Exploring the Effects of Vehicle-Related Air Pollution on the Photosynthetic and Biochemical Traits of <i>Cupressus macrocarpa</i> cv. "Goldcrest"

The utilization of plant species as bio-indicators for monitoring air pollutants and trace elements has been widely explored; however, limited research has focused on their photosynthetic responses and the development of air pollution tolerance indices (APTI) based on biochemical traits. This study investigates the photosynthetic and biochemical responses of Cupressus macrocarpa cv. 'Goldcrest' (Lemon cypress) to air pollution and establishes an APTI using these parameters. Leaf samples were collected from five trees located in both a control site (Burdur Mehmet Akif Ersoy University Campus) and a polluted site (Burdur city center) in Turkey. A total of 60 leaves were analyzed for chlorophyll a, chlorophyll b, total chlorophyll, ascorbic acid, relative water content, and pH. Significant differences (p < 0.05) were observed between the two sites, with chlorophyll b showing the highest reduction (25%) in the polluted area. The APTI showed strong correlations with relative water content in the control site and pH in the polluted site. Principal Component Analysis (PCA) clearly distinguished the control and polluted samples. The findings indicate that C. macrocarpa cv. 'Goldcrest' is a reliable bio-indicator for urban air pollution and a suitable candidate for sustainable urban tree planting in moderately polluted environments.