Lead, zinc and copper accumulation and tolerance in populations of Paspalum distichum and Cynodon dactylon W.S. Shu a ,Z.H.Ye b ,C.Y.Lan a , Z.Q. Zhang a ,M.H.Wong b, * a School of Life Sciences and State Key Laboratory for Biocontrol, Zhongshan University, Guangzhou 510275, People’s Republic of China b Institute for Natural Resources and Environmental Management, and Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong, People’s Republic of China Received 29 March 2001; accepted 28 December 2001 ‘‘Capsule’’: Metal-tolerant populations of the plants Paspalum distichum and Cunodon dactylon were identified. Abstract Both Fankou and Lechang lead/zinc (Pb/Zn) mine tailings located at Guangdong Province contained high levels of total and DTPA-extractable Pb, Zn and Cu. Paspalum distichum and Cynodon dactylon were dominant species colonized naturally on the tailings.Lead,zincandcopperaccumulationandtoleranceofdifferentpopulationsofthetwograssesgrowingonthetailingswere investigated. Tillers of these populations including those from an uncontaminated area were subjected to the following concentra- tions:5,10,20,30and40mgl 1 Pb,2.5,5,10,20and30mgl 1 Zn,or0.25,0.50,1and2mgl 1 Cufor14days,respectively,then toleranceindex(TI)andEC 50 (theconcentrationsofmetalsinsolutionswhichreduce50%ofnormalrootgrowth)werecalculated. TheresultsindicatedthatbothLechangandFankoupopulationsofthetwograssesshowedagreatertolerancetothethreemetals than those growing on the uncontaminated area, which suggested that co-tolerant ecotypes have evolved in the two grasses. P. distichum collectedfromFankoutailingshadthehighesttolerancetoCuwhileLechangpopulationthehighesttolerancetoPband Zn among the tested populations, and tolerance levels in P. distichum were related to metal concentrations in the plants. P. dis- tichum hadabettergrowthperformancethan C. dactylon whenbothofthemweregrownonthetailingssites.Tolerantpopulations of these species would serve as potential candidates for re-vegetation of wastelands contaminated with Pb, Zn and Cu. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Heavy metal; Tolerance; Accumulation; Paspalum distichum; Cynodon dactylon 1. Introduction Metal tolerance refers to specific individuals of a spe- cies which are able to withstand greater amounts of toxicity than their immediate relatives on normal soil (Antonovics et al., 1971). Tolerance is therefore con- ferred by the possession of specific physiological mechanisms which effectively enable it to function nor- mally even in the presence of high concentrations of potential toxic elements (Baker, 1987). The phenom- enon of heavy metal tolerance in plants has attracted theinterestsofscientistsfor50yearssincethediscovery of Pb-tolerance of Agrostis tenuis grass (Bradshaw, 1952), and so far a substantial number of tolerant spe- cies or ecotypes have been identified around the world (Baker, 1987). The ecology, physiology, biochemistry, molecular biology, evolutionary aspects of metal toler- ance in plants have been extensively studied (Baker and Walker, 1990; Macnair, 1993; Ye et al., 1997a, b; Kar- enlampi et al., 2000). The metal tolerant plant materials are not only of scientific interest, but they are also adopted in several aspects of environmental protection, such as revegetation of mined wastelands and phyto- remediation of lands polluted with heavy metals, for long-term stabilization of wasteland surface and reduc- tion of potentially toxic elements (Bradshaw and Chad- wick, 1980; Raskin and Enseley, 2000; Terry and Ban˜uelos, 2000). Although some tolerant plant materi- als are now commercially available for restoration of metalliferous wastelands, there has been continuous interest in searching for native tolerant plant materials which adapt to local climatic conditions and are able to colonize metal-enriched soils for use in land recla- mation (Williamson et al., 1982; Sudhakar et al., 1992; 0269-7491/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0269-7491(02)00110-0 Environmental Pollution 120 (2002) 445–453 www.elsevier.com/locate/envpol * Corresponding author. Tel.: +852-2339-7050; fax: +852-2339- 5995. E-mail address: mhwong@hkbu.edu.hk (M.H. Wong).