[Impacts of climate change on the functioning and productivity of agroecosystems: a focus on the impact of interactions between CO2, temperature and water deficit].

Rising atmospheric CO2 concentrations and temperatures, as well as changes in water regimes, are major determinants of the functioning and productivity of agroecosystems. Although the individual effects of each of these factors have been extensively studied, their combined action remains poorly understood, despite the fact that these factors interact closely to shape future climate conditions. This article provides a synthesis of current knowledge on the combined impacts of rising CO2, temperatures and water deficiency on crop plants, with a particular focus on wheat. Following a review of the experimental setups used to study these interactions, we analyse the ecophysiological and agronomic responses of plants to different combinations of climatic factors, distinguishing between specific effects, interactions and compensatory mechanisms. Results from recent syntheses and meta-analyses highlight a high degree of variability in responses, depending on species, genotypes, phenological stages and experimental conditions. Experimental results, across all experimental setups, show in particular that the fertilising effect of CO2 does not generally compensate for the negative impacts of water and heat stress, particularly when these are combined. Finally, this article discusses the implications of these results for crop modelling and the prediction of agroecosystem productivity trajectories in a climate change context, emphasising the need to explicitly integrate interactions between climatic factors, biological processes and genetic variability.