Types of herbicide resistance
Herbicide resistance is defined as a weed's ability to survive application of a herbicide that would normally be lethal. It's a result of a natural resistance within a weed. What causes this natural resistance is not known, although scientists have identified some of factors.
Target site resistance is the main type of herbicide resistance. Target sites are locations within a weed where the active ingredients in herbicides bind and interfere with physiological processes. Often, a target site is an enzyme or protein that helps a weed grow or reproduce. Once a herbicide binds to a target site, the target site can no longer function properly and the weed eventually dies.
Non-target site resistance is often referred to as metabolic resistance. To control weeds, herbicides must first penetrate the plants - generally through leaf surfaces or root systems - and then move to the target sites. Metabolic resistance prevents herbicides from reaching their target sites by reducing herbicide absorption or translocation, detoxifying a herbicide's active ingredient, "storing" the herbicide in a cellular site that is not vulnerable to the active ingredient or repairing damaged tissue.
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