Toxicity of Silver Nano Particuls, Molecular Reaction and Their Tolerance in Plants: A Review

Abstract

Uptake of AgNPs by plants depends on the size and shape as well as the exposure concentration of AgNPs, but mechanisms of AgNPs internalization and distribution in plants are not fully understood. Their impact on morphological and physiological features of plants depends on AgNP characteristics, transformation possibilities as well as on the plant species and developmental stage and the way of
exposure. Roots are the first tissue to be in contact with AgNP solution, toxic symptoms appear more frequently in roots than in shoots, although AgNPs also induce morphological modifications in the stem and leaves. The main subcellular targets affected by AgNPs are mitochondria, nucleus and in particular chloroplasts, which is in line with detrimental impact of AgNPs on the structure and function of the photosynthetic apparatus. Moreover, damaged chloroplasts contribute to ROS generation and oxidative stress has an important role in the phytotoxicity of AgNPs. However, the underlying mechanisms of AgNP-mediated ROS production need further investigations. Proteomic analyses indicate that AgNPs predominantly affect proteins related to cell metabolism, stress response and signaling. The question whether phytotoxic effect is specific for nanoparticles or it is the result of the action of Ag+ released from AgNPs in exposure solution and/or after biotransformation in the cellular structures remains unresolved.