CO_2浓度升高对两种沈阳城市森林树种光合特性的影响

Effects of Elevated CO_2 Concentration on Photosynthetic Characteristics of Two Urban Forest Species in Shenyang City

利用开顶式气室,研究了CO2浓度升高条件下城市森林主要树种油松(Pinus tabulaefomis)和银杏(Ginkgo biloba)主要光合特性的变化。结果表明,整个生长季,CO2浓度升高(700μmol.mol-1)条件下2树种叶片的净光合速率、可溶性糖、淀粉和可溶性蛋白含量均接近或高于相应对照(自然CO2浓度)值,但不同树种增加的幅度不同;而2树种的叶绿素含量和Chla/Chlb值对CO2浓度升高反应不一,表现为CO2浓度升高条件下油松的叶绿素含量较对照值高,Chla/Chlb值降低,银杏的叶绿素含量为前期升高,后期降低,Chla/Chlb值变化与之正好相反,说明城市森林组成树种对CO2浓度升高的响应具有复杂性。CO2浓度升高条件下,两树种均未发生光合适应现象。

The main photosynthetic characteristics of the main urban forest species Pinus tabulaefomis and Ginkgo biloba in Shenyang City were analyzed in open-top chambers under elevated CO2 concentration. Net photosynthetic rates and soluble sugar, starch and soluble protein content of the leaves of the two species under elevated CO2 concentration （700 μmol·mol^-1） were close to or higher than that of respective controls （natural CO2 concentration）, whose contents were increased differently between species. The responses of chlorophyll content and ratio of Chl a/Chl b under elevated CO2 concentration were not identical for the two species. As well, chlorophyll content increased and ratio of Chl a/Chl b decreased in P. tabulaefomis leaves under elevated CO2 concentration, whereas chlorophyll content of G. biloba leaves increased during the earlier growing season, decreased in the later growing season, and the ratio of Chl a/Chl b responded contrarily, which indicated complexity in the response to elevated CO2 concentration of tree species in an urban forest. Both tree species showed no photosynthetic acclimation to elevated CO2 concentration.