In an old greenhouse tucked behind the biology building at the University of Tennessee Knoxville, you will find two 20-foot-long tables filled with rectangular plastic trays of water. Sitting in these trays are tall, Kelly-green, grass-like plants that wave cheerily in the very slight breeze that passes through the greenhouse to keep it cool in the summer. In a way, the plants are zombies.
I’m the one who brought them back from the dead.
With help from a small team of researchers, I resurrected them from the dormant seeds of a common coastal wetland plant, Olney’s bulrush, which drops seeds into the mud, where they lie dormant. Why bring them back from the brink of death? Because, as we’ve written in a paper in Evolutionary Applications, these plants are the first line of defense against coastal climate change. Olney’s bulrush (Schoenoplectus americanus) is a coastal wetland plant that plays a vital role in helping sediment to collect along coasts, building land that counteracts the action of erosion. You’ll find Olney’s bulrush all across the Atlantic and Gulf coasts of the US, quietly resisting the ocean’s tides and waves.
Olney’s bulrush is an old favorite for global change researchers (it’s common and important in marsh ecology), but my paper and the project it described is the first to dig up the plant’s seeds from the soil where they’re stored. I use the term “zombie,” although the seeds we germinate were never dead, just dormant. Olney’s bulrush has the distinction of producing very durable, miniscule seeds—they are remarkable! Some germinate, but some are buried in the ground where, despite harsh conditions that include salty water, tides, and microbes trying to break them down, these seeds persist in the sediment for 100 years or more. Why they do this, we aren’t sure. Crazier still, those 100-year-old seeds can actually germinate.
And we can learn a lot from hundred-year-old seeds.
I am part of a larger project that aims to understand the evolutionary past, present, and future of this hardy wetland plant. They serve as ambassadors of long-dead historic populations, providing us with insight into their mysterious lives. And there are at least three incredible outcomes from listening to what these plants have to tell us.
First, because we can grow 100-year-old plants alongside their descendants, we can figure out if our they can evolve over the course of a few decades rather than millions of years—the traditional timeline for evolution. That means we can improve models and predictions of how wetlands will fare in the future by showing how important evolution and adaptation might be in shaping our coastlines. Spoiler alert: in the paper linked above, we found evidence for evolution after just 100 years!
Second, seed banks are a relatively underutilized resource in science. Our paper and the project can really help demonstrate just how useful seed banks can be. Maybe in the future, more scientists can search for the Olney’s bulrush of other critical habitats and use them to understand how the future might unfold.
Third, we want to ask questions about just what might be the major environmental pressures that stress our plant out. Right now we want to know some basics. Were they competent at dealing with sea level rise? Did they thrive in highly saline environments, or pale and wither in the presence of high levels of salt? With any luck, we’ll know soon.
There’s an old adage that “those who cannot remember the past are condemned to repeat it.” By studying how this plant adapted to crazy environmental in the past (think about major pollution from the Industrial Revolution), we can better understand its evolutionary potential to respond to sudden and violent global change in the future.
I’m going to put these zombie plants to work.