Research Group on Plant Biology under Mediterranean Conditions, Universitat de les Illes Balears-INAGEA, Palma, Balearic Islands, Spain.
Plant Cell Environ. 2017 Oct;40(10):2081-2094. doi: 10.1111/pce.13004. Epub 2017 Aug 7.
High photosynthetic efficiency intrinsically demands tight coordination between traits related to CO diffusion capacity and leaf biochemistry. Although this coordination constitutes the basis of existing mathematical models of leaf photosynthesis, it has been barely explored among closely related species, which could reveal rapid adaptation clues in the recent past. With this aim, we characterized the photosynthetic capacity of 12 species of Limonium, possessing contrasting Rubisco catalytic properties, grown under optimal (WW) and extreme drought conditions (WD). The availability of CO at the site of carboxylation (C ) determined the photosynthetic capacity of Limonium under WD, while both diffusional and biochemical components governed the photosynthetic performance under WW. The variation in the in vivo caboxylation efficiency correlated with both the concentration of active Rubisco sites and the in vitro-based properties of Rubisco, such as the maximum carboxylase turnover rate (k ) and the Michaelis-Menten constant for CO (K ). Notably, the results confirmed the hypothesis of coordination between the CO offer and demand functions of photosynthesis: those Limonium species with high total leaf conductance to CO have evolved towards increased velocity (i.e. higher k ), at the penalty of lower affinity for CO (i.e. lower specificity factor, S ).
高光效内在要求与 CO 扩散能力和叶片生化特性相关的性状之间紧密协调。尽管这种协调构成了现有叶片光合作用数学模型的基础，但在密切相关的物种中几乎没有被探索过，这可能揭示了最近的快速适应线索。为此，我们对 12 种 Limonium 物种进行了光合作用能力的特征描述，这些物种具有不同的 Rubisco 催化特性，在最佳（WW）和极端干旱条件（WD）下生长。在 WD 下，羧化部位 CO 的可用性决定了 Limonium 的光合作用能力，而扩散和生化成分共同控制 WW 下的光合作用性能。体内羧化效率的变化与活性 Rubisco 位点的浓度以及 Rubisco 的体外特性（如最大羧化酶周转率（k ）和 CO 的米氏常数（K ））相关。值得注意的是，结果证实了光合作用 CO 供应和需求功能之间的协调假说：那些具有高叶片总 CO 导度的 Limonium 物种，已经朝着增加速度（即更高的 k ）进化，代价是对 CO 的亲和力降低（即特异性因素 S 较低）。
