The effect of cadmium ions on the cell cycle of the green flagellate Chlamydomonas noctigama

Abstract

Using synchronous cultures, the effect of different concentrations of cadmium ions on the growth and reproductive processes, both in the nucleocytoplasmic and chloro- plast compartrnent of the cells of the tlagellate Chlamydomonas noctigama was studied. A loss of motility of cells was the first striking effect of cadmium. The concentrations of metalless than 20 !.lM had insignificant effect on the growth whereas at concentrations higher than 100 !.lM cell growth was completely blocked. With increasing concentration of cadmium ions, the number of commitment points in the cel I cycle decreased and dis- tance between them prolonged. The growth ofthe cells was slowed down and the cel I cy- cle prolonged proportionally to the concentration of cadmium ions except of 5 !.lM which shorten the cell cycle. With exception of cytokinesis, the course of reproductive processes was not affected in the presence of cadmium ions. The formation of daughter cells at high- er ion concentrations was irregular or blocked. In the chloroplast compartrnent, presence of cadmium ions caused destruction of chloroplasts and DNA-containing structures (nu- cleoids).