Evaluation of the application of suspensions of iron oxide magnetic nanoparticles functionalized with quaternized chitosan and phosphates on yellow maize and chili pepper plants

We have applied aqueous suspensions of magnetite-maghemite nanoparticles functionalized with quaternized chitosan and phosphate groups on yellow maize ( Zea Mays ) and chili pepper ( Capsicum annuum ) plants, at greenhouse conditions, to evaluate if any beneficial or adverse effects are produced by these nanocomposites in the development of these kind of plants at morphological and physiological level. Phytotoxicity assays with yellow maize seeds showed excellent germination percentages in all treatments evaluated, as well as increasing indicators of biomass and root length of germinated seeds for suspensions of nanoparticles with iron contents up to 50 ppm. Suspensions of nanoparticles with iron contents higher than 50 ppm led to decreasing indicators of biomass and root length of germinated seeds compared to lower iron contents. Iron contents of 100 ppm showed indicators lower than those of the control, suggesting phytotoxic effect of these nanocomposites for iron contents above 100 ppm. Measurements of morphological and physiological parameters of plants of both crops in greenhouse conditions, treated with suspensions of nanoparticles with iron-phosphorus contents of 25 − 3, 35 − 4 and 45 − 5 ppm, commercial fertilizer as positive control and tap water as a negative control did not evidence any phytotoxic or beneficial effect. The results suggest that, although these nanocomposites did not have a noticeable effect as vehicles of micro and macro nutrients as iron and phosphorus in the evaluated plants, they did not produce phytotoxic effects on them at the morphological and physiological level for iron contents less than 50 ppm, as they showed adequate growth and development.