Accumulation of Colorless Carotenes and Derivatives during Interaction of Bleaching Herbicides with Phytoene Desaturation

Colorless carotenoids were accum ulated, analyzed and quantified in heterotrophicallygrow n Scenedesm us cultures treated with the bleaching herbicide norflurazon. By optical, IR and m ass spectroscopy 15-cis as well as all-trans phytofluene, 15-cis phytoenes and traces o f its all-trans isom er were identified. Furtherm ore, a phytoene epoxyde and several hydroxyphytoenes were assigned. C om paring the concentrations o f these phytoene derivatives in heterotrophic cultures grow n in darkness with those in light-grown au to troph ic cells, an exchange o f phytoene derivatives was observed. Levels o f phytoene were much higher in the dark whereas concentrations o f hydroxyphytoenes dom inated in the light. O ther herbicides like fluridone, diflufenican, and difunon accum ulate the same colorless carotenoids including phytoene epox­ yde and various hydroxyphytoenes. F o r all herbicides an alm ost constan t hydroxyphytoene to phytoene epoxyde ratio was observed indicating an interrelated form ation o f both oxygenated phytoene derivatives which can be influenced by light conditions o f the cultures.