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'It's nearly summer
2
00:00:12,240 --> 00:00:16,440
'and the garden
is bursting with life.
3
00:00:16,440 --> 00:00:21,680
'As a botanist, I'm fascinated
by what makes plants grow.
4
00:00:21,680 --> 00:00:26,120
'For instance, to produce
all this colour and diversity
5
00:00:26,120 --> 00:00:30,360
'you need just a few minerals
and three basic ingredients.'
6
00:00:32,880 --> 00:00:36,560
Water, sunlight and carbon dioxide,
7
00:00:36,560 --> 00:00:40,000
the stuff that I'm breathing out
right now.
8
00:00:40,000 --> 00:00:42,880
And that is all. Nothing else.
9
00:00:47,400 --> 00:00:54,760
Plants turn these ingredients into
food for growth and a waste product
we find very useful - oxygen.
10
00:00:58,920 --> 00:01:01,000
It sounds simple,
11
00:01:01,000 --> 00:01:06,600
but this process is one of the most
fascinating and complicated
in the whole of science.
12
00:01:06,600 --> 00:01:09,280
It's called photosynthesis.
13
00:01:13,520 --> 00:01:18,720
'It'll take the pioneers of botany
over 400 years to work out
14
00:01:18,720 --> 00:01:21,360
'why a leaf needs sunlight,
15
00:01:21,360 --> 00:01:24,760
'what role water plays
16
00:01:24,760 --> 00:01:29,760
'and why a plant can't exist
without carbon dioxide.
17
00:01:32,120 --> 00:01:37,120
'Today photosynthesis is at the
forefront of scientific research.'
18
00:01:37,120 --> 00:01:41,040
If we get this right
and learn from photosynthesis,
19
00:01:41,040 --> 00:01:47,640
we should be able to produce very
quickly a liquid fuel for cars...
No more gasoline, no more diesel?
20
00:01:47,640 --> 00:01:50,000
No more fossil fuel.
21
00:01:50,000 --> 00:01:57,360
'Photosynthesis is taking place
right now in every leaf
of every plant.'
22
00:01:57,360 --> 00:02:00,480
I find that amazing.
23
00:02:30,800 --> 00:02:36,440
'The University of Oxford
Botanic Garden is the oldest
in Britain.
24
00:02:36,440 --> 00:02:39,520
'I've been Director here
for 22 years
25
00:02:39,520 --> 00:02:43,120
'and one of the great things
about the job
26
00:02:43,120 --> 00:02:45,600
'is that I get to live here.'
27
00:02:49,760 --> 00:02:55,680
When the gates are locked,
this enchanting place
becomes my back garden.
28
00:03:13,240 --> 00:03:18,360
It took botanists a long time
to understand the complex process
29
00:03:18,360 --> 00:03:22,800
that transforms a seed
into a fully-grown tree.
30
00:03:22,800 --> 00:03:29,080
Any scientific journey will have
twists and turns. Working out
how plants grow was no exception.
31
00:03:38,360 --> 00:03:43,160
This is the 1648 catalogue
for the Botanic Garden.
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00:03:43,160 --> 00:03:49,360
"An English list of the trees
and plants...with the Latin names
added there unto."
33
00:03:49,360 --> 00:03:51,440
Very grand.
34
00:03:51,440 --> 00:03:58,360
It only contains about 1,500
species, but it indicates
the growing interest in botany
35
00:03:58,360 --> 00:04:05,080
and it was around this time that
some inquisitive minds began to ask,
"How do plants grow?"
36
00:04:08,880 --> 00:04:13,720
One of the first to investigate
the natural world is an alchemist.
37
00:04:14,720 --> 00:04:17,640
His name is Jan Baptist van Helmont.
38
00:04:21,480 --> 00:04:24,320
'He dabbles in medicine and magic,
39
00:04:24,320 --> 00:04:28,240
'a dangerous combination
in the 17th century.
40
00:04:29,280 --> 00:04:33,240
'Science is seen as a threat
to God and His creation.
41
00:04:36,000 --> 00:04:41,800
'So when van Helmont suggests
that plants could have
miraculous healing properties,
42
00:04:41,800 --> 00:04:47,920
'he's asking for trouble.
And it's not long before trouble
comes knocking at his door.'
43
00:04:55,160 --> 00:05:00,760
In March, 1634,
agents of the Spanish Inquisition
call at a house in Brussels.
44
00:05:00,760 --> 00:05:05,560
They take 55-year-old Jan Baptist
van Helmont away for questioning.
45
00:05:11,120 --> 00:05:15,360
'They interrogate him
and put him under house arrest.
46
00:05:15,360 --> 00:05:19,000
'They accuse him
of violating God's law.'
47
00:05:19,000 --> 00:05:23,840
His crime? The scientific study
of plants and other phenomena.
48
00:05:25,920 --> 00:05:29,920
'Van Helmont is lucky
to escape with his life.
49
00:05:32,200 --> 00:05:38,080
'While under house arrest,
he starts thinking about a question
that's always intrigued him.
50
00:05:39,040 --> 00:05:41,480
'How do plants grow?
51
00:05:48,680 --> 00:05:53,520
'For over 2,000 years, people
believed plants grew by eating soil.
52
00:05:53,520 --> 00:05:57,520
'Van Helmont wants to know
if this is true,
53
00:05:59,120 --> 00:06:01,520
'so he devises an experiment,
54
00:06:02,760 --> 00:06:08,600
'one that hopefully won't
attract the attention
of the Spanish Inquisition.'
55
00:06:08,600 --> 00:06:13,240
Van Helmont used a willow tree
and a wagon full of soil.
56
00:06:13,240 --> 00:06:17,400
I'm using a bay tree and less soil,
but the principle's the same.
57
00:06:17,400 --> 00:06:22,920
The first thing Van Helmont did
was to weigh his tree
and note its weight.
58
00:06:29,080 --> 00:06:31,240
Next he weighed the soil,
59
00:06:31,240 --> 00:06:35,960
dry soil because he didn't want
water to affect its weight.
60
00:06:40,800 --> 00:06:43,640
Van Helmont then planted his tree,
61
00:06:46,680 --> 00:06:48,720
watered it
62
00:06:51,840 --> 00:06:54,000
and his experiment was ready to go.
63
00:07:01,160 --> 00:07:07,640
'Each of my bay trees represents
a year in the growth of the willow
tree that van Helmont planted.'
64
00:07:09,720 --> 00:07:13,800
He watched it grow for not one year
or two years,
65
00:07:13,800 --> 00:07:17,360
but he tended the tree
for five years.
66
00:07:17,360 --> 00:07:19,400
And then he re-weighed it.
67
00:07:23,040 --> 00:07:27,360
After five years, the tree has
gained a hefty 12 stone.
68
00:07:30,800 --> 00:07:34,840
'The van Helmont dries
and weighs the soil.
69
00:07:34,840 --> 00:07:39,320
'The soil weighs almost exactly
the same as it did five years ago.'
70
00:07:42,320 --> 00:07:48,240
He concludes the tree has grown
not by eating soil,
but by drinking water.
71
00:07:58,800 --> 00:08:03,240
After all this effort, van Helmont
decides not to publish his results.
72
00:08:03,240 --> 00:08:05,720
He is scared.
73
00:08:06,800 --> 00:08:09,600
And with good reason.
74
00:08:09,600 --> 00:08:13,680
'His experiment relies on evidence,
not faith.
75
00:08:13,680 --> 00:08:19,760
'He doesn't want to risk getting
on the wrong side
of the authorities again,
76
00:08:19,760 --> 00:08:24,080
'so his results are only published
after his death.'
77
00:08:26,640 --> 00:08:30,720
For all his personal sacrifice,
van Helmont was wrong.
78
00:08:30,720 --> 00:08:36,200
Water IS important
for the growth of plants,
but it is far from the whole story.
79
00:08:39,600 --> 00:08:44,360
'He misses something fundamental
and he isn't the only one.
80
00:08:48,160 --> 00:08:52,560
'I've found a document
at my Botanic Garden which shows
81
00:08:52,560 --> 00:08:56,840
'how little people in
the 17th century knew about plants.'
82
00:08:58,960 --> 00:09:05,160
Now look at this.
This is a plan of the Oxford
Botanic Garden in 1675.
83
00:09:05,160 --> 00:09:11,240
And up here in the top right-hand
corner is a new addition,
a house for plants.
84
00:09:11,240 --> 00:09:15,600
This was the pride and joy
of the Director back then.
85
00:09:15,600 --> 00:09:19,640
His baby,
his big 17th-century project.
86
00:09:21,280 --> 00:09:28,200
But if you look closely at it,
you can see that there's a reason
why this wasn't a great success.
87
00:09:29,240 --> 00:09:32,640
There's something missing
from this house.
88
00:09:32,640 --> 00:09:37,200
And it's the fact that
there are virtually no windows
89
00:09:37,200 --> 00:09:40,440
and those that are there are tiny.
90
00:09:40,440 --> 00:09:44,440
Hardly any windows
and no glass in the roof.
91
00:09:44,440 --> 00:09:48,080
They were never going to grow much
in here.
92
00:09:48,080 --> 00:09:52,120
What is really interesting
about this is that it clearly shows
93
00:09:52,120 --> 00:09:59,040
that 17th-century botanists
had not made the connection between
the growth of plants and light.
94
00:10:01,520 --> 00:10:06,360
'It sounds obvious to us today,
but back then many people believed
95
00:10:06,360 --> 00:10:08,920
'that leaves grew by God's will.
96
00:10:09,960 --> 00:10:14,480
'So suggesting sunlight plays a part
is pretty radical.
97
00:10:15,520 --> 00:10:20,200
'It's an important step on the road
to understanding photosynthesis.'
98
00:10:38,560 --> 00:10:44,520
In the spring of 1779,
a brilliant Dutch physician
took a carriage from London
99
00:10:44,520 --> 00:10:48,640
to take the air
in the English countryside.
100
00:10:48,640 --> 00:10:54,600
He didn't know it yet,
but this pioneering doctor
was going to open a new chapter
101
00:10:54,600 --> 00:10:59,200
in the story of how plants grow.
His name was Jan Ingenhousz.
102
00:11:10,000 --> 00:11:12,080
As a young man,
103
00:11:12,080 --> 00:11:17,840
he had a gift for science
and for medicine, inspired by
his father's work as an apothecary,
104
00:11:17,840 --> 00:11:20,560
making remedies for ailments.
105
00:11:20,560 --> 00:11:26,520
His leap to fame came not
from studying plants.
He was a smallpox inoculator.
106
00:11:31,080 --> 00:11:33,440
'It's a well-paid job,
107
00:11:33,440 --> 00:11:37,520
'so Ingenhousz can afford to rent
a plush villa
108
00:11:37,520 --> 00:11:43,520
'He exchanges the distraction
of the city for the tranquillity
of the countryside
109
00:11:43,520 --> 00:11:47,600
'with a plan to write a book
about smallpox,
110
00:11:47,600 --> 00:11:52,160
'but it's the countryside
that soon becomes the distraction.'
111
00:11:55,720 --> 00:12:00,200
It wasn't long before Ingenhousz
put his book on the back burner.
112
00:12:00,200 --> 00:12:06,240
Instead, he turned his attention
to the countryside and the plants
that flourished all around him
113
00:12:06,240 --> 00:12:12,880
and he embarked on a series of
experiments that would revolutionise
our understanding of plants.
114
00:12:12,880 --> 00:12:19,040
'In the late 18th century,
it's the fashion among scientists
to investigate gases.
115
00:12:19,040 --> 00:12:24,240
'One eminent scientist suggests
that plants give off gas.
116
00:12:25,280 --> 00:12:27,920
'Ingenhousz sets up an experiment
117
00:12:27,920 --> 00:12:31,040
'to find out if this is true.'
118
00:12:31,040 --> 00:12:37,040
His test was simple.
He collected leaves from his garden
and he put them in water.
119
00:12:37,040 --> 00:12:40,760
Ingenhousz then observed
his experiment.
120
00:12:40,760 --> 00:12:42,800
When watching plants,
121
00:12:42,800 --> 00:12:45,800
patience is important.
122
00:12:54,560 --> 00:12:58,600
'Ingenhousz believes that
if he puts plants under water,
123
00:12:58,600 --> 00:13:02,960
'any gas given off will rise
to the surface as bubbles.
124
00:13:04,120 --> 00:13:08,080
'This will give him a clue
as to how plants grow.'
125
00:13:13,360 --> 00:13:19,360
As much as he tried, he could not
get any of his submerged leaves
to give off any gas
126
00:13:19,360 --> 00:13:23,560
until one day his attention
is caught by a sample
127
00:13:23,560 --> 00:13:26,080
in a shaft of sunlight.
128
00:13:26,080 --> 00:13:30,000
Once again,
Ingenhousz observes his experiment.
129
00:13:39,520 --> 00:13:43,560
After just 10 minutes, something
really interesting is happening.
130
00:13:43,560 --> 00:13:47,920
The sample in the shade,
same old story, nothing.
131
00:13:47,920 --> 00:13:54,080
But the sample in the shaft of light
is different. Tiny bubbles of gas
are emerging from the leaves.
132
00:13:54,080 --> 00:13:57,520
For Ingenhousz,
this was a really exciting moment.
133
00:13:58,720 --> 00:14:05,400
For the first time, he had made
the connection between sunlight
and the production of gas in leaves.
134
00:14:07,600 --> 00:14:13,200
'Ingenhousz proves that plants
exposed to sunlight
do indeed give off a gas.
135
00:14:13,200 --> 00:14:16,760
'Now he wants to find out
what that gas is.'
136
00:14:25,160 --> 00:14:31,000
The tiny bubbles of gas
released by the leaves have
accumulated in the top of the jar.
137
00:14:31,000 --> 00:14:36,200
If I take this glowing splint
and put it in there, it re-ignites.
138
00:14:37,240 --> 00:14:39,800
Indicating the presence of oxygen.
139
00:14:46,320 --> 00:14:50,360
'Sunlight triggers the release
of oxygen from leaves.
140
00:14:50,360 --> 00:14:54,560
'Ingenhousz knows
it's a significant discovery.
141
00:14:54,560 --> 00:14:57,440
'He has to be sure he's right.
142
00:14:58,760 --> 00:15:03,240
'There follows a summer
of frenzied activity at the villa.
143
00:15:05,880 --> 00:15:10,440
'The doctor turned botanist repeats
the experiment over and over again.'
144
00:15:14,280 --> 00:15:19,560
Ingenhousz used all sorts of leaves
from plants in his garden.
145
00:15:19,560 --> 00:15:23,240
Holly, ash, nettles and oak.
146
00:15:23,240 --> 00:15:29,320
Each one he immersed in water
and placed one in the sunlight
and one in the shade.
147
00:15:31,000 --> 00:15:37,080
He even visited the King's gardener
at Kew who gave him leaves
of exotic plants like cocoa.
148
00:15:37,080 --> 00:15:41,520
Every leaf that was placed
in the sunshine bubbled.
149
00:15:44,880 --> 00:15:51,520
'Ingenhousz wants to know
if it's the sun's light or its heat
that causes the gas to be released.
150
00:15:51,520 --> 00:15:56,200
'So he puts leaves in water
near an open fire and watches them.
151
00:15:56,200 --> 00:16:00,640
'When no bubbles are given off,
he knows he's right.
152
00:16:00,640 --> 00:16:07,120
'It's the sun's light,
not its heat that's important
for the production of gas in plants.
153
00:16:08,200 --> 00:16:14,000
'He then repeats his experiment
with different leaves
and gets the same result.'
154
00:16:15,240 --> 00:16:19,920
Ingenhousz began to realise
that this process was universal.
155
00:16:21,560 --> 00:16:25,560
'His holiday has taken
an unexpected turn.
156
00:16:25,560 --> 00:16:28,240
'He arrived a successful doctor,
157
00:16:28,240 --> 00:16:34,960
'he leaves a pioneering botanist,
having unlocked a key part
of photosynthesis.
158
00:16:41,480 --> 00:16:47,960
'Who would have thought that plants
produce a waste product that makes
all human and animal life possible?
159
00:16:47,960 --> 00:16:50,360
'Oxygen.'
160
00:17:02,160 --> 00:17:07,640
It would be 100 years before
botany took another leap forward
161
00:17:07,640 --> 00:17:12,880
and this advance was made
by one of the giants of science,
162
00:17:12,880 --> 00:17:17,840
a man who deserves
to be as well-known as Darwin.
163
00:17:23,680 --> 00:17:26,560
'Julius Sachs was born in 1832.
164
00:17:26,560 --> 00:17:32,120
'He has a passion for plants
that would come
to dominate his life.
165
00:17:36,520 --> 00:17:40,960
'As a schoolboy,
Sachs is fascinated by nature.'
166
00:17:42,200 --> 00:17:47,200
He wasn't interested in science, not
then. He was just mad about plants.
167
00:17:49,960 --> 00:17:55,680
'Every day before school,
he collects and carefully records
the local flora.
168
00:17:56,720 --> 00:18:01,480
'As a botanist, I completely
understand where he's coming from.
169
00:18:01,480 --> 00:18:05,080
'That desire to surround yourself
with plants.
170
00:18:05,080 --> 00:18:09,560
'If you get the bug early,
it never leaves you.'
171
00:18:10,720 --> 00:18:15,760
So when Sachs went out
into the countryside in Germany
to collect flowers,
172
00:18:15,760 --> 00:18:20,160
he was undertaking
a very personal activity,
173
00:18:21,280 --> 00:18:27,720
but at the same time
joining a tradition that goes back
at least four centuries.
174
00:18:27,720 --> 00:18:32,000
You're not just collecting
this specimen for yourself,
175
00:18:32,000 --> 00:18:38,240
but for a worldwide record of where
particular plants were growing
on a particular day.
176
00:18:38,240 --> 00:18:44,080
And around the world
there are millions of specimens
like this
177
00:18:44,080 --> 00:18:48,280
put together and collected
by people like Sachs.
178
00:18:48,280 --> 00:18:51,880
I find it
a very satisfying activity.
179
00:18:51,880 --> 00:18:53,760
And...
180
00:18:53,760 --> 00:18:59,400
I'm sure that Sachs found it
equally peaceful and rewarding.
181
00:19:00,600 --> 00:19:04,640
'It's a passion that Sachs pursues
as he grows up,
182
00:19:04,640 --> 00:19:10,560
'but these idyllic days spent
collecting plants are about to come
to an abrupt end.'
183
00:19:14,280 --> 00:19:18,600
When Sachs was 17,
personal tragedy struck
184
00:19:18,600 --> 00:19:24,360
with the death of his mother, father
and one of his brothers
in the same year.
185
00:19:26,120 --> 00:19:29,120
He drops out of school.
186
00:19:29,120 --> 00:19:33,160
'Without his parents,
the young Sachs is penniless.
187
00:19:33,160 --> 00:19:37,920
'Then a family friend offers him
a job at the University of Prague.'
188
00:19:39,200 --> 00:19:41,440
His professor drove him hard.
189
00:19:43,120 --> 00:19:47,040
'He's forced to work long hours
in the laboratory.
190
00:19:48,560 --> 00:19:54,640
'The job gives the young Sachs
an understanding of the rigorous
methodology required of a scientist.
191
00:19:57,760 --> 00:20:04,760
'He has just enough money to live,
but not nearly enough time
to pursue his real passion -
192
00:20:04,760 --> 00:20:06,600
'plants.
193
00:20:08,280 --> 00:20:12,080
'He turns to drugs
to help him stay awake,
194
00:20:13,120 --> 00:20:17,880
'working for his employer during
the day and for himself at night.
195
00:20:19,880 --> 00:20:22,800
'Over the next 20 years,
196
00:20:22,800 --> 00:20:29,160
'Sachs conducts thousands of
experiments and writes up
his results in meticulous detail.'
197
00:20:30,560 --> 00:20:38,080
Sachs toiled for many years
before producing this, his Textbook
of Experimental Plant Physiology.
198
00:20:40,160 --> 00:20:47,040
It's all in here - the role
of light, the need for gases,
the need for water.
199
00:20:50,160 --> 00:20:56,520
This book became the standard
textbook for plant biologists
in Europe.
200
00:20:56,520 --> 00:20:59,080
It was translated into English
201
00:20:59,080 --> 00:21:03,080
and it is a quite, quite beautiful
piece of work.
202
00:21:04,920 --> 00:21:07,520
Wonderful, wonderful detail.
203
00:21:07,520 --> 00:21:10,320
It's a true magnum opus.
204
00:21:11,320 --> 00:21:12,800
Phenomenal.
205
00:21:18,160 --> 00:21:21,160
'This book is the making of him.
206
00:21:21,160 --> 00:21:23,600
'Offers of work flood in.
207
00:21:31,640 --> 00:21:35,720
'I've come to Wurzburg
in Central Germany.
208
00:21:37,520 --> 00:21:43,440
'It's here that Sachs is appointed
head of Europe's top botanical
institute in 1868.
209
00:21:45,080 --> 00:21:48,000
'He's just 36 years old.'
210
00:21:50,360 --> 00:21:57,240
So from his undeniably humble
origins, Sachs arrives in Wurzburg
as the leading botanist in Europe.
211
00:21:57,240 --> 00:22:02,640
He's the head
of a big university department
with his own research group
212
00:22:02,640 --> 00:22:08,680
and he drives that research group
with the same obsession
that he drove himself
213
00:22:08,680 --> 00:22:13,640
and he still relies on drugs
to keep himself going.
214
00:22:18,160 --> 00:22:23,160
But he was still driven.
He still wanted to know more.
215
00:22:23,160 --> 00:22:27,200
He still wanted to know
what made plants grow,
216
00:22:27,200 --> 00:22:30,800
how they took that light
and what they did with it.
217
00:22:32,760 --> 00:22:39,440
'Only now he has the reputation,
money and resources
to tackle these big questions.
218
00:22:40,720 --> 00:22:44,840
'This time he's the one
driving his colleagues hard.
219
00:22:51,200 --> 00:22:56,960
'Today there's an institute
dedicated to Sachs
at the University of Wurzburg.
220
00:22:56,960 --> 00:23:00,880
'Professor Markus Riederer
is the Director.'
221
00:23:00,880 --> 00:23:02,360
Wow!
222
00:23:03,400 --> 00:23:08,840
These are his paintings he did
himself for using them in lectures.
223
00:23:08,840 --> 00:23:11,400
So this is 19th-century Powerpoint!
224
00:23:11,400 --> 00:23:14,240
It is! Only rather more beautiful.
225
00:23:14,240 --> 00:23:19,840
When you step back
to where the students saw it,
it looks beautifully detailed.
226
00:23:19,840 --> 00:23:24,560
The right scale. Indeed.
That's terrific.
227
00:23:24,560 --> 00:23:29,240
So what else have you got?
Is this his microscope? It is, yeah.
228
00:23:29,240 --> 00:23:33,200
It says Sachs on it.
That's tremendous.
229
00:23:33,200 --> 00:23:39,280
So down here, are these
the accounts for the laboratory?
No, it's his private accounts.
230
00:23:39,280 --> 00:23:43,720
He had a family - a wife and three
children. Did they ever see him?
231
00:23:43,720 --> 00:23:47,440
I cannot believe that.
He always worked.
232
00:23:47,440 --> 00:23:51,680
'His personal accounts
include a few surprises.'
233
00:23:52,880 --> 00:23:54,960
That's cocaine.
234
00:23:54,960 --> 00:23:59,600
Cocaine. OK. In his accounts.
It was legal then.
235
00:23:59,600 --> 00:24:01,560
Oh, OK!
236
00:24:01,560 --> 00:24:07,160
So did that keep him going
14 hours a day? Exactly.
To produce this work. Ja, ja.
237
00:24:09,360 --> 00:24:14,720
'Sachs' desire to understand
what makes plants grow
is all-consuming.
238
00:24:14,720 --> 00:24:19,440
'He knows sunlight produces gas
from leaves. This gas is oxygen.
239
00:24:19,440 --> 00:24:24,200
'What he doesn't know
is why sunlight is so important.
240
00:24:25,680 --> 00:24:30,520
'Professor Riederer recreates one
of Sachs' best-known experiments.'
241
00:24:30,520 --> 00:24:35,560
I have a leaf which has been
in the light all day. A normal leaf.
242
00:24:35,560 --> 00:24:39,400
That's a normal leaf
that has seen hours of light.
243
00:24:39,400 --> 00:24:45,640
And Sachs wanted to find out
what was inside it. Exactly.
Enabling it to grow. Exactly.
244
00:24:50,000 --> 00:24:56,920
'By the 19th century, botanists knew
that a plant's growth wasn't
down to water and sunlight alone.
245
00:24:56,920 --> 00:25:02,480
'Every green plant stores
its energy by making something
called starch.
246
00:25:02,480 --> 00:25:09,800
'It's a vital component
of the human diet and it's the power
at the heart of a growing plant.
247
00:25:11,320 --> 00:25:17,600
'Knowing this, he sets out
to discover the role sunlight plays
in the production of starch.
248
00:25:17,600 --> 00:25:23,440
'He strips the green colour
from a leaf and applies iodine
to the white leaf.
249
00:25:24,760 --> 00:25:30,480
'He knows that iodine will react
with starch produced in the leaf,
turning it black.'
250
00:25:32,800 --> 00:25:36,760
The starch is stained now.
It certainly is.
251
00:25:36,760 --> 00:25:38,840
Hey, presto!
252
00:25:38,840 --> 00:25:45,560
So this leaf, which had been grown
normally in the sunlight, has gone
black because it's full of starch.
253
00:25:45,560 --> 00:25:47,040
Yeah.
254
00:25:47,040 --> 00:25:50,720
'Now
Sachs tries the experiment again.
255
00:25:50,720 --> 00:25:56,360
'This time he uses a leaf
that has seen no sunlight
for 12 hours.
256
00:25:56,360 --> 00:26:00,240
'Again, he strips the green colour
out of the leaf.
257
00:26:03,800 --> 00:26:07,560
'This time when the iodine is added,
nothing happens.
258
00:26:07,560 --> 00:26:10,480
'The leaf stays completely white.
259
00:26:10,480 --> 00:26:14,880
'Having been left in the dark,
it contains no starch.
260
00:26:17,520 --> 00:26:20,200
'Sachs carries out one final test.
261
00:26:20,200 --> 00:26:26,160
'Part of a leaf is covered up
while another part of the same leaf
is left uncovered.'
262
00:26:28,600 --> 00:26:31,120
We have our version of this.
263
00:26:34,160 --> 00:26:37,200
'He then places the leaf
in the sunlight.
264
00:26:41,320 --> 00:26:47,400
'If Sachs is right, only those parts
of the leaf exposed to the sun
should produce starch.'
265
00:26:50,400 --> 00:26:54,840
Part of this leaf should have starch
in, the bit that was illuminated.
266
00:26:54,840 --> 00:26:57,360
And the bit in the shade should not.
267
00:26:57,360 --> 00:27:01,800
This is an exciting moment,
isn't it? It is exciting. It is.
268
00:27:03,160 --> 00:27:05,120
So on goes the iodine.
269
00:27:08,520 --> 00:27:14,240
We're starting to see
some of the tissue... Ah!
270
00:27:14,240 --> 00:27:18,200
Our "Light" is coming out!
Now look at that!
271
00:27:18,200 --> 00:27:24,800
It's back to front,
but you can already see
that the part of the stencil
272
00:27:24,800 --> 00:27:30,600
where the light went through,
the leaf is black.
So starch has only been formed
273
00:27:30,600 --> 00:27:36,640
on the part of the leaf
that was exposed to the light.
It's like photography. It is!
274
00:27:36,640 --> 00:27:40,840
That wonderful moment in a darkroom
when the picture appears.
275
00:27:40,840 --> 00:27:43,200
So there you are.
276
00:27:43,200 --> 00:27:50,080
Fantastic. And you've got
a beautiful demonstration,
very elegant, very simple,
277
00:27:50,080 --> 00:27:55,880
that light equals starch,
shade equals no starch.
That's right.
278
00:28:04,160 --> 00:28:09,200
This was a breakthrough.
It was a monumental quantum step up
279
00:28:09,200 --> 00:28:12,680
in our understanding
of how plants grow
280
00:28:12,680 --> 00:28:19,000
and it's one of those experiments
when you think, "Why didn't I think
of that? Why didn't anybody else?"
281
00:28:19,000 --> 00:28:21,960
The fact that Sachs did it
282
00:28:23,840 --> 00:28:29,240
shows just how he was
so far above his contemporaries
283
00:28:29,240 --> 00:28:33,440
in plant science,
in botany at that time.
284
00:28:40,120 --> 00:28:42,560
'Sachs doesn't stop there.
285
00:28:42,560 --> 00:28:46,400
'He wants to find where in the plant
the starch is produced.'
286
00:28:52,160 --> 00:28:58,200
Sometimes science needs
new tools to develop
and botany was no exception.
287
00:28:58,200 --> 00:29:03,920
When, in the mid-19th century,
a new generation of microscopes
became available,
288
00:29:03,920 --> 00:29:07,720
Sachs was able to look
right inside the leaf.
289
00:29:08,800 --> 00:29:13,440
When he looked down the lens
of the microscope,
290
00:29:13,440 --> 00:29:19,320
Sachs could see inside each cell
and it must have been
as exciting then as it is now.
291
00:29:19,320 --> 00:29:22,440
What he saw inside the cells
292
00:29:22,440 --> 00:29:25,600
were small structures.
293
00:29:26,640 --> 00:29:28,720
Solid structures.
294
00:29:28,720 --> 00:29:33,600
And he realised that this is where
the starch was being produced.
295
00:29:33,600 --> 00:29:38,440
And he had found the factory that
fuelled the growth of the plant.
296
00:29:38,440 --> 00:29:43,480
And these small structures in
each cell are called chloroplasts.
297
00:29:44,800 --> 00:29:50,240
And the energy produced
within these chloroplasts
298
00:29:50,240 --> 00:29:53,880
is what goes on to fuel the growth
of the plant.
299
00:29:53,880 --> 00:29:58,560
Not only that, but the production
of flowers, seeds,
300
00:29:58,560 --> 00:30:01,280
fruit and the next generation.
301
00:30:03,680 --> 00:30:06,400
Now, 150 years later,
302
00:30:06,400 --> 00:30:12,040
we have microscopes that enable us
to look inside living cells...
303
00:30:13,160 --> 00:30:16,760
..and reveal what's going on
inside them.
304
00:30:17,800 --> 00:30:20,680
Sachs would have been amazed to see
305
00:30:20,680 --> 00:30:25,240
that the chloroplasts
are not sitting in the cells
306
00:30:25,240 --> 00:30:29,640
inactive and static, as they were
on his microscope slide,
307
00:30:29,640 --> 00:30:33,040
but they are jostling for position,
308
00:30:33,040 --> 00:30:36,480
so that the production of starch
is maximised
309
00:30:36,480 --> 00:30:38,560
as the light changes.
310
00:30:38,560 --> 00:30:42,800
It's the most amazingly efficient
production system in nature.
311
00:30:44,560 --> 00:30:48,480
As sunlight hits a leaf,
the chloroplasts leap into action.
312
00:30:49,560 --> 00:30:53,360
When this short clip is repeated
and speeded up,
313
00:30:53,360 --> 00:30:58,640
we can see these chloroplasts
vying with each other
to grab the sun's rays.
314
00:31:00,720 --> 00:31:07,440
This wonderful dance
of the chloroplasts
is going on all around us
315
00:31:07,440 --> 00:31:10,240
in what seem like static leaves
316
00:31:10,240 --> 00:31:16,720
and the plant is doing it
to ensure that it captures
just the right amount of light -
317
00:31:16,720 --> 00:31:19,640
not too little and not too much.
318
00:31:21,640 --> 00:31:26,600
It would have been wonderful
to be able to show this to Sachs,
319
00:31:26,600 --> 00:31:30,720
so that he could see that
the chloroplasts that he observed...
320
00:31:31,800 --> 00:31:36,720
..are moving
in this quite beautiful way.
321
00:31:38,840 --> 00:31:43,000
Plants produce sugars which
they store in the form of starch.
322
00:31:43,000 --> 00:31:46,960
Sachs shows where in the plant
this happens,
323
00:31:46,960 --> 00:31:49,640
how in fact a plant grows.
324
00:31:51,760 --> 00:31:57,560
Sachs would have been astonished
to see what happens
inside this potato cell.
325
00:31:58,600 --> 00:32:02,200
To begin with,
there's no sign of starch.
326
00:32:03,800 --> 00:32:09,720
Yet just after a few hours sitting
in the sunlight, the cell
is packed full of starch grains.
327
00:32:15,400 --> 00:32:22,920
In just over 200 years, the pioneers
of botany have cracked some of
the big questions of photosynthesis.
328
00:32:25,920 --> 00:32:28,720
They knew that plants
don't eat soil,
329
00:32:28,720 --> 00:32:31,360
water and sunlight drive growth.
330
00:32:31,360 --> 00:32:37,040
They had also worked out
that leaves give off a gas
when exposed to the sun.
331
00:32:37,040 --> 00:32:39,640
That gas is oxygen.
332
00:32:42,400 --> 00:32:48,600
And thanks to a devastatingly simple
experiment, they knew that plants
use sunlight to produce sugars,
333
00:32:48,600 --> 00:32:52,000
a source of energy
that gets stored as starch.
334
00:32:54,720 --> 00:33:00,480
All in all,
a pretty impressive body of work
for the fledgling science of botany.
335
00:33:00,480 --> 00:33:03,000
There is still something missing.
336
00:33:03,000 --> 00:33:06,320
Without it,
photosynthesis is impossible.
337
00:33:06,320 --> 00:33:09,040
And it's in the very air we breathe.
338
00:33:10,480 --> 00:33:12,600
Carbon dioxide.
339
00:33:12,600 --> 00:33:16,920
When botanists used microscopes
to examine the surface of leaves...
340
00:33:18,040 --> 00:33:22,280
..they discovered
something rather surprising.
341
00:33:26,720 --> 00:33:31,840
The underside of a leaf is covered
with what looks like tiny pores.
342
00:33:31,840 --> 00:33:36,040
Modern microscopes show these
in amazing detail.
343
00:33:37,920 --> 00:33:41,960
They're called stomata and
it's through these tiny openings
344
00:33:41,960 --> 00:33:46,280
that plants take in carbon dioxide
from the air around them.
345
00:33:48,680 --> 00:33:51,440
These stomata can open and close,
346
00:33:51,440 --> 00:33:57,280
thereby constantly regulating
the amount of carbon dioxide
getting into the plant.
347
00:34:03,120 --> 00:34:08,760
I'd like to think that a breath
I exhaled 30 years ago now exists
in the bark of this tree.
348
00:34:11,320 --> 00:34:13,680
There is a direct link
349
00:34:13,680 --> 00:34:17,280
between our lives
and the lives of plants.
350
00:34:18,840 --> 00:34:23,000
We give plants carbon dioxide
to fuel their growth...
351
00:34:24,120 --> 00:34:28,040
..and they give us the oxygen
we need to survive.
352
00:34:30,160 --> 00:34:35,000
Botanists in the 19th century knew
that plants absorbed carbon dioxide.
353
00:34:35,000 --> 00:34:41,960
It wasn't until well into
the 20th century that they found out
what the plant did with it.
354
00:34:41,960 --> 00:34:47,440
It's the last major piece in the
photosynthesis puzzle to be solved.
355
00:35:09,360 --> 00:35:13,240
Take a look at this photograph
from the 1940s.
356
00:35:13,240 --> 00:35:19,040
It shows two men examining a camera,
both of them scientists
at the top of their game,
357
00:35:19,040 --> 00:35:21,920
nothing unusual in it at all.
358
00:35:21,920 --> 00:35:26,600
Except behind this photograph
is a story of betrayal
359
00:35:26,600 --> 00:35:31,320
and a bitter feud
that would last for four decades.
360
00:35:33,360 --> 00:35:36,600
'The man in the white shirt
is Andrew Benson.
361
00:35:38,600 --> 00:35:44,600
'Benson is responsible for one
of the most important discoveries
in the story of photosynthesis.
362
00:35:44,600 --> 00:35:47,600
'His boss is Melvin Calvin,
363
00:35:47,600 --> 00:35:49,920
'a brilliant chemist.
364
00:35:51,000 --> 00:35:55,760
'Both men are working
at the University of California
at Berkeley.
365
00:35:56,880 --> 00:36:00,720
'Their research is focused
on one question -
366
00:36:00,720 --> 00:36:04,800
'what does a plant do
with carbon dioxide?
367
00:36:09,920 --> 00:36:15,200
'Professor David Beerling's
working life is devoted
to the science of plants.
368
00:36:17,760 --> 00:36:22,160
'For him, the meeting
of Calvin and Benson is pivotal
369
00:36:22,160 --> 00:36:25,120
'to the understanding
of photosynthesis.'
370
00:36:26,160 --> 00:36:29,960
So what do we know
about these two men?
371
00:36:29,960 --> 00:36:34,640
Benson was really following his own
intuition and experimental programme
372
00:36:34,640 --> 00:36:39,120
and much of the work that he did
Calvin was unaware of.
373
00:36:39,120 --> 00:36:44,600
Calvin had a lot going on and he was
involved in running this lab
and other research questions.
374
00:36:44,600 --> 00:36:48,880
He also had his own personal theory
about how photosynthesis was working
375
00:36:48,880 --> 00:36:54,040
and he was very focused on addressing
his own particular pet theory,
376
00:36:54,040 --> 00:36:59,040
and all the time
you've got Benson looking on
and seeing his boss pursuing
377
00:36:59,040 --> 00:37:02,680
what he knew to be,
you know, a dead end.
378
00:37:02,680 --> 00:37:08,320
That's not a great basis
for a working relationship. Rivals
in the same team, no, not at all.
379
00:37:10,840 --> 00:37:14,320
To begin with,
things are very different.
380
00:37:14,320 --> 00:37:17,400
Calvin and Benson work
closely together,
381
00:37:17,400 --> 00:37:22,120
trying to figure out how plants use
carbon dioxide to fuel their growth.
382
00:37:25,600 --> 00:37:29,680
Once again, botany benefits
from a leap forward in science.
383
00:37:31,840 --> 00:37:37,760
Foremost among the new technologies
of the age is a machine
called a cyclotron.
384
00:37:37,760 --> 00:37:41,040
Invented at the Berkeley
Radiation Laboratory,
385
00:37:41,040 --> 00:37:43,960
the cyclotron is
a particle accelerator.
386
00:37:43,960 --> 00:37:48,240
It allows scientists to study
the nucleus of the atom.
387
00:37:48,240 --> 00:37:50,560
CLICKING SOUNDS
388
00:37:50,560 --> 00:37:54,280
But that's not
why it interests Benson.
389
00:37:54,280 --> 00:37:58,360
The cyclotron produces
radioactive carbon atoms.
390
00:38:00,360 --> 00:38:02,600
'The Atomic Age.
391
00:38:02,600 --> 00:38:07,320
'Here is the answer to a dream
as old as Man himself,
392
00:38:07,320 --> 00:38:11,280
'a giant of limitless power
at Man's command.
393
00:38:11,280 --> 00:38:14,320
'And where was it science found
that giant?
394
00:38:14,320 --> 00:38:16,320
'In the atom.'
395
00:38:18,440 --> 00:38:23,160
If the atom is radioactive,
you can follow it wherever it goes.
396
00:38:27,600 --> 00:38:32,200
The idea is to replace the normal
carbon atom in carbon dioxide
397
00:38:32,200 --> 00:38:34,640
with a radioactive carbon atom.
398
00:38:35,840 --> 00:38:40,760
By making
the carbon dioxide radioactive
before a plant takes it in,
399
00:38:40,760 --> 00:38:45,680
Benson believes he can track
carbon's journey through the plant.
400
00:38:48,680 --> 00:38:54,000
If this works,
Benson will have discovered
how a plant uses carbon dioxide,
401
00:38:54,000 --> 00:38:57,040
something no-one else
has done before.
402
00:38:57,040 --> 00:39:01,040
For a scientist, it doesn't get
any more exciting than this.
403
00:39:16,440 --> 00:39:21,440
At the heart of the experiment is
a glass disc shaped like a lollipop.
404
00:39:21,440 --> 00:39:27,320
It contains green algae
growing in conditions
that are perfect for photosynthesis.
405
00:39:30,320 --> 00:39:34,760
Inside his disc were algae
busily photosynthesising away.
406
00:39:34,760 --> 00:39:38,520
When he introduced
the radioactive carbon dioxide,
407
00:39:38,520 --> 00:39:41,120
the algae absorbed the gas.
408
00:39:41,120 --> 00:39:46,760
He then killed the algae
and the chemical reactions
stopped instantly.
409
00:39:48,040 --> 00:39:53,080
'By killing the algae with alcohol,
Benson freezes a moment in time.
410
00:39:53,080 --> 00:40:00,440
'He then examines the dead algae
to see how they've used the carbon
in carbon dioxide to make sugars.
411
00:40:04,680 --> 00:40:09,760
'The radioactive compounds
in the algae are separated
on to sheets of paper.
412
00:40:10,880 --> 00:40:15,160
'These sheets are then pressed
against X-ray sensitive film
413
00:40:15,160 --> 00:40:18,600
'to produce something
called a chromatogram.
414
00:40:20,160 --> 00:40:24,680
'Each fuzzy blob here shows where
the radioactive carbon has gone.'
415
00:40:26,800 --> 00:40:30,240
Why did a few smudges create
so much excitement?
416
00:40:30,240 --> 00:40:32,840
This doesn't look very impressive,
417
00:40:32,840 --> 00:40:39,000
but this must have been their Eureka
moment when they started getting
these chromatograms. Really? Why?
418
00:40:39,000 --> 00:40:43,880
Because they realised that they could
now see some of the key compounds
419
00:40:43,880 --> 00:40:50,440
that had used the radioactive carbon
they'd fed the algae. So each blob
is a different molecule?
420
00:40:50,440 --> 00:40:55,720
Each of these smudges represents
a different chemical compound
or a different sugar
421
00:40:55,720 --> 00:40:59,360
that represents a different stage
in the pathway to carbon.
422
00:41:03,160 --> 00:41:06,760
'The pathway to carbon
is effectively a road map,
423
00:41:06,760 --> 00:41:09,840
'showing how the plant makes sugar.
424
00:41:10,920 --> 00:41:15,360
'Understanding the first step
on that road is crucial -
425
00:41:15,360 --> 00:41:19,440
'how a plant splits carbon
from carbon dioxide.
426
00:41:19,440 --> 00:41:24,960
'Benson believes the answer lies
with a protein
that is common to all plants.
427
00:41:26,360 --> 00:41:32,680
'Calvin, on the other hand, has
his own grand theory and isn't much
interested in what Benson is up to.
428
00:41:36,160 --> 00:41:40,400
'So to begin with, Benson doesn't
tell his boss what he's doing.
429
00:41:42,840 --> 00:41:47,680
'Calvin's theory of photosynthesis
is eventually proved wrong.
430
00:41:50,320 --> 00:41:53,160
'Benson is the one
who gets it right.
431
00:41:53,160 --> 00:41:57,640
'It's Benson who shows what happens
during that first crucial step
432
00:41:57,640 --> 00:42:01,560
'when a plant grabs hold
of the carbon in carbon dioxide.'
433
00:42:03,120 --> 00:42:07,760
Photosynthesis is often shown as
carbon dioxide plus water and light
434
00:42:07,760 --> 00:42:10,720
equals sugar and oxygen.
435
00:42:10,720 --> 00:42:14,640
This seems to imply
that that's a gross simplification.
436
00:42:14,640 --> 00:42:18,200
Yes, it's accurate,
but it hides a huge amount of detail
437
00:42:18,200 --> 00:42:21,760
and a huge amount of elegance
in the biochemistry.
438
00:42:21,760 --> 00:42:26,560
So it's not one big step, it's lots
of tiny little hops? That's right.
439
00:42:26,560 --> 00:42:30,880
'Mother Nature doesn't give up
her secrets that easily.
440
00:42:32,520 --> 00:42:35,280
'Every smudge has to be identified,
441
00:42:35,280 --> 00:42:40,080
'then they need to figure out
how all the compounds work together.
442
00:42:40,080 --> 00:42:44,280
'It's a project
that takes ten years to complete.
443
00:42:48,400 --> 00:42:52,200
'Benson receives no recognition
for his work.'
444
00:42:56,840 --> 00:43:00,680
It's a familiar story.
Someone makes a great discovery...
445
00:43:01,720 --> 00:43:04,240
And someone else takes the credit.
446
00:43:07,320 --> 00:43:11,360
In 1954, Benson is sacked
from the university,
447
00:43:11,360 --> 00:43:14,720
leaving Calvin to work on
without him.
448
00:43:19,840 --> 00:43:22,920
I want to show you another photo.
449
00:43:22,920 --> 00:43:27,440
It's 1961 and Melvin Calvin
is receiving his Nobel Prize
450
00:43:27,440 --> 00:43:31,120
for cracking the role of carbon
in photosynthesis,
451
00:43:31,120 --> 00:43:34,280
but there's something
or someone missing.
452
00:43:36,760 --> 00:43:39,760
Andrew Benson is nowhere
to be seen.
453
00:43:44,160 --> 00:43:48,480
To begin with, both men are credited
for their work on photosynthesis.
454
00:43:51,720 --> 00:43:55,200
Now only one name takes
centre stage.
455
00:44:01,480 --> 00:44:06,760
The passing of the years did little
to soften Calvin's approach
to his colleague.
456
00:44:08,840 --> 00:44:13,360
This is Melvin Calvin's
autobiography and it tells a story
457
00:44:13,360 --> 00:44:18,160
of how he and his team unlocked
the secrets of photosynthesis.
458
00:44:18,160 --> 00:44:22,600
It was published 30 years after
he was awarded the Nobel Prize
459
00:44:22,600 --> 00:44:25,720
and in all 175 pages,
460
00:44:25,720 --> 00:44:29,520
there is no mention
of Andrew Benson. Not once.
461
00:44:29,520 --> 00:44:32,200
It's as though he never existed.
462
00:44:38,280 --> 00:44:43,520
'Carbon's journey from gas to sugar
became known as "the Calvin cycle".
463
00:44:45,600 --> 00:44:49,960
'Today, many botanists recognise
Benson's contribution
464
00:44:49,960 --> 00:44:53,080
'and call it
"the Calvin-Benson cycle".
465
00:44:58,880 --> 00:45:04,840
'Benson may have missed out
on the Nobel Prize, but his
contribution hasn't been forgotten.'
466
00:45:04,840 --> 00:45:07,880
So how important is Benson's work?
467
00:45:07,880 --> 00:45:13,200
Andy Benson's discoveries
were absolutely amazing.
468
00:45:13,200 --> 00:45:18,520
They filled a huge gap
in our knowledge
about how plants photosynthesise
469
00:45:18,520 --> 00:45:22,600
and in a sense the discovery
of that pathway of how they do that
470
00:45:22,600 --> 00:45:26,560
is comparable to Watson and Crick
figuring out the structure of DNA.
471
00:45:30,160 --> 00:45:33,600
Today, we not only know
how plants grow,
472
00:45:33,600 --> 00:45:38,680
but with the latest technology,
we can watch them grow,
cell by cell.
473
00:45:40,720 --> 00:45:45,760
The tip of this root is forcing
its way through the earth.
474
00:45:45,760 --> 00:45:50,520
By taking carbon dioxide
and converting it
into sugars and starch,
475
00:45:50,520 --> 00:45:54,080
the plant has the energy
it needs to grow.
476
00:46:06,200 --> 00:46:11,560
It may seem like we now know
everything there is to know
about photosynthesis...
477
00:46:12,680 --> 00:46:15,080
..but that's not the case.
478
00:46:16,360 --> 00:46:22,240
For instance, the environment
in which plants grow can vary
dramatically and yet they survive.
479
00:46:26,280 --> 00:46:29,120
Plants are very sophisticated.
480
00:46:29,120 --> 00:46:35,640
From the Equator to the Arctic
Circle, they photosynthesise
in all sorts of conditions.
481
00:46:35,640 --> 00:46:39,960
And they have to respond to
their environment in order to grow.
482
00:46:39,960 --> 00:46:44,400
And even here in Britain,
plants have a lot to contend with.
483
00:46:50,200 --> 00:46:52,880
Whether they live high on a hill top
484
00:46:52,880 --> 00:46:55,600
or down on the valley floor,
485
00:46:55,600 --> 00:46:58,960
plants have adapted
to where they live.
486
00:46:58,960 --> 00:47:01,600
Take this ivy, for example.
487
00:47:01,600 --> 00:47:05,640
It's growing on a north-facing cliff
so it gets no direct sunshine.
488
00:47:05,640 --> 00:47:09,760
Furthermore, it's got trees forming
a canopy over the top of it.
489
00:47:09,760 --> 00:47:16,040
It's got no real soil to get
its roots into, so it has
no permanent supply of water
490
00:47:16,040 --> 00:47:21,400
and yet there's lots of it.
It is brilliantly adapted
to these growing conditions.
491
00:47:28,120 --> 00:47:31,960
Whether it's poor light
or not enough soil,
492
00:47:31,960 --> 00:47:35,840
plants have to make the most
of their surroundings.
493
00:47:35,840 --> 00:47:39,560
That's because, unlike me,
they're rooted to the spot.
494
00:47:40,640 --> 00:47:44,440
They can't go searching for water
if they're thirsty
495
00:47:44,440 --> 00:47:47,360
or find a shady spot
to hide from the sun.
496
00:47:48,520 --> 00:47:53,400
Up on the top of the hill,
there's plenty of light.
That's not a problem.
497
00:47:53,400 --> 00:47:56,440
Here, it's the wind
drying out the plants
498
00:47:56,440 --> 00:48:00,280
that makes water the limiting factor
for photosynthesis.
499
00:48:06,320 --> 00:48:09,160
Plants either adapt or die,
500
00:48:09,160 --> 00:48:12,920
so they've come up with clever ways
to survive.
501
00:48:14,000 --> 00:48:18,760
And we've developed methods to turn
this ability to our advantage.
502
00:48:19,920 --> 00:48:26,560
Farmers have learned how to make
the most of photosynthesis
in all sorts of conditions
503
00:48:26,560 --> 00:48:32,720
and in modern glasshouses,
they can manipulate the environment
to increase production,
504
00:48:32,720 --> 00:48:36,200
often in ways
that are quite surprising.
505
00:48:38,200 --> 00:48:40,520
SHEEP BLEATING
506
00:48:42,280 --> 00:48:46,880
The Netherlands is one
of the world's smallest countries,
507
00:48:46,880 --> 00:48:50,840
yet it has become one of
the world's biggest food exporters.
508
00:48:53,920 --> 00:48:56,440
In these vast greenhouses,
509
00:48:56,440 --> 00:49:01,920
commercial growers have learned
to manipulate the building blocks
of photosynthesis.
510
00:49:04,160 --> 00:49:07,640
They don't rely on sunlight
to grow crops.
511
00:49:09,960 --> 00:49:14,000
They can make their own
with the help of 3,500 light bulbs.
512
00:49:17,360 --> 00:49:23,160
When the sun goes down,
the lights come on
and the plants continue to grow.
513
00:49:25,080 --> 00:49:27,560
By changing the lighting conditions,
514
00:49:27,560 --> 00:49:33,120
they can bring forward
the growing season of these peppers
by four weeks.
515
00:49:34,600 --> 00:49:39,320
More light buys the plant more time
to turn sugar into fruit.
516
00:49:44,320 --> 00:49:50,800
With sunlight guaranteed,
this greenhouse produces
14 million peppers every year.
517
00:49:53,960 --> 00:49:59,960
Sunlight isn't the only part
of photosynthesis that can be
manipulated to our advantage.
518
00:49:59,960 --> 00:50:02,240
Thanks to a quirk of evolution,
519
00:50:02,240 --> 00:50:07,640
changing the levels
of carbon dioxide can also have
a dramatic effect.
520
00:50:07,640 --> 00:50:11,840
There have been times
in the history of the Earth
521
00:50:11,840 --> 00:50:15,880
when the carbon dioxide levels
were very different
522
00:50:15,880 --> 00:50:22,360
and as a result, plants have
the capacity to use extra
carbon dioxide to make more sugar
523
00:50:22,360 --> 00:50:24,440
and to produce bigger fruit.
524
00:50:30,080 --> 00:50:35,960
Commercial growers have been quick
to exploit this legacy
of our planet's past.
525
00:50:38,120 --> 00:50:44,080
Today, this Suffolk greenhouse
produces 50% of all the tomatoes
grown in Britain.
526
00:50:47,200 --> 00:50:51,160
The secret to more tomatoes
is more carbon dioxide.
527
00:50:55,280 --> 00:50:59,040
Next door to the greenhouse
is this factory.
528
00:50:59,040 --> 00:51:01,480
It generates two waste products.
529
00:51:01,480 --> 00:51:05,360
One is steam
which escapes up these chimneys
530
00:51:05,360 --> 00:51:08,280
and the other is carbon dioxide,
531
00:51:08,280 --> 00:51:12,720
a greenhouse gas that you don't want
to release into the atmosphere.
532
00:51:14,680 --> 00:51:20,840
So instead, this greenhouse gas
gets pumped from the factory
into...a greenhouse.
533
00:51:23,080 --> 00:51:26,360
These plastic tubes have tiny holes
534
00:51:26,360 --> 00:51:30,640
which deliver the gas to the leaves
of the tomato plants.
535
00:51:35,040 --> 00:51:39,720
Give a tomato plant extra carbon
dioxide and it produces more sugar
536
00:51:39,720 --> 00:51:44,000
which makes for a sweeter tomato
which is good for us.
537
00:51:44,000 --> 00:51:46,280
It also doubles the yield
538
00:51:46,280 --> 00:51:49,160
which is good for the grower.
539
00:51:50,320 --> 00:51:53,720
By fine-tuning the environment
of plants,
540
00:51:53,720 --> 00:51:55,800
we can grow more food.
541
00:51:59,320 --> 00:52:04,880
These commercial growers have got
photosynthesis down to a fine art.
542
00:52:04,880 --> 00:52:08,680
They can manipulate it,
but that's as far as it goes.
543
00:52:08,680 --> 00:52:12,040
Plants are still doing
all the hard work.
544
00:52:19,080 --> 00:52:25,640
Turning water and carbon dioxide
into leaves, seeds and fruits
makes huge demands on a plant.
545
00:52:27,360 --> 00:52:31,360
To fuel this growth,
it needs a reliable source of power.
546
00:52:32,480 --> 00:52:36,440
However different they are,
wherever they come from,
547
00:52:36,440 --> 00:52:43,040
plants are all able to survive
and grow because of their ability
to harness energy from the sun.
548
00:52:49,560 --> 00:52:54,360
The amount of light energy converted
by photosynthesis is staggering.
549
00:52:57,160 --> 00:53:01,640
In one year, all the plants
on Earth generate enough energy
550
00:53:01,640 --> 00:53:04,640
to power human civilisation
six times over.
551
00:53:06,720 --> 00:53:10,960
We now know a great deal
about photosynthesis.
552
00:53:10,960 --> 00:53:15,360
We can manipulate it to make
better crops and feed more people.
553
00:53:15,360 --> 00:53:20,040
But this is just the start.
The next step is really exciting.
554
00:53:20,040 --> 00:53:27,120
And if science gets it right,
it will alter lives
for generations to come.
555
00:53:39,760 --> 00:53:43,880
At the University of Glasgow,
Professor Lee Cronin is trying
556
00:53:43,880 --> 00:53:48,160
to recreate photosynthesis
in his laboratory.
557
00:53:48,160 --> 00:53:53,440
Something that plants
have been doing for more
than a thousand million years,
558
00:53:53,440 --> 00:53:56,680
he is trying to do artificially
in a decade.
559
00:53:59,640 --> 00:54:04,200
Plants use the sun's energy to split
water into hydrogen and oxygen,
560
00:54:04,200 --> 00:54:08,320
two gases that could help make
the fuels of the future.
561
00:54:09,800 --> 00:54:13,920
It's this process
that Lee is trying to copy.
562
00:54:15,920 --> 00:54:19,920
This very thin electrode where
you see all these very small bubbles
563
00:54:19,920 --> 00:54:23,520
is a platinum electrode
where the hydrogen is coming off,
564
00:54:23,520 --> 00:54:29,160
and at this black electrode with
the slightly bigger bubble is where
the oxygen is being produced.
565
00:54:29,160 --> 00:54:35,080
This normally happens inside
a leaf, but here it's happening
in this flask. Exactly.
566
00:54:35,080 --> 00:54:37,440
'There's still a long way to go.
567
00:54:38,520 --> 00:54:41,720
'Lee can't split water
using just light.
568
00:54:41,720 --> 00:54:43,760
'Not yet anyway.
569
00:54:43,760 --> 00:54:47,040
'He still needs a battery
to power the process,
570
00:54:47,040 --> 00:54:49,560
'but the potential is enormous.'
571
00:54:49,560 --> 00:54:56,120
If we let this go long enough, the
water in here would get less and less
as it's being converted to the gas
572
00:54:56,120 --> 00:55:00,200
and there'd be nothing left at
the end. How long would that take?
573
00:55:00,200 --> 00:55:06,200
Probably... Well, at this rate,
probably a few days. Right.
So we don't need very much water.
574
00:55:06,200 --> 00:55:09,280
There's a huge amount of gas
locked up in here.
575
00:55:09,280 --> 00:55:15,040
But this is the critical first step
of the photosynthesis story?
Yeah, exactly.
576
00:55:15,040 --> 00:55:18,560
Once we've perfected the first step,
there is a critical part
577
00:55:18,560 --> 00:55:24,400
where we take carbon dioxide from
the atmosphere and complete the story
and turn the carbon dioxide
578
00:55:24,400 --> 00:55:28,000
into a fuel that we could put
in an aeroplane or a car.
579
00:55:28,000 --> 00:55:34,680
So our family cars could start,
in years to come, from a process
like this with water being split?
580
00:55:34,680 --> 00:55:38,640
There's every possibility.
We're very excited about it. Wow!
581
00:55:38,640 --> 00:55:43,160
'So he should be. The prize
is clean and limitless energy.
582
00:55:43,160 --> 00:55:48,800
'No wonder labs like this
all over the world are working hard
to crack the problem.'
583
00:55:48,800 --> 00:55:55,320
If we get this right, if we're able
to understand and learn
from photosynthesis in such a way
584
00:55:55,320 --> 00:56:00,200
that we can surpass evolution if you
like and make an even better device
585
00:56:00,200 --> 00:56:05,520
to take light energy, carbon dioxide
and water and produce a fuel,
586
00:56:05,520 --> 00:56:10,920
then this is going to have
massive ramifications
for our society and our environment.
587
00:56:24,880 --> 00:56:27,400
Lee's work is impressive,
588
00:56:27,400 --> 00:56:31,280
but it shows how sophisticated
photosynthesis is
589
00:56:31,280 --> 00:56:34,760
and scientists will be hard pressed
to replicate it.
590
00:56:34,760 --> 00:56:38,800
The thought that it may provide
an alternative source of energy
591
00:56:38,800 --> 00:56:42,120
confirms the awesome power
of photosynthesis.
592
00:56:44,880 --> 00:56:50,760
To see the power of photosynthesis
in action, take a look
at these images from NASA.
593
00:56:50,760 --> 00:56:55,040
They show how photosynthesis varies
across the globe
594
00:56:55,040 --> 00:56:58,160
with the ebb and flow
of the seasons.
595
00:56:58,160 --> 00:57:00,640
That's not the whole story.
596
00:57:00,640 --> 00:57:03,440
What's fascinating is the oceans.
597
00:57:04,760 --> 00:57:07,480
They're glowing green.
598
00:57:07,480 --> 00:57:14,040
That's because half of the world's
photosynthesis takes place
not on the land, but in the sea.
599
00:57:16,520 --> 00:57:21,480
How close are we to understanding
all there is to know
about photosynthesis?
600
00:57:21,480 --> 00:57:28,080
We understand the broad principles
of how photosynthesis works, but
the real fine detail still eludes us.
601
00:57:28,080 --> 00:57:33,000
We can put a man on the moon,
but we can't mimic photosynthesis.
602
00:57:40,600 --> 00:57:46,200
Botany has come a long way
since the time when people believed
plants eat soil.
603
00:57:48,160 --> 00:57:51,720
Today, we can feed more
of the world's population.
604
00:57:51,720 --> 00:57:56,080
Tomorrow, we may even find a way
to fuel our planet.
605
00:57:58,120 --> 00:58:00,640
And it's all down to photosynthesis,
606
00:58:00,640 --> 00:58:05,240
for me, the most remarkable
and important process on Earth.
607
00:58:06,800 --> 00:58:09,680
Next time on
Botany: A Blooming History...
608
00:58:10,840 --> 00:58:16,400
I'll be looking at how botanists
puzzled over the colours
of snapdragons,
609
00:58:16,400 --> 00:58:20,240
investigated the mysteries
of wild maize
610
00:58:20,240 --> 00:58:24,600
and developed a brand-new science -
plant genetics.
611
00:58:45,920 --> 00:58:49,920
Subtitles by Subtext
for Red Bee Media Ltd 2011
612
00:58:49,920 --> 00:58:52,920
Email subtitling@bbc.co.uk
59189
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