Assessment of the effects of metal oxide nanoparticles on the growth, physiology and metabolic responses in in vitro grown eggplant (Solanum melongena)

Nanoparticles (NPs) are widely used in various domestic products and their usage is constantly increasing which in turn can raise several environmental health issues. Like other abiotic stresses, nanomaterials also affect the growth of crop plants. Solanum melongena is a common vegetable crop grown in the tropics and subtropics regions with medicinal properties. In this study, S. melongena was analyzed for its response to three commercially important metallic nanoparticles, namely NiO, CuO, and ZnO, at four different concentrations (100, 250, 500 and 1000 mg/L). The growth of the eggplant seedlings was suppressed by all the NPs in a concentration-dependent manner and among them, NiO was shown to be more toxic as it suppressed the root and shoot growth effectively. Total chlorophyll contents were decreased in the NP-treated plants compared to control plants. Significant changes were found in the secondary metabolites such as anthocyanins, total phenolic and total flavonoid contents in the NP-treated plants. A dose-dependent increase in the reactive oxygen species (ROS) generation was noticed in the NP-treated plants which are evidenced by the 4-nitro blue tetrazolium chloride (NBT) and 3,3′-diamiobenzidine (DAB) histochemical staining. The DNA damage imposed by the NP in the seedlings of eggplants may be due to the elevated ROS and MDA (malondialdehyde) production. NiO NP was found to be more toxic comparable to CuO and ZnO NPs in the present study. Apart from the toxic effects, nanoparticles also showed profound effects on the production of important secondary metabolites such as phenolics and flavonoid compounds.