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 alpha- and gamma -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 alpha- and gamma -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 alpha- and gamma -Fe2O3 NPs treatments was closely related to the concentrations of NPs. Both alpha- and gamma -Fe2O3 NPs could accumulate in root, stem, and leaf of watermelon plants, but only 400 ppm gamma -Fe2O3 NPs treatment was found to exist in watermelon fruit. Although no promotion of alpha- and gamma -Fe2O3 NPs on the growth of watermelon plants was occurred, our results showed that both alpha- and gamma -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.