[Effect of the soil bulk density on the root morphology and cadmium uptake by Thlaspi caerulescens grown on Cd-contaminated soil].

A pot experiment was conducted using a soil contaminated with 2.12 mg x kg(-1) Cd to study the effect of the variety of the soil bulk density on the Zn/Cd uptake by the hyperaccumulator Thlaspi caerulescens and the removal of Cd and Zn from the soil. The contaminated soil received 0, 0.1%, 2% of soil conditioner and the plants were harvested after 100 days. The results showed that soil amendment with the soil conditioner (EB. a) significantly decreased the soil bulk density. Compared to the control, the bulk density value decreased from 1.27 g x cm(-3) to 1.09 g x cm(-3) at the level of 2% soil conditioner. The increased biomass of shoot and root was observed at the treatment of EB. a amendment. The total root length, root hair length and root/shoot ratio were all significantly enhanced (p < 0.05) by the addition of EB. a. The significant positive relationships between the total root length and the removed Cd/Zn from soil were determined (p < 0.05). Compared with the control,the total root length was increased by 2.6 folds at the addition of 2% soil conditioner; the Cd concentration and removal of Cd from soil were significantly elevated by 20% and 30% respectively. The phytoextraction efficiency of Cd was improved from 15% to 19%. However, the Zn concentration and removal of Zn were not significantly elevated by the addition of soil conditioner. The present results demonstrate that the decreased soil bulk density may improve the root system of T. caerulescens and enhance the phytoextraction efficiency of Cd.