title: Sites of toxicity of specific photooxidation products of anthracene to higher plants: inhibition of photosynthetic activity and electron transport in Lemna gibba L. G-3 (duckweed).
abstract: Sites of toxicity of polycyclic aromatic hydrocarbons (PAHs) were examined to determine if inhibition of photosynthetic activity could be correlated to whole-organism toxicity. The inhibition of photosynthesis was observed by detecting the induction kinetics of endogenous chlorophyll a (Chl a) fluorescence. Anthracene (ANT) photooxidation products were applied to the aquatic higher plant Lemna gibba L. G-3 at concentrations ranging from 0.01 to 10 ppm. The impact on Chl a fluorescence was found to correlate with whole-organism toxicity for the 13 PAH compounds tested in this in vivo study. The mechanism of toxic action starts with inhibition of photosystem I (PSI) or the cytochrome-b6/f complex, followed by photooxidative damage to photosystem II (PSII). To study the effects of oxygenated ANTs on photosynthesis in vivo, the IC(50)s for F(V)/F(M) (PSII activity) and F(Q)/F(M) (activity downstream from PSII) were determined. The IC(50)s for a decrease of F(Q)/F(M) for all 13 chemicals were on average twofold lower than those for F(V)/F(M). F(V)/F(M) was found to be a measure of acute toxicity, whereas F(Q)/F(M) was found to be a measure of chronic toxicity. Thus, Chl a fluorescence by use of the whole organism was able to detect the impacts of photomodified ANT products and indicate a site of action for the chemicals.
authors.affiliation: Department of Ophthalmology, LSU Eye Center, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112-2234, USA. amalla@lsuhsc.edu
authors.forename: Ali
authors.initials: A
authors.lastname: Mallakin
authors.forename: T Sudhakar
authors.initials: TS
authors.lastname: Babu
authors.forename: D George
authors.initials: DG
authors.lastname: Dixon
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Greenberg
mesh_terms: D000873:Anthracenes / Q000737:chemistry / Q000633:toxicity*; D029064:Araceae / Q000502:physiology*; D004579:Electron Transport / Q000187:drug effects*; D010084:Oxidation-Reduction; D010777:Photochemistry; D010788:Photosynthesis / Q000187:drug effects*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D000873:Anthracenes; D014874:Water Pollutants, Chemical; C034020:anthracene