Abstract：
Stable carbon isotopes are a powerful tool to study photosynthesis. Initial applications consisted of determining isotope ratios of plant biomass using mass spectrometry. Subsequently, theoretical models relating C isotope values to gas exchange characteristics were introduced and tested against instantaneous online measurements of 13C photosynthetic discrimination. Beginning in the twenty-first century, laser absorption spectroscopes with sufficient precision for determining isotope mixing ratios became commercially available. This has allowed collection of large data sets at lower cost and with unprecedented temporal resolution. More data and accompanying knowledge have permitted refinement of 13C discrimination model equations, but often at the expense of increased model complexity and difficult parametrization. This chapter describes instantaneous online measurements of 13C photosynthetic discrimination, provides recommendations for experimental setup, and presents a thorough compilation of equations available to researchers. We update our previous 2018 version of this chapter by including recently improved descriptions of (photo)respiratory processes and associated fractionations. We discuss the capabilities and limitations of the diverse 13C discrimination model equations and provide guidance for selecting the model complexity needed for different applications.
摘要：
稳定的碳同位素是研究光合作用的有力工具。最初的应用包括使用质谱法确定植物生物量的同位素比率。随后，引入了将C同位素值与气体交换特性相关的理论模型，并针对13C光合作用的瞬时在线测量进行了测试。从二十一世纪开始，激光吸收光谱仪具有足够的精度来确定同位素混合比成为市售。这允许以更低的成本和前所未有的时间分辨率收集大数据集。更多的数据和伴随的知识允许完善13C判别模型方程，但通常以增加模型复杂性和困难的参数化为代价。本章介绍了13C光合鉴别的瞬时在线测量，为实验设置提供建议，并提供了研究人员可用的方程式的全面汇编。我们更新了本章的2018年版本，包括最近改进的（照片）呼吸过程和相关分馏的描述。我们讨论了各种13C判别模型方程的功能和局限性，并为选择不同应用所需的模型复杂性提供了指导。
