The Private Life of Plants (1995–…): Season 1, Episode 1 - Travelling - full transcript

Midwinter - and the countryside is
so still it seems almost lifeless.

But these trees and bushes and grasses around
me are living organisms, just like animals,

with the same sort of problems as animals
face in their lives if they are to survive.

They have to fight one another;
they have to compete for mates,

and they have to invade
new territories.

We are seldom aware of these dramas because
plants live on a different timescale.

But these days we have ways
of speeding things up visually -

and you can see just how dramatic
the lives of plants can be.

Condense three months
into 20 seconds,

and the desolation of winter quickly
warms into the riot of spring.

Speed a week into a minute -



and you can sense the urgency with which the
ground-living plants race to unfurl their flowers.

Wood anemones nod attentively at the
sun as it rises and sets each day.

Above, hazel leaves,
moving to the same rhythm,

pulse as they expand
to their full size.

Beneath them, the broad leaves of
clocks are rising from the ground.

Foxgloves gape almost alarmingly as they invite
insects to come and collect their pollen.

Strange though it may seem, some plants can
move not just their flowers and leaves,

but can travel from place to place.

Take, for example, this bramble.

Of all the woodland plants,

this is one of the most aggressive.

It waves its shoots agitatedly from side to
side as if feeling for the best way forward.

And when a shoot settles on its course,
it thrusts ahead relentlessly.

The stem's backward-pointing
spines give it the grip it needs



to climb over almost anything
that stands in its way.

It can advance as much as
three inches in a day.

The shoot will put down rootlets

and new territory will be annexed
to the bramble's empire.

Other adult plants
travel even faster.

The birdcage plant
lives in California,

but the desert dunes are always
moving and a site becomes exposed,

so the plant must find a new place.

This plant is now dead,
but within it there is still life.

These tiny particles
are the next generation.

Each contains complete genetic instructions
for rebuilding an adult plant like this.

These small grains are the reason most
plants do most of their traveling.

Some of these genetic particles
are, in fact, microscopic.

Smallest of all belong to fungi.

Fungi are not, to be accurate,
plants at all -

they belong to a kingdom
on their own -

but their spores are in many ways
similar to seeds.

A single puffball produces so many that someone
has calculated that if, for two generations,

every spore grew into an adult,
the resultant mass of puffballs

would be 800 times
the volume of the earth.

Like the birdcage plant, a puffball
can be carried along by the wind,

but the real traveling is done by the spores
that are knocked from it in clouds, like smoke.

In autumn, other smaller fungi
appear on the woodland floor.

Earthstars.

Their appearance when they emerge gives
little hint of how complex they will become.

In the damp autumn air,
the earthstars transform themselves.

They open at this time of the year to
take advantage of the falling rain.

A drip gives them the energy

to propel their spores
into the air.

Flowers also use the wind
to transport their seeds

and few do it more successfully
than dandelions.

As their petals fall their flower heads,
over a period of one or two weeks,

are transformed
into wonderfully intricate globes,

each a precise array of a hundred
or so seeds, all awaiting the wind.

Their seeds are much heftier
than the spores of fungi.

For them to fly,
special apparatus is needed.

Each is fitted with its own
individual parachute.

It is so efficient that a breeze
carries the seeds high into the sky.

In this dense crowd of adult plants,

there's no room
for the next generation.

The seeds must get away, and the
wind will take them for miles.

Trees have a particular advantage when
dispatching their seeds by air - their height.

The farther it falls,
the farther it travels.

And these cottonwood trees

need only provide their seeds
with straightforward fluff.

But this, because of their height,
is enough to carry them for miles.

Every summer, the waters of the Great Lakes
of North America become thickly flecked

with cottonwood seeds
around their margins.

A few will wash up
on distant shores and germinate.

Most will be lost. But the seeds are so
numerous it's of no consequence whatever.

There is much less wind
in the tropical rain forest.

The humid air hangs as a mist,

while below, there is seldom
even a breath in the air.

A plant here has to give its seeds
very good flying equipment indeed.

And none does that better
than this Liana in Borneo.

Aircraft designers have tried to build a wing
as efficient as this this one - but failed.

Even the faintest updraught produced
by the slightest thermal

is enough to lift this little glider with
its seed passenger, and so extend its flight.

Plants preceded humanity in building
fixed-wing gliders - and not only gliders.

They created helicopters too...

...sycamore seeds.

The balance between the weight of the seed and
the length and width of the wing is perfect.

A slightly heavier seed
or a shorter and narrower wing

and the whole thing
would fall like a stone.

The tri-star plant produces
a revolving seed with six blades -

and aircraft designers
have yet to copy that.

Or this.

Plants also use explosives...

"jet Propulsion.

This is a squirting cucumber.

And this - Himalayan balsam.

Its seed capsules are pumped
full of liquid to such a pressure

that the slightest touch
makes them explode.

The force is so great

that seeds can be shot away
for as much as fifteen feet.

Mesembryanthemum seed heads
are opened by rain.

It's the sudden absorption of water

that powers their opening.

Once open, they expose a screen
as taut as a trampoline.

Raindrops bounce off it,
taking the seeds with them.

Water provides many plants with the
power they need for traveling.

It can shift really heavy,
bulky ones.

Beside many tropical rivers, there hangs
the biggest of all seed pods - the sea bean.

These huge containers house one of the most
successful of all vegetable travelers.

There is a groove between each seed, so that
each can fall away in its own separate packaging.

One by one, the sea beans
start on their voyages.

This one is setting off
down a small river in Africa.

After a few miles -
perhaps even a few hundred miles -

the seed arrives at the mouth of its
river and makes its way to the sea.

It can voyage through groups of
islands and out into the open sea

to ride the great ocean currents for as
much as a year and still remain alive.

Its protective packaging

may become so frayed and tattered that
it disintegrates and releases the seed.

But it's not a disaster, for the
seed is able to float by itself.

Many, doubtless, are lost at sea. But some eventually
reach another - and maybe a distant - coast.

One has landed on a tropical beach
in northern Australia,

I've no idea where it came from. It could
be from a tree a few miles up the coast,

or from another continent. Sea beans land on the
coast of Europe, having come with the Gulf Stream.

Of course it's too cold for them
there and they seldom germinate,

but if they land in the tropics, they will almost
certainly grow. There's one on this very beach.

So, some plants send their seeds
by sea, some by air.

But most, in fact,
use living couriers.

Animals with hairy coats

are easily conscripted.

The burdock uses hooks -
hundreds of them.

And very effective they are.

Eventually the burrs are licked off,

picked off, or shaken off.

If the burdock is lucky,

that will happen some distance
from where the adult plant grew.

Trousers will serve just as well
as hairy coats,

and shoes as hooves or paws.

Here, in southern Africa, there is a
creeper that uses not hooks but spikes.

These things are called by the local
people 'devil thorns' and you can see why.

If an animal or human trod on that with
a naked foot it would be very painful.

But if you think that's bad,
what about this?

This is the seed case
of the grapple plant.

Animals with cleft hooves
or relatively soft pads

can be crippled by the grapple plant,
but the bony, scaly feet of ostrich

are particularly tough.

They can carry this vicious
hitchhiker for many miles

without any ill effects.

But there's another way
of treating messengers.

Instead of relying
on chance encounters with them,

you can tempt them with rewards.

Many plants in these
dry heathlands

engage ants as carriers by attaching
ant food to their seeds.

If a seed lies out in the open
for long here,

a mouse or some other rodent
will eat it. If it's to survive,

it must get below ground quickly.

And the ants take it there.

The fleshy bit at the end
is all the ants want.

So the seed has now reached
a safe resting place

just below the surface
of the ground.

Plants bribe us too. And they make
us fit in with THEIR timetable.

This blackberry, for example,
is not yet ready for my services.

But as the flesh around the seeds sweetens,
it announces the fact by changing color.

The blackberry's seeds
will be more widely distributed

if the plant is visited by a
succession of different messengers

so its berries
do not all ripen simultaneously.

Birds find them irresistible,

and quickly spot them. For black is a very
conspicuous color. And so, too, is red.

Birds see color
the same way as we do.

What is vivid to them
is vivid to us.

So rowans and yews,
strawberries and plums,

cherries and hawthorns, use red or black
to summon birds to collect their fruit.

Tropical figs produce much smaller
fruit than their European relative,

and they turn yellow. Even so, their
message is widely understood.

A tropical fig tree in fruit
is a huge bonanza in the forest.

All kinds of diners come to the tree.

As well as fruit-eating birds,
they attract all kinds of mammals -

monkeys, squirrels and gibbons.

The rhinoceros hornbill,
with its huge beak,

has to be a bit of a juggler.

Now comes the important part.

Dozens of fruits containing hundreds of seeds
are ferried miles away in the hornbill's crop.

The flesh of the fruit
will be digested

and the seeds will be voided
in a distant place in the forest.

All forest canopies, however, do not have such
a rich variety of fruit eaters as in Borneo.

In New Guinea, there are very few
mammals and no monkeys at all.

The biggest creature on the ground
is not an antelope or a great ape.

It's a bird - the cassowary.

Both male and female cassowaries have vividly
colored wattles, and the similarity between them

and the fruits
may not be coincidence.

The wattles serve as social signals
between the birds.

Did plants adopt the same colors to call
the birds' attention to their fruit?

Or did the cassowaries make themselves
more attractive to their mates

by reminding them of a good meal?
No-one can say for sure.

What is certain is that cassowaries have no difficulty
finding objects with these colors among the leaves.

Visual signals, however, have their
limitations as advertisements.

In thick forest, you just can't see
them unless you are quite close.

But there is another medium - smell. It's less
precise, but it works over greater distances.

In Borneo, one fruit produces
a smell so pungent

that a sensitive nose can detect it
from half a mile away.

And some people like the taste of that fruit
so much that they walk miles to find it.

And so will others.

This is it - the famous durian.

I have to say that the smell, to my
nostrils at any rate, is fairly disgusting.

Like an open sewer
with just a dash of coal gas.

That's the rind. It's the advertisement.
This is the fruit.

That's very different.

It's really pretty good.

A kind of... slimy caramel creme,
perhaps, would describe it.

But if all Europeans aren't instantly
durian addicts, all orangutan are.

Animals may carry seeds for long
distances in their stomachs,

but most get rid of them at random.

For some plants,
that is simply not good enough.

The trewia tree in the forests of
Nepal has a particular problem.

Their seeds cannot germinate
in deep shade.

They have to be taken into a clearing
if they are to stand a chance -

and one animal will do that for them,

the great Indian rhinoceros.

It's so fond of these fruits

that they're called, locally,
'rhino apples'.

The rhinos usually feed in the
forest during the heat of the day,

but in the cool of the evening they
habitually move out into open grasslands.

The grasslands are created by monsoon
floods that, every few years,

wash away parts of the forest. Rhinos
visit them for the rich grazing.

And out here,
on regularly used communal middens,

they perform the last
of their daily duties.

And there, neatly deposited
with a ration of fertilizing manure,

are the seeds of the trewia.

So young trewias sprout
on the rhinos' dunghills.

Other trees will grow, and the
forest will colonize the grasslands.

Then the trewia fruit, once more, will have
a problem, and rely on the rhino to solve it.

Sadly, this magnificent animal

is getting rarer and rarer.

Over millions of years of evolution, the
trewia tree has established a link with it.

But if the great Indian rhinoceros
becomes extinct,

the trewia itself may disappear from the
grasslands and riverbanks of southern Nepal.

In Africa, elephants - similarly - have
become crucial partners for acacias.

That may seem surprising, for they are only
too obviously great destroyers of acacias.

For when other food is short,
they will use their great strength

to knock the trees down
to eat their branches.

But without elephants, some species
of acacia would barely survive.

Lots of animals
come to feed on acacias.

Inside the pods,
the seeds are threatened

by serious enemies.
These beetle grubs hatched from eggs

injected into the pods.

They will now eat all the seeds
unless they are stopped.

Monkeys eat pods, seeds and grubs -
chewing it all thoroughly.

The acacia gets little benefit
from providing THEM with meals.

But elephants are different.

They greatly relish the seed pods
which are highly nutritious.

They go to considerable trouble

to pick up these
fiddly little things.

But they don't grind up their food
into such a fine mash as monkeys do.

And having fed, they move on.

They may walk for several miles before, having
digested their meals, getting rid of the remains.

These acacia seeds,

have spent at least 24 hours
inside an elephant's stomach.

This has killed stone dead
those beetle grubs.

The elephant's digestive juices
have disinfected these seeds

just as efficiently as a farmer
dressing his seeds with insecticides.

Ninety percent of acacia seeds
in elephant dung germinate.

Those in pods that are left uneaten on the
ground will be killed by beetle grubs.

So acacia seeds eaten by an elephant have not merely
been transported, but saved from near-certain death.

Some seeds, however, are so well-protected
that it seems that nothing could eat them.

These capsules,
as hard as cannon-balls,

contain the individual seeds -
the nuts -

of the Brazil-nut tree.

Even a fall of a couple of hundred
feet doesn't crack them.

Only one animal has the equipment
to open them - the agouti.

The agouti has two pairs of front
teeth that are as sharp as chisels

and they enable it to gnaw a hole into
the capsule and get at the seeds.

But the Brazil-nut tree protects
its seeds from the only animal

that has penetrated its armor.

It presents it with 15 or 20 nuts - far more than
an individual agouti could eat in one sitting.

And the agouti has a habit which suits the Brazil
nut. It buries what it can't eat, for later.

What it doesn't have
is a perfect memory. It loses track.

And a significant proportion
of the nuts survive to sprout.

The Alpine nutcracker - a kind of crow - is an
even more obliging partner for the arolla pine.

The bird knows exactly how to open the
cones and pick out the ripe seeds.

Each one is swallowed, but it doesn't go
into the stomach. It's stored in the crop,

while the bird tackles the next.

Then, like the agouti, the bird hides them,
one by one, as provisions for hard times.

But, unlike the agouti, it carries the
seeds away from the forest onto open ground,

perhaps because there it can
more easily memorize landmarks

to help it find the seeds again
months later.

These places
suit the young trees very well.

One by one, the bird brings them up
from its crop.

It buries them
at a depth that suits the seed.

Then it fills in the hole
to conceal its treasure.

So the seeds of the arolla pine are
carried far from the parent tree

and planted with all the care that
a human forester might give them,

not only in high alpine meadows,

but even high up
on the mountain ridges.

Yet some plants succeed in reaching
seemingly inaccessible sites

without the help of any animal

and entirely by their own exertions.

A crack in a wall fifty feet above
the ground is not easy to reach.

But the ivy-leaved toadflax,
nonetheless, manages to get there.

It has no suckers like Virginia
creeper or clinging roots like ivy.

Its colonies manage to advance
up the wall, from crack to crack,

in an entirely different way.

As the petals fall off, the seeds in
the capsule beneath begin to develop.

Then the toadflax behaves
in a most remarkable way.

It finds the nearest crack
and plants its seeds itself.

So, plants manage
to get their seeds

to the best places to germinate.
But what is the best time?

These protea growing here
on the southern tip of Africa

have had their seeds inside the
seed pods for several years now.

The time to release them
is about to arrive.

The several species of protea growing here
all depend upon the arrival of seasonal fires.

The fire has killed all the
adult plants on this land,

so this is an excellent time for seeds to
germinate. There are no established competitors.

In fact, it's the ONLY time
protea seeds can germinate,

because these seed heads have to
be burnt to release their seeds.

An hour or so after scorching,
the heads open.

All around lies a rich ash,

which makes a nutritious bed
for the seeds.

Protea seeds can remain inert and
apparently lifeless for many years

and then spring into life when conditions
are right. Some will die after 2 or 3 years.

But others are able to remain alive
for astonishing periods.

One of the most remarkable examples comes
from an archaeological site here in Japan.

Two thousand years ago
a small settlement,

with buildings like these,
stood at a place called Asada.

The people who lived here
in such houses

had only just begun to master the art of
working metal. They also knew how to plant rice.

They stored their harvest
in small pits.

In one of those pits
they found some seeds, like these.

These are rice grains -
obviously dead.

But this is a magnolia seed.

Scientists took away that strange,
ancient seed, planted it - and it grew.

At first it looked like Magnolia kobus, the
wild species that still grows in Japanese woods.

Then, in its tenth year,

it produced its first flower buds. These, when
they opened, would reveal exactly what it was.

Magnolia kobus today, typically,
has six petals on its flowers.