Original subtitles

I'm exploring the fascinating world of plants,

from the most bizarre to the most beautiful.

With new techniques and in 3D,

we can unravel their deepest secrets.

We can move from our time scale to theirs.

We can see how they struggle with one another,

how they get help from some animals

but have the battle with others,

and survive against the odds.

And we can watch all these dramas taking place

in a way that is impossible in the wild

in one unique institution.

The Royal Botanic Gardens at Kew.

In this living laboratory,

we can discover plants' most extreme adaptations for survival

and we can glimpse Kew's tiny weapons

in the battle to protect the future of all plants...

seeds.

Kingdom of Plants with David Attenborough

Ever since plants first moved out of water and colonized the land,

they've advanced into drier and drier places

and evolved specially set-up adaptations

in order that they can do so.

Today, deserts cover about a third of the land's surface of the earth

and they are spreading rapidly.

But some plants have developed some truly extraordinary strategies

to enable them to survive in the driest of places.

Survival

In deserts where water is scarce,

one major strategy is to remain passive during the day

when temperatures soar

and only become active in the cool of the night.

This desert in Kew's Princess of Wales Conservatory

contains plants from every regions all around the world.

And in mid-summer,

one plant here does something truly astonishing.

Don't be deceived by the shrivel untidy appearance of this cactus.

This, in fact, one of the most remarkable members of the cactus family,

is called Hylocereus...

"the Queen of the Night".

It lives in Mexico

where, during the summer midday,

the temperatures can reach a crippling 50 degrees centigrade.

So during the day, it doesn't do much.

But once a year,

for one night only,

it becomes a thing of astounding beauty.

The flowers usually open on a night of the full moon.

And as they do so, they give off a smell

which attracts night flying animals, large and small.

And as they get nearer,

they can see the great white flowers,

bright in the light of full moon.

And they go to them to sip the nectar

and, in doing so, pollinate the cactus.

It might seem strange, even risky

for the plant to restrict its flowering to just one night of the year.

But this strategy works for Hylocereus.

Its flowers are the biggest and brightest around

and they offer its pollinators a nectar banazar...

bats.

With the aid of technology, we can imagine them,

thousands of miles from their natural habitat,

here in Kew.

Bats pollinate all kinds of cacti.

In spring time in Southern American deserts,

there is always a cactus of one kind or another in bloom.

A multitude of species compete for the attentions of nocturnal pollinators

using bright pedals and powerful scent.

The sweetest perfumes attract insects.

But flowers that are pollinated by bats

are rather more pungent.

They give off the stench of rotting fruit.

To nectar feeding bats,

that smell is irresistible.

They fly from cactus to cactus,

sipping out the nectar.

Each bat can consume more one and a half times its bodyweight of nectar.

In a single night.

Very tall columnar species,

produce flowers right to the very top of their stems

where they are easily smelt and seen,

and easily reached.

Some provide additional facilities.

Espostoa guentheri from Bolivia

sprouts a landing strip beneath its flowers,

a pat of fur on which the bats can alight

without damaging their wings on the spines.

But in Mexico, bats and cacti

have a even more extraordinary relationship.

Each year, bats migrate across 1,000 miles of desert

from central Mexico to Arizona.

Pregnant females, 100,000 of them,

are on their way to special maternity caves in the north

where they will give birth to their young.

The bats get all the nectar they need to sustain their journey

and in return, they pollinate the cacti.

This annual bat migration coincide exactly

with the blooming of the night flowering cacti,

so the bats can fly along a nectar corridor,

and so can cross a patch of desert

that, otherwise and at other times,

would be impossible for them.

By the time the bats return with their pups,

the cacti are able once again to provide the bats with food,

this time, their fruits.

The bats carry with them in their stomach the fruit

and the seed it contains.

And in due course,

they deposit those seeds with a nice little package of fertilizer

farther down the corridor.

So the corridors are self perpetuating.

The bats, in effect, are cactus farmers.

Perhaps the most extraordinary thing

about these night blooming cacti

is that, just a few hours after the flowers burst open,

they begin to close.

By the time the sun appears,

they have already wilted and died.

This is all part of their survival strategy.

The closed pedals form a protective shield

around the newly pollinated seeds

locking vital moisture inside.

The light of a new day

reveals the bizarre nature of dry zone plants.

These are surely some of the oddest looking species there are.

And their strange shapes

are a direct response to the harsh conditions.

These plants will stay in the baking sun to collect the light they need,

but they must also retain their moisture.

Many do that by turning either their green stems

or their waxy leaves into reservoirs.

This extraordinary cactus from Mexico

is covered in thick white hair.

It's called "the old man".

This fur not only provides shade,

but restricts the circulation of the air around the surface of the stem

and that reduces water loss.

In even hotter and drier climates,

some plants avoid the sun all together.

This is Fenestraria...

the window plant.

It grows in the Kalahari Desert

with most of its body buried beneath the soil.

Only the blunt flat tips of its leaves are exposed.

Each contains tiny lenses

which transmit the sunlight down through the vertical leaf

on to its green photosynthesizing cells.

Some desert plants that live in exceptionally hot dry conditions

take even more drastic measures.

Leaves are very thin and have a large surface area

so they lose a lot of moisture in heat.

And many desert plants have done without them all together.

Instead the valuable green pigment develops in the stems.

And desert stems are often very thick and swollen

and that enables a plant to store water in them.

Not only that,

but some desert plants have pleats in these stems

so that when there is sudden rainstorm,

those ridges can suck up all the moisture while it is there

and expand in order to hold it.

The stems of some of these species swell to such a degree

that they become almost spherical.

A sphere has the minimum surface area for any given volume

and that enables the plant to hold as much water as possible.

This one is Copiapoa from northern Chile

where it never rains at all.

But, in fact, it doesn't need it.

Under a microscope, you can see why.

There are thousands of tiny jagged structures

on which the morning dew condenses

so that the plant can collect it.

But the ultimate is this plant.

It's hidden between these light colored pebbles...

Blossfeldia from Argentina.

This is the only flowering plant

that can withstand total desiccation

for months on end.

And then with a shower of rain or a little bit of water,

it comes to life and produces a tiny little flower.

This ability to wait for the right conditions

is the trump card that enables many plants

to survive in the dry zone.

In many deserts,

plants must endure months, sometimes, years, of drought.

They do it by slowing down their metabolism

and going into a state of virtual dormancy.

But when rains finally arrive,

plants like these suddenly come to life.

Their dried out tissues absorb water like sponges.

And once expanded,

they use the moisture to grow.

This primitive wakeless plant from the Chihuahuan Desert in Mexico

is a spikemoss, Selaginella.

It's also called "the resurrection plants"

because its ability to seemingly come back from the dead.

Rain starts a complex biochemical change in its cells

that enables it to ramp up its metabolism

and grow very quickly while it can.

But the most spectacular consequence of rain in the desert

is an explosion of color.

Desert flowers are as colorful as any of the world.

They have to attract pollinators quickly

before the deserts dry out once again.

But moisture in the soil could evaporate almost as quickly as it arrives

and after a brief bloom, they die.

Desert plants could only grow when the conditions are right

and that maybe only for a few short periods in the year.

So many desert plants

take a long time to reach full size.

That agave there, for example, is over 40 years old.

But during that time,

it has manufactured food and gathered water

and stored them in its great fat leaves,

but it's not yet adult.

This one is.

This agave has started to withdraw that water and food from it leaves.

So now, they are beginning to crumple and wilt.

And it uses that food

to fuel the growth of this huge mast-like stem

that grows from its center and will carry the flowers.

And it reaches its full height at extraordinary speed.

It can grow by a quarter of a meter everyday.

It reaches such a height

that here in Kew's glass house,

panes have to be removed from the root to let it through.

This infrequently flowering

has given this species of agave a nick name...

"the century plant".

So why does the agave produce this huge tall mast?

Well, some plants are pollinated by insects

and you attract insects with smell.

But this plant is pollinated by birds...

humming birds.

And birds have little or no sense of smell.

To attract them, you have to exploit their very sharp sight.

You have to produce flowers that are very bright

and put them right at the top of a prominent tall mast.

Growing at such a rate demands considerable effort.

For the agave, it's terminal.

The act of producing that mast

is the last act in this plant's life.

Having done it and been pollinated, it dies.

Thanks to their extraordinary survival strategies,

desert plants are able to thrive in places

where others would die.

But that makes them the focus of much unwanted attention.

As a downside to success for a desert plant,

the more water it stores,

the more tempting it is for a thirsty animal to try and steal it.

So desert plants have to have good defenses.

The techniques they use can tell us something

about the herbivores that try to feed on them.

This Echinopsis from Argentina

develops long strong spines

as a defense against large grazing animals...

llamas.

But such defenses also provide hiding places

where an insect or a spider can keep out of harm's way.

There are other ways in which a plant can protect itself.

You can disguise yourself,

so you become virtually invisible

as these stone plants have done.

These are not pebbles as you might think.

They are living plants.

These are lithrobs from the deserts of Africa

and their markings closely match their surroundings.

What's more, they are varying color

according to the rocks on which they grow.

That's growing on pale rocks,

and those on reddish rocks.

Or you can load the water you contain

with a particularly strong chemical

which animals might find distasteful.

This is the Peyote plant from Mexico.

And its sap not only puts off animals,

but has the property of suppressing pain,

so the local people use it for that purpose

and also in their religious rituals

for it's also hallucinogenic.

In colder regions,

pine trees also have to conserve water

for during the winter

water in the soil is frozen and so beyond their reach.

Little evaporate their leaves

because they have been reduced to stiff tough needles.

Like cacti,

they also produce distasteful chemicals.

The distinctive smell that you sense when you walk among pine trees

come from volatile oils

that the trees produce in their leaves.

It's a form of defense.

Most insects can't bear it,

but one can...

the pine aphid.

When that attacks, however,

the pine trees have a second line of defense.

They produce that volatile oil from the cuts made by the insects

in even greater quantity

and that crucially changes the nature of the smells around the trees.

Aphids infestation triggers a complex chain reaction from the pines.

Each time an aphid bites,

the pine releases oily vapor from the wound

which fills the surrounding air.

This triggers the release of further volatiles from other branches,

even other trees.

The effect multiplies

until eventually whole forests become coat in pine scent.

This scent cloud attracts predatory ladybirds.

They are as sensitive to it

as sharks are to blood.

This is the eyed ladybird

and it preys on pine aphids.

It locates an infestation

by following the trail of volatiles.

And once there,

it makes short work of the prey.

It's a mutually beneficial arrangement.

The ladybird gets an easy meal

and the pine tree gets rid of a pest.

Some dry zone plants use oils

to defend themselves from other dangers,

not from insects but other plants.

This is a eucalyptus,

famous for the oil in its leaves.

It produces that oil in such quantity

that, under certain conditions,

it can form a blue haze above the tree.

In fact, the Blue Mountains of New South Wales in Australia

get their name from the haze

that hangs over eucalyptus forests sometimes.

When the leaves fall to the ground and rot,

the oil leaches out into the soil.

And then, reinforced by more oil secreted by the roots,

it acts as an inhibitor

that prevents other seeds of other plants from growing around its base,

so reducing competition for the eucalyptus.

Another species uses oils in a different way

and a more dramatic one.

If the temperature raises to 32 degrees centigrade,

those substances in the leaves of this Cistus plant from the Mediterranean

can spontaneously burst into flame.

The flames reduce the Cistus to a cinder

and the plant itself will never recover.

But this is not a disastrous accident.

The Cistus has evolved to burn.

Such extraordinary sacrifice ensures a different kind of survival...

survival of its offspring.

The flames will also destroy all other plants

from the surrounding area

and this gives the Cistus

the chance to extend its territory.

From the ashes,

a new generation of Cistus quickly rises.

Cistus seeds escape damage

because they are enclosed in flame-resistant capsules.

Further more, the spurt stimulates their germination.

It has taken millions of years

for such complex adaptations as this to evolve.

But today,

plants of the dry zone and beyond

face a new threat.

From rainforests to mountain ranges,

the evidence is that plants across the world

are disappearing in variety and number

faster than at any other time in the earth history.

Human beings are taking over more and more of the world's wild places,

but human intervention can also be the key to their future survival.

Kew is at the forefront of the effort.

Its unique facilities enable scientists here

to both measure the loss of species

and work out how to prevent extinctions before it's too late.

And a crucial resource in that battle

is held in this building...

the Herbarium.

Its collection of preserved and dried specimens

contains samples of 90 percent of all known plant specimens on earth.

Here, almost unbelievably,

there are records of every single specimen ever sent to Kew.

It was founded in 1853.

Now, staff process about 50,000 specimens

that are sent every year from all over the world.

It contains about eight million specimens.

It's the biggest repository of botanical data in the world

and Kew's major weapon in the battle

to save the plants of the planet.

This vast databank

plays a vital part in monitoring the global health of plants.

It's run by curator David Mabberley.

This herbarium, eight million specimens,

is actually a record of the vegetation of the earth through time.

There are something which had gone completely extinct

and so all that is known of them is just some herbaria specimens.

For example, this is a relation of the olive,

which was known only from one island off the coast of California.

And it hasn't been seen since 1873.

Really?

Even then, there were only three and that's all that we've got left now.

Goodness!

These specimens, though, are referred to, aren't they? For identification.

Yes, these are the standards.

And the ones which are in these red folders like this are actually the ones

upon which the original description of a plant was made,

the so-called type specimen.

And therefore this is the kind of gold standard.

If anybody really wants to know what is meant by a particular plant name,

they must refer to the type specimen.

The path to saving endangered species often begins here.

For example, back in 1874,

this specimen was sent back

from the Island of Rodrigues in the Indian Ocean

of a tree they called the Cafe Marron...

a kind of coffee.

It was preserved here,

given a Latin name and put in the Herbarium.

And then, about 50 years later,

people on Rodrigues realized that Cafe Marron had disappeared.

Then, in 1979, someone found a plant.

Was it, was it not Cafe Marron?

A specimen was sent here, compared with this specimen

and indeed it proved with the case.

So, for that single plant,

a cutting was taken and sent here to Kew for propagation.

From that single cutting,

horticulturists grew a handful of clone specimens.

But although they flowered frequently,

they never produced viable seed.

Without the ability to reproduce,

the Cafe Marron was still doomed.

So the plant earned the nickname

"the living dead".

The daunting challenge of rescuing it

was taken up by endangered plant specialist...

Carlos Magdalena.

After several months of experimentation with heat and light,

he finally managed to induce the plant to produce seed.

But when they germinated,

the young plants had leaves so unlike the Cafe Marron he knew,

he thought he must have made a mistake.

That's quite different from Cafe Marron.

It's rather different, isn't it?

Different color, different leaf shape.

So, were you surprised?

Well, I was surprised in the way that I've never seen them before.

This strange plant looks nothing like the herbaria sample.

At first, nobody could be sure that was even the same species.

But as it grew,

it changed

and eventually, it morphed

into a recognizable adult plant.

But what is the reason for this dramatic change

as the Cafe Marron matures?

The answer is camouflage.

This is the most famous inhabitant

of the Island of Rodrigues...

a giant tortoise.

It loves bananas.

Go on.

But they also likes green leaves

and that's their main food.

So any plant growing close to the ground

has very little chance of survival

while creatures like this are going around eating them.

And that's the clue to the mystery of the Cafe Marron.

When it's small, it produces leaves

that are very thin and not even green.

And the tortoise whose eyesight is not very good

doesn't even see it.

So he takes very little notice of leaves like these

and the Cafe Marron can grow.

As it grows,

it becomes a bit bigger

and still

its leaves are thin and dark

and rather inconspicuous.

And it's not until

it's really quite tall

does the Cafe Marron plant produce its proper green leaves

and its flowers.

But by that time,

it's well beyond the reach of a giant tortoise.

So that is the solution

to the Cafe Marron mystery

that the plant produces two different leaves

as a defense of being eaten.

The Cafe Marron's survival

is tribute to the skills developed here in Kew.

But it is just one species.

The ultimate aim is to safeguard all remaining plant species.

And the maybe-way of doing that

by using these extraordinary structures...

seeds.

A 3D microscope magnifies them up to 200 times

and reveals how extraordinary complex

the surface of a seed can be.

No two species are the same.

These images have been given artificial colors,

but many of their shapes are beyond explanation.

Some structures, however, have a clear function.

They help the seed to achieve one of its main purposes...

to travel.

Many seeds rely on animal couriers.

The American Stickseed

attaches itself to the fur or skin of passing animals

with hooks or barb spikes.

The amazing sticking structures of such hitchhikers

inspired the invention of Velcro.

Some seeds carry a little package of nutritious fat

which persuades an ant to take it back to its underground nest

where the seed having surrendered its fatty reward to the ants

can germinate in safety.

The seeds of orchids are miniscule

and produced in their millions.

They blow away like dust.

In contrast, this much bigger seed has a large flat membrane

which serves as a wing

so that it can float great distances on the wind.

Other wind disperse seeds like the yellow paintbrush

have a honey cone texture.

Such complex sculpturing

enables seeds to catch the slightest wind current

and ride thermos

traveling long distances from their mother plants.

But these images also reveal

the incredible toughness of the seed's outer capsule.

This strength's maybe the key

to the survival of all plants

for seeds can survive all kinds of hardship.

This plant is called the pincushion.

And grows in South Africa.

And this individual specimen is something of a miracle.

In 1803,

a British man of war captured a Dutch merchantman

coming back from the Cape of Good Hope.

And on board, in the cargo, they found a pack of seeds.

When they got back to Britain,

the seeds went to the trial of London for quite a long time.

But eventually, they found their way here to Kew.

And one of them,

germinated and produced this plant

after 200 years,

just shows how long seeds can survive even without help.

This ability to endure

has inspired Kew's latest ground-breaking project.

Its ultimate goal is to ensure the survival

of every remaining species of plant on earth.

The work takes place deep underground

in a labyrinth of sealed vaults

that are encased in steel and concrete.

It's called the Kew Millennium Seed Bank.

Its contents are so valuable

that it was specifically designed to withstand the impact

of a bomb or an air crash.

Inside these vaults, there are seeds

gathered from plants all over the world.

In fact, as much as 10 percent of the world's known species

are represented in there.

The heart of the Seed Bank Project

is this gigantic freezer

full of seeds in sealed jars.

The conditions inside are perfect for long term storage.

But the job is aided by the very nature of seeds.

The seed is the stage in which a plant can remain dormant

waiting until conditions for germination are right.

Inside the seed, there is a store of food.

Outside, there's a tough protective shell

to guard against predation or damage.

In fact, the seed is a kind of time capsule

that can live for sometimes a decade,

sometimes even centuries.

The aim of the Seed Bank

is to prolong that period as long as possible.

To do that,

they clean the seeds,

dry them,

put them in jars like this,

and then keep them here at minus 20 degrees centigrade.

How long they will survive under these conditions?

Nobody knows,

but it's certainly going to be for a very long time.

New samples arrive for the Seed Bank everyday.

They are first identified and studied in microscopic detail

by chief morphologist Dr. Wolfgang Stuppy.

The latest report from Israeli paints that

date palm seeds have been found in King Herod the Great's palace in Masada

and they germinated after 2,000 years.

So that is possible and this is

the principle that naming "Seed Bank" is built upon.

That seeds can survive for millennium if necessary.

The longevity of most kinds of seeds is unknown,

so they must be regularly checked.

Samples of seeds are periodically removed from the vaults and germinated

If most grow,

the whole batch will be left in the vaults for another decade.

And sometimes a sample fails,

like these anemone seeds,

which, although germinating in sterilized conditions,

become chocked with fungus.

When this happens,

the scientists must find out why

and how to prevent it from happening again.

The Seed Bank Project is still in its infancy

but the evidence is that there is no time to lose.

There are already seeds stored here from plants

that are now extinct in the wild.

The problem is, well, many people don't understand,

is that if a species got extinct,

it means it's gone for us forever.

There were five mass extinctions in the earth history.

After every mass extinction,

it took between 4 and 20 million years

for biodiversity to bounce back to pre-extinction levels.

Now, clearly we cannot wait four million years

for life to bounce back.

So if we don't keep seeds here

and this plant species got extinct,

it will be lost to mankind forever.

Thankfully, there is a great momentum

behind the Seed Bank Project.

Over the next a few decades,

these shelves will be filled to capacity.

There's enough space here to hold seed

from every single species of plants on this planet.

But this place is not just an insurance policy

against the ultimate apocalypse.

This is of huge value right now.

For whatever we discover

that a plant is teetering on the brink of extinction,

we can now boost its numbers with seeds from here

and so ensure that no plant species on earth need go extinct.

There are an estimated

400,000 different species of plant on the planet.

We can't possibly understand the lives of each and every one of them.

But here at the Royal Botanic Gardens in Kew,

one of the birth places of scientific botany,

we began to glimpse their extraordinary world.

Kew is still in the forefront of botanical research

helping to ensure that we not only understand plants,

but protect them in all their astonishing variety.

And here, we can see

how plants in all habitats and environments

are intricately connected with animals

and with fungi.

Not only do plants give the world much of its beauty,

they are indeed the very basis

of all life on earth.