Comparison of N-ethyl-N-nitrosourea Effects in three strains of chlorococcal algae

Three strains of three different species of chlorococcal algae(Chlorella kesslerii Scenedesmus quadricauda andScenedesmus obliquus) were compared in their physiological and genetical responses to N-ethyl-N-nitrosourea (NEU). The mutagen was applied in the basic doses corresponding to their specific tolerance to it. Exponentially-graded doses derived from the basic ones acted for the same period of time and single basic doses acted at linearly-increased periods of time in parallel experiments. The influence of the mutagen on the cell cycle just in progress was characterized by the increase in the frequency of cell divisions which yielded a lower number of autospores. The conditions of the cells during the first three days after treatment were determined according to the average increase of their lag phase. The relative toxicity of the mutagen was expressed as the survival frequencies. The mutation effects were evaluated according to the frequency of permanent changes observed in the growing cell colonies : lethal, morphological and pigmentation. NEU was found to be a relatively suitable mutagen for the chlorococcal algae studied.