PHYSIOLOGICAL INVESTIGATIONS INTO THE RESISTANCE OF A WILD MUSTARD (SINAPIS-ARVENSIS L) BIOTYPE TO AUXINIC HERBICIDES

Possible mechanism(s) of resistance to auxinic herbicides in wild must ard (Sinapis arvensis L.) were investigated by characterizing response s of susceptible and resistant biotypes to 2,4-D, dicamba or picloram. No differences between biotypes were observed in absorption, transloc ation, or metabolism of foliar-applied radiolabelled herbicides. In co ntrast, the levels of ethylene production varied between biotypes. The susceptible biotype produced twofold and sixfold more ethylene than t he resistant biotype within 4 h and 44 h of herbicide application, res pectively. These results suggest that the mechanism of resistance in w ild mustard is not due to differences in absorption, translocation, or metabolism. Ethylene production studies imply that resistance to auxi nic herbicides may be attributed to altered target site(s) of action.