Ulva lactuca extract as biostimulant for reducing salt stress effect in common bean crops

The massive proliferation of Ulva lactuca in the Nador lagoon has become a major environmental concern due to its accumulation, stranding, and decomposition along the coast, leading to ecological disturbances and social discomfort. Yet, seaweed extracts are increasingly recognized for their ability to stimulate plant growth and enhance resilience to both abiotic and biotic stresses, owing to their rich and diverse content of bioactive compounds. In a sustainable valorization approach aimed at mitigating the ecological impact of this invasive species, Ulva lactuca was investigated as a promising natural biostimulant, tested experimentally on common bean (Phaseolus vulgaris L.) under salt stress conditions. Controlled trials were conducted using common bean plants exposed to two levels of salt stress (moderate: 34.2 mM NaCl; high: 68.4 mM NaCl), with or without treatment with Ulva lactuca extract (ULE) applied at three concentrations (1%, 3%, and 6%). Results showed that ULE significantly enhanced plant growth under both non-stress and saline conditions, particularly at 1% and 3%. This positive effect was associated with improved morphological traits, chlorophyll content, antioxidant enzyme activities, and carbon-nitrogen metabolism, along with increased accumulation of key osmolytes. Additionally, ULE treatments reduced lipid peroxidation and suppressed reactive oxygen species (ROS) production. These findings highlight the potential of Ulva lactuca extract as an effective, eco-friendly biostimulant capable of alleviating salt stress in crops, especially in regions facing salinized irrigation water challenges. At the same time, this work offers an innovative and sustainable strategy to valorize an overabundant marine resource while addressing environmental concerns.