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 on Biology. I'm busy in the garden and I haven't, like most gardeners
getting on with sowing seeds. So very busy time of year. I've been saving some bean
seeds. I've got some in my hands. Here you can see they're very dry. These are straight
out of the packet. They're just the common bean. They sometimes the different varieties that can be kidney
beans, they can be runner beans. These ones are called Bortolotti. And it's just the shape and
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
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.
Asuman again. Now we can see that I've removed the seed coat. I just peeled it all
away so there's no pink there anymore. What you're looking at, these two halves
are called the Kotto Legions. They're part of the embryo and they
are a food store. So they're packed full of starch and protein which is going to help
the new seedling get established and that food's been given by the mother plant it put it back
for this till seed. Let's have a look at a big tray of seeds that I've got here. These are various different
species that I sewed a couple of weeks back. Different species in each row.
And you can see some of them are doing very well. It germinated. They've all got a pair of cotton. That's
all you can see. They're sometimes called the seed leaves. And it makes it very difficult
to actually tell seedlings apart because so many plants are like this.
They produce a pair of seed leaves. So, for example, here we have some annual fees are just
there to provide some colour for me and grabbing them for the flowers. That's these two
rows here. But here we have lettuce seedlings. And also I don't want to get those confused and
growing those to eat some here. You can see nothing has happened.
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
time I throw them away or give them one last shot. They haven't come up and that does
happen to seeds, so they don't last forever. You should try to store them somewhere. Cool.
I obviously didn't do that. And small seeds tend to keep longer than large ones. So large
being seeds will only keep for one or two years and then you really have to throw them away and buy new ones,
cause some seeds are famous for lasting for a very long time, like poppy seed. But they tend to be very tiny,
some seeds. If you say them, they won't come up, not because they're dead, but because they have special dormancy
mechanisms to stop them from germinating unless the conditions are just right. So some needs to be
sent in the autumn, for example. They need a winter to germinate. So
we're all really familiar with seeds. And in fact, we probably think that all plants produce
seeds, but that's not actually true. So most of the plants that we're familiar
with, four dominant plants around us are belong to a group called the Seed Plant. So they certainly
produce seeds, but there are other plants in the world and some of them produce new seeds
at all. Alright, so we have a look at some seeds and we saw what they were like and we are very
familiar with seeds. And I said that there's a very large group of plants called the seed plants
and actually the seed plants fall into two groups. So the most common kind and the kind
we're probably all most familiar is a group called The Flowering Plants, and their technical name
is angiosperms. They are the most diverse group of plants on today's earth,
but they're actually relative newcomers and they only evolved during the Cretaceous
period. And that was the last period on Earth when the dinosaurs roaming around.
There is another group of seed plants and they are called Jim No Sperm's.
This is you. That's a gymnast band, Pine Lodge. They're also Joomla
sperm. So the conifers are the biggest group. They're also seeds, plants. They're not
as diverse as the angiosperms now as the flowering plants. But in the past they were very,
very abundant. Ameera, much older group than the flowering plants. So both of these
kinds of plants produce seeds as well as producing seeds. They have a system
of water transport. And that's why I'm holding up the stick factory, because that's one of the best plants
in which you can see what's called the vascular system. So if I break it
and peel it and you can see these strings, me hold it over this white
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.
Cameraman or I might not focus. And there's there are two types of pipes and there
are pipes that conduct water and they always contact water upwards from the roots to the leaves.
But alongside them, there are also another kind of pipe that transports sugar around the plant
and they can go in any direction that flow of sugar. It generally goes from places where sugar
is stored or it's being made to a place where sugar is needed. And the two types
of pipes, the water conducting pipes are called xylem and the sugar conductor. Pipes are called flowing,
so the seed plants have a vascular system and they produce seeds. But there are other
kinds of plants on Earth and you might be familiar with this rather tiny
looking thing. And this is Moss. So it's pretty familiar to us all. And that
doesn't have a vascular system and it doesn't produce seeds. And
we think that something like this, because this is a modern plant, we should be careful. We shouldn't call this
primitive. It isn't primitive. But the original land plants would have been a bit
more like base. They wouldn't have had a vascular system. They didn't produce seeds.
And there are some plants today that have a mixture of those features. And the
commonest kind of ferns. So ferns have a vascular system
so they can transport water and sugar around, but they don't produce seeds. And
the ferns are really looking at that best right now in your garden or in a nice
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
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
that I grow, there are two native ferns at the back here. This is
the heart tongue Fern. You can see the beautiful way that the new leaves uncurl.
I was cut away. The old leaves show them off as best as possible. A mervis, wonderful, vivid
green with quite a simple kind of leaf alongside it here.
There's something called the Golden Scale Fern. It's just starting to unravel now or become
very tall, about a metre tall. These individual fronds will be these things are called
Crozier's. And people are like fractals are very interested in that because they're really very beautiful
structures. And gradually these will unravel and keep that wonderful green colour. Now,
through the year, they'll start to get a little bit more battered and not look quite as beautiful. But
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.
So this is the back of an old leaf. And what you see along the back of these rows of
brown spots and those structures produce spores. And those
spores are part of an essential part of the life cycle of a fern, which
is really quite different from the lifecycle of seed plant. And we'll take a look at that next.
So I just want to talk through the lifecycle of a fern. And I've got a special drawing to do that. That
was produced by one of my former students, Pandora June. So let's have a look at it more closely.
At the bottom here, we see a mature fern plant, and that is a diploid organism.
That means that you've seen some of my previous videos that the genome, which is the instruction booklet
inside all the cells that make up this organism, is actually in two halves. So the genome
consists of two copies, if you like, of the Fern manual. And we saw that
on the underside of the mature leaves produce these little brown structures. And as they mature,
they release spores. And that's what those are. Now, when those spores are released,
they are actually they do not have two copies of the manual. They only have one
copy of the manual. So although the adult fern is what we call deployed two
copies, the spores are what we call haploid with only one. Now, in mammals,
we're familiar with that idea because we are also deployed. But when
sperm and egg cells are produced, they are haploid. And what we might expect is
certainly mammals. Is that an egg and a sperm cell then fused to form a new individual
and restore the diploid number. So what's going to happen to these haploid spores?
Well, they're not going to fuse with one another to form a diploid thing. Instead,
they are going to germinate a male going to form this little
structure. And it's just tiny. It'll be about five millimetres across. And they're generally
heart shaped things, but they grow freely in soil. These are tiny little red hair
cells to absorb water. And they all emerge from the spores. And we don't see them
very often. And in fact, I don't think I've ever seen one because they will only germinate well if conditions are
just right and that requires the place to be really moist and damp. And after a while,
these don't live very long. These to start to produce little structures on their undersurface.
And now they are going to produce true gametes. So there are going to be egg cells produced
and there are going to be little mobile sperm cells produced. Unbelievably, ferns produce
sperm and the sperm will swim away, whereas the egg cells will stay where they are
and the sperm will try to travel to another one of these structures to fertilise the eggs.
And once they have done that, then from the bottom of this little
structure starts to grow. The new fern from the fertilised egg cell
and this will wither away and there will be a new fern in its place. So
that's a really, really complicated life cycle compared to a seed plant.
And you see that the fern is very dependent on water. This structure is very delicate.
And here we need water to move the sperm to the egg cells. So this is one of the reasons why you only
find ferns in damp, moist places. So what's happened
when the seed plants evolved is they made a move away from that lifecycle.
So instead of having these two separate structures, the adult plant and then this strange little extra
structure to produce gametes, they telescoped it all down so that fertilisation
now plants still produce egg cells and they still produce inside the pollen.
Is the male gametes. But that fertilisation all happens internally. Now, inside
the oh, the ovaries at the bottom of the flowers, the pollen has to grow down, fertilise the field.
And that means that the seed plants made this major evolutionary leap and they were able to get
away from their dependency on water and they could colonise even the driest areas of
the planet. So they ferns are still found with us today. They tend to be confined
to damp, shady places. So let's just finish off back where we almost where
we started next to the Ferns. You can see the golden scale. Fern has really unravelled a long
way since we shot that first sequence. Those fronds are getting pretty close. I mean,
it's a tall I reckon they've still got a little bit further to go. You see what I mean about them
being really beautiful structures, but they do need quite a lot of water, actually. I can't let them dry out
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
things like that. Let's have a very last look at the bean plants as well. I remember I
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.
They've pushed up above ground. This is them. They've greened up and they're starting to wither away
because the food that was stored inside them has already been used by the plant to produce
these first pair of true leaves and all the root system below ground. And,
well, I'm rather hopeful of getting a good harvest, to be honest. What can you be doing
this week, then? Well, you could go around your garden just looking for seedlings. An amazing number of seedlings
come up in my garden. And when all you can see is the cotton leads, the seed leaves. You really don't know
what they are. And only when they produce that first pair of true leaves can you start to identify
them. And then you might get lucky and find that some. Self seeded, it's often your garden that you actually really want to
keep. So don't be too voracious with your waiting till next time. Goodbye.