Environmental stress can increase the risk of injury to desirable plants from herbicides.

• A. True
• B. False
• C. Not specified
• D. Sometimes

Answer: (A)

Environmental stress changes how plants respond to herbicides, making injury more likely. When a desirable plant is under stress from drought, heat, cold, or nutrient deficiencies, its physiology shifts in ways that can increase herbicide impact. Stress can weaken cell membranes and cuticle barriers, allowing foliar herbicides to enter more easily. It can slow or alter detoxification pathways the plant normally uses to break down and sequester chemicals, so the herbicide remains active longer in the tissue. Translocation patterns can also change, moving the chemical to sensitive areas where it causes more damage. In some cases, stress conditions amplify phototoxic effects or other modes of action, especially for herbicides that rely on light or specific metabolic activities. Soil- applied herbicides may be taken up more readily by stressed roots, further increasing exposure. Because these factors raise the likelihood of injury to crops or desirable plants, the statement is true.