Response of roadside tree leaves in a tropical city to automobile pollution

Abstract

One of the sources of air pollutants in the surrounding environment is the automobile emissions. Automobiles produce gaseous and particulate matters which are toxic and inflict damage to roadside plants. Roadside trees are notable for the absorption, sequestering of contaminants and the effective interceptor of airborne pollution. In view of this, the present work was based on investigating the macro-morphological and micro-morphological changes that boost the tolerance and continued existence of four roadside trees, namely Ficus platyphylla, Mangifera indica, Polyalthia longifolia and Terminalia cattapa in the incidence of vehicle exhaust emissions in Kumasi Metropolis, Ghana. Three arterial roads representing three different traffic volumes of extreme, heavy and severe were considered as observational sites. Kwame Nkrumah University of Science and Technology Campus was selected as the control site. The macro-morphological characteristics of the four tree species showed reduced leaf area, whilst the micro-morphological results revealed that stomata size, number and index were reduced at the arterial roadsides in all the four tree species. There was increased epidermal cell number and length and trichome length at the polluted arterial roadsides when compared to the control. These variations can be considered as pointers of environmental stress and could be used as indicators of urban air pollution.