The effect of lead on photosynthesis, as determined by photoacoustics in Synechococcus leopoliensis (Cyanobacteria)

The effect of lead on photosynthetic light storage efficiency was measured by the photoacoustic method. The advantage of this method is in its directness, since the signal obtained by a hydrophone is proportional to that fraction of light energy that is dissipated as heat. This increases as less energy is stored photochemically if the photosynthetic apparatus is damaged. Cells of Synechococcus leopoliensis (Cyanobacteria) were grown in medium containing lead in concentrations of 0, 25, 50, 100, and 200 ppm. To avoid the co-precipitation of lead and phosphorus as lead phosphate, phosphorus was omitted from the media used during weeklong exposure to lead. Both chlorophyll concentration and photosynthetic energy storage efficiency decreased with time and with lead concentration. Reduction of photosynthesis progressed with time and increased with lead concentration, reaching up to 80% at the highest lead concentration after seven days.