Raman spectroscopy resolves nitrogen-driven metabolic acclimation to urban air pollution in Quercus ilex.

Abstract

Urban air pollution may alter plant metabolism long before visible damage becomes apparent. Raman spectroscopy was evaluated as a rapid, non-destructive approach to resolve these biochemical adjustments. Mature Quercus ilex L. trees were sampled along a well-defined pollution gradient in Tuscany (Italy), spanning high, intermediate, and low levels of NO₂ and PM₁₀. Leaf Raman spectra revealed coordinated modulation of primary and secondary metabolism. Pigment-related bands (chlorophylls and carotenoids) increased toward the most polluted site, while inducible flavonoid signals showed site-dependent variation consistent with oxidative pressure in superficial tissues. These patterns were consistent with destructive biochemical analyses and chlorophyll fluorescence measurements, which indicated acclimation rather than photoinhibition damage. A composite Raman index showed a close site-level association with NO₂ exposure, suggesting that nitrogen-related urban pollution was the main exposure component linked to the observed metabolic response. Overall, Raman spectroscopy captures the chronic metabolic imprint of urban air pollution in Q. ilex, resolving coordinated pigment reinforcement and defensive activation without sample destruction. This approach provides a rapid and scalable framework for linking atmospheric chemistry to plant functional status in biomonitoring applications.

Plant phenotyping relevance

植物の代謝・機能状態を非破壊的に推定するRaman分光法を評価し、スペクトル指標と生化学・蛍光測定の整合性を検証しているため、手法が中心的です。

Code and data availability

The paper reports Raman-spectroscopy phenotyping of Quercus ilex leaves (spectra, RPRI index, chlorophyll fluorescence, biochemical assays) but provides no public repository deposit, code, or trained model. The only availability statement is an on-request offer of the underlying data; supplementary data are hosted at a

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