Abstract: In simulated tailwaters different in concentration of CuSO₄ and EDTA-Cu, Potamogeton crispus was planted. Growth of the plants was monitored regularly and PSII effective fluorescence yield (F_v/F_m), photochemical quenching (q_P) and non-photochemical quenching (q_N) of photosynthesis of the plants were determined with a underwater saturation pulse chlorophyll fluorescence analyzer (DIVING-PAM) to explore ecological response of the plants in purifying low concentration copper containing tailwater . Results show that P. crispus could adsorb and enrich copper ions, the capacity of absorbingmore CuSO₄ is higher than of EDTA-Cu. CuSO₄ was less toxic to the plant and more or less conducive to its the growth of the plant. In CuSO₄ treatments when CuSO₄ concentration was 0.01, 0.3, 0.5 and 1.0 mg·L^-1, the number of leaves per plant was 292.5%, 390.0%, 155% and 45% ,as many as that in the control, respectively. However, EDTA-Cu did not have much effect or much toxicity on growth of the plant when it was within the range of concentrations in the test. With rising concentration of CuSO₄ and EDTA-Cu, R_ET, F_v/F_m, q_P and q_N varied significantly indicating that a certain concentration of copper ion can increase the transfer rate and share of photoelectrons and promote photosynthesis and is quite low in toxicity to PSII reaction center of the plants as well.

Key words: Potamogeton crispus, photosynthetic fluorescence, CuSO₄, EDTA-Cu, toxicity