Frozen mosses that were buried under glaciers 400 years ago have now been regrown. Surprisingly, the hardy "bryophytes" required no special techniques to regenerate. That means they might be candidates for colonizing extreme environments — even in space.
During the Little Ice Age, which occured between the 16th and 19th centuries, massive glaciers moved in and covered various regions in the Northern Hemisphere. These glaciers slowly retreated throughout the 20th century, and the rate of ice melt has sharply accelerated since 2004.
The substantial glacial retreat is now revealing beautifully preserved vegetative communities, says Catherine La Farge, a bryophyte botanist at the University of Alberta. "It's kind of like a blanket being pulled back, allowing you to see what the Little Ice Age was like."
Bryophytes are non-vascular plants, such as mosses, hornworts and liverworts, that don't produce flowers or seeds; instead, they reproduce asexually using spores. Additionally, they can experience clonal growth and produce a new plant from fragmented vegetative tissue that has fallen off the primary plant. Though they're not the preferred food source for herbivores, they're still an important part of the ecosystem, providing homes for micro-flora and fauna. For example, in the frigid, dry arctic, cyanobacteria and fungi utilize moss cushions as their habitat, while the seeds of vascular plants that fall into moss beds can germinate using the moisture trapped there.
As part of an environmental project looking at the effects of pollution in the arctic, La Farge and her colleagues took a trip in 2007 to Sverdrup Pass, a mountain pass in central Ellesmere Island, Nunavut, Canada, to study the diversity of bryophytes in the area. While there, they saw extensive populations of bryophytes and vascular plants coming out of the nearby receding Teardrop Glacier.
The Teardrop Glacier, with puny human for scale.
"We walked up to the glacier and looked at the populations of bryophytes," La Farge tells io9. "They looked blackened, but they were blackened with a green tint." The exhumed plants appeared to be regrowing, despite being for frozen for presumably hundreds of years, so the researchers collected samples and took them back to their lab for further examination.
Radio carbon dating confirmed that the bryophytes were entombed in the glacier during the Little Ice Age some 400 years ago. And when the team looked at their samples under microscopes, they saw that the plants were indeed experiencing new lateral branch development or stem regeneration. They then decided to take fragments of the plants and test their capacity for regrowth.
The team ground up stem and leaf tissue, sowed it on potting soil and watered it frequently. Using this simple technique, they were able to grow 11 cultures from seven specimens, which represented four different species (Aulacomnium turgidum, Distichium capillaceum, Encalypta procera and Syntrichia ruralis).
The researchers note that these bryophytes aren't the oldest frozen plants to be regenerated — that title goes to a 32,000-year-old Silene stenophylla specimen. However, S. stenophylla's regrowth was far more complicated, requiring scientists to extract placental tissue from seeds, carefully clone the tissue and then grow them on specialized, nutrient-rich media.
La Farge hopes that the work will stimulate renewed interest in bryophytes, which aren't widely studied by botanists. "I think the whole biological system of bryophytes has not really been understood well," she says. But from her study and others, it appears that bryophytes are able to shut down during desiccation and revive when conditions improve. The plants regenerative powers are partly due to their cells' ability to dedifferentiate (lose their specialized function) and return to a stem-cell-like state, allowing them to then become any type of plant cell.
The results of the study suggest that landscapes exposed by retreating ice should no longer be thought of as being barren of land plants. Bryophytes likely play an important role in the establishment, colonization and maintenance of polar ecosystems, the researchers write in their study.
The retreating glacier reveals frozen bryophytes.
"These guys are really adept in extreme environments," La Farge says, adding that the research's implications go beyond just Little Ice Age ecosystems. By further studying bryophyte regeneration, scientists can get a better understanding of "basic life systems," including, perhaps, how to promote biological development in extraterrestrial environments, such as Mars.
Scientists have already taken moss up into space to see how it grows in a micro-gravitational environment. "Maybe astronauts would want to take bryophytes to other planets to see if they would grow and how they could modify extraterrestrial landscapes," La Farge says.
The research was published in the journal PNAS.
Images courtesy of Catherine La Farge.