Effect of autoexhaust emission on germination and seedling growth of an important arid tree Cassia siamea Lamk.

Automobile exhaust emission showed toxic effects on seed germination and seedling growth of Cassia siamea. Germination and growth of C. siamea seeds was significantly (p 0.05) affected in seeds collected from M. A. Jinnah Road, Sharah-e-Faisal, Nazimabad, and Gulshan-e-Iqbal as compared to University campus. The seeds of C. siamea collected from the Karachi University campus, which is considered as control site showed better percentage of seed germination and seedling growth as compared to the seeds of the same species collected from the city area. Higher percentage of decrease in seed germination was found for seeds collected from M. A. Jinnah road, followed by Shahrah-e-Faisal, Nazimabad, and Gulshan-e-Iqbal as compared to control. Seedling length and root length was also highly decreased for seeds of same species collected from M. A. Jinnah road as compared to control. High percentage of decrease in seedling dry weight was found for seeds of same species collected from M.A. Jinnah road, followed by Shahrah-e-Faisal, Nazimabad, Gulshan-e-Iqbal as compared to control. According to tolerance test it was observed that seedling growth of C. siamea showed lowest percentage of tolerance in samples collected from M. A. Jinnah Road followed by Sharah-e-Faisal, Nazimabad and Gulshan-e-Iqbal as compared to Campus.