To develop the usefulness of Caesalpinia pulcherrima and Catharanthus roseus plants as bioindicators, which entail an utmost importance for a particular situation. This study focuses on the assessment of air pollution tolerance index (APTI) of two selected plant species commonly found along roadsides in Bengaluru, India. The plant species selected for the study were Caesalpinia pulcherrima and Catharanthus roseus. The plants were evaluated in terms of APTI by analyzing four different

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... parameters: Leaf relative water content (RWC), Ascorbic acid content (AA), Total leaf chlorophyll (TCh), and pH of leaf extract. Based on APTI Caesalpinia pulcherrima was found to be more tolerant compared to Catharanthus roseus. Species with lower APTI value are considered sensitive species, which can be used as a biological indicator for further monitoring of air quality. Species with higher APTI value are tolerant species and thus, can be planted for pollution abatement in order to control and reduce environmental pollution.