Nanoparticles and salinity stress: Emerging insights into plant responses and stress mitigation

• Nanoparticles improve plant stress tolerance by regulating Na⁺/K⁺ homeostasis. • Nano-mediated antioxidant activation reduces ROS and protects photosynthesis. • Nanoparticle efficiency depends on size, surface chemistry, and rhizosphere traits. • Nanoparticles modulate stress-related genes and may induce epigenetic stress memory. • Field validation is needed to address dose toxicity, environmental fate, and food safety. Salinity stress is a major abiotic constraint limiting agricultural productivity worldwide, a challenge that is expected to intensify under climate change and unsustainable land-use practices. Salinity disrupts plant growth through osmotic stress, ionic toxicity, nutrient imbalance, oxidative damage, and extensive reprogramming of physiological and molecular processes. Although plants possess intrinsic adaptive mechanisms, conventional strategies for managing salinity stress remain insufficient to ensure sustainable crop production. In recent years, nanotechnology has emerged as a promising approach to enhance plant resilience against salinity stress by improving nutrient use efficiency, modulating stress signaling pathways, and reinforcing antioxidant defense systems. This review critically synthesizes current knowledge on the roles of nanoparticles (NPs) in mitigating salinity stress in plants, with a particular focus on their uptake, translocation, and interactions at physiological, molecular, and epigenetic levels. We discuss how engineered NPs influence ion homeostasis, reactive oxygen species (ROS) regulation, hormonal balance, gene expression, and epigenetic modifications that collectively underpin enhanced salt tolerance. Special attention is given to NP-mediated regulation of key transporters, stress-responsive genes, antioxidant enzymes, and signaling networks, as well as emerging evidence for nano-enabled stress memory and epigenetic priming. Furthermore, the review highlights the dual nature of NPs, emphasizing both their potential as nano-fertilizers and plant biostimulants, as well as the associated risks of phytotoxicity, environmental persistence, and food-chain safety concerns. Finally, we outline critical knowledge gaps, regulatory challenges, and future research directions necessary for translating laboratory-scale findings into safe, effective, and field-applicable nano-enabled strategies. Overall, this work provides an integrative framework for understanding NP–plant–salinity interactions and underscores the potential of nanotechnology to support sustainable and climate-resilient agricultural systems.