Physiological functioning of Lagerstroemia speciosa L. under heavy roadside traffic: an approach to screen potential species for abatement of urban air pollution

The mitigation potential of avenue tree species needs a sound understanding, especially for landscape planning or planting tree species on roadside, especially in city limits where there is huge traffic due to more number of vehicles. A preliminary study was conducted to investigate the impact of heavy traffic movement and pollution thereof on physiological functioning of Lagerstroemia speciosa trees planted on roadside in terms of carbon absorption, mitigation potential and adaptive behavior. Trees on roadside exhibited reduced carbon assimilation (36.7 ± 2.4%) and transpiration rate (42.14 ± 2.9%), decreased stomatal conductance (66.85 ± 3.87%), increased stomatal resistance (212.2 ± 11.25%), more leaf thickness (40.54 ± 3.25) and water use efficiency (9.4 ± 0.87%), and changes in lead (179.31 ± 10.24%) and proline (15.61 ± 1.92%) concentration in leaf tissues when compared to less traffic area (FRI campus). The impacts were also witnessed in the form of enhanced vapour pressure deficit of air (63.18 ± 4.94%) and leaf (45.72 ± 3.25%), and air temperature (3.2 ± 0.16%) and leaf temperature (9.0 ± 0.82%) along roadside trees. It was inferred that heavy traffic movements interrupt the physiological functioning of trees due to alteration in the surrounding environment as compared to non-traffic areas. The present study provides baseline information to further explore and identify the potential avenue tree species having significant mitigation potential and adaptive efficiency to heavy traffic movements for improving urban environment.