Different dominant atmospheric nitrogen species coincide with contrasting physiological responses of Hypogymnia physodes (L.) Nyl. transplanted to rural and urban areas.

Different dominant atmospheric nitrogen species induce contrasting physiological responses in Hypogymnia physodes transplanted to urban and rural areas, with nitrate and ammonium levels varying seasonally.

• Why it matters: Understanding how specific nitrogen species affect lichen physiology is crucial for accurate air quality assessment, as total nitrogen load alone does not capture the complexity of pollution impacts.
• What they did: The study analyzed 4 key physiological parameters—photosystem II efficiency, lipid peroxidation, dehydrogenase activity, and nitrogen accumulation—in transplanted lichens across seasons, comparing urban and rural environments.
• The result: Findings reveal that urban environments promote nitrate accumulation and reduced photosynthetic efficiency in winter, while rural sites lead to higher oxidative stress and ammonium buildup, highlighting the importance of considering nitrogen species and environmental context in bioindicators.