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Modification of a gas exchange system to measure active and passive chlorophyll fluorescence simultaneously under field conditions
AoB Plants ( IF 2.9 ) Pub Date : 2020-12-06 , DOI: 10.1093/aobpla/plaa066
Eliot W Meeker 1 , Troy S Magney 2 , Nicolas Bambach 3 , Mina Momayyezi 4 , Andrew J McElrone 4, 5
Affiliation  

Solar-induced fluorescence (SIF) is a promising tool to estimate photosynthesis across scales; however, there has been limited research done at the leaf level to investigate the relationship between SIF and photosynthesis. To help bridge this gap, a LI-COR LI-6800 gas exchange instrument was modified with a visible-near-infrared (VIS-NIR) spectrometer to measure active and passive fluorescence simultaneously. The system was adapted by drilling a hole into the bottom plate of the leaf chamber and inserting a fibre-optic to measure passive steady-state fluorescence (Ft,λ, analogous to SIF) from the abaxial surface of a leaf. This new modification can concurrently measure gas exchange, passive fluorescence and active fluorescence over the same leaf area and will allow researchers to measure leaf-level Ft,λ in the field to validate tower-based and satellite measurements. To test the modified instrument, measurements were performed on leaves of well-watered and water-stressed walnut plants at three light levels and a constant air temperature. Measurements on these same plants were also conducted using a similarly modified Walz GFS-3000 gas exchange instrument to compare results. We found a positive linear correlation between Ft,λ measurements from the modified LI-6800 and GFS-3000 instruments. We also report a positive linear relationship between Ft,λ and normalized steady-state chlorophyll fluorescence (Ft/Fo) from the pulse-amplitude modulation (PAM) fluorometer of the LI-6800 system. Accordingly, this modification will inform the link between spectrally resolved Ft,λ and gas exchange—leading to improved interpretation of how remotely sensed SIF tracks changes in the light reactions of photosynthesis.

中文翻译:

在野外条件下同时测量主动和被动叶绿素荧光的气体交换系统的改进

太阳诱导荧光 (SIF) 是估计跨尺度光合作用的有前途的工具;然而,在叶片水平上对 SIF 与光合作用之间的关系进行的研究非常有限。为了帮助弥合这一差距,LI-COR LI-6800 气体交换仪器使用可见-近红外 (VIS-NIR) 光谱仪进行了改进,以同时测量主动和被动荧光。该系统通过在叶室底板上钻孔并插入光纤来测量被动稳态荧光(F tλ,类似于 SIF)来自叶子的背面。这种新的改进可以同时测量同一叶面积上的气体交换、被动荧光和主动荧光,并将允许研究人员在现场测量叶级F tλ以验证基于塔的测量和卫星测量。为了测试改进后的仪器,在三个光照水平和恒定空气温度下对浇水充足和水分胁迫的核桃植物的叶子进行了测量。还使用类似改进的 Walz GFS-3000 气体交换仪器对这些相同的工厂进行了测量,以比较结果。我们发现F t , λ之间呈正线性相关来自改良的 LI-6800 和 GFS-3000 仪器的测量结果。我们还报告了F tλ与来自 LI-6800 系统的脉冲幅度调制 (PAM) 荧光计的归一化稳态叶绿素荧光 ( F t / F o )之间的正线性关系。因此,本变形例将通知光谱分辨之间的链路˚Fλ和气体交换导致改进的光合作用的光反应如何遥感SIF轨道变化的解释。
更新日期:2021-01-29
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