Iron oxide nanoparticles and mycorrhizae in plant responses to drought and salinity stress: a review

Abstract

Global climate change is increasing the frequency and severity of drought and soil salinity, which are major constraints to crop productivity and long-term agricultural sustainability. These abiotic stresses disrupt water and ion homeostasis, increase the overproduction of reactive oxygen species (ROS), and impair photosynthetic efficiency, cellular integrity, and plant growth. To survive under these conditions, plants activate coordinated physiological, biochemical, and molecular responses involving antioxidant defense systems, hormonal signaling networks, transcriptional reprogramming, and epigenetic regulation. This review presents an integrated overview of plant responses to drought and salinity, with particular emphasis on oxidative stress regulation and the molecular mechanisms controlling ROS homeostasis. We summarize the roles of antioxidant enzymes and discuss how their expression is regulated by stress-responsive transcription factors and hormone-dependent pathways. Recent advances in epigenetic regulation, including DNA methylation, histone modifications, and small RNA-mediated pathways, are also highlighted as important contributors to stress memory and adaptive plasticity under recurrent drought and salinity. We further highlight emerging mitigation strategies based on iron oxide nanoparticles (IONPs) and arbuscular mycorrhizal fungi (AMF), which modulate redox balance, nutrient availability, hormonal crosstalk, and stress-responsive gene expression. Evidence suggests that IONPs enhance antioxidant capacity and ion homeostasis, while AMF improve water uptake, nutrient acquisition, and transcriptional coordination under stress. The combined application of IONPs and AMF shows synergistic potential by targeting shared signaling hubs such as ROS, ABA, and Ca²⁺, thereby strengthening plant resilience to drought and salinity. Finally, we discuss future perspectives for integrating nanotechnology, beneficial soil microorganisms, molecular breeding, and epigenetic approaches to develop sustainable, field-applicable strategies for enhancing crop resilience to drought and salinity in a changing climate.