Physiological effects of repeated foliar application of magnetite nanoparticles on maize plants

Iron is an essential micronutrient which is highly unavailable for plants in calcareous soils. Although the application of nanoparticles (NPs) to plants has been recently implemented, their long-term effects have not been studied yet. The objective of this study was to investigate whether the treatment of maize plants with 100 ppm iron nanoparticles (Fe-NPs) through their life cycle would affect the development of the second generation. The plants were treated with or without 100 ppm of Fe-NPs and 100 ppm of Fe-Ch, and their seeds were planted to obtain the second generation. The latter were again treated with or without Fe-NPs and Fe-Ch, and the results of two generations were compared. In the first generation, Fe-NPs treatments improved maize photosynthesis and hydrogen peroxide (H2O2) scavenging capacity and lowered the rate of membrane lipid peroxidation, compared to the control and Fe-Ch-treated plants. The improvement of calcium, Fe2+, total iron and ferritin contents was more pronounced in Fe-NPs treatments. However, the second progeny of Fe-NPs-treated plants showed less biomass, lower contents of chlorophyll, protein and calcium, and lower H2O2 scavenging capacity but higher amount of total iron content, compared with the control group and the first generation. In comparison, no adverse effects on growth parameters were observed in the plants which were treated with Fe-Ch for two subsequent generations, while their total iron and ferritin contents were remarkable. Due to the adverse effects of Fe-NPs in the second generation, more caution in its application for consecutive years is recommended.