Comparison of the effects of commercial coated and uncoated ZnO nanomaterials and Zn compounds in kidney bean (Phaseolus vulgaris) plants.

Bean (Phaseolus vulgaris) plants were grown for 45 days in soil amended with either uncoated (Z-COTE®) and coated (Z-COTE HP1®) ZnO nanomaterials (NMs), bulk ZnO and ZnCl2, at 0-500mg/kg. At harvest, growth parameters, chlorophyll, and essential elements were determined. None of the treatments affected germination and pod production, and only ZnCl2 at 250 and 500mg/kg reduced relative chlorophyll content by 34% and 46%, respectively. While Z-COTE® did not produce phenotypic changes, Z-COTE HP1®, at all concentrations, increased root length (∼44%) and leaf length (∼13%) compared with control. Bulk ZnO reduced root length (53%) at 62.5mg/kg and ZnCl2 reduced leaf length (16%) at 125mg/kg. Z-COTE®, at 125mg/kg, increased Zn by 203%, 139%, and 76% in nodules, stems, and leaves, respectively; while at the same concentration, Z-COTE HP1® increased Zn by 89%, 97%, and 103% in roots, stems, and leaves, respectively. At 125mg/kg, Z-COTE HP1® increased root S (65%) and Mg (65%), while Z-COTE® increased stem B (122%) and Mn (73%). Bulk ZnO and ZnCl2 imposed more toxicity to kidney bean than the NMs, since they reduced root and leaf elongation, respectively, and the concentration of several essential elements in tissues.