Abstract— It has been shown that green cells of Euglena gracilis accumulate under red light. The action spectrum of this response has been determined. Its shape and the results of regreening experiments clearly indicate a role of chlorophyll. The quenching effect of chlorophenyl–dimethylurea and NH2OH demonstrate that this cell accumulation is not directly light‐induced, as in the case of phototaxis, but is due to an effect of oxygen, the evolution of which is stimulated by light.
SummaryAn apparatus for the cultivation of microorganism under controlled conditions is described. This apparatus is basically a turbidostat improved with automatic devices for sample withdrawal and tube cleaning. The results of experiments, using Euglena graciZis to check the constancy of some physiological parameters (in particular phototactic reactivity), are reported.
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