Illinois Field Crop Applicators Practice Test

The mode of action of a herbicide refers to what aspect?

1. How the herbicide is absorbed

2. How it inhibits plant growth

3. The environmental impact

4. The application method

The correct answer is: How it inhibits plant growth

The mode of action of a herbicide specifically refers to the mechanism by which it inhibits plant growth. This includes understanding how the herbicide affects biochemical processes within the plant, leading to growth inhibition or plant death. For instance, some herbicides disrupt photosynthesis, while others interfere with hormone balance or inhibit seed germination by targeting specific enzymes or metabolic pathways. In contrast, while absorption is important for a herbicide's effectiveness, it pertains more to the pharmacokinetics of how the chemical enters the plant rather than its mode of action. The environmental impact relates to how the herbicide affects non-target organisms and ecosystems, which is a separate consideration from how it specifically influences plant physiology. Lastly, the application method refers to how the herbicide is applied (e.g., spraying, granules), which is operational rather than explaining the chemical's action within the plant.