Research line 3 focuses on crop ecophysiology to (1) quantify the impacts of biotic and abiotic stresses, (2) identify the adaptive strategies of a plant stand under constraints and (3) contribute to the development and evaluation of innovative management practices.

We study genetically pure or mixed cultivated annual species (wheat, rapeseed). The preferred integration levels are the plant and the cultivated stand, and we start developing approaches that facilitate the change of scale toward the landscape in relation to RL1. The constraints considered are mainly nitrogen nutrition, leaf pathogenic fungi (rust, septoria) and atmospheric contaminants (ozone), as single factors or in interaction. Our work goes back and forth between the understanding of the processes involved and their integration at the stand level, with two main foci:

• Biological processes of plants under stress and its genetic variability. These researches aimed to produce knowledge on the processes by which the biotic and abiotic environment impacts the structural and functional characteristics of plants and stands, and in return how the functioning of plants impacts their environment, such as the growth of pathogens or the emission in the atmosphere of nitrogen or volatile organic compounds. An originality of our works was the importance given to the architecture of plant and stands, which plays a major role on microclimate and transfer. During the last term period, we showed that; the plasticity of plant architecture response to floral damage was genetically variable (Pinet et al., 2015) and; nitrogen stress, plants states and climate modified the development of foliar pathogenic fungi (Bancal et al., 2016; Robert et al., 2018); inter-plant heterogeneity within a canopy could be modelled with a limited number of parameters (Baey et al., 2018); the mechanisms of defense and adaptation of cells to oxidative stress involved glutathione disulfide with mechanisms yet to be elucidated (Rahantaniaina et al., 2017).
• Modeling the environmental response of whole stand including plants interactions. The practical outcomes are to identify levers and produce indicators for optimizing crop management, and selection. These works concern genetically homogeneous or heterogeneous stands such as associations of species or varieties. The targeted variables concern crop production, but also environmental impact such as fluxes of spore and GHG out of plots. Interactions and feedbacks between system components are explicit in simulation models. Besides we also use top-down approaches, based on the analysis of the relationships between variables measured within the system. During the last term period, we implemented novel schemes that integrate the C and N metabolisms processes in plant models (Barillot et al., 2006ab); we analyzed the genetic variability of nitrogen utilization efficiency under nitrogen stress (RAPSODYN project, V. Vazquez-Carrasquer PhD) ; we showed that worms were necessary to improve organic nitrogen nutrition efficiency (J. Barthod PhD, 2017); we implemented generic 3D plant-pathogen models (Garin et al., 2014) which showed that septoria greatly affected brown rust development (Garin et al., 2018) and was strongly limited by early senescence (Robert et al., 2018); we further developed a new, ecological, consumer-resource model for wheat pathogens which showed that pathogen production increased with fertilization (Précigout et al., 2017); We also contributed to the identification of varieties, either escaping (ECHAP project) or tolerant (Bancal et al., 2015; Collin et al., 2018) to aerial fungal diseases; finally we developed conceptual models of oxidative stress at the cellular level (Tuzet et al., 2018).