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Lesson Outline Overview and Objectives Introduction Membrane Review Passive Absorption — Some General Concepts Passive Absorption — Looking at Effects of Charge Passive Absorption — Ion Trapping and Accumulation Benefits of Accumulation via Ion Trapping Passive Absorption — Additional Accumulation Mechanisms Passive Absorption Summary Active Absorption — General Concepts Active Absorption — Three Herbicide Examples Active Absorption Summary Lesson Summary Lesson Media Objects Herbicide Uptake by Leaves and Cells Ionization, pH, and pKa processes

Cellular Absorption of Herbicides Rate Me 1 2 3 4 5 Passive Absorption Summary Prior to herbicides reaching their sites of action and killing the plant, they must first enter the plant cell where that site of action resides. Most herbicides are able to enter a plant cell by passing through the cell membrane, as driven by their concentration gradient (termed passive diffusion), a process that requires no energy. Even though most herbicides are passively absorbed, some herbicides are able to accumulate in the alkaline cytosol to concentrations greater than outside the cell, because of ion trapping. In addition to ion trapping, the processes of metabolism and binding to cell walls or lipids can also increase the concentration of the herbicide in the cell. However, in these cases, the herbicides are usually rendered non-toxic. Comments Be the first to write a comment... Add Comment

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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, adminstered 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 author(s) and do not necessarily reflect the views of the USDA or NSF.
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