Figure 2

Microphotographs of eight-celled coenobia of the wild type and Se resistant strains of Scenedesmus quadricauda treated with selenium. Coenobia observed in DIC (A, B, D, E) or in a fluorescence microscope (C, F). A: daughter untreated cells in octuplet coenobium; B: cells treated with selenite 50 mg Se × l^-1, malformations of the cells and an abnormal number of spines (see arrows) are apparent; C: cells treated with selenite 100 mg Se × l^-1, only one large bright cell from the coenobium was viable but not dividing, five small half-bright cells were growing poorly and two dark cells were dead. D, E, F: the cells in octuplet coenobium at the stage of protoplast division, D: selenate resistant strain SeVI treated with selenate 100 mg Se × l^-1, E: selenite/selenate resistant strain SeIV+VI treated with selenite+selenate (50+50 mg Se × l^-1), F: selenite resistant strain SeIV treated with selenite 100 mg Se × l^-1, bars: 10 μm.