冬小麦光合作用对开放式空气CO_2浓度增高(FACE)的非气孔适应

Non-stomatal Acclimation of Leaf Photosynthesis to Free-Air CO_2 Enrichment(FACE)in Winter Wheat

在同样CO2 浓度下测定时 ,开放式空气CO2 浓度增高 (FACE ,5 80 μmolCO2 /mol)条件下生长的冬小麦叶片的净光合速率、气孔导度和羧化效率都显著低于普通空气 ( 3 80 μmolCO2 /mol)中生长的对照叶片。与此相一致 ,FACE叶片的可溶性蛋白、二磷酸核酮糖羧化酶 /加氧酶 (Rubisco)和Rubisco活化酶含量也都显著低于对照叶片。这些结果表明 ,在根系生长不受限制的田间条件下 ,冬小麦叶片的光合作用对高浓度CO2 产生了适应现象 ,其主要原因可能是碳同化的关键酶Rubisco等含量的降低。

In order to explore the mechanism for photosynthetic acclimation to high CO 2 concentration, net photosynthetic rate(Pn), stomatal conductance(Gs), intercellular CO 2 concentration(Ci), and carboxylation efficiency(CE) as well as the soluble proteins, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and Rubisco activase contents were compared between the leaves of winter wheat grown under free-air CO 2 enrichment (FACE) conditions and in normal atmosphere at several development stages. When measured at their growth CO 2 concentrations, Pn, apparent quantum yield of carbon assimilation, instantaneous water use efficiency were significantly higher in leaves grown at elevated CO 2 concentration (580 μmol CO 2 /mol,FACE) than those in normal atmosphere (380 μmol CO 2 /mol, Control) (Figs.1 and 2, Table 1). However, Pn, Gs, and CE were remarkably lower in FACE leaves than control leaves when measured at a same CO 2 concentration (580 μmol CO 2 /mol) (Figs.2, 3). In consonance with these results, the soluble proteins, Rubisco, and Rubisco activase contents were significantly lower in FACE leaves than control leaves (Figs.4, 5). These results indicate that photosynthetic acclimation to high CO 2 concentration occurs in wheat leaves under field conditions without root growth limitation. And the main reason of the acclimation may be a decline in key enzyme contents of photosynthetic carbon assimilation such as Rubisco and its activase rather than decrease in stomatal conductance because Ci has been found not to decrease significantly in many cases.