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A Glow From Tree Leaves, Invisible To Humans, Can Be Used To Track Photosynthesis

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A new technique that tracks fluorescence in the far-red spectrum found strong correlation between fluorescence and photosynthesis.

Research tells us that early springs can offset the impacts of climate change. The earlier green-up makes for a longer growing season, and more carbon dioxide captured from the atmosphere. But we haven’t been able to tell if spring is coming earlier for conifers in the mountains – until now.

Researchers at NASA and the University of Utah recently announced they were able to apply a new technique called “solar-induced fluorescence” to track how much conifers photosynthesize.

“Conifer forests are always green, but they’re not always photosynthesizing. The traditional measures for plant activity are focused on greenness, so we’ve not been able to ascertain how fast evergreen forests have responded to climate warming. This solar-induced fluorescence allows us to monitor when photosynthesis is occurring,” said Dr. David Bowling, a professor of forest ecology at the University of Utah.

Before the application of solar-induced fluorescence, scientists tracked photosynthesis by setting up atmospheric towers that measured the flux of carbon dioxide, but these towers can’t be set up on complex terrains. The new technique could be applied from satellites, because it doesn’t track the flux of CO2. It tracks the emission of far-red light from photosynthesizing plants.

“Plants absorb sunlight energy with a pigment called chlorophyll,” Bowling said. “Naturally about 2-4% of the sunlight that is absorbed by chlorophyll is just reemitted as fluorescence in the far-red regions of the visible spectrum. This is just a byproduct of a not perfectly efficient photosynthetic system.”

Although this study only took place over two years, Bowling thinks that in the future the new technique could tell us if conifers come out of dormancy and start photosynthesizing earlier in the spring as a result of climate change.