Cadmium tolerance in Thlaspi caerulescens - I. Growth parameters, metal accumulation and phytochelatin synthesis in response to cadmium

Abstract

A population of the metallophyte, Thlaspi caerulescens, originating from a Cd-Pb-Zn old mining and smelter site at Plombieres (Belgium) was studied. T. caerulescens was cultivated hydroponically to investigate Cd uptake and tolerance. Cd was added to Hoagland's medium at concentration range from 5 to 500 mu M. The plants could tolerate 500 mu M Cd in the solution showing only minor visible symptoms of toxicity but with a 32% decrease in fresh weight. After 14 days at 500 mu M. Cd content in roots and shoots was 707 and 602 mg kg(-1) of dry weight (d.w.), respectively. Application of Cd to hydroponically cultivated T. caerulescens induced the accumulation of PCs in plant roots and shoots. Buthionine sulfoximine (BSO) application almost completely reduced (by 98-100%) the accumulation of PCs without simultaneous increase in plants sensitivity to Cd. These results suggest a minor if any role of PCs in tolerance to Cd of the studied population of T. caerulescens in hydroponics. On the other hand, no PC accumulation was detected either in T. caerulescens plants growing in their natural environment at Plombieres or in plants growing in their native soil in a greenhouse. These results suggest that naturally selected tolerance in T. caerulescens population from Plombieres is not associated with enhanced PCs synthesis. (c) 2004 Elsevier B.V. All rights reserved.