Flowers developed on plants to aid in the delivery of pollen (the powdery fertilizing agent discharged by the male of a flower) to eggs by insects. The oldest ones, magnolias, first appeared about 100 million years ago.
Before flowers came along so called “flower” plants such as ferns reproduced when parent plants released spores that flew away and grew into tiny structures called gametophytes. Then sperm cells within the gametophytes broke out and swam over to another, fertilizing its eggs. The fertilized gametophytes then developed into new parent plants. The system was fine as long as the spores fell into places that were wet enough for the sperm to swim in. Flowering plants eliminated the need for spores by having the gametophytes develop in the parent plant in the form of a flower.
Eggs are clustered in the center of flowers, each protected by a coat with a receptive spike at the top called a stigma. Pollen needs to be placed on the stigma for the flower to be fertilized. The fragrance, bright pedals and other structures of a flower were developed to capture the attention of insects, who can perceive color and smell, to get them to apply pollen picked up from the male part of the flower and apply to the stigma..
To further this objective flowers also produced nectar for the insects to feed on and marking in both color and ultra-violent light that insects to help insects land on the right spots. The problem of a flower fertilizing itself was dealt with by the flower developing the eggs and pollen at different time.
Early forms of daisy flowers were open to all comers. But this turned out be wasteful. If the pollen of one species was deposited on another species it was wasted. Over time flowers became specialized to attract pollinators that would only pollinate its own kind.
Impatients in the rainforest grow twice as large as those in the U.S.
Websites and Resources: Rainforest Action Network ran.org ; Rainforest Foundation rainforestfoundation.org ; World Rainforest Movement wrm.org.uy ; Wikipedia article Wikipedia ; Forest Peoples Programme forestpeoples.org ; Rainforest Alliance rainforest-alliance.org ; Nature Conservancy nature.org/rainforests ; National Geographic environment.nationalgeographic.com/environment/habitats/rainforest-profile ; Rainforest Photos rain-tree.com ; Rainforest Animals: Rainforest Animals rainforestanimals.net ; Mongabay.com mongabay.com ; Plants plants.usda.gov ;Books: “The Private Life of Plants: A Natural History of Plant Behavior” by David Attenborough (Princeton University Press, 1997); “Portraits of the Rainforest” by Adrian Forsythe. National Geographic articles “Rainforest Canopy, the High Frontier” by Edward O. Wilson, December 1991 ▸; “Tropical Rainforests: Nature's Dwindling Treasures”, by Peter T. White, January 1983 ∩
Parts of Flowers
Parts of a flower starting from the base: 1) stalk, or pedicle, which holds the flower to a branch, often containing a platform on which the flower is built; 2) calyx, which consists of leaflike structures known as sepals, which act to protect the flower while it is developing in a bud; and 3) the corolla, the most colorful part of the flower, consisting of pedals. The corolla surrounds and protects the reproductive organ of the plant and serves to catch the eyes of insects and other animals that carry pollen from one flower to another. [Source: Kevin Short, Daily Yomiuri]
The reproductive organs found inside the corolla are broken down into the androecium, or male series, and the gynoecium, the female series. The androecium is usually on the outside, consisting of a number of structures known as stamens, and the gynoecium is on the inside. The function of the stamen like all male sex organs is to make sperm cells and deliver them. The stamen consists of two part: 1) the anther at the tip, containing chambers where the sperm is actually produced, and the filament below which is used to position the stamen so the sperm is picked up. Sperm cells are delicate and short lived. For protection they are encased in pollen grains that can be carried by an insect or animals or by the wind .
The gynoecium is one of several highly-specialized structures called pistils. Each pistil in turn is comprised of three parts: 1) the stigma, a branched or expanded surface that exudes a sticky substance to which pollen grains arriving on an animal or the wind can adhere; 2) the style, which contains tubes that capture sperm cells released by pollen grains delivered by the stigma; and 3) the ovary at the base of the pistil which receive the sperm cells delivered by the tubes of the style. An ovary is like an egg and when it is fertilized by sperm cells it begins developing into a new organism: in this case in the from of a seed, which after it matures has to be dispersed in the wind or by some animal.
The variations among flowers and basic flower part are endless. Some species have flowers with male and female parts. Some have both flowers of both sexes on the same plant but in different places. Yet others have them on separate plants. There are flower that don’t have separate pedal put rather have unique tube-like structure. In lilies, orchids and irises the sepals are almost indistinguishable from the pedals once the flower opens.
An orchid is a terrestrial or epiphytic plant with a non-woody stem and, in most cases, a lovely flower. There are over 25,000 species of orchid in 700 genera. They make up the largest family of flowering plant and comprise nearly a seventh of all plant species. Some orchids are extremely rare and hard for gardeners grow. These sometimes produces magnificent, showy flower that in some cases bloom only once every few years. Others are common, and easy to grow. [Source: Michael Pollan, National Geographic, September 2009; Luis Marden, National Geographic, April 1971; Ogden Tanner, Smithsonian Magazine]
Orchids are found on all the continents save Antarctica in almost every imaginable habitat: deserts, rainforests, mountain tops and living rooms. About 80 percent of orchids grow in the tropics. The majority of these grow at elevations between 3,000 and 6,000 feet, and are thus are more likely to be found in montane forests or cloud forests than in lowland rainforests. Some species grow at elevations as high as 14,000 feet. All temperate zone orchids grow out of the ground while most tropical orchids cling to branches in the rainforest canopy or grow on rocks. Some orchids dangle roots that collect water from moisture in the air. Others spread across branches and gather in rainwater dripped from leaves. One even produces a root that moves around like a worm to collect water.
Orchids are unique among flowering plants in that they have a column structure that includes both male and female reproductive organs, making it possible for pollinators to simultaneously pick up pollen and fertilize flowers with each stop. Most orchid seeds are extremely tiny. Individual plants of some species produce million of microscopic seeds, which are carried from place to place in the wind.
The sweet, perfumery liquid that orchids produce is often not nectar or only has a small amount of nectar in it. The seeds tend to be so tiny the don’t even contain a food source for the developing embryo (that is provided by an endophytic fungus that infiltrates the seed, an occurrence that is rare but occurs enough to keep a species going).
Early History of Orchids
The common ancestors of all orchids lived 80 million years ago, in the late Cretaceous period, when dinosaur were in decline. They appear top have benefitted from the asteroid that destroyed the dinosaurs as orchids spread across the globe after the mass extinction of dinosaurs and before the rise of mammals. All of this was determined from some orchid pollen found on the back of a 20-million -year-old bee trapped in piece of amber in the Dominican Republic. The findings were reported in a article in Nature by Harvard researcher Santiago Ramirez, who extrapolated back in time and built a “family tree” for orchids using a “a molecular clock” that used DNA mutations to estimate the divergence between living organisms.
The word orchids is Greek for testicles. Theophratus, the father of botany, gave these plants that name because he thought their orb-like roots resembled parts of the male anatomy they were named after. Medieval herbalists believed that eating orchids produced desire among women, because the flowers resembled female sex organs, and increased the likelihood of giving birth to a son. Vanilla comes from an orchid that was introduced to Europe by the Aztecs.
Later History of Orchids
Charles Darwin was fascinated by orchids. He called them “as perfect as the most beautiful adaptions in the animal kingdom.” The first book he published after “On the Origin of Species” was “The Various Contrivances by Which Orchids are Fertilized by Insects”. It painstakingly detailed how each part different orchids’ flowers served some reproductive function.
Darwin was perplexed how natural selection could create such complicated structures and botanist have been trying to come up with explanations ever since. The artist Georgia O’Keefe was fascinated by orchids and their resemblance to human female sexual anatomy.
In the 19th century orchid raising became the rage among the aristocracy in Europe, especially in Victorian England, where men especially pursued the passion despite the “blatant sexuality” or orchids. The earliest commercially grown tropical orchids were raised in the early 18th century from dried specimens. The first human-hybridized orchid blooms in 1856.
At that time raising orchids outside of their habitat was difficult because they relied on specific kinds of fungi to help them generate food. Conditions not only have to be right for reproducing for the orchids but also had to be right for growing the fungi as well. The realization that certain kinds of fungus are necessary for germination did not occur until 1904. And it wasn’t until the 1930s that a technique was developed for germinating orchid seeds in specially enriched jellies that provided nutrients their fungi would have been provided in their natural environment.
Various advances in the 1920s and 1960s made it possible to grow to mass produce orchids and exotic hybrids, some of which now sell for over $100,000. Today there are over 100,000 registered hybrid orchids, many made form improbable combinations with bizarre results.
What is and what isn't an orchid is not clearly defined. "The orchid world is divided into what we call 'lumpers' and 'splitters'", Peter Hunt of Kew Gardens in London told National Geographic, "Those who want to reduce the mass of described orchids to few species, and those who try to subdivide them further still."
Kinds of Orchids
Orchids produce a dazzling variety of flowers. Species from Australia look like bearded hillbillies and bug-eyed donkeys. The Mediterranean Ophrys resembles a female wasp and gives off an odor that attracts pollinating male wasps. The Guatemalan tiger orchid has a bee platform that looks like Santa Clause.
The smallest orchid blooms, from the cloud forests of Venezuela, are small enough fit on the head of a pin, and largest orchid flowers are over a foot across. The plants of some species are over 100 feet long. One species from Malaysia and the Philippines produce plants that weigh over a ton and produces 10,000 flowers each blooming season.
The Javanese dendrobium produces a bloom that lasts of for only five or six minutes. The flowers of most orchids however are very long-lived, lasting for several weeks or several months. Some produce a heavenly scent, some smell like rotten meat and other produced blooms that look spiders, slippers, bumblebees, buckets dancing ladies and have been named accordingly. Some flowers have developed custom tubes that are form fitted for specific species of moth.
The dendrobium orchid, which is collected by the truckload in the Kachin Province of Myanmar is used in Asian and Ayurveda medicine and in some places is more highly valued than ginseng. There has been some discussion of cultivating the orchid commercially and making medicines with it.
An unusual species of white orchid — the star orchid — found in Madagascar holds nectar at the extreme end of a foot-long spur. Darwin postulated in the 19th century that there must be a species of moth with an 12 inch proboscis that could reach the fluid and pollinate the flower. Even though he was scoffed at by other scientists 40 years later a night-flying hawk moth was discovered in the island with a 12 inch tongue.
Hundreds of new orchid species come to light every year. The search is fueled by a lucrative market for new species and the willingness of orchid hunters to search remote jungles for new species
Deception is a key to orchid reproduction. Michael Pollan wrote in National Geographic, “A third of orchid species long ago figured out, unconsciously of course, that they can save on the expense of nectar and increase the odds of reproducing by evolving a clever deceit, whether that ruse be visual, aromatic, tactile, or all three at once. Some orchids lure bees with the promise of food by mimicking the appearance of nectar-producing flowers, while others, as in the case of “Dracula” orchid, attract gnats by producing an array of nasty scents, from fungus and rotten meat to cat urine...Some orchids promise shelter, deploying floral forms that mimic insect burrows or brood rooms. Others mimic male bees in flight, hoping to incite territorial combat that results in pollination.”
The orchid’s reproductive strategy results in a lot of species but small number of each species, which explains why new orchids are constantly being discovered and searched for in far-flung places. Deception only works if the pollinators are fooled. If a deception becomes widely known insects will not be fooled anymore and the reproductive strategy no longer works. The strategy also works because orchids get a lot of mileage from the few insects that are fooled.
John Alcock, an evolutionary biologist who wrote “An Enthusiasm for Orchids”, has postulated that the reason why orchid reproduction is not an easy and straightforward process with plentiful supplies of nectar is because with that method pollinators are most likely to fertilize the nearest orchid, which could lead to inbreeding and poor quality offspring. By having a reproductive process that is so complex and frustrating, resulting in little or no nectar, pollinators are likely to skip nearby orchids not wanting to go through the same ordeal for little reward, and are more likely to try again at some distance away after “forgetting” about the frustrating experience.
Perhaps the main reason orchids have such elaborate reproduction strategies is that they seek to develop a relationship with a highly specialized pollinator that it knows is likely to deliver the goods and not waste energy in creating a lot of nectar that any creature can indulge in. If you create a flower that attract one kind of bee then it is likely that that bee will deposits pollen on another orchid of the same species in another location.
Bees, Wasps, Orchids and Sex
Some orchids attract male wasps with smells of a mating female wasps and flowers that resemble female wasp. Males attempt to copulate with the orchids and in doing so pick up pollen that they pass on to the next orchid they try to have sex with. Different orchids imitate bee females in different position so the males try copulating with them in different positions.
One species of orchid,the “Ophrys”, found on the large Italian island of Sardinia, is known to botanist as the “prostitute orchid” because of the way it employs “sexual deception” and “pseudo copulation” to spread its pollen. The orchid mimics a female bee in appearance and touch and gives off a scent similar to the pheromones released by female bees. Male bees are so fooled by the deception they literally try to mate with the flower, or in the words of one botanical reference book the bee performs “movements which look like an abnormality vigorous and prolonged attempt at copulation.”
During the commotion the male bee jostles the orchid’s column and two yellow pollen-filled sacs are stuck to his back with a quick-drying gluelike substance and carried off by the bee after the mating attempt is finished. Each pollen sac carries an enormous amount of sperm and pollen and each ovary contains a huge number of seeds. So if a pollinator successfully make his pick up and delivers it to another blooming orchid of the same species the result is a lot of fertilized seeds.
You can watch a You Tube video of wasp mating with an Australian tongue orchid and actually ejaculating on it. What is extraordinary about this is that females of this species of wasp (“Lissopimpla exclesa”) are capable of reproducing without males and giving birth to only male offspring. All this works to the orchid’s favor: there are more males to have sex with the orchid and because there are relatively few females the males are more likely to be less picky and have sex with flowers rather than real female wasps.
Bucket Orchids and Bees
Bucket orchids are found in the high canopy of forests in Central America. The twenty or so species produce perfumey liquids that all smell more or less the same to humans but smell quite different to little iridescent bees that come in different species, each responding to the perfume of a different species of bucket orchid.
Bucket orchids contain two petals that act as gates, a bucket with perfumey nectar and a pollen-filled tunnel. Male bees are attracted by the nectar which they spread on their bodies for later use in an elaborate courtship ritual to attract females. Sometimes males pass through the gate-like petals, dunk themselves with nectar, escape through the pollen-filled tunnel and fly off to other orchids and pollinate them.
Some varieties of bucket orchid produce nectar that intoxicates bees and causes them to fall into the bucket. The only way out for the bee is through a spout covered with pollen. Without this system the bee would just feed on the nectar and not pick up the pollen.
Describing euglossine bees at work on a bucket orchid Michael Pollan wrote in National Geographic, “Visiting bees busy themselves scraping fragrances from the waxy source of the flowers, using their front legs they then transfer the scents to tibia sacs carried in their rear legs like little wallets...Most animals that rely on scents to attract a mate produce it themselves; not the euglossine bee, which forages for a specific set of ingredients, getting them only from orchids but also from certain leaves and fungi, and then mixes up the perfume by ‘hand.’”
“As the bees jostle each other for scents, one or more is apt to lose his footing on the slick petal and plunge into the bucket. This would not be a problem, except the viscous liquid in the bucket renders the bees’ wings temporarily useless. So the bee struggles mightily to clamber up the slippery walls of the bucket until he stumbles upon a series of steps, which conduct him up and out of the pool through a narrow passageway leading out the back of the flower. As the dazed and sopping bee squeezes himself through the tunnel, he passes beneath a spring-loaded device that (you guessed it!) claps a pair of yellow pollinia on his back.” If all goes according to plan the bee will go through the same ritual at another bucket orchid “and on his way through the tunnel unwittingly snags his yellow backpack on tiny hooks adapted for precisely that purpose. Pollination accomplished the bucket orchid closes up shop, collapsing its extravagant petals into a wad of crumpled yellow tissues.”
Image Source: Mongabay mongabay.com
Text Sources: “The Private Life of Plants: A Natural History of Plant Behavior” by David Attenborough (Princeton University Press, 1997); National Geographic articles. Also the New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Natural History magazine, Discover magazine, Times of London, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.
Last updated March 2011