Chlorophyll fluorescence as a bioindicator of effects on growth in aquaticmacrophytes from mixtures of polycyclic aromatic hydrocarbons

Chlorophyll-a fluorescence induction is a rapid technique for measuring pho tosynthetic electron transport in plants. To assess chlorophyll-a fluoresce nce as a bioindicator of effects of polycyclic aromatic hydrocarbon mixture s, chlorophyll-a fluorescence parameters and plant growth responses to expo sure to the wood preservative creosote were examined in the aquatic plants Lemna gibba and Myriophyllum spicatum. Exposure to creosote inhibited growt h of L. gibba (EC50 = 7.2 mg/L total polycyclic aromatic hydrocarbons) and M. spicatum (EC50 = 2.6 mg/L) despite differences in physiology. Creosote a lso diminished maximum PSII efficiency (F-v/F-m) (EC50 = 36 and 13 mg/L for L. gibba and M. spicatum) and the effective yield of photosystem [I photoc hemistry (DeltaF/F-m') (EC50 = 13 and 15 mg/L for L. gibba and M. spicatum) , The similarity between growth and chlorophyll-a fluorescence EC50s and sl opes of the response curves suggests a close mechanistic link between these end points. The predictive power of chlorophyll-a fluorescence as a bioind icator of whole-organism effects applied to complex contaminant mixtures is discussed.