Traffic-Related Heavy Metal Stress in the Medicinal Plant Plantago lanceolata L.

Ensuring the safety of sustainably managed medicinal plants is closely linked to the quality of plant raw materials, including the presence of heavy metals within safe limits. Sustainable management in the context of herbal raw materials therefore entails responsible management of herbal plant resources, integrating environmental protection with ensuring long-term economic profitability. The aim of this study was to analyze selected biochemical parameters and to determine metal concentrations in soils and leaves of Plantago lanceolata L. collected from natural habitats at increasing distances from traffic routes. The content of Zn, Cu, Ni, and Pb was determined in the soils and leaves of Plantago lanceolata L. Assessing the content of these elements in plant raw materials allows for: the prevention of harmful substances in final products, adaptation of raw materials to applicable safety standards (avoiding toxicity), and protection of consumer health. This promotes sustainable development by building a safe supply chain. The leaves of Plantago lanceolata L. were also tested for biochemical enzymatic (catalase (CAT) and superoxide dismutase (SOD)) and non-enzymatic (chlorophyll a and b (Chl a and b), carotenoids (Car), ascorbic acid (AAC)), and mechanisms regulating the activity of reactive oxygen species (ROS) were determined in the leaves of Plantago lanceolata L. Based on the results of leaf pH, relative water content (RWC), ascorbic acid content, and total chlorophyll content, the air pollution tolerance index (APTI) was calculated. The distance from the road has a significant impact on the concentration of the heavy metals analyzed. The soils were found to be free of Zn, Cu, Pb, and Ni contamination. However, analysis of Plantago lanceolata L. leaves revealed exceedances of acceptable lead limits for herbal plants. The content of pigments, the ratio of Chl a/b, and Chl (a + b)/Car in the leaves of Plantago lanceolata L. was significantly dependent on the distance from the road. The activity of CAT and SOD in the leaves of Plantago lanceolata L. growing closest to the road was significantly higher compared to the others. APTI values suggest that Plantago lanceolata L. exhibits sensitivity to pollution, independent of its distance from the emission source.