Analysis of gaseous assessments of a root system by ¹⁸O₂ and ¹⁵N₂. Application to the direct measurement of nitrogen fixation

This academic engineering study addresses the use of the measurement of nitrogen symbiotic fixation by using the ¹⁵O₂ isotope. This method is non destructive and allows the simultaneous measurement of fixation and of other important vegetal metabolisms (photosynthesis, photo-respiration, foliar and root respiration). After a bibliographical synthesis on nitrogen fixation, the author presents equipment and methods: mini-cells in a chamber of automatic cultivation under artificial atmosphere, regulations, data acquisition and exploitation. He briefly presents the mass spectrometer and isotopic measurements, reports various performed calibrations, and the measurement of root respiration. Experimental results are then presented and discussed: experiments on non-nodulated beans and on nodulated beans.