Polypodium Polypodioides
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''Pleopeltis polypodioides'' (syn. ''Polypodium polypodioides''), also known as the resurrection fern, is a
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
of creeping, coarse-textured
fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except t ...
native to the
Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. Along with th ...
and
Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
.


Description

The evergreen
frond A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the lar ...
s of this fern are 25 cm high by 5 cm wide and monomorphic. The leathery, yellow-green pinnae (leaflets) are deeply pinnatifid, oblong to narrowly lanceolate, usually widest near middle, occasionally at or near base. It attaches to the limbs of its host plant with a branching, creeping, slender
rhizome In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...
, which grows to 2 mm in diameter. The scales are lanceolate, with light brown base and margins, and having a dark central stripe. The
gametophyte A gametophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has on ...
s (the
haploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...
gamete producers) of this plant develop from very small
spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...
s that float in the air and are deposited on moist tree branches. These spores are produced in
sporangia A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cy ...
that develop on the leaves of the fern's
sporophyte A sporophyte () is the diploid multicellular stage in the life cycle of a plant or alga which produces asexual spores. This stage alternates with a multicellular haploid gametophyte phase. Life cycle The sporophyte develops from the zygote pr ...
. The fern can also reproduce by the division of its
rhizome In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...
s. On the underside of the blades, the sori (reproductive clusters) are round, discrete, and sunken. Their outline can be seen as raised dimples on the upper surface. They are typically near the outer edge, and occur on all but the lowest pinnae of fertile fronds. Indusium is absent. Sporangia are yellow to brown at maturity. Spores are produced from summer to fall.


Habitat

This fern is an
epiphyte An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphytes grow are called phoroph ...
, or air plant, which means it attaches itself to other plants and gets its
nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...
s from the air and from water and nutrients that collect on the outer surface of
bark Bark may refer to: * Bark (botany), an outer layer of a woody plant such as a tree or stick * Bark (sound), a vocalization of some animals (which is commonly the dog) Places * Bark, Germany * Bark, Warmian-Masurian Voivodeship, Poland Arts, ...
. The resurrection fern lives on the branches of large trees such as
cypresses Cypress is a common name for various coniferous trees or shrubs of northern temperate regions that belong to the family Cupressaceae. The word ''cypress'' is derived from Old French ''cipres'', which was imported from Latin ''cypressus'', the la ...
and can often be seen carpeting the shady areas on limbs of large
oak An oak is a tree or shrub in the genus ''Quercus'' (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably ''L ...
trees repeatedly exposed to rainfall. However, it is known to grow on the surfaces of rocks and dead logs as well. It is often found in the company of other epiphytic plants such as
Spanish moss Spanish moss (''Tillandsia usneoides'') is an epiphytic flowering plant that often grows upon large trees in tropical and subtropical climates. It is native to much of Mexico, Bermuda, the Bahamas, Central America, South America, the Southern Uni ...
. The ''P. polypodioides'' resides in the
hardwood forests Temperate broadleaf and mixed forest is a temperate climate terrestrial habitat type defined by the World Wide Fund for Nature, with broadleaf tree ecoregions, and with conifer and broadleaf tree mixed coniferous forest ecoregions. These f ...
of southeastern United States in areas including Delaware, Maryland, the Carolinas, Virginia, West Virginia, Illinois, Ohio, Alabama, Georgia, Florida, Mississippi, Arkansas, Texas and Oklahoma. This fern can also be found in areas such as
subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Geographical z ...
America, parts of southern Africa and other humid or sub-humid climate areas.


Physiology and Rehydration

The resurrection fern gets its name because it can survive long periods of
drought A drought is defined as drier than normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D.  Jiang, A.  Khan, W.  Pokam Mba, D.  Rosenfeld, J. Tierney, an ...
by curling up its
frond A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the lar ...
s and appearing desiccated, grey-brown and dead. However, when just a little water is present, the fern will uncurl and reopen, appearing to "resurrect". It has been estimated that these plants could last 100 years without water and still revive after a single exposure. The resurrection fern roots have evolved to function as anchors for the epiphytes, holding them to their host tree’s bark and have been found to be inefficient in absorption. When in clustered groups of ferns on the bark of trees, the increased
transpiration Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth a ...
of the ferns and bark allow the middle ferns of the cluster to remain open longer than ferns on the outside. The relative humidity of the air and the closing rate of the leaves of the ferns is an inverse relationship. The greater the humidity, the slower the leaves of the ferns close because they have prolonged exposure to moisture in the air. The resurrection fern can severely
desiccate Desiccation () is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. ...
and lose almost all of its water. Experiments have shown they can lose up to 97%--and remain alive, though more typically they only lose around 76% in dry spells. For comparison, most other
plants Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...
would die after losing only 8-12%. This fern can lose almost all the water not hydrating the cells in its leaves and survive. Upon rainfall or even minute exposures to water they can fully rehydrate and return to a normal state within 24 to 48 hours. Following substantial exposures to moisture, there is an immediate increase in its water content of up to 50% after the first hour and 65-70% after three hours. When it regains moisture, the fern can once again become photosynthetically active, increasing its metabolism and release of organic compounds that provide nutrients for
symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...
bacteria that allow them both to thrive.   At least one study has shown association between ''P. polypodioides'' and
moss Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hor ...
, indicating that this fern may rely on moss for some of its water needs. The resurrection ferns accumulate sugar in their dehydrated cells in order to protect them and stabilize the membranes and proteins in the dry state. By accumulating sugar, the cells can maintain hydrogen bonds between necessary macromolecules needed for their structure. An interesting feature of the resurrection fern is it does not immediately uptake water after having been in a desiccated state. The resurrection ferns have porous cell structure networks that can expand and rearrange to accommodate absorbing three to four times their own weight in water after being exposed. Initially, the water flows via
capillary pressure In fluid statics, capillary pressure () is the pressure between two immiscible fluids in a thin tube (see capillary action), resulting from the interactions of forces between the fluids and solid walls of the tube. Capillary pressure can serve as bo ...
into the spongy layer of the epidermis and the porous network of the fern’s leaves, without altering them significantly. Over time, pressure builds up in the fern cell network, changing the turgor pressure and strain in the plant, initiating the unfolding of the leaves. The fern only stops unfolding its leaves when the cell network of the fern is entirely filled with water. The uncurling of the leaves was believed to be an entirely osmotic phenomenon, but when the fern is again exposed to water, it absorbs the water through solid
colloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend ...
s causing an increase in volume and capillary pressure of the cells of the fern.   When the fronds "dry", they curl with their bottom sides upwards. In this way, they can rehydrate the quickest when rain comes, as most of the water is absorbed on the underside of the leaf blades. The fern fronds contain canal cells in the center of their surface scales that direct water to the epidermis of the fern leaves, allowing absorption. The ability of the fern fronds to unroll after exposure to desiccation is attributed to the large cells of the upper epidermis along the midrib of the frond that increase in width more than any other epidermal cell, which forces the fronds to uncurl and flatten out. One way the resurrection fern has adapted to survive desiccation is the ability of its cell walls to deform and reform, without bursting or rupturing. It has been observed that
dehydrin Dehydrin (DHN) is a multi-family of proteins present in plants that is produced in response to cold and drought stress. DHNs are hydrophilic, reliably thermostable, and disordered. They are stress proteins with a high number of charged amino aci ...
s may allow the cell walls of the fern fronds and leaves to deform and reform in times of extreme drought followed by water exposure, due to large fluctuations in water content. Dehydrins were found to be only expressed when the fern was drying or in the desiccated state, with the dehydrins located on the outsides of the cells near the cell walls, allowing the leaves and fronds of the ferns to deform and reform accordingly.
Thermoluminescence Thermoluminescence is a form of luminescence that is exhibited by certain crystalline materials, such as some minerals, when previously absorbed energy from electromagnetic radiation or other ionizing radiation is re-emitted as light upon he ...
of the resurrection fern has been tested to observe at what temperatures it occurs and therefore shows what temperatures and amount of desiccation the ferns can tolerate before their
chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in ...
s lose the energy they’ve stored for the plant, in the form of light emissions. One study found the resurrection fern to require high temperatures before thermoluminescence occurred at around 50 degrees C whereas other desiccation-tolerant plants showed thermoluminescence at 40 degrees C. The thermoluminescence activity of the resurrection fern increased as it was exposed to six separate but consecutive flashes of green safelight at its leaves. Because thermoluminescence from the fern fronds wasn’t observed until higher temperatures, this hints that the fern’s chloroplasts may have a mechanism to withhold and store energy for the fern as it desiccates that allow it to survive higher temperatures and extreme periods of desiccation.


Reproduction

The fern has spores on the bottom of the fronds, contained in sori. The fern sporulates in Summer and early Fall. Rhizome sections are also viable offspring and can root themselves in new medium.


See also

*
Resurrection plant A resurrection plant is any poikilohydric plant that can survive extreme dehydration, even over months or years. Examples include: * ''Anastatica hierochuntica'', also known as the Rose of Jericho, a plant species native to deserts of North Africa ...


References


Flora of North America: ''Pleopeltis polypodioides'' var. ''michauxiana''USDA Plants Profile: ''Pleopeltis polypodioides''Flora of Zimbabwe: ''Polypodium polypodioides'' subsp. ''ecklonii''''Polypodium polypodioides''
from the Hardy Fern Library. *Moran, Robbin C., ''A Natural history of Ferns''. Timber Press (2004).

By John W. Story II * ttp://florida.plantatlas.usf.edu/Plant.aspx?id=3445Florida Plant Atlas Pleopeltis michauxiana

Florida Plant Atlas Pleopeltis polypodioides

NASA mission that took Resurrection Fern into space. {{Taxonbar, from=Q3392279 Pleopeltis, polypodioides Epiphytes Ferns of the Americas Ferns of Africa Ferns of the United States Flora of North America Flora of South America