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首页> 外文期刊>Journal of Experimental Botany >Increasing water use efficiency along the C-3 to C-4 evolutionary pathway: a stomatal optimization perspective
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Increasing water use efficiency along the C-3 to C-4 evolutionary pathway: a stomatal optimization perspective

机译：沿C-3至C-4进化途径提高用水效率：气孔优化观点

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摘要

C-4 photosynthesis evolved independently numerous times, probably in response to declining atmospheric CO2 concentrations, but also to high temperatures and aridity, which enhance water losses through transpiration. Here, the environmental factors controlling stomatal behaviour of leaf-level carbon and water exchange were examined across the evolutionary continuum from C-3 to C-4 photosynthesis at current (400 mu mol mol(-1)) and low (280 mu mol mol(-1)) atmospheric CO2 conditions. To this aim, a stomatal optimization model was further developed to describe the evolutionary continuum from C-3 to C-4 species within a unified framework. Data on C-3, three categories of C-3-C-4 intermediates, and C-4 Flaveria species were used to parameterize the stomatal model, including parameters for the marginal water use efficiency and the efficiency of the CO2-concentrating mechanism (or C-4 pump); these two parameters are interpreted as traits reflecting the stomatal and photosynthetic adjustments during the C-3 to C-4 transformation. Neither the marginal water use efficiency nor the C-4 pump strength changed significantly from C-3 to early C-3-C-4 intermediate stages, but both traits significantly increased between early C-3-C-4 intermediates and the C-4-like intermediates with an operational C-4 cycle. At low CO2, net photosynthetic rates showed continuous increases from a C-3 state, across the intermediates and towards C-4 photosynthesis, but only C-4-like intermediates and C-4 species (with an operational C-4 cycle) had higher water use efficiencies than C-3 Flaveria. The results demonstrate that both the marginal water use efficiency and the C-4 pump strength increase in C-4 Flaveria to improve their photosynthesis and water use efficiency compared with C-3 species. These findings emphasize that the advantage of the early intermediate stages is predominantly carbon based, not water related.
机译：C-4光合作用独立地进化了许多次，这可能是由于大气中CO2浓度的下降，也是由于高温和干旱导致的，这些水分和水分通过蒸腾作用增加了水分的流失。在这里，在当前（400μmol mol（-1））和低（280μmol mol）的条件下，研究了从C-3到C-4光合作用的进化连续体，控制叶水平碳和水交换气孔行为的环境因素（-1））大气CO2条件。为此，进一步开发了气孔优化模型，以在统一框架内描述从C-3到C-4物种的进化连续体。使用有关C-3，三类C-3-C-4中间体和C-4 Flaveria物种的数据对气孔模型进行参数化，包括边际用水效率和CO2浓缩机制效率的参数（或C-4泵）;这两个参数被解释为反映C-3到C-4转化过程中气孔和光合调节的性状。从C-3到早期C-3-C-4中间阶段，边际用水效率和C-4泵送强度都没有显着变化，但是在早期C-3-C-4中间产物和C-具有C-4循环操作的4类中间体。在低CO2的条件下，净光合速率显示出从C-3状态，跨中间体向C-4光合作用的持续增长，但只有C-4类中间体和C-4物种（具有可操作的C-4循环）用水效率比C-3 Flaveria高。结果表明，与C-3物种相比，C-4 Flaveria的边际水分利用效率和C-4泵浦强度都有所提高，以改善其光合作用和水分利用效率。这些发现强调，早期中间阶段的优势主要是基于碳的，与水无关。

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