Plants cover much of the land surface of our planet.
But there is another extraordinary green world
that is often hidden from us.
It's one where plants have overcome huge challenges
in order to survive.
The world of fresh water.
At first sight, a lake like this would seem to have everything
that life needs in order to thrive.
Clear, oxygen-rich water,
plenty of dissolved nutrients and minerals
and lots of sunlight.
But, in fact, life in fresh water
presents plants with huge problems.
To succeed, plants have had to abandon many of the adaptations
that served them so well on land
and evolve something quite new and, doing that,
they have created some of the most beautiful and bizarre
and important habitats on Earth.
There are few places where it's more difficult to make
a permanent home than a freshwater torrent like this one.
Violent currents drip across the riverbed,
scouring it clean...
..whipping land plants from their margins
and drowning them.
How could any plant survive in a place like this?
Yet, even here, some do manage to,
quite literally, hold on.
They can grasp the bare rock with remarkable strength.
This ability allows plants to thrive
in these otherwise hostile environments.
This is the Cano Cristales river in Colombia.
These plants are red Macarenia,
sometimes called the Orchid of the Falls.
They cling to the riverbed, not with their roots,
but with their stems, glued to the rock surface by one
of the most powerful adhesives in nature.
The rock itself will break
before these anchors lose their grip.
These feathery filaments are their modified leaves,
and they do what roots normally do -
gather the minerals and nutrients they need
that are dissolved in the water.
With such spectacular colours, it's hardly surprising
that the Cano Cristales is sometimes called
the most beautiful river on Earth.
But being rooted to the spot is not always the best strategy
for living in a water world.
This is a water lettuce,
and it has some remarkable adaptations.
Its roots hang free,
so it's not anchored to the ground,
and its leaves are thick and spongy
and covered in fine hairs.
So the plant itself is more or less unsinkable.
This combination of characteristics enable the water lettuce
to do something that almost no land plant can do.
It can travel.
It is an ability that becomes invaluable when,
during the wet season, flooded rivers become great highways,
as they do here in South America.
This is the largest inland water world on Earth.
The Pantanal.
For a few months every year, it provides water plants
with ideal conditions,
but, all too soon, it becomes a battleground.
Plants are racing to claim their space on the surface.
The water lettuce rapidly expands its network of hanging roots
so that it starts absorbing nutrients
before other competitors arrive.
Water hyacinth appears.
Its leaves are carried on stalks filled with air
that also make it virtually unsinkable.
The race for space intensifies.
A new competitor arrives, Ludwigia.
It spreads by developing a chain of tiny rafts.
And jostles for space with the densely packed leaves
of mosaic plants.
All are racing to claim as much sunlight as possible.
They flower quickly before the floodwaters recede.
And these surface dwellers also have competitors.
Including one that has been waiting in the depths
and is now stirring.
It's a monster.
It's well armed.
It clears space for itself
by wielding one of its buds.
Like a club.
And now it dominates the surface.
This is a leaf of the giant water lily.
It expands by over 20 centimetres a day
and eventually measures
more than two metres across.
Its immense leaves are supported by a network of air-filled struts
and protected by spines two centimetres long.
The leaves float high in the water and their surfaces are dotted
with tiny holes, drains, that help them ensure that rainwater
doesn't accumulate and sink them.
Nutrients from the fertile mud below are carried up by tubes
in its stem to fuel the leaf's expansion.
Over the next few months, the lily will produce
some 40 or so of these gigantic leaves.
And as each one reaches the surface and expands, more and more light
is taken from those plants that are trying to grow beneath.
Competitors are pushed aside.
Some are crushed,
or skewered.
Eventually, its immense leaves press their margins
against one another,
totally cutting off the light from the plants beneath them.
The battle is over.
And victory is total.
The frozen water world of Lake Akan in northern Japan.
Home to one of the strangest and most primitive of plants.
It's an alga, like those that appear so mysteriously in our ponds.
But this one is truly extraordinary.
Each spring, the melting ice releases soft, velvety balls
of interwoven threads called Marimos.
This one is small.
No bigger than a walnut.
But there are lots of them here.
They attract the attention of visiting whooper swans.
But there is one way for the Marimo to escape from the danger,
and it depends on a change in the weather.
Fortunately, in the spring, winds sweep across the lake...
..creating currents that carry some of the Marimos beyond the reach
of hungry swans.
It's the start of a remarkable journey.
They are gently carried back and forth by the currents
so that the Marimos become more and more spherical.
And, slowly, they travel into deeper water.
Here, there are great numbers of them, certainly many millions.
Some are the size of basketballs.
They're safe from swans,
and the water is still shallow enough
for some sunlight to reach them.
It seems a perfect home.
And so it is...
..almost.
The snag is that these waters also carry a fine sediment
that can clog the Marimo's surface,
cutting off the all-important light.
But the Marimos are not entirely immobile.
They dance.
The winds blowing over the lake's surface create currents
beneath that are sufficiently strong to move the Marimos.
They rub against each other.
And in just a couple of hours of gentle movement,
they're all clean once more.
As they spin, every part of their surface
gets enough time in the sunlight to keep growing.
This is the heart of the Amazon.
There are water worlds here that are so remote that, even today,
few people have ever seen them.
This barely explored tributary is the Rio Claro.
And here, when conditions are just right, it's possible
to witness a rare and remarkable spectacle.
The river is so crystal clear that its bed is bathed in sunlight.
A magical landscape of miniature mountains and valleys.
It's carpeted by pipewort, fanwort
and star grasses.
As the sun climbs in the sky...
..bubbles of gas appear.
Evidence of photosynthesis.
Deep inside the plant cells,
tiny structures called chloroplasts
move towards the light.
They absorb carbon dioxide and use the sun's power
to synthesise the sugars that the plant needs to grow.
And as a by-product, they release oxygen.
The gas that we and all other animals must have
in order to breathe.
Now, in late afternoon, bubbles of oxygen make the river water
fizz like champagne.
The plants can become so buoyant with gas
that they rise to the surface,
even carrying the bedrock with them.
Only in this remote water world
can this spectacular natural wonder be seen.
Eastern Venezuela.
Here, rectangular table mountains known as tepuis
stand above the tropical forest.
There are more than 50 such isolated mountain plateaus here,
each home to a unique community of plants.
Downpours are so torrential that no soil can accumulate
on their broad, rocky summits,
and some plants living up here have to find their nutrients
from another source.
These are Bromeliads.
Their leaves are shaped like a funnel and collect rainwater,
which accumulates in the centre.
This small pond is colonised by all kinds of tiny animals.
And it is their bodies, when they die, that provide
some of the nutrients the Bromeliads need.
This makes a good partnership in which both parties can thrive.
But...
..it can be exploited
by a plant predator.
This probing stem belongs to a plant called a bladderwort.
It, too, is in need of nutrients.
And a well-stocked Bromeliad pool is just the place to find them.
This one is full of aquatic animals.
The bladderwort begins to change...
..into a hunter.
It develops bladders
and removes sufficient of the water within them
to create a partial vacuum.
Each bladder has a trap door beside it with trigger hairs.
Now all the bladderwort has to do...
..is to bide its time.
It only takes one touch
for the trap door to snap open...
..and suck in its prey.
It's all over in a millisecond.
And after it has fed, a bladderwort has enough energy
to produce another tendril
to search for another Bromeliad pool.
Swamps and bogs are also poor in nutrients.
So several plants that live in such places catch insects too,
if they can.
The leaves of Sundews are covered with long, red hairs,
each tipped with a droplet.
These glistening globules are,
in fact, glue.
Once the Sundews detect the taste of their victim's body,
they flood it with digestive enzymes.
The little body disintegrates.
And the Sundew gets the nutrients it needs.
Another plant has an even more elaborate way
of catching a meal.
The Venus Flytrap has leaves that are lined
with interlocking teeth.
It attracts insects by producing a sweet perfume,
just as a flower does.
It, too, has a hair trigger.
And another insect is caught.
But the technique is more complex than it might seem.
The Venus Flytrap has a problem.
It needs to avoid false alarms,
snapping shut on something inedible, like a raindrop
or a little bit of twig.
That would be a waste of both time and energy.
So how does it avoid that?
Well, it does it by counting.
If I touch this one,
sensitive hair just there...
..no reaction.
That could be a false alarm, but the plant remembers that
for 20 seconds.
And if I touch it a second time within that time,
then that's much more likely to be worth eating.
And so...
..it closes.
So far, so good, but now it needs to be absolutely certain
that it's got something worth eating,
so it continues counting.
Only after it has totted up five separate touches to those hairs
will it give the final squeeze and then begin to produce the liquid
from the surface of the leaf, which will dissolve the body
of its unfortunate victim.
The Flytrap now has enough energy to produce flowers
and attract pollinating insects.
Wind and insects between them pollinate virtually all land plants,
but neither method can be used by plants that live
entirely underwater.
So some lead double lives.
A chalk stream in southern England, and swaying in the current
is a plant for which these rivers are famous.
This is water-crowfoot, a kind of aquatic buttercup.
For most of the year, it is underwater.
And if I take this underwater camera...
..you can see its floppy stems grow horizontally.
That reduces the risk of being swept away by the current.
But each spring, when it's time to flower, it produces
something crucially different...
..a stem that is stiff enough to resist the current
and lift its flowers into the air above.
And now, of course, they can get help from insects.
So every year, in part, at least,
water-crowfoot becomes a land plant...
..and provides us with one of the loveliest natural spectacles
of the early English summer.
Water-crowfoot is not the only water plant to lift its flowers
above the surface.
Plants do so all around the world.
From the swamps of the Pantanal...
..to the lakes of Thailand,
they all burst into spectacular bloom.
Once they've been pollinated, they produce seeds.
And now their flowers have done their job,
some return to a life under water.
Now they must ensure that some of their seeds
will find suitable places in which to germinate.
Bullrushes every year produce these long, brown, velvety objects.
Look what happens when I break one open.
It contains almost a quarter of a million seeds.
Each seed is attached to a delicate parachute.
Even the slightest breeze will lift it and may carry it
for very long distances indeed.
So even though suitable stretches of fresh water are few
and far between, there's a good chance that at least one
will end up in a place where it can grow.
Much bigger seeds, of course, can't travel by air.
A river can provide transport,
but it's a one-way journey downstream
that often ends up in the sea.
And that's not ideal.
So how can any riverside plant avoid this and travel upstream?
Here, along the Bonito River in Brazil,
a variety of trees manage to do exactly that.
They embed their seeds in the middle of soft, sweet fruit.
Monkeys, such as these capuchins,
make a meal of them just as soon as they're ripe.
But monkeys are very wasteful feeders.
And what's not eaten ends up in the river
and is washed away.
But not all.
In the fruiting season, hundreds of Piraputanga fish
gather beneath these trees.
But the Piraputanga want more than the monkeys' leftovers.
The brightly coloured fruits are clearly visible, even to the fish
in the water below.
And some manage to claim them
even before a monkey does.
This isn't a skill mastered by just one particularly
successful acrobatic fish.
Many of the Piraputanga can do this.
Nor is this a disaster for the tree.
Far from it.
These Piraputanga are migratory,
heading many miles upriver to spawn.
The trees, by enticing the fish to eat their fruits,
have a perfect means of transport for their seeds.
With luck, the seeds will be deposited many miles upstream.
The ability to colonise new habitats
has allowed one group of flowering plants to venture out of fresh water
and into a world that may look the same to us,
but for a plant is crucially different.
The much greater, saltier world...
..the sea.
This is a fruit from one of the most important plants on the Earth today.
Seagrass.
This particular one is floating off the coast of Formentera
in the Mediterranean.
100,000 years ago, a seagrass seed like this
sank to the sea floor just here.
And, eventually, it produced...
..a great meadow.
A meadow that is still flourishing today.
It did so by cloning itself.
Now over ten miles across,
it's not only one of the largest living
organisms on Earth,
it's also one of the oldest.
And it supports a rich community of many kinds of animals.
It's become a kind of marine savannah.
Over 1,000 species now live here.
Some, like these elegantly camouflaged pipe fish,
live nowhere else but amongst the seagrass.
Seagrass fringes many of the world's coasts.
Turtles depend upon it, too.
And so do Dugong - animals that are sometimes called,
very appropriately, sea cows.
Today, seagrass plays a critical role in maintaining the health
of our planet.
It creates stores of carbon around its roots
at an enormous rate.
35 times faster, in fact, than plants that live on the floor
of a tropical rainforest.
Here in Formentera,
it's possible to see, beneath the living seagrass,
layer upon layer of trapped carbon
that the plants have accumulated over the past 2,000 years.
Seagrass, however, is easily destroyed by human disturbance.
A third of the world's underwater meadows have already been lost,
and many more are in decline.
Biologists are now striving to not only protect the remaining meadows,
but to restore them.
One plant at a time.
Seagrass could be a valuable ally
in our fight against climate change.
Today, water worlds everywhere are under threat.
Many of their inhabitants are disappearing
without us even being aware of their existence.
The plants that grow in water are probably the least noticeable.
They're certainly the least studied.
But the more you know about the problems of living in that way,
the greater the wonder of their success.
Surely they deserve more of our attention
and, most importantly,
our care.
This vast wetland is the Pantanal.
The Water World's team are heading to a plant battlefield.
The home of Brazil's giant water lily.
This is like seeing the end of a war.
There are leaves growing on top of each other,
flowers going through leaves.
Unbelievable!
To capture this story in all its detail would take over a year
and require a unique Green Planet approach, both filming here,
and, in a parallel mini Pantanal,
in deepest, darkest Devon.
This is the unique world of specialist time lapse cameraman
Tim Shepherd.
Tim has the reputation of being able to think like a plant.
It's absolutely crucial that you get the plant really happy.
And to make the giant lily feel totally at home,
Tim must build a little piece of Brazilian wetland.
First, a 10,000 litre tank.
Hundreds of bricks, almost 1,000 kilos of soil
and countless cups of tea later,
the foundations are complete.
So far, so good.
Now time to prepare for the new green pellet camera system.
We're trying to assemble the main gantry framework
so that we can mount the moving rig on top of it.
So it's a bit of a fiddle to get all the screws
in all the right places, basically.
After a few weeks, the building works are complete.
The flood can now begin.
Tim needs to be sure everything in the room is heated
to tropical temperatures...
..before the star of the scene can move in.
Carefully grown at the Royal Botanic Gardens at Kew, especially for us.
Everything depends on this one plant.
There will be no time for a second attempt.
And even more important for Tim
to keep his guest happy and healthy.
This big monster need a lot of feeding.
We found we need about five sand bags full of compost
every two or three weeks, so we just sort of lower them in
and stick them down by the roots.
There you go.
Whilst the Devon giant settles in,
the Pantanal crew are continuing to get their shots.
Time to see some giant water lilies underwater.
And I hope there's no anaconda.
Ooh! Mission accomplished!
The pressure is now on Tim.
After months of pampering, the giant lily is ready for action.
First thing to film is a leaf spike rising up from the depths.
Luckily, there are no anacondas here.
The special camera weighs over 40 kilos.
It's suddenly become less heavy, which is good.
The new rig means Tim will be able to follow
the emerging plant in any direction.
Wow, fancy!
The technology is working well,
but nature is starting to derail Tim's plans.
We're tangled up in all these weeds.
What happens is we've got a bit of an ecosystem developing here
and, before you know it, you get masses and masses of algae
growing in amongst it all.
Cor!
Think I've just released some anaerobic gases there.
No, not me, the algae!
State of the art tools help keep the algae at bay.
Eurgh!
Just in time for Tim to film lift-off.
That's quite nice coming out of the water, look at that!
Tim's focus can now shift to the battle that's starting to take place
on the surface.
I'm trying to film this new bud coming out on this lily leaf.
Give or take about three days to grow from where it is now.
Somewhere in this zone between these two other leaves.
I want that to last about ten seconds.
Ten seconds is about 250 frames.
That works out about one frame every 20 minutes.
But plants don't read scripts.
It's nature, it doesn't always do what you think it's going to do.
We've had a few false starts where the leaf has swung out of shot
and gone somewhere else.
Or it just grows a lot quicker than you thought.
It's a challenge to get things right.
But with the combination of Tim's expertise and the new camera system,
results are starting to look good.
I think the difference now with this series is we can bring
the plants much more to life as characters and tell their story
in a much more dynamic way.
It's great to be able to follow them around much more with the way
you'd film an animal behaving.
These rigs have given us a whole new realm of possibilities.
After over a year of filming and recording
100,000 separate images,
the secret life of the giant water lily and the battle of the Pantanal
has been revealed.
Next time on The Green Planet,
the ever changing seasonal world,
full of hunters, tricksters
and unlikely alliances.
Plants here are in a race against the clock.
Timing is everything.
The Open University has produced a poster
that explores the vital role that plants have for our planet.
To order your free copy, call...
..or go to...
..and follow the links to the Open University.