Leaf water status and contrasting physiological response profiles of urban Echinacea purpurea in Budapest

We examined whether leaf water status, stomatal traits, and biochemical markers followed a common site ranking or formed contrasting response profiles in three public-space stands of Echinacea purpurea ‘Prairie Splendor’ in Budapest, Hungary. The stands occupied a roadside bed at the edge of Vérmező Park, the paved transport hub at Baross Square, and a bed within Pope John Paul II Square park. Microclimate was recorded on 24–26 July 2025, and leaves were sampled on 26 July. Vapour pressure deficit (VPD) and relative water content (RWC) were interpreted alongside stomatal traits, antioxidant-enzyme activities, proline, pigments, and extractable protein. One composite soil sample per site characterised soil chemistry, enzyme activities, and microbiological profiles. At Baross Square, lower mean VPD (1.89 kPa) accompanied a mean RWC of 98.36%. Mean RWC was 97.29% at Attila Street under greater atmospheric drying demand and 84.64% at Pope John Paul II Square, although the latter two sites had nearly identical maximum VPD. The Attila Street profile included shorter, denser stomata, the highest class III peroxidase (POD) and catalase (CAT) activities, and the highest mean proline content. Pope John Paul II Square had the highest mean pigment and extractable-protein contents on a fresh-weight basis. Total superoxide dismutase (SOD) activity and the air pollution tolerance index (APTI) showed no significant site differences, while individual APTI components varied. The descriptive soil profiles distinguished Attila Street, where higher relative organic-matter and phosphorus fractions, microbial respiration, fungal abundance, and functional microbial groups accompanied high RWC. Leaf water status, stomatal traits, and biochemical markers did not share a common site ranking. Their contrasting combinations indicate that leaf hydration alone only partly characterises the physiological state of these urban stands.