Chlorophyll a fluorescence: a tool for the investigation of toxic effects in the photosynthetic apparatus.

The effects of environmental pollutants, such as triazines, urea herbicides, phenols, nitro aromatic compounds, aldehydes, hydrogen sulfide, volatile halogenated aliphatic and aromatic compounds, and alkylbenzenes, the photosynthesis of green algae were investigated by using detailed analysis of chlorophyll a fluorescence. Application of quenching analysis by means of a pulse amplitude-modulated fluorometer allows the discrimination of different modes of action. Blocks of the electron-transport chain, the action of uncouplers, and fluorescence quenching by nitroaormatic compounds could be distinguished. Hydrogen sulfide and short-chain aldehydes seem to react in the same way, probably by reaction with components of the electron-transport chain. Nonreactive volatile compounds affect chlorophyll fluorescence in a strictly hydrophobicity-dependent manner. The quenching analysis suggests an inhibition of utilization of proton-motive force for ATP synthesis. Detailed analysis of fluorescence patterns may be of great help for identification of toxic pollutants and their sources.