New Herbicidal Inhibitors of Carotene Biosynthesis

Abstract

New herbicidal compounds, CGA 22867, LS 80707, LS 80717, MB 38183, as well as AMO 1618 have been shown to interfere with enzymes of the carotenogenic pathway. Other reactions in the photosynthetic apparatus (i. e., electron transport, peroxidative processes) were not affected. With a cell-free enzyme system from Aphanocapsa, which converts phytoene into β-carotene, it was demonstrated that phytoene desaturase is inhibited by CGA 22867, MB 38183, LS 80707, and LS 80717. Furthermore, the activity of ξ-carotene desaturase was also decreased with LS 80707. The cyclase inhibitor AMO 1618 had an inhibitory effect on lycopene cyclase, the third enzyme in the reaction sequence from phytoene to β-carotene. The inhibitory properties of all of these compounds were rather similar in vitro and in vivo.