All language subtitles for BBC.Botany.A.Blooming.History.2of3.Photosynthesis.720p.HDTV.x264.AAC.MVGroup.org.eng

'It's nearly summer

'and the garden
is bursting with life.

'As a botanist, I'm fascinated
by what makes plants grow.

'For instance, to produce
all this colour and diversity

'you need just a few minerals
and three basic ingredients.'

Water, sunlight and carbon dioxide,

the stuff that I'm breathing out
right now.

And that is all. Nothing else.

Plants turn these ingredients into
food for growth and a waste product
we find very useful - oxygen.

It sounds simple,

but this process is one of the most
fascinating and complicated
in the whole of science.

It's called photosynthesis.

'It'll take the pioneers of botany
over 400 years to work out

'why a leaf needs sunlight,

'what role water plays

'and why a plant can't exist
without carbon dioxide.

'Today photosynthesis is at the
forefront of scientific research.'

If we get this right
and learn from photosynthesis,

we should be able to produce very
quickly a liquid fuel for cars...
No more gasoline, no more diesel?

No more fossil fuel.

'Photosynthesis is taking place
right now in every leaf
of every plant.'

I find that amazing.

'The University of Oxford
Botanic Garden is the oldest
in Britain.

'I've been Director here
for 22 years

'and one of the great things
about the job

'is that I get to live here.'

When the gates are locked,
this enchanting place
becomes my back garden.

It took botanists a long time
to understand the complex process

that transforms a seed
into a fully-grown tree.

Any scientific journey will have
twists and turns. Working out
how plants grow was no exception.

This is the 1648 catalogue
for the Botanic Garden.

"An English list of the trees
and plants...with the Latin names
added there unto."

Very grand.

It only contains about 1,500
species, but it indicates
the growing interest in botany

and it was around this time that
some inquisitive minds began to ask,
"How do plants grow?"

One of the first to investigate
the natural world is an alchemist.

His name is Jan Baptist van Helmont.

'He dabbles in medicine and magic,

'a dangerous combination
in the 17th century.

'Science is seen as a threat
to God and His creation.

'So when van Helmont suggests
that plants could have
miraculous healing properties,

'he's asking for trouble.
And it's not long before trouble
comes knocking at his door.'

In March, 1634,
agents of the Spanish Inquisition
call at a house in Brussels.

They take 55-year-old Jan Baptist
van Helmont away for questioning.

'They interrogate him
and put him under house arrest.

'They accuse him
of violating God's law.'

His crime? The scientific study
of plants and other phenomena.

'Van Helmont is lucky
to escape with his life.

'While under house arrest,
he starts thinking about a question
that's always intrigued him.

'How do plants grow?

'For over 2,000 years, people
believed plants grew by eating soil.

'Van Helmont wants to know
if this is true,

'so he devises an experiment,

'one that hopefully won't
attract the attention
of the Spanish Inquisition.'

Van Helmont used a willow tree
and a wagon full of soil.

I'm using a bay tree and less soil,
but the principle's the same.

The first thing Van Helmont did
was to weigh his tree
and note its weight.

Next he weighed the soil,

dry soil because he didn't want
water to affect its weight.

Van Helmont then planted his tree,

watered it

and his experiment was ready to go.

'Each of my bay trees represents
a year in the growth of the willow
tree that van Helmont planted.'

He watched it grow for not one year
or two years,

but he tended the tree
for five years.

And then he re-weighed it.

After five years, the tree has
gained a hefty 12 stone.

'The van Helmont dries
and weighs the soil.

'The soil weighs almost exactly
the same as it did five years ago.'

He concludes the tree has grown
not by eating soil,
but by drinking water.

After all this effort, van Helmont
decides not to publish his results.

He is scared.

And with good reason.

'His experiment relies on evidence,
not faith.

'He doesn't want to risk getting
on the wrong side
of the authorities again,

'so his results are only published
after his death.'

For all his personal sacrifice,
van Helmont was wrong.

Water IS important
for the growth of plants,
but it is far from the whole story.

'He misses something fundamental
and he isn't the only one.

'I've found a document
at my Botanic Garden which shows

'how little people in
the 17th century knew about plants.'

Now look at this.
This is a plan of the Oxford
Botanic Garden in 1675.

And up here in the top right-hand
corner is a new addition,
a house for plants.

This was the pride and joy
of the Director back then.

His baby,
his big 17th-century project.

But if you look closely at it,
you can see that there's a reason
why this wasn't a great success.

There's something missing
from this house.

And it's the fact that
there are virtually no windows

and those that are there are tiny.

Hardly any windows
and no glass in the roof.

They were never going to grow much
in here.

What is really interesting
about this is that it clearly shows

that 17th-century botanists
had not made the connection between
the growth of plants and light.

'It sounds obvious to us today,
but back then many people believed

'that leaves grew by God's will.

'So suggesting sunlight plays a part
is pretty radical.

'It's an important step on the road
to understanding photosynthesis.'

In the spring of 1779,
a brilliant Dutch physician
took a carriage from London

to take the air
in the English countryside.

He didn't know it yet,
but this pioneering doctor
was going to open a new chapter

in the story of how plants grow.
His name was Jan Ingenhousz.

As a young man,

he had a gift for science
and for medicine, inspired by
his father's work as an apothecary,

making remedies for ailments.

His leap to fame came not
from studying plants.
He was a smallpox inoculator.

'It's a well-paid job,

'so Ingenhousz can afford to rent
a plush villa

'He exchanges the distraction
of the city for the tranquillity
of the countryside

'with a plan to write a book
about smallpox,

'but it's the countryside
that soon becomes the distraction.'

It wasn't long before Ingenhousz
put his book on the back burner.

Instead, he turned his attention
to the countryside and the plants
that flourished all around him

and he embarked on a series of
experiments that would revolutionise
our understanding of plants.

'In the late 18th century,
it's the fashion among scientists
to investigate gases.

'One eminent scientist suggests
that plants give off gas.

'Ingenhousz sets up an experiment

'to find out if this is true.'

His test was simple.
He collected leaves from his garden
and he put them in water.

Ingenhousz then observed
his experiment.

When watching plants,

patience is important.

'Ingenhousz believes that
if he puts plants under water,

'any gas given off will rise
to the surface as bubbles.

'This will give him a clue
as to how plants grow.'

As much as he tried, he could not
get any of his submerged leaves
to give off any gas

until one day his attention
is caught by a sample

in a shaft of sunlight.

Once again,
Ingenhousz observes his experiment.

After just 10 minutes, something
really interesting is happening.

The sample in the shade,
same old story, nothing.

But the sample in the shaft of light
is different. Tiny bubbles of gas
are emerging from the leaves.

For Ingenhousz,
this was a really exciting moment.

For the first time, he had made
the connection between sunlight
and the production of gas in leaves.

'Ingenhousz proves that plants
exposed to sunlight
do indeed give off a gas.

'Now he wants to find out
what that gas is.'

The tiny bubbles of gas
released by the leaves have
accumulated in the top of the jar.

If I take this glowing splint
and put it in there, it re-ignites.

Indicating the presence of oxygen.

'Sunlight triggers the release
of oxygen from leaves.

'Ingenhousz knows
it's a significant discovery.

'He has to be sure he's right.

'There follows a summer
of frenzied activity at the villa.

'The doctor turned botanist repeats
the experiment over and over again.'

Ingenhousz used all sorts of leaves
from plants in his garden.

Holly, ash, nettles and oak.

Each one he immersed in water
and placed one in the sunlight
and one in the shade.

He even visited the King's gardener
at Kew who gave him leaves
of exotic plants like cocoa.

Every leaf that was placed
in the sunshine bubbled.

'Ingenhousz wants to know
if it's the sun's light or its heat
that causes the gas to be released.

'So he puts leaves in water
near an open fire and watches them.

'When no bubbles are given off,
he knows he's right.

'It's the sun's light,
not its heat that's important
for the production of gas in plants.

'He then repeats his experiment
with different leaves
and gets the same result.'

Ingenhousz began to realise
that this process was universal.

'His holiday has taken
an unexpected turn.

'He arrived a successful doctor,

'he leaves a pioneering botanist,
having unlocked a key part
of photosynthesis.

'Who would have thought that plants
produce a waste product that makes
all human and animal life possible?

'Oxygen.'

It would be 100 years before
botany took another leap forward

and this advance was made
by one of the giants of science,

a man who deserves
to be as well-known as Darwin.

'Julius Sachs was born in 1832.

'He has a passion for plants
that would come
to dominate his life.

'As a schoolboy,
Sachs is fascinated by nature.'

He wasn't interested in science, not
then. He was just mad about plants.

'Every day before school,
he collects and carefully records
the local flora.

'As a botanist, I completely
understand where he's coming from.

'That desire to surround yourself
with plants.

'If you get the bug early,
it never leaves you.'

So when Sachs went out
into the countryside in Germany
to collect flowers,

he was undertaking
a very personal activity,

but at the same time
joining a tradition that goes back
at least four centuries.

You're not just collecting
this specimen for yourself,

but for a worldwide record of where
particular plants were growing
on a particular day.

And around the world
there are millions of specimens
like this

put together and collected
by people like Sachs.

I find it
a very satisfying activity.

And...

I'm sure that Sachs found it
equally peaceful and rewarding.

'It's a passion that Sachs pursues
as he grows up,

'but these idyllic days spent
collecting plants are about to come
to an abrupt end.'

When Sachs was 17,
personal tragedy struck

with the death of his mother, father
and one of his brothers
in the same year.

He drops out of school.

'Without his parents,
the young Sachs is penniless.

'Then a family friend offers him
a job at the University of Prague.'

His professor drove him hard.

'He's forced to work long hours
in the laboratory.

'The job gives the young Sachs
an understanding of the rigorous
methodology required of a scientist.

'He has just enough money to live,
but not nearly enough time
to pursue his real passion -

'plants.

'He turns to drugs
to help him stay awake,

'working for his employer during
the day and for himself at night.

'Over the next 20 years,

'Sachs conducts thousands of
experiments and writes up
his results in meticulous detail.'

Sachs toiled for many years
before producing this, his Textbook
of Experimental Plant Physiology.

It's all in here - the role
of light, the need for gases,
the need for water.

This book became the standard
textbook for plant biologists
in Europe.

It was translated into English

and it is a quite, quite beautiful
piece of work.

Wonderful, wonderful detail.

It's a true magnum opus.

Phenomenal.

'This book is the making of him.

'Offers of work flood in.

'I've come to Wurzburg
in Central Germany.

'It's here that Sachs is appointed
head of Europe's top botanical
institute in 1868.

'He's just 36 years old.'

So from his undeniably humble
origins, Sachs arrives in Wurzburg
as the leading botanist in Europe.

He's the head
of a big university department
with his own research group

and he drives that research group
with the same obsession
that he drove himself

and he still relies on drugs
to keep himself going.

But he was still driven.
He still wanted to know more.

He still wanted to know
what made plants grow,

how they took that light
and what they did with it.

'Only now he has the reputation,
money and resources
to tackle these big questions.

'This time he's the one
driving his colleagues hard.

'Today there's an institute
dedicated to Sachs
at the University of Wurzburg.

'Professor Markus Riederer
is the Director.'

Wow!

These are his paintings he did
himself for using them in lectures.

So this is 19th-century Powerpoint!

It is! Only rather more beautiful.

When you step back
to where the students saw it,
it looks beautifully detailed.

The right scale. Indeed.
That's terrific.

So what else have you got?
Is this his microscope? It is, yeah.

It says Sachs on it.
That's tremendous.

So down here, are these
the accounts for the laboratory?
No, it's his private accounts.

He had a family - a wife and three
children. Did they ever see him?

I cannot believe that.
He always worked.

'His personal accounts
include a few surprises.'

That's cocaine.

Cocaine. OK. In his accounts.
It was legal then.

Oh, OK!

So did that keep him going
14 hours a day? Exactly.
To produce this work. Ja, ja.

'Sachs' desire to understand
what makes plants grow
is all-consuming.

'He knows sunlight produces gas
from leaves. This gas is oxygen.

'What he doesn't know
is why sunlight is so important.

'Professor Riederer recreates one
of Sachs' best-known experiments.'

I have a leaf which has been
in the light all day. A normal leaf.

That's a normal leaf
that has seen hours of light.

And Sachs wanted to find out
what was inside it. Exactly.
Enabling it to grow. Exactly.

'By the 19th century, botanists knew
that a plant's growth wasn't
down to water and sunlight alone.

'Every green plant stores
its energy by making something
called starch.

'It's a vital component
of the human diet and it's the power
at the heart of a growing plant.

'Knowing this, he sets out
to discover the role sunlight plays
in the production of starch.

'He strips the green colour
from a leaf and applies iodine
to the white leaf.

'He knows that iodine will react
with starch produced in the leaf,
turning it black.'

The starch is stained now.
It certainly is.

Hey, presto!

So this leaf, which had been grown
normally in the sunlight, has gone
black because it's full of starch.

Yeah.

'Now
Sachs tries the experiment again.

'This time he uses a leaf
that has seen no sunlight
for 12 hours.

'Again, he strips the green colour
out of the leaf.

'This time when the iodine is added,
nothing happens.

'The leaf stays completely white.

'Having been left in the dark,
it contains no starch.

'Sachs carries out one final test.

'Part of a leaf is covered up
while another part of the same leaf
is left uncovered.'

We have our version of this.

'He then places the leaf
in the sunlight.

'If Sachs is right, only those parts
of the leaf exposed to the sun
should produce starch.'

Part of this leaf should have starch
in, the bit that was illuminated.

And the bit in the shade should not.

This is an exciting moment,
isn't it? It is exciting. It is.

So on goes the iodine.

We're starting to see
some of the tissue... Ah!

Our "Light" is coming out!
Now look at that!

It's back to front,
but you can already see
that the part of the stencil

where the light went through,
the leaf is black.
So starch has only been formed

on the part of the leaf
that was exposed to the light.
It's like photography. It is!

That wonderful moment in a darkroom
when the picture appears.

So there you are.

Fantastic. And you've got
a beautiful demonstration,
very elegant, very simple,

that light equals starch,
shade equals no starch.
That's right.

This was a breakthrough.
It was a monumental quantum step up

in our understanding
of how plants grow

and it's one of those experiments
when you think, "Why didn't I think
of that? Why didn't anybody else?"

The fact that Sachs did it

shows just how he was
so far above his contemporaries

in plant science,
in botany at that time.

'Sachs doesn't stop there.

'He wants to find where in the plant
the starch is produced.'

Sometimes science needs
new tools to develop
and botany was no exception.

When, in the mid-19th century,
a new generation of microscopes
became available,

Sachs was able to look
right inside the leaf.

When he looked down the lens
of the microscope,

Sachs could see inside each cell
and it must have been
as exciting then as it is now.

What he saw inside the cells

were small structures.

Solid structures.

And he realised that this is where
the starch was being produced.

And he had found the factory that
fuelled the growth of the plant.

And these small structures in
each cell are called chloroplasts.

And the energy produced
within these chloroplasts

is what goes on to fuel the growth
of the plant.

Not only that, but the production
of flowers, seeds,

fruit and the next generation.

Now, 150 years later,

we have microscopes that enable us
to look inside living cells...

..and reveal what's going on
inside them.

Sachs would have been amazed to see

that the chloroplasts
are not sitting in the cells

inactive and static, as they were
on his microscope slide,

but they are jostling for position,

so that the production of starch
is maximised

as the light changes.

It's the most amazingly efficient
production system in nature.

As sunlight hits a leaf,
the chloroplasts leap into action.

When this short clip is repeated
and speeded up,

we can see these chloroplasts
vying with each other
to grab the sun's rays.

This wonderful dance
of the chloroplasts
is going on all around us

in what seem like static leaves

and the plant is doing it
to ensure that it captures
just the right amount of light -

not too little and not too much.

It would have been wonderful
to be able to show this to Sachs,

so that he could see that
the chloroplasts that he observed...

..are moving
in this quite beautiful way.

Plants produce sugars which
they store in the form of starch.

Sachs shows where in the plant
this happens,

how in fact a plant grows.

Sachs would have been astonished
to see what happens
inside this potato cell.

To begin with,
there's no sign of starch.

Yet just after a few hours sitting
in the sunlight, the cell
is packed full of starch grains.

In just over 200 years, the pioneers
of botany have cracked some of
the big questions of photosynthesis.

They knew that plants
don't eat soil,

water and sunlight drive growth.

They had also worked out
that leaves give off a gas
when exposed to the sun.

That gas is oxygen.

And thanks to a devastatingly simple
experiment, they knew that plants
use sunlight to produce sugars,

a source of energy
that gets stored as starch.

All in all,
a pretty impressive body of work
for the fledgling science of botany.

There is still something missing.

Without it,
photosynthesis is impossible.

And it's in the very air we breathe.

Carbon dioxide.

When botanists used microscopes
to examine the surface of leaves...

..they discovered
something rather surprising.

The underside of a leaf is covered
with what looks like tiny pores.

Modern microscopes show these
in amazing detail.

They're called stomata and
it's through these tiny openings

that plants take in carbon dioxide
from the air around them.

These stomata can open and close,

thereby constantly regulating
the amount of carbon dioxide
getting into the plant.

I'd like to think that a breath
I exhaled 30 years ago now exists
in the bark of this tree.

There is a direct link

between our lives
and the lives of plants.

We give plants carbon dioxide
to fuel their growth...

..and they give us the oxygen
we need to survive.

Botanists in the 19th century knew
that plants absorbed carbon dioxide.

It wasn't until well into
the 20th century that they found out
what the plant did with it.

It's the last major piece in the
photosynthesis puzzle to be solved.

Take a look at this photograph
from the 1940s.

It shows two men examining a camera,
both of them scientists
at the top of their game,

nothing unusual in it at all.

Except behind this photograph
is a story of betrayal

and a bitter feud
that would last for four decades.

'The man in the white shirt
is Andrew Benson.

'Benson is responsible for one
of the most important discoveries
in the story of photosynthesis.

'His boss is Melvin Calvin,

'a brilliant chemist.

'Both men are working
at the University of California
at Berkeley.

'Their research is focused
on one question -

'what does a plant do
with carbon dioxide?

'Professor David Beerling's
working life is devoted
to the science of plants.

'For him, the meeting
of Calvin and Benson is pivotal

'to the understanding
of photosynthesis.'

So what do we know
about these two men?

Benson was really following his own
intuition and experimental programme

and much of the work that he did
Calvin was unaware of.

Calvin had a lot going on and he was
involved in running this lab
and other research questions.

He also had his own personal theory
about how photosynthesis was working

and he was very focused on addressing
his own particular pet theory,

and all the time
you've got Benson looking on
and seeing his boss pursuing

what he knew to be,
you know, a dead end.

That's not a great basis
for a working relationship. Rivals
in the same team, no, not at all.

To begin with,
things are very different.

Calvin and Benson work
closely together,

trying to figure out how plants use
carbon dioxide to fuel their growth.

Once again, botany benefits
from a leap forward in science.

Foremost among the new technologies
of the age is a machine
called a cyclotron.

Invented at the Berkeley
Radiation Laboratory,

the cyclotron is
a particle accelerator.

It allows scientists to study
the nucleus of the atom.

CLICKING SOUNDS

But that's not
why it interests Benson.

The cyclotron produces
radioactive carbon atoms.

'The Atomic Age.

'Here is the answer to a dream
as old as Man himself,

'a giant of limitless power
at Man's command.

'And where was it science found
that giant?

'In the atom.'

If the atom is radioactive,
you can follow it wherever it goes.

The idea is to replace the normal
carbon atom in carbon dioxide

with a radioactive carbon atom.

By making
the carbon dioxide radioactive
before a plant takes it in,

Benson believes he can track
carbon's journey through the plant.

If this works,
Benson will have discovered
how a plant uses carbon dioxide,

something no-one else
has done before.

For a scientist, it doesn't get
any more exciting than this.

At the heart of the experiment is
a glass disc shaped like a lollipop.

It contains green algae
growing in conditions
that are perfect for photosynthesis.

Inside his disc were algae
busily photosynthesising away.

When he introduced
the radioactive carbon dioxide,

the algae absorbed the gas.

He then killed the algae
and the chemical reactions
stopped instantly.

'By killing the algae with alcohol,
Benson freezes a moment in time.

'He then examines the dead algae
to see how they've used the carbon
in carbon dioxide to make sugars.

'The radioactive compounds
in the algae are separated
on to sheets of paper.

'These sheets are then pressed
against X-ray sensitive film

'to produce something
called a chromatogram.

'Each fuzzy blob here shows where
the radioactive carbon has gone.'

Why did a few smudges create
so much excitement?

This doesn't look very impressive,

but this must have been their Eureka
moment when they started getting
these chromatograms. Really? Why?

Because they realised that they could
now see some of the key compounds

that had used the radioactive carbon
they'd fed the algae. So each blob
is a different molecule?

Each of these smudges represents
a different chemical compound
or a different sugar

that represents a different stage
in the pathway to carbon.

'The pathway to carbon
is effectively a road map,

'showing how the plant makes sugar.

'Understanding the first step
on that road is crucial -

'how a plant splits carbon
from carbon dioxide.

'Benson believes the answer lies
with a protein
that is common to all plants.

'Calvin, on the other hand, has
his own grand theory and isn't much
interested in what Benson is up to.

'So to begin with, Benson doesn't
tell his boss what he's doing.

'Calvin's theory of photosynthesis
is eventually proved wrong.

'Benson is the one
who gets it right.

'It's Benson who shows what happens
during that first crucial step

'when a plant grabs hold
of the carbon in carbon dioxide.'

Photosynthesis is often shown as
carbon dioxide plus water and light

equals sugar and oxygen.

This seems to imply
that that's a gross simplification.

Yes, it's accurate,
but it hides a huge amount of detail

and a huge amount of elegance
in the biochemistry.

So it's not one big step, it's lots
of tiny little hops? That's right.

'Mother Nature doesn't give up
her secrets that easily.

'Every smudge has to be identified,

'then they need to figure out
how all the compounds work together.

'It's a project
that takes ten years to complete.

'Benson receives no recognition
for his work.'

It's a familiar story.
Someone makes a great discovery...

And someone else takes the credit.

In 1954, Benson is sacked
from the university,

leaving Calvin to work on
without him.

I want to show you another photo.

It's 1961 and Melvin Calvin
is receiving his Nobel Prize

for cracking the role of carbon
in photosynthesis,

but there's something
or someone missing.

Andrew Benson is nowhere
to be seen.

To begin with, both men are credited
for their work on photosynthesis.

Now only one name takes
centre stage.

The passing of the years did little
to soften Calvin's approach
to his colleague.

This is Melvin Calvin's
autobiography and it tells a story

of how he and his team unlocked
the secrets of photosynthesis.

It was published 30 years after
he was awarded the Nobel Prize

and in all 175 pages,

there is no mention
of Andrew Benson. Not once.

It's as though he never existed.

'Carbon's journey from gas to sugar
became known as "the Calvin cycle".

'Today, many botanists recognise
Benson's contribution

'and call it
"the Calvin-Benson cycle".

'Benson may have missed out
on the Nobel Prize, but his
contribution hasn't been forgotten.'

So how important is Benson's work?

Andy Benson's discoveries
were absolutely amazing.

They filled a huge gap
in our knowledge
about how plants photosynthesise

and in a sense the discovery
of that pathway of how they do that

is comparable to Watson and Crick
figuring out the structure of DNA.

Today, we not only know
how plants grow,

but with the latest technology,
we can watch them grow,
cell by cell.

The tip of this root is forcing
its way through the earth.

By taking carbon dioxide
and converting it
into sugars and starch,

the plant has the energy
it needs to grow.

It may seem like we now know
everything there is to know
about photosynthesis...

..but that's not the case.

For instance, the environment
in which plants grow can vary
dramatically and yet they survive.

Plants are very sophisticated.

From the Equator to the Arctic
Circle, they photosynthesise
in all sorts of conditions.

And they have to respond to
their environment in order to grow.

And even here in Britain,
plants have a lot to contend with.

Whether they live high on a hill top

or down on the valley floor,

plants have adapted
to where they live.

Take this ivy, for example.

It's growing on a north-facing cliff
so it gets no direct sunshine.

Furthermore, it's got trees forming
a canopy over the top of it.

It's got no real soil to get
its roots into, so it has
no permanent supply of water

and yet there's lots of it.
It is brilliantly adapted
to these growing conditions.

Whether it's poor light
or not enough soil,

plants have to make the most
of their surroundings.

That's because, unlike me,
they're rooted to the spot.

They can't go searching for water
if they're thirsty

or find a shady spot
to hide from the sun.

Up on the top of the hill,
there's plenty of light.
That's not a problem.

Here, it's the wind
drying out the plants

that makes water the limiting factor
for photosynthesis.

Plants either adapt or die,

so they've come up with clever ways
to survive.

And we've developed methods to turn
this ability to our advantage.

Farmers have learned how to make
the most of photosynthesis
in all sorts of conditions

and in modern glasshouses,
they can manipulate the environment
to increase production,

often in ways
that are quite surprising.

SHEEP BLEATING

The Netherlands is one
of the world's smallest countries,

yet it has become one of
the world's biggest food exporters.

In these vast greenhouses,

commercial growers have learned
to manipulate the building blocks
of photosynthesis.

They don't rely on sunlight
to grow crops.

They can make their own
with the help of 3,500 light bulbs.

When the sun goes down,
the lights come on
and the plants continue to grow.

By changing the lighting conditions,

they can bring forward
the growing season of these peppers
by four weeks.

More light buys the plant more time
to turn sugar into fruit.

With sunlight guaranteed,
this greenhouse produces
14 million peppers every year.

Sunlight isn't the only part
of photosynthesis that can be
manipulated to our advantage.

Thanks to a quirk of evolution,

changing the levels
of carbon dioxide can also have
a dramatic effect.

There have been times
in the history of the Earth

when the carbon dioxide levels
were very different

and as a result, plants have
the capacity to use extra
carbon dioxide to make more sugar

and to produce bigger fruit.

Commercial growers have been quick
to exploit this legacy
of our planet's past.

Today, this Suffolk greenhouse
produces 50% of all the tomatoes
grown in Britain.

The secret to more tomatoes
is more carbon dioxide.

Next door to the greenhouse
is this factory.

It generates two waste products.

One is steam
which escapes up these chimneys

and the other is carbon dioxide,

a greenhouse gas that you don't want
to release into the atmosphere.

So instead, this greenhouse gas
gets pumped from the factory
into...a greenhouse.

These plastic tubes have tiny holes

which deliver the gas to the leaves
of the tomato plants.

Give a tomato plant extra carbon
dioxide and it produces more sugar

which makes for a sweeter tomato
which is good for us.

It also doubles the yield

which is good for the grower.

By fine-tuning the environment
of plants,

we can grow more food.

These commercial growers have got
photosynthesis down to a fine art.

They can manipulate it,
but that's as far as it goes.

Plants are still doing
all the hard work.

Turning water and carbon dioxide
into leaves, seeds and fruits
makes huge demands on a plant.

To fuel this growth,
it needs a reliable source of power.

However different they are,
wherever they come from,

plants are all able to survive
and grow because of their ability
to harness energy from the sun.

The amount of light energy converted
by photosynthesis is staggering.

In one year, all the plants
on Earth generate enough energy

to power human civilisation
six times over.

We now know a great deal
about photosynthesis.

We can manipulate it to make
better crops and feed more people.

But this is just the start.
The next step is really exciting.

And if science gets it right,
it will alter lives
for generations to come.

At the University of Glasgow,
Professor Lee Cronin is trying

to recreate photosynthesis
in his laboratory.

Something that plants
have been doing for more
than a thousand million years,

he is trying to do artificially
in a decade.

Plants use the sun's energy to split
water into hydrogen and oxygen,

two gases that could help make
the fuels of the future.

It's this process
that Lee is trying to copy.

This very thin electrode where
you see all these very small bubbles

is a platinum electrode
where the hydrogen is coming off,

and at this black electrode with
the slightly bigger bubble is where
the oxygen is being produced.

This normally happens inside
a leaf, but here it's happening
in this flask. Exactly.

'There's still a long way to go.

'Lee can't split water
using just light.

'Not yet anyway.

'He still needs a battery
to power the process,

'but the potential is enormous.'

If we let this go long enough, the
water in here would get less and less
as it's being converted to the gas

and there'd be nothing left at
the end. How long would that take?

Probably... Well, at this rate,
probably a few days. Right.
So we don't need very much water.

There's a huge amount of gas
locked up in here.

But this is the critical first step
of the photosynthesis story?
Yeah, exactly.

Once we've perfected the first step,
there is a critical part

where we take carbon dioxide from
the atmosphere and complete the story
and turn the carbon dioxide

into a fuel that we could put
in an aeroplane or a car.

So our family cars could start,
in years to come, from a process
like this with water being split?

There's every possibility.
We're very excited about it. Wow!

'So he should be. The prize
is clean and limitless energy.

'No wonder labs like this
all over the world are working hard
to crack the problem.'

If we get this right, if we're able
to understand and learn
from photosynthesis in such a way

that we can surpass evolution if you
like and make an even better device

to take light energy, carbon dioxide
and water and produce a fuel,

then this is going to have
massive ramifications
for our society and our environment.

Lee's work is impressive,

but it shows how sophisticated
photosynthesis is

and scientists will be hard pressed
to replicate it.

The thought that it may provide
an alternative source of energy

confirms the awesome power
of photosynthesis.

To see the power of photosynthesis
in action, take a look
at these images from NASA.

They show how photosynthesis varies
across the globe

with the ebb and flow
of the seasons.

That's not the whole story.

What's fascinating is the oceans.

They're glowing green.

That's because half of the world's
photosynthesis takes place
not on the land, but in the sea.

How close are we to understanding
all there is to know
about photosynthesis?

We understand the broad principles
of how photosynthesis works, but
the real fine detail still eludes us.

We can put a man on the moon,
but we can't mimic photosynthesis.

Botany has come a long way
since the time when people believed
plants eat soil.

Today, we can feed more
of the world's population.

Tomorrow, we may even find a way
to fuel our planet.

And it's all down to photosynthesis,

for me, the most remarkable
and important process on Earth.

Next time on
Botany: A Blooming History...

I'll be looking at how botanists
puzzled over the colours
of snapdragons,

investigated the mysteries
of wild maize

and developed a brand-new science -
plant genetics.

Subtitles by Subtext
for Red Bee Media Ltd 2011

Email subtitling@bbc.co.uk