Plants Behaving Badly (2014) s00e02 Episode Script
Sex and Lies
Hidden in these rainforests are plants that helped shape.
Our modern view of biology.
Orchids.
Exotic, bizarre.
Mysterious blooms in romantic faraway places.
But in nature such beauty.
Serves a purpose.
The vitally important purpose.
Of helping orchids make more orchids.
Behind their beauty there's another side to orchids.
A darker side, a world of trickery and fraud.
As they try to make certain they're pollinated.
The private life of orchids is so intriguing.
It caught the attention of Charles Darwin.
To help shape his Theory of Evolution he made detailed studies of orchids.
And discovered a world so strange he could hardly believe it.
But generations of scientists since have uncovered stories.
Far stranger than Darwin discovered.
Stories of deception and dishonesty in pursuit of pollinations.
That defy imagination.
Orchids are the largest family.
Of plants in the world.
At the last count there are at least 25 thousand different species of orchids.
World wide.
Around one kind of plant in every 20 is.
An orchid.
And their diversity is astounding.
They range from the tiny and inconspicuous.
Like mask orchids and frog orchids familiar to Darwin on the hills near his home in Sutton, England, to the most dramatic.
Lowe's mini slipper with a flower spike.
Nearly a meter long.
This specimen is growing in a very special forest.
A hotspot for orchids, on the slopes of Mount Kinabalu.
In Borneo.
This is a botanists' paradise Anthony Lamb has been exploring these forests for fifty years.
And he's still making new discoveries.
We're actually nearly 1600 meters on Mount Kinabalu.
In fact, this forest right here.
Is probably the richest in terms of plant diversity.
Of all the forests of Borneo.
We can see that the trees are very mossy.
There are orchids climbing up.
The diversity is huge.
Kinabalu is one of the richest places in the world for orchids.
Fifty percent of all orchids on Borneo are found around Kinabalu.
That's over 860 or 870 species.
And we're going to go on finding new species and new.
Records.
I really wouldn't be surprised if eventually we get up to.
Nearly 900 species in Kinabalu in the long term.
That's nearly four times as many species as in the whole of Europe.
Just in the rainforests cloaking this one mountain.
There are so many orchids here that some kinds.
Have only ever been seen once before.
You can see how thick this forest is, something like over 100 species of orchids.
That have been found on Mount Kinabalu, are only known.
From one collection.
We've recently been finding species that were discovered 70 to 100 years ago and are now.
Being only collected for the second time.
Of course they have never been photographed before.
Almost nothing is known about many of these orchids.
There are surprises everywhere.
A pure blue orchid.
And this one.
Hosts a colony of ants.
These ants.
Are farmers; they tend tiny bugs.
The bugs suck the orchid's sap and turn it into a sweet liquid.
That the ants love.
The ants are continually moving their miniature herd around.
And the bugs when picked up respond by embracing the ant around its neck.
And holding on.
With ants to guard them, the defenseless bugs can feed without worry.
And that's just one story.
Many more await discovery in these rich forests.
But you don't have to travel to remote rainforests.
To see spectacular orchids.
All across Europe orchids grow.
In impressive displays, even alongside road verges.
They also grow in abundance on the Chalk Hills of Southern England.
And it was these displays that drew Darwin's attention.
He named one of his favorite places.
OrchÃs Bank, a natural laboratory within easy reach of his home.
Down House, in Kent.
In 1859 Darwin published "On the Origin of Species".
Outlining his ideas on how species could change and evolve.
By a process he called natural selection and how this gave rise to the tree of life.
In all its diversity.
But could natural selection really explain the rich variety of animals and plants.
That we see around us.
Many scientists of Darwin's day thought not Darwin knew he needed more detailed studies to strengthen the ideas behind.
His theory.
He was meticulous in his observations and experiments.
And began to look for evidence of natural selection in the plants.
And animals around his home.
He soon became entranced by orchids.
By the ingenious ways that their flowers are adapted.
To make sure that pollen of one plant finds its way to another of the same species.
Soon after starting his studies, he wrote.
In my examination of orchids hardly.
Any fact has struck me so much as.
The endless diversity of structure for gaining the very same end.
Namely, the fertilization of one flower by the pollen of another.
Such cross-pollination.
Maintains genetic variety in the population.
With raw material for the natural selection proposed by Darwin's theory Darwin soon realized that orchid flowers.
Were very different from those of other plants.
Many familiar flowers have identical petals arranged around the sexual organs of the plants.
In orchid flowers.
One petal is often very different.
We now know that this is because orchids have a peculiarity in their genetic code.
Known by botanists as the orchid code.
This allows orchids to evolve individual petals in different ways.
Creating this extraordinary diversity.
In particular, the lower petal, the lip.
Has evolved an almost unbelievable variety.
Of shapes and designs.
The lip has allowed orchids to come up with some very unusual ways.
Of making sure pollination happens.
One of the strangest examples grows here in the Appalachian Mountains in the United States.
These ancient mountains are cloaked in spectacular forests.
Growing beneath the canopy are several kinds of ladies slipper orchids.
The pink ladies slipper.
The yellow ladies slipper.
The lip is swollen into a huge hollow structure bearing some resemblance to a shoe.
The ladies slipper, with a hole in the top.
Bees are drawn to the bright colors of the slipper.
And eventually enter the hole.
Once inside, they can't get out the way they came in.
The sides are too steep and slippery.
But there is a way out, a narrow passage.
At the base of the flower.
It's a tight squeeze, but the bee can sense freedom and keeps struggling.
This escape route forces the bee close to the orchid's pollen.
And as it passes the orchid glues a sticky mass of pollen to its back.
A little disoriented by its adventure the bee soon recovers.
And this is the reason for the diversity of orchid flowers.
As Darwin realized long ago.
It's aimed at one thing: persuading pollinators to carry pollen.
From one plant to another.
The bee is soon drawn to another ladies slipper and once again.
Ends up inside the hollow lip.
This time it knows the way out and as it squeezes through the narrow channel.
The pollen on its back is rubbed off on the female part of the flower.
Success for the orchid.
Many plants don't need help from insects.
Grasses dangle their stamens in the breeze.
And shed huge amounts of pollen on the wind.
It's purely luck if a few grains land on a female flower.
Of the rightt species.
Orchids don't rely on the wind, they depend on.
Insects to move their heavy pollen area from one plant to another.
Early in his studies, Charles Darwin showed that orchids.
Need insects.
In a simple experiment.
He carried out one spring.
Even today, in spring in southern England, sees a few ancient meadows.
Put on a dazzling display of wildflowers.
These sights would have been much commoner in Darwin's day.
The bright yellow of cowslips mingles with the purple.
Of green winged orchids.
And green wing orchids were the subject.
Of Darwin's experiments.
He covered some of the orchids with a glass bell jar.
To exclude any insect visitors and waited.
The orchids in the meadow set seed normally and produced pods.
Full of seeds.
But those covered by the jars failed to develop any seed pods.
Without insects, they hadn't been pollinated.
So orchids need to attract insects but how? Most plants use.
A sugary liquid, nectar, high energy flight fuel.
For insects, and some orchids.
Do the same.
A common twayblade.
With tiny green flowers, but these flowers release so much nectar it runs down the lip in a sticky river.
Which attracts all kinds of insects.
Small wasps.
Are frequent visitors.
The wasp, works its way up the lip feeding on the nectar.
When it gets to the top it bumps into the pollenia.
And the orchid glues some to its head.
Eventually, the wasp will leave to find more nectar, hopefully.
From another twayblade, and in doing so it will cross-pollinate the plant.
But the twayblade's nectar is so.
Easily available it attracts all kinds of insects.
Some, far less useful as pollinators.
Flies.
And beetles.
The swollen-thighed beetle gorges itself on the twayblade's nectar.
And it doesn't seem to notice.
As more and more pollenia are glued to its head.
Meanwhile.
This fly has sucked up so much nectar it must regurgitate it.
So that some of the water in it evaporates and concentrates the nectar.
Then it sucks the liquid back in.
Yet it has avoided picking up any pollenia at all.
The beetle now has so many pollenia stuck to it.
That it is hard for it to feed, but it's strong enough.
To just scrape them off.
These pollenia contain all the pollen from that flower.
If they are destroyed, then that particular flower has no chance of pollinating another.
And, if the insect fails to deliver it to another orchid of the same species.
All the pollen will again be wasted, unlike grass flowers.
Every orchid flower has only one chance to get it right.
Yet, as summer unfolds each and every insect is spoiled for choice when it comes to other sources of nectar.
Countless flowers, all offering rewards.
For insect pollinators.
How can an orchid make it more likely that an insect will visit another orchid of the same species? With its precious load of pollenia.
The fragrant orchid has one way.
Each flower has a long tube projecting out behind it.
And the orchid only produces nectar towards the tip of this spur.
It can be seen clearly through the spur's thin walls.
But it can only be reached by.
Insects with long tongues like butterflies.
A painted lady butterfly takes a little time to find the entrance of the spur.
With its long tongue, so once it's learned the trick.
It has an exclusive supply of nectar open only to long-tounged insects.
It must probe deep to reach the nectar and as it does the orchid glues its pollinias to the butterfly's tongue.
Since it won't have to compete with a lot of other insects for nectar.
It makes sense for the butterfly to find another fragrant orchid and as it feeds.
It now pushes the pollen onto the female parts.
Of the fragrant orchid flower Darwin was beginning to understand the way orchids are adapted to exploit insects.
But one orchid proved a real test.
For his theories.
He was sent a species of orchid from Madagascar - a comet orchid.
Like the fragrant orchid, this species had a spur.
But Darwin measured the spur as over a foot long.
What on earth could pollinate this orchid Darwin made a bold prediction: there must be a moth.
In Madagascar with a tongue to match the orchid.
It wasn't until after Darwin's death.
That the hawk moth, with the predicted foot-long tongue was found and then just a few ago, scientists saw the moth in action.
Entomologists filled the fleece.
Travelled to the forests of Madagascar to stake out a comet orchid at night high in the canopy with infrared cameras.
Nothing to do now but wait.
There it is.
It's hovering in front of the orchid.
The tongue out, look! Awesome! Final Proof, 143 years after Darwin's prediction Darwin would doubtless have felt the same.
Unbelievable.
From an orchid's point of view a close partnership with one or just a few species.
Produces the most reliable pollinators.
And in tropical America some species found an ingenious way of doing just that.
Orchid bees.
These bees are all male.
They flock to certain orchid species in large numbers.
But they are not after nectar.
Instead, this orchid produces an oil which the bees.
Scrape up with their front legs.
Then, in flight, they transfer this to large pouches on their back legs.
Here it's converted into a chemical that female orchid bees find irresistible.
Only orchid bees have any use for the orchid's oil.
So, like the comet orchid and the hawk moth in Madagascar.
These tropical American orchids have formed.
An exclusive relationship and turned orchid bees.
In a reliable delivery service for their precious pollenia.
But some orchids produce no reward, no nectar.
No oils, nothing.
The green-winged orchid shown by Darwin to depend on insects.
Is one such miserly flower.
Yet Darwin flatly refused to believe that some orchids produced no nectar at all.
Why would an insect visit a flower for no reward? He thought that insects were too smart to waste their time on flowers with no nectar.
So he made careful dissections of green wing orchids looking for nectar - he found none.
But was convinced that it must just be hidden in some way.
But this time Darwin was wrong.
We know that around one third of all orchid species produce no reward at all.
So why do lots of insects fall for what Darwin called so gigantic an impostor? To an insect the green-winged orchid looks like the kind of flower that should produce nectar.
And is surrounded by many other species that are rich in nectar so it's worth investigating and as the bee probes in vain for the nectar it picks up the orchid's pollenia, but soon leaves.
Still hungry, to look for a more rewarding plant.
If this is devious.
Other orchids are downright dishonest.
Narrow-leafed helleborine growing not far from Darwin's home.
They share this forest with a close relative.
The white helleborine Darwin was familiar with both of these plants.
And examined them closely.
He found that the white helleborine has yellow ridges on the lip.
And observed that these were often nibbled by insects.
Though he never saw the culprits.
The narrow leafed helleborine has even bigger yellow patches Darwin thought that they were some kind of food for visiting insects.
An alternative to nectar, but it has recently been suggested that.
That these patches mimic the loose pollen of other plants.
Many insects eat pollen, although they don't find the sticky pollenia of orchids.
Very appetizing, so this is a farce.
That the orchid uses fake pollen to attract insects by deceit.
Many of the 25,000 kinds of orchids are dishonest.
And some use not the promise of food, but the promise of sex.
Bee orchids.
There are many kinds of bee orchids and the lips of their flowers have come to.
Resemble different insects.
To attract pollinators they need to convince male bees.
That the lip really is a female bee, but surely male bees would never be fooled by such a crude mimic.
To find out how the orchid succeeds.
We need to visit a colony of these bees.
In early spring, the air is buzzing with male bees.
They spent the winter underground, in the nests where they grew as larvae.
Males emerge before females.
And now they are hunting for the first females Female bees release.
A particular scent, a male can even smell a female still hidden underground.
And in his eagerness tries to dig her out.
Eventually, The first females emerge.
Almost immediately she's pounced on by males.
Often many of them.
The males have a good reason for this frenzy.
A female will only mate once, so it's vital.
To be first there.
Males have to be quick if they want to mate.
No time to be discerning as long as it smells right.
He doesn't hesitate and that's what the orchid depends on.
A bee orchid flower releases a similar chemical mix to a female bee.
It's a close enough match that eager males pounce on the flower and try to mate with it.
As they do so they pick up.
The orchid's pollen.
It's a devious trick, but a risky one.
As Darwin long ago suspected insects are smart enough to know when they're being duped.
And only a very few of these bees will fall for the same trick twice.
But if being deceitful.
Is such a risky pollination strategy, why have so many orchids given up producing only a reward, like nectar Darwin simply couldn't believe that the green-winged orchid could be cross-pollinated without producing nectar to attract pollinators and as only recently discovered what this orchid is up to.
A devious trick to make cross-pollination even more likely.
The orchid's plan becomes obvious if artificial nectar is added to the flowers.
In this experiment scientists dosed some plants with nectar and left others free.
They then recorded the behavior.
Of visiting insects.
Bumblebees are the main pollinators of this orchid, and the scientists weren't surprised that the bees spent far longer on the flowers with artificial nectar drinking their fill.
On the normal plants they spent only a fifth of the time.
A quick check of different flowers to see if there's any nectar.
And then, disappointed, they move on.
But the scientists also watched what happened to the pollen picked up by those bees.
Spending longer on plants with nectar greatly increased the chance that the bee would just move pollen between flowers on the same plant - self-pollination - not what the plant wants.
Though, by not producing nectar.
The orchid makes it more likely that the bee will leave and carry the pollen to a different plant.
The plant that so puzzled Darwin.
Now seems to fit his ideas perfectly, a clever adaptation.
To encourage cross-pollination Darwin missed this story.
But he did discover some adaptations just as ingenious.
In his own studies.
In early spring the woodlands near his home were carpeted with wild flowers.
Amongst these there's a tall and stately orchid.
The early-purple orchid.
This was the first orchid that Darwin studied.
He found that even the pollen masses themselves have a very clever way to ensure cross-pollination.
He extracted the pollinias using a sharpened pencil.
To mimic the probing tongue of an insect.
The polynia stuck to the pencil.
Just as they would to an insect.
At first, nothing happened, then after about half a minute he saw something amazing.
The stalks holding the pollen masses began to bend forward Darwin realized what this meant.
Each pollen mass was now lined up to meet the female part of the flower.
And the orchid delays the bending long enough for the insect to finish feeding on that plant.
By the time the pollinia are aligned to hit the female part of the flower the insect will have left the first plant and have carried the pollen to another.
When an orchid is finally pollinated.
It produces thousands of seeds.
There are so many, the plant can't afford to make big seeds.
Instead orchids seeds are like dust, they blow on the wind.
And because they are so small they can't contain any food supplies for developing seedlings.
To germinate and grow orchids must use yet more deception.
When we see a forest, we see a collection of trees and other plants.
But that is only one way of viewing it.
We need to look at the forest in a different way the way an orchid sees it.
At the microscopic level, the forest floor is a mass of fine filaments.
The threads of fungi.
Spreading right across the forest.
We normally think of fungi as the mushrooms that spring up from the forest floor each autumn.
But these are just the structures that produce the spores, the reproductive organs of the fungus.
The bulk of the fungus is underground; this is decomposing and digesting the material that falls onto the forest floor.
The fungal threads connect with the roots of the trees, the fungus supplies the tree with certain nutrients.
And in return the tree passes the fungus sugars.
That are made by photosynthesis in its leaves.
So the forest is like one huge.
Superorganism and the orchid seed is a parasite.
Fungal threads penetrate the seed to try to decompose it.
But the seed contains fungicides that stop the threads from overwhelming it.
Now the orchid seed can steal nutrients from the fungus.
To fuel its own growth.
Most orchids maintain a relationship with fungi.
Even after they grow their own leaves and can make food for themselves.
But some take this to an extreme.
The bird's nest orchid.
It has no leaves at all.
It simply produces its pale coloured flower spike.
Each summer.
It depends for all of its food on the fungal threads running through the forest floor.
In turn, the fungus gets much of its food from the trees, so the orchid is connected to the trees.
And makes use of their leaves held high in the sunlight.
Each kind of orchid depends on very specific fungi.
To germinate and grow, which makes orchids.
Very difficult to grow in cultivation.
World-wide many orchids are threatened with extinction, so growing them successfully to put back in the wild is critical.
The Everglades in southern Florida a vast area of swampy grassland.
Running through this river.
Of grass are long strips of forest.
Strands.
Dense, often impenetrable and infested with mosquitoes.
This is Fakahatchee strand, it may look uninviting.
But it hides a real treasure.
And this is it.
A ghost orchid.
For most of the year, this is all we get, a few roots.
It has no leaves, but the roots are green and photosynthesize.
To provide the orchid with food.
And then the summer brings rain to replenish the swamps it transforms.
In the flickering sunlight of the dark forest it opens an exquisite flower, perhaps the most sought after of all orchids.
There are only around 2,000 ghost orchids in the whole of South Florida, all of these sites are closely-kept secrets.
They have to be.
Remote cameras hidden in the swamps catch poachers emerging with armfuls of rare orchids.
There is still a demand world-wide for orchids stolen from the wild.
Help for such threatened orchids comes from an unlikely source.
Writhlington School in Somerset in the UK.
It looks like any other school.
But in its grounds are state-of-the-art greenhouses.
Part of Writhlington's International Orchid Project.
In the greenhouses, students grow.
Over a thousand different kinds of orchids from all over the world.
They're using all the same techniques for cultivation as used by the biggest botanical gardens.
And they have spectacular results.
The school has its own propagation lab, where seeds can be germinated and plants grown on.
The school produces thousands of plants each year.
And these plants allow the school to help orchids world-wide.
The orchids are carefully tended in the greenhouses.
And then sold.
Part of the money raised goes into funding.
Trips to some of the most exotic places a student could imagine.
In the past we have had several in Central America.
Central and South America: Brazil, Belize, Guatemala.
There are plans to go to Rwanda there is a Canada trip and a second trip.
In many of these places.
The students help local botanists and conservationists set up labs to cultivate their own orchid species.
The Laos expedition was the last one to go on, where we helped Eddie and Suk, our contacts out there, set up a lab in Laos, which is the first lab in southern Laos to grow orchids from seed.
Because the big problem out there is wild collection.
Because people steal them.
Cultivating orchids in all these countries.
To supply collectors is reducing threats to wild populations.
And in the process the students at Writhlington get to know perhaps the most amazing plant family of all.
People enjoy being part of something that is.
Truly special is probably the best.
Plant family to be involved in, I think.
Yes, I love it.
In their passion for the world's largest family of plants.
They are following in the footsteps of Charles Darwin.
A new generation inspired by these remarkable plants.
And there is still plenty left for them to discover.
One of Darwin's favorite orchid sites was Downbank near his home.
Perhaps he had this place in mind.
When he wrote the final sentences of the Origin of Species.
It is interesting to contemplate.
An entangled bank, clothed with many plants of many kinds.
With birds singing on the bushes with various insects flitting about.
There was, he wrote, grandeur in this view of life.
But the very last sentence in The Origin seems particularly appropriate.
To orchids.
Endless forms, most beautiful.
And most wonderful, have been and are being evolved.
Endless forms that have helped orchids to become.
The most successful family of plants on the planet
Our modern view of biology.
Orchids.
Exotic, bizarre.
Mysterious blooms in romantic faraway places.
But in nature such beauty.
Serves a purpose.
The vitally important purpose.
Of helping orchids make more orchids.
Behind their beauty there's another side to orchids.
A darker side, a world of trickery and fraud.
As they try to make certain they're pollinated.
The private life of orchids is so intriguing.
It caught the attention of Charles Darwin.
To help shape his Theory of Evolution he made detailed studies of orchids.
And discovered a world so strange he could hardly believe it.
But generations of scientists since have uncovered stories.
Far stranger than Darwin discovered.
Stories of deception and dishonesty in pursuit of pollinations.
That defy imagination.
Orchids are the largest family.
Of plants in the world.
At the last count there are at least 25 thousand different species of orchids.
World wide.
Around one kind of plant in every 20 is.
An orchid.
And their diversity is astounding.
They range from the tiny and inconspicuous.
Like mask orchids and frog orchids familiar to Darwin on the hills near his home in Sutton, England, to the most dramatic.
Lowe's mini slipper with a flower spike.
Nearly a meter long.
This specimen is growing in a very special forest.
A hotspot for orchids, on the slopes of Mount Kinabalu.
In Borneo.
This is a botanists' paradise Anthony Lamb has been exploring these forests for fifty years.
And he's still making new discoveries.
We're actually nearly 1600 meters on Mount Kinabalu.
In fact, this forest right here.
Is probably the richest in terms of plant diversity.
Of all the forests of Borneo.
We can see that the trees are very mossy.
There are orchids climbing up.
The diversity is huge.
Kinabalu is one of the richest places in the world for orchids.
Fifty percent of all orchids on Borneo are found around Kinabalu.
That's over 860 or 870 species.
And we're going to go on finding new species and new.
Records.
I really wouldn't be surprised if eventually we get up to.
Nearly 900 species in Kinabalu in the long term.
That's nearly four times as many species as in the whole of Europe.
Just in the rainforests cloaking this one mountain.
There are so many orchids here that some kinds.
Have only ever been seen once before.
You can see how thick this forest is, something like over 100 species of orchids.
That have been found on Mount Kinabalu, are only known.
From one collection.
We've recently been finding species that were discovered 70 to 100 years ago and are now.
Being only collected for the second time.
Of course they have never been photographed before.
Almost nothing is known about many of these orchids.
There are surprises everywhere.
A pure blue orchid.
And this one.
Hosts a colony of ants.
These ants.
Are farmers; they tend tiny bugs.
The bugs suck the orchid's sap and turn it into a sweet liquid.
That the ants love.
The ants are continually moving their miniature herd around.
And the bugs when picked up respond by embracing the ant around its neck.
And holding on.
With ants to guard them, the defenseless bugs can feed without worry.
And that's just one story.
Many more await discovery in these rich forests.
But you don't have to travel to remote rainforests.
To see spectacular orchids.
All across Europe orchids grow.
In impressive displays, even alongside road verges.
They also grow in abundance on the Chalk Hills of Southern England.
And it was these displays that drew Darwin's attention.
He named one of his favorite places.
OrchÃs Bank, a natural laboratory within easy reach of his home.
Down House, in Kent.
In 1859 Darwin published "On the Origin of Species".
Outlining his ideas on how species could change and evolve.
By a process he called natural selection and how this gave rise to the tree of life.
In all its diversity.
But could natural selection really explain the rich variety of animals and plants.
That we see around us.
Many scientists of Darwin's day thought not Darwin knew he needed more detailed studies to strengthen the ideas behind.
His theory.
He was meticulous in his observations and experiments.
And began to look for evidence of natural selection in the plants.
And animals around his home.
He soon became entranced by orchids.
By the ingenious ways that their flowers are adapted.
To make sure that pollen of one plant finds its way to another of the same species.
Soon after starting his studies, he wrote.
In my examination of orchids hardly.
Any fact has struck me so much as.
The endless diversity of structure for gaining the very same end.
Namely, the fertilization of one flower by the pollen of another.
Such cross-pollination.
Maintains genetic variety in the population.
With raw material for the natural selection proposed by Darwin's theory Darwin soon realized that orchid flowers.
Were very different from those of other plants.
Many familiar flowers have identical petals arranged around the sexual organs of the plants.
In orchid flowers.
One petal is often very different.
We now know that this is because orchids have a peculiarity in their genetic code.
Known by botanists as the orchid code.
This allows orchids to evolve individual petals in different ways.
Creating this extraordinary diversity.
In particular, the lower petal, the lip.
Has evolved an almost unbelievable variety.
Of shapes and designs.
The lip has allowed orchids to come up with some very unusual ways.
Of making sure pollination happens.
One of the strangest examples grows here in the Appalachian Mountains in the United States.
These ancient mountains are cloaked in spectacular forests.
Growing beneath the canopy are several kinds of ladies slipper orchids.
The pink ladies slipper.
The yellow ladies slipper.
The lip is swollen into a huge hollow structure bearing some resemblance to a shoe.
The ladies slipper, with a hole in the top.
Bees are drawn to the bright colors of the slipper.
And eventually enter the hole.
Once inside, they can't get out the way they came in.
The sides are too steep and slippery.
But there is a way out, a narrow passage.
At the base of the flower.
It's a tight squeeze, but the bee can sense freedom and keeps struggling.
This escape route forces the bee close to the orchid's pollen.
And as it passes the orchid glues a sticky mass of pollen to its back.
A little disoriented by its adventure the bee soon recovers.
And this is the reason for the diversity of orchid flowers.
As Darwin realized long ago.
It's aimed at one thing: persuading pollinators to carry pollen.
From one plant to another.
The bee is soon drawn to another ladies slipper and once again.
Ends up inside the hollow lip.
This time it knows the way out and as it squeezes through the narrow channel.
The pollen on its back is rubbed off on the female part of the flower.
Success for the orchid.
Many plants don't need help from insects.
Grasses dangle their stamens in the breeze.
And shed huge amounts of pollen on the wind.
It's purely luck if a few grains land on a female flower.
Of the rightt species.
Orchids don't rely on the wind, they depend on.
Insects to move their heavy pollen area from one plant to another.
Early in his studies, Charles Darwin showed that orchids.
Need insects.
In a simple experiment.
He carried out one spring.
Even today, in spring in southern England, sees a few ancient meadows.
Put on a dazzling display of wildflowers.
These sights would have been much commoner in Darwin's day.
The bright yellow of cowslips mingles with the purple.
Of green winged orchids.
And green wing orchids were the subject.
Of Darwin's experiments.
He covered some of the orchids with a glass bell jar.
To exclude any insect visitors and waited.
The orchids in the meadow set seed normally and produced pods.
Full of seeds.
But those covered by the jars failed to develop any seed pods.
Without insects, they hadn't been pollinated.
So orchids need to attract insects but how? Most plants use.
A sugary liquid, nectar, high energy flight fuel.
For insects, and some orchids.
Do the same.
A common twayblade.
With tiny green flowers, but these flowers release so much nectar it runs down the lip in a sticky river.
Which attracts all kinds of insects.
Small wasps.
Are frequent visitors.
The wasp, works its way up the lip feeding on the nectar.
When it gets to the top it bumps into the pollenia.
And the orchid glues some to its head.
Eventually, the wasp will leave to find more nectar, hopefully.
From another twayblade, and in doing so it will cross-pollinate the plant.
But the twayblade's nectar is so.
Easily available it attracts all kinds of insects.
Some, far less useful as pollinators.
Flies.
And beetles.
The swollen-thighed beetle gorges itself on the twayblade's nectar.
And it doesn't seem to notice.
As more and more pollenia are glued to its head.
Meanwhile.
This fly has sucked up so much nectar it must regurgitate it.
So that some of the water in it evaporates and concentrates the nectar.
Then it sucks the liquid back in.
Yet it has avoided picking up any pollenia at all.
The beetle now has so many pollenia stuck to it.
That it is hard for it to feed, but it's strong enough.
To just scrape them off.
These pollenia contain all the pollen from that flower.
If they are destroyed, then that particular flower has no chance of pollinating another.
And, if the insect fails to deliver it to another orchid of the same species.
All the pollen will again be wasted, unlike grass flowers.
Every orchid flower has only one chance to get it right.
Yet, as summer unfolds each and every insect is spoiled for choice when it comes to other sources of nectar.
Countless flowers, all offering rewards.
For insect pollinators.
How can an orchid make it more likely that an insect will visit another orchid of the same species? With its precious load of pollenia.
The fragrant orchid has one way.
Each flower has a long tube projecting out behind it.
And the orchid only produces nectar towards the tip of this spur.
It can be seen clearly through the spur's thin walls.
But it can only be reached by.
Insects with long tongues like butterflies.
A painted lady butterfly takes a little time to find the entrance of the spur.
With its long tongue, so once it's learned the trick.
It has an exclusive supply of nectar open only to long-tounged insects.
It must probe deep to reach the nectar and as it does the orchid glues its pollinias to the butterfly's tongue.
Since it won't have to compete with a lot of other insects for nectar.
It makes sense for the butterfly to find another fragrant orchid and as it feeds.
It now pushes the pollen onto the female parts.
Of the fragrant orchid flower Darwin was beginning to understand the way orchids are adapted to exploit insects.
But one orchid proved a real test.
For his theories.
He was sent a species of orchid from Madagascar - a comet orchid.
Like the fragrant orchid, this species had a spur.
But Darwin measured the spur as over a foot long.
What on earth could pollinate this orchid Darwin made a bold prediction: there must be a moth.
In Madagascar with a tongue to match the orchid.
It wasn't until after Darwin's death.
That the hawk moth, with the predicted foot-long tongue was found and then just a few ago, scientists saw the moth in action.
Entomologists filled the fleece.
Travelled to the forests of Madagascar to stake out a comet orchid at night high in the canopy with infrared cameras.
Nothing to do now but wait.
There it is.
It's hovering in front of the orchid.
The tongue out, look! Awesome! Final Proof, 143 years after Darwin's prediction Darwin would doubtless have felt the same.
Unbelievable.
From an orchid's point of view a close partnership with one or just a few species.
Produces the most reliable pollinators.
And in tropical America some species found an ingenious way of doing just that.
Orchid bees.
These bees are all male.
They flock to certain orchid species in large numbers.
But they are not after nectar.
Instead, this orchid produces an oil which the bees.
Scrape up with their front legs.
Then, in flight, they transfer this to large pouches on their back legs.
Here it's converted into a chemical that female orchid bees find irresistible.
Only orchid bees have any use for the orchid's oil.
So, like the comet orchid and the hawk moth in Madagascar.
These tropical American orchids have formed.
An exclusive relationship and turned orchid bees.
In a reliable delivery service for their precious pollenia.
But some orchids produce no reward, no nectar.
No oils, nothing.
The green-winged orchid shown by Darwin to depend on insects.
Is one such miserly flower.
Yet Darwin flatly refused to believe that some orchids produced no nectar at all.
Why would an insect visit a flower for no reward? He thought that insects were too smart to waste their time on flowers with no nectar.
So he made careful dissections of green wing orchids looking for nectar - he found none.
But was convinced that it must just be hidden in some way.
But this time Darwin was wrong.
We know that around one third of all orchid species produce no reward at all.
So why do lots of insects fall for what Darwin called so gigantic an impostor? To an insect the green-winged orchid looks like the kind of flower that should produce nectar.
And is surrounded by many other species that are rich in nectar so it's worth investigating and as the bee probes in vain for the nectar it picks up the orchid's pollenia, but soon leaves.
Still hungry, to look for a more rewarding plant.
If this is devious.
Other orchids are downright dishonest.
Narrow-leafed helleborine growing not far from Darwin's home.
They share this forest with a close relative.
The white helleborine Darwin was familiar with both of these plants.
And examined them closely.
He found that the white helleborine has yellow ridges on the lip.
And observed that these were often nibbled by insects.
Though he never saw the culprits.
The narrow leafed helleborine has even bigger yellow patches Darwin thought that they were some kind of food for visiting insects.
An alternative to nectar, but it has recently been suggested that.
That these patches mimic the loose pollen of other plants.
Many insects eat pollen, although they don't find the sticky pollenia of orchids.
Very appetizing, so this is a farce.
That the orchid uses fake pollen to attract insects by deceit.
Many of the 25,000 kinds of orchids are dishonest.
And some use not the promise of food, but the promise of sex.
Bee orchids.
There are many kinds of bee orchids and the lips of their flowers have come to.
Resemble different insects.
To attract pollinators they need to convince male bees.
That the lip really is a female bee, but surely male bees would never be fooled by such a crude mimic.
To find out how the orchid succeeds.
We need to visit a colony of these bees.
In early spring, the air is buzzing with male bees.
They spent the winter underground, in the nests where they grew as larvae.
Males emerge before females.
And now they are hunting for the first females Female bees release.
A particular scent, a male can even smell a female still hidden underground.
And in his eagerness tries to dig her out.
Eventually, The first females emerge.
Almost immediately she's pounced on by males.
Often many of them.
The males have a good reason for this frenzy.
A female will only mate once, so it's vital.
To be first there.
Males have to be quick if they want to mate.
No time to be discerning as long as it smells right.
He doesn't hesitate and that's what the orchid depends on.
A bee orchid flower releases a similar chemical mix to a female bee.
It's a close enough match that eager males pounce on the flower and try to mate with it.
As they do so they pick up.
The orchid's pollen.
It's a devious trick, but a risky one.
As Darwin long ago suspected insects are smart enough to know when they're being duped.
And only a very few of these bees will fall for the same trick twice.
But if being deceitful.
Is such a risky pollination strategy, why have so many orchids given up producing only a reward, like nectar Darwin simply couldn't believe that the green-winged orchid could be cross-pollinated without producing nectar to attract pollinators and as only recently discovered what this orchid is up to.
A devious trick to make cross-pollination even more likely.
The orchid's plan becomes obvious if artificial nectar is added to the flowers.
In this experiment scientists dosed some plants with nectar and left others free.
They then recorded the behavior.
Of visiting insects.
Bumblebees are the main pollinators of this orchid, and the scientists weren't surprised that the bees spent far longer on the flowers with artificial nectar drinking their fill.
On the normal plants they spent only a fifth of the time.
A quick check of different flowers to see if there's any nectar.
And then, disappointed, they move on.
But the scientists also watched what happened to the pollen picked up by those bees.
Spending longer on plants with nectar greatly increased the chance that the bee would just move pollen between flowers on the same plant - self-pollination - not what the plant wants.
Though, by not producing nectar.
The orchid makes it more likely that the bee will leave and carry the pollen to a different plant.
The plant that so puzzled Darwin.
Now seems to fit his ideas perfectly, a clever adaptation.
To encourage cross-pollination Darwin missed this story.
But he did discover some adaptations just as ingenious.
In his own studies.
In early spring the woodlands near his home were carpeted with wild flowers.
Amongst these there's a tall and stately orchid.
The early-purple orchid.
This was the first orchid that Darwin studied.
He found that even the pollen masses themselves have a very clever way to ensure cross-pollination.
He extracted the pollinias using a sharpened pencil.
To mimic the probing tongue of an insect.
The polynia stuck to the pencil.
Just as they would to an insect.
At first, nothing happened, then after about half a minute he saw something amazing.
The stalks holding the pollen masses began to bend forward Darwin realized what this meant.
Each pollen mass was now lined up to meet the female part of the flower.
And the orchid delays the bending long enough for the insect to finish feeding on that plant.
By the time the pollinia are aligned to hit the female part of the flower the insect will have left the first plant and have carried the pollen to another.
When an orchid is finally pollinated.
It produces thousands of seeds.
There are so many, the plant can't afford to make big seeds.
Instead orchids seeds are like dust, they blow on the wind.
And because they are so small they can't contain any food supplies for developing seedlings.
To germinate and grow orchids must use yet more deception.
When we see a forest, we see a collection of trees and other plants.
But that is only one way of viewing it.
We need to look at the forest in a different way the way an orchid sees it.
At the microscopic level, the forest floor is a mass of fine filaments.
The threads of fungi.
Spreading right across the forest.
We normally think of fungi as the mushrooms that spring up from the forest floor each autumn.
But these are just the structures that produce the spores, the reproductive organs of the fungus.
The bulk of the fungus is underground; this is decomposing and digesting the material that falls onto the forest floor.
The fungal threads connect with the roots of the trees, the fungus supplies the tree with certain nutrients.
And in return the tree passes the fungus sugars.
That are made by photosynthesis in its leaves.
So the forest is like one huge.
Superorganism and the orchid seed is a parasite.
Fungal threads penetrate the seed to try to decompose it.
But the seed contains fungicides that stop the threads from overwhelming it.
Now the orchid seed can steal nutrients from the fungus.
To fuel its own growth.
Most orchids maintain a relationship with fungi.
Even after they grow their own leaves and can make food for themselves.
But some take this to an extreme.
The bird's nest orchid.
It has no leaves at all.
It simply produces its pale coloured flower spike.
Each summer.
It depends for all of its food on the fungal threads running through the forest floor.
In turn, the fungus gets much of its food from the trees, so the orchid is connected to the trees.
And makes use of their leaves held high in the sunlight.
Each kind of orchid depends on very specific fungi.
To germinate and grow, which makes orchids.
Very difficult to grow in cultivation.
World-wide many orchids are threatened with extinction, so growing them successfully to put back in the wild is critical.
The Everglades in southern Florida a vast area of swampy grassland.
Running through this river.
Of grass are long strips of forest.
Strands.
Dense, often impenetrable and infested with mosquitoes.
This is Fakahatchee strand, it may look uninviting.
But it hides a real treasure.
And this is it.
A ghost orchid.
For most of the year, this is all we get, a few roots.
It has no leaves, but the roots are green and photosynthesize.
To provide the orchid with food.
And then the summer brings rain to replenish the swamps it transforms.
In the flickering sunlight of the dark forest it opens an exquisite flower, perhaps the most sought after of all orchids.
There are only around 2,000 ghost orchids in the whole of South Florida, all of these sites are closely-kept secrets.
They have to be.
Remote cameras hidden in the swamps catch poachers emerging with armfuls of rare orchids.
There is still a demand world-wide for orchids stolen from the wild.
Help for such threatened orchids comes from an unlikely source.
Writhlington School in Somerset in the UK.
It looks like any other school.
But in its grounds are state-of-the-art greenhouses.
Part of Writhlington's International Orchid Project.
In the greenhouses, students grow.
Over a thousand different kinds of orchids from all over the world.
They're using all the same techniques for cultivation as used by the biggest botanical gardens.
And they have spectacular results.
The school has its own propagation lab, where seeds can be germinated and plants grown on.
The school produces thousands of plants each year.
And these plants allow the school to help orchids world-wide.
The orchids are carefully tended in the greenhouses.
And then sold.
Part of the money raised goes into funding.
Trips to some of the most exotic places a student could imagine.
In the past we have had several in Central America.
Central and South America: Brazil, Belize, Guatemala.
There are plans to go to Rwanda there is a Canada trip and a second trip.
In many of these places.
The students help local botanists and conservationists set up labs to cultivate their own orchid species.
The Laos expedition was the last one to go on, where we helped Eddie and Suk, our contacts out there, set up a lab in Laos, which is the first lab in southern Laos to grow orchids from seed.
Because the big problem out there is wild collection.
Because people steal them.
Cultivating orchids in all these countries.
To supply collectors is reducing threats to wild populations.
And in the process the students at Writhlington get to know perhaps the most amazing plant family of all.
People enjoy being part of something that is.
Truly special is probably the best.
Plant family to be involved in, I think.
Yes, I love it.
In their passion for the world's largest family of plants.
They are following in the footsteps of Charles Darwin.
A new generation inspired by these remarkable plants.
And there is still plenty left for them to discover.
One of Darwin's favorite orchid sites was Downbank near his home.
Perhaps he had this place in mind.
When he wrote the final sentences of the Origin of Species.
It is interesting to contemplate.
An entangled bank, clothed with many plants of many kinds.
With birds singing on the bushes with various insects flitting about.
There was, he wrote, grandeur in this view of life.
But the very last sentence in The Origin seems particularly appropriate.
To orchids.
Endless forms, most beautiful.
And most wonderful, have been and are being evolved.
Endless forms that have helped orchids to become.
The most successful family of plants on the planet