Bouzid Nedjimi
Cadmium (Cd) pollution of the agricultural sector has occurred as a grave major environmental problem, affecting crop productivity, biotope sustainability, and human health due to its rapid transfer into the trophic chain. The presence of this heavy metal (HM) in organs and plant tissues alters several biological features, like tissue water balance, mineral homeostasis, and photosynthetic apparatus, causing ultimately a net reduction of plant development and crop productivity. Although many strategies have been used to combat Cd pollution, including fertilization and chemical application, their effectiveness remains uncertain depending on environmental circumstances. Due to its high bioavailability, surface area, and reactivity, exogenous applications of silicon (Si), particularly in the form of nanoparticles (Si–NPs), have revealed a promising alternative for boosting plant resilience to HM toxicity in the more recent era of nanotechnology. Despite the existence of recent relevant papers on the useful application of Si–NPs to mitigate HM toxicity, a general synthesis summarizing their effects on enhancing Cd tolerance across different crop species is still scarce. We hypothesize that Si–NPs possess multifaceted roles in improving plant Cd tolerance through harmonized mechanisms at molecular, biochemical, and physiological levels. Si–NPs increase plant Cd tolerance by enhancing ion homeostasis, strengthening antioxidant defenses and membrane stability, maintaining chlorophyll pigment concentration, and upregulating the expression of specific genes implicated in transport and Cd detoxification. The current overview provides a synthesis of the most recent findings about the ameliorative application of Si-NPs on plant growth and physiological attributes and makes evidence of their potential as a valuable strategy for enhancing plant tolerance and ensuring food safety under Cd stress. Further investigations are still required to clarify their long-term persistence, application manners, optimal dosage, and interactions with other nutrients. To ensure an effective, safe integration of these composites in conventional agronomic amendments, fuller research in these areas will be necessary.