[Stoichiometry of multi-elements in the zinc-cadmium hyperaccumulator Thlaspi caerulescens grown hydroponically under different zinc concentrations determined by ICP-AES].

Thlaspi caerulescens is commonly known as a zinc (Zn) and cadmium (Cd) hyperaccumulator, which can be used to clean up the Zn- and/or Cd-contaminated soil. However, it is unclear whether high soil Zn concentrations will stimulate undue accumulations of other elements to such an extent as to cause the nutrient unbalance in the soil. To address this question, the inductively coupled plasma-atomic emission spectrometry (ICP-AES) was employed to investigate the effect of Zn on the stoichiometry of Zn, Cd, K, P, Mg, Ca, Fe, Mn and Cu in T. caerulescens (Ganges ecotype) exposed to low, middle and high Zn concentrations (5, 50 and 500 micromol x L(-1), respectively) in a hydroponic experiment. The results showed that there were no significant variations in contents of Cd, K, P, Mg, Ca, Fe, Mn and Cu in the shoot of T. caerulescens, however, the Zn content in the shoot and root with 500 mciromol x L(-1) Zn treatment increased as much as 13 times higher than that with low Zn exposure, indicating that the plant is capable of Zn hyperaccumulating. The authors' study suggests that it is improbable to induce soil nutrient unbalance when T. caerulescensis (Ganges) is used for phytoremediation of Zn-contaminated soil, in that over-uptake of nutrient elements from the soil other than Zn was not observed, at least for the elements K, P, Mg, Ca, Fe, Mn and Cu.