Physiological Aspects of Air Pollution Stress in Forests

1996

S. 15-22

42 Lit. Ang.

Unselbständiges Werk

200101753

Air pollutants, such as ozone, sulfur dioxide, nitrogen compounds and others, affect health of forests in Europe and North America. Gaseous air pollutants enter plants mainly through stomata, although transcuticular transport can also be important for some pollutants. Toxic effects of pollutants depend on their effective dose that is proportional to pollutant ambient concentration and plant stomatal conductance. Mechanisms of air pollution toxicity are very complex and depend on various physiological and biochemical properties of plants. These mechanisms (including formation of free radicals) are still poorly understood. In addition, physiological responses of forest plants to air pollution stress can be modified by various biotic (e.g., insects, pathogens, mycorrhizae associations, genetic variation) and abiotic (e.g., increasing CO2 concentrations, ultraviolet-B radiation, nitrogen deposition, nutrient deficiencies, drought) factors. An example of air pollution effects on forest trees may be responses of ponderosa pine seedlings to elevated concentrations of ozone in the Sierra Nevada. Various physiological changes caused by ozone (e.g., lowered net photosynthesis, altered carbon allocation, deterioration of photosynthetic pigments, etc.) have led to the reduced growth and biomass of the seedlings.