Influence of α- and γ-Fe2O3 Nanoparticles on Watermelon (Citrullus lanatus) Physiology and Fruit Quality

Iron deficiency has been becoming a worldwide problem in crop cultivation. New approaches are desired to alleviate the iron-deficit chlorosis. Iron-containing nanomaterials could be effective to supply the iron to plants and promote plant growth. In this study, soil cultured watermelon plants were treated with 100, 200, and 400 ppm α- and γ-Fe2O3 nanoparticles (NPs), respectively. Growth and physiology parameters were investigated in a period of time. The study also evaluated the nutritional quality of watermelon fruit. Results showed that no elevation of plant growth or chlorophyll content was observed. All α- and γ-Fe2O3 NPs treatments had no positive influence on nutritional components including central and edge sugar content, and total amino acid content. An interesting result was that the vitamin C (VC) content of all NP treatments was significantly improved compared with the control group (without iron). In addition, we found that iron distribution of α- and γ-Fe2O3 NPs treatments was closely related to the concentrations of NPs. Both α- and γ-Fe2O3 NPs could accumulate in root, stem, and leaf of watermelon plants, but only 400 ppm γ-Fe2O3 NPs treatment was found to exist in watermelon fruit. Although no promotion of α- and γ-Fe2O3 NPs on the growth of watermelon plants was occurred, our results showed that both α- and γ-Fe2O3 NPs could enter plant roots and translocate upwards to other tissues. Our finds will provide data for the future applications of iron-containing nanomaterials in agricultural production.