Recent advances in nano-enabled plant salt tolerance: Methods of application, risk assessment, opportunities and future prospects

Salinity is a major issue threatening global food security. Among the different strategies, nanotechnology has shown tremendous potential for improving crop production under abiotic stresses such as salinity. In this review, we discuss the environmental challenges associated with the different methods of nanomaterial application, including seed nanopriming, as well as foliar and soil/root application. Based on previous research, nanopriming uses less nanomaterials and has minimal concerns regarding environmental safety and the food chain. We discuss in detail the preventive measures for the safe and sustainable use of nanomaterials in agriculture based on the application methods. Furthermore, we summarize the role of antioxidant enzyme-triggering nanomaterials and direct reactive oxygen species (ROS) scavenging nanomaterials (nanozymes) in plant salt tolerance. Nanomaterials can improve sodium (Na⁺) and potassium (K⁺) homeostasis through various anatomical, physiological, and molecular mechanisms while improving plant salt tolerance. The role of nanomaterials in modulating plant photosynthesis and hormonal balance has been largely overlooked. We also identify research gaps and provide guidelines for future research work. This review provides guidelines for helping researchers to understand the proper design of nanoparticles (NPs) and different plant-related factors while using NPs for plant stress tolerance. These considerations will help to improve the efficient delivery of NPs into plants. Furthermore, after gaining sufficient scientific knowledge and better understanding, NPs can be integral to sustainable agriculture, while saving costs and reducing biosafety concerns and environmental pollution.