Evaluation of air pollution phytotoxicity in a seasonally dry tropical urban environment using three woody perennials



A two-year study was conducted in the urban environment of Varanasi, India, to evaluate plant responses to urban air pollution. Three species including a shrub (Carissa carandas L.) and two tree species (Delonix regia Rafin and Cassia fistula L.) were grown in pots at selected study sites. Changes in plant performance were considered in relation to the status of ambient air quality.

Reductions in plant height, basal diameter, canopy area, plant biomass and chlorophyll, ascorbic acid and nitrogen contents in leaves were correlated with air pollution level at different sites. The magnitude of response indicated the relative sensitivity of the three species in the order D. regia > C. fistula > C. carandas. Shifts in relative contribution of photosynthate to leaf production and shoot growth appear to be a pollution-induced adaptive response in C. carandas. The study shows that the urban air pollution level at Varanasi is detrimental to the growth of plants.