State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, PR China.
Physiol Plant. 2012 Jul;145(3):395-405. doi: 10.1111/j.1399-3054.2012.01581.x. Epub 2012 Mar 6.
In this study, we tested for the temporal occurrence of photosynthetic acclimation to elevated [CO₂] in the flag leaf of two important cereal crops, rice and wheat. In order to characterize the temporal onset of acclimation and the basis for any observed decline in photosynthetic rate, we characterized net photosynthesis, g(s) , g(m) , C(i) /C(a) , C(i) /C(c) , V(cmax) , J(max) , cell wall thickness, content of Rubisco, cytochrome (Cyt) f, N, chlorophyll and carbohydrate, mRNA expression for rbcL and petA, activity for Rubisco, sucrose phosphate synthase (SPS) and sucrose synthase (SS) at full flag expansion, mid-anthesis and the late grain-filling stage. No acclimation was observed for either crop at full flag leaf expansion. However, at the mid-anthesis stage, photosynthetic acclimation in rice was associated with RuBP carboxylation and regeneration limitations, while wheat only had the carboxylation limitation. By grain maturation, the decline of Rubisco content and activity had contributed to RuBP carboxylation limitation of photosynthesis in both crops at elevated [CO₂]; however, the sharp decrease of Rubisco enzyme activity played a more important role in wheat. Although an increase in non-structural carbohydrates did occur during these later stages, it was not consistently associated with changes in SPS and SS or photosynthetic acclimation. Rather, over time elevated [CO₂] appeared to enhance the rate of N degradation and senescence so that by late-grain fill, photosynthetic acclimation to elevated [CO₂] in the flag leaf of either species was complete. These data suggest that the basis for photosynthetic acclimation with elevated [CO₂] may be more closely associated with enhanced rates of senescence, and, as a consequence, may be temporally dynamic, with significant species variation.
在这项研究中，我们测试了两种重要谷物作物——水稻和小麦——旗叶对高浓度[CO₂]的光合作用适应的时间发生情况。为了描述适应的时间起始和任何观察到的光合速率下降的基础，我们描述了净光合速率、g(s)、g(m)、C(i)/C(a)、C(i)/C(c)、V(cmax)、J(max)、细胞壁厚度、Rubisco 含量、细胞色素（Cyt）f、N、叶绿素和碳水化合物、rbcL 和 petA 的 mRNA 表达、Rubisco、蔗糖磷酸合酶（SPS）和蔗糖合酶（SS）的活性，在旗叶完全展开、开花中期和后期灌浆阶段。在旗叶完全展开时，两种作物都没有观察到适应。然而，在开花中期，水稻的光合作用适应与 RuBP 羧化和再生限制有关，而小麦只有羧化限制。到谷物成熟时，Rubisco 含量和活性的下降导致两种作物在高浓度[CO₂]下的 RuBP 羧化限制光合作用；然而，Rubisco 酶活性的急剧下降在小麦中发挥了更重要的作用。尽管在这些后期阶段非结构性碳水化合物确实增加，但它与 SPS 和 SS 或光合作用适应的变化不一致。相反，随着时间的推移，高浓度[CO₂]似乎增强了氮的降解和衰老速度，以至于到后期灌浆时，两种作物旗叶对高浓度[CO₂]的光合作用适应已经完全完成。这些数据表明，高浓度[CO₂]下光合作用适应的基础可能与衰老速度的提高更为密切相关，因此可能具有时间动态性，存在显著的物种差异。
