Fluorescent Evergreen Glow Tells When Trees Are Taking Up Carbon

Researchers are learning how to interpret the faint light given off by the trees It’s pretty simple to tell when deciduous trees are photosynthesizing—their leaves are green. When that process is over for the year, the foliage shrivels up, turns brown, and falls off, an event so widespread it can be tracked by satellites in space. But tracking when evergreen trees crank up their chloroplasts and begin turning sunlight and CO2 into energy is much more difficult since, as their name implies, they stay green year-round (the trees actually stop photosynthesizing in the autumn but use a green pigment as a type of sunblock, keeping them green year-round). That has been a problem when it comes to climate modeling, which currently relies on estimates to determine how much CO2 evergreen forests pull out of the atmosphere. But a new study suggests there’s another way to keep tabs on photosynthesis in evergreen forests: watching their fluorescent glow from space. 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 […]

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