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Hello, my name's Lindsay Turnbull and I'm an associate professor in the Department of Plant Sciences

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at the University of Oxford, and we're right in the middle of this very serious corona virus crisis right

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now. And my students are all stuck at home and we want to keep them in touch with biology

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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

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biology.

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Hello, welcome to this episode of Back on Biology. I'm busy in the garden and I haven't, like most gardeners

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getting on with sowing seeds. So very busy time of year. I've been saving some bean

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seeds. I've got some in my hands. Here you can see they're very dry. These are straight

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out of the packet. They're just the common bean. They sometimes the different varieties that can be kidney

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beans, they can be runner beans. These ones are called Bortolotti. And it's just the shape and

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a colour of the beans a little bit different. Italians like them a lot. When I was living in Switzerland, I got used to eating

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them. So I'm trying to grow some for myself. They're like a lot of sons. I'm not sure how well I'm going to do here.

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Asuman again. Now we can see that I've removed the seed coat. I just peeled it all

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away so there's no pink there anymore. What you're looking at, these two halves

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are called the Kotto Legions. They're part of the embryo and they

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are a food store. So they're packed full of starch and protein which is going to help

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the new seedling get established and that food's been given by the mother plant it put it back

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for this till seed. Let's have a look at a big tray of seeds that I've got here. These are various different

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species that I sewed a couple of weeks back. Different species in each row.

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And you can see some of them are doing very well. It germinated. They've all got a pair of cotton. That's

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all you can see. They're sometimes called the seed leaves. And it makes it very difficult

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to actually tell seedlings apart because so many plants are like this.

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They produce a pair of seed leaves. So, for example, here we have some annual fees are just

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there to provide some colour for me and grabbing them for the flowers. That's these two

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rows here. But here we have lettuce seedlings. And also I don't want to get those confused and

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growing those to eat some here. You can see nothing has happened.

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And that's partly because it's an old packet of seeds. I'd kept that packet to say it's about five years and I thought was about

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time I throw them away or give them one last shot. They haven't come up and that does

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happen to seeds, so they don't last forever. You should try to store them somewhere. Cool.

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I obviously didn't do that. And small seeds tend to keep longer than large ones. So large

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being seeds will only keep for one or two years and then you really have to throw them away and buy new ones,

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cause some seeds are famous for lasting for a very long time, like poppy seed. But they tend to be very tiny,

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some seeds. If you say them, they won't come up, not because they're dead, but because they have special dormancy

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mechanisms to stop them from germinating unless the conditions are just right. So some needs to be

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sent in the autumn, for example. They need a winter to germinate. So

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we're all really familiar with seeds. And in fact, we probably think that all plants produce

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seeds, but that's not actually true. So most of the plants that we're familiar

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with, four dominant plants around us are belong to a group called the Seed Plant. So they certainly

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produce seeds, but there are other plants in the world and some of them produce new seeds

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at all. Alright, so we have a look at some seeds and we saw what they were like and we are very

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familiar with seeds. And I said that there's a very large group of plants called the seed plants

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and actually the seed plants fall into two groups. So the most common kind and the kind

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we're probably all most familiar is a group called The Flowering Plants, and their technical name

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is angiosperms. They are the most diverse group of plants on today's earth,

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but they're actually relative newcomers and they only evolved during the Cretaceous

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period. And that was the last period on Earth when the dinosaurs roaming around.

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There is another group of seed plants and they are called Jim No Sperm's.

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This is you. That's a gymnast band, Pine Lodge. They're also Joomla

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sperm. So the conifers are the biggest group. They're also seeds, plants. They're not

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as diverse as the angiosperms now as the flowering plants. But in the past they were very,

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very abundant. Ameera, much older group than the flowering plants. So both of these

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kinds of plants produce seeds as well as producing seeds. They have a system

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of water transport. And that's why I'm holding up the stick factory, because that's one of the best plants

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in which you can see what's called the vascular system. So if I break it

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and peel it and you can see these strings, me hold it over this white

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thing, you can see what looked like strings and they got stuck in your teeth. When you eat celery, don't try and come to terms.

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Cameraman or I might not focus. And there's there are two types of pipes and there

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are pipes that conduct water and they always contact water upwards from the roots to the leaves.

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But alongside them, there are also another kind of pipe that transports sugar around the plant

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and they can go in any direction that flow of sugar. It generally goes from places where sugar

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is stored or it's being made to a place where sugar is needed. And the two types

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of pipes, the water conducting pipes are called xylem and the sugar conductor. Pipes are called flowing,

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so the seed plants have a vascular system and they produce seeds. But there are other

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kinds of plants on Earth and you might be familiar with this rather tiny

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looking thing. And this is Moss. So it's pretty familiar to us all. And that

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doesn't have a vascular system and it doesn't produce seeds. And

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we think that something like this, because this is a modern plant, we should be careful. We shouldn't call this

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primitive. It isn't primitive. But the original land plants would have been a bit

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more like base. They wouldn't have had a vascular system. They didn't produce seeds.

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And there are some plants today that have a mixture of those features. And the

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commonest kind of ferns. So ferns have a vascular system

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so they can transport water and sugar around, but they don't produce seeds. And

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the ferns are really looking at that best right now in your garden or in a nice

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woodland. If you happen to live near one and you're allowed to go there at the moment, I want to show you some of the films

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that are coming up in my garden. They're just growing next to me here. And I think that some of the most beautiful plants

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that I grow, there are two native ferns at the back here. This is

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the heart tongue Fern. You can see the beautiful way that the new leaves uncurl.

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I was cut away. The old leaves show them off as best as possible. A mervis, wonderful, vivid

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green with quite a simple kind of leaf alongside it here.

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There's something called the Golden Scale Fern. It's just starting to unravel now or become

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very tall, about a metre tall. These individual fronds will be these things are called

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Crozier's. And people are like fractals are very interested in that because they're really very beautiful

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structures. And gradually these will unravel and keep that wonderful green colour. Now,

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through the year, they'll start to get a little bit more battered and not look quite as beautiful. But

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I've got some other ferns in my garden and I've just cut off their old leaves. So I just want to have one last close up.

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So this is the back of an old leaf. And what you see along the back of these rows of

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brown spots and those structures produce spores. And those

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spores are part of an essential part of the life cycle of a fern, which

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is really quite different from the lifecycle of seed plant. And we'll take a look at that next.

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So I just want to talk through the lifecycle of a fern. And I've got a special drawing to do that. That

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was produced by one of my former students, Pandora June. So let's have a look at it more closely.

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At the bottom here, we see a mature fern plant, and that is a diploid organism.

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That means that you've seen some of my previous videos that the genome, which is the instruction booklet

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inside all the cells that make up this organism, is actually in two halves. So the genome

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consists of two copies, if you like, of the Fern manual. And we saw that

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on the underside of the mature leaves produce these little brown structures. And as they mature,

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they release spores. And that's what those are. Now, when those spores are released,

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they are actually they do not have two copies of the manual. They only have one

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copy of the manual. So although the adult fern is what we call deployed two

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copies, the spores are what we call haploid with only one. Now, in mammals,

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we're familiar with that idea because we are also deployed. But when

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sperm and egg cells are produced, they are haploid. And what we might expect is

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certainly mammals. Is that an egg and a sperm cell then fused to form a new individual

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and restore the diploid number. So what's going to happen to these haploid spores?

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Well, they're not going to fuse with one another to form a diploid thing. Instead,

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they are going to germinate a male going to form this little

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structure. And it's just tiny. It'll be about five millimetres across. And they're generally

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heart shaped things, but they grow freely in soil. These are tiny little red hair

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cells to absorb water. And they all emerge from the spores. And we don't see them

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very often. And in fact, I don't think I've ever seen one because they will only germinate well if conditions are

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just right and that requires the place to be really moist and damp. And after a while,

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these don't live very long. These to start to produce little structures on their undersurface.

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And now they are going to produce true gametes. So there are going to be egg cells produced

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and there are going to be little mobile sperm cells produced. Unbelievably, ferns produce

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sperm and the sperm will swim away, whereas the egg cells will stay where they are

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and the sperm will try to travel to another one of these structures to fertilise the eggs.

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And once they have done that, then from the bottom of this little

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structure starts to grow. The new fern from the fertilised egg cell

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and this will wither away and there will be a new fern in its place. So

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that's a really, really complicated life cycle compared to a seed plant.

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And you see that the fern is very dependent on water. This structure is very delicate.

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And here we need water to move the sperm to the egg cells. So this is one of the reasons why you only

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find ferns in damp, moist places. So what's happened

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when the seed plants evolved is they made a move away from that lifecycle.

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So instead of having these two separate structures, the adult plant and then this strange little extra

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structure to produce gametes, they telescoped it all down so that fertilisation

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now plants still produce egg cells and they still produce inside the pollen.

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Is the male gametes. But that fertilisation all happens internally. Now, inside

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the oh, the ovaries at the bottom of the flowers, the pollen has to grow down, fertilise the field.

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And that means that the seed plants made this major evolutionary leap and they were able to get

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away from their dependency on water and they could colonise even the driest areas of

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the planet. So they ferns are still found with us today. They tend to be confined

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to damp, shady places. So let's just finish off back where we almost where

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we started next to the Ferns. You can see the golden scale. Fern has really unravelled a long

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way since we shot that first sequence. Those fronds are getting pretty close. I mean,

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it's a tall I reckon they've still got a little bit further to go. You see what I mean about them

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being really beautiful structures, but they do need quite a lot of water, actually. I can't let them dry out

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too much. And they're round here and they're very shadiest part of my garden. This is the only place where I could grow

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things like that. Let's have a very last look at the bean plants as well. I remember I

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showed those beans. I said I was going to sow them and they were all nicely swollen. You could just see those white coated legions.

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They've pushed up above ground. This is them. They've greened up and they're starting to wither away

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because the food that was stored inside them has already been used by the plant to produce

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these first pair of true leaves and all the root system below ground. And,

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well, I'm rather hopeful of getting a good harvest, to be honest. What can you be doing

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this week, then? Well, you could go around your garden just looking for seedlings. An amazing number of seedlings

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come up in my garden. And when all you can see is the cotton leads, the seed leaves. You really don't know

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what they are. And only when they produce that first pair of true leaves can you start to identify

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them. And then you might get lucky and find that some. Self seeded, it's often your garden that you actually really want to

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keep. So don't be too voracious with your waiting till next time. Goodbye.