Nutritional quality of bean seeds harvested from plants grown in different soils amended with coated and uncoated zinc oxide nanomaterials

Abstract

The effects of soil properties on nanomaterial (NM) interactions with plants are not well understood. Bean (Phaseolus vulgaris) plants were grown to maturity in natural soil (NS) or organic matter (OM)-enriched soil (ES) amended with either uncoated (Z-COTE), hydrophobically-coated (Z-COTE HP1) ZnO NMs, bulk ZnO, or ZnCl₂ at 0–500 mg kg⁻¹. At harvest, yield and seed nutrient composition were assessed. The soil × compound interaction reduced the maturation time by about 25 days and increased the seed yield (∼155%) in ES, compared to NS. In NS, ZnCl₂ at 125 mg kg⁻¹ produced 10% less seed protein than the control, and disregarding the concentration, seeds from ZnCl₂ showed the highest relative sugar content (102%, compared with the other compounds), while in NS, seeds from Z-COTE HP1 accumulated the highest relative sugar content (44% more than Z-COTE and ZnCl₂). In addition, seeds from ES + Z-COTE HP1 had 19% less Zn than the rest of the compounds. In ES, the OM enrichment and reduction in pH enhanced the accumulation of Zn (38%), K (64%), S (44%), P (83%), Mg (86%), Ca (70%), Fe (89%), and Mn (85%), but reduced Mo under Z-COTE HP1 and ZnCl₂, in comparison to NS seeds. Compared to the controls, ZnCl₂ at 500 mg kg⁻¹ reduced the K content in NS and ES (25% and 13%) but increased the P content in NS (66%). In general, Z-COTE and Z-COTE HP1 affected seed nutritional elements in a similar manner. However, the results indicate that the effects of ZnO NMs in bean plants vary with soil composition.