Evaluation of the mechanism of action of the bleaching herbicide SC-0051 by HPLC analysis

Abstract The accumulation of leaf pigments in soybean [ Glycine max (L.) Merr. cv. Essex] plants treated with the bleaching herbicides norflurazon (20 ppm, w w ) and SC-0051 (2.5 ppm, w w ) was investigated by means of high-performance liquid chromatography analysis. SC-0051 is a new experimental herbicide whose chemistry has not been released. Both SC-0051 and norflurazon reduced the relative concentrations of xanthophylls, chlorophylls, and colored carotenoids and induced the accumulation of the colorless carotene, phytoene, in the leaves of treated soybeans. These results confirm that the mechanism of the bleaching action of the herbicide SC-0051 is similar to that of norflurazon and includes the inhibition of the desaturation reactions of carotenoid biosynthesis. In addition to their phytoene-accumulating activity, both SC-0051 and norflurazon induced the accumulation of an additional pigment which was not present in leaf extracts obtained from untreated soybeans. Although the exact identity of this pigment is unknown, it appears to be a derivative of phytoene.