Lesson Media Objects
Cellular Absorption of Herbicides
Active Absorption — General Concepts
Up until now, we have discussed how herbicides can be passively absorbed into plant cells, where their absorption is driven by passive diffusion, and occurs down a concentration gradient. Most herbicides are absorbed in this manner. However, a few are absorbed via mechanisms of active transport, such as 2,4-D, glyphosate and paraquat.
Active transport moves a molecule across a membrane against its concentration gradient. This type of transport usually involves a protein carrier located on the membrane which uses energy to move the herbicide from one side of the membrane to the other. The protein can carry the molecule into the plant cell, increasing its concentration within the cell to levels well above those outside the cell.
We know that charged, hydrophilic herbicides move into plants cells via active transport based on experimental evidence which has shown the following:
Interestingly, out of all the different herbicide chemistries currently available, evidence for active transport of herbicides across plant membranes so far has been shown for only 2,4-D, glyphosate, and paraquat. By following the link for “Active Absorption” in this animation, Herbicide Uptake by Leaves and Cells, you can see this process animated (Figure 10). Details for each of these three herbicides are described in the next topic.
Be the first to write a comment...