Analysis of the physiological responses of the plane and willow trees against air pollution in Tehran .

Trees can improve air quality, but at the same time, pollution might put them at risk. Plane(Platanus orientalis L) and willow trees (Salix babylonicaL) are important trees in the green space of Tehran. Plane trees in Tehran have experienced early autumn in recent years due to severe air pollution. The present study, investigated some physiological traits of these trees under study to determine the cause of early autumn phenomenon. Three regions in Tehran were chosen for the study:  Sadra Park as a clean region, Al-Mahdi Park as the polluted region 1, and Avesta Park as the polluted region 2. The results showed that the highest levels of chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, and anthocyanins were observed in the leaves of the plane trees of Sadra Park and the leaves of the willow trees of the Avesta Park and Sadra Park. The average concentration of lead (Pb) in the plane leaves was observed in the Avesta Park and the highest cadmium concentration was recorded for the Sadra Park while the concentration of these two metals in the leaves of willow trees in the three regions were not significantly different. This may suggest that the willow trees, by an increase in the amount of anthocyanins of their leaves, prevent the reduction of the amount of photosynthetic pigments under the influence of air pollution. By late spring, the two plants could relatively preserve similar amounts of lead and cadmium in their leaves.