Overview and Objectives
Herbicides are effective because they each target a specific metabolic pathway in plants. In order for a herbicide to kill a plant, it must first be absorbed by the plant’s leaves or roots. Once the herbicide is absorbed, it will enter a cell which possesses the metabolic pathway the herbicide was designed to target. This lesson follows the fate of the herbicide after it has entered the plant via leaf or root tissue, and explains the factors controlling transport of a herbicide into plant cells. This lesson describes 1) the barriers to herbicide entry, such as the plant cell membrane, 2) the role that the herbicide’s chemical properties have on the rate of cellular absorption, and 3) experimental approaches to understanding herbicide absorption at the cellular level.
At the completion of this lesson, students will be able to:
- Define lipophilicity and hydrophilicity;
- Compare and contrast passive and active transport across membranes;
- Identify the factors controlling herbicide transport across membranes;
- Explain ion trapping of weak acids; and
- Identify experimental approaches to characterizing modes of herbicide transport across membranes.
Development of this lesson was supported in part by the Cooperative State Research, Education, & Extension Service, U.S. Dept of Agriculture under Agreement Number PX2003-06237 administered by Cornell University, Virginia Tech and the American Distance Education Consortium (ADEC) and in part by the New Mexico and Nebraska Agricultural Experiment Stations. 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.