Assessment of toxic interaction of nano zinc oxide and nano copper oxide on germination of Raphanus sativus seeds.

Multiple applications of nanoparticles (NPs) could result in their potential release into agricultural systems and raised concerns about food safety. The NPs once released in the environment may interact with numerous pollutants, including other NPs. Present study assessed the impact of a single (CuO and ZnO NPs) and binary mixture (CuO+ZnO NPs) on the germination of Raphanus sativus seeds with a wide range of exposure concentration (0-1000 mg/L). Both the NPs have shown a deleterious effect on seeds at exposure concentration greater than 10 mg/L. Antagonistic interaction between effects of CuO and ZnO NPs on seeds was noticed for all the exposed concentrations. CuO NPs showed higher absorption capacity on the seedling surface than ZnO NPs. Internal uptake of Zn in ZnO NP-exposed seedlings was found to be greater than that due to CuO NP-exposed seedlings. Three different types of exposure adversely affected seed germination (reduction in root length, shoot length, and fresh weight). Reduction in growth parameters (length and weight) with concentration was compared using log-logistic dose-response model of "DRC" package of the "R" software, and EC50 was determined. As per EC50 values, the toxicity of CuO NPs was found to be maximum followed by CuO+ZnO NPs and then minimum for ZnO NPs. Seedlings accumulated Cu and Zn metals, and higher uptake was recorded for Zn (reported as mg/g seedling dry weight). The order of toxicity was found as CuO NPs > binary mixture (CuO+ZnO) NPs > ZnO NPs. Exposure concentration greater than 10 mg/L resulted in significant toxicity and uptake in germinated seedlings. These findings indicated that exposure of the mixture of NPs during germination might give different effects and thus, further attempts could prove quite beneficial to the literature.