Chemical and Biological Interactions of Nano-Selenium in the Rhizosphere: Implications for Plant Heavy Metal Stress Tolerance

The plant root system dynamically grows and senses stress, especially phytotoxic heavy metals (HMs), which threaten plant growth and human health through food contamination. Agricultural soils act as reservoirs and pathways for HMs, with accumulation intensified by human activities, including industrial discharges, mining, and heavy use of agrochemicals. Persistent HMs, including cadmium, lead, chromium, and arsenic, alter soil properties, disrupt microbes, and impair nutrient cycling. Strategies to reduce HM stress in plants include nanomaterials, noted for their high reactivity and tunability. Nano-selenium (nano-Se), a trace element, shows promise in regulating plant stress tolerance. Evidence indicates that nano-Se reduces HM uptake and translocation by strengthening antioxidant defenses and modulating rhizosphere and hormonal processes, thereby enhancing root growth, microbial activity, and nutrient-water uptake under metal stress. This review summarizes recent advances in nano-Se signaling, focusing on rhizosphere chemistry and plant-microbe interactions, and examines their potential for sustainable crop growth in HM-polluted soils.