Uptake, Translocation, Toxicity, and Impact of Nanoparticles on Plant Physiological Processes

The application of nanotechnology in agriculture has increased rapidly. However, the fate and effects of various nanoparticles on the soil, plants, and humans are not fully understood. Reports indicate that nanoparticles exhibit positive and negative impacts on biota due to their size, surface property, concentration within the system, and species or cell type under test. In plants, nanoparticles are translocated either by apoplast or symplast pathway or both. Also, it is not clear whether the nanoparticles entering the plant system remain as nanoparticles or are biotransformed into ionic forms or other organic compounds. Controversial results on the toxicity effects of nanomaterials on the plant system are available. In general, the nanomaterial toxicity was exerted by producing reactive oxygen species, leading to damage or denaturation of various biomolecules. The intensity of cyto- and geno-toxicity depends on the physical and chemical properties of nanoparticles. Based on the literature survey, it is observed that the effects of nanoparticles on the growth, photosynthesis, and primary and secondary metabolism of plants are both positive and negative; the response of these processes to the nanoparticle was associated with the type of nanoparticle, the concentration within the tissue, crop species, and stage of growth. Future studies should focus on addressing the key knowledge gaps in understanding the responses of plants to nanoparticles at all levels through global transcriptome, proteome, and metabolome assays and evaluating nanoparticles under field conditions at realistic exposure concentrations to determine the level of entry of nanoparticles into the food chain and assess the impact of nanoparticles on the ecosystem.