The Private Life of Plants (1995–…): Season 1, Episode 3 - Flowering - full transcript

HE SNEEZES

The English summer fills our landscape with lovely
flowers, but it comes at a price - hay fever.

For those of us who suffer from it,
and I certainly do,

our eyes swell, our nose runs and we get
overcome with fits of uncontrollable sneezing.

The source of our affliction is in
the air all around me: pollen grains.

No bigger than specks of dust, they are
astonishingly varied and complex in shape.

Each species of plant
has its own characteristic pattern.

They are shed in millions from stamens that
tumble out of the grass's tiny flowers.

As the grains are released,
so the wind carries them away.

It's these tiny particles, when they get up our
nostrils, that give so many of us such a bad time.

But their proper destination
is not the human nose,



it's structures like these,
the stigmas of other grass flowers.

When a pollen grain happens to land on one of
these feathery traps, a grass plant is fertilized

and can then produce seeds which
will grow into other grass plants.

You might think that such a method of distributing
pollen would be wasteful and inefficient,

but grasses are
extraordinarily successful.

They've spread to every continent on earth
and some of them have grown very big indeed.

These in Nepal
are the biggest of all,

standing twenty feet tall.

Human beings, even rhinoceroses, could move around
in these meadows and still be totally concealed.

Hazel, like many trees, also relies
on the wind to distribute its pollen.

Because pollen is produced in vast
quantities and discharged wholesale,

it and the structures from which it comes,
like these catkins, are regarded as male.

The female structures, the stigmas, grow
separately on the hazel as tiny pink sprays.

At the base of each stigma, there's a chamber
holding a small number of eggs - in hazel, only one.



Although many pollen grains may fall on a
stigma, only one is needed to fertilize each egg.

It develops a microscopic tube which grows down through
the stigma and unites with the egg at the bottom.

This then swells
and becomes a hazelnut.

Most plants, however, combine their male
and female structures into one flower.

The stigma is usually in the center and the
pollen-producing stamens are clustered around it.

The petals are advertisements
to attract animal messengers

who will carry the pollen
from one flower to another.

Many flowers,
like this wild geranium,

ripen their male and female structures at
different times to prevent self-fertilization.

First, the stamens curl back and release
pollen from the containers at their tip.

Only then
does the white stigma open.

Now it can receive
pollen from another plant.

The Australian kangaroo-paw flower
produces its stamens in a line,

with the thinner, longer stigma
projecting in front of them.

The flowers grow in a spike and open in succession
to offer visiting animals a drink of the sweet nectar

that each holds in its depths.

And when a honey-eater reaches down
with its beak to collect that nectar,

it gets pollen
over the back of its neck.

And then, when the bird
goes to drink elsewhere,

the stigma of the second plant is
brushed with the pollen from the first.

In South America, hummingbirds are great nectar-drinkers.
Flowers load them with pollen in similar ways.

The stamens of this one
are clustered into a brush.

And on goes the pollen.

Many of these bird-pollinated
flowers are red.

This is not just a coincidence. Birds
have a color vision much like our own.

Red draws their attention
as quickly as it draws ours.

This South American plant, columnea, at first sight has
no bright colors, but look at its leaves from beneath.

They have translucent blotches
and the light shining through them

gives them the scarlet brilliance
of stained-glass windows.

The flowers, close to the stem, are
pale, small and easily overlooked.

But hummingbirds have learned
that the leaf blotches are signposts.

In some ways, this is a better way
of advertising than using petals.

The red patches on the leaves
are more economically produced,

they last longer than petals and
advertise a succession of flowers.

It's a good guess that a red,
robust, trumpet-shaped flower,

no matter where you find it,
will be bird-pollinated.

These aloes are in South Africa
and this is a sunbird.

There's another prediction
you can make about flowers.

Not only are prominent red flowers
likely to be pollinated by birds,

but they're unlikely
to have any scent. This aloe hasn't.

The reason is birds, with very few
exceptions, lack a sense of smell.

Perfume would be wasted on them.

Color is all they need to attract their
sharp-eyed, red-sensitive pollinators.

This aloe, like many in the family, ripens
its stigmas at the same time as its stamens

so you might think that the plant
was in danger of fertilizing itself.

But aloes' stigmas are able
to recognize their own pollen

and will only accept pollen
from other plants.

Proteas, another South African
plant family, like aloes,

produce a multitude of small flowers
clustered together.

But they pack them even more closely so that several
hundred tiny florets form a single spectacular bouquet.

Those in the center may produce
stamens and stigmas and nectar,

while those around the outside are sterile
and serve only as advertisements.

So proteas produce spectacular
flower heads of great variety

and provide their pollinating birds with a
large number of individual sips of nectar.

But a few are different.

This too is a protea.

At first sight, it may be difficult
to believe, but it is in full bloom.

The flowers are not perched on top.
They're down here.

They're brown, they point downwards and, in
the evening, they develop a yeasty smell.

They're obviously not suited
for pollination by birds.

To discover what does pollinate them,
you have to watch them after dark.

A little bush mouse.

The banquet won't last long,
for the flowers will soon be over.

Then the mouse will go back
to its normal diet of seeds.

By that time, it will have carried pollen
from one plant to another on its nose,

all that the protea requires
as payment for the meal.

The durian tree of Borneo also blooms at
night and is also tended by nocturnal mammals.

Fruit bats.

They rival birds in their
effectiveness as pollinators.

They, too, will fly great distances
to find food.

Mammals were the most recent group
of creatures to evolve.

Before them, the reptiles ruled.

Some of them during the time of the dinosaurs would
be conscripted by plants as some are still today.

The giant gecko of New Zealand
is one.

The islands have no native mammals, except bats, so
plants have limited candidates for the job of courier.

The gecko has been recruited
by the pohutukana tree.

Dawn in Madagascar.

Madagascar split away from the eastern
flank of Africa some 40 million years ago

and it's been isolated ever since.

Because of that, it has plants
that are found nowhere else.

The spectacular traveler’s palm
is one of them.

It produces its flowers in sprays that
sprout between the leaves of its great fan.

They are drab, stiff,
almost leathery structures.

You have to be pretty strong to pull these hefty
petals apart to reach the nectar they conceal.

But the island not only has unique
plants, it has unique animals.

Lemurs.

They have all the strength
that is necessary.

There are many kinds of lemur but only
a few have taken to nectar feeding.

The black lemur is one of them.

Its name is misleading. The males
are black but the females are brown.

They have much longer tongues
than nectar-teetotaller lemurs

and that enables them to drink
from the palm's deep nectaries.

Being dusted with pollen
is only half the payment required.

The pollen must also be delivered to the flower of
another traveler’s palm, which may be miles away.

But the lemurs move great distances and once
they have drained the nectar from one palm,

they try and find another.

Only when they have drunk
from a second traveler’s palm

will they have completed the task
given to them by the first.

But the most widely used messenger service is
supplied neither by mammals, birds nor reptiles,

but by insects.

In many ways, they provide the cheapest
and most efficient courier service.

A plant like this Indian balsam can summon them
with quite small, economically produced flowers.

Each individual messenger, such as this bumblebee,
will do its work for quite a modest payment of nectar.

The balsam constructs its flowers in a way that ensures
that no-one gets a drink without getting a load.

It holds the nectar deep in the flower so
that the bee has to go right inside to get it.

The stamens hang from the roof of the entrance.
An arriving bee brushes them with its back.

And when all the pollen has gone, the stamens loosen
so that a departing messenger knocks them off.

That exposes the stigma so that the next
thirsty bee that arrives to collect a drink

will make not a collection
but a delivery.

Dozens of pollen grains get caught on the
sticky stigma, many more than are needed.

And when the flower's function
is over, the petals fall,

then the egg chamber at the base of each flower
quickly swells and becomes a capsule full of seeds.

Many plants have found that it pays
to have an exclusive courier service

so that a messenger doesn't deliver its package to
a different kind of flower where it'll be useless.

This gentian, growing on the Cape in
South Africa, has adopted that policy.

The reward it offers
is edible pollen.

Carpenter bees pack great quantities
of it into baskets on their legs.

The stamens appear to be offering
yellow pollen to all comers.

But that is an illusion.

These yellow structures are hollow
tubes. The pollen is secure inside.

A beetle, attracted by the sight,
is totally baffled.

So how do the bees manage to collect
such large loads of pollen?

Well, if you listen very carefully when
one arrives, you can hear the answer.

BEE BUZZES

By vibrating more slowly than usual
and making a deeper buzz,

the bee shakes the tube with the right frequency to
make the pollen spurt out of a tiny hole at the top.

DEEP BUZZING

I can show the sort of vibration
that is needed with this tuning fork.

TUNING FORK HUMS

There!

You might think that the long stigma, growing to one
side, would collect pollen sprayed around like that.

But there's no danger of the flower
fertilizing itself.

The stigma is not receptive until
all the flower's own pollen has gone.

There's an additional advantage
with this strategy.

A bee can't tell by sight whether a yellow
stamen has pollen inside it or not,

so flowers which have no pollen left but newly
receptive stigmas get a pollen delivery without paying.

Honeysuckle rewards its employees
not with pollen but with nectar.

It keeps the payments at the end
of long tubes formed by the petals

so that a long tongue is needed
to get it out.

The hummingbird hawk moth has one.

To get the last drops, the moth has to
probe to the full length of its tongue.

And that compels it to brush
the stamens with its underside.

The flowers go on producing nectar well after their
stamens have become exhausted and have shriveled,

so the moths go on drinking
from them.

But now they brush pollen off their
undersides and onto the stigma.

Some flowers make drinking even more
difficult for their couriers.

This small iris grows in South Africa. Each
flower has a hugely elongated tubular base.

The tiny entrance to it is indicated with exemplary
clarity and absolute accuracy by these white arrows.

And here is the only tongue
that can reach that nectar.

It belongs to a hover fly.

It's not so much a tongue
as a fine tube.

In proportion to body length, it's one of the
longest feeding implements in the animal kingdom.

The clear markings
are particularly important

because the tongue is so long that even
in the lightest wind the end blows about.

An extra thrust is needed
to get the last drop.

The iris only flowers
for a few weeks.

So what does the hover fly collect with
its phenomenal tongue at other times?

Well, after this iris is over, this different
blue flower opens. It's another species of iris.

A succession of plants bloom on
the veld during the next few months

so that the hover fly is kept fed
throughout its short adult life.

The hover fly collects pollen on the front of
its broad head and on the back of its neck.

Butterflies, on the other hand, tend to
accumulate it around the base of the tongue.

They don't hold their tongue
needle-straight, like the hover fly.

They curve it and sometimes
they can put a sharp bend in it.

This butterfly has got pollen not only on
its tongue but all over its legs as well.

Pollen, however, is valuable stuff.

In terms of calories, it costs a lot
for a plant to produce.

The crassula flower
releases its pollen so lavishly

that this South African mountain pride
butterfly gets it all over its tongue.

The mountain pride
lives in the hills around the Cape.

Several red flowers grow here.

The butterfly, unusually among insects,
has a particular liking for that color

which elsewhere seems almost
the prerogative of birds.

Not only are there red crassulas,
but there are also red gladioli.

They, too, squander pollen
on the butterfly most lavishly.

But there's one flower
that has done something about that.

It loads its pollen onto the mountain pride
butterfly in a much more accurate and economical way.

It grows at the head
of this spectacular gorge.

And this is it. A red orchid.

It's got a vessel at the back here which is full of
nectar and the butterfly knows exactly where it is.

Orchids have a special way
of rationing their pollen.

They parcel it up into a pair
of packets called pollinia.

Here, they're hidden behind those
two white knobs at the top.

The white lump at the bottom
is the stigma.

Like other orchids, it provides
its visitors with a landing platform.

There's only one position in which a butterfly
can stand in order to reach the nectar.

As the mountain pride
pushes forward to get the last drop,

a pad from one of those white knobs
is glued onto its back legs.

As the butterfly moves again,
it pulls out the yellow pollinia.

When it visits its next flower, it must alight on
the landing platform in precisely the same position.

That causes the pollinia
to be dragged across the stigma.

That too is sticky.

The orchid has been fertilized.

In South Africa in spring, the veld is covered
with as spectacular a display of flowers

as can be found
anywhere in the world.

Some are advertising meals
of pollen, some drinks of nectar.

And those aren't the only
treats on offer. BEE BUZZES

This flower, a relative of the
snapdragon, has an unusual product,

a nutritious oil which it holds
at the end of two long spurs.

Only one customer, this bee, has the
right equipment for collecting it.

Its front legs are specially elongated and
thickly covered with hair which mops up the oil.

In South America, a group of orchids offers an
even more unusual and sophisticated product.

It too is an oil,
but not an edible one.

The customers for whom it's
produced are tiny, iridescent bees.

But only males visit the flowers.

The oil is very waxy and the bees have to
scrape it from a pad at the back of the flower.

It's not a food, it's a perfume.

The male bees use it to attract
females during courtship rituals.

Each species of bee
needs its own exclusive brand,

so each species of orchid tailors its product to
match the taste of its own particular customers.

But it doesn't come for free.

The surface of the orchid around the
oil pad is particularly slippery.

The males have a lot of trouble
in keeping their foothold.

One slip and he falls down a chute
to collide with a sticky knob.

It fastens onto him securely and when he struggles
free, he pulls the yellow pollinia away with him

Another orchid in this group imposes its
will on its customers in a different way.

That white rod is a trigger. Small bees
are not heavy enough to operate it.

But this one is altogether heftier.

And in a fraction of a second,
the orchid dumps its cargo onto it.

Some plants produce a reward that only one animal
seems to like or, indeed, could even reach.

This tropical fig tree in northern
Australia has a relationship with a wasp

which is so complex that it is difficult to imagine
who started it or who is getting the better bargain.

The fig tree carries its flowers
inside these small green knobs.

The only way to reach them is through
this tiny hole in the center.

Within, the cavity is lined
by both male and female flowers.

Each is little bigger
than a pinhead,

but some of the female ones
have been parasitized.

Weeks ago, a minute female wasp crawled in through
the entrance hole and laid her eggs in their ovaries.

Now those eggs are about to hatch.
First to emerge are male wasps.

They are difficult to recognize as such for
they have long, worm-like bodies and no wings.

They will never fly.
They won't even leave this chamber.

They are searching for those parasitized female
flowers that contain unhatched female wasps.

A male, having found what he seeks, mates with the
female while she is still inside the tiny flower.

He crawls away and will soon die.
His work is over.

Now the females begin to hatch.

They are more recognizable as wasps for, although they
are barely bigger than mosquitoes, they do have wings.

They head for the exit hole.

To reach it, they have to pass the fig's male
flowers, and they get loaded with pollen as they go.

Out into the open air they fly to
look for another fig tree in flower.

If they find it, they will force their way
into the little globular flower capsules

and so fertilize the fig.

Their reward for that service will be to use the fig's
flower chamber as a nursery for the next generation.

Some plants, however, do not
give their pollinators any reward.

In the warmer parts of Europe lives a whole group
that bamboozle their pollinators into thinking

that they're going to get a really
sensational reward, a sexual one.

These little orchids reproduce
remarkably closely the signals

that enable a male bee or wasp

to recognize
a female of the same species.

Several have blue patches.

One is fringed
with what looks like fur.

A wasp's wings in the right light flash iridescent
blue. Its abdomen is covered with thick brown fur.

A female wasp also pumps out an identifying
perfume but the orchid does the same.

The result is irresistible.

As the male wasp nuzzles forward
in his attempts to mate,

he butts the pollinia, which stick
to him like yellow horns.

He seems to be well aware
that something has happened to him

but there's nothing he can do about it and
he flies off to try his luck elsewhere.

This is what the orchid requires. This time he
deposits the pollen on another bogus female.

The hairs on many of these orchids run downwards
as though the female is sitting with her head up.

But some reproduce her clinging head-down so
the male must land that way if he wants to mate

and he will get the pollen
stuck to his rear.

This one, too, seems fully aware that he's
got rather more than he bargained for.

The orchids' mimicry
is so convincing and enticing

that sometimes a flower will attract
a whole scrum of sex-crazed suitors.

Some are trying to get to the orchid and
will inadvertently deliver the pollen.

Other males, since there seems to be a full
house, attempt to mate with one another.

In the heathlands of Western Australia, orchids
perpetrate an even more complex sexual charade.

This time, the victims are a particular
group of wasps known as the thynnids.

In spring, the female thynnid emerges from the
sandy soil where she's been feeding on beetle grubs.

She's ready to mate. If you burrow
it's difficult to develop wings.

She has none so she can't travel far.

But the males can, for they feed
by hunting and do have wings.

They will have to come to her.

Once settled, she begins
to emit a message of perfume

that is detectable for a long
distance downwind. Then she waits.

And usually not for long.

The male carries her away
and will mate with her in mid-air.

This, however, is plainly not,
to our eyes, a wingless female wasp.

It's a tiny orchid, but it does carry the signals
which indicate a female wasp to a male wasp.

It backs those visual signals with a perfume
that is virtually identical chemically

to the smell emitted
by a female wasp.

And the two things between them are
quite enough to delude a poor male.

Watch.

He tries to fly away with her.

But how is this helping the orchid?

The answer lies in the mechanical
construction of the flower.

The purple part is the bogus female.

The other half carries a little cup with the
pollinia attached to another of those sticky pads.

A black head and a furry body is all, apparently,
you need to disguise yourself as a female.

This simplified mock-up is attached to the other
part of the flower by a delicate but strong hinge.

When the male tries to carry off
what he assumes is the female,

he's thrown upwards by the force of his own
exertions towards the cup and the pollinia.

But the male's position
has to be absolutely correct.

In spite of the enthusiasm with
which this one is trying to mate,

he isn't clinging
in exactly the right way.

Perhaps this time the orchid
will be luckier.

Obviously there's little wrong with this orchid's
mimicry. TWO males are trying to get at it.

There - the pollinia
are attached to his back.

But the most punishing of fertilization
techniques used by plants

involve not sexual deception
but imprisonment, penal servitude.

GULLS CALL OUT

Gull colonies in the Mediterranean, as anywhere
else, are busy, noisy places, full of activity,

as parent birds come and go,
tending their chicks.

They are also messy, smelly places,

with droppings, misplaced bits of half-digested
fish and dead bodies lying about all over the place.

In short, for flies and ants
they are very heaven.

And beside some gull colonies,
you may find one of these.

This is not an image of a sexy, seductive
female animal. The mimicry is more gruesome.

This is a bogus corpse, mimicking
rotting flesh covered with hair

and giving off the putrid smell
of carrion.

It's the dead-horse arum.

Blowflies find it highly attractive.

They need to find a hole to get into
a corpse, and this seems to be one.

Within are a whole cluster
of tiny flowers.

Those at the top are male,
but they are not yet ripe.

Below is a barricade of spines
and below them the female flowers.

Some of the flies have already visited such a
flower as this and are carrying cargoes of pollen.

Down here, in a real corpse, they might have found
rotting flesh on which to feast and lay their eggs

so that, later, their maggots
could also feed.

But they find nothing.

As they continue to search, pollen
brushes off them onto the stigmas.

The spikes discourage them
from getting out.

By now, it's getting dark, and flies
don't fly at night. They're stuck.

During the night, the male flowers
suddenly shed their pollen.

And during the night, too,
the spikes of the barricade shrivel.

So, by the morning,
the flies are free to go.

And each takes with it a load
of pollen from the male flowers.

One of the most extraordinary of these insect-enticers
lives here, in the tropical rainforest of Sumatra.

It only flowers once in a thousand days and, when
the flower develops, it only lasts for three days,

so very few people have seen it.

But here it is.

Technically, it's a whole group
of flowers clustered around this,

but you could be justified
for regarding it as one flower.

If you do that, this is
the biggest flower in the world.

It's related to the dead-horse arum, but
it's nine feet tall and three feet across.

It's Amorphophallus titanum,
the titan arum.

The function of this great spike
in the middle is to produce a smell.

And if you smell it, it smells
very strongly of bad fish.

This, apparently, attracts insects
which come along here

and go down into this great funnel to the
small flowers that grow at the base.

No-one was sure what insects
pollinated the titan arum.

As we watched, we saw that, without doubt,
the job was done by tiny sweat bees.

Like other arums, the male flowers
form a band at the top.

Below them, the female flowers,
with long yellow-tipped stigmas.

The bees seemed to find some reward on the
stigmas, for they crawled all over them,

distributing the pollen
they'd brought.

Why should the titan arum produce the biggest bloom
in the world to attract such tiny pollinators?

To be effective, these bees must
bring pollen from another bloom.

Since the plant is rare,
the nearest may be miles away.

It's not easy to spread perfume over such distances
in the still, humid air of the rainforest.

Perhaps the best way to do so is to disperse
it from the top of a towering spire,

like smoke from a factory chimney.

We tend to assume that flowers
are here to gladden OUR hearts.

They're not. Plants produced flowers
long before humanity appeared

to summon mammals, birds
and, above all, insects.

And though they sometimes are given
some payment, they are the servants.

The masters are the plants.