Thứ Sáu, 24 tháng 2, 2012

How scientists resurrected a 30,000-year-old flower

After successfully growing samples of ancient S. stenophylla in a lab, scientists may finally have a technique to recreate the woolly mammoth A few years ago in northeastern Siberia, Russian scientists uncovered a rare trove of immaculately frozen Arctic squirrel burrows dating back to the Ice Age. Inside they found buried seeds, including the fruit of a flower called the narrow-leafed campion. Now, after 30,000 years, they've brought the original flower back to life. Here's what you should know:

So they grew the flower from frozen seeds?
Not exactly. Efforts to resurrect ancient plants from seeds found "wonderfully preserved by the cold, dry environment" fell short, says Sharon Levy at Scientific American, including attempts to sprout sedge, alpine bearberry, and the narrow-leafed campion (known scientifically as Silene stenophylla). "Those seeds did begin to germinate, but then faltered and died back." Instead, the scientists, led by David Gilichinsky of the Russian Academy of Sciences, looked to tissue samples from S. stenophylla fruit — specifically, they turned to the plant's placenta (think of the white meat inside a bell pepper), which produces its seeds.

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Then what did they do?
After thawing out the organic material, they placed cells taken from the placenta into petri dishes. Scientists were delighted when these specimens grew into "whole plants," and were able to use those seeds to farm a second generation of flowers. The team was able to grow 36 narrow-leafed campion plants in all, and the specimens "appeared identically to the present day narrow-leafed campion until they flowered," says Nicholas Wade at The New York Times, "when they produced narrower and more splayed-out petals." 

How were the frozen seeds able to survive for so long?
Researchers think it may have something to do with the "special circumstances" of the campion's deep freeze. Squirrels bury their finds next to icy permafrost "to keep seeds cool during the arctic summers," meaning the fruits were frozen early on, notes Wade. Plus, the placentas contain "high levels of sucrose and phenols, which are good antifreeze agents." 

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Are these the oldest plants ever grown?
By far. The sediments surrounding the frozen seeds date back roughly 30,000 to 32,000 years. "If so, it would trounce the previous record held be a date palm from a 2,000-year-old seed recovered from Masada, Israel," says Tristin Hopper at National Post. 

What's next?
Scientists will use the techniques to produce more plants found in the Siberian burrows, but the same techniques could potentially be applied to woolly mammoths or saber toothed tigers. "We find partially-preserved mammoth carcasses in the Siberian tundra that are 30,000 years old," says paleontologist Grant Zazula. "This raises the potential that you could have viable sperm cells and eggs cells within some of these animals."

Sources: Associated Press, National Post, NY Times, Scientific American

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