Herbicidal Inhibition of Carotenogenesis Detected by HPLC

The target sites o f three herbicides which inhibit carotenoid biosynthesis have been charac­ terized using H PLC analysis o f pigm ent extracts from two higher plant systems, carro t cell suspension cultures and barley seedlings. Diflufenican causes an accum ulation o f phytoene and phytofluene. D ichlorm ate causes accum ulation o f phytoene, phytofluene, ^-carotene, neurosporene and ß-zeacarotene. A m itrole causes accum ulation of phytoene, phytofluene, yand 5-carotenes and lycopene. Significant differences in the geometric and hydroxylated natures o f the accum ulated precursors occurred between the carro t cell and darkand lightgrown barley. These differences are discussed with respect to both the target sites o f the three carotenogenic herbicides and the biosynthetic pathw ay leading to carotenoid biosynthesis in higher plants.