“…According to a number of workers (Gaffron and Rubin 1942, Gingras et al 1963, Hartmann and Krasna 1962 the hydrogenase of Scenedesmus exhibits its activity only after a dark period in the absence of O,. However, it was also reported that in media containing boiled carrot extracts, cells of Scenedesmus (Chiba andSasaki 1963, Stiller andLee 1964) and Chlorella (Stiller and Lee 1964) develop active hydrogenase without dark anaerobic adaptation. This effect was enhanced by glucose, indicating a possible correlation between respiration and hydrogenase adaptation.…”