The remediation potential of lead in two mustard species (Brassica carinata and B. juncea)

Ethiopian (Brassica carinata) and Indian (B. juncea) mustards from Brassicacea are important oily crops. Ethiopian mustard with a deep root system is resistant to drought and heat and Indian mustard is a promising plant for metal phytoremediation. Accordingly the potential for the absorption, tolerance and remedation of lead (Pb) by these species grown in contaminated soils were investigated. Plants were grown in greenhouse in soils contaminated with 15, 300 and 600 mg kg-1 of Pb, harvested after 7 weeks and analyzed for parameters including length, dry weight, leaf area, photosynthetic pigments and Pb concentration. Both species had great stress tolerance indices to Pb. Furthermore, Pb treatments did not significantly affect root and shoot lengths, dry weights and specific leaf area in both mustards. Although photosynthetic pigments in Ethiopian mustard remained unaffected by Pb treatments, the contents of chlorophylls and carotenoids decreased in 600 mg kg-1 Pb treatment in the Indian mustard. Root Pb concentrations of both Ethiopian and Indian mustard significantly increased with rise in lead contamination, so that the ratio of Pb concentration of root to soil (bioconcentration factor) increased. Pb concentration in the shoot of Ethiopian mustard was significantly increased in 600 mg kg-1 of Pb, which this amount in the control and treatment of 600 Pb was 7 and 30 mg kg-1, respectively. However, there was no significant change in other treatments. Both plants displayed low translocation factor for Pb. Thus, with regards to biomass, stress tolerance indices, high Pb concentration in root and thereby, high bioconcentration factors both Ethiopian and Indian mustards can be useful in phytostabilization Pb contaminated soils and remediation of these soils in urban and industrial areas.