Maize root hydraulic architecture and its response to water deficit

International audience

English. Water availability is the most limiting factor affecting plant growth and crop productivity worldwide. Understanding and controlling the mechanisms that underlie plant responses to drought has become essential for agriculture especially in the context of global change. Considered as a water-saving plant due to its C4 metabolism, maize is a suitable model for studying the physiological and genetic bases of cereal responses to drought. Here, we investigated maize root responses to water deficit and focused on three major aspects: hydraulics, growth, and signaling. These three functions shape root hydraulic architecture. We adapted a pressure chamber device to measure root hydraulic conductivity (Lpr) of hydroponically grown maize seedlings, using a whole embryonic root system or individual primary or seminal roots. Root system architecture (RSA) and Lprwere analysed in plants subjected to water deficit induced by various polyethylene glycol (PEG) concentrations. Moderate water stress (50 g/L PEG; ᴪ = -0.070 MPa) had no effect on RSA but slightly inhibited Lpr. In contrast, a higher water deficit (150 g/L PEG; ᴪ = -0.332 MPa) had inhibitory effects on root growth, lateral root formation and Lpr. Slight quantitative differences in both architectural and hydraulic responses to water deficit were observed between primary and seminal roots. In parallel, a genetic dissection of maize root hydraulics (Lpr) was initiated using Genome Wide Association Studies in a panel of 316 Dent lines. Associated SNPs and underlying candidate genes are currently under study. In the future, improved water transport measurements and root image analyses will be coupled to mathematical modelling to represent effects of water deficit on root hydraulic architecture of contrasting maize genotypes.