© 1992 Heron Publishing—Victoria, Canada
Biochemical composition of loblolly pine reflects pollutant exposure
Alexander L. Friend (1), Patricia T. Tomlinson (2), Richard E. Dickson (2), E. Gerry O’Neill (3), Nelson T. Edwards (3) and George E. Taylor, Jr. (4)
1. Department of Forestry, Mississippi State University, P.O. Drawer FR, Mississippi State, MS 39762, USA / 2. USDA Forest Service, North Central Forest Experiment Station, P.O. Box 898, Rhinelander, WI 54501, USA / 3. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6034, USA / 4. Desert Research Institute, University of Nevada, P.O. Box 60220, Reno, NV 89506-0220, USA / Received August 23, 1991
Summary
Under experimental conditions, the growth of loblolly pine (Pinus taeda L.) is often responsive to ozone at near-ambient concentrations. However, little is known of the biochemical changes associated
with this or other pollutants. Loblolly pine seedlings in open-top chambers were exposed to combinations of ozone (sub-ambient,
ambient, or twice-ambient), acidic precipitation (pH 3.8 or pH 5.2) and soil magnesium (0.15 or 0.32 μg g–1 exchangeable Mg) for three growing seasons. The effects of these treatments were greater in foliage than in stems or roots.
The largest treatment effect was a 50% decrease in the starch concentration of current-year foliage from the twice-ambient
ozone treatment compared with current-year foliage from the sub-ambient ozone treatment. Responses to ozone were consistent
with the hypothesis that ozone-induced growth reductions are associated with depletion of carbohydrate reserves resulting
from injury compensation and repair processes or reduced carbon fixation or both. Addition of acidic precipitation, and to
a small extent Mg, decreased sugar concentrations of tissues; however, this effect appeared to be mediated by nutrient addition
rather than by acidity per se. Given the role of carbohydrates in plant resistance to environmental stress, the sensitivity of carbohydrates to experimental
treatments demonstrates the potential for indirect effects of ozone, acidic precipitation, and soil properties on stress resistance.
Noncarbohydrate constituents were largely unresponsive to the experimental treatments. These findings imply that tissue carbohydrate
analysis may be useful for assessing the impacts of pollutants in forest ecosystems.
