Couvreur, ValentinDing, LeiStoquart, ThéoThéoStoquart2025-06-302025-06-302025-06-0920252025-06-10https://hdl.handle.net/2078.2/43248Soil salinization presents a major threat to agricultural productivity worldwide, necessitating the development of salt-tolerant crop varieties. This thesis investigates the hydraulic and physiological mechanisms underlying salinity tolerance in tomato (Solanum lycopersicum cv. 'Moneymaker') and its wild relative S. pimpinellifolium, within the framework of the Plant Water Pump Project, which questions the classical paradigm of passive water transport in plants. By exploring plant responses to osmotic stress, this work contributes to the broader understanding of active regulatory processes in plant water movement. Plants were grown hydroponically under controlled phytotron conditions and exposed to a three-stage protocol: growth, a gradual salt stress phase (up to 120 mM NaCl), and a post-stress recovery period. A multi-parametric approach was employed, combining continuous non-destructive measurements—such as transpiration (via precision balances) and leaf water potential (via psychrometers and pressure chambers)—with destructive assessments of hydraulic conductance (via High-Pressure Flow Meter), proline accumulation, anatomical traits (leaf area and root surface), and biomass production. The results demonstrate a clear contrast in stress response strategies. S. lycopersicum exhibited a steep decline in transpiration under salt stress, followed by partial recovery. It showed substantial proline accumulation, indicative of active osmotic adjustment, but also sustained reductions in leaf water potential, water content, and root hydraulic conductance. In contrast, S. pimpinellifolium maintained more stable water use, showed higher root conductance under stress, and exhibited only mild reductions in water potential. Its resilience is further evidenced by its ability to preserve root structure and leaf area, a higher basal level of proline even before stress onset, and a more efficient recovery of hydraulic and growth functions. Statistical analysis, including linear mixed models and ANOVA, confirmed the significance of condition–phase interactions across multiple physiological traits, with S. pimpinellifolium demonstrating a slower but more robust and plastic adaptation. These species-specific responses are consistent with ecological origin: S. pimpinellifolium is native to saline and arid coastal environments, while S. lycopersicum has undergone domestication bottlenecks that have reduced its tolerance range.S.pimpenillifoliumS.lycopersicumSalt stressPlant water relationstext::thesis::master thesis