Fluorescent Evergreen Glow Tells When Trees Are Taking Up Carbon | Sierra Club
Decades ago, researchers realized that chlorophyll gives off a tiny, difficult-to-detect fluorescent glow. When sunlight hits chlorophyll—the green pigment that produces energy in most plants—it bumps it into an excited energy state. When the chlorophyll returns to its normal state, it emits 2 to 4 percent of that energy as a photon, or light particle, in the red and far-red light wavelengths. The glow is called solar-induced fluorescence (SIF) and, though not visible to the naked eye, it can be picked up by spectrometers, sensitive instruments that detect wavelengths of light.
In 2011, researchers first used satellite data to measure plant fluorescence, but scientists are still figuring out what the glow actually means. “Because they’re always green, it’s harder to know when photosynthesis might ramp up and when it might ramp down in evergreens,” says Troy Magney of the California Institute of Technology and NASA’s Jet Propulsion Laboratory, first author of the new study in The Proceedings of the National Academy of Sciences. “Beyond that, the typical remote sensing techniques we use to look at evergreen species basically just measure the amount of reflected radiation in the near infrared and red spectrum, which really just tells us how much green stuff there is. But we really don’t know what that green stuff is doing. We have no idea when they start photosynthesis and how much carbon they take up.”