Which signs are common indicators of herbicide injury on plants?

The common indicators of herbicide injury on plants are visible symptoms such as wilting, curling, yellowing, and necrosis of leaves. These symptoms result from the toxic effects of herbicides on plant tissues. Herbicides are designed to disrupt specific physiological processes within plants; for example, they might interfere with photosynthesis or disrupt cell division.

When plants experience herbicide injury, the stress manifests as wilting due to loss of turgor pressure, curling or distortion of leaves because of abnormal growth patterns, yellowing (known as chlorosis) due to impaired chlorophyll production, and necrosis, which is the death of plant tissue. These signs are reliable indicators for diagnosing potential herbicide exposure and can help in determining the appropriate management practices to mitigate further damage or to avoid future occurrences.

In contrast to this, the other options suggest growth enhancements or traits that do not align with herbicide injury, such as thickened stems or increased flowering, which would not be expected results from herbicide exposure. Thus, the identification of wilting, curling, yellowing, and necrosis as symptoms distinguishes them as clear signs of herbicide injury.