The Appearance of Neoxanthin during the Regreening of Dark-grown Euglena

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Abstract
Dark-grown Euglena gracilis var. bacillaris which contain no chlorophyll and are unable to carry out photosynthetic reactions, have now been shown to contain only 7% of the carotenoids present in light-grown controls. Neoxanthin, which comprises 5% of the total carotenoids in the control cultures, is completely lacking in the dark-grown cultures. When dark-growing cultures in a resting medium are exposed to white light, carotenoid synthesis begins immediately with the exception of neoxanthin which shows a 4-hour lag before its synthesis begins. The 4-hour period corresponds to the lag reported for the 1st appearance and development of photosynthetic competence in similar cultures. This indicates that neoxanthin synthesis parallels the development of the photosynthetic apparatus in regreening E. gracilis.