Loading…
AD

Anne de la Porte

Institut national de la Recherche Scientifique
Tracking nodule-generated H2 and its impacts on microbial community functioning in the rhizosphere of legume plants

Anne de la Porte, Étienne Yergeau, Philippe Constant

Legume plants are involved in a mutualistic relationship with soilborne bacteria, known as rhizobia, fixing atmospheric nitrogen (N2) in legumes’ symbiotic organs, nodules. Legumes that host rhizobia lacking the hydrogenase uptake system release hydrogen (H2) from their nodules as a by-product of N2 fixation. H2 is an energetic compound that is readily consumed by soil H2-oxidising microbes, thus potentially impacting rhizospheric community functioning. For instance, it has been shown that H2 displays a soil fertilisation effect, but the underlying processes remain unknown. Our aim is to test the hypothesis that H2 fertilisation effect is driven by changes in microbial-mediated processes related to nutrient turnover. Our objectives are (1) to record H2 diffusion from nodules in the rhizosphere and its concentration gradients, as measured by gas chromatography, and (2) identify key microbial guilds whose biodiversity and activity is impaired by changes in H2 concentrations. For the purpose of these experiments, we developed an innovative rhizotron system designed to collect gas samples in soil and examine spatial correlations between H2 gradients and changes in microbial functions. Here, we present performance of rhizotron system to monitor trace gas diffusion and microbial turnover in soil. Case studies including soil alone, soil exposed to H2 originating from artificial or legume plants are presented. Taken together, the results demonstrate that non-destructive and non-disturbing gas sampling in the rhizotron system permits temporal studies mimicking in situ conditions to study the impact of gas emission from plants on soil microbial community diversity and functioning.