Mitigating salt stress in maize using Ecklonia maxima seaweed extracts

• Salinity stress of maize decreased dry root weight, photosynthesis and membrane integrity. • Stress-associated metabolites increased in salt stressed maize. • Foliar application of Ekclonia maxima -derived biostimulant mitigated salt stress impact. • Improved morphology and photosynthesis of biostimulant treated maize under salinity stress. • Metabolic reprogramming of metabolites associated with salt stress alleviation and adaptation. Salinity stress poses a significant threat to crop productivity, making it crucial to explore strategies that alleviate its adverse effects. This study investigated the impact of Afrikelp®, a commercial seaweed extract (SE) biostimulant, derived from Ecklonia maxima on maize ( Zea mays L.) plants subjected to salinity stress. Gas exchange analysis revealed that plants treated with SE Afrikelp® exhibited significantly higher photosynthetic rates under control conditions (45 % respectively) and 200 mM salt stress (95 % respectively) compared to untreated plants. Similarly, plants treated with SE Afrikelp® and 200 mM salt stress had significantly higher internal CO 2 concentrations and transpiration rates compared to untreated salt stressed plants. Morphological analysis demonstrated that SE Afrikelp® enhanced plant growth and reduced electrolyte leakage under both control and salinity stress conditions. Metabolomic profiling revealed significant alterations in primary metabolites, particularly amino acids, sugars, and organic acids. As such, the results reveal that SE Afrikelp® induced a metabolic reprogramming towards stress alleviation and enhanced defences. Overall, SE Afrikelp® demonstrated potential in mitigating the adverse effects of salinity stress on maize plants, warranting its efficacy for agricultural applications.