In this study a solution culture experiment was conducted to investigate the response of phytochelatins (PCs) in a floating aquatic plant Pistia stratiotes L. and a submerged one Elodea nuttallii exposed to a range of lower concentrations of cadmium (Cd) (0.01~0.64µmol/L). It was observed that two macrophytes showed obvious cumulative effects to lower concentrations of Cd exposure. PCs were significantly induced in P. stratiotes L. in a dose-dependent manner and increased with the increase of exogenous Cd concentrations. Cd concentrations at 0.08~0.64µmol/L were highly toxic to P. stratiotes L., accompanied by the dramatic production of PCs of plant tissues, especially in roots. Regressive analysis showed that there were linearly positive relationships between PC contents and Cd toxicity in E. nuttallii and P. stratiotes L.. It was indicated that PCs could be a promising biomarker for estimating Cd toxicity. Compared with E. nuttallii, PCs in roots of P. stratiotes L. was sensitive to Cd contamination and may be a sensitive indicator to reflect Cd toxicity in the aquatic ecosystem.
