Effect of Cadmium and Lead on Quantitative and Essential Oil Traits of Peppermint (Mentha piperita L.)

Cadmium (Cd) and lead (Pb) are particularly noteworthy metals that can pollute the air, soil and water contributing to serious environmental problems. Tests were done on concentrations of Pb and Cd; treatments tested in the experiment were as follows; Cd concentrations (10, 20, 40, 60, 80, 100 ppm) and concentrations of Pb (100, 300, 600, 900, 1200, 1500 ppm) and control. Tests were done on Mentha piperita L. in a greenhouse, arranged as a randomized complete block design with three replications. Rhizomes with uniform weight were planted in pots 30×50×35 cm. Plants were irrigated with Cd and Pb chloride after germination of all rhizomes. Results demonstrated that with increasing concentrations of Cd and Pb there was a decrease in fresh and dry weights, main stem height, leaf area per plant, leaf number, number of nodes per main stem and essential oil of peppermint compared to the control. Fresh weights were decreased at 100 ppm of Cd and 1500 ppm of Pb, 18.16% and 24.55%, respectively compared to the control at the first harvest. At the second harvest, these decreases were 15.24% and 32.72%, respectively. At the highest concentrations of Cd and Pb, dry weight of peppermint was dropped 22.92% and 39.01% at the first harvest. For the second harvest, decreased dry weights were 25.88% and 26.77% respectively. It seems that peppermint can tolerate waste water or soil polluted with medium range of Cd and Pb concentrations and the essential oil percentage was not affected by these concentrations.