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Revisiting carbon isotope discrimination in C 3 plants shows respiration rules when photosynthesis is low
Nature Plants ( IF 15.8 ) Pub Date : 2020-03-09 , DOI: 10.1038/s41477-020-0606-6
Florian A. Busch , Meisha Holloway-Phillips , Hilary Stuart-Williams , Graham D. Farquhar

Stable isotopes are commonly used to study the diffusion of CO2 within photosynthetic plant tissues. The standard method used to interpret the observed preference for the lighter carbon isotope in C3 photosynthesis involves the model of Farquhar et al., which relates carbon isotope discrimination to physical and biochemical processes within the leaf. However, under many conditions the model returns unreasonable results for mesophyll conductance to CO2 diffusion (gm), especially when rates of photosynthesis are low. Here, we re-derive the carbon isotope discrimination model using modified assumptions related to the isotope effect of mitochondrial respiration. In particular, we treat the carbon pool associated with respiration as separate from the pool of primary assimilates. We experimentally test the model by comparing gm values measured with different CO2 source gases varying in their isotopic composition, and show that our new model returns matching gm values that are much more reasonable than those obtained with the previous model. We use our results to discuss CO2 diffusion properties within the mesophyll.



中文翻译:

在光合作用低下时,重新审视C 3植物中的碳同位素歧视显示出呼吸规则

稳定同位素通常用于研究CO 2在光合植物组织中的扩散。用于解释观察到的对C 3光合作用中较轻的碳同位素的偏好的标准方法涉及Farquhar等人的模型,该模型将碳同位素的辨别力与叶片内的物理和生化过程相关。但是,在许多情况下,该模型对于叶肉电导率对CO 2扩散的返回不合理的结果(g m),尤其是在光合作用速率较低时。在这里,我们使用与线粒体呼吸作用的同位素效应相关的修改假设重新推导碳同位素判别模型。特别是,我们将与呼吸有关的碳库与主要同化物库分开对待。我们通过比较同位素组成不同的不同CO 2原料气测得的g m值,通过实验测试了该模型,并表明我们的新模型返回的匹配g m值比以前的模型更合理。我们用我们的结果来讨论叶肉内部的CO 2扩散特性。

更新日期:2020-03-09
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