Seeds buried for centuries in the permafrost of the arctic tundra could help save plant varieties threatened by extinction and provide “living fossils” to study plant evolution.
“It’s a logical environment to look for very old seeds that are viable,” said James B. McGraw, a biologist at West Virginia University. “The permafrost soil buries the seeds, insulates them and keeps them frozen. No bacteria, predators or fungi can get at them. They’re really protected.”
McGraw has spent the last two summers digging up the dry, frozen dirt beneath a hillside about 100 miles northeast of Fairbanks, Alaska, hoping to find seeds still alive after thousands of years.
Seeds from the early 1800s have yielded grass-like plants called reeds and rushes, and McGraw is eager to see what grows in soil estimated to be between 1,500 and 2,000 years old uncovered during his latest dig. “We won’t know exactly what we have until we have the samples carbon-dated. We may find something, we may not. But there are hints that we may.”
The dating process will not be completed until spring.
Scientists have known since the early 1970s that some seeds can stay viable for hundreds of years under the right conditions. A 600-year-old seed found in a nutshell rattle and germinated in 1971 is the oldest known seed to sprout.
Knowing how long seeds can stay viable could help improve storage in seed banks where the government preserves thousands of crop varieties. Thousands of irreplaceable seeds die annually in under-funded, antiquated seed banks.
The research also could help uncover a genetic trait for hardiness that could be transferred to crops grown in the harsh conditions found in some Third World countries, McGraw said. “We have found significant differences between our older seeds and younger seeds that appear to be genetic, but we won’t be sure until we complete our DNA analysis.
“There have been no major surprises yet, but we’ve looked at only 100 samples gathered last year. We have five times that many this year.”
McGraw and his crew of volunteers used only picks and shovels to dig a trench through a 5-foot layer of clay, called a lobe, to reach the seed-bearing layer of organic material. No mechanized equipment was used because of the damage it would have caused to the delicate tundra environment.
The samples were put in plastic bags, kept frozen in large coolers and shipped to Morgantown where they were transfered to dozens of trays, watered and kept under lights 20 hours a day to simulate the arctic summer.
“We put them under ideal germinating conditions and basically just see if anything grows,” McGraw said. “It’s the most efficient way to look for seeds because they’re so small and hard to find.”
Once the plants sprout, McGraw removes the seed cover from the root, and the seed’s age is determined through carbon dating--measuring the amount of naturally radioactive carbon remaining in the material.
He then uses the “living fossils” to compare the structure, growth rates and other characteristics of plants grown from old seeds and those existing on the tundra. “We’ve got some seeds that are nearly 200 years old and they are genetically different from the modern day seed and that’s interesting,” he said.
“But it will be even more interesting when we have seeds that are 1,000 or 2,000 years old and can measure their evolutionary development.
“We’re not there yet, but we’re closer.”
McGraw hopes to collect samples old enough to test theories of evolution.
“Current evolutionary theory tells us that natural selection should keep improving the genotype of the plant,” he said. “If that’s true, then the older types shouldn’t stand a chance against the more recent plants.
“We’ll soon be able to check that.”