Jennifer Schultz Nelson
Extension Educator, Horticulture
Looking out at three foot high snow drifts against my house this week, I was at a loss to come up with a topic for my column. For me, snowstorms after January are an unnecessary delay of Spring. The white wasteland in my backyard makes me wonder if life really is lurking in the ground, waiting for the weather to break.
It occurred to me that one of the plants I have is a great demonstration of how life can bounce back despite appearances that suggest otherwise. A friend of mine had one years ago, and it was so fascinating that when I saw one for sale last year, it just had to come home with me.
The plant that caught my interest was the resurrection fern, Pleopeltis polypodioides. It doesn't look like much, just a little cluster of brown, dead looking leaves. But place it in a shallow dish of water, and overnight, like magic, the leaves unfurl, and become green. Take it out of the water, and as it dries it reverts to the dead looking tuft of leaves again.
The resurrection fern is native to parts of Africa and the Americas. It is a true marvel of the plant world, not just a novelty item as it is often sold as.
Most plants can only tolerate about a 10% loss of water from their cells before the plant dies. In human terms, we can lose only about 20% of our body's water before death occurs. The resurrection fern has evolved to be able to tolerate losing up to 97% of its water and somehow manages to remain alive. During a "typical" dry period, it will lose around 75% of its water, which is still a phenomenal feat no matter who you are.
Some experts have estimated that the resurrection fern can exist in it's nearly completely dry state for at least 100 years. Researchers speculate that the resurrection fern's ability to tolerate such incredible levels of dehydration gives them an evolutionary advantage, because they will be able to survive an extended drought period long after their neighbors have succumbed to the lack of water.
Resurrection ferns are true ferns. They reproduce via spores rather than seeds. The spores develop in structures called sporangia on the underside of the leaves arranged in clusters called sori. The sori on the resurrection fern look like round depressed areas, and at maturity are typically dark in color.
Unlike most other ferns, resurrection ferns are epiphytic, meaning they attach to another living species and collect water and nutrients that collect on the surface where they are attached. Another common name for this type of plant is "air plant".
They are in no way stealing nutrients from their host plants. Like other epiphytes such as Spanish moss and some orchids, the host plant is only a point of attachment, and gives the epiphyte a better position for absorbing water and nutrients from the environment.
The host plant of choice for resurrection ferns is living trees. They use a creeping rhizome to attach themselves, and often occur in great numbers in nature.
I wrongly assumed that resurrection ferns were native only to tropical climates. On the contrary, the subspecies that naturally occurs in North America, michauxiana, also called Weatherby, lives not only in Florida and west to Texas, but also can be found as far north as New York. The USDA lists this subspecies as being found in the southernmost counties of Illinois.
Resurrection fern's ability to withstand extended periods without water may have an interesting application in modern life, specifically space travel.
One limitation to doing biological experiments in space is that specimens need to survive being loaded for a flight and held in less than optimum conditions for extended periods of time before liftoff. As part of ongoing research on biological experiment systems in space, middle school students in South Carolina nominated the Resurrection Fern as a hardy candidate for space travel.
Students at the Medical University of South Carolina designed an experiment measuring chlorophyll fluorescence (the green pigment in plants responsible for photosynthesis) to assess how resurrection ferns revived in space. In 1997, resurrection ferns earned the title of "first fern in space" on the Space Shuttle Discovery.