Placeholder Image

Subtitles section Play video

  • Do you know

  • how many species of flowering plants there are?

  • There are a quarter of a million -- at least those are the ones we know about --

  • a quarter of a million species of flowering plants.

  • And flowers are a real bugger.

  • They're really difficult for plants to produce.

  • They take an enormous amount of energy and a lot of resources.

  • Why would they go to that bother?

  • And the answer of course, like so many things in the world,

  • is sex.

  • I know what's on your mind when you're looking at these pictures.

  • And the reason that sexual reproduction is so important --

  • there are lots of other things that plants can do to reproduce.

  • You can take cuttings;

  • they can sort of have sex with themselves;

  • they can pollinate themselves.

  • But they really need to spread their genes

  • to mix with other genes

  • so that they can adapt to environmental niches.

  • Evolution works that way.

  • Now the way that plants transmit that information

  • is through pollen.

  • Some of you may have seen some of these pictures before.

  • As I say, every home should have a scanning electron microscope

  • to be able to see these.

  • And there is as many different kinds of pollen

  • as there are flowering plants.

  • And that's actually rather useful for forensics and so on.

  • Most pollen that causes hay fever for us

  • is from plants that use the wind

  • to disseminate the pollen,

  • and that's a very inefficient process,

  • which is why it gets up our noses so much.

  • Because you have to chuck out masses and masses of it,

  • hoping that your sex cells, your male sex cells,

  • which are held within the pollen,

  • will somehow reach another flower just by chance.

  • So all the grasses, which means all of the cereal crops,

  • and most of the trees

  • have wind-borne pollen.

  • But most species

  • actually use insects to do their bidding,

  • and that's more intelligent in a way,

  • because the pollen, they don't need so much of it.

  • The insects

  • and other species

  • can take the pollen,

  • transfer it directly to where it's required.

  • So we're aware, obviously, of the relationship

  • between insects and plants.

  • There's a symbiotic relationship there,

  • whether it's flies or birds or bees,

  • they're getting something in return,

  • and that something in return is generally nectar.

  • Sometimes that symbiosis

  • has led to wonderful adaptations --

  • the hummingbird hawk-moth

  • is beautiful in its adaptation.

  • The plant gets something,

  • and the hawk-moth spreads the pollen somewhere else.

  • Plants have evolved

  • to create little landing strips here and there

  • for bees that might have lost their way.

  • There are markings on many plants

  • that look like other insects.

  • These are the anthers of a lily,

  • cleverly done

  • so that when the unsuspecting insect

  • lands on it,

  • the anther flips up and whops it on the back

  • with a great load of pollen that it then goes to another plant with.

  • And there's an orchid

  • that might look to you as if it's got jaws,

  • and in a way, it has; it forces the insect to crawl out,

  • getting covered in pollen that it takes somewhere else.

  • Orchids: there are 20,000, at least,

  • species of orchids --

  • amazingly, amazingly diverse.

  • And they get up to all sorts of tricks.

  • They have to try and attract pollinators

  • to do their bidding.

  • This orchid, known as Darwin's orchid,

  • because it's one that he studied

  • and made a wonderful prediction when he saw it --

  • you can see that there's a very long nectar tube

  • that descends down

  • from the orchid.

  • And basically what the insect has to do --

  • we're in the middle of the flower --

  • it has to stick its little proboscis

  • right into the middle of that

  • and all the way down that nectar tube

  • to get to the nectar.

  • And Darwin said, looking at this flower,

  • "I guess something has coevolved with this."

  • And sure enough,

  • there's the insect.

  • And I mean, normally it kind of rolls it away,

  • but in its erect form,

  • that's what it looks like.

  • Now you can imagine

  • that if nectar

  • is such a valuable thing

  • and expensive for the plant to produce

  • and it attracts lots of pollinators,

  • then, just as in human sex,

  • people might start to deceive.

  • They might say, "I've got a bit of nectar. Do you want to come and get it?"

  • Now this is a plant.

  • This is a plant here

  • that insects in South Africa just love,

  • and they've evolved with a long proboscis

  • to get the nectar at the bottom.

  • And this is the mimic.

  • So this is a plant that is mimicking the first plant.

  • And here is the long-probosced fly

  • that has not gotten any nectar from the mimic,

  • because the mimic doesn't give it any nectar. It thought it would get some.

  • So not only has the fly

  • not got the nectar from the mimic plant,

  • it's also -- if you look very closely

  • just at the head end, you can see that it's got a bit of pollen

  • that it would be transmitting to another plant,

  • if only some botanist hadn't come along

  • and stuck it to a blue piece of card.

  • (Laughter)

  • Now deceit carries on through the plant kingdom.

  • This flower with its black dots:

  • they might look like black dots to us,

  • but if I tell you, to a male insect of the right species,

  • that looks like two females

  • who are really, really hot to trot.

  • (Laughter)

  • And when the insect gets there and lands on it,

  • dousing itself in pollen, of course, that it's going to take to another plant,

  • if you look at the every-home-should-have-one scanning electron microscope picture,

  • you can see that there are actually some patterning there,

  • which is three-dimensional.

  • So it probably even feels good for the insect,

  • as well as looking good.

  • And these electron microscope pictures --

  • here's one of an orchid mimicking an insect --

  • you can see that different parts of the structure

  • have different colors and different textures to our eye,

  • have very, very different textures

  • to what an insect might perceive.

  • And this one is evolved to mimic

  • a glossy metallic surface

  • you see on some beetles.

  • And under the scanning electron microscope,

  • you can see the surface there --

  • really quite different from the other surfaces we looked at.

  • Sometimes the whole plant

  • mimics an insect, even to us.

  • I mean, I think that looks like some sort of flying animal or beast.

  • It's a wonderful, amazing thing.

  • This one's clever. It's called obsidian.

  • I think of it as insidium sometimes.

  • To the right species of bee,

  • this looks like another very aggressive bee,

  • and it goes and bonks it on the head lots and lots of times to try and drive it away,

  • and, of course, covers itself with pollen.

  • The other thing it does

  • is that this plant mimics another orchid

  • that has a wonderful store

  • of food for insects.

  • And this one doesn't have anything for them.

  • So it's deceiving on two levels --

  • fabulous.

  • (Laughter)

  • Here we see ylang ylang,

  • the component of many perfumes.

  • I actually smelt someone with some on earlier.

  • And the flowers don't really have to be that gaudy.

  • They're sending out a fantastic array of scent

  • to any insect that'll have it.

  • This one doesn't smell so good.

  • This is a flower

  • that really, really smells pretty nasty

  • and is designed, again, evolved,

  • to look like carrion.

  • So flies love this.

  • They fly in and they pollinate.

  • This, which is helicodiceros,

  • is also known as dead horse arum.

  • I don't know what a dead horse actually smells like,

  • but this one probably smells pretty much like it.

  • It's really horrible.

  • And blowflies just can't help themselves.

  • They fly into this thing,

  • and they fly all the way down it.

  • They lay their eggs in it,

  • thinking it's a nice bit of carrion,

  • and not realizing that there's no food for the eggs, that the eggs are going to die,

  • but the plant, meanwhile, has benefited,

  • because the bristles release

  • and the flies disappear

  • to pollinate the next flower -- fantastic.

  • Here's arum, arum maculatum,

  • "lords and ladies," or "cuckoo-pint" in this country.

  • I photographed this thing last week in Dorset.

  • This thing heats up

  • by about 15 degrees above ambient temperature --

  • amazing.

  • And if you look down into it,

  • there's this sort of dam past the spadix,

  • flies get attracted by the heat --

  • which is boiling off volatile chemicals, little midges --

  • and they get trapped underneath in this container.

  • They drink this fabulous nectar

  • and then they're all a bit sticky.

  • At night they get covered in pollen,

  • which showers down over them,

  • and then the bristles that we saw above,

  • they sort of wilt and allow all these midges out, covered in pollen --

  • fabulous thing.

  • Now if you think that's fabulous, this is one of my great favorites.

  • This is the philodendron selloum.

  • For anyone here from Brazil, you'll know about this plant.

  • This is the most amazing thing.

  • That sort of phallic bit there

  • is about a foot long.

  • And it does something

  • that no other plant that I know of does,

  • and that is that when it flowers --

  • that's the spadix in the middle there --

  • for a period of about two days,

  • it metabolizes in a way

  • which is rather similar to mammals.

  • So instead of having starch,

  • which is the food of plants,

  • it takes something rather similar to brown fat

  • and burns it at such a rate

  • that it's burning fat, metabolizing,

  • about the rate of a small cat.

  • And that's twice the energy output, weight for weight,

  • than a hummingbird --

  • absolutely astonishing.

  • This thing does something else which is unusual.

  • Not only will it raise itself to 115 Fahrenheit,

  • 43 or 44 degrees Centigrade, for two days,

  • but it keeps constant temperature.

  • There's a thermoregulation mechanism in there

  • that keeps constant temperature.

  • "Now why does it do this," I hear you ask.

  • Now wouldn't you know it,

  • there's some beetles that just love to make love at that temperature.

  • And they get inside, and they get it all on.

  • (Laughter)

  • And the plant showers them with pollen,

  • and off they go and pollinate.

  • And what a wonderful thing it is.

  • Now most pollinators

  • that we think about are insects,

  • but actually in the tropics,

  • many birds and butterflies pollinate.

  • And many of the tropical flowers are red,

  • and that's because butterflies and birds

  • see similarly to us, we think,

  • and can see the color red very