Effect of lead and cadmium on germination stage and application of vermicompost in concomitant pollution control by ornamental sunflower (Helianthus annuus "Sungold")

One of the methods of remediation and cleaning of soils contaminated with heavy metals is the use of organic compounds such as vermicompost to purify or stabilize the contamination. In this study, the effect of vermicompost on the uptake of heavy metals lead and cadmium by ornamental sunflower and the effect of these metals on germination and plant establishment characteristics were investigated. This study was carried out in two experiments of germination and greenhouse in 1397-98 in Islamic Azad University, Arak Branch in a factorial way in a completely randomized design. In the first experiment, concentrations of 50, 100 and 200 mg / l of lead nitrate and cadmium chloride were used and then germination indices were evaluated. In the second experiment, concentrations of 0, 5, 10 and 15 mg/kg of lead metal, concentrations of 0, 400 and 600 mg/kg of cadmium and three levels of 0, 15 and 30 kg/m2 of vermicompost to the ability to uptake heavy metals were used by ornamental sunflowers. The results of the first experiment showed that increasing the concentrations of heavy metals lead and cadmium reduced the length of root, shoot and germination indicators such as seed vigor index, germination rate index and average germination rate. The results of the second experiment showed that by increasing the concentration of lead and cadmium in the soil, the number of leaves and shoot length of ornamental sunflower decreased and the amount of soil and lead cadmium, lead and cadmium root and lead and cadmium shoot increased. The study achieves that H. annuus "Sungold" plant showed tolerance to lead and cadmium contamination and we recommend its capacity for the remediation of lead and cadmium contaminated soils. The activity of the enzyme superoxide dismutase also increased as the concentration of heavy metals in the culture medium increased. Vermicompost implementation was able to partially improve the negative effects of these heavy metals. With increasing the concentration of heavy metals, the activity of superoxide dismutase increased by 30-50% compared to the control. Vermicompost reduced the amount of these metals in the soil, roots and stems of the ornamental sunflower plant, and this ornamental plant can be introduced as a purifier of lead and cadmium contaminated areas.