The Role of Root Damage in the Chelate-Enhanced Accumulation of Lead by Indian Mustard Plants

Abstract

In the present study, increasing ethylenediaminetetraacetic acid (EDTA) concentration from 0 to 0.5 mmol L⁻¹ resulted in progressive increases in root elongation and in shoot and root dry matter (DM) of Indian mustard seedlings (Brassica juncea. L.) exposed at 0.5 mmol L⁻¹ of lead (Pb). The highest concentration of Pb in the shoots of Indian mustard reached 1140 mg kg⁻¹  dry weight (DW) in the treatment with 0.5 mmol L⁻¹ of Pb + 0.25 mmol L⁻¹ of EDTA. A significantly positive correlation was found between the concentrations of Pb and EDTA in the shoots of mustard. Roots were pretreated with an MC (methanol:trichloromethane) solution, 0.1 mol L⁻¹ of HCl, and 65°C hot water. The plants were then exposed to 0.5 mmol L⁻¹ of Pb + 3 mmol L⁻¹ of EDTA in solution for 2 d. The pretreatments with MC, HCl, and hot water all increased the concentration of Pb in shoots by 14-, 7-, and 15-fold, respectively, compared with the shoots that had not been pretreated. Therefore, some physiological damage to roots would be useful to enhance the uptake of metal by plants and to minimize the application of doses of chelates in the practical operation of chelate-assisted phytoremediation.

KEY WORDS:

• ethylenediaminetetraacetic acid (EDTA)
• lead (Pb)
• mustard
• root damage
• phytoremediation

ACKNOWLEDGEMENTS

This research project was supported by the Social Development Program of Jiangsu Province (BS2003029), the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institutions, the Chinese Ministry of Education, the National Science Foundation of China (No: 30300211), and the Research Grants Council of the Hong Kong SAR Government (PolyU 5046/02E).