0:00:25 > 0:00:30Plants have a family tree stretching back nearly half a billion years.
0:00:34 > 0:00:38They have developed an extraordinary range of strategies to survive.
0:00:42 > 0:00:44This tree is a bristlecone pine.
0:00:44 > 0:00:47It's taken thousands of years to reach this size.
0:00:49 > 0:00:52It has seen empires rise and fall,
0:00:52 > 0:00:55kings, queens and presidents come and go
0:00:55 > 0:01:00and may have seen the sun rise more than 1.5 million times.
0:01:02 > 0:01:06Bristlecone pines are the oldest living things on Earth.
0:01:15 > 0:01:19Bamboo is the fastest growing plant.
0:01:21 > 0:01:26It will be full-grown - 30 metres tall - in just 90 days.
0:01:37 > 0:01:41Like animals, plants are constantly competing for food.
0:01:44 > 0:01:46Striving to produce offspring
0:01:48 > 0:01:51and battling against predators.
0:01:59 > 0:02:03They will deceive and, in some cases,
0:02:03 > 0:02:06they will even hunt.
0:02:31 > 0:02:38We often don't notice such dramatic behaviour because, to our eyes, it happens so slowly.
0:02:38 > 0:02:40But if time is compressed
0:02:40 > 0:02:44and you shift perspective to the plants' point of view,
0:02:44 > 0:02:47their world comes spectacularly to life.
0:02:47 > 0:02:49The events in this woodland
0:02:49 > 0:02:52can build to a view of half a year in less than a minute.
0:03:36 > 0:03:40Like animals, plants need food and water.
0:03:53 > 0:03:58But what sets them apart is their struggle for light.
0:04:09 > 0:04:15Plants must have light in order to grow and will do anything to get as much as they need.
0:04:19 > 0:04:25The forest might appear to be the perfect place for plants to thrive.
0:04:25 > 0:04:28Yet down here on the forest floor
0:04:28 > 0:04:31is one of the hardest places imaginable
0:04:31 > 0:04:34for a young plant to begin its life.
0:04:36 > 0:04:38The canopy above is so thick
0:04:38 > 0:04:41that only a little sunlight can filter through.
0:04:46 > 0:04:50For this sapling, too little light means death.
0:05:00 > 0:05:04But plants on the forest floor need not be passive.
0:05:11 > 0:05:13If the light won't come to them,
0:05:13 > 0:05:16they can go to the light.
0:05:21 > 0:05:24But they still have a problem.
0:05:24 > 0:05:28The light is 50 metres above them.
0:05:28 > 0:05:31So, they must climb.
0:05:40 > 0:05:44It's much easier to use another plant as scaffolding.
0:05:53 > 0:05:59But they won't get very high unless they can hold on tight.
0:06:03 > 0:06:06Like fingertips searching for a hold,
0:06:06 > 0:06:09this ivy's adhesive pads grip the bark.
0:06:12 > 0:06:17Instead of sticking to the trees, some climbers use sharp claws.
0:06:21 > 0:06:26The cat's claw creeper hooks its tendrils into the tiniest crevices
0:06:26 > 0:06:28and hauls itself to the top.
0:06:37 > 0:06:38With every metre it climbs,
0:06:38 > 0:06:42the light gets a little stronger, fuelling more growth.
0:06:48 > 0:06:53This tendril of a passion flower seems to flail aimlessly in mid-air,
0:06:53 > 0:06:56but in fact it's searching for an anchor point.
0:07:04 > 0:07:09Its tendril coils on itself, pulling the plant towards its support.
0:07:17 > 0:07:22In a matter of just days, these climbers make it to the canopy.
0:07:25 > 0:07:30Now with light in plentiful supply, these plants are able to flower.
0:07:36 > 0:07:39Other plants have a different strategy
0:07:39 > 0:07:42to find the light they need in the crowded forest.
0:07:44 > 0:07:46These are air-plants.
0:07:46 > 0:07:49They grow on the upper branches of tall trees
0:07:49 > 0:07:53and spend their whole lives basking in the light.
0:07:54 > 0:08:00But growing 50 metres above the ground does have its drawbacks.
0:08:00 > 0:08:05Most plants get water and nutrients through their roots in the ground.
0:08:05 > 0:08:10For an air-plant, with their roots planted in the tree tops,
0:08:10 > 0:08:11this isn't an option.
0:08:13 > 0:08:15But they have a solution.
0:08:17 > 0:08:23First, the bare roots have an extraordinary ability to soak up water like blotting paper.
0:08:26 > 0:08:30The slightest rain or mist, and they absorb every drop.
0:08:34 > 0:08:37They also have a way of gathering nutrients.
0:08:40 > 0:08:44Their roots trap falling leaves which eventually rot
0:08:44 > 0:08:48and provide the plants with their own personal supply of compost.
0:08:56 > 0:08:5820,000 different plants -
0:08:58 > 0:09:03orchids, bromeliads and ferns have taken up this remarkable lifestyle.
0:09:25 > 0:09:30For a plant to thrive, it must not only get enough nutrients,
0:09:30 > 0:09:33but also the right balance of nutrients.
0:09:34 > 0:09:40The soil in this waterlogged bog is very poor quality, lacking in nitrogen.
0:09:42 > 0:09:46But these strange plants have an ingenious strategy.
0:09:48 > 0:09:54Their leaves are covered in tentacles, tipped with droplets of what appears to be morning dew.
0:09:57 > 0:10:01These droplets give the plant its name - the sundew.
0:10:07 > 0:10:12They're sweet-smelling and attractive to many insects.
0:10:12 > 0:10:16But they're also extremely sticky.
0:10:20 > 0:10:25Mosquitoes emerge in huge numbers from the boggy water
0:10:25 > 0:10:27and the sundews are ready.
0:10:59 > 0:11:03The sundew's tentacles are living fly-paper.
0:11:10 > 0:11:14Struggling only makes matters worse.
0:11:17 > 0:11:20With each contact, the plant tightens its grip.
0:11:28 > 0:11:30As more and more tentacles envelop the prey,
0:11:30 > 0:11:33the droplets spread across its body.
0:11:37 > 0:11:41Eventually, the insect is smothered and drowns in sticky fluid.
0:11:44 > 0:11:48Digestive enzymes break down the body into a nitrogen-rich meal
0:11:48 > 0:11:51which is absorbed by the plant.
0:11:51 > 0:11:55Without animal tissues, this plant would not survive.
0:12:00 > 0:12:02But there's another carnivorous plant
0:12:02 > 0:12:06that's an even more sophisticated predator.
0:12:15 > 0:12:17The Venus fly trap.
0:12:25 > 0:12:29Like the sundew, it makes itself very attractive,
0:12:29 > 0:12:32oozing nectar across the brim of each leaf.
0:12:45 > 0:12:50But any visiting insect had better watch out for these six tiny hairs.
0:13:02 > 0:13:05This fly has to tread carefully.
0:13:13 > 0:13:14If it strikes one hair,
0:13:16 > 0:13:19it can carry on feeding.
0:13:19 > 0:13:21But a timer has been set.
0:13:29 > 0:13:34A second strike in less than 20 seconds and the fly is doomed.
0:13:42 > 0:13:49An electrical impulse is triggered and the leaf snaps shut in just a fraction of a second.
0:13:50 > 0:13:54The tips lock together like prison bars.
0:14:02 > 0:14:09If the fly is very big, or very small, it may just manage to escape.
0:14:09 > 0:14:11But most are trapped.
0:14:13 > 0:14:15And die.
0:14:36 > 0:14:39Ten days later, the trap re-opens.
0:14:42 > 0:14:46All that remains is a husk.
0:14:46 > 0:14:53The plant has finished its meal and resets itself for its next victim.
0:14:56 > 0:15:00But there is one time of year when the Venus fly trap
0:15:00 > 0:15:03needs some of the visiting insects to live.
0:15:04 > 0:15:08It needs their help to be pollinated.
0:15:08 > 0:15:11It sends up flowers on tall stems,
0:15:11 > 0:15:14well away from the danger of the traps below.
0:15:28 > 0:15:32Here, insects can feed safely on nectar.
0:15:33 > 0:15:36In return, they provide a vital service,
0:15:36 > 0:15:39carrying pollen from flower to flower.
0:15:44 > 0:15:48But the truce is only temporary.
0:15:48 > 0:15:53When pollination is over, it's back to business as usual.
0:16:02 > 0:16:0680% of plant species on Earth have flowers.
0:16:08 > 0:16:10Flowers have just one role -
0:16:10 > 0:16:14to enable the plant to produce offspring.
0:16:16 > 0:16:19Colour, perfume, nectar and shape
0:16:19 > 0:16:24all act to make a flower irresistible.
0:16:24 > 0:16:28Sunflowers grow to face the rising sun.
0:16:28 > 0:16:32The warmth of the rays speeds the production of nectar
0:16:32 > 0:16:34and this lures pollinators.
0:16:37 > 0:16:38One after another,
0:16:38 > 0:16:42hundreds of individual florets produce pollen-covered stamens.
0:16:54 > 0:16:56And, like most flowers,
0:16:56 > 0:17:00sunflowers establish a close relationship with animals
0:17:00 > 0:17:03in order to ensure their reproduction.
0:17:09 > 0:17:11As these bees busily feed on nectar,
0:17:11 > 0:17:15they unwittingly brush against the stamens, collecting pollen,
0:17:15 > 0:17:17and then carry it from flower to flower.
0:17:23 > 0:17:25The sunflower is fertilised.
0:17:31 > 0:17:34In the sun-drenched fields of southern France,
0:17:34 > 0:17:37the flowering season is a long one,
0:17:37 > 0:17:40but not all plants have this luxury.
0:17:43 > 0:17:49Cradle Mountain in Tasmania is blasted by bitter Antarctic winds.
0:17:52 > 0:17:55To reproduce, the Richea honey bush must flower.
0:17:57 > 0:18:01But the delicate parts of the flowers risk being damaged by the cold.
0:18:03 > 0:18:07The plant appears to have an ingenious solution.
0:18:09 > 0:18:11The flower petals fuse together,
0:18:11 > 0:18:15forming an insulated, protective case around its stamens.
0:18:15 > 0:18:19However, this creates another problem,
0:18:19 > 0:18:23the flower case is so well sealed that, unfortunately,
0:18:23 > 0:18:26it also keeps out pollinating insects.
0:18:28 > 0:18:30During brief, sunny spells,
0:18:30 > 0:18:34the flowers warm up and suddenly start producing nectar.
0:18:37 > 0:18:41This attracts a bird - the Black Currawong.
0:18:42 > 0:18:46It has the strength to rip open the flowers' outer casing
0:18:46 > 0:18:48and gets its reward of nectar.
0:18:48 > 0:18:54At the same time, it exposes the delicate stamens to waiting insects.
0:19:00 > 0:19:03With luck, there's enough time for pollination
0:19:03 > 0:19:07before the biting wind kills the flowers.
0:19:14 > 0:19:19For some plants, the relationship with their pollinators
0:19:19 > 0:19:20is not collaborative,
0:19:20 > 0:19:23it's war.
0:19:23 > 0:19:26Butterflies, and in such numbers,
0:19:26 > 0:19:30would seem to be perfect pollinators for any flower.
0:19:31 > 0:19:35The Sandhill milkweed blooms every spring
0:19:35 > 0:19:38in the sandy meadows of Florida.
0:19:39 > 0:19:42It times its flowering perfectly to match the arrival
0:19:42 > 0:19:45of Monarch butterflies migrating here from Mexico.
0:19:48 > 0:19:51The Monarchs search out milkweed plants,
0:19:51 > 0:19:55but they have something other than pollination on their minds.
0:19:55 > 0:19:57Rather than collect pollen,
0:19:57 > 0:20:00this female lays her eggs on the milkweed leaf.
0:20:05 > 0:20:09This is the only plant the caterpillars can eat.
0:20:17 > 0:20:20But the milkweed has a defence mechanism.
0:20:25 > 0:20:29As the caterpillar bites into a vein,
0:20:29 > 0:20:32a kind of latex swells out engulfing it.
0:20:37 > 0:20:40If the caterpillar isn't quick, it will drown...
0:20:42 > 0:20:45or find its jaws glued together.
0:20:48 > 0:20:50The plants' defence is so effective
0:20:50 > 0:20:53that only one third of the Monarch caterpillars
0:20:53 > 0:20:55make it through the first day.
0:20:57 > 0:21:02But the caterpillars that survive, grow in size and strength.
0:21:10 > 0:21:14And they go for the jugular.
0:21:14 > 0:21:17By carefully chewing through the main vein,
0:21:17 > 0:21:21the caterpillar drains the leaf of latex
0:21:21 > 0:21:23and cuts off its supply.
0:21:24 > 0:21:27The milkweed's leaf is now defenceless
0:21:27 > 0:21:29and the caterpillar eats in safety
0:21:29 > 0:21:32before preparing to pupate into a butterfly.
0:21:38 > 0:21:40But after about ten days,
0:21:40 > 0:21:45it becomes clear why the plant has endured this onslaught.
0:21:48 > 0:21:52A newly-hatched Monarch simply can't resist the nectar-filled cups
0:21:52 > 0:21:53of the milkweed flowers.
0:21:53 > 0:21:56As it moves across the flower heads,
0:21:56 > 0:22:00its feet slide between grooves in the petals
0:22:00 > 0:22:04where the flower's pollen sacs are waiting.
0:22:06 > 0:22:09As it flies off, the Monarch's feet hook out the pollen
0:22:09 > 0:22:15and carry it to the next flower and pollination is achieved.
0:22:15 > 0:22:18Although the milkweed has paid a heavy price,
0:22:18 > 0:22:22in the end it used the Monarch to get its way.
0:22:26 > 0:22:30Here in Dominica there's a plant that is so manipulative
0:22:30 > 0:22:33that it has enslaved its pollinator.
0:22:34 > 0:22:39The bright red structures of the Heliconia are actually modified leaves.
0:22:43 > 0:22:45These are its flowers.
0:22:45 > 0:22:48They may be small, but they play a very important role
0:22:48 > 0:22:53keeping nectar well guarded at the very bottom of their long stems.
0:22:53 > 0:22:56The purple-throated Carib hummingbird,
0:22:56 > 0:22:58with its long curved beak,
0:22:58 > 0:23:03is the only bird capable of reaching this energy-rich food.
0:23:04 > 0:23:09But, cleverly, the Heliconia rations the amount of nectar it produces
0:23:09 > 0:23:12to force the hummingbird into returning to the flower
0:23:12 > 0:23:14time and time again.
0:23:19 > 0:23:21Every time it makes a visit,
0:23:21 > 0:23:24it picks up more pollen on its beak and feathers.
0:23:30 > 0:23:32The hummingbird is like an addict.
0:23:32 > 0:23:34Not only does it never stray,
0:23:34 > 0:23:38but it will aggressively defend the flowers from thieves.
0:23:39 > 0:23:43The plant is the master in this relationship.
0:23:45 > 0:23:47To ensure it gets pollinated,
0:23:47 > 0:23:50Heliconia has made the hummingbird its prisoner.
0:23:58 > 0:24:02A plant's problems don't end once it's been pollinated.
0:24:04 > 0:24:08Plants need to spread their seeds as far away as possible,
0:24:08 > 0:24:12otherwise the adults will be in direct competition with their offspring.
0:24:15 > 0:24:18Here in South Africa, one flower achieves this
0:24:18 > 0:24:20by performing a remarkable trick.
0:24:27 > 0:24:32The plant waits dormant underground for more than a year.
0:24:33 > 0:24:36The first heavy rains for many months
0:24:36 > 0:24:39are the trigger the plant has been waiting for.
0:24:55 > 0:24:57Brunsvigia burst into flower.
0:25:05 > 0:25:08Their timing is perfect.
0:25:08 > 0:25:11These conditions are ideal for insects too.
0:25:14 > 0:25:18The flowers enjoy a few days of frenzied pollination.
0:25:30 > 0:25:34But it's not long before the searing heat returns.
0:25:34 > 0:25:38The flowers start to wilt, shrivel and die.
0:25:44 > 0:25:49Brunsvigia now needs to disperse its seeds widely,
0:25:49 > 0:25:53yet the flowers still have their seeds trapped inside.
0:25:54 > 0:25:57But the flower isn't finished yet.
0:26:00 > 0:26:03There are strong winds that blow across this landscape.
0:26:03 > 0:26:07They snap the dry, dead stalks, sending each and every plant
0:26:07 > 0:26:11cart-wheeling across the ground, casting seeds as it goes.
0:26:39 > 0:26:41With the heat threatening to dry them out,
0:26:41 > 0:26:44the seeds' germination has to be immediate.
0:27:05 > 0:27:07Deep in the forests of Borneo,
0:27:07 > 0:27:11some plants also use the wind to disperse their seeds,
0:27:11 > 0:27:16but in a completely different way - by giving their seeds wings.
0:27:20 > 0:27:24Some are helicopters that twist and turn their way down to the ground.
0:27:36 > 0:27:38But there is one that has a design
0:27:38 > 0:27:43that enables it to travel greater distances than all the others.
0:27:46 > 0:27:48This is Alsomitra.
0:27:48 > 0:27:50Its football-sized pod
0:27:50 > 0:27:55is packed full of hundreds of extraordinary seeds.
0:27:58 > 0:28:01Each is an almost aerodynamically perfect glider
0:28:01 > 0:28:04that can be supported by even the slightest breeze.
0:28:09 > 0:28:11Its paper-thin upswept wings
0:28:11 > 0:28:15allow it to travel hundreds of metres through the forest.
0:28:37 > 0:28:39Once the seed hits the ground,
0:28:39 > 0:28:43the wings rot away and the seed starts to germinate.
0:28:57 > 0:29:01A new Alsomitra vine starts to grow up towards the canopy
0:29:01 > 0:29:05and into the light - well away from its parent.
0:29:09 > 0:29:11There are other ways to disperse seeds
0:29:11 > 0:29:15and plants have evolved different tactics
0:29:15 > 0:29:17depending on where they live.
0:29:18 > 0:29:24In the desert of Arizona lives a master - the Saguaro cactus.
0:29:27 > 0:29:31In the cool of the night, the cacti open their radiant flowers.
0:29:42 > 0:29:46They're soon visited by nectar-feeding bats
0:29:46 > 0:29:49and as the bats move from cactus to cactus,
0:29:49 > 0:29:51they pollinate them.
0:30:10 > 0:30:13Each flower only lasts a night,
0:30:13 > 0:30:19but over three weeks, each cactus will produce more than 200 flowers.
0:30:27 > 0:30:31Every pollinated flower immediately begins to form a fruit at its base,
0:30:31 > 0:30:33packed with thousands of seeds.
0:30:48 > 0:30:52The mature Saguaro cacti are superbly adapted
0:30:52 > 0:30:56to survive out in the intense heat of the Sonoran Desert.
0:30:58 > 0:31:04But their seeds are delicate, and must find shade or they will scorch to death before they germinate.
0:31:04 > 0:31:08The seeds are covered with succulent sweet flesh -
0:31:08 > 0:31:12a meal that all sorts of desert creatures find irresistible.
0:31:16 > 0:31:21White winged doves are among the first to reach the ripening fruit.
0:31:21 > 0:31:24The seeds survive in the birds' stomachs
0:31:24 > 0:31:26and will be carried many miles
0:31:26 > 0:31:29before being deposited in their droppings.
0:31:29 > 0:31:32Their own little packet of fertiliser.
0:31:35 > 0:31:38But the cactus doesn't just rely on birds.
0:31:38 > 0:31:42Fallen fruit provides a bonanza for creatures on the ground.
0:31:46 > 0:31:50Foraging ants quickly gather seeds and flesh.
0:31:50 > 0:31:53That's if a tortoise doesn't get there first.
0:31:55 > 0:31:59The greater range of animals the cactus can get to eat its fruit,
0:31:59 > 0:32:03the more likely the seeds within will be carried to the perfect place to germinate.
0:32:05 > 0:32:08The ants carry the seeds underground into their nests,
0:32:08 > 0:32:11often excavated among the roots of trees.
0:32:15 > 0:32:18The tortoise too will head for shade.
0:32:18 > 0:32:21It spends much of its day cooling off under trees
0:32:21 > 0:32:24where it's sure to leave undigested seeds in its dung.
0:32:29 > 0:32:32Now the seeds wait for the rains to come.
0:32:36 > 0:32:38THUNDER
0:32:45 > 0:32:49Of the 40 million or so seeds a cactus produces in its lifetime,
0:32:49 > 0:32:53the chances are that only one will develop into a plant
0:32:53 > 0:32:55that outlives its parent.
0:32:57 > 0:32:59If it was lucky enough to find shade,
0:32:59 > 0:33:01a seed will still take ten years
0:33:01 > 0:33:04to become a five centimetre tall cactus.
0:33:07 > 0:33:11To reach the size of its parents, possibly ten metres,
0:33:11 > 0:33:13will take at least 100 years.
0:33:18 > 0:33:24Plants can survive in the most unlikely and inhospitable places on Earth.
0:33:24 > 0:33:29Here on Socotra, a remote island in the Arabian Sea,
0:33:29 > 0:33:31the dry season is brutal.
0:33:31 > 0:33:37But this strange tree has a strategy to survive it.
0:33:41 > 0:33:45The Dragon's Blood tree.
0:33:49 > 0:33:53The key to their success lies in their bizarre shape.
0:33:53 > 0:33:57They live on the mountain tops where there's little soil,
0:33:57 > 0:34:00but there are critical compensations.
0:34:04 > 0:34:08Occasional morning mists sweep across the high ground.
0:34:16 > 0:34:21The mist condenses on the skyward-pointing waxy leaves.
0:34:26 > 0:34:32The droplets run down to the centre of the trunk and down to its roots.
0:34:37 > 0:34:42Water is so precious that the tree cannot afford to waste any.
0:34:47 > 0:34:52Drops that do escape and fall to the ground are not totally lost.
0:34:56 > 0:35:01The tree's huge, densely packed crown acts as a parasol.
0:35:04 > 0:35:10It shades the ground so effectively it allows time for the water to seep into the sand.
0:35:15 > 0:35:17And it also shades the network of roots
0:35:17 > 0:35:20that lie just under the surface.
0:35:23 > 0:35:26Another plant shares this parched desert,
0:35:26 > 0:35:28but survives in a very different way.
0:35:31 > 0:35:33The Desert Rose.
0:35:35 > 0:35:37In really harsh conditions,
0:35:37 > 0:35:41it jettisons its leaves to minimise water loss.
0:35:41 > 0:35:46Strangely, it chooses this time to flower.
0:35:46 > 0:35:52Its bulbous trunk is like a barrel that stores water all year round.
0:35:56 > 0:35:59It's so hardy it can grow out of bare rock.
0:36:04 > 0:36:07It might seem that conditions can't get much tougher
0:36:07 > 0:36:08for a plant than here.
0:36:12 > 0:36:15But, for some, the conditions are even harsher.
0:36:20 > 0:36:23Six hours ago, here on the coast of Australia,
0:36:23 > 0:36:26this tree was high and dry on a sandy beach.
0:36:28 > 0:36:31For almost all plants, saltwater is lethal,
0:36:31 > 0:36:34so submersion of this tree's roots by the tide twice a day
0:36:34 > 0:36:35should kill it.
0:36:43 > 0:36:47Yet this Red Mangrove is flourishing.
0:36:53 > 0:36:58The retreating tide reveals the key to surviving the sea's assault.
0:37:01 > 0:37:05The mangrove's roots are covered in warty growths.
0:37:05 > 0:37:10The growths surround pores that take in oxygen from the air
0:37:10 > 0:37:12when the roots are above water.
0:37:18 > 0:37:24But the pores become useful in a quite different way when they're submerged again.
0:37:28 > 0:37:31They allow water into the plant,
0:37:31 > 0:37:36but filter out 99% of the salt as it passes through.
0:37:39 > 0:37:46Any salt that gets in is pumped into a few sacrificial leaves that turn yellow and are discarded.
0:37:54 > 0:37:59Plants can not only cope with being poisoned, parched and scorched,
0:37:59 > 0:38:02but they can also survive being frozen.
0:38:02 > 0:38:05In the world's northern forests,
0:38:05 > 0:38:09the changing of the seasons creates its own challenges.
0:38:21 > 0:38:23As summer moves to autumn,
0:38:23 > 0:38:27plants prepare themselves for the toughest time of their year.
0:38:31 > 0:38:36Broad-leaved trees unveil what seems to us a colourful spectacle.
0:38:36 > 0:38:43But for these plants it is the beginning of a series of urgent and drastic survival strategies
0:38:43 > 0:38:45to cope with the coming cold.
0:38:46 > 0:38:52They begin by pulling all the water and nutrients within their leaves back into the trunk.
0:38:54 > 0:38:58The last rays of useful sunlight are channelled
0:38:58 > 0:39:00into making a sugary anti-freeze
0:39:00 > 0:39:03that will protect the body of the tree.
0:39:06 > 0:39:09The green pigment - chlorophyll -
0:39:09 > 0:39:14disappears, leaving purples, reds, oranges and yellows.
0:39:14 > 0:39:18Finally, the leaves die and the trees discard them.
0:39:27 > 0:39:30As temperatures drop below freezing,
0:39:30 > 0:39:33the plants of broad-leaved forests settle down
0:39:33 > 0:39:34to hibernate until spring.
0:39:48 > 0:39:53Pine trees can survive much colder conditions.
0:39:55 > 0:39:58They have anti-freeze in the leaves themselves,
0:39:58 > 0:40:01that means they can keep them all winter.
0:40:03 > 0:40:06The needle-like leaves also have a thick waxy coating
0:40:06 > 0:40:09that limits any water loss through pores.
0:40:11 > 0:40:14The winters here are long and hard.
0:40:16 > 0:40:23The trees have to survive temperatures of down to -40C for five months.
0:41:10 > 0:41:16But one pine tree is capable of surviving even harsher conditions.
0:41:20 > 0:41:23These pines live at the limit of life -
0:41:23 > 0:41:28above 3,000 metres in the mountains of western America.
0:41:29 > 0:41:34Almost continuous freezing temperatures and savage winds
0:41:34 > 0:41:37make life so tough that these bristle cones
0:41:37 > 0:41:40only manage to grow for six weeks of the year.
0:41:43 > 0:41:46Everything is about conserving energy.
0:41:46 > 0:41:52They hardly ever shed their needles, which can last more than 30 years.
0:41:52 > 0:41:56After centuries of being blasted by storms,
0:41:56 > 0:41:59a full-grown tree still survives
0:41:59 > 0:42:02with only a strip of bark a few inches wide.
0:42:07 > 0:42:12These trees live life at such a slow pace that they can reach great age.
0:42:12 > 0:42:15Some are over 5,000 years old.
0:42:19 > 0:42:21It's been said of the bristlecones,
0:42:21 > 0:42:25that to live here is to take a very long time to die.
0:42:34 > 0:42:36As the northern spring approaches,
0:42:36 > 0:42:39the warming temperatures and increased day length
0:42:39 > 0:42:41release the land from winter.
0:42:47 > 0:42:51Plants that have lain dormant begin to grow again.
0:42:58 > 0:43:00These have over-wintered,
0:43:00 > 0:43:03buried in the mud at the bottom of this frozen lake.
0:43:13 > 0:43:16The retreating ice allows the water to warm
0:43:16 > 0:43:20and this white water lily to flourish for another season.
0:43:36 > 0:43:40And, as all the trees come out of their winter rest,
0:43:40 > 0:43:43the vivid green of new leaves returns to the land.
0:44:05 > 0:44:09From the frozen north to the southern deserts,
0:44:09 > 0:44:12the spring bloom symbolises the success of plants
0:44:12 > 0:44:15in surviving against the odds.
0:44:41 > 0:44:44But the most successful type of flowering plant
0:44:44 > 0:44:49is one that makes up 20% of all plant life on the planet.
0:44:51 > 0:44:52Grass.
0:44:54 > 0:44:57There are 10,000 different species.
0:45:02 > 0:45:07Today, they form the diet of many thousands of different animals.
0:45:12 > 0:45:15And a few grasses, particularly rich in nutrients,
0:45:15 > 0:45:19have developed a relationship with one animal
0:45:19 > 0:45:22and together, the two have changed the world.
0:45:33 > 0:45:3710,000 years ago, we humans started to cultivate rice
0:45:37 > 0:45:41in order to harvest its food-rich seeds.
0:45:48 > 0:45:52Now, half of the world's population depends on it.
0:46:01 > 0:46:04But there is one other grass that has spread
0:46:04 > 0:46:07even further across the planet
0:46:07 > 0:46:10due to its relationship with humans...
0:46:10 > 0:46:11wheat.
0:46:16 > 0:46:20It underpinned the development of western civilisation.
0:46:30 > 0:46:35Today, it covers more of the land than any other kind of plant.
0:46:42 > 0:46:46Plants have been residents on land longer than animals
0:46:46 > 0:46:49and have had nearly half a billion years to evolve.
0:46:53 > 0:46:57During that time, they've diversified into countless forms
0:46:57 > 0:46:59and have colonised every habitat.
0:47:09 > 0:47:12As well as collaborating with animals,
0:47:12 > 0:47:14plants are sometimes their masters,
0:47:14 > 0:47:17exploiting them to their own advantage.
0:47:29 > 0:47:32Plants capture energy from the sun
0:47:32 > 0:47:37and all life on land, directly or indirectly, depends on them.
0:47:37 > 0:47:43So, ultimately, plants fuel the diversity of life on Earth.
0:47:54 > 0:47:58To see the behaviour of plants as they struggle to survive
0:47:58 > 0:48:00presented a unique challenge.
0:48:07 > 0:48:09The plants team had to employ many techniques,
0:48:09 > 0:48:13including time-lapse and high-speed photography.
0:48:17 > 0:48:20They filmed in jungles, deserts, swamps and plains,
0:48:20 > 0:48:25but they also spent many hours shooting in a converted barn
0:48:25 > 0:48:26just outside Exeter.
0:48:38 > 0:48:40All under the watchful eye
0:48:40 > 0:48:44of green-fingered cameraman, Tim Shepherd.
0:48:47 > 0:48:50Filming plants in time-lapse takes so long
0:48:50 > 0:48:54and is so susceptible to changes in light levels and weather conditions
0:48:54 > 0:48:58that some key sequences had to be filmed in this studio.
0:49:04 > 0:49:07In time-lapse, a camera takes a series of pictures
0:49:07 > 0:49:10over an extended period of time,
0:49:10 > 0:49:14so, when played back, the action appears speeded up.
0:49:14 > 0:49:18These sunflowers actually take three days to open,
0:49:18 > 0:49:21but are seen opening in a matter of seconds.
0:49:27 > 0:49:30The most complex time-lapse the team attempted
0:49:30 > 0:49:32showed an entire growing season
0:49:32 > 0:49:35in an English woodland in one continuous shot.
0:49:35 > 0:49:38A shot that took two years to create.
0:49:46 > 0:49:48I think this is going to be the spot.
0:49:50 > 0:49:52As the producer, Neil Lucas
0:49:52 > 0:49:55leads Tim and Mick Connaire, the graphic designer,
0:49:55 > 0:49:57out to the location,
0:49:57 > 0:49:59he explains his idea.
0:49:59 > 0:50:02- Well, this is one that I thought... - That's a lovely rock.- Just here.
0:50:02 > 0:50:06And I think that'd be great to have the brambles growing along.
0:50:06 > 0:50:10It will be a tracking shot through the wood with plants growing,
0:50:10 > 0:50:13flowers blooming and the woodland coming to life
0:50:13 > 0:50:15over the course of a year.
0:50:15 > 0:50:18We're condensing one year down into less than a minute.
0:50:18 > 0:50:22We have to have them all coming out at the same time, multiple passes.
0:50:22 > 0:50:25How long does a foxglove take to grow?
0:50:25 > 0:50:28Well, if we start just before the buds are about to open
0:50:28 > 0:50:30and you've got the whole long spike,
0:50:30 > 0:50:33then top to bottom that's probably about three weeks.
0:50:33 > 0:50:36So, even if you wanted to, you couldn't shoot the plants here
0:50:36 > 0:50:39because, three weeks, the weather's going to change,
0:50:39 > 0:50:44you've got the day-night and also just leaving the equipment here running, it's not feasible, is it?
0:50:44 > 0:50:48You just have to imagine the changes that would happen here in three weeks
0:50:48 > 0:50:50and if that was all joined together
0:50:50 > 0:50:52and one frame the plant might be there
0:50:52 > 0:50:55and you take a shot of it an hour later and, if the wind's blowing,
0:50:55 > 0:50:59it's over here somewhere and then you join those two shots together...
0:50:59 > 0:51:04It just won't work. So what we've got to do is not only have we got to produce a move
0:51:04 > 0:51:07that is exactly the same repeatable move,
0:51:07 > 0:51:10a track that can be built exactly the same again in a studio.
0:51:10 > 0:51:12Build exact models of every object in here
0:51:12 > 0:51:16so we can put plants in the right places and then time everything,
0:51:16 > 0:51:20- so they grow just as the camera happens to be pointing at them. - Yes.- OK.
0:51:20 > 0:51:23The scale of the challenge is dawning on them.
0:51:23 > 0:51:25Months of planning lie ahead.
0:51:29 > 0:51:32The following spring, the team head back to the wood.
0:51:32 > 0:51:33With no road access,
0:51:33 > 0:51:38manpower is the only way to get the tonnes of equipment into position.
0:51:45 > 0:51:50Everyone's wondering how this will turn out, including the locals.
0:51:59 > 0:52:01- Go up about an inch.- Straight now.
0:52:04 > 0:52:05Start like that.
0:52:11 > 0:52:13Position now is 221556.
0:52:16 > 0:52:18We've done it wrong.
0:52:25 > 0:52:28That's pulled it. Hang on - that's pulled it terribly.
0:52:30 > 0:52:32BLEEP!
0:52:33 > 0:52:37- Did that snap? - No, it's pulled this wheel round.
0:52:40 > 0:52:44Two days of building, levelling, test runs
0:52:44 > 0:52:46and even a few minor disasters
0:52:46 > 0:52:49and finally the track is ready to run.
0:52:49 > 0:52:52OK, that's pretty close.
0:52:52 > 0:52:59If you move your... Can you see that little bit of lichen? Go to 8,900.
0:53:01 > 0:53:03Accuracy is paramount.
0:53:04 > 0:53:06Yeah, whatever we shoot in the studio,
0:53:06 > 0:53:09it's got to match this landscape exactly,
0:53:09 > 0:53:11so unless we know precisely where everything is
0:53:11 > 0:53:13relative to the camera,
0:53:13 > 0:53:17there's no way of placing the plants in the studio in the right place.
0:53:17 > 0:53:19So we have to measure the hell out of it.
0:53:19 > 0:53:22Oh, bloody hell, it's spot on. Look at that.
0:53:22 > 0:53:26- So 250.- OK.
0:53:33 > 0:53:35Shot by shot and step by step,
0:53:35 > 0:53:39the camera inches its way back up the 30 metre track.
0:53:39 > 0:53:41Well, that's working.
0:53:45 > 0:53:47This is only the background shot.
0:53:47 > 0:53:50There is still a huge amount of other filming to be done.
0:53:53 > 0:53:57The track has to be rebuilt exactly as it is on location
0:53:57 > 0:54:01back in the studio - a task that will take weeks to get right.
0:54:18 > 0:54:22Right in front of the tree at the end of the rock.
0:54:25 > 0:54:27Using the detailed measurements taken in the wood,
0:54:27 > 0:54:31the position size and shape of every structure
0:54:31 > 0:54:32has to be matched precisely.
0:54:36 > 0:54:39- 35.- 35, yeah.
0:54:42 > 0:54:48The slightest discrepancy will put the team back to square one.
0:54:48 > 0:54:54Chicken-wire and polystyrene form the rocks and trees of the woodland.
0:54:54 > 0:54:58Blue screen is used to cover every inch of the set
0:54:58 > 0:55:03to allow the original shot to be mapped on later in graphics.
0:55:03 > 0:55:06Once built, and with the plants placed in their exact locations,
0:55:06 > 0:55:07filming can start.
0:55:09 > 0:55:12The stars of the show finally make an appearance.
0:55:32 > 0:55:33Timing is everything.
0:55:33 > 0:55:36With each plant taking up to three weeks to flower
0:55:36 > 0:55:39there's only one chance of getting it right.
0:56:03 > 0:56:08A year later and thankfully so far all had gone to plan.
0:56:16 > 0:56:20The final stage is to bring all the pieces together seamlessly -
0:56:20 > 0:56:23a challenging task for any graphic designer.
0:56:23 > 0:56:27We've got things overlapping that wouldn't necessarily grow at the same time,
0:56:27 > 0:56:30but all the growth of each individual plant is absolutely accurate.
0:56:30 > 0:56:32It's exactly what they would do.
0:56:32 > 0:56:35We're just seeing it in a shorter space of time.
0:56:35 > 0:56:40That big rock in the foreground at the end of the shot that we wanted to try and get stuff climbing on,
0:56:40 > 0:56:42that's worked really, really well.
0:56:42 > 0:56:43This is the bramble here.
0:56:43 > 0:56:49Had to measure it so carefully so we knew exactly where these things were, how round they were,
0:56:49 > 0:56:50how deep they were from the camera.
0:56:50 > 0:56:53Then when we take the blue out of that
0:56:53 > 0:56:55you can see that the plants start to sit into the shot
0:56:55 > 0:56:57exactly where we wanted them to be,
0:56:57 > 0:56:59things appearing from behind the tree,
0:56:59 > 0:57:01forming on the top of the rock.
0:57:01 > 0:57:03- That's fantastic.- So here they go.
0:57:03 > 0:57:04If I switch those off
0:57:04 > 0:57:07you can see how just how neatly they slot into the shot.
0:57:07 > 0:57:09If we play it, you can see
0:57:09 > 0:57:14that everything's sticking in pretty well.
0:57:16 > 0:57:2396 layers, 15 tracks and two years later, the shot is finally complete.
0:57:27 > 0:57:31A 60-second shot that proved to be one of the most complex
0:57:31 > 0:57:34ever attempted in natural history film-making.
0:58:10 > 0:58:14Subtitles by Red Bee Media Ltd
0:58:14 > 0:58:17E-mail subtitling@bbc.co.uk