Abstract

The discharge of toxic pollutants from automobile exhaust emission are a dominant feature of urban environments pollution problems and represents detrimental effects on urban vegetation. The different effects of automobile exhaust emission on the seed germination and early seedling growth performance of Sesbania grandiflora (L.) Poiret was recorded. The pollutants from the auto emission showed negative effects on seedling height, leaf area, total plant fresh weight, total plant dry weight, root dry weight, stem dry weight, leaf dry weight, root/shoot ratio for fresh weight and root/shoot ratio for dry weight of Sesbania grandiflora. Auto emission showed significantly (p<0.05) toxic effects on seedling growth of Sesbania grandiflora growing in polluted sites (Tariq Road, Bahadurabad, Khalid Bin Waleed Road, Gulshan-e-Iqbal Gulshan-e-Iqbal) of city as compared to Karachi University Campus (Cleaner site).

The seeds of Sesbania grandiflora collected from the Karachi University campus, which is consider as control site showed better percentage of seed germination and seedling growth as compared to the seeds of the same species collected from the different polluted areas of the city. A high percentage of decrease in seed germination was found for the seeds collected from the Tariq Road, followed by Bahadurabad, Khalid Bin Waleed Road and Gulshan-e-Iqbal Gulshan-e-Iqbal as compared to control. Seedling length was also highly decreased for seeds of same species collected from Tariq Road (5.73a±0.53) as compared to control (21.93c±1.07). High percentage of decrease in seedling dry weight was found for seeds of same species collected from Tariq Road, Bahadurabad, Khalid Bin Waleed Road, and Gulshan-e-Iqbal as compared to control. Root growth of Sesbania grandiflora was significantly decreased in the polluted seedlings as compared to control. According to the tolerance test it was observed that the seedling growth of Sesbania grandiflora showed lowest percentage of tolerance in samples collected from Tariq Road, followed by Bahadurabad, Khalid Bin Waleed Road and Gulshan-e-Iqbal Gulshan-e-Iqbal as compared to University Campus.

Keywords: Auto exhaust emission; Pollution; Roadside tree; Seedling growth; Urban site