Changes in Carotenoid Composition and Function of the Photosynthetic Apparatus during Light‐dependent Chloroplast Differentiation in Mutant C‐6D of Scenedesmus obliquus*

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Abstract
Changes in pigment composition during light‐dependent chloroplast differentiation in mutant C‐6D of Scenedesmus obliquus were followed by HPLC. The system used enables the separation and quantitative determination of five xanthophylls (neoxanthin, violaxanthin, antheraxanthin, lutein and zeaxanthin), α‐ and β‐carotene and chlorophyll a and b (and their epimeric forms).Dark‐grown cells of the mutant contain only chlorophyll a, traces of chlorophyll b and acyclic precursors of carotenoids. During subsequent illumination, precursors decrease and high amounts of xanthophylls, carotenes and chlorophyll a and b are formed.Dark‐grown cultures of mutant C‐6D show high photosystem I‐activity and contain the photosystem I‐complex CP I, but lack photosystem II‐activity, the photosystem II‐complex CPa and the LHCP. Immediately after transfer to light, photosystem II‐activity increases rapidly, as also do the amounts of CPa and lutein. Under anaerobiosis no lutein and PS II‐activity can be detected. This indicates a role of lutein in the assembly of an active photosystem II‐complex. All other xanthophylls and the LHCP exhibit high rates of synthesis only after a delay of about 1 hour. Thus, our results reveal an asynchronous fashion of formation of CPa and LHCP.