Impacts of vehicle emissions on vegetation

A system has been constructed which provides stable, realistic urban atmospheres with pollutant mixtures at concentrations and proportions relevant to those found at roadsides in urban areas. This system has been used in conjunction with a range of field sites to assess the impacts of urban pollution mixtures on a broad range of plant species of contrasting morphological and functional types. Impacts of pollution treatments have been assessed in terms of visible injury symptoms, growth, rates of stomatal conductance, senescence, and leaf surface characteristics. Our data clearly demonstrate that levels of pollutant mixtures typical of urban areas do have species-specific, direct effects on plant growth and may make plants susceptible to other environmental stresses