The following agents were used for rescue experiments of heavy metals impact on Micrasterias cells: cultures were pre-treated with 20 μM salicylic acid C7H6O3 (SA), 20 μM L-ascorbic acid C6H8O6 (AA), 300 nM reduced l-glutathione C10H17N3O6S (GSH), 100 μM Fe-EDTA (Fe), 300 nM ZnSO4 (Zn) or 1 mM CaSO4 (Ca) for 1 week to allow acclimatization of the cells to the substances. Dividing cells were then collected and incubated for 4 h, or cultures were treated for 21 days with heavy metals and ameliorating substances simultaneously, before the effects were examined. For rescue treatments with gadolinium (Gd), cells from untreated cultures were exposed to 15 μM Cd and 40 μM Pb either together with 3 μM Gd or after 30 min pre-treatment with Gd. All used concentrations of rescue substances were previously determined to have no negative effect on cell development, morphology and photosynthesis when applied to Micrasterias cells alone. Heavy metals and rescue substances were added to the cell cultures only once at the given time points.