The effect of automobile pollutants on plants growing in Karachi during different seasons was studied. In response to the polluted environment, the phenology of Guaiacum officinale and Peltophorum pterocarpum was highly affected at M. A. Jinnah Road, the most polluted area of the city. Automobile emissions also significantly reduced the productivity of fruits and flowers in G. officinale, whereas Azadirachta indica was found comparatively resistant to automobile emissions. The trees growing on busy roads had a significant effect on seed germination. The seeds of Albizia lebbeck showed a significant reduction in germination as compared to Peltophorum pterocarpum.
Effective identification of air pollutant sources and their accumulation in plants would be helpful for environmental protection. The findings would also be helpful for understanding the ecological value of vegetation, which maintains water, climatic conditions, and protection from the hazardous effects of air pollutants.