A new system for simultaneous measurement of photosynthesis and solar-induced fluorescence

Can solar-induced fluorescence be used to accurately estimate photosynthetic traits at different scales?

As the primary determinant of plant productivity, photosynthesis has long been regarded as a target for improvement in plant breeding programs. Yet while photosynthesis is relatively easy to measure directly at the leaf scale using portable gas exchange instruments, measurement at the field or ecosystem scale in such a manner is unfeasible. This has led to researchers investigating new less direct techniques that could allow for measurement of photosynthesis at a variety of scales.

Solar-induced chlorophyll fluorescence (SIF) is a promising tool to estimate photosynthesis remotely (i.e. from satellite) by measuring the fluoresced light from chlorophyll pigments of plants. However, the mechanistic relationship between SIF and photosynthesis remains unclear. 

(A) Side-view schematic of the of the modified LI-6800 leaf chamber plate with inserted spectrometer fibre-optic. (B) Top-view schematic of the modified plate, which highlights the orientation of the 1.5-mm drilled hole in reference to the temperature sensor hole. (C) Photo of the modified system with fibre-optic inserted into the leaf chamber. Image credit: Meeker et al.

In their recent paper in AoBP, Meeker et al. describe the modifications they made to two common gas exchange systems that allow them to measure SIF and photosynthesis simultaneously at the leaf-level. LI-COR LI-6800 and WALZ GFS-3000 gas exchange instruments were modified with a visible-near-infrared (VIS-NIR) spectrometer to measure active and passive fluorescence simultaneously. Whilst the WALZ system is limited mostly to in-lab use, the LI-COR system is highly portable and can be used in the field.

This new tool can be used to develop a deeper understanding between chlorophyll fluorescence and photosynthesis at different scales. Whilst the authors tested the system with just one plant species in this work, they hope that future research with these devices might look at multiple species aiming to advance the understanding of the biological mechanisms of SIF. Using this device in the field with concurrent tower-based measurements will also help to determine how suitable SIF is for the measurement of photosynthetic traits at the whole field and ecosystem scales.

This Tools article was published in the AoBP Special Issue entitled Solar-Induced Fluorescence: From the Leaf to Beyond the Canopy.

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