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Plant response to heavy metal toxicity: Comparative study between the hyperaccumulator Thlaspi caerulescens (ecotype Ganges) and nonaccumulator plants: Lettuce, radish, and alfalfa
Author(s) -
Benzarti Saoussen,
Mohri Shino,
Ono Yoshiro
Publication year - 2008
Publication title -
environmental toxicology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.813
H-Index - 77
eISSN - 1522-7278
pISSN - 1520-4081
DOI - 10.1002/tox.20405
Subject(s) - raphanus , hyperaccumulator , lactuca , ecotype , phytotoxicity , phytoremediation , brassicaceae , biology , botany , ecotoxicology , horticulture , medicago sativa , toxicology , ecology , contamination
Thlaspi caerulescens (alpine pennycress) is one of the best‐known heavy metal (HM) hyperaccumulating plant species. It exhibits the ability to extract and accumulate various HM at extremely high concentrations. In this hydroponic study, the performance of T. caerulescens (ecotype Ganges) to accumulate Cd, Zn, and Cu was compared with that of three nonaccumulator plants: alfalfa ( Medicago sativa ), radish ( Raphanus sativus ), and lettuce ( Lactuca sativa ). Plants were exposed to the separately dissolved HM salts for 7 days at a wide range of increasing concentrations: 0 (control: 1/5 Hoagland nutrient solution), 0.1, 1, 10, 100, and 1000 μM. The comparative study combined chemical, physiological, and ecotoxicological assessments. Excessive concentrations of HM (100 and 1000 μM) affected plant growth, photosynthesis, and phytoaccumulation efficiency. Root exudation for all plant species was highly and significantly correlated to HM concentration in exposure solutions and proved its importance to counter effect toxicity. T. caerulescens resisted better the phytotoxic effects of Cd and Zn (at 1000 μM each), and translocated them significantly within tissues (366 and 1290 μg g −1 , respectively). At the same HM level, T. caerulescens exhibited lower performances in accumulating Cu when compared with the rest of plant species, mainly alfalfa (298 μg g −1 ). Root elongation inhibition test confirmed the selective aptitude of T. caerulescens to better cope with Cd and Zn toxicities. MetPLATE bioassay showed greater sensitivity to HM toxicity with much lower EC 50 values for β‐galactosidase activity in E. coli . Nevertheless, exaggerated HM concentrations coupled with relatively short exposure time did not allow for an efficient metal phytoextraction thus a significant reduction of ecotoxicity. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008.