Effects of the size and oxidation of graphene oxide on crop quality and specific molecular pathways

Applications of graphene-based nanomaterials in agriculture have attracted much attention, but their potential risks to crop quality and food safety are largely unknown. The present study found that graphene oxide (GO), GO quantum dots (GOQDs) and reduced GO (rGO) translocated from wheat stems to grains and formed large nanomaterial aggregates. The nanomaterials also reduced the globulin, prolamin, amylose and amylopectin contents by 8-28%, 11-25%, 5-34%, and 23-37%, respectively, decreased the levels of mineral elements and upregulated the soluble sugar content by 19-36% in wheat grains, while rGO downregulated the levels of proteins with nutrient reservoir activity to a greater extent than GO. The downregulation of alpha-amylase inhibitor was responsible for the observed decrease in starch content in grains. The decrease in the mineral element contents obtained with rGO and GOQD was greater than that observed with GO, and this effect was linked to the upregulation of calmodulin mediated by ABC transporters. GOQD and rGO changed the proteomic and metabolomic profiles more strongly than GO, suggesting that graphene materials with a small size and a low oxidation content are clearly more detrimental to grain quality. The above results provide an important basis for further nanomaterial design and agricultural applications. (C) 2018 Elsevier Ltd. All rights reserved.