Early salt shock uncouples shoot - root acclimation in Lobularia maritima

Salt stress triggers overlapping osmotic and ionic effects. In halophytes, rapid acclimation can obscure how early responses are coordinated across organs. The use of facultative halophytes and salt shocks provides a useful framework to resolve this transition.

We investigated the first 24 h of salt shock responses in the facultative halophyte Lobularia maritima by integrating physiological, ionomic, transcriptional and phytohormonal analyses to resolve organ- and time-dependent acclimation dynamics.

Salt shock induced a rapid but transient osmotic effect, with shoot turgor recovery after 8 h. This recovery was associated with sustained osmotic adjustment, proline accumulation and increased Na ⁺ levels in shoots. Conversely, photosynthetic impairment persisted beyond osmotic recovery. Salt exposure rapidly reshaped shoot and root ionomes and was associated with dynamic expression of LmSOS1 , LmNHX1 , and LmHKT1 , consistent with coordinated Na ⁺ partitioning. Oxidative responses diverged between organs; shoots maintained a stable oxidative state, while roots exhibited progressive loss of meristem viability. Abscisic acid (ABA) was strongly accumulated at all time points and emerged as the dominant regulator of early responses.

These results show that early salt acclimation in L. maritima is rapid but spatially and functionally uncoupled, combining fast shoot osmotic adjustment with persistent photosynthetic constraints and increased root vulnerability.