Performance of purslane (Portulaca oleracea) in nickel and cadmium contaminated soil as a heavy metals-removing crop

Specific plants can remove heavy metals from the soil and contribute to pollution remediation in cropping systems. Determining the level of highest heavy metals that a super-accumulator crop can withstand without reducing its yield is important for management. The objective of this study was to investigate the heavy metal-removing capacity of purslane by studying different stress criteria and by tracking its nickel and cadmium removal from germination to harvest. Therefore, pot experiments in outdoor condition were performed by heavy metal levels including nickel (0, 30, 60, 120 mg/kg) and cadmium (0, 10, 20, 40 mg/kg) in two seasons. The results of this research showed that different levels of nickel and cadmium had significant effects on the morphological and physiological characteristics of purslane and increased heavy metals concentration decreased significantly these characteristics. Comparisons of mean shoot and root dry weight and extraction percentage showed that the highest level belonged to the control plants while the lowest level was observed in the plants under combined treatment of nickel (120 mg/kg) and cadmium (40 mg/kg) and the single treatment of cadmium (40 mg/kg). Perhaps heavy metals by their effect on dry and fresh matter made negative influence on extraction. Furthermore, the toxic properties of cadmium were more than nickel and decreased most of the measured characteristics.