Potential of Silver and Zinc Nanoparticles in Mediating Abiotic Stress Tolerance in Crop Plants

Being rooted, plants are highly vulnerable to extreme abiotic stress environment like high temperature, drought, and salinity, severely affecting the quality and yield of crops. Among the multiple approaches to fortifying plants, nanoparticles (NPs) have attracted global attention. In particular, silver (Ag) and zinc (Zn) NPs are very popular owing to their biosolubility, small size, and large surface area. Once NPs reach the outer membrane of plant cells, they move in through the plasmodesmata or endocytic pathways and are translocated to other organs via apoplastic and symplastic routes. NPs, upon reaching the xylem, are transferred to the shoots, and some flow back to the roots through the phloem. These NPs show notable stress protection in enhanced growth, seed germination, chlorophyll content, stomatal conductance, transpiration rate, and decreased reactive oxygen species (ROS) and membrane damage. Specifically, Ag and Zn NPs protect from mitochondrial dysfunction, ribosome disassembly, and DNA and protein damage. However, beyond a certain concentration, Ag and Zn, like other NPs, are cytotoxic and genotoxic, thereby causing excess ROS accumulation, DNA damage, chromosomal aberrations, and membrane damage leading to decreased leaf area, pollen viability, chlorophyll degradation, vacuole shrinkage, etc. Hence, only regulated exposure to NPs can help us achieve sustainable nano-agriculture in the near future. This chapter will probe into the role of Ag and Zn NPs in protecting plants from stressful abiotic conditions, along with insights into the cytotoxic nature and activity of NPs.