Published August 09, 2021 by Tom Porter

Chlorophyll Fluorescence: Shedding Light on Global Climate Change

Chlorophyll is the green pigment found in plants that absorbs the light used to power photosynthesis, explains Barry Logan, Bowdoin’s Samuel S. Butcher Professor in the Natural Sciences. “Curiously, chlorophyll emits a tiny fraction of absorbed sun energy. That is, chlorophyll fluoresces.”

barry logan

In other words, says Logan, the earth’s vegetation glows, albeit so weakly that our eyes cannot detect it. “Our ability to measure this chlorophyll fluorescence has greatly expanded over the last decade. Scientists now report and analyze chlorophyll fluorescence intensities measured at scales ranging from portions of individual leaves to whole continents, using hand-held devices and instruments mounted to towers, drones, aircraft, and satellites.”

Gaining knowledge of the varying intensities of this process, says Logan, “has refined our understanding of the exchange of carbon between the biosphere and the atmosphere, thereby refining models of global change. It has sharpened our understanding of the response of vegetation to environmental stresses such as drought. Still,” he continues, “there is a great deal left to be learned about the forces affecting the strength of the chlorophyll fluorescence signal. For example, how do the branching patterns of trees and the resultant clumping of leaves affect fluorescence intensity? What is the relationship between the rate of photosynthesis of individual leaves and their fluorescence emission? These are among the many complexities not yet fully understood.”

Logan is part of an international team of authors behind a newly published article in Nature Plants, an article he describes as “an invitation to the plant science community to collaborate in an effort to realize the full potential of fluorescence measurements.” The article, he explains, emerged from a pre-pandemic workshop held at a forest research station in central Finland. “We summarize the current state of knowledge of chlorophyll fluorescence emission and propose a road map for resolving remaining scientific challenges, explicitly inviting plant molecular biologists, physiologists, ecologists, modelers, earth system scientists, and others, to join forces in a search for deeper understanding, more confident interpretation, and greater usefulness of measurements of this quirk of chlorophyll.”

Logan’s focus in the article, he says, was leaf-level physiology. “I also played a heavy role in harmonizing the narrative which integrates the contributions of specialists from a wide range of subdisciplines with diverse language backgrounds.”

Read the article

More useful links: two original research articles on the subject, coauthored by Logan.

From Geophysical Research Letters of the American Geophysical Union.

From PNAS (Proceedings of the National Academy of Sciences of the United States of America).