What Are Epiphytes?
An organism is an individual plant or animal that lives permanently attached to soil, water, sunlight and other elements. They are able to survive without any of these things but they cannot live in complete isolation from them. Plants and animals have many types of cells called ‘epithelial’ which line their surfaces. These cells produce various substances (called ‘endophytes’) that allow the organisms to grow and thrive.
The word ‘epiphyte’ comes from Greek meaning “leaf” and refers to a plant with leaves. The term was first used in 1842 by botanist William Buckland, who described several species of algae growing on rocks in Scotland’s Loch Lomond National Park.
Epiphytes are plants that grow on the ground and do not require light to grow. Some epiphytic plants include mosses, lichens, ferns, mosses and some flowering trees such as poppies. Other epiphytic plants include certain fungi and bacteria found in soil or water.
If the epiphytes are growing on a living plant, the epiphyte is called a ‘parasite’ or ‘pathogen’ as it drains nutrients from the living plant. However, if the epiphytes are growing on a dead plant then it is called a ‘mutualist’ or ‘symbiote’ as it benefits the host plant by making it more attractive to animals or improves its soil.
Adaptations Of Epiphytes
Due to the epiphyte’s lack of soil, it must find other ways of getting the nutrients it needs. Most epiphytes have developed methods of collecting the water and nutrients they need from rain or moisture in the air. Instead of producing its own food through photosynthesis, many epiphytes get their energy by collecting dust and bits of organic matter from the air.
An alternative way of getting nutrients, is to trap and digest insects that land on the epiphyte’s leaves. The process of trapping insects is called ‘pitfall trapping’ and is a very successful form of feeding for many epiphytic plants. Pitfall trapping involves the epiphyte developing little indentations in its leaves. When an insect lands on the plant’s leaf, it often accidentally falls into one of these indentations.
The final way that epiphytes collect nutrients is through ‘mimicry’. Mimicry involves the epiphyte having a similar physical appearance to another organism, which makes it attractive or even essential to a particular animal. Many orchids use mimicry to attract male insect pollinators. The orchid has evolved to imitate the look of a female insect to attract the male insect.
A common way that epiphytes collect nutrients is through ‘commensalism’ in which one organism (the commensal) benefits from a relationship with another organism (the host), but neither hurts nor helps the other. A good example of this is when fungi grow on the roots of a tree without damaging the tree. The tree provides the fungus with a suitable environment including water, warmth and nutrients. The fungus in turn produces enzymes that break down the tree’s cellulose fibers, allowing the tree to access nutrients such as nitrogen, that would otherwise be unavailable to it.
Epiphytes also collect moisture and nutrients from dust and debris that accumulate on their leaves. If the epiphyte is an insect, then it can also collect food from feeding on the sap of the epiphytic plants.
The vast majority of epiphytes are actually single celled organisms such as ‘protists’. The protist benefits by getting its nutrition from dead organic matter and dust, which it filters out of the air.
The Orchid Epiphyte
Perhaps the most famous epiphytes are orchids. There are 25,000 different species of orchid and all of them are epiphytes. Orchids are so closely linked with epiphytes that the word ‘epiphyte’ is often used to refer to orchids.
The main adaptation of an orchid is its method of pollination. Most orchids have highly specialized flowers that mimic the appearance of a female insect to attract male insects. When the male insect tries to mate with the flower, it picks up pollen from the orchid’s anthers (male part of a flower that produces pollen), which it then transfers to the stigma (female part of a flower that receives pollen).
The process of attracting insects involves brilliant colors, subtle scents and shapes that are similar to female insects. The result is that orchids have become one of the most diverse and successful groups of flowering plants.
There are various types of orchids including ‘Epidendrums’, which are terrestrial orchids that produce small flowers and usually grow in clusters on the ground.
The largest orchid in the world is the ‘Gastrorchis’, a tropical plant that can grow up to 9 feet tall and has a lifespan of around 40 years.
The ‘Vanilla planifolia’ is an orchid that is grown in plantations and used to produce vanilla.
The ‘Anggrek Bulan’ or Moon Orchid is one of the most popular orchids in Indonesia, which grows in the flowers on trees at high altitude. In Java there are hundreds or even thousands of moon orchids growing on a single tree. The flowers only last one night before wilting.
Orchid colors range from the usual purple, pink and yellow varieties to some very unusual colors including red, black, yellow-green and dark green. There are also albino orchids that lack all color.
Orchids have been cultivated by humans for over a thousand years. The Chinese Emperor Shennong is thought to have mentioned orchids in his book ‘The Herbal’ that was written in around 3000 BC. Native Americans were growing orchids in Ecuador and Columbia 1,000 years ago.
The Cattleya is a popular orchid with flowers that can grow to around 10 inches in diameter. The Laelia is a small and delicate looking orchid that has re-blooming abilities (meaning it produces a second flowering after the first one has been harvested). The Dendrobium is a common orchid with flowers that last for several months.
The Bulbophyllum is a small orchid that grows in clusters of flowers and has numerous small petals and sepals. The ‘Vanda’ is one of the largest orchid groups with over 200 different species.
At present, there are over 25,000 known orchid species, however in the Amazon rainforest there are estimated to be around 100,000 species still to be classified.
Orchids are some of the most endangered plants in the world. The ‘Epipactis Palustris’, a rare orchid that grows exclusively in wetland habitats in the Netherlands, was once found in over 100 locations. Today, it can only be found in 3 locations, all of which are threatened by human intervention because the areas are slated for conversion into farmland.
The Catasetum is an orchid that grows in parts of Southern America. At one time it was hunted for food, until it became endangered. It is thought that all Catasetum species now exist in cultivation.
The Dendrobium Phalenopsis is an orchid that was believed to be extinct in the wild until a small population was discovered in 1981 growing on rocky limestone cliffs.
Poaching and over collection are major contributors to the decline of orchid populations. Even in areas where orchids are more common, species such as the ‘Brachycoria Mandaica’ are so popular among collectors that they have been completely wiped out.
Orchids are also threatened by human intervention in their natural habitats.
Sources & references used in this article:
Microclimate, light adaptation and desiccation tolerance of epiphytic bryophytes in two Venezuelan cloud forests by Y León‐Vargas, S Engwald… – Journal of …, 2006 – Wiley Online Library
Vascular plants as epiphytes: evolution and ecophysiology by U Lüttge – 2012 – books.google.com
Determinants of epiphytic fitness in bacteria by SE Lindow – Microbial ecology of leaves, 1991 – Springer
Gas exchange and water relations in epiphytic orchids by CJ Goh, M Kluge – Vascular plants as epiphytes, 1989 – Springer
Epiphytic fitness of phytopathogenic bacteria: physiological adaptations for growth and survival by GA Beattie, SE Lindow – Bacterial pathogenesis of plants and animals, 1994 – Springer