What indicates a possible nitrogen oxide impact on plants?

The presence of bronze or copper-colored necrosis of leaves is a significant indicator of potential nitrogen oxide impact on plants. Nitrogen oxides can lead to oxidative stress within plant tissues, resulting in leaf damage characterized by these distinctive discolorations. The necrosis reflects the cellular damage caused by reactive oxygen species generated under the influence of nitrogen oxides. This symptom often appears as the leaves develop a bronzed or copper hue accompanied by tissue death, which can severely affect the overall health and productivity of the plant.

The other options, while indicative of different plant stress factors or diseases, do not specifically point to nitrogen oxide exposure. Stunted foliage growth, for example, can stem from a variety of nutrient deficiencies or pathogens unrelated to nitrogen oxides. Knotty stems may suggest physical damage or a different type of plant disease, and beautiful flowering is typically a sign of healthy plant growth and nutrition, not an indication of nitrogen oxide impact.