Cadmium inhibits epoxidation of diatoxanthin to diadinoxanthin in the xanthophyll cycle of the marine diatom Phaeodactylum tricornutum.

Cd has pleiotropic effects on plant physiology and in particular on photosynthesis. It has not been established yet if Cd alters the functioning of the xanthophyll cycle. To answer this question, an exponentially growing culture of the marine diatom Phaeodactylum tricornutum was incubated with Cd (20 mg/l) for 24 h and irradiated with a light activating the xanthophyll cycle, which in diatoms, consists of the reversible deepoxidation of diadinoxanthin to diatoxanthin. The measurements show that the deepoxidation step is not influenced by Cd. In contrast, the Cd concentration used sharply inhibits the epoxidation of diatoxanthin to diadinoxanthin.