Biological monitoring and assessment studies due to urban--road pollutants were carried out using Air Pollution Tolerance Index (APTI) of plants. Four plant (leaf) parameters--namely ascorbic acid, total chlorophyll, relative water content and leaf extract pH were combined together in a formulation signifying the APTI of plants. APTI was calculated for five different shrub species viz. Bougainvillea glabra, Duranta repens,Lantana camara, Ricinus communis and Sambucus hookeri growing in four different areas, i.e. control area and along the roadsides in Kathmandu valley. The control site was selected in the Tribhuvan University, Campus area. Reduction in total chlorophyll content and pH was found in the leaf samples of all selected plants collected from less polluted sites (control) when compared with samples from more polluted site, whereas APTI, ascorbic acid and RWC were found to be higher in the plant samples of more polluted site as compared to less polluted site (control). From the results obtained, it has been observed that Bougainvillea glabra and Duranta repens were the most tolerant species since they have high APTI values. Tolerant plant species can be used in green belt development as they tend to serve as barriers and act as sink for air pollutants. The sensitive species were Lantana camera and Ricinus communis . They can be used as bio-indicators to air quality. Such studies will help in future planning of the roadside landscape in order to reduce pollution.

Keywords: Air pollution tolerance index (APTI), Total chlorophyll content, Ascorbic acid, pH, Dust ,Shrub species