Iron Nanoparticles-induced Improvement of Antioxidant Enzymes and Photosynthetic Pigments of Purslane (Portulaca oleracea L.) Under Cadmium Stress

Cadmium (Cd) is one of the most toxic metals affecting the environment and can severely restrict growth as well as development of animals plus plants in the soil. The aim of this study was to investigate the effect of foliar spraying of iron nanoparticles on antioxidant enzymes plus photosynthetic pigments of purslane (Portulaca oleracea L.) under Cd stress. We applied cadmium chloride at six levels (0, 25, 50, 75, 100 and 125 mg/kg soil) in the soil along with foliar spraying of iron nanoparticles at five levels (0, 0.25, 0.5, 0.75 and 1 g/L). The results indicated that chlorophyll content diminished with increasing Cd stress, while carotenoid content increased with fewer slopes. Foliar spraying of iron nanoparticles at 0.25 and 0.5 g/L improved leaf chlorophyll content in plants grown under 25 and 50 mg/kg of Cd in the soil. The activity of antioxidant enzymes at lower concentrations of Cd and without the foliar spraying of iron nanoparticles was partially enhanced. By increasing the amount of Cd in the soil, the highest activity of guaiacol peroxidase (GP) and ascorbate peroxidase (APX) was recorded when 1 g/L of iron nanoparticles was sprayed. Also, iron nanoparticles at the rate of 0.75 g/L maximized the activity of superoxide dismutase, indicating a positive effect of iron nanoparticles on Cd stress in purslane plants. Based on our results, foliar spraying of iron nanoparticles could enhance the purslane plant tolerance to cadmium through increasing levels of carotenoids and antioxidant enzymes activity.