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

Abstract

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.