Agronomy and Horticulture Department



Metabolism of Herbicides or Xenobiotics in Plants

Date of this Version


Document Type



Plant and Soil Sciences eLibrary (PASSeL) Lesson

A contribution of the University of Nebraska Cooperative Extension, Lincoln NE 68583, Journal Series No. 1019


Copyright © 2006 Tracy M. Sterling, Deana Namuth, and Ismael Hernández-Rios. Used by permission.

JNRLSE approved 2006

This project was supported in part by the National Research Initiative Competitive Grants CAP project 2011-68002-30029 from the USDA National Institute of Food and Agriculture, administered by the University of California-Davis and by the National Science Foundation (NSF), Division of Undergraduate Education, National SMETE Digital Library Program, Award #0938034, administered by the University of Nebraska. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the USDA or NSF.

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 authors and do not necessarily reflect the view of the U.S. Department of Agriculture.


This lesson will take an in depth view of how plants handle foreign chemicals (xenobiotics) such as herbicides. It will discuss the three main phases that plants use to handle toxic chemicals, which enzymes are involved in these biochemical conversions, how these processes help protect crops again phytotoxic chemicals and consider the importance of these processes to successful weed management.


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.