Accumulation, Detoxification, and Genotoxicity of Heavy Metals in Indian Mustard (Brassica Juncea L.)

Abstract

Plants of Indian mustard (Brassica juncea L.) were exposed to different concentrations (15, 30, 60, 120 μM) of (Cd, Cr, Cu, Pb) for 28 and 56 d for accumulation and detoxification studies. Metal accumulation in roots and shoots were analyzed and it was observed that roots accumulated a significant amount of Cd (1980 μg g⁻¹ dry weight), Cr (1540 μg g⁻¹ dry weight), Cu (1995 μg g⁻¹ dry weight), and Pb (2040 μg g⁻¹ dry weight) after 56 d of exposure, though in shoot this was 1110, 618, 795, and 409 μg g⁻¹ dry weight of Cd, Cr, Cu, and Pb, respectively. In order to assess detoxification mechanisms, non-protein thiols (NP-SH), glutathione (GSH) and phytochelatins (PCs) were analyzed in plants. An increase in the quantity of NP-SH (9.55), GSH (8.30), and PCs (1.25) μmol g⁻¹ FW were found at 15 μM of Cd, however, a gradual decline in quantity was observed from 15 μM of Cd onwards, after 56 d of exposure. For genotoxicity in plants, cytogenetic end-points such as mitotic index (MI), micronucleus formation (MN), mitotic aberrations (MA) and chromosome aberrations (CA) were examined in root meristem cells of B. juncea. Exposure of Cd revealed a significant (P < 0.05) inhibition of MI, induction of MA, CA, and MN in the root tips for 24 h. However, cells examined at 24 h post-exposure showed concentration-wise recovery in all the end-points. The data revealed that Indian mustard could be used as a potential accumulator of Cd, Cr, Cu, and Pb due to a good tolerance mechanisms provided by combined/concerted action of NP-SH, GSH, and PCs. Also, exposure of Cd can cause genotoxic effects in B. juncea L. through chromosomal mutations, MA, and MN formation.

KEY WORDS:

• Brassica juncea
• chromosome aberrations
• glutathione
• heavy metals
• micronucleus
• phytochelatins

ACKNOWLEDGMENTS

The authors gratefully acknowledge the Council of Scientific and Industrial Research, New Delhi, India for the financial support in the present study.