What is an example of a plant response that can indicate environmental stress?

The correct answer highlights that plant symptoms, such as wilting, discoloration, or leaf drop, can serve as indicators of environmental stress. These symptoms often result from factors like drought, nutrient deficiency, pest infestations, or disease, which affect a plant's overall health and well-being. Observing these symptoms helps in diagnosing potential issues the plant may be facing due to its environment.

Although growth inhibition, root curl, and environmental adaptation are also responses that can occur in plants, they do not encompass the broader range of visible indicators that plant symptoms represent. Growth inhibition specifically refers to a decrease in growth rate but does not necessarily convey the various signs observed on the plant. Root curl typically indicates localized stress but may not be as easily recognized as the more general symptoms that can be observed in various parts of the plant. Environmental adaptation, while a crucial response to stress, suggests changes over time rather than immediate signs or symptoms that indicate stress. Therefore, plant symptoms provide a more comprehensive understanding of the signs of environmental stress immediately observable on the plant.