Post-stress recovery from drought and salinity in olive plants is an active process associated to physiological and metabolic changes

The present work aims to explore a poorly understood behavior of how olive plants coordinate their physiological functions and metabolic adjustments after a prolonged recovery period following water deficit and salt stress. Here, water stress and salinity were imposed for 21 days, followed by a recovery period for 60 days. Both stressors induced reduction in physiological performance of olive plants, leading to oxidative damage, with a more pronounced effects under saline conditions. After stress release, despite the restoration of the physiological and the cellular redox state in both treated plants, their metabolic profiles do not return to the control level. Indeed, our data showed a considerable induction, lasting after two months of recovery, of potent signal molecules and antioxidants like H₂O₂, proline, phenols (showing an intermediate behavior between plants recovering from salinity or drought) and Car, SOD and CAT (displaying higher expression in salt-recovered plants), putatively as a preventive protection response. Additionally, by reducing the chlorophyll amount and the level of fatty acids without impacting the UFAs, DBI and PSII efficiency, recovered olive plants tend to adjust its chloroplast and membrane structures to a new state of reorganization to prevent future membrane damage. Nonetheless, these extensive modulations appeared to occur at the expense of regrowth, particularly in salt-recovered plants. Overall, olive recovering from water deficit or salinity, with little differences in retaining the stress’s imprint, may drive their metabolism to develop an acclimation process, possibly as a sign of beneficial adaption to adapt to repeated stress episodes.