Trifoliin — Rhizobium trifolii interaction and its inhibition by herbicides and their corresponding metabolites

The effect of the phenylurea herbicides linuron, monolinuron, metobromuron, and the phenoxyalkanoic acid herbicides 2,4-D and 2,4,5-T as well as their corresponding aromatic metabolites 3,4-dichloro-, 4-chloro-, 4-bromoaniline, 2,4-dichloro-, and 2,4,5-trichlorophenol on the agglutination of Rhizobium trifolii was tested with a trifoliin containing seed extract of white clover (Trifolium repens).

The herbicides tested did not effect the agglutination up to concentrations as high as their water solubility. However, the chloro-or bromoanilines showed an inhibitory effect on agglutination at concentrations ranging from 16 to 25 mM. 2,4-Dichloro- and 2,4,5-trichlorophenol inhibited the agglutination even in concentrations of 2 and 1 mM, respectively. All metabolites were effective after preincubation of the seed extract, since they damaged the glycoprotein trifoliin. The compounds did not influence the lectin-binding polysaccharide formation at the cell surface. HgCl₂ treated cells, cells harvested in the stationary and log phase or grown in the presence of 0.2 mM 2,4-dichlorophenol and 0.1 mM 2,4,5-trichlorophenol, respectively, agglutinated without any differences in the test system used.