Short-term effect of zinc oxide nanoparticles (ZnO-NPs) on Carum capticum growth and physiological effects under hydroponic condition

This study investigated the growth and physiological response in medicinal plant Carum copticum exposed to zinc oxide nanoparticles (ZnO-NPs). Treatments of 0.1, 0.2, 1, 5 and 25µM of ZnO-NPs compared with 0.2 µM ZnSO4 (control; Zn form in Johnson solution) were applied in culture media under hydroponic conditions. The plants shoot/root length, and water content, H2O2, anthocyanin and activity POD enzyme were measured. The root length was more sensitive to ZnO-NPs than shoot length. The 0.2 and 1 µM NPs increased plant fresh weight by 96.8 and 115.2%, respectively. The shoot and root water content increased at 0.1-25 µM NPs treatments by 40-51% and 26-34% compared to the control group, respectively. The increase in POD enzyme was accompanied by increased length and fresh weight and anthocyanin contents under ZnO-NPs. The 25 µM ZnO NPs (high level) resulted in 36% shoot length, 44% root length, 38% plant fresh weight and 27% anthocyanin decline, while increased 40% shoot water content, 26% root water content, 17% H2O2 and 69% POD activity compared with control. Overall, 25 μM ZnO-NPs treatment induced higher damages to the growth parameters due to H2O2 increase (oxidative stress) and the failure of the enzymatic and non-enzymatic mechanisms (anthocyanin and POD) to cope with the H2O2 enhancement induced by ZnO-NPs.