Phytotoxic effects of olive mill waste on primary metabolism and morpho-physiological parameters of broad bean (Vicia faba L.)

Abstract

Olive mill waste (OMW) presents a complex environmental challenge due to its high phenolic content and acidity, yet its precise impact on integrated plant metabolic networks remains poorly understood. This study investigates the physiological and biochemical plasticity of broad bean (Vicia faba L.) in response to increasing concentrations (0% to 15%) of olive pomace filtrate (OPF). While high OPF levels (> 5%) induced severe growth inhibition reducing shoot and root biomass by up to 53% and 64%, respectively and triggered significant lipid peroxidation (0.35–0.5 nmol TBARS /g dry biomass), comprehensive LC-MS/MS profiling revealed a strategic metabolic “pivot.” We observed a systematic depletion of charged polar amino acids, including asparagine (80.95 µg/g dry biomass) and glutamine (996.7 µg/g dry biomass), which was contrasted by a massive 11-fold accumulation of the osmo-protectant proline (754.4 µg/g dry biomass). Furthermore, the results demonstrate a profound modulation of hormonal homeostasis, where the synchronized elevation of both indole-3-acetic acid (59.19 µg/g dry biomass) and abscisic acid (2.40 µg/g dry biomass) indicates an adaptive coordination between growth-regulating and stress-responsive pathways. Dynamic shifts in nucleotide metabolism were also evident, with monophosphate nucleotides exhibiting higher sensitivity than their corresponding nucleosides. The concurrent peak in FRAP and ORAC activities, alongside a dramatic increase in dopamine derivatives (8808 µg/g dry biomass), indicates that V. faba actively reroutes primary carbon and nitrogen resources toward the phenylpropanoid pathway for antioxidant defense. These findings provide a mechanistic framework for understanding how pulse crops reprogram their primary metabolism to survive high-phenolic organic waste exposure, highlighting the dual nature of OMW as both a phytotoxin and a potential metabolic stimulus.