Quantum yield variation across the three pathways of photosynthesis: not yet out of the dark
Quantum yield variation across the three pathways of photosynthesis: not yet out of the dark
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DOI：
10.1093/jxb/ern029
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发表时间：
2008-05-01
影响因子：
6.9
通讯作者：
Skillman, John B.
中科院分区：
文献类型：
--
作者：
Skillman, John B.
收敛量子产额假说（CQY）假设热力学和自然选择共同限制了在其他特定条件下（例如温度和CO2浓度）低光下光合作用最大能量效率的变化。对陆地植物C-3、C-4和CAM光合类型的光合量子产率（phi）研究进行了文献调查，以检验CQY假说。C-3植物的phi值的广泛变化可以通过考虑测量条件对光呼吸是允许的还是限制的来部分解释。根据CO2 phi：O-2 phi比值计算的同化系数（AQ）表明，在C-3植物中，49%和29%的吸收光能分别分配给碳固定和光呼吸。无法解释的其余部分（22%）可能是转移到其他各种能量需求过程（如淀粉合成，氮同化）。这些其他过程对光合效率的单独和累积影响很难量化。在C-4植物中，观察到phi值的变化很小，这与C-4植物表现出很小的光呼吸的事实一致。如前所述，AQ值表明22%的吸收光能不能通过C-4植物中的碳固定来解释。在所有三种光合作用类型中，CAM植物的光合作用的phi是研究最少的，似乎是高度可变的，并且可能对CQY假说提出最大的挑战。大量的能量转移到过程中，而不是碳固定在C-3和C-4植物和CAM植物的光合效率的穷人的特点是显着的缺陷，否则我们强大的理解陆地光合自养的能量。
The convergent quantum yield hypothesis (CQY) assumes that thermodynamics and natural selection jointly limit variation in the maximum energetic efficiency of photosynthesis in low light under otherwise specified conditions (e.g. temperature and CO2 concentration). A literature survey of photosynthetic quantum yield (phi) studies in terrestrial plants from C-3, C-4, and CAM photosynthetic types was conducted to test the CQY hypothesis. Broad variation in phi values from C-3 plants could partially be explained by accounting for whether the measuring conditions were permissive or restrictive for photorespiration. Assimilatory quotients (AQ), calculated from the CO2 phi:O-2 phi ratios, indicated that 49% and 29% of absorbed light energy was allocated to carbon fixation and photorespiration in C-3 plants, respectively. The unexplained remainder (22%) may represent diversion to various other energy-demanding processes (e.g. starch synthesis, nitrogen assimilation). Individual and cumulative effects of these other processes on photosynthetic efficiency are poorly quantified. In C-4 plants, little variation in phi values was observed, consistent with the fact that C-4 plants exhibit little photorespiration. As before, AQ values indicate that 22% of absorbed light energy cannot be accounted for by carbon fixation in C-4 plants. Among all three photosynthetic types, the phi of photosynthesis in CAM plants is the least studied, appears to be highly variable, and may present the greatest challenge to the CQY hypothesis. The high amount of energy diverted to processes other than carbon fixation in C-3 and C-4 plants and the poor characterization of photosynthetic efficiency in CAM plants are significant deficiencies in our otherwise robust understanding of the energetics of terrestrial photoautotrophy.