The Shapeshifting Tree
By: Pempem Dorji
Have you ever wondered how fascinating plant adaptations emerge? Commonly studied peculiarities such as the monkey-like faces of Dracula simia orchids or the carnivorous nature of Venus flytrap plants may immediately come to mind. Recently, though, researchers have discovered an astonishing shape-shifting mechanism in a lesser-known fern, nicknamed the “Green Zombie,” found in southern, subtropical temperate forests. James Dalling, a plant biologist at the University of Illinois at Urbana-Champaign, has spent the last fifteen years studying plants in the Fortuna forest reserve of Western Panama. Recently, Dalling and his team discovered a unique mechanism used by a short tropical fern native to the region called Cyathea rojasiana. The mechanism enables C. rojasiana to reanimate its senescent leaves — leaves whose cells have stopped dividing and are in the process of dying — to function as root structures for the plant.
Dalling has studied Panamanian plants for thirty years, and his team unexpectedly stumbled upon this discovery while investigating the peculiar composition of plant species in the reserve. “We were digging around for roots, and these dead leaves of the tree ferns kept getting in the way,” Dalling said. “We kept trying to brush them away, but in the process, we discovered that these dead leaves were rooted in the soil.”
While it was initially thought that C. rojaisiana grows in locations all around the forest reserve, fern specialists later concluded that C. rojaisiana is endemic only to an extremely infertile patch of forest with significantly lower concentrations of nitrogen and phosphorus. The special characteristics of this patch of land may provide some explanation for the unique evolutionary adaptation of the shape-shifting leaves. “It’s this lack of nutrients which has created this selective force for this adaptation,” Dalling said.
In response to the lack of nutrients, the tree fern evolved an efficient system for gathering nutrients needed for growth by repurposing its aging parts. “These roots from leaves […] are like tentacles, being placed out into the forest floor surrounding the fern,” Dalling said. “There is a lot of spine scale spatial heterogeneity in the availability of nutrients.” Spine scale spatial heterogeneity refers to an uneven distribution of fern spines along a plant within the population, and each plant has its own unique spine distribution. This creates an economically advantageous system of sampling different patches of soil and optimizing the extraction of nutrients over a broader range of land.
Another advantage to this unique mechanism is the ability to repurpose existing tissue for reanimation into roots. “With plants we talk about nutrient use sufficiency, [or] how much can they grow per unit investment of nutrients,” Dalling said. Repurposing existing tissue, as opposed to growing new tissue, saves the plant from investing precious nutrients.
This novel process opens up a host of questions in the ecological community. “This is something we have never observed before,” Dalling said. Such unprecedented findings could facilitate the expansion of the boundaries of our understanding of plant adaptive traits. This nutrient-uptaking adaptation may even become relevant to human life, as we confront the ever-increasing dangers of diminishing nutrient resources in agriculture, especially phosphorous deficiencies. Strategies used by C. rojaisiana to conserve nutrients could perhaps be engineered into crops, making them more efficient in their consumption of critical nutrients. Studying the extraordinary mechanisms through which plants, such as the C. rojaisiana fern, adapt to nutrient-scarce environments has the potential to not only reveal their evolutionary past but also create a more sustainable future.
