Drought priming alleviated salinity stress and improved water use efficiency of wheat plants

Global warming and salinization are inducing adverse effects on crop yield. Drought priming has been proved to improve drought tolerance of plants at later growth stages, however, whether and how drought priming at early growth stage alleviating salinity stress at later growth stage and improving water use efficiency (WUE) of plants remains unknown. Therefore, two wheat cultivars were subjected to drought priming at the 4th and 6th leaf stage and subsequent moderate salinity stress at 100 mmol NaCl applied at the later jointing growth stage. The growth, physiological responses, ABA signaling and WUE were investigated to unravel the regulating mechanisms of drought priming on subsequent salinity stress. The results showed that drought priming imposed at the early growth stage improved the leaf and root water potential while attenuated the ABA concentration in the leaves ([ABA]leaf) for the primed plants, which increased the stomatal conductance (gs) and photosynthesis (Pn). Consequently, the biomass under the salinity stress was significantly increased due to earlier drought priming. Moreover, drought priming improved the specific leaf N content due to the facilitated root growth and morphology, and this could benefit high leaf photosynthetic capacity during the salinity stress period, improving the Pn and water uptake for the primed plants. Drought priming significantly improved plant level WUE (WUEp) due to considerably enhanced dry biomass compared with non-primed plants under subsequent salinity stress. The significantly increased leaf δ13C under drought priming further demonstrated that the improved leaf δ13C and WUEp was mainly ascribed to the improvement of Pn. Drought primed plants significantly improved K+ concentration and maintained the K+/Na+ ratio compared with non-primed plants under subsequent salinity stress, which could mitigate the adverse effects of excess Na+ and minimize salt-induced ionic toxicity by improving salt tolerance for primed plants. Therefore, drought priming at early growth stage could be considered as a promising strategy for salt-prone areas to optimize agricultural sustainability and food security under changing climatic conditions.