Comprehensive analysis of air pollution tolerance and anticipated performance indices of different tree species growing in urban environment

This study deals with the Air Pollution Tolerance Index (APTI) and Anticipated Performance Index (API) of thirty eight tree species growing in polluted and unpolluted areas of Coimbatore city to identify their tolerance against air pollution. A comprehensive assessment on APTI was carried out at first over two years, considering the changes in physiological factors like relative water content, leaf extract pH, ascorbic acid, and total chlorophyll. Furthermore, API of these 38 tree species was employed to assess their performance against air pollution based on diverse characteristics like tolerance (APTI), biological parameters (tree habit, canopy structure, type of tree), morphological laminar structure (leaf size, texture, hardiness), and socioeconomic factors (multiple uses). The combination of APTI and API emerges as a pivotal approach for identifying the right species for urban green endeavors. From the present study, Ficus religiosa (APTI 29.19), Polyalthia longifolia (APTI 25.81), Pithecellobium dulce (APTI 18.91), Samanea saman (APTI 17.83) and Thespesia populnea (APTI 17.15) are the best suited tree species for planting in an air pollution zone as these trees poses high APTI values. Similarly, plant species with API scores as 81.25% for Pithecellobium dulce, Tamarindus indica, Terminalia catappa and Thespesia populnea while as 75% for Azadirachta indica, Alstonia scholaris, Ficus religiosa and Mangifera indica displayed notable tolerance to air pollution. Finally, micro morphological features of Ficus religiosa, Polyalthia longifolia, Pithecellobium dulce, Samanea saman and Thespesia populnea leaves observed through Scanning Electron Microscope (SEM) confirm that these tree species poses high particulate matters retention capacity which make them desirable for air pollution zone.