Physiological, Biochemical and Defense System Responses of Roadside Vegetation to Auto-Exhaust Pollution.

This study determined the effects of traffic pollutants on plants (Nerium oleander and Ricinus communis) growing along Faisalabad to Okara (R-1) and Okara to Lahore (R-2) roads in Pakistan. The photosynthetic pigments, photosynthetic rate, transpiration rate and total soluble proteins of roadside vegetation were significantly lower than control plants (50 m away from road). The average decrease in photosynthetic rate of Nerium oleander and Ricinus communis was 33.90% and 27.94% along R-1 and 41.85% and 32.409% along R-2 road, respectively. The decreased photosynthesis in roadside flora resulted in higher water use efficiency and substomatal CO2 concentration. However, higher antioxidant activity and free amino acid contents were noted in roadside plants that might be due to their defensive response to traffic pollutants. N. oleander was more affected by traffic pollutants and R. communis showed more resistance. Thus, N. oleander could be used for biomonitoring and R. communis for phytoremediation of vehicular pollution.