EVALUATION OF AIR-POLLUTION PHYTOTOXICITY IN A SEASONALLY DRY TROPICAL URBAN-ENVIRONMENT

This study was conducted in the urban environment of Varanasi, India, to evaluate the plant responses to urban air pollution. Twenty sites w ere selected in four different zones of the city. At each site, seven woody perennials of same age classes were selected. Out of the four zo nes (I, II, III and IV), zone IV was used as a reference (control) zon e as it received the minimum pollution input. Plant species growing in polluted and control areas were compared with respect to foliar dust load, pet cent leaf area injury, leaf area, specific leaf weight and c hlorophyll, ascorbic acid, SO42-S and total N concentration in the lea ves. Results indicated that the air pollution level in Varanasi causes leaf damage, reduces leaf area, specific leaf weight and chlorophyll, ascorbic acid and total N concentrations in the leaves. Sulphur conce ntration in leaves increased with increasing level of SO2 in the ambie nt air. The magnitude of such changes was maximum at the zone receivin g maximum pollution load. Carissa carandas was found to be the most se nsitive species and Bougainvillea spectabilis, the least. The study sh ows that the urban air pollution level in Varanasi is detrimental for the growth of plants involved in this study.