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<p>Urbanization has exacerbated air pollution globally, with vehicular traffic emerging as a major contributor. Plants serve as cost-effective and environmentally friendly biomonitors, and their tolerance can be evaluated using the air pollution tolerance index. This study assessed the physiological responses and air pollution tolerance of <i>Cedrus libani</i>, <i>Pinus nigra</i>, and <i>Juniperus excelsa</i> across three study sites with varying pollution levels. For this purpose, physiological traits, including total chlorophyll, carotenoids, ascorbic acid, relative water content, leaf pH, and membrane stability index, were measured, and air pollution tolerance index was calculated. ANOVA and Duncan’s test were used to identify interspecific differences, while correlation analysis and principal component analysis revealed trait relationships. Across the pollution gradient, total chlorophyll, carotenoids, leaf pH, and membrane stability index decreased, while ascorbic acid, relative water content, and APTI increased, indicating stress-induced physiological adjustments. Among the studied species, <i>C. libani</i> and J<i>. excelsa</i> exhibited moderate tolerance, whereas <i>P. nigra</i> was more sensitive to air pollution. Correlation analysis revealed site-specific patterns, with APTI showing strong positive associations with ascorbic acid and membrane stability index at the control site, with total chlorophyll and pH at the lightly polluted site, and with ascorbic acid, carotenoids, pH, and membrane stability index under high pollution conditions. Principal component analysis explained 69.09% of the variance, separating pigment-related traits (chlorophyll, carotenoids, pH) from stress tolerance traits (ascorbic acid, membrane stability index, air pollution tolerance index, partially relative water content). Species-specific distributions highlighted distinct adaptation strategies, with <i>J. excelsa</i> clustering with tolerance indicators, <i>C. libani</i> at polluted sites aligning with ascorbic acid, and <i>P. nigra</i> showing weaker associations under stress. Overall, ascorbic acid emerged as the most decisive trait influencing air pollution tolerance index, emphasizing the role of antioxidant mechanisms in pollution tolerance. These findings suggest that <i>C. libani</i> and <i>J. excelsa</i> are more suitable for urban greening in polluted environments, while <i>P. nigra</i> may serve as a sensitive bioindicator.</p>

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Physiological Responses of Three Urban Needle-Leaved Tree Species to Traffic-Related Air Pollution

  • 期刊论文

  • 发表日期：

    2025年11月11日

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  • Mazlum Erol,
  • Nuray Cicek,
  • Cengiz Yucedag

摘要

Urbanization has exacerbated air pollution globally, with vehicular traffic emerging as a major contributor. Plants serve as cost-effective and environmentally friendly biomonitors, and their tolerance can be evaluated using the air pollution tolerance index. This study assessed the physiological responses and air pollution tolerance of Cedrus libani, Pinus nigra, and Juniperus excelsa across three study sites with varying pollution levels. For this purpose, physiological traits, including total chlorophyll, carotenoids, ascorbic acid, relative water content, leaf pH, and membrane stability index, were measured, and air pollution tolerance index was calculated. ANOVA and Duncan’s test were used to identify interspecific differences, while correlation analysis and principal component analysis revealed trait relationships. Across the pollution gradient, total chlorophyll, carotenoids, leaf pH, and membrane stability index decreased, while ascorbic acid, relative water content, and APTI increased, indicating stress-induced physiological adjustments. Among the studied species, C. libani and J. excelsa exhibited moderate tolerance, whereas P. nigra was more sensitive to air pollution. Correlation analysis revealed site-specific patterns, with APTI showing strong positive associations with ascorbic acid and membrane stability index at the control site, with total chlorophyll and pH at the lightly polluted site, and with ascorbic acid, carotenoids, pH, and membrane stability index under high pollution conditions. Principal component analysis explained 69.09% of the variance, separating pigment-related traits (chlorophyll, carotenoids, pH) from stress tolerance traits (ascorbic acid, membrane stability index, air pollution tolerance index, partially relative water content). Species-specific distributions highlighted distinct adaptation strategies, with J. excelsa clustering with tolerance indicators, C. libani at polluted sites aligning with ascorbic acid, and P. nigra showing weaker associations under stress. Overall, ascorbic acid emerged as the most decisive trait influencing air pollution tolerance index, emphasizing the role of antioxidant mechanisms in pollution tolerance. These findings suggest that C. libani and J. excelsa are more suitable for urban greening in polluted environments, while P. nigra may serve as a sensitive bioindicator.