PHYSIOLOGICAL, BIOCHEMICAL AND DEFENSE SYSTEM RESPONSES OF PARTHENIUM HYSTEROPHORUS TO VEHICULAR EXHAUST POLLUTION

摘要

Pollution caused by vehicular exhaust emissions detrimentally affect plants and other living beings. This investigationwas carried out to evaluate the effects of vehicular exhaust pollutants on Parthenium hysterophorus at various sites alongtwo major roads [Pindi Bhattian to Lillah (M-2) and Faisalabad to Sargodha (FSR) ]in the Punjab, Pakistan. Control samplesof P. hysterophorus were also collected from 100m away from the roads. Chlorophyll contents, photosynthetic rate,transpiration rate, stomatal conductance, substomatal CO2 concentration, water use efficiency, total free amino acids andtotal antioxidant activity of P. hysterophorus were measured. The results depicted significant reductions in chlorophyll a,chlorophyll b, total chlorophyll and carotenoid contents of P. hysterophorus. Likewise, reduction in stomatal conductancewas also recorded which resulted in lowered photosynthetic and transpiration rates. The overall reduction in photosyntheticrate of P. hysterophorus was 30.92% and 35.38% along M-2 and FSR roads, respectively. The limited photosynthesisresulted in increased levels of sub stomatal CO2 concentration and water use efficiency. The elevated levels of free aminoacids and total antioxidant activity were noted and could be attributed to activation of plant’s defense system to cope withthe deleterious effects of vehicular air pollutants. The significant correlations between various attributes of P. hysterophoruswith traffic density signifies the stress caused by vehicular emissions.