Ordinarily, once a fern's leaf fronds have died, the plant has no further use for them. Such is not the case with the Cyathea rojasiana fern, though – a scientist has discovered that its dead fronds become "zombie leaves" which suck nutrients from the soil.
While studying another type of plant in a Panamanian forest reserve, the University of Illinois Urbana-Champaign's Prof. James Dalling and colleagues noticed something interesting about the Cyathea rojasiana tree ferns, which are only found in Panama.
When fronds of the plants died, wilted and drooped to the ground, the ends of those fronds grew tiny rootlets which connected them to the soil. Subsequent lab tests showed that when this happened, the plant reversed the flow of water in those fronds, using them to draw nitrogen from the earth.
So, why don't other plants employ this technique?
Well, since Cyathea rojasiana grows by no more than a few centimeters every year, and because nutrients are unevenly distributed in the area's soil, the plant has to make what growing it does do really count. Therefore, instead of putting energy into growing special nutrient-seeking rooting structures which may never reach fertile soil, Cyathea rojasiana just recycles the fronds that it already grew for performing photosynthesis.
This arrangement, in which a plant reconfigures its own dead tissue to feed itself, has never been previously documented. Dalling believes the reason that other scientists didn't notice it in Cyathea rojasiana before is simply because the fronds just look like decaying plant matter.
"This is a truly novel repurposing of tissue," he said. "And it’s distinct from what we know other ferns do."
The research is described in a paper that was recently published in the journal Ecology. There's more information in the following video.
