Black mustard (Brassica nigra) was grown in pots amended with 41 nm ZnO (200–600 mg/kg soil) and 47 nm CuO (12.5–50 mg/kg soil) nanoparticles (NPs) to analyze growth response and yield characteristics. B. nigra seed germination was not affected by CuO NPs, but significant toxicity was observed by ZnO NP treatment. Both NPs significantly increased the growth profile of B. nigra, i.e., the stem height, number of leaves, average leaf area, number of branches, and number of nodes per plant. Application of ZnO and CuO NPs brought a significant dose-dependent decrease in primary root length; however, the number of secondary roots increased in the presence of CuO NPs. The average number of flowers and pods per plant significantly increased in the presence of CuO NPs. The seed yield, average seed weight per plant, and seed diameter parameters were observed to be better in the presence of CuO NPs as compared with ZnO NPs. Total protein contents and glucosinolates increased in the seeds grown in the NP-amended soil, while total oil contents decreased. Oil analysis depicted that oleic acid and linolenic acid percentage decreased while erucic acid percentage increased in seeds in the presence of both NPs in the soil. An atomic absorption spectrophotometer showed accumulation of Cu and Zn in B. nigra in the following order: root > stem > leaves > seeds. The study concludes that CuO and ZnO NPs have detrimental effect on the B. nigra plant and yield. The release of NPs and type of metal in NPs might also have a positive effect on the plant; however, their concentration in the soil also matters.

Due to unique physiochemical properties, nanoparticles (NPs) have acquired substantial attention in the field of research. However, threats of ecotoxicity and phytotoxicity have limited their biological applications. In this study in vivo experiments were performed to determine the effect of CuO (12.5, 25 and 50 mg/kg) and ZnO (200, 400 and 600 mg/kg) NPs on growth, and antioxidant activities of Brassica nigra. The results showed that CuO NPs did not affect the seed germination while presence of ZnO NPs in the soil generated an inhibitory effect. Both CuO and ZnO NPs positively influenced the growth of stem and other physiological parameters i.e. stem height increased (23%) at 50 mg/kg CuO while root length decreased (up to 44%) with an increase in the concentration of NPs. Phytochemical screening of apical, middle and basal leaves showed elevated phenolic and flavonoid contents in the range of 15.3-59 μg Gallic Acid Equivalent (GAE)/mg Dry Weight (DW) and 10-35 μg Querceitin Equivalent (QE)/mg DW, respectively, in NPs-treated plants. Antioxidant activity was higher in CuO NPs-treated plants as compared to ZnO and control plants. Results conclude that CuO and ZnO NPs at low concentrations can be exploited as nanofertilisers in agriculture fields.