Kellomäki S, Wang K Y
University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland.
Environ Pollut. 1997;97(1-2):17-27. doi: 10.1016/s0269-7491(97)00084-5.
Naturally regenerated, 30-year-old Scots pines (Pinus Sylvestris L.) were grown in open-top chambers and exposed in situ to doubled ambient O(3), doubled ambient CO(2) and a combination of elevated O(3) and CO(2) from 15 April to 15 September for three growing seasons (1994-1996). To examine the effects of O(3) and/or CO(2) on photosynthesis, chlorophyll a fluorescence and gas exchange were measured simultaneously. Doubled ambient O(3) significantly decreased the rates of photosynthesis at all levels of photon flux density. This was related mainly to a significant decrease in the photochemical efficiency of photosystem II (PS II) and the rate of whole electron transport, rather than to a decrease in stomatal conductance. When measurements were made at doubled ambient concentration of CO(2) (700 micromol mol(-1)), doubled ambient CO(2) treatment did not lead to a significant change in the intrinsic capacity of photosynthesis, as manifested by no changes in PS II, the rate of electron transport, the maximal rate of photosynthesis and the apparent quantum yield of CO(2) assimilation. However, elevated CO(2) increased the sensitivity of stomatal conductance to light and decreased maximal stomatal conductance. When O(3) and CO(2) were combined, the O(3)-induced decrease in photosynthesis rate was reduced significantly by a high concentration of CO(2). This may be partly related to the decrease in stomatal conductance induced by the high concentration of CO(2). The complete mechanism behind this interaction is, however, still unclear.
自然再生的30年生苏格兰松（Pinus Sylvestris L.）种植于开顶式气室中，于1994年至1996年的三个生长季（4月15日至9月15日）在原位暴露于两倍于环境浓度的臭氧、两倍于环境浓度的二氧化碳以及臭氧和二氧化碳浓度均升高的组合环境中。为研究臭氧和/或二氧化碳对光合作用的影响，同时测定了叶绿素a荧光和气体交换。两倍于环境浓度的臭氧在所有光通量密度水平下均显著降低了光合作用速率。这主要与光系统II（PS II）的光化学效率和全电子传递速率显著降低有关，而非气孔导度降低。当在两倍于环境浓度的二氧化碳（700 μmol mol⁻¹）条件下进行测量时，两倍于环境浓度的二氧化碳处理并未导致光合作用内在能力发生显著变化，这表现为PS II、电子传递速率、最大光合作用速率和二氧化碳同化表观量子产率均无变化。然而二氧化碳浓度升高增加了气孔导度对光的敏感性并降低了最大气孔导度。当臭氧和二氧化碳同时存在时，高浓度二氧化碳显著减轻了臭氧诱导的光合作用速率下降。这可能部分与高浓度二氧化碳诱导的气孔导度降低有关。然而，这种相互作用背后的完整机制仍不清楚。
