Physiological responses induced by copper bioaccumulation in Eichhornia crassipes (Mart.)

Eichhornia crassipes (Mart.) has strong ability to remove Cu2+ from copper-contaminated water. Physiological responses in E. crassipes exposed to known concentrations of Cu2+ were examined in this study, and demonstrated that E. crassipes could accumulate 314 mg kg(-1) dry weight of Cu when exposed to 5 mg l(-1) of Cu2+ for periods up to 14 d. However, there were marked changes in physiology of the plant commencing at Cu2+ concentrations of 1 mg l(-1). Results of this study showed that E. crassipes could tolerate moderate concentrations (i.e. 0.5 mg l(-1)) of Cu2+, without significant changes in photosynthetic pigment concentrations, while high concentrations (i.e. 5 and 10 mg l(-1)) of Cu2+ resulted in substantial loss in pigment concentrations. Increases in malondiadehyde (MDA) content were also demonstrated in plant exposure to high Cu2+ concentrations. Soluble protein content increased to a level slightly higher than the control at < 0.5 mg l(-1) of Cu2+, but then decreased with exposure to > 1 mg l(-1) of Cu2+. Our results suggest that E. crassipes has a substantial capacity to accumulate copper when cultivated at moderate concentrations of Cu2+, without marked changes in its physiology. The findings indicate that E. crassipes is a promising possibility for phytoremediation of moderately Cu-contaminated water bodies.