Epiphytes in the tropical rainforest

Plant Adaptations

1. Bark
In drier, temperate deciduous forests a thick bark helps to limit moisture evaporation from the tree’s trunk. Since this is not a concern in the high humidity of tropical rainforests, most trees have a thin, smooth bark. The smoothness of the bark may also make it difficult for other plants to grow on their surface.
2. Lianas
Lianas are climbing woody vines that drape rainforest trees. They have adapted to life in the rainforest by having their roots in the ground and climbing high into the tree canopy to reach available sunlight. Many lianas start life in the rainforest canopy and send roots down to the ground.

3. Drip Tips
The leaves of forest trees have adapted to cope with exceptionally high rainfall. Many tropical rainforest leaves have a drip tip. It is thought that these drip tips enable rain drops to run off quickly. Plants need to shed water to avoid growth of fungus and bacteria in the warm, wet tropical rainforest.

4. Buttresses
Many large trees have massive ridges near the base that can rise 30 feet high before blending into the trunk. Why do they form? Buttress roots provide extra stability, especially since roots of tropical rainforest trees are not typically as deep as those of trees in temperate zones.

5. Prop and Stilt Roots
Prop and stilt roots help give support and are characteristic of tropical palms growing in shallow, wet soils. Although the tree grows fairly slowly, these above-ground roots can grow 28 inches a month.
6. Epiphytes
Epiphytes are plants that live on the surface of other plants, especially the trunk and branches. They grow on trees to take advantage of the sunlight in the canopy. Most are orchids, bromeliads, ferns, and Philodendron relatives. Tiny plants called epiphylls, mostly mosses, liverworts and lichens, live on the surface of leaves.

7. Bromeliads
Bromeliads are found almost exclusively in the Americas. Some grow in the ground, like pineapple, but most species grow on the branches of trees. Their leaves form a vase or tank that holds water. Small roots anchor plants to supporting branches, and their broad leaf bases form a water-holding tank or cup. The tank’s capacity ranges from half a pint to 12 gallons or more. The tanks support a thriving eco-system of bacteria, protozoa, tiny crustaceans, mosquito and dragonfly larvae, tadpoles, birds, salamanders and frogs.

Mangroves
On tropical deltas and along ocean edges and river estuaries, trees have adapted to living in wet, marshy conditions. These trees, called mangroves, have wide-spreading stilt roots that support the trees in the tidal mud and trap nutritious organic matter.

Nepenthes

Pitcher plant vines in the family Nepenthaceae have leaves that form a pitcher, complete with a lid. Sweet or foul-smelling nectar in the pitcher attracts insects, especially ants and flies, that lose their grip on the slick sides and fall into the liquid. Downward-pointing hairs inside the pitcher prevent the insects’ escape. The insects are digested by the plants and provide nutrients. Pitcher plants are not epiphytes but climbers rooted in the soil.

The forest really does hum with life.

Though often too low or too high for human ears to detect, insects and animals signal each other with vibrations. Even trees and plants fizz with the sound of tiny air bubbles bursting in their plumbing.

And there is evidence that insects and plants “hear” each other’s sounds. Bees buzz at just the right frequency to release pollen from tomatoes and other flowering plants. And bark beetles may pick up the air bubble pops inside a plant, a hint that trees are experiencing drought stress.

Sound is so fundamental to life that some scientists now think there’s a kernel of truth to folklore that holds humans can commune with plants. And plants may use sound to communicate with one another.

If even bacteria can signal one another with vibrations, why not plants, said Monica Gagliano, a plant physiologist at the University of Western Australia in Crawley.

“Sound is overwhelming, it’s everywhere. Surely life would have used it to its advantage in all forms,” she told OurAmazingPlanet.

Gagliano and her colleagues recently showed corn seedling’s roots lean toward a 220-Hertz purr, and the roots emit clicks of a similar tune. Chili seedlings quicken their growth when a nasty sweet fennel plant is nearby, sealed off from the chilies in a box that only transmits sound, not scent, another study from the group revealed. The fennel releases chemicals that slow other plants’ growth, so the researchers think the chili plants grow faster in anticipation of the chemicals — but only because they hear the plant, not because they smell it. Both the fennel and chilies were also in a sound-isolated box.

“We have identified that plants respond to sound and they make their own sounds,” Gagliano said. “The obvious purpose of sound might be for communicating with others.”

Monica Gagliano, plant acoustics researcher. (Image credit: University of Western Australia)

Gagliano imagines that root-to-root alerts could transform a forest into an organic switchboard. “Considering that entire forests are all interconnected by networks of fungi, maybe plants are using fungi the way we use the Internet and sending acoustic signals through this Web. From here, who knows,” she said.

As with other life, if plants do send messages with sound, it is one of many communication tools. More work is needed to bear out Gagliano’s claims, but there are many ways that listening to plants already bears fruit.

When the bubble bursts

Scientists first recognized in the 1960s that listening to leaves revealed the health of plants.

When leaves open their pores to capture carbon dioxide, they lose huge amounts of water. To replace this moisture, roots suck water from the ground, sending it skyward through a series of tubes called the xylem. Pit membranes, essentially two-way valves, connect each of the thousands of tiny tubes. The drier the soil, the more tension builds up in the xylem, until pop, an air bubble is pulled in through the membrane.

For some plants, these embolisms are deadly — as with human blood vessels — because the gas bubbles block the flow of water. The more air in the tubes, the harder it is for plants to pull in water, explains Katherine McCulloh, a plant ecophysiologist at Oregon State University.

But researchers who eavesdrop on plant hydraulics are discovering that certain species, like pine trees and Douglas firs, can repair the damage on a daily or even an hourly basis.

“These cycles of embolism formation and refilling are just something that happens every single day. The plant is happy, it’s just day-to-day living,” McCulloh said. “In my mind, this is revolutionary in terms of plant biology. When I learned about how plants moved water, it was a passive process driven by evaporation from the leaves. What we’re beginning to realize is that’s just not true at all. It’s a completely dynamic process.”

How to listen to plants

The technology to hear plant bubbles explode is actually quite simple. Acoustic sensors designed to detect cracks in bridges and buildings catch the ultrasonic pops. A piezoelectric pickup, the same as an electric guitar pickup, goes through an amplifier to an oscilloscope that measures the waveform of each pop. The acoustic sensor is pricey, but Duke University botanist Dan Johnson has funding from the National Science Foundation and the U.S. Department of Agriculture to build a low-cost version this summer. He’ll give the embolism detector to high school students at the North Carolina School of Science and Mathematics in Durham.

“I think plant hydraulics will be the piece of the puzzle that tells us which species are going to live and which species are going to die with climate change,” Johnson told OurAmazingPlanet. “Plant hydraulics will tell us what our future forests will look like in 50 years.”

Two geologists in Arizona are also building a low-cost acoustic detector, crowd-funded at about $1,000, drawn by the age-old allure of communicating with plants.

“We became fascinated with the thought of being able to listen in to the plumbing of the saguaro cactus,” said Lois Wardell, owner of Tucson-based consulting firm Arapahoe SciTech. Starting with a 3-foot-tall potted saguaro, Wardell and geophysicist Charlotte Rowe hope to distinguish between cacti drying out and those complaining about other environmental stress.

“We’re working on trying to differentiate these two signals: I’m cold versus I’m really thirsty,” Wardell said. “We’ve already managed to produce a few squawks.”

What plants say about drought

Acoustic emissions, or the sound of bursting air bubbles, could also upend assumptions about the effects of drought on plants.

In the arid Southwest, Johnson was surprised to find that the plants considered the most drought-tolerant, such as junipers, did worst at repairing embolisms. Broad-leaf plants, including rhododendrons and beaked hazels, were better at fixing the damage caused by dry pipes.

“With the incredible drought going on there right now, the species we predicted to die are exactly the opposite of what’s occurring,” Johnson said. “We’re seeing a lot of deaths in junipers, and those are typically the most drought-resistant in that area, whereas most of the broad-leaf systems go dormant and they repair whatever embolisms occur the next spring, when there’s more water.”

A Ponderosa Pine needle scanning electron microscope image. What we see is that the xylem (in red) embolizes as the leaves get more dehydrated. a) fully hydrated at minus 112 degrees Fahrenheit (minus 80 degrees Celsius (cryoSEM); b) fully hydrated, but imaged at room temperature with epifluorescence microscopy; c) cryoSEM of a dehydrated needle; and d) cryoSEM of a severely dehydrated needle. Panels b,c, and d are zoomed in compared to panel a. (Image credit: Dan Johnson, Duke University)

Johnson predicts that in future severe droughts, the plants that have a harder time repairing embolisms are more likely to die. “It’s the plants that can repair embolisms that are going to survive,” he said.

Living in drought-stricken Australia, Gagliano is also excited by the possibility of decoding drought signals. “We don’t know if these emissions are also providing information to neighborhoods of plants,” she said. “Plants have ways of protecting themselves when they run out of water, and they are really good at sharing information about danger, even if one sharing is one that’s going to die.”

Sensing sound by touch instead?

Critics of Gagliano’s research point out that no one has found structures resembling a mouth or ears on corn or any other plant. Nor do the group’s studies prove that plants “talk” among themselves.

“This is pretty provocative and worth following, but it doesn’t really provide a lot of evidence that these are acoustic communications,” said Richard Karban, a University of California, Davis, expert in how plants communicate via chemical signals.

But simpler life forms manage just fine without complex sound receptors and producers. Walnut sphinx caterpillars whistle by forcing air out of holes in their sides. Flying insects perform death drops when they sense a bat’s sonar clicks. Earthworms flee the vibrations of oncoming moles.

Of course, there may be another explanation for the apparent response to sound reported by Gagliano. One that could also account for the century of researchers and home gardeners (including Charles Darwin) who manipulated plant growth with music.

Could a sense of touch be why plants seem to respond to sound?

Even humans can perceive sound without hearing it, said Frank Telewski, a botanist at Michigan State University and an expert on how trees respond to wind.

“How many times have you sat next to someone who has their car stereo at full blast? You can really feel it pounding in your chest,” he said.

Trees perceive and respond to touch, like wind or an animal passing on a trail. And like the wind, sound is a wave that travels through air.

In fact, a tree needs wind to grow, Telewski said. “If you stake down a seedling, you do it a little bit of disservice, because a tree needs to perceive motion. It’s like physical therapy for the tree. If you stake it too tight, it does not allow the plant to produce stronger tissues.”

Wheat harvest on the Palouse. (Image credit: USDA/ARS)

But Telewski is open to the idea of plant communication by sound. He said in the last few years, researchers in China have shown they can increase plant yields by broadcasting sound waves of certain frequencies. Other groups have investigated how different frequencies and intensities of sounds change gene expression. Their studies find that acoustic vibrations modify metabolic processes in plants. Some of the beneficial vibrations also drive away pesky insects that munch on crops.

“We’re not there yet,” Telewski said of the effort to prove plants communicate. “Sometimes a fantastic hypothesis can turn out to be true, but there has to be fantastic evidence to support it.”

Answering critics

Karban, from UC Davis, notes that the plant field is not very receptive to new ideas. The idea that plants could talk via scent, or volatile chemicals, was roundly pooh-poohed in the 1980s, but Karban and others went on to prove that plants including sagebrush warn their neighbors of impending danger by wafting chemical signals into the air. “At times in my career I’ve tried to push new ideas and it’s been very difficult,” Karban said.

Gagliano remains undeterred by the skepticism.

“I was guided to sound by the long tradition in folklore of people talking to plants and listening to plants and plants making sounds,” Gagliano said. “I wanted to see if there was any scientific basis for something that stays so stubbornly in our culture.”

But the corn root clicks are at the lower end of the human hearing range. “In theory, we could hear it, but realistically, these were emitted from roots in the ground, so the truth is we probably wouldn’t hear it,” she said. And the fizzy bubble bursts in xylem are ultrasonic, about 300 kiloHertz, detectable only by insects and some other animals.

This spring, Gagliano and her collaborators will screen more plants for communication skills. “We will see whether some groups of plants might be more chatty than others, and if some plants have specific requirements for sound,” she said. They also plan to record sounds emitted from plants and play them back and see what kind of response, if any, they produce in other plants.

“Shamans say they learn from the plant’s sounds. Maybe they are attuned to things we don’t pay attention to,” Gagliano said. “It’s really fascinating. We might have lost that connection and science is ready to rediscover it.”

Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanet, Facebook or Google+. Original article on LiveScience’s OurAmazingPlanet.

Types Of Epiphytes – What Is An Epiphyte Plant And Adaptations Of Epiphytes

Both tropical and rainforests feature an incredible array of plants. Those that dangle from trees, rocks and vertical supports are called epiphytes. Tree epiphytes are called air plants because they have no firm grip in the earth. This fascinating collection of plants is also fun to grow indoors or out in the garden. Find answers on what is an epiphyte plant so you can introduce this unique form to your indoor or outdoor landscape.

What is an Epiphyte Plant?

The word epiphyte comes from the Greek “epi”, which means “upon” and “phyton”, which means plant. One of the amazing adaptations of epiphytes is their ability to attach to vertical surfaces and capture their water and much of their nutrient needs from sources other than soil.

They may be found on branches, trunks and other structures. While epiphytes may live on other plants, they are not parasites. There are many types of epiphytes, with the majority being found in tropical and cloud forests. They get their moisture from the air but some even live in desert terrain and gather moisture from fog.

Types of Epiphytes

You might be surprised what plants have the adaptations of epiphytes. Tree epiphytes are usually tropical plants such as bromeliads, but they may also be cacti, orchids, aroids, lichens, moss and ferns.

In tropical rain forests, giant philodendrons wrap themselves around trees but are still not tethered to the ground. The adaptations of epiphytes allow them to grow and flourish in areas where ground is difficult to reach or already populated by other plants.

Epiphytic plants contribute to a rich ecosystem and provide canopy food and shelter. Not all plants in this group are tree epiphytes. Plants, such as mosses, are epiphytic and may be seen growing on rocks, the sides of houses and other inorganic surfaces.

Adaptations of Epiphytes

The flora in a rainforest is diverse and thickly populated. The competition for light, air, water, nutrients and space is fierce. Therefore, some plants have evolved to become epiphytes. This habit allows them to take advantage of high spaces and upper story light as well as misty, moisture-laden air. Leaf litter and other organic debris catches in tree crotches and other areas, making nutrient-rich nests for air plants.

Epiphyte Plant Care and Growth

Some plant centers sell epiphytic plants for home gardeners. They need to have a mount in some cases, such as Tillandsia. Affix the plant to a wooden board or cork piece. The plants gather much of their moisture from the air, so place them in moderate light in the bathroom where they can get water from shower steam.

Another commonly grown epiphyte is the bromeliad. These plants are grown in well-drained soil. Water them in the cup at the base of the plant, which is designed to capture moisture out of misty air.

For any epiphytic plant, try to mimic the conditions of its natural habitat. Orchids grow in shredded bark and need average light and moderate moisture. Take care not to overwater epiphytic plants since they supplement their moisture needs from the air. Humid conditions often provide all the moisture a plant will need. You can assist the plant by misting the air around it or putting the pot in a saucer of rocks filled with water.

Planting billions of trees across the world is one of the biggest and cheapest ways of taking CO2 out of the atmosphere to tackle the climate crisis, according to scientists, who have made the first calculation of how many more trees could be planted without encroaching on crop land or urban areas.

As trees grow, they absorb and store the carbon dioxide emissions that are driving global heating. New research estimates that a worldwide planting programme could remove two-thirds of all the emissions from human activities that remain in the atmosphere today, a figure the scientists describe as “mind-blowing”.

The analysis found there are 1.7bn hectares of treeless land on which 1.2tn native tree saplings would naturally grow. That area is about 11% of all land and equivalent to the size of the US and China combined. Tropical areas could have 100% tree cover, while others would be more sparsely covered, meaning that on average about half the area would be under tree canopy.

The scientists specifically excluded all fields used to grow crops and urban areas from their analysis. But they did include grazing land, on which the researchers say a few trees can also benefit sheep and cattle.

“This new quantitative evaluation shows restoration isn’t just one of our climate change solutions, it is overwhelmingly the top one,” said Prof Tom Crowther at the Swiss university ETH Zürich, who led the research. “What blows my mind is the scale. I thought restoration would be in the top 10, but it is overwhelmingly more powerful than all of the other climate change solutions proposed.”

Crowther emphasised that it remains vital to reverse the current trends of rising greenhouse gas emissions from fossil fuel burning and forest destruction, and bring them down to zero. He said this is needed to stop the climate crisis becoming even worse and because the forest restoration envisaged would take 50-100 years to have its full effect of removing 200bn tonnes of carbon.

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But tree planting is “a climate change solution that doesn’t require President Trump to immediately start believing in climate change, or scientists to come up with technological solutions to draw carbon dioxide out of the atmosphere”, Crowther said. “It is available now, it is the cheapest one possible and every one of us can get involved.” Individuals could make a tangible impact by growing trees themselves, donating to forest restoration organisations and avoiding irresponsible companies, he added.

Other scientists agree that carbon will need to be removed from the atmosphere to avoid catastrophic climate impacts and have warned that technological solutions will not work on the vast scale needed.

Jean-François Bastin, also at ETH Zürich, said action was urgently required: “Governments must now factor into their national strategies.”

Q&A

Why are trees good for the environment?

Show Hide

There are about three trillion trees on the planet and they play a major role in producing the oxygen we all breathe. But twice as many existed before the start of human civilisation.

Today, 10 billion more trees are cut down than are planted every year. This destruction is a significant contributor to the carbon emissions that are driving the climate crisis. However, trees draw carbon dioxide back out of the atmosphere as they grow, and planting trees will need to play an important part in ending the climate emergency.

Forests are also a vital and rich habitat for wildlife. Earth is at the start of a sixth mass extinction of species and the razing of forests and other ecosystems is the biggest contributor to the losses. Tropical rainforests are especially important, hosting 50% of known terrestrial species on only 6% of the world’s land. Trees are also important in controlling regional rainfall, as they evaporate water from their leaves.

In urban areas, the shade from trees has been shown to both cool city streets and reduce levels of air pollution. They can also boost people’s wellbeing as part of green spaces, with research showing two-hour “dose” of nature a week significantly improving health.

Christiana Figueres, former UN climate chief and founder of the Global Optimism group, said: “Finally we have an authoritative assessment of how much land we can and should cover with trees without impinging on food production or living areas. This is hugely important blueprint for governments and private sector.”

René Castro, assistant-director general at the UN Food and Agriculture Organisation, said: “We now have definitive evidence of the potential land area for re-growing forests, where they could exist and how much carbon they could store.”

The study, published in the journal Science, determines the potential for tree planting but does not address how a global tree planting programme would be paid for and delivered.

Crowther said: “The most effective projects are doing restoration for 30 US cents a tree. That means we could restore the 1tn trees for $300bn , though obviously that means immense efficiency and effectiveness. But it is by far the cheapest solution that has ever been proposed.” He said financial incentives to land owners for tree planting are the only way he sees it happening, but he thinks $300bn would be within reach of a coalition of billionaire philanthropists and the public.

Effective tree-planting could take place across the world, Crowther said: “The potential is literally everywhere – the entire globe. In terms of carbon capture, you get by far your biggest bang for your buck in the tropics but every one of us can get involved.” The world’s six biggest nations, Russia, Canada, China, the US, Brazil and Australia, contain half the potential restoration sites.

Tree planting initiatives already exist, including the Bonn Challenge, backed by 48 nations, aimed at restoring 350m hectares of forest by 2030. But the study shows that many of these countries have committed to restore less than half the area that could support new forests. “This is a new opportunity for those countries to get it right,” said Crowther. “Personally, Brazil would be my dream hotspot to get it right – that would be spectacular.”

The research is based on the measurement of the tree cover by hundreds of people in 80,000 high-resolution satellite images from Google Earth. Artificial intelligence computing then combined this data with 10 key soil, topography and climate factors to create a global map of where trees could grow.

This showed that about two-thirds of all land – 8.7bn ha – could support forest, and that 5.5bn ha already has trees. Of the 3.2bn ha of treeless land, 1.5bn ha is used for growing food, leaving 1.7bn of potential forest land in areas that were previously degraded or sparsely vegetated.

“This research is excellent,” said Joseph Poore, an environmental researcher at the Queen’s College, University of Oxford. “It presents an ambitious but essential vision for climate and biodiversity.” But he said many of the reforestation areas identified are currently grazed by livestock including, for example, large parts of Ireland.

“Without freeing up the billions of hectares we use to produce meat and milk, this ambition is not realisable,” he said. Crowther said his work predicted just two to three trees per field for most pasture: “Restoring trees at density is not mutually exclusive with grazing. In fact many studies suggest sheep and cattle do better if there are a few trees in the field.”

Crowther also said the potential to grow trees alongside crops such as coffee, cocoa and berries – called agro-forestry – had not been included in the calculation of tree restoration potential, and neither had hedgerows: “Our estimate of 0.9bn hectares is reasonably conservative.”

However, some scientists said the estimated amount of carbon that mass tree planting could suck from the air was too high. Prof Simon Lewis, at University College London, said the carbon already in the land before tree planting was not accounted for and that it takes hundreds of years to achieve maximum storage. He pointed to a scenario from the Intergovernmental Panel on Climate Change 1.5C report of 57bn tonnes of carbon sequestered by new forests this century.

Other scientists said avoiding monoculture plantation forests and respecting local and indigenous people were crucial to ensuring reforestation succeeds in cutting carbon and boosting wildlife.

Earlier research by Crowther’s team calculated that there are currently about 3tn trees in the world, which is about half the number that existed before the rise of human civilisation. “We still have a net loss of about 10bn trees a year,” Crowther said.

Visit the Crowther Lab website for a tool that enables users to look at particular places and identify the areas for restoration and which tree species are native there.

• This article was amended on 18 October 2019 to reflect a revision made to the original research paper, and a clarification in a letter by the authors of the study in the journal Science, that responds to criticism of their work. They clarify that one comparison made did not take into account that 55% of the CO2 produced by human activity is absorbed by land and oceans. The text of the first and second paragraph of this article have been edited to reflect this and the paper revision.

Epiphyte

Epiphyte, also called air plant, any plant that grows upon another plant or object merely for physical support. Epiphytes have no attachment to the ground or other obvious nutrient source and are not parasitic on the supporting plants. Most epiphytes are found in moist tropical areas, where their ability to grow above ground level provides access to sunlight in dense shaded forests and exploits the nutrients available from leaf and other organic debris that collects high in the tree canopy. The majority of epiphytic plants are angiosperms (flowering plants); they include many species of orchids, tillandsias, and other members of the pineapple family (Bromeliaceae). Mosses, ferns, and liverworts are also common epiphytes and are found in both tropical and temperate regions. While epiphytes are uncommon in arid environments, ball moss (Tillandsia recurvata) is a notable exception and can be found in coastal deserts in Mexico, where it receives moisture from marine fog.

  • Epiphyte bromeliads (Vriesea).Luiz Claudio Marigo/Bruce Coleman Ltd.
  • Ant-welcoming epiphyte (genus Myrmecodia). Within the core of the plant is a network of chambers housing ants that provide nutrients for the plant.Frithfoto/Bruce Coleman Ltd.

Epiphytes obtain water from rain and water vapour in the air; most absorb water with their roots, though many have specialized leaves that also take in moisture. While some minerals are obtained directly from rain, nutrients are generally absorbed from the debris that collects on the supporting plants. Given their narrow habitat requirements, many epiphytes rely on wind for seed dispersal and have feathery or dustlike seeds. Animal dispersal is also common, and a number of species have edible fruits with seeds that are dispersed by birds and other tree-dwelling animals.

Epiphytic orchids (genus Dendrobium). Epiphytes establish aerial roots that absorb moisture from the humid air, allowing them to develop on other plants without harming their hosts.E.R. Degginger

epiphytic plant

Synonyms: aerophyte, air plant, epiphyte Types: show 7 types… hide 7 types… Clusia insignis, waxflower epiphytic clusia of British Guiana Spanish moss, Tillandsia usneoides, black moss, long moss, old man’s beard dense festoons of greenish-grey hairlike flexuous strands anchored to tree trunks and branches by sparse wiry roots; southeastern United States and West Indies to South America aeschynanthus a plant of the genus Aeschynanthus having somewhat red or orange flowers and seeds having distinctive hairs at base and apex hemiepiphyte, semiepiphyte a plant that is an epiphyte for part of its life strangler, strangler tree an epiphytic vine or tree whose aerial roots extend down the trunk of a supporting tree and coalesce around it eventually strangling the tree Clusia major, Clusia rosea, pitch apple, strangler fig a common tropical American clusia having solitary white or rose flowers Aeschynanthus radicans, lipstick plant epiphyte or creeping on rocks; Malaysian plant having somewhat fleshy leaves and bright red flowers Type of: flora, plant, plant life (botany) a living organism lacking the power of locomotion

Epiphytes adaptations

We often hear that epiphytes plants live on the air and it really seems like this, because they don’t nearly need soil to develop. They grow on trunks taking advantage of his height in search of the source of energy much wanted in tropical forests: the sun. In this article we describe epiphytes adaptations and the most common epiphytic groups of these amazing plants.

The epiphytes live on other plants without parasitize them or damaging any of its organs or functions. Epiphytes take advantage of other plants structures as physical support to grow into the shaded forest canopy, using the trunks and branches of older trees to reach more height and catch the sunlight. Epiphytes never touch the ground; they are adapted to live on the air!

Epiphytic plants including Cactaceae, Bromeliaceae and ferns growink on a trunk. Source: Barres Fotonatura.

They have amazing adaptations as a result of this habit, such as:

• The ability to capture water and nutrients from the air, the rain and the small amount of soil or organic debris that may remain in the trees trunk where they root.

• Their roots are much more adapted to anchor to the trunks that to absorve water and nutrients.

• Frequently, they develop structures to accumulate moisture.

Although epiphyte plants depend on its host to obtain their nutrients, sometimes they grow so much that overload their host and end up killing their support. This is the case of some Ficus (Moraceae), called “strangler fig” that develop aerial roots around other trees without letting them grow.

Hollow structure left by a stranges fig after killing its hoste. Source: Wikipedia.

Thanks to the epiphytes contribution we can say that tropical rain forest is organized in a vertical gradient along the trees trunks, where we find organism diversity organized according to their distance to the ground. Epiphytes are largely responsible for the extremely rich biodiversity that makes tropical rainforests the most complex ecosystems on Earth. Besides providing different layers of vegetation along height, epiphytes provide shelter and nutrients to different insects and amphibians; who use water stored in the epiphytes leaves as a shelter or nest in the refuge generated in the middle of the trunk.

Water accumulated on a Bromeliad. Source: Otávio Nogueira, Creative Commons.

Epiphytes are found mostly in tropical rainforests, where dozens epiphytes have recorded on a single tree. However, in temperate climates or even deserts we can also found drought tolerant epiphytic species.

Epiphytes diversity

Currently, approximately 25,000 species are epiphytes. Most common and known epiphytes are Bromeliaceae and Orchidaceae families and ferns. Epiphytism has appeared several times throughout evolution and we found examples in other tropical spermatophytes (plants with seed and trunk) like Ericaceae, Gesneriaceae, Melastomataceae, Moraceae and Piperaceae and also in seedless plants (lichens, mosses and liver) of temperate climates.

Orchids

Orchids have the highest number of epiphytic in the world, with 20 tropical epiphytic genera. The genus with much epiphytes species number are Bulbophyllum (1800) and Dendrobium (1200). The genus of epiphytic orchids Phalaenopsis (60 species) is cultivated worldwide because of its beauty. In fact, many plants used in interior gardening are epiphytes because they have few nutrients and water requirements.

Epidendrum sp. orchids. Source: Barres Fotonatura.

Among orchids, we wanted to highlight a species known for a different reason: the vanilla (Vanilla planifolia), native to Mexico and Central America, where it was consumed with cocoa. It was imported to Reunion island and Madagascar (currently first world producers) by the Spaniards when they discovered their amazing flavor. The vanilla crops imitate their naturally grow on trees, and vanilla plants are not grown on ground, but on logs. The part of the vanilla plant that is consumed is the still immature fruit, after a curing process.

Vanilla cultivation on logs. Source: .com

Orchids have one of the most complex pollination systems throughout the plant world, with several cases of monospecific coevolution systems linked to insects and hummingbirds. Vanilla is another example, as it is only pollinated by Mexican native bees and hummingbirds, so pollination does not occur naturally in the cultivation areas and it must be done by hand. Normally, women and children still practice this handmade technique pollinating each vanilla flower to get its precious fruit. In fact, vanilla is the world’s most expensive crop, by weight.

Vanilla flower. Source: Wikipedia.com.

Bromeliads

Bromeliaceae includes more than 3,000 neotropical species, most of them epiphytic. The most species rich genera are Tillandsia (450), Pitcairnia (250), Vriesia (200), Aechmea (150) and Puya (150). The leaves of bromeliads grow in rosette facilitating the accumulation of water. The cultivation of bromeliads has been prohibited in Brazil (where we found 43% of Bromeliaceae native species) by ignorance, because it was thought that this water favored the reproduction of Aedes aegypti, mosquito transmitter of Zika, dengue and chikungunya virus. Actually, bromeliads have secondary compounds that prevent the proliferation of this mosquito eggs and larvae while the water inside the leaves creates a micro-habitat that accumulates nutrients that feed other insects, amphibians and native birds that can help fighting it. Bromeliaceae flowers have bright colors and are accompanied by showy bracts also attracting the attention of pollinators, especially hummingbirds and bats. Many bromeliads are used as ornamental plants, especially Tillandsia and Guzmania.

Tillandsia sp. Source: Barres Fotonatura.

Epiphytes from temperate climates

One of the most incredible epiphytic ferns is the staghorn fern (Platycerium bifurcatum), widely used as an ornamental plant. The staghorn fern is native to Australia but is found in all tropical areas used for gardening. This fern develops two leaf shapes: the first kind is kidney-shaped and does not produce spores; its function is to anchor to the trunk. These leaves eventually acquire a brown coloration and form a base from which the second kind of leaves grow; which are fertile and therefore produce spores. The fertile leaves are long and bifurcated and can grow up to 90 cm long. The spores of this fern are produced at the leaves apex that gain a velvet appearance.

The two kinds of leaves in Platycerium bifurcatum. Source: Barres Fotonatura.

At temperate forests, the most common epiphytes are lichens. Among lichens, we want to highlight Usnea or old’s men beard. It is a cosmopolitan genus growing on conifers and deciduous trees. This grayish fruticose lichen grow as curtain shape hanging from trees. Curiously, there is a species of epiphytic bromeliads that reminds Usnea because they share this particular growth form. Its called Spanish moss (Tillandsia usneoides) but is neither a moss or lichen, but a bromeliad with very small leaves growing chained to the ground. Nor is Spanish but lives in America.

Usnea lichen growing as a curtain on temperate climates (left) and Tillandsia usneoides of tropical climates (right): Source: Barres Fotonatura and Wikipedia.com.

The epiphytes are still little known because climbing techniques in tropical rainforest have only been developed recently so we still known a little about compared with carnivorous or parasitic plants. Many are still to discover!

Benzing, D.H. 1990. Vascular Epiphytes: General Biology and Related Biota. Cambridge: Cambridge University Press.

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