The European Space Agency’s Fluorescence Explorer satellite mission is scheduled for launch in 2024 to provide global Solar-induced Fluorescence maps


How much atmospheric carbon dioxide does a forest absorb through photosynthesis? Which plant varieties are less sensitive to global change? It may now be possible to answer these questions by observing the fluorescence of chlorophyll.

Chlorophyll, the green pigment used by plants and algae to capture sunlight, emits a subdued, red light during photosynthesis. This so-called “chlorophyll fluorescence”, invisible to the human eye, conveys information about the instantaneous rate of photosynthesis, thus providing an “optical window” that tracks the plant’s health and functional status. The journal Nature Plants published an article on the subject entitled ‘Chlorophyll a fluorescence illuminates a path connecting plant molecular biology to Earth-system science’, in which José Ignacio García-Plazaola of the Ekofisko research group in the Department of Plant Biology and Ecology at the UPV/EHU has participated.

Although various manipulative methods that allow chlorophyll fluorescence in a leaf or at the subcellular level to be measured and interpreted have been known for decades, it has only recently been possible on ecosystem and regional scales to calculate and image chlorophyll fluorescence that has been directly induced by sunlight (SIF-Solar-induced Fluorescence).

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

These developments are paving the way for a whole range of scientific and commercial applications in plant ecophysiology, ecology, biogeochemistry, as well as in precision agriculture and forestry.

“These tools are opening the door to conducting spatial and 3D photosynthesis studies in the field, which will help solve questions related to the photosynthetic dynamics of different parts of a plant or ecosystem under real-world conditions. SIF can also be applied in physiological phenotyping and pre-visual stress detection, which is a powerful tool for next-generation crop and forest management practices,” explained José Ignacio García-Plazaola.

To meet these ambitious goals, collaborative multidisciplinary studies that are also multi-scale are required. Expertise from plant biology, remote sensing, agronomy and forestry must merge to translate the information content of SIF into innovative applications that take advantage of knowledge across molecular, foliar and canopy scales.

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