Overview and Objectives


Herbicide detoxication via metabolism is the primary mechanism of selectivity for most herbicides. Selective weed control using herbicides often relies on the ability of tolerant crop plants to detoxify the herbicide more rapidly than weeds. The same processes used by plants to detoxify herbicides are used for other xenobiotics (foreign chemicals); therefore, these terms will be used interchangeably. In this lesson, we will explore in detail three major phases of herbicide metabolism in plants, the enzymes involved in those processes and the final fate of herbicide metabolites. In addition, how crop injury or weed sensitivity might be altered by synergists, antagonists or other factors that affect metabolism will be described. Involvement of herbicide metabolism in resistance will also be discussed.


At the completion of this lesson, learners will be able to:

  1. Understand the importance of herbicide metabolism for crop tolerance (selectivity).  
  2. Identify the three major phases of xenobiotic metabolism in plants.  
  3. Explain the major enzyme systems involved during metabolism of xenobiotics in plants.  
  4. Provide examples of each major phase and understand how metabolism may also lead to herbicide bio-activation.
JNRLSE Approved 2006

Development of this lesson was supported in part by the Cooperative State Research, Education, & Extension Service, U.S. Dept of Agriculture under Agreement Number 00-34416-10368 administered by Cornell University and the American Distance Education Consortium (ADEC). Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture. A contribution of the University of Nebraska Cooperative Extension, Lincoln NE 68583, Journal Series No. 1019.