Interference of Dimethazone with Formation of Terpenoid Compounds

Abstract

Dimethazone is a bleaching herbicide without any peroxidative activity. In addition to the inhibition of chlorophylls, carotenes, and xanthophylls, decreased formation of other prenyl lipids (phytol and a-tocopherol) can be observed in the presence of dimethazone. Application of this herbicide to pea plants results in the inhibition of longitudinal growth of the newly formed internodes which can be reversed by gibberellic acid. Apparently, dimethazone also decreases the endogenous gibberellin levels. As the formation of all the compounds assayed is inhibited to the same extent and as I50 -values for chlorophyll and carotenoid biosynthesis are identical (about 10 μm dimethazone), the various effects of dimethazone are explained by a single enzyme target in the terpenoid biosynthetic pathway between acetate and geranylgeranyl pyrophosphate. © 1986, Verlag der Zeitschrift für Naturforschung