The mystery of the “zombie” fern

In the rainforests of western Panama, plant biologist Jim Dalling came across tree ferns with 6-foot-long fronds that bent to the ground when they died, wrapping around the plant like a skirt.

“I was trying to get these things out of the way and then I realized they were rooted in the ground,” Dalling said.

A professor and forest ecologist at the University of Illinois, he sought a a completely foreign plant.

The rest of the fern fronds were brown and withered, dead to the eye (although still attached to the trunk of the tree fern).

He asked himself: How could inanimate plant matter take root?

“I really couldn’t believe what I was seeing,” Dalling said.

A more detailed study revealed that this tree fern, the so-called Cyathea rojasianait transforms the inner part of its dead or dying leaves.

Remains of xylem and phloem (tubules that transport water, sugars and nutrients through living leaves) somehow They become the root.

From the tips of these leaves, nicknamed “zombie leavesThey then sprout new fine roots and penetrate the soil, said Dalling, co-author of a study describing the findings published in January in the journal Ecology.

In the process of transmutation of the central vein of the leaf, the plant undergoes proliferation new vascular tissue and prevents it from rotting while the rest of the leaf wilts.

“This is completely unknown in any other factory in the world,” he said.

“Normally, vascular tissue is deposited on the leaf and that’s it,” said Robbin Moran, a fern expert and curator emeritus at the New York Botanical Garden in the Bronx.

But in this species, after the rest of the leaf dies, it “begins to differentiate, to proliferate. “I don’t know how it’s going to happen.”

“I’ve never seen anything like it,” added Moran, who was not involved with the paper.

This tree fern is found in a humid area Fortuna Forest Reservewhere it rains more than 6 meters per year.

The rain leaches the sandy and volcanic soil, removal of nitrogen and phosphorus.

Scientists believe that the fern’s adaptation allows it to take advantage of pockets of nutrients in nearby topsoil that it would otherwise be unable to access.

Many plants are known for their almost unlimited adaptability, and other species can produce new roots from living leaves.

Notable examples include the walking fern (Asplenium rhizophyllum), native to the United States, which reproduces on mossy rocks using this technique.

But the tree fern’s “zombie leaves,” or leaf roots, represent the first known example of the reuse of dying tissue, said Eddie Watkins, a professor and fern expert at Colgate University who was not involved in the study.

By turning existing leaf material into roots, the plant is most likely to conserve energy, Watkins suggested.

This might help you in “struggle for nutrients in its part of the rainforest.

The heavy rainfall and poor soils provide a unique assemblage of plants, including a conifer known as Podocarpus, which is Greek for “footed fruit” (a reference to the stem-like appearance of another species in the genus).

This evergreen tree sends out strange bulbous roots everywhere, even into the trunks of nearby trees.

The conifer was what led Dalling to dig through the undergrowth in the first place.

“It’s pure coincidence that we were digging at the base of these tree ferns,” he said.

Dalling examined dozens of these ferns and found that each one was growing roots from its “zombie leaves.”

But his work was interrupted by the coronavirus pandemic, which forced him to leave Panama with his wife and dog and return to Illinois in February 2020.

He returned two years later.

Dalling and his colleagues dug roots from the leaves of three individual plants, placed them in pots, and added a chemically labeled nitrogen fertilizer.

A month later, they examined the new leaves at the top of the fern and found that nitrogen had indeed been incorporated into the plant, confirming that these roots were actively transport water and nutrients.

Much remains to be known, including essentially all of the biochemical and developmental mysteries of how this particular tree fern achieves such a transformative feat.

The discovery speaks to the importance of spending time studying and appreciating the natural world, Watkins said, adding that this type of exploration has become less frequent and financially demanding.

“If you stop and look at the organism, there are really new and interesting things,” Watkins said.

“We can tell stories we haven’t discovered.”

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