Chapter 3 Plants as Accumulators of Atmospheric Emissions

Abstract The uptake of air pollutants by plants occurs through different pathways and processes, including direct uptake of gases through stomata, deposition to the soil and subsequent root uptake, and deposition to external surfaces of bark and foliage. After uptake, pollutants may diffuse or be actively transported to different plant parts. The accumulation rate depends on the balance between the rates of uptake and removal, either by direct excretion or elimination after metabolic processing. Avoidance of toxic effects may occur through sequestering material within the plant in specialized structures, or in a way that minimizes damage. The effective use of plants as bioindicating accumulators of air pollution requires an understanding of the factors that control the concentrations of accumulated material in and on plants: the original deposition pathway; the biological, physical, and chemical processes that occur; and the effects of climate, substrate, and species on the plant itself.