Effects of Functionalized Iron Oxide Magnetic Nanoparticle Suspensions on Seed Morphology and Physiology in Yellow Maize and Chili Pepper

We evaluated the effects of suspensions of magnetite–maghemite nanocomposites functionalized with quaternized chitosan and phosphate groups on morpho-anatomical and physiological traits of yellow maize (Zea mays) and chili pepper (Capsicum annuum) seeds. A phytotoxicity assay was first conducted by applying aqueous suspensions of these nanocomposites to maize seeds at iron concentrations up to 100 ppm, using deionized water as the control under humid chamber conditions. After incubation, seeds treated with concentrations above 100 ppm exhibited reductions in biomass and root length compared with the control, suggesting phytotoxicity at high levels. Based on these results, suspensions containing 25, 35, and 45 ppm of iron, with corresponding phosphorus concentrations of 2.9, 4.0, and 5.2 ppm, were selected for a second in vitro assay using both maize and chili seeds. No statistically significant differences between treatments and control were detected for the variables measured. Germinated seeds from this assay were further evaluated under greenhouse conditions, where measured parameters also showed no significant differences between treatments and control in either crop. Overall, the findings indicate that aqueous suspensions of magnetite–maghemite nanocomposites with iron concentrations below 100 ppm do not produce phytotoxic effects on seed germination or morpho-anatomical and physiological traits measured.