Spatial and developmental reprogramming enables root growth under high salinity in the extremophyte Schrenkiella parvula

High salinity severely restricts root growth in most plants, yet the extremophyte model Schrenkiella parvula maintains growth under otherwise inhibitory conditions through a previously unrecognized developmental reorganization of the primary root. Under high salinity, the elongation zone rapidly reorganizes into two distinct states: the bulged and gap zones. These zones form in response to ionic stress and emerge during a transient growth pause followed by resumed tip growth and localized lateral root emergence from the gap zone. Jasmonic acid (JA) is necessary to initiate this developmental transition, while cell-layer-resolved hormone profiling revealed spatiotemporally coordinated JA and auxin accompanying the maintenance of the distinct zones. The zone-specific expression profiling resolved transcriptomic networks spanning core development and broad or zone-specific stress responses, revealing spatial regulation of hormone signaling, cell-wall remodeling, and osmotic and oxidative stress pathways. Raman spectroscopy, metabolite profiling, and cellular imaging supported localized regulation of water availability, ionic balance, and suppression of ROS accumulation and cell death. These networks also identified orthologous genes co-opted for novel functions potentially used to sustain growth. Together, these findings reveal a spatially coordinated mechanism for maintaining root growth under salt stress and provide a framework for discovering genetic mechanisms that optimize growth under stress.