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Quantum yield variation across the three pathways of photosynthesis: not yet out of the dark

机译：跨越光合作用的三种途径的量子产率变化：尚未摆脱黑暗

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摘要

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 (ϕ) studies in terrestrial plants from C3, C4, and CAM photosynthetic types was conducted to test the CQY hypothesis. Broad variation in ϕ values from C3 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 ϕ:O2 ϕ ratios, indicated that 49% and 29% of absorbed light energy was allocated to carbon fixation and photorespiration in C3 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 C4 plants, little variation in ϕ values was observed, consistent with the fact that C4 plants exhibit little photorespiration. As before, AQ values indicate that 22% of absorbed light energy cannot be accounted for by carbon fixation in C4 plants. Among all three photosynthetic types, the ϕ 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 C3 and C4 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.
机译：收敛量子产率假设（CQY）假设在其他条件下（例如温度和CO 2 浓度），热力学和自然选择共同限制了弱光条件下光合作用的最大能量效率的变化。对C 3 ，C 4 和CAM光合作用类型的陆生植物进行的光合作用量子产率研究，以检验CQY假说。 C 3 植物ϕ值的宽泛变化可以部分解释测量条件是允许还是限制光呼吸。由CO 2 ϕ：O 2 ϕ比计算得出的同质商（AQ）表明，吸收的光能的49％和29％被分配给碳固定和光呼吸分别在C 3 植物中无法解释的剩余物（22％）可能代表转向其他各种能量需求过程（例如淀粉合成，氮同化）。这些其他过程对光合作用效率的个体和累积影响很难量化。在C 4 植物中，observed值几乎没有变化，这与C 4 植物几乎没有光呼吸的事实相一致。如前所述，AQ值表明在C 4 植物中固碳无法解释22％的吸收光能。在所有三种光合作用类型中，CAM植物中光合作用的ϕ研究最少，似乎变化很大，并且可能对CQY假设提出最大的挑战。在C 3 和C 4 植物中，大量能量转移到除碳固定以外的过程中，而CAM植物的光合效率表征不佳，这在我们本来就健壮的研究中是明显的缺陷。对陆地光自养的能量学的理解。

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    《Journal of Experimental Botany》 |2008年第7期|p.1647-1661|共15页
  • 作者

    John B. Skillman*;

  • 作者单位

    Department of Biology, California State University, San Bernardino, CA 92407, USA;

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  • 正文语种 eng
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