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Phytotoxicity of m-phenoxybenzamides: Inhibition of cell-free phytoene desaturation

1985; Elsevier BV; Volume: 23; Issue: 3 Linguagem: Inglês

10.1016/0048-3575(85)90094-x

1095-9939

Ian E. Clarke, Gerhard Sandmann, Peter M. Bramley, Peter Böger,

Photosynthetic Processes and Mechanisms

Inhibition of carotenoid biosynthesis by herbicidal m-phenoxybenzamide derivatives has been investigated in a cell-free carotenogenic system from Aphanocapsa. Their target is the phytoenedesaturase reaction. Double-reciprocal plots of β-carotene biosynthesis (from 14C-labeled geranylgeranyl pyrophosphate) showed that 3-(2,5-dimethylphenoxy)-N-ethylbenzamide was a noncompetitive inhibitor of the phytoene-desaturase complex. The Ki value for cell-free inhibition of β-carotene formation was almost identical to the I50 value of intact cells. Furthermore, the influence of certain substituents on herbicidal activity has been investigated. Inhibition increased with the length of the unbranched N-alkyl chains. In addition, substituents at the phenoxy group with higher lipophilicities showed greater inhibitory activities. The presence of a phenoxy or trifluoromethyl moiety at position 3 is essential.