Natural biostimulant formulations enriched with honey, iodine, and silymarin enhance drought tolerance and yield in faba bean (Vicia Faba L.) through antioxidant and hormonal regulation

Drought stress is a major limitation to legume productivity in arid and semi-arid regions. This study investigated the effectiveness of two novel natural biostimulant formulations (NBFs), composed of bee honey, potassium iodate, and silymarin selected for their complementary antioxidant and osmoprotective functions in enhancing drought tolerance in faba bean (Vicia faba L.). Plants were subjected to deficit irrigation (withholding one irrigation after every two cycles) and foliar-sprayed with NBFs containing either 7.5 g L⁻¹ (F1) or 15 g L⁻¹ (F2) bee honey combined with 25 mg L⁻¹ potassium iodate and 0.2 mg L⁻¹ silymarin. Deficit irrigation markedly reduced growth, photosynthetic pigments, water status, and yield, while elevating oxidative stress markers. Application of NBFs significantly alleviated these adverse effects by enhancing osmolyte accumulation, improving antioxidant defenses, and restoring photosynthetic efficiency. Hormonal regulation was also improved, with increases in auxin, gibberellins, and cytokinins, alongside reduced abscisic acid levels. Notably, F2 was more effective than F1 in maintaining leaf integrity and maximizing pod yield under drought. These results highlight the potential of honey-iodine-silymarin formulations as eco-friendly, cost-effective biostimulants to promote crop resilience and productivity under water-limited conditions, contributing to sustainable agriculture.