Phytotoxicity Assay of Cu, Pb and Zn on Launaea cornuta and Sporobolus jacquemontii Grown in Heavy Metal contaminated soil

Abstract

In this paper, a phytotoxicity assay is used to assess the harmfulness and tolerance of L. cornuta and S. jacquemontii in phytoremediation of heavy metal-contaminated soils. The effects of Pb, Cu, and Zn concentrations in the soil on the number of leaves generated, root and shoot growth, and tolerance indices of the investigated plant species were analyzed. The experimental plants were grown in soil with 0, 100, 300, 600, 1500, 2000, 2500, and 3000 mg/kg dry soil weight (DW for Pb, Cu, and Zn). Sample preparation and laboratory analysis followed the standard methods. Data were analyzed with one-way analysis of variance (ANOVA) using GraphPad Instat 3.1 software. The growth mean of different treatments was compared using Duncan’s Multiple Range Test at p < 0.05. Plants grown in soil containing more than 300/kg DW metal contents exhibited a significant effect on the growth of the root and shoot. Concentrations lower than 300 did not show any significant effects. At 1500 mg/kgDW, the numbers and sizes of leaves decreased very significantly, while at 2000 mg/kgDW both plants failed to survive. The toxic effects of the metals on biomass production showed inhibition in the following trend: Zn>Cu>Pb. The results suggest that hyper accumulator plants can also be affected by metals in the soils on which they grow. Therefore, the application of L. cornuta and S. jacquemontii as phytoremediation plants at higher metal soil concentrations requires the application of soil amendments to minimize the toxicity effect of metal on the plants.