Air pollution and plant metabolism.

The 20 contributions examine mechanisms by which (potentially) harmful atmospheric gases and their aqueous products can exert an influence on living plant cells at the ultrastructural, biochemical and physiological levels. With a general understanding of metabolic changes, predictive models should be able to assess the relative consequences of atmospheric pollutants upon plants. Papers include discussion of: deposition, uptake and residence of pollutants; carbon gain, allocation and growth as affected by air pollution; interactions between air pollutants and both water stress and cold stress; air pollution effects on plant pathogens; effects of pollutants on mycorrhizae; and effects on host plant/insect relationships

Effects of over-winter fumigation with sulfur and nitrogen dioxides on biochemical parameters and spring growth in red spruce

Red spruce (Picea rubens Sarg.) seedlings were overwintered in two controlled environment chambers designed to simulate sub-zero winter conditions. One of the chambers was fumigated throughout the 5-month period with low concentrations of SO2+ NO2. Extracts of extracellular fluid from trees in this treatment revealed accumulations of sulphite and nitrite, but not of sulphate or nitrate. Analysis of the chloroplast membrane lipid monogalactosyl diglyceride (MGDG) indicated a large increase in fatty acid saturation in both treatments during mid-winter, with a subsequent recovery to earlier levels. Although at the end of the experiment the MGDG of polluted trees contained significantly less linolenic acid, there was no overall treatment effect on fatty, acid content. In the following spring, there was some indication that flushing of leader buds began earlier and proceeded at a slower rate in polluted trees compared to controls, but no other growth parameters were affected by the winter treatment. The absorption of SO2 and NO2 and the accumulation of their products during dormancy is discussed as a potential mechanism for metabolic disruption, resulting in changes to seasonal responses which could be critical to the survival of the plant