Vicia-faba - Sister chromatid exchanges of the organophosphorus insecticides methyl parathion, dimethoate, oxydemeton methyl, azinphos methyl and phoxim.

Vicia faba root tips were treated for two hours with several concentrations of the organophosphorus insecticides methyl parathion, dimethoate, oxydemeton methyl, azinphos methyl and phoxim, after one incroporation cycle with 5-bromodeoxyuridine (5-BrdUrd). Afterwards, the roots were exposed to a second replication cycle with 5-BrdUrd. The differential stain technique described by Tempelaar et al. (1982) with some modifications was used. The results showed that the two insecticides which are the most effective inducers of SCE are methyl parathion and phoxim.In no case was a concentration-response relationship observed. The treatments (except with dimethoate 0.5 ppm) produced SCE frequencies which differed significantly from those of the control.