentration. ln soils results are less marked due to the high concentrations of nitrogen in our control soils. ln the rhizosphere, compared to the non adhering soil, bacterial activity and density have been increased. Communities structure has not been modified. We have shown, that in the rhizosphere, argininase activity was increased suggesting an increase of gross mineralisation. Moreover, balance sheet of the nitrogen transformations was in favour of a decrease of nitrogen mineralisation in the soil sam pies in the vicinity of roots. The relationships between rhizodeposits and nitrogen dynamics in the the rhizosphere are discussed.
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Theses
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http://docnum.univ-lorraine.fr/prive/INPL_T_2004_HENRY_F.pdf
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Submitted on : Thursday, March 29, 2018 - 12:36:16 PM
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Frédéric Henry. Interactions entre la rhizodéposition de composés carbonés et la disponibilité en N minéral chez Lolium multiflorum aux stades végétatifs. Sciences agricoles. Institut National Polytechnique de Lorraine, 2004. Français. ⟨NNT : 2004INPL018N⟩. ⟨tel-01750030⟩

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