“Zombie Leaves” – Scientists have discovered that a unique species of tree fern defies death

“Zombie Leaves” – Scientists have discovered that a unique species of tree fern defies death

Cyathia rugasiana

Other plants, including some ferns, send out leaves or shoots that touch the ground and sprout roots to support a new plant. But the Panama tree fern, Cyathia rugasiana, reshapes “zombie leaves,” reflecting the flow of water to pull nutrients back into the plant. Credit: Drawing by Camilla Pisano, color by Michael Vincent

Plant biologists have discovered that this is unique Classify A tree fern, exclusive to Panama, that has the ability to regenerate its dying leaf fronds into root-like structures. This fern, known as Cyathia rugasianatransforms these “zombie leaves” by changing the direction of water flow, enabling them to absorb nutrients back to the main plant.

James Dalling, a professor of plant biology at the University of Illinois Urbana-Champaign, who made the discovery with his team while studying a different plant in a Panama forest reserve, said this strange phenomenon only occurs after the leaves die and drop to the ground. Daling noticed that the fronds were firmly embedded in the soil, and a network of small roots had sprouted. Laboratory tests revealed that the zombie leaves were pulling nitrogen from the soil.

Even after being turned into roots, the wilted fronds look like decaying plant matter, which is likely why generations of plant biologists failed to notice that they were serving a life-sustaining function, Daling said.

“It’s really a new reuse of tissue. It’s different from what we know about other ferns,” he said.

The uniqueness of Cyathea rojasiana

Other plants, including some ferns, send out leaves or shoots that touch the ground and sprout roots to support a new plant, he said. But reconstitution of dead tissue to nourish the parent plant has not been reported. The new findings are detailed in the journal Ecology.

C. rogasiana It belongs to an ancient lineage of tree ferns dating back to the Paleolithic period Jurassic Daling said. Zombie leaves are likely an adaptation to nutrient-poor volcanic soil.

Geological and environmental context

He said: “Panama is a land bridge between North and South America. It was united 7 million years ago from an archipelago of islands, and these islands are the result of volcanic activity in the past.” “At one of the sites we discovered, there was a layer of volcanic ash several meters deep, similar to the sand you would dig on a sandy beach. The plants growing there are different from those we find elsewhere in that forest reserve.”

James Dalling

University of Illinois Urbana-Champaign plant biology professor James Dalling and his colleagues have discovered that some tree ferns recycle their dead fronds into roots. Researchers call these reused fronds “zombie leaves.” Credit: Fred Zwicky

The patchiness of vegetation means that soil nutrients are also unevenly distributed.

“So the tree ferns appear to be sticking out tentacles to sample the surrounding soil,” Dalling said. “They’re able to sample a wider range of nutrient environments for the same amount of investment of young roots than if they just sent out a single rooting structure throughout the fern. I think it’s all about the economics of how they use resources in a patchy environment.”

Tree ferns also grow very slowly.

“They’re probably putting on one or two leaves a year, so they’re adding a few centimeters of height a year,” Dalling said.

This means that each frond represents a significant investment of resources that the plant reuses after the leaf dies. Slow growth also means that the tree fern is short enough that it will droop all the way down when its fronds die. Daling said the trees reach a maximum height of about two metres.

He said the discovery is “another example of the extraordinary diversity of plant adaptations found in resource-poor environments.”

Reference: “Zombie leaves: a new reuse of senescent fronds in the tree fern Cyathea rojasiana in a tropical montane forest” by James W. Dalling, Edilio Garcia, Carlos Espinoza, Camila Pisano, Astrid Ferrer, and Jessica Lira Viana, 18 January 2024, Ecology.
doi: 10.1002/ecy.4248

Daling is also a research associate at the Smithsonian Tropical Research Institute in Panama.

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