Toxic effect assessment of pollutant mixtures in Lemna minor by using polyphasic fluorescence kinetics

Abstract

Analysis of the fast chlorophyll fluorescence rise OJIP and O₂ evolution was carried out to assess the toxic effect of copper–diuron, paraquat or flazasulfuron mixtures caused by their interaction on duckweed. Information about energy absorption, electron transport and further metabolic events (e.g., ATP synthesis, CO₂ absorption) were obtained from the same fluorescence measurement. Copper with diuron or flazasulfuron acted in slight synergy on the efficiency of PSII photochemistry and on the fraction of inhibited centers. On the contrary, the effect of the Cu²⁺-paraquat mixture seemed to be antagonistic in regard to the PSII photochemistry parameters. The results suggest that complex interactions between contaminants could exist in natural environments. Polyphasic fluorescence kinetics generate large amounts of informative data that can be used not only to investigate the relationship between photosynthetic electron transport and herbicidal action mechanism but also as a useful physiological tool in detecting contaminant mixture toxicity, such as caused by copper, diuron, paraquat, and flazasulfuron, at an early stage.

Keywords:

• Herbicide
• copper
• chlorophyll fluorescence
• oxygen evolution
• duckweed

Acknowledgments

This work was cofinanced by the French Ministry of Environment, the local committee of Champagne-Ardenne, the “Département de la Marne” and the city of Reims via Europol’Agro.