Water deficit caused by osmotic stresses to roots, including salinity and drought, presents a significant environmental challenge to plant growth and crop yield. In seconds to hours, it results in diverse responses in plants, including impairment of cell wall integrity, decline in turgor potential, generation and signaling of abscisic acid, as well as reprogramming of gene expression. These processes have been studied extensively but, so far, there is no clear picture of when and where the physical nature of a water deficit is perceived by plants and turned into a biological signal. In a work published in 2023, a combination of physiology and transcriptomic approaches allowed us to unravel that both turgor pressure changes in root cortical cells and external osmotic potential are able to trigger specific transcriptional regulations. We identified genes whose mRNA abundance in roots was quantitatively correlated to one or the other of the components of water potential. We recently focused our efforts on two of those candidates, and unravel that plasmolysis is a turning point in their dynamic of response to osmotic stress. Both promoter activity and mRNA decay pathways are required for their proper regulation. Finally, we created a luciferase-based, genetically encoded, construct that is able to report early hydraulic changes. This “hydro-reporter” is ABA-responsive but its regulation by water deficit is ABA- independent and, although initially designed in roots, can also be observed in shoots.