The effect of illumination on the pigment composition of the zeta-carotenic mutant, PG1, of Scenedesmus obliquus.

Dark grown Scenedesmus obliquus strain PG1 accumulated zeta-carotene and phytoene as its major carotenoids. On illumination of dark-grown cultures in air/CO2, cyclic carotenes and xanthophylls were formed, apparently at the expense of the accumulated phytoene and zeta-carotene. This interconversion of carotenoids was accompanied by chlorophyll synthesis. In an atmosphere of nitrogen/CO2 the light-induced changes occurred more slowly and in nitrogen alone the changes were incomplete. No massive production of cyclic carotenes from the accumulated zeta-carotene was observed in cultures illuminated under anaerobic conditions.