Effect of metal, hydrogen peroxide and light fluence on cellular growth. Four fold serial dilutions of mid log phase liquid cultures were spotted onto BG11 plates with or without the indicated agents, incubated for 4–5 days and scanned (Methods). Panel A: Typical influence of iron ((NH4)FeH2C6H5O7 or FeCl3), cobalt (Co(NO3)2) and citrate ((NH4)2H2C6H5O7) on the toxicity of cadmium (CdSO4). Panel B: Typical influence of iron ((NH4)FeH2C6H5O7) on the toxicity of hydrogen peroxide (H2O2). Panel C: Influence of the light fluence on the toxicity of CdSO4. These experiments were repeated three times.