The mutant strain of Chlorella (strain 5/520) recently described synthesizes wild type carotenoids in light only. When the dark grown mutant is transferred into light, synthesis of α- and β-carotene proceeds as well in the absence as in the presence of O2, whereas synthesis of xanthophylls is dependent on light and molecular O2 2, 3. The experiments described below indicate that 1. the final oxydative steps of the light dependent xanthophyll synthesis of Chlorella are in fact dark reactions following light reactions, the latter occurring also in N2; 2. immediate precursors of xanthophylls are accumulated anaerobically in light which in the presence of molecular O2 can be oxydised to xanthophylls in the dark; 3. Xanthophyll synthesis in the dark is always accompanied by a strictly corresponding decrease of α- and β-carotene accumulated in the previous light period. This would indicate that α- and β-carotene are the immediate precursors of xanthophylls in green cells.

Claes, H. (1959). Biosynthese von Carotinoiden bei Chlorella. Zeitschrift Für Naturforschung B, 14(1), 4–7.