ADAPTATIONAL STRATEGY OF A TROPICAL SHRUB CARISSA-CARANDAS L TO URBANAIR-POLLUTION

This paper reports the adaptational response of a tropical shrub Caris sa Carandas L. to urban air pollution stress in Varanasi, India. Sapli ngs of C. carandas were grown at a density of one per pot and kept for two years at 25 selected sites in the urban environment. Different si tes received different levels of air pollution input. Changes in veget ative growth pattern (leafing and branching), in morphological feature s and in the distribution of biomass to above and below ground structu res were considered in relation to the ambient air quality. Different levels of air pollution input produced different sets of harmful effec ts. Although the air pollution level at Varanasi reduced the plant hei ght, basal diameter, canopy area, leaf area and total plant biomass of C. carandas, this species retained a major fraction of its photosynth ate to above-ground plant parts where foliage assumes predominance. Si nce carbon gain is dependent not only on the rate of carbon acquisitio n per unit leaf tissue but also on the amount of photosynthetic tissue present, a shift in relative contribution of photosynthate to leaf pr oduction and shoot growth appears to be a pollution-induced adaptive r esponse in C. carandas.