Adaptation and mitigation potential of roadside trees with bio-extraction of heavy metals under vehicular emissions and their impact on physiological traits during seasonal regimes

A massive increase in air emissions resulted from the growing population and the increasing use of automobiles. This air pollution adversely affects living beings including humans, plants as well as a physical property of the surrounding environment. In this way, tree species standing along with the roadside and in their proximity act as defense guard against vehicular emission. In view of this, the present investigation was conducted to assess the adaptation and mitigation potential of roadside tree species (Pinus roxburghii, Quercus leucotrichophora, Cupressus cashmeriana, Daphniphyllum himalense and Lyonia ovalifolia) towards air pollution and their physiological response during different seasons i.e. spring, summer and autumn, under heavy metal accumulation. The higher accumulation of heavy metals was observed in P. roxburghii during summer season at S1 (near to road) and S2 (1.5 km far from S1) site over the control site S3 (5 km far from S1), while physiological traits viz. CO2 assimilation, stomatal conductance, and transpiration were recorded higher in Q. leucotrichophora during summer season at control site S3 and decreased at S2 and S1. Chlorophyll a, b, carotenoid contents and cooling impact were also higher in Q. leucotrichophora during summer season at control site S3 and decreased at S2 and S1 site. However, during the summer season at control site S3, the air pollution tolerance index (APTI) was higher for P. roxburghii and Q. leucotrichophora, and decreased at site S2 and S1. Thus we found that all tree species performed well and to be used as one of the potential tree species for roadside plantation to mitigate air pollution.

Automated summary

The study revealed the varying adaptation and mitigation potential of different roadside tree species towards air pollution in summer, with Quercus leucotrichophora showing better physiological responses. These tree species can be considered as potential candidates for roadside plantation to alleviate air pollution.