Use of chlorophyll fluorescence as a tool for determination of herbicide toxic effect: Review

Chlorophyll fluorescence-based methods have been used for many years to study the effect of environmental factors (including herbicides) on plants, and, with the development of very sensitive fluorometers, these methods have become very useful in ecotoxicological studies. This review provides a summary of the research done over the last 10 years concerning the study, by using chlorophyll fluorescence, of the herbicide toxic effects. Although numerous parameters are available, it is striking to notice that the majority of the studies done in the recent years used only a limited number of parameters, thus restraining in some way the interpretation of the obtained results. Furthermore, the use of the maximal photosystem II quantum yield to evaluate toxic effect of herbicides is probably not the best parameter due to its relatively low sensitivity. One should take the advantage of using other parameters such as the operational PSII quantum yield and the non-photochemical quenching since they integrate the entire physiological state of the plant and therefore should be more sensitive. We also recommend the systematic determination of EC50 values in future studies since such determination will permit a more accurate comparison between published reports.