ECOPHYSIOLOGIE DES LEGUMINEUSES (EcoLeg)

Coordinator : Marion PRUDENT

Thanks to their ability to fix atmospheric nitrogen, legumes are a biological nitrogen source for cropping systems. However, they currently represent only a small part of cultural systems, since the use of chemical fertiliser, associated with agricultural intensification, has replaced their biological fertilising function. Legumes now have a key role to play in the transition of agriculture towards cultural systems based on an agroecological management of resources.

The limited abundance of legumes in our agrosystems is partly related to their high sensitivity to abiotic stresses, the intensity and frequency of which are amplified by current changes in climate.

In this context, the finalised objective of the team is to contribute to the development of annual legume ideotypes (e.g. pea, faba bean, soy bean, lentil) that provide ecosystem services, support interactions with soil microorganisms, and are adapted to future climate.

Our research is based on an ecophysiological analytical framework that characterises the responses of legumes to selected biotic and abiotic parameters, with a structure-function approach that integrates the inputs and fluxes of nitrogen, carbon and water at the whole-plant scale. This framework, associated with other scientific disciplines (namely transcriptomics, metabolomics and microbial ecology), takes into account intra- and inter-specific genetic variability by establishing interactions with the geneticists and molecular physiologists of the GEAPSI department as well as the microbial ecologists and soil scientists of the BIOME department.

Our approach is applied to 4 main research themes:

• The study of the response of plants and stands to abiotic stresses, whether single, repeated or combined, during the early part of the plant development cycle (e.g. winter temperature, water stress) or its late part (e.g. high temperature, water stress).
• Characterising the onset of trophic interactions (including the study of rhizodeposition) between legumes and soil microbial communities (including the symbiont) and their impact on plant nutrition and water status.
• The analysis of the tolerance and resilience of the nitrogen status of legumes to water stress, in interaction with soil microbial communities.
• The study of the impacts of precipitation regimes on the interactions between the plant and soil microbial communities (including bacteria and fungi), and their consequences on soil biogeochemical carbon and nitrogen cycles.

This analytical research and their integration in models allow us to identify legume traits that determine adaptation characteristics to global change or provide services such as:

• Characteristics of adaptation to climate change in pea stands are identified through the development and use of the culture model AZODYN-PEA, in collaboration with climate scientists that run models of future climate.
• Characteristics enhancing positive interactions between legumes and soil microbial communities (whether symbiotic or not), for improved water and mineral plant nutrition.
• Characteristics involved in production of nitrogen-related ecosystem services, through the quantification of nitrogen fluxes in the field for a range of legume species (during growth, between crops and in the crop following legumes).

Our research is supported by methodological developments. Specifically, our analytical work is integrated in models that represent the functioning of legumes either at the plant scale, using the PEAD-NOD root architectural model (coll. UR PSH), or at the stand scale, using the crop model AZODYN-PEA (coll. UMR Agronomie). Ecophysiological measurements take advantage of a specific experimental setup within the 4PMI high-throughput phenotyping platform, in which we develop rhizotron growth systems as well as associated image analysis methods.