EFFECTS OF SINGLE AND COMBINED STRESS OF CU OR ZN ON THE PHOTOSYNTHETIC FLUORESCENCE CHARACTERISTICS OF VALLISNERIA NATANS.

For investigating the response of chlorophyll fluorescence characteristics under single and combined of Cu or Zn stress, Vallisneria natans was selected as the experimental subject. V. natans was cultured 21 days under six concentration levels of Cu or Zn. The results showed that Fv/Fm, Fv/Fo, Y (II) and qP increased, and other indicators were almost unchanged in low- concentration treatment (Cu≤0.4mg/L, Zn≤4.0mg/L, Cu+Zn≤0.2+2.0 mg/L). V. natans could still maintain normal growth within such a range of heavy metal concentration, and it could maintain relatively a high photosynthetic activity. When heavy metal concentration was higher than the above concentration, the photosynthetic activity was inhibited. Fv/Fm, Fv/Fo, Y (II) and qP decreased gradually with the increasing stress concentration and stress time, while Y(NO), Y (NPQ), and qN showed different degrees of increase. The combined stress of Cu and Zn had a synergistic effect on the photosynthetic activity. V. natans can be used for ecological restoration of polluted water with low concentration of Cu and Zn. [ABSTRACT FROM AUTHOR]