Researchers at the University of New Mexico have made an exciting discovery about the smooth horsetail plant, known scientifically as Equisetum laevigatum. This plant has existed for around 400 million years, dating back to the Devonian period. Their findings reveal that the plant can distill water in a remarkable way, causing its chemical signature to mimic that of meteorites.
Led by Professor Zachary Sharp, the team focused on how water travels up the horsetail’s segmented stems. As it rises, most of it evaporates through tiny pores, leaving behind heavy oxygen isotopes at the top. This intense natural distillation sheds light on long-standing mysteries in oxygen isotope data from modern desert plants and animals.
The horsetail functions like a well-engineered machine. It consists of hollow segments that feature rows of stomata—tiny pores that allow moisture to escape. Sharp describes it as “a meter-high cylinder with a million holes.” As the plant takes in water, it continuously loses moisture, changing the water’s chemical composition inside.
When water evaporates, lighter oxygen isotopes escape first. This leaves a concentrated pool of heavier isotopes, creating a unique chemical signature that could illuminate ancient environments. Researchers recently discovered that the water at the plant’s tip contained isotopic values that had never been seen before in terrestrial materials. Sharp remarked, “If I found this sample, I would say this is from a meteorite.”
This discovery not only clarifies modern desert ecology but also provides a window into Earth’s past. Ancient horsetail ancestors grew as large as 30 meters tall. They stored water in solid, glassy structures called phytoliths, which trap isotopic information. These phytoliths survive for millions of years in the fossil record, acting as time capsules of past climates.
By measuring the isotopes in these plants, scientists can now reconstruct humidity levels from millions of years ago. With improved models, researchers can better understand how climate conditions changed over time, especially during the era of dinosaurs. This opens up exciting avenues for studying ancient ecosystems.
As Sharp explains, “We can use this as a palaeo-hygrometer, which is pretty cool.” He adds that while researchers must consider that these phytoliths represent averages over time and not instantaneous conditions, this discovery gives us a powerful tool for delving back into Earth’s climate history.
The full findings are published in the journal PNAS here.
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