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Title: Effects of air pollutants on the composition of stable carbon isotopes delta/sup 13/C, of leaves and wood, and on leaf injury

Journal Article · · Fish. Bull.; (United States)
OSTI ID:6020860

Air pollutants are known to cause visible leaf injury as well as impairment of photosynthetic CO/sub 2/ fixation. Here we evaluate whether the effects on photosynthesis are large enough to cause changes in the relative composition of stable carbon isotopes, delta/sup 13/C, of plant tissue samples, and, if so, how the changes relate to visual leaf injury. For that purpose, several woody and herbaceous plant species were exposed to SO/sub 2/ + O/sub 3/ and SO/sub 2/ + O/sub 3/ + NO/sub 2/ for one month. At the end of the fumigations, the plants were evaluated for visual leaf lesions, and delta/sup 13/C of leaf tissue was determined. Woody plants generally showed less visual leaf injury and smaller effects on delta/sup 13/C of pollutant exposure than did herbaceous plants. If delta/sup 13/C was affected by pollutants, it became, with few exceptions, less negative. The data from the fumigation experiments were consistent with delta/sup 13/C analyses of whole wood of annual growth rings from two conifer tree species, Pseudotsuga menziesii and Pinus strobus. These trees had been exposed until 1977 to exhaust gases from a gas plant at Lacq, France. Wood of both conifer species formed in the polluted air of 1972 to 1976 had less negative delta/sup 13/C values than had wood formed in the much cleaner air in 1982 to 1986. No similar, time-dependent differences in delta/sup 13/C of wood were observed in trees which had been continuously growing in clean air. Our delta/sup 13/C data from both relatively short-term artificial exposures and long-term natural exposure are consistent with greater stomatal limitation of photosynthesis in polluted air than in clean air.

Research Organization:
Native Plants, Inc., Salt Lake City, UT (USA)
OSTI ID:
6020860
Journal Information:
Fish. Bull.; (United States), Vol. 88:1
Country of Publication:
United States
Language:
English