Résumé
Understanding and controlling the mechanisms that underlie plant responses to drought has become essential for agriculture in the context of global change. Here, we used maize as a model for studying the physiological and genetic bases of root responses to drought. Three major functions shaping root hydraulic architecture were investigated: hydraulics, growth and signaling.Root system architecture (RSA) and root hydraulic conductivity (Lpr) were analysed in plants subjected to water deficit of different intensities as induced by various polyethylene glycol (PEG) concentrations. Detailed studies on primary and seminal roots revealed distinct anatomical, architectural and hydraulic response patterns depending on water deficit intensity and root type. In particular, a functional/structural model of primary or seminal roots was developed and used in an inverse modelling approach to concomitantly determine their axial and radial hydraulic properties, and their dependence on water deficit. A split root system was used to dissect the effects of heterogeneous water availability revealing systemic effects of water deficit on root growth. The significance of these responses with respect to plant acclimation to drought will be discussed. In parallel, a genetic dissection of maize root hydraulics (Lpr) was carried out using Genome Wide Association (GWA) in a diversity panel of 316 dent lines. Associated SNPs and underlying candidate genes are currently under genetic validation using biparental recombinant populations and knock-out mutants obtained by transposon insertion or CRISPR-Cas9. In the future, these contrasting maize genotypes will be used to analyse the impacts of root hydraulic architecture on plant growth under drought.