Effect of air pollution on plant secondary metabolites in selected trees of Delhi

Abstract

AbstractAir pollution is emerging as one of the most important stresses, particularly in urban areas, of both developed and developing countries. It severely affects plant growth and development besides being a health hazard to humans and animals. Delhi has the dubious distinction of being one of the most polluted cities in the world. Incidentally, it is also one of the greenest cities with ongoing programs to increase the already considerable forest cover and biodiversity parks. Plants often act as a sink for airborne pollutants, including particulate matter. Hence it is important to evaluate their efficacy in absorbing pollutants and use the promising species for urban plantation. In the present study, the stress tolerance of four common trees of Delhi (Psidium guajava, Alstonia scholaris, Murraya koenigii, and Moringa oleifera), growing in three areas with varying pollution levels, was estimated by measuring Plant Secondary Metabolites (PSMs: total phenols, flavonoids, alkaloids, and tannins) along with the total chlorophyll content of the leaves. P. guajava showed significant increase in the contents of phenols, tannins, and alkaloids with higher Air Quality Index (AQI). Increased amounts of phenols and flavonoids were observed in A. scholaris, those of phenols and alkaloids in M. koenigii, and only of alkaloids in M. oleifera. There was a decrease in the total chlorophyll content of the leaves of all four species investigated. P. guajava and A. scholaris can be recommended for plantation along the sides of roads with heavy traffic movement. Since PSMs are seen to accumulate as a defense mechanism against air pollution too, as in various abiotic and biotic stresses, they can be used as biomarkers for stress tolerance in plants.