Résumé
To gain insights into the natural variation of root hydraulics and its molecular components, genotypic differences in root water transport and PIP aquaporin expression were investigated in 13 natural accessions of Arabidopsis. A 2-fold variation of root hydraulic conductivity (Lpr) and variable contribution of cell-to-cell and apoplastic water transport paths among accessions were revealed. Principle component analysis (PCA) showed a positive overall correlation between Lpr and certain highly expressed PIP transcripts. Root hydraulic responses to salt stress were characterized in a subset of five accessions (Blh-1, Ct-1, Col-0, Di-M, and Mr-0). Lpr was down-regulated in all accessions except Mr-0. In Mr-0 and Ct-1, cortical cell hydraulic conductivity was unresponsive to salt, whereas it was down-regulated in the three other accessions. The overall work provides clues on how hydraulic regulation allows plant adaptation to salt stress. It also shows that a wide range of root hydraulic profiles, as previously reported in various species, can be observed in a single model species. This work paves the way for a quantitative genetics analysis of root hydraulics.