Interplay of metal-based nanoparticles with plant rhizosphere microenvironment: implications for nanosafety and nano-enabled sustainable agriculture

The development of nanotechnology and the widespread application of metal-based nanoparticles (MNPs) in various consumer products have released a large number of nanoparticles into soil environment, especially agricultural systems. The accumulation of MNPs in the soil has threatened the soil health and plant growth. This review uses Ag NPs and ZnO NPs which have been widely used in commercial products as examples, combined with other kinds of MNPs (such as TiO2, CuO, CeO2, etc.) to discuss the interplay of MNPs with plant rhizosphere microenvironment. Plant rhizosphere properties, such as soil pH, organic matter, microorganisms, or rhizosphere exudates, can affect the environmental behaviors of MNPs. Further MNPs can alter rhizosphere soil chemistry and microbial properties which in turn affect the MNP behaviour and biological effects. Meanwhile, MNPs can cause damage to roots or be absorbed by plant roots to induce oxidative stress in plant roots, affecting plant root growth and nutrient uptake. Finally, given the inadequacies of current research on MNPs and soil-plant systems, several future research priorities are recommended.