Response of leaf anatomy in Ash (Fraxinus rotundifolia Mill.) to pollutant gases and climatic factors

Air pollution is a factor threating the green areas and vegetation in urban zones. Pollutant gases spreading with different density in urban spaces have destructive effects on vegetation along with climatic and antropogenic factors. On the other side, green spaces decrease noticeably the effects of pollutant gases on human society due to their ecological function. This study was carried out to find the effects of urban pollutant gases (SO₂, NO₂ and O₃) and climatic factors (temperature and precipitation) on Fraxinus rotundifolia Mill. In Tehran. For this purposes, anatomical characteristics including leaf blade and cuticle thicknesses, epidermis thickness, blade mesophyll thickness, thickness and number of layers of spongy and palisade parenchyma mesophyll, blade vascular bundle thickness, number and thickness of collenchyma and parenchyma of main vein of Fraxinus rotundifolia Mill. leaves were studied by using correlation analysis. The results demonstrated an increase in leaf blade thickness, blade mesophyll thickness and palisade parenchyma thickness in response to increase in urban air pollution. Furthermore, the ratio of palisade parenchyma to spongy parenchyma (RP/RS) increased as the temperature rose.