Contamination of agricultural land by chromium (Cr) can inhibit physiological and biochemical processes in plants, leading to reduced crop productivity and food/feed safety. Owing to their fine size, large surface area, and high adsorption affinity for metals, nanomaterials have shown a potential for phytoremediation of heavy metal-contaminated soils. Nanomaterials enhance fitness of plants under metal stress through their modifying effects on plant physiology and biochemistry. The aim of this study was to assess the performance of sunflower (Helianthus annuus) plants grown in soil spiked with hexavalent chromium (Cr IV; 0, 75 and 150 ppm) and the potential role of nano-zerovalent iron ( Fe0 nanoparticles; 0, 1 and 2%) to ameliorate Cr toxicity. Results revealed that the Cr uptake decreased by increasing the concentration of Fe0 nanoparticles, causing a significant enhancement in plant morphological and physiological attributes. Treatment with Fe0 nanoparticles reduced bioaccumulation factor (BAF) (in both root and shoot tissues) and translocation factor (TF); however, the magnitude of BAF and TF decreased significantly by increasing the level of Cr(VI). Chromium stress increased the activities of antioxidant enzymes, which further increased by Fe0 nanoparticle application, resulting in improved growth traits. A significant positive correlation was found between growth, BAF and TF of seedlings treated with Fe0 nanoparticles (both 1 and 2%) upon Cr exposure (75 and 150 ppm). The results demonstrated the potential of Fe0 nanoparticles to improve performance of sunflower plants under Cr toxicity through reducing their Cr uptake, which was accompanied by enhanced activity of detoxification enzymes (SOD, CAT, POX, and APX) in cells.
