© 1994 Heron Publishing—Victoria, Canada
Leaf-level and whole-plant gas exchange characteristics of shortleaf pine exposed to ozone and simulated acid rain
Richard B. Flagler (1), John E. Lock (2) and Christine G. Elsik (1)
1. Department of Forest Science, Texas Agricultural Experiment Station, Texas A&M University System, College Station, Texas 77843-2135,
USA / 2. Department of Forest Science, Texas Agricultural Experiment Station, Route 3, Box 2973, Nacogdoches, Texas 75961, USA / Received May 3, 1993
Summary
Field-grown shortleaf pine (Pinus echinata Mill.) seedlings were exposed to ozone (O3) and simulated acid rain (SAR) in open-top chambers over three growing seasons. Ranges of O3 and SAR spanned ambient levels found in the southern USA. Effects of O3 on leaf-level and whole-plant gas exchange were characterized for a single measurement period immediately before the third
summer of exposure. Decreased photosynthesis rates were attributed to O3, but not SAR. Stomatal conductance decreased in response to O3 exposure, and either increased or was unaffected by SAR. Increased internal CO2 concentration (ci) in response to O3 treatment indicated a greater effect of O3 on photosynthetic capacity than stomatal conductance. Whole-seedling gas exchange characteristics indicated that whole-seedling
carbon assimilation was more severely affected by O3 than was evident from leaf-level gas exchange characteristics. Seedlings exposed to O3 retained fewer flushes than seedlings grown in charcoal-filtered air.
Keywords:
internal CO2 concentration, leaf-level gas exchange, photosynthesis, Pinus echinata, stomatal conductance, transpiration, water-use efficiency, whole-plant gas exchange.
