Size-based dynamics of nanoparticles in plant growth and environmental stress tolerance: potential benefits and hazards

Abstract

Environmental stress conditions such as drought, salinity, and heavy metal toxicity can considerably reduce growth and productivity of plants. Nanotechnology offers efficient solutions to enhance plant growth under stressful environments. Nanoparticles (NPs; 1–100 nm) in the form of plant growth promoters, nanopesticides, and nanofertilizers improve the nutrient use efficiency, stress resistance, and soil cleaning and minimize environmental pollution. Nanoparticles also transform plant–microbe associations through the modulation of rhizosphere microbial populations as well as root exudation, influencing the health of the plant as well as ecosystem services. Their nanoscale size and huge surface area facilitate enhanced physiological action and mobility as well as uptake within plant systems, frequently leading to enhanced growth and yield. However, these same traits can also cause toxicity. Therefore, it is important to carefully consider the NPs' size-dependent effects. This review highlights the significance of particle size in plant–NP interactions, with a particular emphasis on their dual potential to cause toxicity and mitigate environmental stress. This is, to the best of our knowledge, the first thorough evaluation of size-dependent NP effects on plants and related microbes. The significance of creating safe, optimized nanomaterials that provide agronomic advantages with little ecological risk is also highlighted.