The narrow-leafed campion is not a particularly long-lived flower; and yet, the parents of the campion pictured here blossomed in the presence of mammoths and woolly rhinos. How is that possible?
The explanation is simple, but the circumstances are unprecedented. The fruits that gave rise to the flowers you see here first fell to the Earth during the late Pleistocene. They were snatched up by a foraging squirrel, hidden underground, and subsequently entombed in ice. Now, more than 30,000 years later, the fruits have been revivified, giving rise to one of the most incredible biological anachronisms the world has ever known.
It's worth pointing out that ancient frozen seeds have been found before; they've even been grown into full-fledged plants. What makes this little arctic flower (which goes by the scientific name of Silene stenophylla) so impressive is just how old it is. Radiocarbon dating suggests that the fruit that generated this plant had been tucked away in the tundra of northeastern Siberia for 31,800 years. That blows the old record (previously held by a date palm seed) out of the water by around 30,000 years.
The fruit that gave rise to these flowers started its journey in the foraging paws of a Pleistocene-era squirrel. Squirrels like to hoard things — food, to be precise. This is as true today as it was 30,000 years ago. So when a research team led by David Gilichinsky decided to go foraging for the spoils of ancient squirrels along the banks of Russia's lower Kolyma river, they encountered no shortage of food stores; some of the burrows that the researchers raided contained upwards of 600,000 seeds and fruits.
These stockpiles have been preserved at around -7 degrees Celsius since they were first buried all those years ago; entombed by layer-upon-layer of permanently frozen soil, it's unlikely that these food stores thawed even once in the time between when they were first inhumed and when they were recovered by Gilinchinsky and his team.
Incredibly, when researcher Svetlana Yashina extracted the placentas from the recovered fruits, she was able to coax the tissue into producing roots and shoots. (The placenta is where the fruit's seeds attach and receive nutrients, labeled "P" in image A, and shown with attached seeds in image B.) She potted the plants and waited. One year later, flowers emerged. The plants bore fruit that set seed, and from those seeds a new generation of plants emerged. After more than 30,000 years, this ancient lineage had simply picked up right where it left off.
The researchers regard the discovery as compelling evidence for the existence of other, as-of-yet discovered biological anachronisms that may be locked away in layers of permanently frozen soil, which is thought to cover nearly one fifth of the Earth's surface. These naturally occurring fruit and seed stores, explain the authors, can be thought of as nature's version of man-made seed repositories, like Norway's Svalbard Global Seed vault, where researchers are working to amass a stockpile of the world's ever-dwindling plant diversity.
"Naturally occurring permanently frozen sediments offer an important opportunity for the discovery of wild plant species, preservation of biological material, studying the conditions for cryopreservation, and developing germplasm collections," write the researchers in today's issue of Proceedings of the National Academy of Sciencies.
"We consider it essential to continue permafrost studies in search of an ancient genetic pool, that of preexisting life, which hypothetically has long since vanished from the earth's surface."
Images by Yashina et al. via PNAS