Effect of ZnO nanoparticles on corn seedlings at different temperatures; X-ray absorption spectroscopy and ICP/OES studies

Abstract

Previous studies have shown that ZnO nanoparticles (NPs) affect corn germination and root growth. However, there is a lack of information about the effects of these NPs at different temperatures. In this study, corn seedlings were exposed to ZnO NPs (24±3nm) at 0–1600mgL−1 and ionic Zn 0–250mgL−1 for 15days. Germination, root elongation, Zn uptake and oxidation state, enzyme activity and protein expression were analyzed. At 20 and 25°C, 400mg ZnO NPs L−1 significantly reduced the germination (40 and 53% respectively), while no effect of Zn2+ was observed. Temperature and Zn concentration affected root growth. At 20°C, ZnO at 50, 400, and 1600mgL−1 reduced root growth by 18, 47, and 26% respectively. At 25°C, 100 and 800mgL−1 increased root growth by 22 and 27%, while at 30°C, 100mgL−1 reduced root growth by 42%. At 30°C, 0.1mgL−1 of Zn2+ increased the growth by 50%. Zn accumulation in seedlings was significant only at 1600mgL−1 ZnO and 250mgL−1 Zn2+. Ascorbate peroxidase activity increased by 24 and 57% under exposure to ZnO at 400 and 1600mgL−1 at 25°C. At any temperature the XAS analyses showed presence on NPs in roots. Exposure to ZnO NPs did not show changes in protein expression; however, a protein band with molecular weight of 85kDa decreased its expression at 30°C, while a protein of 75kDa increased its expression at 30°C. This study suggests that temperature may alter the way the ZnO NPs interact with plants.