Use of physiological and biochemical markers for assessing air pollution stress in trees
Air pollutants such as O3, NOx, SO2, and H2O2 are powerful oxidants that can generate extremely reactive oxygen free radicals that may cause enzyme breakdown, membrane damage, and DNA alterations, all resulting in reduced growth. In this study, specific gas exchange measurements were used diagnostically as indicators of stress and as a means of separating stomatal from biochemical effects on photosynthesis. Similarly, biochemical antioxidants and oxidant stress indicators were hypothesized to be useful as early biomarkers of oxidant stress in trees. Loblolly pine (Pinus taeda L.) seedlings were exposed to a range of ozone treatments in open-top chambers at two study sites in North Carolina. Treatments consisted of charcoal-filtered (CF) air and proportional additions of ozone to non-filtered air in relation to the ambient ozone concentration. Diagnostic gas exchange measurements included the response of photosynthesis and stomatal conductance to irradiance and to intercellular CO2 concentration (Ci). Biochemical measurements included the content of malondialdehyde (MDA), an indicator of lipid peroxidation, and the activities of the enzymatic antioxidants superoxide dismutase (SOD) and peroxidase (Px). These biochemical characteristics were also related to concurrent measurements of light-saturated photosynthesis.
Richardson, CJ; Sasek, TW; Di Giulio, RT
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