Absorption, Translocation and Metabolism of Dichlobenil in Bean Seedlings

Abstract

Summary. A quantitative study was carried out on the absorption, translocation and metabolism of 2,6–dichlorobenzonitriie‐14G (dichlobenil) in seedlings of Phaseolus vulgaris L. From an aqueous solution dichlobenil is absorbed by the roots and accumulates about three‐fold; metabolism in the roots is of minor importance. From the roots the herbicide is translocated throughout the plant. In the leaves two competitive processes take place: the main part (90%) of the dichlobenil evaporates and another part is metabolized. The principal metabolic pathway is hydroxylation, followed by conjugation, 3–hydroxy‐2,6–clichlorobenzonitriIe and 4–hydroxy‐2,6–dichlorobenzonitrile analogues being formed in a ratio of about 4:1. Hydrolysis of dichlobenil into 2.6–dichlorobenzamide and 2,6–dichlorobcnzoic acid is only a minor metabolic route. From a saturated atmosphere dichlobenil is taken up rapidly through the leaves but little translocation occurs to the roots. Following foliage application more of the applied dichlobenil Is metabolized because evaporation of dichiobenil as a competitive process is virtually eliminated. Absorption, migration ei métabolisme du dichlobenil dans les plantules de haricot

High peroxidase activity and stable changes in the cell wall are related to dichlobenil tolerance

“…Peroxidases could also play a direct role in dichlobenil detoxification through its oxidization to 3-and 4-hydroxy derivatives, which would subsequently form non-active sugar conjugates (Verloop and Nimmo, 1970). Further oxidation of dichlobenil hydroxylated metabolites would produce radicals, which might also be rendered inactive by non-enzymatic polymerization (Agostini et al, 2003).…”

Metabolism of dichlobenil by microorganisms in the aquatic environment

“…Verloop and Nimmo (1969) also reported that dichlobenil was degraded by soil microorganisms. However, their conclusion was an indirect one since it was based on the absence of degradation in sterilized soil.…”

The relationship of metabolism studies to the modes of action of herbicides

“…Dichlobenil (2,6-dichlorobenzonitrile) is also a highly volatile herbicide applied to soil or water and behaves primarily as a growth inhibitor, acting on the meristems. Its mode of action has been examined in bean seedlings by Verloop and Nimmo,20 in wheat and rice seedlings,21 and in selected aquatic species by Mottley and Kirkwood.22 These studies show that dichlobenil is absorbed by the roots and translocated to the leaves where a large portion may be lost by volatilisation. Metabolism studies show that in bean leaves, hydroxylation occurs with the formation of the 3-and 4-hydroxy derivatives which subsequently form conjugates.…”