Friday Fellow: King Fern

by Piter Kehoma Boll

Ferns make up an amazing group of plants and can have many different shapes and sizes. Some can grow like a tree, the so-called tree ferns, which are the tallest ferns in the world today. However, some other not-quite-tree ferns can also become really large. And one of those is today’s fellow, Angiopteris evecta, known as the king fern, giant fern, oriental vessel fern and many other names.

Native from Indonesia, Australia and many Pacific Islands near the equator, the king fern was discovered by European naturalists in the second half of the 18th century and it soon started to be cultivated as an ornamental plant due to its astonishing looks. The fronds (i.e., leaves) of the king fern are bipinnate, meaning that they have a feather shape, like in most ferns, where the leaflets are themselves formed by smaller leaflets. The shape of those fronds is nothing that special, but their size is amazing, as they can reach up to 9 m in length and 2.5 m in width. About 2 m of its length is formed by the thick and fleshy petiole. This makes them the largest fern leaves in the world, and they are even more incredible because despite this huge size they have no hard, woody tissues to sustain them, relying entirely on the hydraulic pressure of the sap.

The fronds of the king fern are so huge it is very hard to take a good photo of them. Credits of this one to Forest & Kim Starr.**

The rhizome (i.e., stem) of the king fern is also huge. It can reach up to 1 m in diameter and get very long. Most of it lies on the ground, like a fallen tree trunk, but the tip is often vertical and can reach up to 1.5 m in height. Overall, considering the size of the huge fronds, the plant can be up to 7 m high and 16 m wide.

The preferred habitat of the king fern are hot rainforests with very rich and drainable soils and good water availability, often near the coast. The sporangia that grow on the underside of the fronds produce a very large number of spores, which enables the king fern to spread quickly across suitable areas. As a result, it became invasive in some areas where it was introduced as an ornamental plant, such as Hawaii, Jamaica, Cuba and Costa Rica. Other regions where the king fern can potentially become invasive include most of the Caribbean and the tropical forest near the coast in Central and South America, Africa and Southeast Asia.

The thick trunk-like rhizome grows horizontally on the ground, except for its terminal part, which is pointed upward. Photo by Steve Fitzgerald.*

The king fern is traditionally used as a medicinal herb by the Dayak people in Borneo, especially to treat liver problems. The rhizome is highly toxic, but apparently can be eaten after a process to extract the toxins. Studies with extracts of the plant indicated that it has the potential for the development of drugs against HIV-1 and tuberculosis.

And there is one more interesting thing about this species. There are fossil fronds from the Carboniferous, about 300 million years old, that are basically identical to those of the king fern. This suggests that this species is insanely old, and was widespread around the whole world during that time. Later, as the eras passed, it retreated to its current native location in areas near the tropical Indo-Pacific. Now, due to human intervention, it seems that the king fern is about to dominate the whole planet again 300 million years after its last empire.

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References:

Christenhusz, M. J., & Toivonen, T. K. (2008). Giants invading the tropics: the oriental vessel fern, Angiopteris evecta (Marattiaceae). Biological Invasions, 10(8), 1215-1228. https://doi.org/10.1007/s10530-007-9197-7

Kamitakahara, H., Okayama, T., Agusta, A., Tobimatsu, Y., & Takano, T. (2019). Two‐dimensional NMR analysis of Angiopteris evecta rhizome and improved extraction method for angiopteroside. Phytochemical Analysis, 30(1), 95-100. https://doi.org/10.1002/pca.2794

Wikipedia. Angiopteris evecta. Available at < https://en.wikipedia.org/wiki/Angiopteris_evecta >. Access on 30 December 2021.

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* This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

** This work is licensed under a Creative Commons Attribution 3.0 Unported License.

Friday Fellow: Elkhorn Fern

by Piter Kehoma Boll

Unusually shaped plants are always charming for plant lovers and they can get very popular if they are easily cultivated. Among ferns, this is the case of Platycerium bifurcatum, the elkhorn fern or common staghorn fern.

Native from Java to Australia, the elkhorn fern and all other species of the genus Platycerium have a very out-of-the-ordinary appearance for a fern. Growing as an epiphyte, the elkhorn fern has two types of fronds (leaves): basal fronds and fertile fronds.

An old specimen of elkhorn fern in Queensland, Australia. Photo by D. Gordon E. Robertson.**

The basal fronds are ovoid, kidney- or shield-shaped and grow over the roots and rhizome, protecting them from desiccation by attaching to the substrate. They can reach a length of about 45 cm. They start green but with time dry out and become brown. The upper margin is often more losely attached to the substrate and allows water and leaf litter to reach the roots.

A baby specimen. Photo by Wikimedia user Calvinal*.

The fertile fronds are elongate and forked and grow away from the roots, reaching up to 90 cm in length. They often have a grayish-green color. In mature fronds, the long lobes from their bifurcation bear the sporangia, which are clustered in brownish sori.

Fertiles leaves with the brown mark of the sori on the underside. Photo by Wikimedia user Kembangraps.*

The elkhorn fern became a very popular garden plant. In tropical and subtropical regions, it can be cultivated outdoors, but in colder climates it only survies indoors since it cannot tolerate temperatures below 5°C. On the other hand, it is quite tolerant to high temperatures and even desiccation. Its basal fronds use Crassulacean Acid Metabolism, a special mechanism used by plants of arid localities to tolerate drought, although the fertile fronds do not seem to be able to do the same.

A specimen growing on a Casuarina glauca tree in Australia. Photo by Peter Woodard.

I was not able to find information about the ecological interactions of the elkhorn fern. Who eats it? How does its presence affect the performance of the host plant? Does it have a preferred substrate to grow in its native habitat? For such a popular plant, we seem to know very little about its relevance in the wild.

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References:

Wikipedia. Platycerium. Available at < https://en.wikipedia.org/wiki/Platycerium >. Access on 24 september 2020.

Wikipedia. Platycerium bifurcatum. Available at < https://en.wikipedia.org/wiki/Platycerium_bifurcatum >. Access on 24 september 2020.

Rut G, Krupa J, Miszalski Z, Rzepka A, Ślesak I (2008) Crassulacean acid metabolism in the epiphytic fern Patycerium bifurcatum. Photosynthetica 46:156. https://doi.org/10.1007/s11099-008-0026-8

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* This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

** This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

Friday Fellow: Leatherleaf Fern

by Piter Kehoma Boll

Leia em Português

You may have seen parts of today’s fellow at least once in your life, as it is a very popular plant in flower arrangements.

A flower bouquet including leaves of Rumohra adiantiformis.

Rumohra adiantiformis is how it is known by botanists, and common names include leatherleaf fern, seven-weeks fern and iron fern. This fern species is widely distributed in Australasia, southern Africa and the Neotropics, as well as several islands of the Pacific Ocean.

Living in forested areas, especially where there is not too much shade, the leatherleaf fern has a biology that is not very different from that of other ferns. It usually grows on the soil, although it may eventually occur on rocks or on trees. What makes this fern special is that its mature fronds are somewhat hard and, after being cut off, continue to have a green and live appearance for a very long time, usually several weeks. This amazing resistance to wilt makes it an ideal species to be used in flower arrangements.

Leatherleaf fern growing in South Africa. Photo by Wikimedia user JMK.*

Currently, most of the leatherleaf fern’s production for commercial use occurs in the state of Florida, USA, where it is cultivated in irrigated shaded nurseries. Other large producers are South Africa and Brazil, especially southern Brazil, but in these two countries the plant is exploited through extractivism, i.e., it is harvested in the wild and not cultivated. Although the extraction of the leatherleaf fern is a widespread activity in both South Africa and southern Brazil and is a major source of income for many families, it is illegal under national or regional laws. However, at least in southern Brazil, where the leatherleaf fern occurs in the highest recorded densities in the world, the main reason for its populations to be diminishing does not seem to be its extraction but rather natural forest succession. As forests grow older and become darker, they become unsuitable for the leatherleaf fern to grow.

It is, of course, necessary to establish limits for its harvest. Otherwise, its increasing demand in the florist market may end up causing concerning effects on its occurrence. The best alternative continues to be cultivating the fern, as it protects wild populations and allows the harvest of high-quality fronds and a faster recovery after defoliation.

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References:

Geldenhuys CJ, van der Merwe CJ (1988) Population structure and growth of the fern Rumohra adiantiformis in relation to frond harvesting in the southern Cape forests. South African Journal of Botany 54(4): 351–362.

Milton SJ (1987) Growth of Seven-weeks Fern (Rumohra adiantiformis) in the Southern Cape Forests: Implications for Management. South African Forestry Journal 143: 1–4.

Souza GC, Cubo R, Guimarães L, Elisabetsky E (2006) An ethnobiological assessment of Rumohra adiantiformis (samambaia-preta) extractivism in Southern Brazil. Biodiversity and Conservation 15: 2737–2746. doi: 10.1007/s10531-005-0309-3

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* This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

Friday Fellow: Giant Salvinia

by Piter Kehoma Boll

We are moving out of the sea this week, but will still remain in the water to bring you a peculiar fern. Commonly known as giant salvinia, kariba weed or giant watermoss, its scientific name is Salvinia molesta and it comes from southeastern Brazil.

Fronds of Salvinia molesta growing in Hawaii. Photo by Forrest & Kim Starr.*

The water salvinia is an aquatic fern that floats on the surface of the water and has a peculiar anatomy. It lacks roots, and it produces leaves in sets of three. Two of them remain at the surface of the water, side by side, and the third one is submerged, acting like a modified root. The upper side of the surface leaves (which are anatomically their underside) have many small hairs that turn them into a waterproof surface and the underside have very long hairs that look like roots.

Preferring slow-moving waters, the giant salvinia grows very quickly in ideal conditions and has become an invasive species in several parts of the world. It was exported from Brazil to be used in aquaria and garden ponds and ended up in natural environments. While spreading, the giant salvinia can cover the entire surface of water bodies, blocking light for other plants and algae, which decreases photosynthesis and reduces the amount of oxygen in the water. Additionally, it can clog waterways, blocking natural or artificial water flows.

The problem caused by the giant salvinia in areas where it has become invasive led to the development of control methods. One of the simplest methods is simply removing the plants mechanically, but it is difficult in areas with large infestations, as even small remaining populations may quickly recover. Another alternative is the use of biological control using Cyrtobagous salviniae, a tiny weevil that feeds on the giant salvinia in its natural environment.

Not everything about the giant salvinia is bad, actually. Its peculiar leaf anatomy led to the discovery of what was properly called “the salvinia effect”, a phenomen by which an air layer becomes stable over a submerged surface, as in the leaves of species of Salvinia. By developing artificial structures that make use of this phenomenon, it is possible to produce devices that move smoothly in water, such as ships with reduced friction.

A considerably recent study also found out that some compounds extracted from the giant salvinia are effective in the control of human tumor cells.

Our relationship with this peculiar plant is therefore one of love and hate.

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References:

Coetzee, J. A.; Hill, M. P.; Byrne, M. J.; Bownes, A. (2011) A Review of the Biological Control Programmes on Eichhornia crassipes (C.Mart.) Solms (Pontederiaceae), Salvinia molesta D.S.Mitch. (Salviniaceae), Pistia stratiotes L. (Araceae), Myriophyllum aquaticum (Vell.) Verdc. (Haloragaceae) and Azolla filiculoides Lam. (Azollaceae) in South Africa. African Entomology 19: 451-468.

Li, S.; Wang, P.; Deng, G.;  Yuan, W.; Su, Z. (2013)  Cytotoxic compounds from invasive giant salvinia (Salvinia molesta) against human tumor cells. Bioorganic & Medicinal Chemistry Letters 23(24): 6682-6687.

Wikipedia. Salvinia molesta. Available at < https://en.wikipedia.org/wiki/Salvinia_molesta >. Access on February 21, 2018.

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This work is licensed under a Creative Commons Attribution 3.0 Unported License.

Friday Fellow: Mexican Giant Horsetail

by Piter Kehoma Boll

If you are walking through the forest of Central America, you may end up finding something that at first you could think is a group of bamboos, plants growing as a cylindrical segmented stem that can reach up to 7 m in height, as seen in the picture below:

A group of bamboos? Not exactly. Photo by Alex LomasAlex Lomas.*

Those are not actually bamboos, though, but specimens of the largest species of horsetail that exists today, the Mexican giant horsetail, Equisetum myriochaetum. It can be found growing naturally from Peru to Mexico in areas of fertile soil, especially along water bodies such as streams and swamps.

As other horsetails, the Mexican giant horsetail has an erect and hollow stem with very narrow leaves growing in a whirl around the “joints” of the stem. The leaves are very simple, similar to those of more primitive plants such as the spikemosses and ground pines, but are thought to be a simplification of more complex leaves, as they are more closely related to the complex-leaved ferns.

More than only the largest horsetail in the world, the Mexican giant horsetail is an important medicinal plant in Mexican folk medicine, being used to treat kidney diseases and type 2 diabetes mellitus. And as in many other occasions, laboratory studies confirmed that water extracts from the aerial parts of E. myriochaetum do indeed reduce the blood glucose levels of type 2 diabetic patients without reducing their insulin levels. One more point to traditional medicine.

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References:

EOL – Encyclopedia of Life. Equisetum myriochaetum. Available at <http://eol.org/pages/6069616/overview&gt;. Access on March 4, 2017.

Revilla, M., Andrade-Cetto, A., Islas, S., & Wiedenfeld, H. (2002). Hypoglycemic effect of Equisetum myriochaetum aerial parts on type 2 diabetic patients Journal of Ethnopharmacology, 81 (1), 117-120 DOI: 10.1016/S0378-8741(02)00053-3

Royal Botanic Garden Edinburgh. Equisetum myriochaetum. Available at <http://www.rbge.org.uk/the-gardens/plant-of-the-month/plant-profiles/equisetum-myriochaetum&gt;. Access on March 4, 2017.

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Friday Fellow: Samambaiaçu

by Piter Kehoma Boll

It’s more than time to bring a fern as a Friday Fellow, and I decided to start with one of my favorites, the Neotropical tree fern Dicksonia sellowiana, known in Brazil as Samambaiaçu or Xaxim.

A samambaiaçu in a forest in southern Brazil. Photo by Wikimedia user DeadWood II.*

The samambaiaçu occurs from southern Mexico to Uruguay and is usually found in moist forests, being a remarkable species of moist forests in southern Brazil, especially in Araucaria moist forests. It may reach several meters in height and the fronds (leaves) reach up to 2,4 m in length.

During most of the 20th century, the fibrous stems of the samambaiaçu (usually called “xaxim”) were extensively used for manufacturing flower pots or plates that served as a substrate for cultivating orchids and other epiphytic plants. As a result of this exploitation, as well as the destruction of its native habitat, the samambaiaçu is currently included in the Brazilian Red List of endangered species.

The trade of xaxim is currently forbidden by law in Brazil, so if  you ever find someone selling it somewhere, please, communicate the authorities!

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References:

Schmitt, J., Schneider, P., & Windisch, P. (2009). Crescimento do cáudice e fenologia de Dicksonia sellowiana Hook. (Dicksoniaceae) no sul do Brasil Acta Botanica Brasilica, 23 (1), 283-291 DOI: 10.1590/S0102-33062009000100030

Brazil. Law Nº 9.605/98. Available at: <http://www.planalto.gov.br/ccivil_03/leis/L9605.htm >.

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