Impacts of ZnO nanoparticles and dissolved zinc (ZnSO4) on low temperature induced responses of wheat

Nanoparticles (NPs), due to their specific physical and chemical properties, can cause benefits and risks once they are released into the environment. Consideration of nano-specific impacts of nanomaterials is essential for the safe design of NPs applications. In the present study, the effects of ZnO NPs and ZnSO4 application on low temperature-induced responses was investigated in two wheat cultivars (Triticum aestivum L. spring cultivar Sivand and the winter cultivar Pishgam). Seedlings were grown in a Johnson nutrient solution and then exposed to the uptake solution containing zinc (Zn) from two sources of ZnSO4 and ZnO NPs and subjected to temperature treatments by incubating them in the dark at +25, +9, and −4 °C for 18 h. Our results indicate that ZnO NPs and ZnSO4 did not show the same effects on wheat cultivars at freezing temperature. The ZnO NPs led to an increase in malondialdehyde (MDA) content, higher electrolyte leakage, and intensified the freezing effects compared to ZnSO4 and Zn-free treatments, in Sivand. At optimum temperature, root MDA content and electrolyte leakage index (ELI) was greater in Sivand plants compared to Pishgam. The differences indicate that the two cultivars differ in their responses to ZnO NPs application and low temperatures. In general, Sivand reacted more sensitively to the ZnO NPs treatment compared to ZnSO4. Freezing temperature resulted in higher activity of superoxide dismutase (SOD), MDA content and ELI in both wheat cultivars. In Sivand, with regard to the activity of SOD, MDA content and ELI, ZnO NPs cause effects different from that of ZnSO4, which indicates that ZnO NPs used under the current experimental conditions because nano-specific risks under low temperatures.