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.
Hello, welcome to this episode of Back Garden Biology, I I'm sitting in
my lawn and there are quite a lot of bits of my lawn that I let grow
quite wild and we only mow them at the end of the summer and that allows all kinds
of plants to establish in the lawns. Of course, we think of lawns as being just consisting of grass
and that's mostly what people want to lawn to consist of. And some people, of course, spend a lot
of time trying to remove any other plants from their lawn mowers. Wage war
against moth. They wage war against daisies and dandelions and they only want to have grass in their lawn.
So in a conservation lawn rather than grass, you want to have lots of other things,
growing wildflowers, etc. But actually what people often find is that it's really
difficult to get them to establish so you can throw in tons of seed of all kinds
of different species that you'd like to have and find that nothing ever establishes. And that's
because grass is actually a really good competitor. And once you've got a good sward of grass established
over things can find it quite difficult to invade. But there is a plant
that if you sow it seeds into your lawn and your lawn isn't too dense and thick,
has a pretty good chance of establishing. And it's called hay rattle or yellow
rattle. Now, the reason that the hay rattle is able to establish
in your lawn when lots of other wildflowers might find it difficult is because hay rattle is not
an ordinary plant. It's got a special trick up its sleeve and it's what we call a Hemi parasite.
Now, about half the species on this planet, amazingly, are parasites of one sort or another,
and they are freeloading on the other half. Now, hey, Rattle is a hemi parasite.
That means it doesn't rely entirely on parasitism. And we can see that it has nice green
leaves which do conduct photosynthesis, but it doesn't have very many leaves and they're quite small.
So it's surprising that it's so successful. But below ground, the hay rattled doesn't produce
any proper rates. Instead, what it does is it plugs into
the roots of grasses and it plugs into their xylem vessels, which are conducting
water, mineral nutrients, and it taps off their water and then mineral nutrients.
The effect of adding hay rattle into a piece of grass is that it starts
to weaken the grasses. And that means that it's easier to get some of the wildflowers
that you want to grow in your lawn to actually establish because they struggle to compete against
the grasses, especially if you've been fertilising your lawn until fairly recently.
Now, there are lots of schemes up and down the country where people are trying to restore wildflower meadows. They're trying
to turn that area of just grass into a meadow which is filled with lots of different species.
And this hay rattle is one way that they can help. That can really help them to do that.
So they so back in with the wildflowers in the hope that it will emerge and start Parisot
ising the grasses are make it easier for other wildflowers to establish.
So in this episode we're going to go out to my local park where there are some areas where they're trying to restore
meadows. I mean we can see lots of rain up this growing. And later in the programme we're going to hear
about some other parasitic plants, including mistletoe, which is probably a familiar thing at
Christmas at least. And Rob Salguero Gomez, he works in the Department of Zoology,
has a study going on that plants we're going to find out a little bit about what he's doing.
Hello, my name is Chris Thoroughgood, and I'm going to be talking about this seemingly
unattractive plant, but it's very, very interesting. This is a broom rape.
Its scientific name is are a banki. And why is it interesting? It's parasitic.
So it steals all of its food. It robs its existence from the roots
of green plants. And you'll notice that this plant has no green leaves or chlorophyll
of its own. It also produces no functional roots either. And
as a seedling, it attaches to the roots of other plants, in this case to the roots of an I.V.
And then it siphons off its food. Now, broadly speaking, we can divide parasitic
plants into those that are photosynthetic. Still, the hammie parasites, they have their own leaves
and chlorophyll and those that are not and are completely dependent upon their hosts for
their survival, such as this bring right now parasitic plants can have
what's being terms the Dracula effect. So they suck the life for the sap out of their host plant
like this. What some of these parasitic plants have shifted from the wild
vegetation to cultivated crops. So which weed is one particularly
pernicious weed that across Africa and Asia can have devastating effects on crops?
It costs about devastates about ten billion dollars worth of crops every year. So
it's a real problem for farmers. So it's it's worth studying and understanding these
plants to understand how to control them, where they become weeds. But it is also interesting to understand
them because they're fascinating in their own right. These are evolutionary enigmas
and little is known about the life history of many of the species. Some of the exotic ones
are fascinating. One of the better known is roughly zikr, which produces
the largest flowers in the world. They can grow to over a metre across. And this extraordinary
plant is an Endou Fetich hollow parasite. So not only does it not have
leaves or chlorophyll like this or a banky, but I've shown you it also lives inside
the tissues of its hosts. Only emerging when it produces these gigantic
blooms on the rain forest floor. So if ever there was a botanical enigma, this
is it.
So I've left my guard and I'm in the pass of Kozlow Park. And gets to say Park is run
by the city council, you probably hear the road in the distance. It's not that far away from here.
That's the ring road around a very busy road in this park. If you can ignore that
noise, it feels very tranquil. And there's lots of different parts of this park. This park
has been allowed to become a really nice meadow. And I don't know what you can hear in this film,
but I can see butterflies flying around. I can hear grasshoppers chirping. And it's what we think of as traditional
nice meadow. And that means it has wildflowers in it. And I've got a few different ones show you. I don't
know how well the camera will pick them up, but there's four on my hand here. This
little Rev's one here is a red clover. The white one is an Upsidaisy.
It's much bigger than the lawn daisies that grow in your lawn. Then there are two yellow ones.
The slightly more feathery thing is at ladies bed straw.
It smells quite nice there at the foliage and that's why it gets its name from. And this
is eggs and bacon. It's a little bit of low growing yellow
flower. So all four of these can be found in abundance here and lots
of other flowers as well. So that's the question really. Why is it in a nice meadow like this? You've
got all these wild flowers and it hasn't just it's not just the grass totally dominating.
And that's I to think about it a bit more detail how the yellow rattle is playing a crucial role in maintaining
these wild flowers. Okay, so what's going on in the magic? Well, what happened with
a lot of our traditional machos is people starts to fertilise them, added fertiliser to
get more yield. Get more grass. No, the grass the farmers would harvest and use it to feed their
animals. I mean, artificial fertilisers became available. Farmers leapt on those and started fertilising
pastures. Now, what happens when you do that is that grass, grass and the wildflowers
you can think of as being two different strategies, if you like. And it turns out if you don't fertilise
them too much and you let animals graze them or you perhaps move them once a year, then
these two things can grow together side by side. But when you start to fertilise, the grass
becomes really dominant. And it's a bit like playing the game rock, paper,
scissors. And if you can imagine that the grass starts playing the strategy paper
and the wildflowers are stuck with a strategy rock. And as you know, if you play that game when paper
meets rock, paper always wins. So every time these two things meet,
a paper beats the rock and gradually the grass just takes over. And the poorer wildflowers
are wiped out. Now, if you're familiar with that game, you will know
what you need in a game of rock, paper, scissors for it not just to become as boring as that is a pair of scissors.
And that is what the Hey Russell represents. So let's just cut some and we'll see what happens.
So this is now my hay rattle. This is it. Once it's setting, see these empty pods
and listen. That is the rattling and that's why it's called. Hey, Russell.
So this is now playing strategy scissors. And of course, when scissors, me, paper, scissors,
cut paper. So the Ryan and first the the hay rattle attacks the grasses and wins
against the grasses. But the final flowers are still playing. Rock and scissors doesn't
win against rock. In fact, it loses. And that's because this plant cannot parasitise
the wildflowers. It can only parasitise the grass. And so now
we have all three strategies. We have rock. We have paper. And we have scissors.
And the three of them can actually live together very, very well indeed. Because no body
has an absolutely winning strategy. And so that's how plants can play rock, paper, scissors.
Today, we will learn a bit more about mistletoes, mistletoes or semiprecious, if he
plans a semi parasitic plant is a plant that obtains some
but not all of the necessary resources from another living and species like a tree.
In the case of many mistletoes, a really interesting feature of mistletoes is
the point of connexion to its whole street. Here you can see a drawing of
a serious because he has grown no leaves a deciduous host tree. As many you can
find across the UK. And then here you can also find an individual of mistletoe.
Mistletoe is, of course, do have leaves and branches. But if we were to some in
or you would see that in this part of this section where the branch of the whole story and the mistletoe
come in contact is like in roots where you can find instead of that. So really interesting
architecture. If you consume in here, you will be able to see it's planted with my
finger. I'm showing you the whole storeroom. The Historium is
a root like structure that the mistletoes developed when they first germinate upon the
branch of the whole street. This structure allows the mistletoe
to become a hemi. Parasite's Hemi comes from Greek means half to half parasites.
This structure allows it to steal quote unquote, water and nutrients from the whole street
water, nutrients that are, of course, come in all the way from the underground section of the tree.
So they steal the water. They're still in nutrients and they carry out their own photosynthesis.
But even then, they're not 100 percent efficient. And when that there was a paper that came out last year
in Nature pointing out the fact that the first synthetic varieties of mistletoes is not
as efficient as as many other plants that grows in Tree of Life. So perhaps instead of referring
to mistletoes as healthy parasites, we should perhaps three quarter parasites, not
any parasites. Well, I'm back where I started just to finish off this video. A huge thank you to
Chris and to Rob for making those pieces. What I filmed introduction. I haven't even asked Chris to do
it. Hadn't said that was really nice of him. And I did it with a unique taste. But if you look at that roughly,
see a picture that popped up during his little piece, you'll notice it's not
a photograph. It's one of his amazing paintings. And Chris is a very, very talented
botanical artist, as well as knowing loads about plants. And his Twitter feed has lots of his
lovely pictures. If you're not already following that. So parasitic plants come in different shapes
and forms. We have the hemi parasites. We have the full parasites who really are the vampire plants.
And the Ryan unfussy my lawn. Well, I've only got a few plants here. No, you can see them. Whether my cameraman
can feed Matt as the big dark brown seed pods and if managed to recover a bit, they didn't like
that very, very dry period earlier in the year. But they are setting seed now. And I'm hoping
that by having them in my lawn, they'll help other wildflowers to establish. I've also
got mistletoe actually in my apple tree at the back of the garden. And what happened this year? We noticed it completely
come unplugged from the tree and it's fallen out. And I don't know. But I think that might be the
host tree rejecting the mistletoe plants. Do you have a kind of primitive immune
system they are able to recognise when they're being invaded by something that isn't themselves
and take action against it? So like all of us in the face of disease and parasites, we're not helpless
in the face of them. We've got weaponry and we can fight back. Anyway, I hope you enjoy hunting
for vampire plants yourself. See you next time. I'm back on Bolaji.