Eco-Innovative Biostimulant Derived From Olive Mill Solid Wastes Enhances Agro-Physiological Performance And...

Nanotechnology is increasingly recognized in research, industrial, and agricultural sectors for its ability to generate bio-based nanomaterials that support sustainable production systems. In parallel, the mismanagement of olive mill wastes (OMWs) poses a persistent environmental challenge, despite their richness in bioactive compounds of agronomic interest. Recent studies have underscored the potential of OMW valorization as a source of eco-friendly bioactive agents. In this context, this study developed a hybrid nanobiostimulant (B) consisting of lignin nanoparticles (LNPs) loaded with phenolic extract (LNPs + PE) derived from olive mill solid wastes (OMSWs) and evaluated its effectiveness in alleviating drought stress in pomegranate (Punica granatum L.). The formulation (250 ppm) was tested under three irrigation regimes: control (C, 100% field capacity), drought-stressed (S, 50% field capacity), and drought-stressed plants treated with the nanobiostimulant (S + B). Application of LNPs + PE under water deficit significantly improved shoot elongation, leaf area (LA), and relative water content (RWC). Physiological and biochemical responses showed enhanced chlorophyll fluorescence, increased pigment and flavonoid accumulation, and notable reductions in malondialdehyde (MDA) and soluble sugars, indicating improved drought tolerance. Overall, this work demonstrates that OMSW can be transformed into value-added nanobiostimulants capable of strengthening plant performance under limited water availability, offering a practical approach to waste valorization and sustainable agriculture.