Hello, my name's Lindsay Turnbull and I'm an associate professor in the Department of Plant Sciences
at the University of Oxford, and we're right in the middle of this very serious corona virus crisis right
now. And my students are all stuck at home and we want to keep them in touch with biology
and keep in touch with us. And so we're going to make a new series of videos and they're going to be called back garden
biology.
Welcome to my second episode. I'm going to look at a particular plant this time
and it's pollinators and I'm starting in my front garden, not with my focal plant,
but just to show you some general principles. This is Rosemary. We grow that as a herb
humans. And if I touch her and if I bruise the leaves, I got a really wonderful smell.
Now, on this, Rosemary, every time I come out here, I can see bees visiting it. They're
not interested in its culinary properties. They are interested in its flowers. But you probably
know that not all flowers are the same. Some flowers are really attractive to bees and others are not.
And bees are interested in two things that flowers produce. They're interested in nectar, which
is a sugary liquid, very high and energy. Bees are flying and burning energy,
so they need that nectar. The other thing they are interested in is pollen.
The plants, of course, want them to pick up pollen and transfer it around between flowers.
But the bees will take some of that pollen as well and take that home to feed their larvae.
Poland has a lot of protein in it. It's not just sugar. So it's not just empty
calories. It's actually got good stuff in it to feed growing bee larvae.
Now, if you want to really attract bees, you've got to have enough flowers. And so this rosemary plant
is attracting a lot of bees, partly just because it's huge. And if that's of a second one growing near
it and that kind of a parent's seed to insects is really important. And
that's what we're going to look at in the back garden. It can go and look at another plant, which has got a few
clever tricks to try to persuade bees that there's perhaps more on offer
than there actually is. So around in the back garden now and crouching next to the focal plant,
it's been a bit of a gap between me shooting that first sequence in the front garden and coming to do this, because
unfortunately, I've had this cold 19 virus, or at least I think I've had it. And I was in bed
for about eight days and I was very lucky that I didn't have any of the really serious symptoms that some
people have had. But it is a reminder that we're all vulnerable to it and we must follow
the advice as closely as we possibly can. We certainly don't want to have it. It wasn't very nice experience.
OK, well, here is my fear. Plant is quite attractive. Not a real showstopper, but nice
if you come up close to it. I am told you what it is here. And the reason for that is I want
you to have a guess and I'm going to cut off one of its leaves and show it to you. I'm going to have to wear a
glove because I am quite allergic to this plant. And if I touch it, I tend to find that I react
to it. So let's chop off a leaf and have a look at it. I'm also going to ask
you, is body part. Does it remind you of any guesses?
Well, it's supposed to look like a disease lung. And the reason for that
or the explanation, I should say, for why and that's important
in its name is that in mediaeval times, a herbalism was a big thing. And of
course, today, a lot of our medicines do come from plants. Plants produce an incredible
array of chemicals. They are the sort of natural pharmacy. But we didn't know in mediaeval
times what plants were they supposed to use for different ailments and may develop something
called the doctrine of signatures. May decided that obviously God wanted people
to heal themselves. And so he would give signs on various plants as to what they should be used
for. And because that leaf looks like a disease lung. They thought that clearly this plant
must be used to treat lung conditions. Now, it's probably all a bit backwards. And I think this
plant was used to treat lung conditions before the adoption of signatures ever emerged, probably.
So a lot of it was a bit, you know, being kind of deciding after the fact. Yes, Ash, those leaves do
look a bit like a disease lung. But anyway, this is called Longworth's. And I certainly don't
advise, no matter how bad your coffee is, that you start grinding the leaves of this plant and treating yourself. It has
got some very toxic compounds in it. And I don't know whether there's any scientific evidence to show that any
medicine derived from this plant could actually help you if you had a cough. And you certainly
shouldn't try to harvest things yourself because plants can vary a lot and some leaves will have a
lot of compounding and some will have a lot less. Now, the reason I'm interested in it, we were talking
about pollinators. And if you look closely, we just zoom in on this plant for a minute. We can see
something a little bit unusual. So the flowers are very different colours and that is
very unusual. And if we look here, this is a newly opened flower. It's just starting
to open and it's got a lovely pink colour. And as the flowers get a bit older,
here's one that's a little bit older and you can see it starts to get suffused with power poles. You can see
sort of pink and purple together. And that flower is the oldest one. And it's really
very blue. Okay, so why is it doing that?
Well, that's something that I want to take a look at in more detail, and it's to. With its pollinators.
That's why that plant is changing. Kind of like that. And scientists have come up with explanations as to why
this happens. It's quite a rare phenomenon. And actually, the biggest mystery is why
more plants don't actually do it. But before we look at what what the explanations are for
this colour change, we need to have a closer look at its main pollinators.
The small gingery bee visiting this long word is a male of the hairy footed
flower bee. And that's a very common early bumblebee in British gardens. This
little black bee is the female of the same species. And we can see that she
has these little orange blobs on her legs. And those are pollen sacs. So she's not just taking
nectar. She's gathering pollen to take back and feed her brood of bee larvae.
And both of those bees you can see really target the pink flowers. If they land on a blue
on, it's not for long. Mostly, they seem to be able to aim straight for the pink ones.
Now, there are also other insects that visit Longworth's. I wasn't able to film it on long word, but this
is a bee fly. You can see it's a fly because it's such an amazing flyer
able to bullseye those tiny little forget-me-not flowers without even landing on
the flowers, just hovering above them. Only a fly can do that. When the bee
fly lands and sits down, you can really tell it's a bee fly. See how its tongue is sticking out.
A bee tucks its tongue underneath its body. The fly. Wow. But embarrassing, really.
Okay, so we've just been having a look at some of the pollinators of loanwords. Is that the most common one is the hairy forces
flower bee. So how did interactions to plants and the pollinator drive
the evolution of that floral colour change that we can see? In other words, maybe
glad to know I've got my pleader. I'm going to try and show you how it works. So let's have a
closer look. I've got three potential lungworm plants here. This
especially be the leaf. And here's the stamp on which the flowers are going to appear. And this plant is going to be
what's called the ancestral plant. I'm going to imagine this is how long it started and it produced
pink flowers. And every day I'm going to assume that the plant produces another flower. So it's
day one, day to day three. But the flowers only last for three days.
So on day four, when that flower appears, is going to disappear.
And on day five, when this new flower appears, that one's going to disappear. And on day six
and the final one appears that's going to disappear. So the most flowers it's ever going to have is three.
It's going to be from over there for a second. Make this a bit easier. Now, what if there's
a mutant plant that's doing something a bit different? So it opens a flower on
day one, flower on day two and a flower on day three. But on day four,
when this flower opens, it decides to hold onto that flower. It's not producing actual pollen
anymore. So it's not really costing the plant anything, but it just decides to let that flower,
that the old flower hang on in there on day five. It's still going to let that one
hang on there. And on day six, it's going to do the same. So on average, these flowers last for six days,
but only for three of them when they're in the first three days of actually producing pollen
and nectar. That's valuable for bees. And these three are bit on rubbish. And the question is
if will this plant do better than this one? Well, I think the answer is in the short term, yes, it
would, because it looks much more attractive to the bees. And so they might go to this plant
in preference to that one. So this plant will be more successful and we might end up with a
lungworm population that looks like this. Okay. So that's all well and good.
But now the bees are coming to the lungworm plans. And if they arrive first at one of these
flowers, the old ones, because they can't tell the difference, then they're going to be really disappointed
because there isn't any pollen or nectar there. And they might choose to just fly off again. And so
the lungworm might start to suffer as the bees start to realise that this is not a plant to be trusted.
It's not sending what we call honest signals. And so a second thing
might happen where Longworth's charvat a new kind of change occurs.
So here's what might happen now. This plant opens a pink flower on day one,
a new pink flower on day two and a new pink flower on day three. But then on day
four, when it opens a new pink flower, it changes the colour of the old
one. OK. And then on day five, when yet another new one, pink one
opens, it changes the colour, the old one. And finally, on day six, when the last
new one opens, it changes the colour again. I'm going to shove that along and show the radial flower
as being really blue purple. And the question we have to ask now, will that be more successful
than that? And I think this will be more successful. And the reason is that bees
is still a lots of flower. To attract him, the bees will come there. But they are targeted
at the flowers with the high reward so they won't leave quickly feeling disappointed.
Instead, they will stay and they will visit the flowers with the pollen in
the nectar. Okay, so it seems that the Longworth has come up
with a really great strategy, and I can imagine it evolving like that as a two step process.
First, to retain the old flowers, but then as pollinators learnt, perhaps
Lungworm is cheating on it to develop the systems, change the colour of them
so that pollinators wouldn't be cheated. And that's an example of cocoa evolution,
where the plant and its pollinator are influencing each other and the way
that they evolve. So we're going to end where we began again with back at the patch of Longworth's.
And in fact, I can see a male hairy fossil flower bee sting right now as we speak. This
patch of Ludwig is in the shadiest coolest part of the garden and it's still going strong. Some of the other
parts where it's been sunny are finishing. Lungworm is one of the first plants to flower
in the year. And that's why it's so important for these very early pollinators. And studies
have been done that show that the plant is also highly dependent on that hairy footed flower
bee. If it's not allowed access to the flowers. Then you get very poor seeds that
actually the lungworm by the primrose have back pain from mating system. So it requires
pollinators to come and transfer pollen amongst plants in order that it can set seed.
And we live. It's got this very clever trick of hanging onto the old flowers in order to look
like there's more normal for him. There actually is. But when the bees arrive, they didn't feel cheated
because they know exactly which flowers are offering the best rewards. Now, the pink ones, not
the blue ones, and the bees seem to know that. And they focus in on those pink ones and spend more time visiting
them. And that's also been shown. And if you have some of this club home and you want to have a go,
you could film on your phone very easily and then watch and see whether they do seem to target
the pink ones. When I've done that, I feel like they really do do that, but I haven't really quantified that properly
or anything. If you want to grow long and you haven't got it in your garden, it's really, really easy
to grab it from seed. And once you've got it spreads very easily and you can move it around your
garden, you can move the seedlings around as tough as old boots or grab anywhere. And it's particularly good for
growing in what's called dry shade underneath trees. It's specialised on doing that
at the moment. It can grow under trees because most of the trees haven't really leafed out yet properly.
And once the trees leaf out, they take all the light, they suck up all the water and they make life very difficult
for anything growing underneath. Anyway, that's the end of today's or
this this week show. And hopefully we'll be back again next week and hopefully we'll all be recovered in this
household anyway from this horrible virus. I hope you're staying safe at home as well.