Evaluation of pigment concentrations of roadside tree species as bioindicators of air pollution in Abakaliki Metropolis

Abstract

Variations in the concentration of different photosynthetic pigments (Chlorophyll and carotenoids) of leaves of three tree species growing in some polluted sites were evaluated. Terminalia catappa, Polyalthia longifolia and Mangifera indica which were in abundance and well distributed in the Residential (Control), Industrial and Traffic sites (Polluted area) were selected for the study. Reduction in chlorophyll ‘a’, ‘b’ and carotenoid was recorded in the leaf samples collected from polluted sites when compared with samples from control sites. In the polluted area (Industrial and Traffic sites), the highest decrease in total chlorophyll of the studied plants was in Mangifera indica (1.02 mg/g) followed by Terminalia catappa (0.89 mg/g) and Polyalthia longifolia (0.78 mg/g). There was a decrease in carotenoid content at the polluted area (Industrial and Traffic sites) compared with the control (Residential). The value was highest in Terminalia catappa (0.19 mg/g) and lowest in Mangifera indica (0.12 mg/g). It is evident from this study that residential tree species have more chlorophyll a/b ratio compared with the tree species exposed to air pollution. The ratio of chlorophyll a+b and carotenoid ratio decreased, which is an indication of stress arising from the industrial and vehicular air pollution. This study clearly showed that the industrial and vehicular-induced air pollution reduced the concentration of photosynthetic pigments in the trees exposed to it. These changes could be used as bioindicator of air pollution of an area.