Evaluation of Biochemical and Physiological Parameters of the Leaves of Tree Species Exposed to Vehicular Emissions

Aims: To determine the sensitivity and tolerance levels of the tree species to air pollution using biochemical and physiological parameters.

Study Design: Field and Laboratory Studies

Place and Duration of the Study: Three major roads in Ile-Ife, Institute of Ecology and Environmental Studies Laboratory and Central Science Laboratory, Obafemi Awolowo University, Ile-Ife, Osun State, Southwest, Nigeria.

Methodology: The air pollution tolerance indices (APTI) of twelve dominant plant species found along three major roads in Ile-Ife, Osun State, Southwest Nigeria were studied, with a view to determining their sensitivity to air pollution. Biochemical and physiological parameters such as, relative water content, total chlorophyll, leaf extract pH and ascorbic acid concentration of the leaves of the selected trees were analyzed to determine their APTI.

Results: The lowest pH value was obtained in Spondias mombin (2.75) while Albizia zygia had the highest pH value (5.47). Ascorbic acid concentration of the leaves ranged within 3.14 mg/g and 7.88 mg/g, with the lowest and highest value recorded in Psidium guajava and Polyalthia longifolia respectively. The total chlorophyll of the leaves of the studied plants was estimated to be within the range of 0.41 mg/g and 0.80 mg/g, with the highest value in Anacardium occidentale and the lowest in Tectona grandis while relative water content of leaves ranged between 74.4% (Senna siamea; lowest) and 90.5% (Terminalia catappa; highest). The APTI of the tree species ranged between 9.2 and 12.7, the highest value was obtained in Polyalthia longifolia and the lowest value in Psidum guajava.

Conclusion: P. longifolia, M. indica, G. arborea, T. grandis and T. catappa were the most tolerant to air pollution of all the tree species.