Copper-based materials mitigate salinity stress in hydroponically grown lettuce (Lactuca sativa L.)

As water scarcity persists, alternative irrigation methods, such as water reuse in agriculture, will be adopted, though often limited by high salinity levels. Hence, the potential of copper to mitigate salinity stress in lettuce (Lactuca sativa L.) was evaluated. Plants were grown hydroponically and exposed to moderate (100 mM) or elevated (150 mM) salinity (as NaCl), either alone or in combination with foliar applied copper-based materials, including copper oxide nanoparticles (nCuO), bulk copper oxide (bCuO), copper sulfide nanoparticles (nCuS), or copper sulfate (CuSO₄). Under moderate salinity, the Cu-based materials were applied at 25 and 100 mg L^-1, while for high salinity, only the 25 mg L^-1 Cu treatment was used. Foliar application of 25 mg L^-1 nCuO, nCuS, or CuSO₄ effectively mitigated salinity-induced growth inhibition under both salinity conditions. Additionally, 25 mg L^-1 nCuS significantly increased the chlorophyll content of salt-affected plants by 305% (p < 0.005) and 92.9% (p < 0.001) under moderate and elevated salinity conditions, respectively, compared to untreated salinity controls. In addition, shoot phosphorus and potassium uptake were significantly increased by 25 mg L^-1 nCuO compared to the moderate salt-stressed controls (p < 0.05). Furthermore, moderate salinity induced oxidative stress and lipid peroxidation, as indicated by a 52% increase in malondialdehyde (MDA) content. One hundred mg L^-1 nCuO and nCuS significantly decreased MDA by 45% and 38% (p < 0.05), respectively. This study demonstrates a concentration- and Cu-type-dependent role of Cu in reducing the adverse effects of salinity stress in lettuce plants under hydroponic conditions. The consistency of the findings under both moderate and elevated salinity conditions highlights the robustness of Cu-based treatments in mitigating salt stress in lettuce.

The online version contains supplementary material available at 10.1186/s44331-025-00006-2.