Chlorophyll fluorescence, the light from photosynthesis, illuminates our view of plant function
How much atmospheric carbon dioxide is assimilated by a forest via photosynthesis? What plant varieties are less sensitive to environmental stress induced by global change? Answering these questions could now be possible by observing chlorophyll fluorescence.

Chlorophyll, the green pigment found in plants and algae, emits faint red and far-red light when illuminated during photosynthesis. This so-called chlorophyll-a fluorescence conveys information about the instantaneous rate of photosynthesis, which provides an “optical window”  that tracks plant functional and health status.

Although methods to measure and interpret chlorophyll-a fluorescence at the leaf and subcellular levels have been around for decades, it is only recently that chlorophyll fluorescence (known as solar-induced fluorescence, SIF) can be estimated and imaged at the ecosystem and regional scales.

Cutting edge SIF measurements are conducted with hyperspectral optical sensors mounted on towers, drones, aircraft, and even satellites.  For example, the FLuorescence EXplorer (FLEX) satellite mission from the European Space Agency is scheduled for launch in 2024 and will provide global maps of SIF at a resolution of a few hundred meters.

These developments pave the way to multiple scientific and commercial applications in plant ecophysiology, ecology, biogeochemistry, as well as precision agriculture and forestry.

"Excitingly, SIF opens up spatial and 3D photosynthesis studies in the field. This will help to resolve long-standing research questions related to the photosynthetic dynamics of the different parts of a plant or ecosystem in real-world conditions. SIF can also be applied in physiological phenotyping and pre-visual stress detection, which is a powerful tool for next-generation forest and crop management practices," says Albert Porcar-Castell from the University of Helsinki.

To meet these ambitious goals, multiscale and multidisciplinary collaborative studies are required. Expertise from plant biology, remote sensing, agronomy and forestry should be fused to translate the information content of SIF into innovative applications capitalising on insight across the molecular, leaf and canopy scales. 

Article:

Albert Porcar-Castell, Zbyněk Malenovský, Troy Magney, Shari Van Wittenberghe, Beatriz Fernández-Marín, Fabienne Maignan, Yongguang Zhang, Kadmiel Maseyk, Jon Atherton, Loren P. Albert, Thomas Matthew Robson, Feng Zhao, Jose-Ignacio Garcia-Plazaola, Ingo Ensminger, Paulina A. Rajewicz, Steffen Grebe, Mikko Tikkanen, James R. Kellner, Janne A. Ihalainen, Uwe Rascher and Barry Logan. Chlorophyll-a fluorescence illuminates a path connecting plant molecular biology to Earth-system science. https://doi.org/10.1038/s41477-021-00980-4

Optics of Photosynthesis Lab
Institute for Atmospheric and Earth System research INAR
Viikki Plant Science Center ViPS