Foliar application of green-synthesized MoO₃ nanoparticles alleviates salinity stress in molokhia by boosting antioxidant defense and stress-related gene expression

Abstract

Abstract Background Salinity stress is a major global challenge that impairs plant growth by disrupting numerous physiological and biochemical processes. Nano-fertilizers, particularly green synthesized nanoparticles, offer a promising and eco-friendly strategy to enhance plant resilience and productivity under such stress. Accordingly, this study addresses a significant research gap by exploring the potential role of Molybdenum trioxide nanoparticles (MoO₃NPs) in improving salinity tolerance in molokhia, a topic that has received limited attention in previous studies. Results Molybdenum trioxide nanoparticles (MoO₃NPs) were fabricated using Medicago polymorpha fruit extract and characterized as spherical, orthorhombic α-MoO₃ with an average size of 9.2 ± 2.7 nm. Molokhia ( Corchorus olitorius L.) was foliar-sprayed with MoO₃NPs at various dosages (0, 25, 50, and 100 mg/L) to mitigate the harmful effects of salinity stress (250 mM NaCl) on 30-day-old Molokhia plants. Application of 250 mM NaCl significantly inhibited growth, photosynthetic pigments, antioxidant activity, and osmolyte accumulation, alongside increased oxidative stress markers (MDA and H 2 O 2 ). Foliar spraying with biogenic MoO 3 NPs under saline conditions, especially at 50 mg/L, effectively mitigated salt-induced damage by enhancing growth parameters, restoring photosynthetic pigment levels, and improving osmotic adjustment by boosting proline and soluble protein levels compared with control. Moreover, MoO 3 NPs treatment elevated enzymatic and non-enzymatic antioxidants (phenolics, flavonoids, glutathione, and ascorbic acid) and upregulated key stress-responsive genes ( phenylalanine (PAL), magnesium chelatase (CHLH), superoxide dismutase1 (SOD1), catalase2 (CAT2), and flavonol synthase (FLS) ), thereby reducing oxidative stress markers. These effects mitigated ROS accumulation, improved cellular stability, and enhanced overall plant resilience. Conclusion These findings highlight that green-synthesized MoO₃NPs act as efficient nanofertilizers that alleviate salinity stress by promoting growth, reinforcing antioxidant defenses, and modulating stress-related genes. This dual role not only enhances crop resilience but also enriches the medicinal and nutritional value of Molokhia.