Application of Nanoparticles in Plant In Vitro Culture for Micropropagation and Secondary Metabolite Production: A Review

This review summarizes recent studies on the use of nanoparticles (NPs) in plant in vitro clonal micropropagation and secondary metabolite production. The analyzed applications include culture initiation, shoot multiplication, rooting, acclimatization, callus culture, and hairy root culture. Because NPs’ effects are strongly endpoint-dependent, their effectiveness is evaluated separately for micropropagation endpoints, including contamination control, explant survival, multiplication rate, shoot and root development, and plantlet quality, and for metabolite-production endpoints, including biomass accumulation, target metabolite concentration, and total metabolite yield. Based on the quantitative analysis of published data, the most frequently beneficial NP size range was 20–60 nm, whereas effective concentrations, combining a positive effect on plant growth and the synthesis of secondary metabolites, were mainly within 1–120 mg L−1. For the most extensively studied NPs, the corresponding indicative concentration ranges were 15–45 mg L−1 for 25–40 nm Ag-NPs, 75–200 mg L−1 for 15–45 nm ZnO-NPs, 120–150 mg L−1 for 50–80 nm Se-NPs, and 90–145 mg L−1 for 54–55 nm Si-based NPs. Ag- and carbon-based nanomaterials showed relatively strong overall responses in micropropagation datasets, whereas Ag- and Se-NPs were often associated with enhanced target metabolite accumulation. NP responses depend on particle composition, synthesis method, surface properties, dose, culture system, species, genotype, and may involve phytotoxic or residue-related risks.