Flagler R B, Lock J E, Elsik C G
Department of Forest Science, Texas Agricultural Experiment Station, Texas A&M University System, College Station, Texas 77843-2135, USA.
Tree Physiol. 1994 Apr;14(4):361-74. doi: 10.1093/treephys/14.4.361.
Field-grown shortleaf pine (Pinus echinata Mill.) seedlings were exposed to ozone (O(3)) and simulated acid rain (SAR) in open-top chambers over three growing seasons. Ranges of O(3) and SAR spanned ambient levels found in the southern USA. Effects of O(3) 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 O(3), but not SAR. Stomatal conductance decreased in response to O(3) exposure, and either increased or was unaffected by SAR. Increased internal CO(2) concentration (c(i)) in response to O(3) treatment indicated a greater effect of O(3) on photosynthetic capacity than stomatal conductance. Whole-seedling gas exchange characteristics indicated that whole-seedling carbon assimilation was more severely affected by O(3) than was evident from leaf-level gas exchange characteristics. Seedlings exposed to O(3) retained fewer flushes than seedlings grown in charcoal-filtered air.
在三个生长季节中，将田间种植的短叶松（Pinus echinata Mill.）幼苗置于开顶式气室中，使其暴露于臭氧（O₃）和模拟酸雨（SAR）环境下。O₃和SAR的浓度范围涵盖了美国南部发现的环境水平。在暴露的第三个夏季来临前的一个测量期内，对O₃对叶片水平和整株植物气体交换的影响进行了表征。光合作用速率的降低归因于O₃，而非SAR。气孔导度因O₃暴露而降低，而SAR对其的影响则是使其增加或未受影响。O₃处理导致内部CO₂浓度（c(i)）升高，这表明O₃对光合能力的影响大于对气孔导度的影响。整株幼苗的气体交换特征表明，与叶片水平的气体交换特征相比，O₃对整株幼苗碳同化的影响更为严重。暴露于O₃的幼苗比在经过活性炭过滤的空气中生长的幼苗保留的新梢更少。
