Which of the following is NOT a mechanism of herbicide resistance?

Enhanced absorption is not a mechanism of herbicide resistance. Herbicide resistance typically involves alterations that allow a plant to survive applications of herbicides that would otherwise be lethal. Common mechanisms include compartmentalization or sequestration, where a plant isolates the herbicide away from its target site, thereby reducing its effectiveness. Altered target sites occur when the site of action for a herbicide is modified, preventing the herbicide from binding effectively and leading to reduced efficacy. Over-expression of the target protein means that the herbicide's intended target is present in greater amounts than usual, which can also diminish the herbicide's impact.

On the other hand, enhanced absorption refers to a plant's ability to take up more of the herbicide, which would typically make it more susceptible to the herbicide rather than resistant. Therefore, increased absorption does not confer resistance, as it would lead to the opposite effect of what is required for a plant to survive herbicide application.