1
00:00:06,000 --> 00:00:12,074
Advertise your product or brand here
contact www.OpenSubtitles.org today

2
00:00:54,326 --> 00:00:57,875
The Great Barrier Reef, Australia. At night.

3
00:00:58,766 --> 00:01:01,121
I'm surrounded by corals.

4
00:01:04,726 --> 00:01:08,002
They do look extraordinarily like plants,

5
00:01:08,166 --> 00:01:12,444
branching into fans and twigs and bushes.

6
00:01:13,926 --> 00:01:17,123
At night, the similarity is particularly marked.

7
00:01:17,286 --> 00:01:23,725
All over their stony surface,
tiny buds open into what look like flowers.

8
00:01:45,086 --> 00:01:50,365
But these little structures
don't behave in a flower-like way.

9
00:01:51,086 --> 00:01:58,481
They seize and eat any edible particle
that drifts by, they are clearly animals.

10
00:01:59,206 --> 00:02:03,040
But even so, they look like plants. Why?

11
00:02:06,246 --> 00:02:11,525
It was only comparatively recently
that we understood the answer in full detail.

12
00:02:11,686 --> 00:02:14,883
And it only becomes evident
when the sun comes up,

13
00:02:15,046 --> 00:02:19,198
for then the corals
change their behaviour in a radical way.

14
00:02:33,646 --> 00:02:36,240
Corals, like plants, must have light.

15
00:02:36,406 --> 00:02:38,874
They can't grow if the water is cloudy,

16
00:02:39,046 --> 00:02:43,278
or the depths so great
that the rays of the sun can't reach it.

17
00:02:43,446 --> 00:02:47,325
And these resemblances
are not just coincidences.

18
00:02:47,486 --> 00:02:51,604
If I go back underwater
now that it's day and the sun is up,

19
00:02:51,766 --> 00:02:56,999
I'll see that many of these corals are feeding
in a way that is not like animals at all,

20
00:02:57,166 --> 00:02:59,555
a way that is quite different.

21
00:03:10,206 --> 00:03:14,484
Now the plant-like form of the coral
is even more obvious.

22
00:03:14,646 --> 00:03:16,796
The tiny rosettes of groping arms

23
00:03:16,966 --> 00:03:21,835
have withdrawn into their stony sockets
on the surface of the coral skeleton.

24
00:03:22,006 --> 00:03:25,078
But they're still within the reach of sunlight.

25
00:03:26,806 --> 00:03:32,403
And within their tiny bodies
are microscopic green plants, algae,

26
00:03:32,566 --> 00:03:36,684
and they're feeding
by making starches and sugars.

27
00:03:40,526 --> 00:03:42,562
But the corals are feeding, too.

28
00:03:42,726 --> 00:03:46,514
They have partly digested the walls
of these captive plants,

29
00:03:46,686 --> 00:03:52,875
and 80% of the food the algae make
leaks out of them and is consumed by the coral.

30
00:03:53,046 --> 00:03:58,962
Having dined on meat all night,
the corals are now getting their vegetables.

31
00:04:01,046 --> 00:04:05,483
The corals provide their internal gardens
with the best possible light

32
00:04:05,646 --> 00:04:07,557
by growing into these shapes.

33
00:04:07,726 --> 00:04:12,163
Which is just what bushes do
for their food factories, their leaves,

34
00:04:12,326 --> 00:04:15,124
when they grow in the same way.

35
00:04:16,126 --> 00:04:19,721
The coral algae do get some benefit
from this arrangement.

36
00:04:19,886 --> 00:04:25,324
These glassy waters are very poor
in nitrates and phosphates, which algae need.

37
00:04:26,006 --> 00:04:29,919
Those substances, however,
are in the coral's waste products.

38
00:04:30,086 --> 00:04:35,843
So the algae, safe inside these rocky skeletons,
can absorb their fertiliser directly,

39
00:04:36,006 --> 00:04:39,715
and live in waters
that otherwise could not support them.

40
00:04:42,006 --> 00:04:46,921
Other animals on the reef
also cultivate similar gardens.

41
00:04:50,086 --> 00:04:53,795
Giant clams keep their algae
not inside their cells,

42
00:04:53,966 --> 00:05:00,485
but in special compartments just beneath the
surface of the mantle that form long, brown lines.

43
00:05:01,486 --> 00:05:06,002
To give them the light they need,
the clam has to open its shell wide,

44
00:05:06,166 --> 00:05:08,282
so exposing itself to danger.

45
00:05:08,446 --> 00:05:11,085
But the blue spots are sensitive to light,

46
00:05:11,246 --> 00:05:17,037
and warn it of any unexpected shadows
that might indicate an approaching threat.

47
00:05:19,446 --> 00:05:23,678
A few jellyfish maintain algal populations as well.

48
00:05:23,846 --> 00:05:27,122
These, in a lake on the Pacific island of Palau,

49
00:05:27,286 --> 00:05:30,835
pamper theirs in an extraordinary way.

50
00:05:35,366 --> 00:05:39,484
This lake is cut off from the sea
by ramparts of coral limestone,

51
00:05:39,646 --> 00:05:41,762
and there are very few fish here.

52
00:05:41,926 --> 00:05:47,046
So these jellyfish can't live, like most
of their relations, by catching animal prey,

53
00:05:47,206 --> 00:05:50,755
and their tentacles
no longer carry stings for hunting.

54
00:05:50,926 --> 00:05:56,205
Instead, they have been converted
into allotments for algae.

55
00:06:03,126 --> 00:06:07,677
The lake is surrounded by a tall forest
growing on the limestone wall.

56
00:06:07,846 --> 00:06:13,557
The sun doesn't rise above the trees
until several hours after dawn.

57
00:06:16,566 --> 00:06:20,718
But at last its rays strike the water
at one end of the lake.

58
00:06:20,886 --> 00:06:27,234
And there, several million jellyfish
have assembled, awaiting the sunlight.

59
00:06:30,926 --> 00:06:33,235
As the sun moves across the sky,

60
00:06:33,406 --> 00:06:38,434
so the vast fleet travels slowly
towards the other side of the lake,

61
00:06:38,606 --> 00:06:41,962
keeping always in the sunshine.

62
00:06:43,166 --> 00:06:46,841
So reluctant are the jellyfish to leave the light

63
00:06:47,006 --> 00:06:52,285
that, on the edge of the shadow,
they crowd together in a tightly-packed shoal.

64
00:07:08,526 --> 00:07:12,724
But without stings, the jellyfish are defenceless.

65
00:07:12,886 --> 00:07:16,561
Now, if they blunder
into the arms of a sea anemone,

66
00:07:16,726 --> 00:07:20,036
they have no way of repelling the tentacles.

67
00:07:20,206 --> 00:07:21,924
They're eaten.

68
00:07:37,646 --> 00:07:40,080
The daytime voyage across the lake

69
00:07:40,246 --> 00:07:44,478
is not the only action the jellyfish take
to nurture their algae.

70
00:07:44,646 --> 00:07:48,355
Come the evening,
they swim down to the bottom.

71
00:07:48,526 --> 00:07:52,997
There, the water is murky
with decaying vegetable matter and sludge.

72
00:07:53,166 --> 00:07:58,320
And there, during the night,
the algae absorb the fertiliser they need.

73
00:08:04,446 --> 00:08:08,564
That animals should sometimes kidnap plants
is not surprising.

74
00:08:08,726 --> 00:08:14,596
All animals, including ourselves, have always
exploited plants in one way or another,

75
00:08:14,766 --> 00:08:17,439
directly or indirectly.

76
00:08:17,606 --> 00:08:21,963
Perhaps it's more surprising
that sometimes it's the other way round.

77
00:08:22,126 --> 00:08:27,484
Sometimes it's plants that keep animals
for the plants' benefit.

78
00:08:28,846 --> 00:08:35,285
Here in the forest of Borneo,
the rattan cane does just that.

79
00:08:35,446 --> 00:08:41,316
No plant benefits from being eaten,
but most can't do much to stop it.

80
00:08:41,486 --> 00:08:45,161
Not so the rattan. Watch and listen.

81
00:08:47,126 --> 00:08:49,037
(THROBBING SOUND )

82
00:08:49,206 --> 00:08:54,997
Out of a nest around the stem of the rattan,
close to its tip, come angry ants.

83
00:09:03,886 --> 00:09:06,525
They're making this throbbing hiss

84
00:09:06,686 --> 00:09:11,043
by banging their heads synchronously
against the rattan's stem.

85
00:09:16,526 --> 00:09:21,805
These ants have a particularly vicious bite,
as I well know. Ow!

86
00:09:22,686 --> 00:09:27,237
I certainly try and keep clear of them
when I'm in the forest,

87
00:09:27,406 --> 00:09:30,637
and I'm quite sure plant-eating animals do, too.

88
00:09:32,246 --> 00:09:39,038
So when I, or they, hear this alarming noise,
we do our best to steer clear of what's making it,

89
00:09:39,206 --> 00:09:44,644
and the rattan's tip, its most vulnerable part,
remains undamaged.

90
00:09:52,526 --> 00:09:58,795
In Africa, there are a great number
of very determined plant-eaters.

91
00:10:07,006 --> 00:10:12,034
Acacias protect themselves with spines,
but they're by no means a total defence.

92
00:10:12,206 --> 00:10:14,845
Some animals, it's true, are put off by them,

93
00:10:15,006 --> 00:10:19,397
but others, like the giraffe,
seem able to ignore them.

94
00:10:34,046 --> 00:10:38,881
But a few acacias, like the rattan,
have recruited ants as guards,

95
00:10:39,046 --> 00:10:44,325
and provide them with special barracks,
the swollen bases of their thorns.

96
00:10:49,046 --> 00:10:53,676
One nibble from the giraffe
is enough to bring out the defenders.

97
00:11:04,886 --> 00:11:07,559
They attack the animal's tongue and lips.

98
00:11:13,486 --> 00:11:16,558
Eventually, the irritation becomes too much.

99
00:11:16,726 --> 00:11:22,119
Even though there are a lot of good leaves left
on the tree, the giraffe moves away.

100
00:11:26,086 --> 00:11:29,601
Several different acacias
employ ants as defenders.

101
00:11:29,766 --> 00:11:32,155
As well as providing accommodation,

102
00:11:32,326 --> 00:11:35,875
the trees pay their security staff
with a sugary nectar

103
00:11:36,046 --> 00:11:40,676
that wells up from little glands on their stems.

104
00:11:48,166 --> 00:11:53,035
This South American species
rewards its ants even more extravagantly.

105
00:11:53,206 --> 00:11:57,597
It not only produces nectar for them,
but packets of protein,

106
00:11:57,766 --> 00:12:01,042
little beads that grow on the tip of its leaflets.

107
00:12:06,846 --> 00:12:09,235
But these are not for the adults.

108
00:12:09,406 --> 00:12:14,321
They're special baby food
which the workers take back to their larvae.

109
00:12:24,006 --> 00:12:28,318
These infants are housed
in the swollen bases of the thorns.

110
00:12:39,286 --> 00:12:45,521
The worker tucks the bead into a special pouch
just beneath the larva's jaws.

111
00:12:53,926 --> 00:13:00,365
Whenever the youngster wants a meal,
it just bends its head down and takes a nibble.

112
00:13:14,046 --> 00:13:17,322
In return for these lavish provisions
and amenities,

113
00:13:17,486 --> 00:13:23,925
the ants mount a very energetic defence
of the acacia, rushing to attack intruders.

114
00:13:26,646 --> 00:13:32,403
Any insect that lands on the tree
hoping to nibble a leaf or two is soon dealt with.

115
00:13:46,966 --> 00:13:51,403
The ants even defend their tree
against rival plants.

116
00:13:51,566 --> 00:13:57,038
Regular patrols go down the trunk and range
for a long way over the surrounding earth.

117
00:14:00,166 --> 00:14:02,634
Seedlings that sprout within this area,

118
00:14:02,806 --> 00:14:07,675
so threatening to take some of the acacia's
sustenance, are severely mauled.

119
00:14:07,846 --> 00:14:13,159
The ants aren't eating this plant,
they're chewing it to death.

120
00:14:17,646 --> 00:14:23,084
The tendrils of any plant that reach over
to climb onto the acacia get similar treatment.

121
00:14:23,246 --> 00:14:27,444
Clearly, it's well worth the acacia's while
to provide food and lodging

122
00:14:27,606 --> 00:14:31,076
for such a valiant and dedicated defence force.

123
00:14:40,006 --> 00:14:43,078
This plant is even more accommodating.

124
00:14:43,246 --> 00:14:49,196
It has inflated most of its stem
into an ant mansion.

125
00:14:55,166 --> 00:14:59,637
It grows in New Guinea,
clinging to the branches of other trees,

126
00:14:59,806 --> 00:15:04,516
and it's called, with good reason, an ant plant.

127
00:15:04,686 --> 00:15:07,519
Ants continually run about on its surface,

128
00:15:07,686 --> 00:15:12,840
on their way to, or returning from,
a hunt for insects.

129
00:15:14,726 --> 00:15:18,685
The accommodation the plant provides
for the ants is spacious

130
00:15:18,846 --> 00:15:22,475
and excellently suited to their requirements.

131
00:15:22,646 --> 00:15:24,637
Immediately within its walls,

132
00:15:24,806 --> 00:15:29,084
a network of corridors ensures
the whole structure is air-conditioned,

133
00:15:29,246 --> 00:15:33,683
an essential for any
well-appointed residence in the tropics.

134
00:15:46,806 --> 00:15:49,878
Farther inside, there are the nurseries,

135
00:15:50,046 --> 00:15:54,437
smooth-walled chambers
where the larvae are reared.

136
00:16:04,206 --> 00:16:07,676
And there are also special refuse tips.

137
00:16:07,846 --> 00:16:11,475
Here the workers dump
the droppings of the colony.

138
00:16:17,486 --> 00:16:21,525
These chambers are not only middens,
they are mortuaries,

139
00:16:21,686 --> 00:16:27,602
the last resting place of members of the colony
that die within the mansion.

140
00:16:36,566 --> 00:16:41,401
The chambers in which these bodies lie
have walls covered with warts.

141
00:16:41,566 --> 00:16:45,115
These absorb nutrients from the rotting piles.

142
00:16:45,286 --> 00:16:48,881
This is how the plant collects its rent.

143
00:16:59,806 --> 00:17:06,359
Fungi may seem unlikely, even dangerous
organisms with which to form a partnership.

144
00:17:06,526 --> 00:17:09,518
After all, they do feed on plants.

145
00:17:11,686 --> 00:17:18,034
Fungi are neither animals nor plants,
they're fundamentally different from either.

146
00:17:19,086 --> 00:17:24,558
They can dissolve all kinds of substances,
rock, metal, even plastic.

147
00:17:24,726 --> 00:17:28,639
But most notably,
they consume the bodies of plants,

148
00:17:28,806 --> 00:17:33,084
and these bracket fungi eat trees.

149
00:17:33,246 --> 00:17:38,240
We tend to notice them only when they produce
spectacular structures like these,

150
00:17:38,406 --> 00:17:40,795
their fruiting bodies.

151
00:17:40,966 --> 00:17:45,801
Spores fall from their underside
in astronomical numbers, millions a minute,

152
00:17:45,966 --> 00:17:49,754
so fungal spores exist pretty well everywhere.

153
00:17:52,686 --> 00:17:56,315
They may enter a tree
through a wound in the bark.

154
00:17:56,486 --> 00:18:01,844
They then develop into threads that slowly
move inwards and start to digest the wood.

155
00:18:02,006 --> 00:18:06,955
The tree now, as we would see it,
has a rotten core.

156
00:18:13,086 --> 00:18:16,476
Eventually, after tens or even hundreds of years,

157
00:18:16,646 --> 00:18:21,276
a tree may have its interior completely eaten
away by the fungal threads,

158
00:18:21,446 --> 00:18:23,277
as has happened to this one.

159
00:18:23,446 --> 00:18:29,282
But that is not as disastrous as you might think,
because the fungus only consumes dead tissue.

160
00:18:29,446 --> 00:18:32,324
It leaves the living tissue completely untouched,

161
00:18:32,486 --> 00:18:37,196
and it survives as a kind of outer cylinder
from which all new growth comes,

162
00:18:37,366 --> 00:18:39,880
and that's all the tree needs.

163
00:18:46,246 --> 00:18:52,845
So, although this 800-year-old oak
in Windsor Great Park

164
00:18:53,006 --> 00:18:56,043
is completely hollow, it's still thriving.

165
00:18:56,206 --> 00:18:59,676
Every year, it puts out a fresh crown
of green leaves,

166
00:18:59,846 --> 00:19:04,795
and I guess it's got
many more years of life in it yet.

167
00:19:08,326 --> 00:19:13,195
The change of form
brings a positive advantage to the old tree.

168
00:19:13,366 --> 00:19:18,884
A hollow cylinder is better able
to absorb great shocks than a solid pillar.

169
00:19:20,086 --> 00:19:23,476
Trees standing out in the open,
as they do in parks,

170
00:19:23,646 --> 00:19:26,558
can get severely buffeted by stormy winds,

171
00:19:26,726 --> 00:19:30,878
and it's not unusual after a gale
to see young oaks uprooted,

172
00:19:31,046 --> 00:19:36,916
whereas older ones, with the age and girth
to become hollow, are still standing.

173
00:19:41,126 --> 00:19:45,722
The surgery performed by the fungus
brings other advantages, too.

174
00:19:45,886 --> 00:19:51,279
It enables the oak to reclaim
some of its lifetime savings.

175
00:19:51,446 --> 00:19:57,282
Roots develop inside the hollow trunk,
grow down into the ground within the cylinder,

176
00:19:57,446 --> 00:20:02,645
and collect nutriment that the fungus
has released from the wood as it digested it.

177
00:20:02,806 --> 00:20:06,162
And that is not the only goodness
to be found here.

178
00:20:08,566 --> 00:20:11,524
Animals have come to live in the hollow tree.

179
00:20:11,686 --> 00:20:18,080
Owls may be roosting in its upper parts,
bats hanging from its walls.

180
00:20:22,326 --> 00:20:27,559
Its lodgers, having fed out in the woodland,
drop their dung within the hollow.

181
00:20:27,726 --> 00:20:33,437
So the tree receives food from places
that otherwise would be far beyond its reach.

182
00:20:37,726 --> 00:20:40,445
So, thanks to its fungal partner,

183
00:20:40,606 --> 00:20:44,724
an oak often has an old age
that is both robust and well-fed.

184
00:20:51,606 --> 00:20:55,724
But fungi bring food to many plants
throughout their lives,

185
00:20:55,886 --> 00:21:02,200
and that is particularly so in forests such as
this one on the north-west coast of America.

186
00:21:04,006 --> 00:21:09,603
Even the tallest of these giant spruces,
totally healthy and in the prime of its life,

187
00:21:09,766 --> 00:21:13,645
is dependent for its health
and strength on a fungus.

188
00:21:15,046 --> 00:21:18,675
Its partner is down here.

189
00:21:22,886 --> 00:21:27,482
This is a rootlet through which the tree
absorbs its nourishment,

190
00:21:27,646 --> 00:21:31,719
but wrapped round it
are a mass of tiny white threads.

191
00:21:31,886 --> 00:21:36,038
They belong to the fungus,
and are part of a dense mesh

192
00:21:36,206 --> 00:21:42,554
which vastly increases the surface area through
which the tree can absorb water and nutrients.

193
00:21:42,726 --> 00:21:46,355
The partnership starts
at the very beginning of a tree's life,

194
00:21:46,526 --> 00:21:51,805
when a fungus living in the soil entwines itself
around the seedling's infant roots.

195
00:21:51,966 --> 00:21:56,721
Indeed, seedlings that have the misfortune
to germinate in soil without fungi

196
00:21:56,886 --> 00:21:59,446
are likely to starve to death.

197
00:22:00,446 --> 00:22:05,474
But if there's a fungus to convey food to it,
the seedling will get a good start.

198
00:22:07,846 --> 00:22:10,599
And that connection is never broken.

199
00:22:10,766 --> 00:22:15,965
An adult tree is able to collect
nutriment-laden moisture from fungal threads,

200
00:22:16,126 --> 00:22:20,677
suck it along its roots,
up the piping in its trunk, and into its leaves,

201
00:22:20,846 --> 00:22:27,479
and there combine it with that other essential
raw material, carbon dioxide gas, to make food.

202
00:22:35,526 --> 00:22:39,599
So trees, including giants like this one,

203
00:22:39,766 --> 00:22:44,078
can't grow without the help
of tiny organisms in the soil.

204
00:22:44,246 --> 00:22:47,397
Organisms we don't even notice until they fruit,

205
00:22:47,566 --> 00:22:51,957
and that may not happen
more than two or three days in twenty years.

206
00:23:10,246 --> 00:23:16,196
This is how the fly agaric uses its share
of the profits from the partnership.

207
00:23:30,046 --> 00:23:34,881
About a quarter of the sugars and starches
produced by the tree in its leaves

208
00:23:35,046 --> 00:23:41,838
travel back down the trunk and into the ground
to feed its multitude of fungal partners.

209
00:24:03,406 --> 00:24:07,843
Fungi fruit so briefly and often so rarely,
each in its own season,

210
00:24:08,006 --> 00:24:12,158
it's difficult to appreciate
how widespread they are and how varied.

211
00:24:12,326 --> 00:24:16,638
There are over a thousand different species
in the coniferous forests.

212
00:24:17,526 --> 00:24:19,801
Although trees do have preferences,

213
00:24:19,966 --> 00:24:25,438
any one individual may have links
with up to 200 different partners.

214
00:24:25,606 --> 00:24:28,837
Partnership with fungi is not limited to trees.

215
00:24:29,006 --> 00:24:31,804
Many smaller plants
are also dependent on them.

216
00:24:31,966 --> 00:24:35,754
And none more so
than those most glamorous of plants...

217
00:24:37,046 --> 00:24:38,638
..orchids.

218
00:24:44,166 --> 00:24:49,160
It seems paradoxical that such opulent
and flamboyant blooms as these

219
00:24:49,326 --> 00:24:55,959
should be totally dependent on the help of drab,
threadlike organisms wrapped around their roots.

220
00:25:08,766 --> 00:25:12,679
Most plants provision their seeds
with stores of food

221
00:25:12,846 --> 00:25:16,316
to fuel germination
and the first stages of growth.

222
00:25:16,486 --> 00:25:18,761
But not these orchids.

223
00:25:18,926 --> 00:25:21,804
This is an orchid seed capsule, and here...

224
00:25:24,486 --> 00:25:29,844
..is orchid seed,
so fine it's blowing away in the air.

225
00:25:30,006 --> 00:25:34,875
Minute seeds like this have always been
extremely difficult to get to germinate.

226
00:25:35,046 --> 00:25:39,722
Infuriatingly, the seed from some
of the most dazzling and rare of orchids

227
00:25:39,886 --> 00:25:41,956
wouldn't germinate at all.

228
00:25:42,126 --> 00:25:45,357
And then scientists tackled the problem.

229
00:25:47,526 --> 00:25:51,917
They found that many orchids
have their own special fungal partner.

230
00:25:52,086 --> 00:25:57,365
They devised ways of isolating that fungus
and then culturing it with the orchid seed.

231
00:25:58,286 --> 00:26:03,360
Under the right conditions,
the two strike up their partnership immediately.

232
00:26:12,086 --> 00:26:18,161
The fungus extracts nutriment from the culture
medium in a way the orchid can't do for itself,

233
00:26:18,326 --> 00:26:21,284
and supplies it to the young plant.

234
00:26:46,366 --> 00:26:52,441
Within a month, the fungus has invaded the seed
and started conveying nutriment to it,

235
00:26:52,606 --> 00:26:57,600
and the young seedling is well on its way
to becoming a vigorous plant.

236
00:27:10,566 --> 00:27:16,004
You could argue that it is the orchid which is
the dominant member of this partnership.

237
00:27:16,166 --> 00:27:20,125
It is, after all,
the one we can see with our naked eye.

238
00:27:21,926 --> 00:27:27,046
But there are plant-fungus relationships in
which the balance, if anything, is the other way.

239
00:27:27,206 --> 00:27:31,916
It's the fungus which determines the shape
into which the partnership grows.

240
00:27:32,086 --> 00:27:34,839
One of those shapes is flat and plate-like,

241
00:27:35,006 --> 00:27:39,477
but to see the two partners, you have to look
through very high magnification

242
00:27:39,646 --> 00:27:44,117
such as provided by
a scanning electron microscope like this.

243
00:27:44,286 --> 00:27:48,438
This is a section
through one of those platelike partnerships.

244
00:27:48,606 --> 00:27:52,679
Here is the top,
which is formed entirely by the fungus.

245
00:27:52,846 --> 00:27:58,000
These threads are part of the fungus,
and this sphere here is the plant.

246
00:27:58,166 --> 00:28:00,999
To see just how intimate their relationship is,

247
00:28:01,166 --> 00:28:04,636
you have to look at them
at even greater magnification.

248
00:28:04,806 --> 00:28:08,481
This picture is magnified 10,000 times.

249
00:28:08,646 --> 00:28:10,716
Here are the fungal threads,

250
00:28:10,886 --> 00:28:16,961
and this is the plant, the alga,
from which they're getting their sustenance.

251
00:28:27,446 --> 00:28:29,880
Together, the two different organisms

252
00:28:30,046 --> 00:28:34,039
form one of the most widely distributed
of living structures,

253
00:28:34,206 --> 00:28:35,764
lichens.

254
00:28:39,606 --> 00:28:44,999
The partners operate so closely together
that each pairing is given a single name,

255
00:28:45,166 --> 00:28:49,284
and there are over 13,000 of them.

256
00:29:04,206 --> 00:29:08,438
They not only form these hard skins
and curling crusts,

257
00:29:08,606 --> 00:29:12,884
some lichens grow into little branched bushes.

258
00:29:26,286 --> 00:29:29,642
And very successful organisms they are, too.

259
00:29:29,806 --> 00:29:33,435
They come into their own
in the harshest of conditions.

260
00:29:33,606 --> 00:29:36,837
No grass can grow on these arid slopes,

261
00:29:37,006 --> 00:29:40,919
here on the edge of the Namib Desert
in southern Africa.

262
00:29:41,086 --> 00:29:47,559
This extraordinary orange colour
is produced entirely by a carpet of lichen.

263
00:29:53,166 --> 00:29:57,478
It can get so hot here
that it's painful to put your hand on rock.

264
00:29:57,646 --> 00:30:01,844
And there's no relief with a shower of rain,
for it hardly ever falls.

265
00:30:02,006 --> 00:30:05,794
Yet 29 species of lichen flourish here.

266
00:30:07,366 --> 00:30:11,120
The red one is particularly successful.

267
00:30:21,686 --> 00:30:28,637
One of the functions of the fungus
is to absorb moisture and deliver it to the algae.

268
00:30:28,806 --> 00:30:34,642
But if there's no moisture, the whole organism
simply shrivels and becomes brittle.

269
00:30:34,806 --> 00:30:37,764
And that's what's happened to this here.

270
00:30:37,926 --> 00:30:43,717
But for this lichen, salvation is going to come
from a very surprising source.

271
00:30:47,686 --> 00:30:50,837
The sea lies only a mile or so away.

272
00:30:51,006 --> 00:30:54,476
A cold current sweeps up the coast
from the south.

273
00:30:54,646 --> 00:30:59,117
The hot air rising from the desert
pulls in cold air from the sea,

274
00:30:59,286 --> 00:31:02,483
and the mixture produces fog.

275
00:31:11,366 --> 00:31:15,439
The moisture condenses as droplets
on the lichen's branches.

276
00:31:15,606 --> 00:31:20,885
It's swiftly absorbed by the fungal skin
and conveyed to the alga within.

277
00:31:21,046 --> 00:31:26,757
And suddenly, and miraculously,
the desiccated branches turn green.

278
00:31:59,686 --> 00:32:05,363
But even in the best circumstances,
lichen grow only very slowly,

279
00:32:05,526 --> 00:32:09,439
often only a millimetre or so a year.

280
00:32:09,606 --> 00:32:15,681
One place shows vividly and accurately
just how slowly that is - a churchyard.

281
00:32:16,686 --> 00:32:23,444
The lichens, with their ability to live
on bare rock, flourish on the tombstones.

282
00:32:26,886 --> 00:32:28,763
The dates of the inscriptions

283
00:32:28,926 --> 00:32:33,954
tell us exactly when the bare stone surface
was first exposed to the elements,

284
00:32:34,126 --> 00:32:37,562
and became available for colonisation by lichens.

285
00:32:37,726 --> 00:32:43,198
Some of these blotches,
only an inch or so across, may be centuries old.

286
00:32:55,286 --> 00:32:59,165
Lichens also grow in undisturbed ancient forests

287
00:32:59,326 --> 00:33:02,557
such as those on the Pacific coast
of North America.

288
00:33:05,006 --> 00:33:08,237
Trees here may live five or six hundred years,

289
00:33:08,406 --> 00:33:14,197
but well before they reach this advanced age,
they are usually colonised by various lichens

290
00:33:14,366 --> 00:33:18,678
that hang in great tufts and blankets
from their branches.

291
00:33:36,926 --> 00:33:43,240
So plants form intimate partnerships with
members of the other great kingdoms of life.

292
00:33:43,406 --> 00:33:47,718
In tropical forests, with members
of the animal kingdom particularly,

293
00:33:47,886 --> 00:33:50,195
ants and other insects.

294
00:33:50,366 --> 00:33:54,120
Here in the great coniferous forests
of North America,

295
00:33:54,286 --> 00:33:57,403
partnerships with fungi are particularly common,

296
00:33:57,566 --> 00:34:03,596
ranging from those that produced these lichens
dangling from the boughs of this great spruce,

297
00:34:03,766 --> 00:34:09,045
down to the tangle of tiny threads
meshed around the roots of the tree

298
00:34:09,206 --> 00:34:11,401
250 feet below me.

299
00:34:11,566 --> 00:34:17,675
And there are also partnerships within
the plant kingdom, between plant and plant.

300
00:34:17,846 --> 00:34:19,916
Some are just simple -

301
00:34:20,086 --> 00:34:26,525
these mosses and ferns,
which use the spruce tree simply as a perch.

302
00:34:26,686 --> 00:34:31,362
But there are some partnerships
between plants that are much more intimate.

303
00:34:32,726 --> 00:34:34,603
This is a mistletoe.

304
00:34:34,766 --> 00:34:39,556
It can only exist in partnership with a tree,
for it has no roots of its own.

305
00:34:39,726 --> 00:34:42,843
But this is a very one-sided relationship.

306
00:34:43,006 --> 00:34:46,555
The mistletoe has green leaves,
so it can manufacture food,

307
00:34:46,726 --> 00:34:51,595
but it draws all the liquid it needs
from the tree onto which it's fastened itself.

308
00:34:52,486 --> 00:34:58,561
The tree gets nothing from the arrangement.
The mistletoe, in short, is a parasite.

309
00:35:00,206 --> 00:35:03,835
The mistletoe family has over 1,000 species.

310
00:35:04,006 --> 00:35:08,363
Here in Australia alone there are 75,
so many and so widely dispersed

311
00:35:08,526 --> 00:35:12,360
that somewhere or another
there is always one in fruit.

312
00:35:12,526 --> 00:35:17,156
And that makes it possible
for one bird to eat almost nothing else.

313
00:35:18,206 --> 00:35:22,836
The mistletoe bird knows
exactly how to extract the fruit.

314
00:35:39,806 --> 00:35:44,277
The bird digests the fleshy coating
of the seed with extraordinary speed.

315
00:35:44,446 --> 00:35:47,677
It takes less than half an hour
from beak to bottom.

316
00:35:47,846 --> 00:35:53,955
The seed, when it emerges, is still
phenomenally sticky, and has to be wiped off,

317
00:35:54,126 --> 00:35:56,799
which suits the mistletoe very well.

318
00:36:07,966 --> 00:36:09,843
The seed, when it comes out,

319
00:36:10,006 --> 00:36:14,875
remains attached to the bird's behind
by a long, sticky thread,

320
00:36:15,046 --> 00:36:19,483
and the bird has to have
a special technique for breaking it.

321
00:36:30,406 --> 00:36:36,038
Every time it needs to detach a seed,
it has to perform this little dance.

322
00:36:57,126 --> 00:37:01,085
It's this stickiness that is the key
to the mistletoe's success

323
00:37:01,246 --> 00:37:03,885
in getting from one tree to another.

324
00:37:04,046 --> 00:37:09,359
Once parked on a living branch,
the seed quickly plugs itself in.

325
00:37:17,446 --> 00:37:20,279
With a connection to its host's liquid supply,

326
00:37:20,446 --> 00:37:24,325
it can build leaves
and start making food for itself.

327
00:37:37,326 --> 00:37:39,635
This is another mistletoe.

328
00:37:39,806 --> 00:37:42,445
It grows only in Western Australia,

329
00:37:42,606 --> 00:37:47,964
and it flowers in December, which is why
it's known locally as the Christmas tree.

330
00:37:48,126 --> 00:37:51,675
I know it's a mistletoe
from the character of its flowers,

331
00:37:51,846 --> 00:37:54,360
and it does have green, fleshy leaves.

332
00:37:54,526 --> 00:37:58,360
But from other points of view,
it's very unlike other mistletoes,

333
00:37:58,526 --> 00:38:01,836
most obviously because
this is a free-standing tree

334
00:38:02,006 --> 00:38:04,964
that doesn't seem to be parasitising anything.

335
00:38:05,126 --> 00:38:12,282
But in fact, it gives us a very good idea as to
how parasitism might have started in this family.

336
00:38:12,446 --> 00:38:14,437
Have a look at its roots.

337
00:38:23,166 --> 00:38:28,001
This is the root
that belongs to the Christmas tree,

338
00:38:28,166 --> 00:38:32,444
and this root belongs to another,
completely different bush nearby.

339
00:38:32,606 --> 00:38:37,964
And the Christmas tree
has encircled this other root with a white ring.

340
00:38:38,126 --> 00:38:42,324
It has plugged itself into the root system
of another plant.

341
00:38:42,486 --> 00:38:47,241
And it gets all its water and minerals in that way.

342
00:38:47,406 --> 00:38:52,082
And it's not at all fussy
about what kind of plant it parasitises.

343
00:38:52,246 --> 00:38:56,717
Grasses, sedges, small bushes,
big trees, gum trees, sycads,

344
00:38:56,886 --> 00:38:58,842
it will go for the lot.

345
00:38:59,966 --> 00:39:04,437
But at least the mistletoes have leaves
to make some food for themselves.

346
00:39:04,606 --> 00:39:07,484
A few parasitic plants don't even have that.

347
00:39:10,686 --> 00:39:14,076
These are the germinating seeds of dodder.

348
00:39:14,246 --> 00:39:18,478
They have to find their host
within a few days or they will die.

349
00:39:29,606 --> 00:39:32,120
A favourite target is the nettle.

350
00:39:32,286 --> 00:39:37,679
Well-armed with stings it may be,
but they are no defence against dodder.

351
00:39:41,966 --> 00:39:46,721
The seedlings can detect whether a nettle stem
is feeble or well-nourished,

352
00:39:46,886 --> 00:39:49,446
and they pick their victim with care.

353
00:39:54,486 --> 00:40:00,641
This is a strong, healthy one, good to feed on.
In goes a nozzle.

354
00:40:10,726 --> 00:40:17,359
The dodder sucks the nettle's sap, which then
fuels its growth and its hunt for another victim.

355
00:40:34,926 --> 00:40:38,714
The dodder is a relative of the bindweed,
convolvulus,

356
00:40:38,886 --> 00:40:41,844
and it climbs in the same sort of way.

357
00:41:05,246 --> 00:41:07,316
Wherever the feeding seems good,

358
00:41:07,486 --> 00:41:12,276
the parasite inserts a tube
and draws off the nettle's sap.

359
00:41:24,246 --> 00:41:29,036
Once fully established, drinking from the nettle
through hundreds of connections,

360
00:41:29,206 --> 00:41:34,963
the dodder is siphoning off enough nourishment
from its victim to enable it to flower.

361
00:42:12,726 --> 00:42:19,882
Eventually, the whole bed of nettles
is overwhelmed by writhing dodder stems.

362
00:42:49,806 --> 00:42:55,722
The dodder is completely parasitic,
getting all it needs from another plant.

363
00:42:55,886 --> 00:43:00,596
But the relationship between parasite
and host can be even closer.

364
00:43:00,766 --> 00:43:04,361
Here in the forests of Borneo,
there is an enormous parasite

365
00:43:04,526 --> 00:43:10,556
whose relationship with its host is so intimate
that the parasite is invisible most of the year,

366
00:43:10,726 --> 00:43:13,524
so it's not easy to find.

367
00:43:38,646 --> 00:43:43,162
This is the first
that anyone or anything sees of it.

368
00:43:43,326 --> 00:43:49,037
The bud is obviously coming from this root,
but the root doesn't belong to this.

369
00:43:49,206 --> 00:43:53,484
The root is part of this great vine.

370
00:44:01,326 --> 00:44:06,923
Inside the massive trunk of this vine,
there's a multitude of hair-like filaments.

371
00:44:07,086 --> 00:44:11,557
They don't belong to the vine
but to a parasite called rafflesia.

372
00:44:11,726 --> 00:44:15,685
Rafflesia has no stem, no leaves,
and never will have.

373
00:44:15,846 --> 00:44:20,044
It feeds entirely on the sap produced by the vine.

374
00:44:20,206 --> 00:44:25,326
The only time rafflesia emerges
into the outside world is in order to flower.

375
00:44:25,486 --> 00:44:28,842
But that was just a young bud,
maybe three weeks old.

376
00:44:29,006 --> 00:44:33,045
If I follow the root of the vine,
maybe I'll find more.

377
00:44:42,326 --> 00:44:45,204
Two more, but still small.

378
00:44:50,366 --> 00:44:52,197
A bigger one.

379
00:44:58,366 --> 00:45:02,154
And this one looks as though
it might well open tonight.

380
00:45:40,326 --> 00:45:45,605
By the time dawn comes and the first rays
of the sun filter down into the forest,

381
00:45:45,766 --> 00:45:48,234
the flower is almost fully open.

382
00:45:58,526 --> 00:46:03,122
Rafflesia produces
the largest single flower on earth.

383
00:46:03,286 --> 00:46:06,835
A big one can be three feet across.

384
00:46:13,046 --> 00:46:18,404
The surface of the warty petals
looks a little like that of a putrefying corpse.

385
00:46:18,566 --> 00:46:20,955
There's a faint smell of rotting fish,

386
00:46:21,126 --> 00:46:27,645
and the huge flower quickly attracts those
that find much of their food in carrion - blowflies.

387
00:46:36,766 --> 00:46:42,523
In the bottom of the cup, a great disc
covered in spikes stands on a pedestal.

388
00:46:42,686 --> 00:46:47,043
The flies go in to investigate
and crawl all over it.

389
00:46:56,646 --> 00:47:01,561
Hanging from the underside of the disc
are droplets of liquid pollen.

390
00:47:05,926 --> 00:47:12,035
As the flies explore, they touch the droplets
and get saddled with a dab of pollen.

391
00:47:18,566 --> 00:47:20,636
This will only benefit rafflesia

392
00:47:20,806 --> 00:47:28,315
if the fly finds another of these very rare flowers
fully open in the forest to deliver its load to.

393
00:47:29,326 --> 00:47:32,921
Rafflesia produces the biggest single flower
in the world,

394
00:47:33,086 --> 00:47:37,557
but why, when all it needs to attract are flies?

395
00:47:38,846 --> 00:47:41,201
Plants, like other living organisms,

396
00:47:41,366 --> 00:47:45,644
can only afford to spend
a limited amount of food on reproduction.

397
00:47:45,806 --> 00:47:51,802
But rafflesia does not, after all, earn its food,
it takes it straight from the vine.

398
00:47:52,646 --> 00:47:55,365
Provided the vine is not fatally injured,

399
00:47:55,526 --> 00:48:00,156
there seems to be no limit
to the amount rafflesia may extract.

400
00:48:00,326 --> 00:48:05,161
Maybe an unearned income
in the plant world, as elsewhere,

401
00:48:05,326 --> 00:48:10,036
can lead to extravagance
on a truly monumental scale.

402
00:48:11,305 --> 00:48:17,377
Support us and become VIP member 
to remove all ads from www.OpenSubtitles.org