Aim: Nowadays, in the industrial areas, there is a problem of simultaneous contamination of soil with heavy metals and lack of organic matter that can impede the growth of plants. Thus, this study was done to investigate the effect of organic amendments on decreases plant abiotic stress in a soil cocontaminated with lead (Pb) and cadmium (Cd) under ornamental sunflower cultivation. Materials and Methods: Treatments consisted of applying vermicompost (0, 15, and 30 t/ha) and soil polluted with Cd (0, 5, 10, and 15 mg/kg soil) and Pb (0, 400, and 600 mg/kg soil), and the plant used in this experiment was ornamental sunflower. After 8 weeks of the experiment, plants were harvested, and soil and plant Zn and Fe were measured using the atomic absorption spectroscopy. In addition, the ascorbate peroxidase (APX) and peroxidase (POX) of the plant were measured. Results: The application of 15 and 30 t/ha vermicompost significantly depressed the APX and POX activity by 12.1% and 14.6%, respectively. While the plant Fe and Zn concentration was significantly increased by 11.1% and 13.6%, respectively. Increasing soil pollution to Cd to 15 mg/kg soil significantly increased the APX and POX enzyme activities of the sunflower by 14.6% and 13.3%, respectively. Conclusion: It can be concluded that the interaction effect of Fe and Zn with heavy metal can help to decrease the plant abiotic stress that is a positive point in the environmental research. However, the role of organic amendments in decreasing heavy metals availability cannot be ignored.
