Introduction: Salinity is a major environmental issue that negatively impacts agricultural productivity and food security. A promising strategy for mitigating salt stress is the use of biostimulants that enhance plant tolerance to this abiotic stress. Grape pomace, an abundant agro-industrial byproduct, contains bioactive compounds that can be utilized as biostimulants.

Methods: This study examines the impact of grape pomace extract on the germination of tomato (Solanum lycopersicum) and cucumber (Cucumis sativus) seeds under both normal and salt stress conditions. Various concentrations of the extract were evaluated to determine their effects on key germination parameters, including germination percentage, Timson's germination index, germination uniformity coefficient, mean germination time, coefficient of velocity of germination, relative seed germination, relative root growth, and the overall germination index.

Results: Characterization of the grape pomace extract revealed a high content of bioactive secondary metabolites. At low concentrations, the extract significantly improved all germination parameters in both tomato and cucumber under normal and salt stress conditions, indicating a pronounced biostimulant effect across both species. However, higher concentrations exhibited phytotoxic effects, negatively impacting seed germination.

Conclusion: These findings highlight the potential of grape pomace extract as an eco-friendly biostimulant when applied at the optimal concentrations.