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10| Plants, Roots, Spirals and Palaeobotany — Sandy Hetherington
112 Plays1 year ago
Plants have transformed the surface of the earth and the contents of our atmosphere. To do this they've developed elaborate systems of roots and branches which (sometimes) follow uncanny mathematical patterns such as the Fibonacci sequence.
Our guest this week, Sandy Hetherington, leads Edinburgh's Molecular Palaeobotany and Evolution Group. They take a no-holds-barred approach to understanding plant development by combining genomics, fossil records, herbaria, and 3D modeling.
Dig in!
- Show notes: multiverses.xyz
- Sandy's Twitter: @sandy_heth
- Hetherington lab Twitter @MPEG_Edinburgh
- In New Scientist on (lack of) spiral forms in ancient plant leaves
- BBC article on Herbaria
- The Guardian on Sany's work on plant roots
(00:00) Intro
(2:15) Discussion starts
Recommended
Transcript
Introduction to Plant Evolution and Guest Introduction
00:00:00
Speaker
Plants have marvellously elaborate networks of roots and branches, all for taking the sun's energy along with nutrients and moisture or water and converting it into their own growth and repair. How do they develop these complex structures and how to explain the uncanny mathematical patterns which they follow?
00:00:22
Speaker
I guess this week is Sandy Hetherington, a professor in biology at the University of Edinburgh.
Evolutionary Study of Plants: Fossils and Current Features
00:00:28
Speaker
He looks at the evolution of plants on very long timescales, on geological timescales. We talk about the methods for doing that, including the incredible details that can be revealed in fossils down to the cellular level, as well as the way that we can compare plants now to plants that have similar features that we can recognise in fossils.
00:00:52
Speaker
And doing this we can understand the evolutionary tree of trees, if you like, or plants in general. Sandy has made important contributions along with his collaborators in understanding how roots developed, and also in the patterns that leaves take.
00:01:10
Speaker
In particular, recently he's looked at how certain plants don't seem to follow a Fibonacci sequence in the arrangements of their patterns. And this is well known. There's plants now which don't do that. But he's shown that this is actually a very, very old trait. And this mainly just a rethink of an understanding of how and why plants take the shapes that they do.
Future Plant Evolution and Atmospheric Adaptation
00:01:34
Speaker
We also talk about the clues that this type of research might give to the future trajectory of plant evolution as they react to the changing atmosphere that humanity has created. Sandy strikes me as someone with a real eye for detail, and I think this comes across in his work.
Podcast Introduction and Lab Focus
00:01:50
Speaker
And suddenly having this conversation has caused me to look more closely and appreciate even the most humble of plants. I'm James Robinson. You're listening to Multiverses.
00:02:15
Speaker
Sandy Hutherington, thanks for joining me on Multiverses. Thank you all for the invitation to be here.
00:02:22
Speaker
So in biology, I've noticed that labs tend to take the name of the lead investigator. So you lead something called the Hetherington lab, but it has another name, which is, and it's a great name, the molecular paleobotany and evolution group. That's a pretty grand title. Can you explain like how all those things come together?
00:02:45
Speaker
Yeah, of course. So the molecular period botany and evolution group really came about because I wanted to give the group name a vision for what we're doing. And each one of those strands is kind of combined in this interdisciplinary approach we take to tackle questions in plant evolution.
00:03:01
Speaker
So let's start from the beginning, molecular paleobotany is a kind of name taken from a field more in the area of paleontology where paleontologists began to realize that there were many different molecular techniques that could be used to give us really new insights into fossils.
Paleobotany: Fossils and Molecular Evidence
00:03:18
Speaker
So whether that means looking at molecular in terms of chemical type signals or using molecular data as we refer to it in biology, so thinking about genes and genomes. So molecular paleobotany is the idea that we can combine evidence from fossil plants, that's paleobotany plants, with the molecular side of living species today.
00:03:37
Speaker
And then combining that all together, calling it the evolution group as well, is just to give it that framework that everything we're doing is really interpreted in an evolutionary context. Okay, so, yeah, and obviously, and the paleo thing, I think, just worth putting out, remind us, that means very old, like, very crudely put, right? Yeah, of course, yeah. So paleobotany is probably a word that a lot of people haven't really come across. You might have heard of paleontology for looking at really old things, but paleobotany is in particular a study of fossil plants.
00:04:06
Speaker
And so we're talking about fossilized structures, often things that are over about a million years old, but most of the things we're looking at are much older in the geological record, so about 300 or 400 million years ago are lots of the fossils we're working on. Okay, that's really old, yeah. I mean, so that's much older than the dinosaurs, obviously. And I think one thing that strikes me is that
00:04:28
Speaker
fossils have had a glorious history in the study of animal evolution and famously Darwin had a impressive collection of fossils which informed, actually indeed inspired his theory of evolution. But I've not seen the same sort of, I don't know, level of
00:04:51
Speaker
research going on in plant fossils. Is that fair? Yeah definitely. I think there's definitely less people who study plant fossils. I think there's in some ways there's often less people who study plants in general. They're often overlooked but the plant fossil record also has a huge amount to tell us and has also been really key for helping to build evolutionary theory because there's many things that are actually easier to study in plants than there are necessarily in animals and they give us
00:05:15
Speaker
an entirely independent view on evolution.
Multicellularity in Plants and Animals
00:05:18
Speaker
I think this is a really nice point to highlight is that animals and plants have both independently evolved multicellularity. So their common ancestor was unicellular and then the fact that multicellularity evolved multiple times in these different images gives us a kind of independent way to investigate evolutionary phenomena because there's no reason necessarily to assume that evolution is being played out exactly the same way in plants that are sessile and they're
00:05:42
Speaker
interacting with the environment in quite a different way to animals. So that's one of the main reasons why I think it's great to investigate plants. And another thing that I've noticed from your work is that you know every we've noticed this is looking at very very old plants and that also allows you to take a kind of longer view of evolution than if you're looking at more recent things. And one might just think oh well evolution is always over long timescales but this is you know much longer timescales than say the kind of
00:06:10
Speaker
the animal fossils that, again, Darwin was interested in. Yeah, definitely. So I think there's many different ways to study evolution over many different timescales. Lots of the ones that actually Edinburgh University is really famous for are these much shorter timescales where we're looking at individual populations. So you can actually study a population of
00:06:29
Speaker
sheep or rams or deer quite famously studied over a long time where you're tracking everything. I'm really interested in that but I'm actually interested in these much longer timescales as well to see whether those same dynamics that we see at the short scale play out over millions of years when they're interspersed with things like giant asteroids hitting the earth, huge changes in global climate, movement of the continents itself. So how do those things play out at the macro, these longer term timescales that we see at the micro level as well?
00:07:00
Speaker
And so yeah, key to this is having access to very, very old fossils, at least to the kind of paleobodeny part. There's then comparisons that you can do with modern plants. But yeah, we need some handle on what plants looked like a very long time ago. We're talking 300, 400 million years.
Ancient Plant Life and Evolutionary Insights
00:07:22
Speaker
Where do we get those? You mentioned fossils, but what kind of shape are these fossils in?
00:07:28
Speaker
I'm not expecting, one might not think that these are going to tell us that much if they're hundreds of millions of years old. Yeah, definitely. So let's break that down to a couple of points. So the first one is, whereabouts can we get fossils? So we're very lucky here in the UK to have huge museum collections of fossils. So many of the museums, including National Museum of Scotland, just down the road,
00:07:49
Speaker
has an entire warehouse of fossils which you can go and investigate. So there's obviously lots of these that are already curated if you are particularly interested in knowing what the dinosaurs ate or what was around when our first ancestors were coming out of the water. So that's a good place to start. However, the UK especially is particularly famous for some key time periods that include fossil plants and the most famous is the Carboniferous Period.
00:08:14
Speaker
So, Carbonin has buried roughly 360 to 300 million years ago. It's got the name Carbonin, it's famous for huge amounts of coal deposits. Now coal, you know, fueled the Industrial Revolution and the majority of these coal deposits we have in both the UK, in Europe and America were all formed at that period of time and they were formed by giant swampy forests known as the Coalswamp Forest.
00:08:39
Speaker
So where we're sitting here in Edinburgh 300 million years ago would have been right in the middle of a swampy forest. It's that forest that would have formed deep thick layers of organic rich peats and over long periods of geological time they've been compressed to form coal. So what's really great is pretty much wherever we have coal you also have
00:09:00
Speaker
other fossil plants. You'll also have lots of other fossil plants as well. So actually just down at the coast, even in Edinburgh, you can find fossil plants. And what they would look like if you had the rock in front of you now would be, often on these largest slabs, you'd have a black coley outline of a plant that would actually look really familiar. Lots of the time you're looking at things that look just like fern leaves today. So remarkably 300 million years ago you have this kind of foliage which looks incredibly similar to
00:09:29
Speaker
what you'd recognize today. And how detailed are these fossils? How much can we see of the form? Is it just a kind of outline, or is there more than that? Yeah, so it really varies. It varies between sites. So in lots of these ones associated with coal, all we're looking at is a compression, that thin, curly layer, which will often crumble off. So in general, you're looking at often the impression
00:09:53
Speaker
of the leaf itself. So that gives you, you can see the outlines of where the veins would have been and the shape of the leaf, but in many cases not that much more. However, move to some other fossil sites and things change completely. We get fossils that are preserved in three dimensions, their internal tissues are preserved,
00:10:12
Speaker
So a great example would be the petrified forest. You might have come across petrified wood before but in many cases petrified wood, petrified means that you've got typically mineral rich water has seeped into the wood and deposited the minerals within the cellular spaces.
00:10:29
Speaker
So actually in many cases the fact you can see tree rings in a petrified forest means that actually you've got the cells preserved and if you take one of those you know big a chunk of fossil wood and either you slice it into a very thin thin section a thin slice and look at it under a microscope you can actually often see individual cells preserved.
00:10:46
Speaker
So the preservation ranges all the way from those just COVID outlines that we find often quite commonly. And in many cases, you can actually go and find them yourselves, all the way up to ones where we can see individual cells in plants that grew over three or 400 million years ago. Yeah, that's mind-blowing that you can have that level of detail of resolution down to the individual cell.
00:11:13
Speaker
I suppose it's quite a unique mechanism that produces it, so it's this
00:11:17
Speaker
the minerals coming out of the water, do they crystallize then and kind of preserve it? And what I'm, you know, one thinks of kind of science fiction films where there's cryogenic freezing. This is kind of the equivalent of cryogenic preservation in a sense. And indeed, I suppose even if we were to freeze cells, generally that would harm them and sort of destroy the cell walls because as the water expands.
00:11:43
Speaker
So it seems so fortuitous that there is this mechanism that exists that leaves a record of something so old in such detail. Yeah, it's quite mind-blowing. So in the actual more lab-based side we're working on living plants today, we're obviously really interested in their internal tissues. And so the way we often investigate those is making similar thin preparations of those specimens as well.
00:12:09
Speaker
And typically, you would fix them in resin or in wax, and then you try and cut these very, very thin slices and look at the internal, you know, the preservation of the internal tissues. And it's remarkable that we do this on a day-to-day basis. So many of these ones we make with the living species, we just have to throw away because the preservation is not good enough. And yet, we've got these fossils from 400 million years ago where the preservation is actually even better in some cases than we can get in the lab. Yeah. It's kind of mind-blowing.
00:12:37
Speaker
And I'm curious, you mentioned that we have a lot of museums and cue gardens and other places where we have these really comprehensive fossil collections. Why were people picking up these fossils? What did they know about the things they were finding?
00:13:01
Speaker
Yeah, so I think we started with the collections in the UK and Europe. I'd say many of them have actually come, especially many of them are from the Carboniferous period when the Industrial Revolution fueled this hunt for coal. Fossils were just found alongside that. And because some of them look so characteristic, like living species today, they were collected.
00:13:23
Speaker
This is also around the time where people are trying to give names to species they're finding. So there's cataloging and also the development of the theory of evolution at the same time as well. So all of these things are combined that we're trying to understand how life might have changed through time and how they've been cataloged. So I think at that period in time, that's in the
00:13:46
Speaker
late 19th century when many of the big collections are being found. But there's records that fossil plants were found earlier and there's a lovely example called the Herbarium of the Deluge which is one of the first books written about fossil plants. Herbarium specimens are
00:14:06
Speaker
taken when living species are kept today and they're pressed. Places like Kew Gardens, like you mentioned, has an amazing collection as does World Botanic Gardens. And we use these as a record of plants and this is how we give plants and keep a record of which plants have which particular names. So this book was written because it was a herbaria of what they were interpreting as a great flood because they were finding these encased in rock.
00:14:30
Speaker
And this, I've forgotten what age is, but this is taking us back quite a bit earlier. So at that point, people were even able to recognize them as plants. But I think at that time it would have been difficult to, or they wouldn't be able to comprehend the long time scales we're talking about. Yeah. Although, I mean, the name suggests that they thought they discovered the, you know, the flora of the garden of Eden, I guess. Yeah. Yeah. Yeah. That'd be quite amazing.
00:14:56
Speaker
One thing that struck me from looking through your work is that these very old specimens are still generating new science. And so I know you found something really
00:15:11
Speaker
crucial in our understanding of the early development of roots. Can you take us through what that was and the specimens that were used and so forth? Yeah, of course. So I think the reason why these old fossils can definitely really lead us to new interpretations is that we have very different questions than when they were often first found.
00:15:32
Speaker
For me, I'm very interested in the evolution of new organs. How does an entirely new organ evolve? In the case of plants, most of my early work I did was all on roots. When did plant roots evolve? What can we learn about this? How much did it change the earth? When we're thinking biologically and developmentally, what does that actually mean to evolve a new organ?
00:15:56
Speaker
And so what we can do is we can take a starting place of living species today. The vast majority of living plant species today are what we call vascular plants. They have a specialized conducting tissue known as the water conducting asylum and the food conducting phloem. Now they make up the vast majority of living species and almost all their species develop roots.
00:16:19
Speaker
So we might predict that their common ancestor also developed a root and therefore that the presence of roots in all of these living species represents just conservation from that. However, when we turn to these early fossils, the story changes quite a bit because in the earliest fossils we find of fossil vascular plants, we don't find any evidence of roots. We find these really superficial kind of horizontal stems covered in these hair-like structures.
00:16:47
Speaker
So suddenly these fossils are giving us a really interesting view on a type of rooting system which you know we just don't really see in in these living vascular plants today. And so at that point the question still becomes okay we have a rootless common ancestor and we've got plants today with roots so what's in between those two?
Early Root Development and Geological Biases
00:17:07
Speaker
And there's a very key fossil site called the Rhiney Church, which is based here in Scotland, and has some incredible preservation of plants that are roughly 407 million years old. And one of the plants in there has these early rooting systems. So we thought, if there's going to be one plant that might be able to help tell us and inform us about this transition, it's definitely, this is definitely, given the preservation of this plant, astronauts, while in Mackay, might be able to give us, you know, real new insights.
00:17:34
Speaker
And so we hunted through specimens which are actually already in museum collections around the UK and did a survey of attempting to try and find all the thin slices of these specimens in museums around the UK. And it was while finding, looking through those that came across the very tip of one of these little rooting axes.
00:17:54
Speaker
And based on living species today, we know that the tips of a root are covered by a structure known as the root cap, which helps protect it as it grows through the soil environment. And yet this feature appeared to be absent in the fossil. And so this very early fossil, therefore, we interpret it as giving us a really unique view on how roots might have evolved.
00:18:12
Speaker
an ancestor lacked roots. And then we had this form we interpret as a transitional form. So in some ways it's kind of half, it's like a halfway route. It's got many of the features we associate with roots, but isn't quite there. And then we know in the living lycophytes today, the ones related to that species that they develop true reach with all the characteristics. So this was really interesting that it told us about the gradual evolution of roots in that group. And also what I think is most exciting is that if the ancestor of vascular plants was rootless,
00:18:42
Speaker
And yet, amongst this lycophyte lineage, we know it took quite a long time for roots to evolve in a gradual fashion. It implies that roots, as we know them today, have actually had two entirely separate evolutionary origins. Yeah, so it seems that, you know, roots are so important that kind of
00:18:59
Speaker
Well, to use the terminology of Jurassic Park, you know, life sounds the way, and it's developed them independently at different points. Yeah, that's really something. And I guess the root cap protects the root and helps dig into the Earth. You mentioned how important roots have been in changing
00:19:25
Speaker
the ground beneath us and actually atmosphere as well, I think you might have mentioned. And in going from this very, so initially very hair-like, I think it's rhizoidal, is it? Yeah. So very, very fine structures, which kind of the, you know, the first, if you like, iteration of roots, and then becoming, you know, burrowing deeper into the earth, or actually
00:19:56
Speaker
It strikes me that they were sort of creating that soil as they went.
00:20:04
Speaker
these very early plants were not long off the water and they were on an earth's surface that looked very different to how it is now. So yeah, maybe take us through what did the earth look like when we had the first plants on the surface and how were they adapted to that versus how they evolved and how the surface evolved as well. Definitely. I mean, first of all, it's very difficult to know exactly what the earth's surface would have looked exactly like.
00:20:29
Speaker
Part of the reason for that is it's very difficult to also pin down exactly when plants first evolved because the fossil record, we're working with plants around 407 million years old in the Rhiney Church, but we predict that fossil plants might have gone back the best part of 100 million years before that. And for a number of reasons such as biases in the geological record,
00:20:53
Speaker
we just don't really have a great record of this very early evolution. So it's difficult to say what was going on in the earliest period. Is that roughly because we don't have, you know, until you have enough matter building up of the right kind, these kind of PT charts, you're not going to have this kind of minimised water that's throwing through things and preserving them.
00:21:17
Speaker
So we just have like a kind of blind spot, I guess. Is that roughly... So that's definitely one of the reasons, but on top of that whole thing is this imprint of the rock record itself. Right. So the rock record we have is not representative of the geological period. So each geological period doesn't make up 10% of the record, for example. Instead, the Carboniferous Period, where we have huge amounts of coal, we have loads of terrestrial rock from that period in time.
00:21:45
Speaker
Devonian period before that, same thing. The Siloian period before that, as we get earlier, we have loads and loads of marine sediments and almost no terrestrial rock. So in actual fact, we know that period of time is famous for finding marine fossils. And yet we don't have the terrestrial one. So I think the rock record itself has imprinted and made it more difficult to investigate what's going on at the Devonian time.
00:22:13
Speaker
I guess, one issue is, yeah, we just don't know, we don't have a rock record which tells us quite like what the surface of the Earth looked like, but can we speculate? What do we think to the best of our, you know, science, I guess?
00:22:28
Speaker
Yeah, so definitely, I think it would have definitely looked very different to most places on the terrestrial surface today. We're used to seeing plants, we see plants almost everywhere. So some of the best analogies would be to go to places with many fewer plants or where plants make up a tiny subset. So some quite extreme environments, bits of the Arctic.
00:22:49
Speaker
would be great examples of that, where you have what we would call, and bits around some bits of deserts as well, a cryptogamic cover is what this has often been come to known as, and what that is supposed to encompass is that if you're looking at it from a distance, you can probably make out there's some sort of life, maybe some colours,
00:23:08
Speaker
And when you zoom in closely, you see there's just a range of, there's still quite a lot of diversity. There might be lichens, fungi, very small lamplands, all sort of hanging on together in this very, very small scale. And some of that life might be slightly below ground.
00:23:24
Speaker
you know, lichens and these early potentially moss-like mite plants are still able to bind together some of those soil particles and help trap other things. So they're leading to the kind of accretion of both more biological material but also bits of more sediment. But within that, again, as I said, there'll be definitely fungal life and similarities with cyanobacteria things.
00:23:48
Speaker
So I often think of it as a kind of barren, it must have looked like about, you know, initially it would look like a really barren inhospitable environment. I think if you zoomed in closely, you'd actually find there'd still be quite a bit of life there, but just not much which is large and multi-salar at this period in time. But then that all changes as we move into the kind of Devonian period of plants that are beginning to take off and get much bigger.
00:24:14
Speaker
So as we move into this Devonian period about 400 million years ago, yeah, how do things change? Yeah, so I think the first thing we really notice is, let's start the soil and work out, because that's where I've been working so far. So the first thing we definitely see is we start to see soils that are looking a bit more familiar. We've got rooting systems now penetrating to a variable depth. By the mid Devonian, we have roots at least a meter in depth.
00:24:43
Speaker
Wow, okay. So they're, you know, again, they're breaking up rock but they're also anchoring together rock. They're allowing life to extend deeper into these kind of soil environments. So I think the soil itself is changing. And would we have some roots of up to a meter deep and would the soil have been that deep already or were they sort of burrowing into rock?
Plants' Impact on Climate and Soil Formation
00:25:09
Speaker
Yeah, so I think
00:25:10
Speaker
It's actually quite a sticky subject as to what precisely is soil and how do we define it. Let's talk about that. The images coming up from the Discovery rover on Mars show a form of what people often call a regolith, a broken up, sandy type substrate on the surface. And it's a question as to when does that broken up sand inorganic type substrate turn into what we call a soil.
00:25:40
Speaker
And I think there's quite a kind of spectrum in there. So what you can definitely imagine is before you have plants on land, there's still going to be lots of sediment. There's going to be silts. They're going to be, you think about a kind of sandy beach and you think about changes to areas where there'd be more mud, more sort of mud rock.
00:25:57
Speaker
you know, entirely inorganic. So there's definitely substrates in that sense. So I think these things, they're borrowing, the roots are borrowing down most likely into this stuff. I think they're helping to break up rock, but I don't think they're not just kind of drilling straight into hard rock, but they're definitely, they're forming what we then move on to, you know, calling this thing like a soil because there is, there's organic life coming deeper in it as there's changes, there's the plants are actually moving water around.
00:26:27
Speaker
you know water's coming being brought up by the roots and they're also as they're being broken down they're putting carbon into these environments as well. So at this point I think it's again something where I think we'd be just inherently more familiar with as a type soil rather than just simply sandy sediment. Yeah it's really interesting it strikes me that so many things within the sciences are
00:26:47
Speaker
and philosophy are emergent and you can't quite say well one thing becomes another and you know one of the extremes you have completely barren you know
00:26:59
Speaker
dust I guess which is very very uniform but then at some point as you say you can imagine a bit of mud coming in and and then the other extreme you have something that's completely teeming with life and you know full of underground fungi and roots and and bacteria and so forth but yeah where one becomes the other like is is something that well we can we don't necessarily need an answer to I guess it's kind of
00:27:30
Speaker
depends on how you want to frame things. But as you said, it is clearly changing.
00:27:41
Speaker
and there's changes below ground and above ground. And is there a kind of feedback loop here? So you mentioned the change to the atmospheric constitution. What's going on? Yeah, so at the same time that these ecosystems are getting bigger below ground, obviously the bit above ground, which I think we'd spot instantly, we were standing there for the first time getting larger trees up to heights of, you know, the initial ones, you know, we find evidence of up to about eight meters or something, but these are definitely,
00:28:08
Speaker
Yeah, they're large, large organic structures. We're seeing the first diversity of branching structures, of leaves of the interval of this time as well, these big woody stems. So suddenly plants are there and we've got a kind of forest ecosystem. And this itself is really changing lots of the kind of biogeochemical cycles on the earth. So already mentioned water, but plants are really important in terms of taking up water
00:28:36
Speaker
and effectively breathing it out to the environment through the process of transformation. They're also mining for nutrients. So the kind of nutrients that plants need for their growth is also coming from directly mining it from the environment as well. So they're leading to different cycling, moving those nutrients to different parts above ground, which are then being broken down and recycled by other organisms. So these are changing. And then one of the most famous is actually how plants were able to change the concentration of CO2 in the atmosphere.
00:29:05
Speaker
And there's kind of two things that jump out for this. The first is that, first of all, plants are locking up a lot of CO2 in their own bodies. And when we think about it for going from an environment where there's just no forest to forest covering large parts of the terrestrial surface,
00:29:22
Speaker
you're actually ending up with quite a large part of that CO2 being locked up as carbon in their bodies themselves and as long as those bodies are maintained that's actually you know quite a large net store of carbon. And the other thing that they're doing is broadly increasing weathering rates and so the weathering of rock, weathering of certain types of rock called silicate rocks which are quite common,
00:29:46
Speaker
As they're broken down, there's a net drawdown of CO2 from the atmosphere as they're withered through this very, very long-term carbon cycle. It's a long gradual process, but the combined effect of locking up lots of carbon in their own bodies, but also increasing weathering rates, means that plants are quite remarkably able to change concentrations of CO2 in the atmosphere, and this is correlated with this big decrease in atmosphere CO2 levels.
00:30:16
Speaker
Do we know how that affected plants' rate of growth? I'm conscious now that we seem to see plants growing or we certainly do see plants growing more quickly with just a very small change. I don't want to downplay the importance of the change in the current levels of CO2 in the atmosphere as it's very precarious.
00:30:38
Speaker
relatively, we've gone from hundreds of parts per million to an extra hundred parts per million or so of CO2 in our atmosphere now. But I presume that the change in this period was much, much greater. Did plants grow more slowly because they were able to draw down less CO2 or was it actually maybe easier for them for other reasons?
00:31:01
Speaker
Yeah, that's really interesting. I think it's something we actually don't... There's no great answer to that. What we do know is that CO2 levels are being brought down towards levels that we see today. So before then, they're higher than that. And in theory, that might have meant that plants might have been able to grow faster, like you suggest, because it's easier for them to get CO2. But that's our hypothesis, which would be a really difficult test.
00:31:24
Speaker
about the lifespan of the plant. One thing we definitely do see is that there's a correlation between the levels of atmospheric CO2 and the small pores that we get on plant leaves caused the tomato.
00:31:38
Speaker
And these pores are really important because they're the valves that allow gas exchange from the outside, from the atmosphere on the outside to inside the plant where they're then used for photosynthesis. And what we find is that when levels of CO2 are very high, plants can get away with having not that many stomata because you don't need many pores to let in the CO2. This is good because plants are always playing a game, a trade-off game.
00:32:04
Speaker
because as soon as you have pores in your leaf, these are the places where water is being lost. So plants are always playing this careful balancing game between how many pores you have and how open they are, therefore how much water you're going to lose, but also the requirement to have them open to get CO2 in. So at a time when CO2 levels were super high in the past, they might have been able to have a bit of a different physiology where they maybe didn't need as many pores open to get in that amount of CO2.
00:32:31
Speaker
So that might give us some clues about the trajectory for plant evolution as, yeah, in a time of rising CO2 levels. So I guess we might expect again that it will have kind of smaller pores like this. Yeah, definitely. I think it'd be really definitely very interesting to fall in the future and actually this pattern was actually recognised when looking through
00:32:53
Speaker
much more recent data from herbarium specimens where they were able to investigate this from looking back over the past 50 to 100 years about the way the number of stomata on leave were changing levels of CO2. So it's interesting, this is something we've learned from living species and then we know how to put it into the past and use with fossils as well. That's incredible. Yeah, slight tangent. Is this something where
00:33:21
Speaker
We should be using our knowledge to do selective breeding, for example, and say, okay, well, we know how things are going to trend in terms of carbon concentration in the atmosphere, whereas
00:33:34
Speaker
plants don't know that, they kind of react to it. But, you know, maybe we could get ahead of the curve here and, you know, try to create plants which are better adapted to this kind of new unfortunate system or scenario that we put ourselves in.
Adapting Plant Traits for Climate Change
00:33:50
Speaker
Definitely. No, I think it's a real error of research. I know the lab of Professor Julie Gray at the University of Sheffield
00:33:57
Speaker
is definitely working in that area in that you've managed to identify mutants which change the density of the number of stomata you have and then think of those specifically in the context of croplants because lots of the research, the fundamental research we do is on model species that one in particular called Avalopsis thaliana which is
00:34:16
Speaker
a type of crest. It's important for us because it's a system where we are able to pin down and really understand so much of the biology of the plant but doesn't necessarily translate instantly to crops. I remember with Julie's work being able to actually extend that into crop species and to be able to modify stomata on crop plants is just like you say a really interesting trait that will become really
00:34:42
Speaker
more useful yeah and presumably yeah it would make them more drought resistant or more resistant to
00:34:51
Speaker
drier air, I suppose, and transpiration losses. Interesting. Yes, so okay, so where are we? We're in the Devonian period.
Devonian Plant Features and Fibonacci Patterns
00:35:02
Speaker
We've seen eight metre tall trees growing up. We've seen, I guess now, we've got proper big roots to support that, fully with root caps and so forth.
00:35:16
Speaker
What next? Any other innovations that you'd like to highlight from this time? For me, this period of time is really exciting because it's when I think the body plan is forming. We're beginning to see leaves and roots and plants that we're relatively familiar with at the moment.
00:35:35
Speaker
One thing in particular we're noticing is leaves, as I said, and leaves are actually going to be arranged in characteristic patterns. And some work that we've just had published recently is actually giving us kind of illumination into some of these early leaf-like patterns we're finding in the Devonian.
00:35:52
Speaker
So what you might not have noticed is that plant leaves are often arranged in quite precise patterns. This is most apparent if you look at something, some rosette type plants or a subfluent plant, where you can kind of look down from the top, you can see that they seem to be arranged in patterns and often those patterns are in spirals. So you often see spirals of leaves, if you turn a pine cone over you'll see that there's the arrangement of those reproductive structures are in spirals, you see spirals and flowers.
00:36:19
Speaker
Actually, these spirals seem to crop up everywhere. The more we look in plants, the more we find these spiralite structures. And what's been interesting is when they've been investigating and kind of quantified is that these spirals are often described by integers in the famous mathematical series, the Fibonacci series.
00:36:39
Speaker
And so, again, because Fibonacci spiral is a bit like the same story of roots, really, because they're so common today, it was always assumed that they must have been there, they must have been ancients. And so again, these early fossils, again, looking at fossils in the Rhine Church that we just recently examined.
00:36:55
Speaker
again in that same species, Astrootsul and Machiai, we were able to look at the arrangement of its leaves and we found that they were spirals but remarkably they were actually non Fibonacci spirals. So this seemed to indicate that in fact if we were standing in the Devonian we'd see that leaves were arranged but there's a reasonable chance that many of these plants would have types of arrangements that we're just not as familiar in seeing today and actually at a later date these Fibonacci spirals we're so familiar with today must have cropped up.
00:37:24
Speaker
Yeah, and I think that seems to suggest that there might be kind of multiple, again, multiple ways which leaves have evolved because this, I'm going to pronounce this wrongly, but the astaroxylon is sort of the ancestor of club mosses.
00:37:48
Speaker
we know that other types of plants which do have evolved their leaves kind of on a separate time scale and and therefore yeah again like they seem to have come up with these innovations separately and led to kind of different yeah
00:38:05
Speaker
arrangements of their leaves, which is quite surprising perhaps. Definitely. Yeah, I think it's still something that strikes me as just remarkable about convergent evolution where through the course of evolution, similar shapes and forms are cropping up many times independently. And leaves are a great example of that. And in this case, even the arrangement of leaves, these Fibonacci spywalls seem to be cropping up in multiple images separately. In some ways, it's quite funny, quite interesting with a trait like Fibonacci spywalls where they're so common today.
00:38:35
Speaker
to try and understand, you know, what's going on in the few groups that don't do it. Yeah. And that's what I found so exciting about this early fossil, because suddenly we, it gave a kind of new perspective. They'd always been thought anything that wasn't Fibonacci was always thought as a kind of an oddball, something that I just
00:38:51
Speaker
and very recently maybe gone off on its own track, whereas this seemed to say in the case of this group of lycophites that actually that inherent diversity, those kind of different types really had a really long evolution in history. So what does that mean, evolutionary? And I think that's something we would definitely want to like to try and investigate in more detail. Yeah, it's interesting because it seems that there's been a lot of effort to try to understand
00:39:13
Speaker
why the Fibonacci numbers. And we should say, so I guess the way that the Fibonacci numbers fit in is that, yeah, it strikes me that there's been lots of thinking about why the Fibonacci sequence crops up here and in lots of places in nature. And it
00:39:36
Speaker
It is an interesting thing to explain because it's kind of a non-obvious way that it crops up in these spirals. So you count the number of spirals going out in one direction, and then you count the number of spirals going out in another direction, and they are Fibonacci numbers. So they're numbers within the sequence that appear next to each other.
00:39:52
Speaker
As a reminder, the Financi sequences is the one which goes, so each term is the sum of the previous two terms, so it's 1, 1, 3, 5, have I got that right? Yeah, previous three terms, is it? No.
00:40:08
Speaker
Let me get this right. One, one, two, three. One, two, three. I left out with two. One, one, two, three, five, eight. Okay. Get there in the end. And I guess, you know, there is a kind of natural relationship between those numbers and growth because if you have a process where it's, you know, the next generation depends on the previous two generations, you can kind of see naturally how this sequence might represent something. And there's also ways of thinking about how
00:40:39
Speaker
how things like Fibonacci spirals, which are also called the golden spiral, how they can evolve from particular ways of, for example, arranging boxes. And so it has various properties, which in some contexts are quite easy to understand how they fit into nature, although fascinating nonetheless.
00:41:03
Speaker
One example I really like is why you have so many shells which have these follow the golden spiral. And one explanation is just it's a scale-free spiral, so as the organism grows and grows and grows and grows, each it can move into kind of successive compartments within this shell and build them out. And its shape doesn't need to change.
00:41:33
Speaker
So there are places I think where it's quite well understood but for these it took quite a while I think to understand why leaves were arranged in this way and if I understand correctly it turned out that actually it's just the optimal way of packing them so that they receive as much light as possible even as they're growing.
00:41:59
Speaker
Yeah, so what's interesting is I think that is definitely one of the main hypotheses for why
00:42:06
Speaker
Yeah, why they should be arranged in that way, in the sense that, just like you say, they're arranged so that a leaf will capture as much sunlight and then will minimise on the shading of the one below. And it's also a patchy one. However, contrary to that, if that really was the case, then you might also expect that plants would modify their arrangement quite easily. So if you grow it in a low light environment or a highlight environment, you might expect them to change their pattern. But in many ways they don't. Instead, they change the actual shape of the leaf.
00:42:36
Speaker
One way if a plant's in a shady environment, they'll change the position of the leaves, they'll actually change the overall shape of the overall shape of it, and yet the actual patterning and the arrangement is one of the things that plants don't change. There is still this really big unanswered question about what is the selective advantage, and is there really a strong selective advantage for why they're so common?
00:43:04
Speaker
Capturing light is definitely one of the key ones and packing efficiently is definitely another one that's been cited for things like sunflower heads where you want to pack in as many of these reproductive structures altogether. But there's also from the side you mentioned the kind of packing of boxes and the fact that these are almost self-assembling systems. There's also a
00:43:23
Speaker
a prominent view that in fact this pattern which is found so common in plants is simply just there because it is a convenient way of growth and I find that really fascinating to have something which is so common in plants today but might not have and that we're still uncertain about what the real adaptive significance of it is.
00:43:44
Speaker
that's a fascinating way of thinking about it because it sort of de-emphasizes the evolutionary fitness and says well maybe this was just, it's just easy to produce like the factory makes this easily. I think that there is a kind of tradition of thinking about that which goes back to someone here in or nearby in Scotland to
00:44:07
Speaker
Darcy Thompson and his book on growth and form, where actually he looked at a lot of these golden spirals and things and he said, well, yeah, okay, evolution is clearly important. I'm pretty saying a lot here, but maybe let's look at kind of the chemical events, I suppose, or kind of gradients that might lead, for example, to
00:44:33
Speaker
If you think of like a horn's spiral, you know, if you have that growing, if you have some bone growing more or a horn structure growing more on one side than another, you will get a spiral pattern as it just grows slightly faster. And you can quite easily get a logarithmic spiral doing that or a Fibonacci spiral.
00:44:55
Speaker
if the rate of growth changes with your distance from a kind of origin. And again, that seems quite easy to understand why there could just be almost mechanical things or chemical processes which cause that.
00:45:11
Speaker
Whereas on the other hand, it strikes me as very hard to explain that from an evolutionary point of view, because even if there's an advantage to that, how do you get something that's so precise, you know, in creating this Fibonacci shape, you'd expect it to be, you know, just kind of good enough, right, slightly off, but to get it down so precisely, I think is hard to explain.
00:45:32
Speaker
So, yeah, I do find this kind of picture really fascinating. And it also opens the question, you know, why, again, why do we not see this kind of Fibonacci arrangement for Club Mosses now and for the
00:45:51
Speaker
looking a bit astro-exile on the kind of ancient plants that you studied.
Leaf Pattern Experiments and Club Mosses
00:45:57
Speaker
Yeah, what could be the mechanisms that are producing that and is there some advantage? Exactly and this is I think what gets me really excited about this. So the work I described earlier about routing systems where we found the route that lacks the route cap and we interpreted it as a transitional form that helps us understand how this new organ evolved
00:46:17
Speaker
So that itself, the fossil was incredibly informative and I think it's, yeah, provided this great point of reference for beginning to understand root evolution. But one of the difficulties with that is that we don't have a diversity of living plants today that lack a root cap. Everything develops a root cap today. So in some ways the fossil is really important but we can't actually begin to do any experimental testing on the living relatives that easily because again,
00:46:42
Speaker
We don't find it in the main species and even some of the mutant lines we find is there. There's only a couple of genes that we know that will really disrupt blue carp. What's exciting about this example with phytotatsy is just like you said, some of the living relatives, these living club monsters, still develop this pattern.
00:47:01
Speaker
And so that means we can, for the first time, the hope is to actually be able to actually do some experimental testing to really begin to try and drill down into this question. What's going on in these living species today that is doing a very similar pattern to a species 400 million years ago?
00:47:16
Speaker
And we can actually maybe, or hope to be able to test some of those hypotheses. Can we grow this plant in different light conditions? Do we see changes? Is it a kind of structural feature? So when we find different sizes of plants, yeah, a whole range of hypotheses where, yeah, can't wait to dive into really. So this is kind of where the molecular part in the name of your lab comes in. So you have, you've done the, you've had this kind of
00:47:42
Speaker
groundbreaking discovery with the fossils, that's the paleobonany, and we should say, because you're probably too modest to mention it, that was just published in Science by the time this goes out, probably about a month ago, but you know, very recently, so congratulations. But now, yeah, that's almost like the beginning of a new research program, where you're like, okay, we know this is not just a flash in the pan, as it were, right? It's not something
00:48:10
Speaker
This, this fire taxi, this way of arranging leaves has not just evolved as a kind of random fluke. There's something interesting to look at here. Can we see what it's doing for the plant, how we can affect it?
00:48:24
Speaker
switch it off, switch it on, maybe. Yeah, so take us through a little bit about the checks there in more detail. Is there kind of gene editing involved? Yeah, definitely. So this is, yeah, I just said that in active area research, we can't wait to kind of dive into more. And obviously, there's a couple of ways you can approach this. Obviously, we can focus on these club mosses alive today. And I think that's going to be our starting place. I think
00:48:50
Speaker
There's many things we want to do at quite a fundamental and basic level, which is just to be able to visualize in more detail and through a time course for how they develop. So the fossil, we were very lucky, I think in total was it five samples we have, five or six samples, which for a fossil study is quite extensive.
00:49:08
Speaker
to a biologist that's a terrifyingly small sample size so we can't wait to be able to you know grow a whole range of these plants and then really begin to tease apart how they're developing so that some of the things we want to quantify are the kind of distances and the angles between these newly developing leaves to see whether they follow a regular pattern whether there's irregularity in there already and so that's something again we're really looking forward to doing with the living species and then to dive in further then
00:49:38
Speaker
Sadly, we can't do any genetic modification on any of the club mosses because the techniques are just not currently there to be able to do that. Interesting. So that kind of leaves going to two approaches. One is we go hunting around for other unusual species today, maybe flowering plants where some of these techniques are there.
00:49:56
Speaker
that we can look in more detail. Or we can think about rather than using gene editing techniques, whether there's any other approaches we can use. And one of the approaches that we're really quite excited about is microsurgery experiments. So we actually learned a huge amount about the arrangement of leaves through what are now famous experiments done on the shoot tips of flowering plants using surgery experiments. So what they found was that
00:50:25
Speaker
if you took a shoot tip and you made a very small incision right at the tip of the shoot and you separated one developing leaf away from the rest of the growing apex, that you were able to see that this tiny little incision had a really big impact on where leaves were going. And this began to indicate that leaves themselves were forming an inhibitory field around them. So a small leaf would actually stop the development of a leaf too close to it.
00:50:52
Speaker
And this was illustrated with the surgery ones because when you made that incision, you were able to break the patterning and leaf would form some ways closer together than we'd expect them to. So this is a really nice way about how we began to understand the way that leaves are patterned in flowering plants today.
00:51:09
Speaker
But those experiments have never actually been done on these unusual club masses. So for us this seems like a really logical place to go and have a go. And I think it's going to be technically pretty difficult, but we're definitely going to have a go at seeing where we can replicate those experiments.
00:51:23
Speaker
am I right in thinking that leaves and roots grow from basically stem cells, kind of meristem? Yeah, that in itself is really amazing and I guess it's why cuttings work at all, that you can just take a little bit of something and it produces a whole new version. But I guess that's maybe part of why
00:51:43
Speaker
these techniques are so fruitful because it's not that the cell has already decided what it's going to do. There's some kind of signal, there's something about the way that it's arranged, like structurally, chemically, whatever it is, that when you situate it differently, it behaves differently. I find that completely
00:52:04
Speaker
Yeah, completely fascinating. Yeah, I think plants are amazing in that respect. And it actually takes quite a long time. It definitely took me a long time to really begin to appreciate what you are really seeing when a plant continues to grow and give our new leaves. Because most studies of development in animals, many of them are done at the embryonic stage when embryos are being patterned. Whereas in plants, this is just continuing to happen. So if you're interested in the origin of a new leaf, if you compare that to one of our limbs,
00:52:33
Speaker
The plant is just producing these on a regular basis from a shoot tip and you can let it grow for a bit or you can watch entirely new organs develop from this population of these stem cells and as they differentiate and you can just keep watching that as the plant continues to grow and as you said you can take cuttings, you can move them on to different media, you can
00:52:54
Speaker
Yeah, produce a ball of these stem cells and then get multiple of these plant cuttings that are all genetically identical from the cuttings of that. So yeah, I think plants really are quite beautiful systems to work with asking some of these developmental questions. Yeah, I'm being quite speculative here but it seems that plants are in some ways continuously embryonic. They're always able to develop and that
00:53:21
Speaker
When one looks at nature, that seems somewhat evident. There's a certain kind of plasticity to plants that animals don't have. Humans look more or less all the same. We reach a certain stage of development and we don't adapt around that much. But if you put a plant
00:53:39
Speaker
in different conditions, it will look in entirely different, it can grow to very different sizes and yeah, I can't help but thinking there's some kind of link here between this
00:53:54
Speaker
very fundamental different ways that these forms develop. Yeah, definitely. I think that, yeah, having those populations of stem cells, you know, housed in what we call, yeah, meristems, just gives plants a real plasticity. It means that as we're, you know, viewing kind of growth and through time of the plant, you really are being able to see lots of different stages of development all played out at different periods of time on that same plant, which is, yeah, really, really exciting. It takes, as you said, it takes a while to get your head round.
00:54:21
Speaker
There's not, you know, there's not within, within a seed just a tiny little plant which then just gradually enlarges it actually is a isn't actually changing, changing process.
Appreciation for Ancient Plant Lineages
00:54:30
Speaker
Yeah, that's, that's wonderful. It arises something I wanted to ask you actually which is, you know, as you walk around let's say you go to the Botanic Gardens which just down the road from, from here.
00:54:39
Speaker
or if you're in the woods or if you're near some rocks. How has your work informed the way that you look at all the things around you? Yeah, so I think the most simple one, which will be testified by anyone who comes out with me, is that I'm probably going to spend far too long looking at what other people might class as some boring bog plants.
00:55:00
Speaker
So definitely at the gardens, especially because I'm working on these older plants, many of these plants, the vast majority of plants we work on, all evolved, or the lineages they're in, evolved before flowering plants. So I haven't yet graduated to flowering plants myself, which is what most people are interested in. So you'll find me definitely scuttling around the ferneries and looking for these early club mosses. And I do find these
00:55:25
Speaker
Yeah, these organisms are just really fascinating and can definitely be found, you know, there's a number of native club mosses in the UK and I'm always excited to find them and the same with the gardens, botanic gardens, especially the kind of fern house that has these quite amazing species because each of these lineages have done, you know, they've been on their own evolution trajectory for
00:55:46
Speaker
three four hundred million years compared to flowering plants. You know they've been going down these different paths for such a long time so there are similarities but it's also the closer you look the more you also find some quite unusual differences as well.
00:55:58
Speaker
Yeah, and I expect you're looking pretty closely. Are you sort of trying to count the number of parastetias, as they're called, these kind of spirals coming out? Yeah, and frankly, it's always really difficult. For lots of those, you really want to take them back to the lab, but I do find myself definitely just looking at the biology and the shapes of these things in a lot more detail. But it is, yeah, and it's extraordinary because, I mean, I would look at these things and I just wouldn't know what I'm looking for, but it makes me think of
00:56:27
Speaker
the story of how you found the lack of a root cap. And that was something that had been just missed for 100 years because people, as you say, they just didn't necessarily know what was interesting to look through. And I think you mentioned that you looked through hundreds and hundreds of species for that. So you really kind of knew what was interesting to find because you had to just get the right angle of cut on the fossil that someone had taken way back when.
00:56:55
Speaker
that would show you this. I'm curious, did you know what you were looking for? We're stepping back a little bit. No, but I think that's right. There's a kind of adage, and they told you that you only found it because you believed it. And I think there's this kind of element that you do need to have a search image when you're looking through that. So the fossil specimens we're looking through are these thin slices that effectively fossilize soil. And so it's just a crown full of stuff.
00:57:23
Speaker
I think it's almost impossible to, you can't take in all the information so it's really good to have a, you need to go with quite a specific search image in your mind about what this might look like and again that goes back to the living side of the work which is so important for my lab which is, we do a lot of work with the living species where
00:57:42
Speaker
you know exactly what that thing that that route looks like before you make a section of it and so knowing that means gives you real insight into okay this is the kind of structure i'm going to be looking for in the fossils yeah you're going to go hunting for that but
00:57:56
Speaker
I have a colleague here in London and she works on fossilized fungi. And what's really funny is I think that both of us will broadly overlook. I will look at the roots and barely see the fungi and she will look at the exact same specimen and be looking and be spotting all these different diversity of fungi and not see the roots. So again, I think you got your eyes kind of get in. Yeah, you have a kind of search image in mind and then your eyes are kind of drawn to what you're interested in.
00:58:23
Speaker
It's fascinating that they, you know, maybe you've looked at the same slides and, you know, one man's junk is another man's treasure as well. But it's just one of the things that, yeah, there's so much richness in this record of
00:58:38
Speaker
Do we call it herbaria? Is that all of the fossils? Yes, so the herbaria are more for the living species. Whereas these ones are just amazing. Just like natural history collections. Yeah. But yeah, I'm such an advocate for the importance of maintaining collections. And there are enough stories, there's terrifying stories all over the world constantly of large collections just being thrown in the bin. Yeah.
00:59:04
Speaker
I know you have a story about this, actually. No, exactly. This is in my work when I was a PhD student in Oxford. I worked with a remarkable box of fossils, which used to be a teaching collection. So they were fossil-thin sections made around 1900. They were bought at that time by the university to be used and
00:59:24
Speaker
brought out for students really to look at during the practicals. And this had just gone on for so long to the point where there was no one teaching this stuff and it just became this kind of dusty old box. And at one stage during a large clear out, this and a load of these other old teaching specimens just I think physically went in the skip. Fortunately for me, have people who had a real passion for saving and understanding of collections and Stephen Harris,
00:59:53
Speaker
he's now in charge of the herbaria in Oxford, had noticed this and said, you know, these are actually really important, we should keep these. So he accessioned them into the herbaria. And it was this box that I investigate and we got the work from just this old, old box of fossil contribution to three new papers and a real change in our understanding of rooting systems, including this one apex. We'd never seen anything like it before, you know, able to give it an entirely new name to science. Again, coming out of a box, which was almost lost,
01:00:23
Speaker
Yeah, I think it's always important to realise that, especially with new questions and new techniques, we can really begin to ask some really exciting new questions. That's brilliant. I think in the Hollywood dramatisation of this, which I have half of this, you'll be sort of running to the bin yourself and sort of pick it and you say, I found it! You know? So, yeah.
01:00:49
Speaker
it is wonderful just the richness yeah that we've inherited both you know from 300 million years ago but also from from these collectors about 100 or so years ago uh sort of for me proves the importance of being a hoarder or give some kind of justification for that um yeah particularly given that
01:01:13
Speaker
people back then didn't necessarily know the value of what they were finding. Yeah, one thing I was curious about is you've done a lot of work. Just having these fossils is the beginning of trying to understand what they tell you. And you have to look at them in great detail. And you've mentioned how you kind of reconstruct them. Take us through
Digitization of Plant Collections
01:01:38
Speaker
some of those techniques. And I'm also curious how
01:01:40
Speaker
technology might change this. Is there a kind of program to digitize the fossils that we have or kind of somehow catalog them, if I can say that correctly, so that you don't have to traipse around between all these different collections?
01:01:56
Speaker
Definitely. So I'll start off answering that part first, and then we'll go back to the actual making, the kind of 3D reconstruction. So I think digitizing collections is absolutely transforming the science we can do. I think the best story for this comes from Haverian specimens, those flattened plants. What's nice about them is they're flattened. They're typically on flat pieces of paper. And so they're ideal to scan. And so very, very high resolution scanners
01:02:25
Speaker
are used to actually scan copies of them which include basically the plant itself but also the barcode and where it was collected so they can then be geotagged and these resources are just remarkable and there's been efforts all around the world to do this and it means that if you're interested in a particular plant group you know whether it's coffee or whether it's you know whichever
01:02:49
Speaker
is getting you excited. You can actually look on the haberian about all around the world, where these specimens are, where they were collected, who collected them, what age they were. If you wanted to know whether the structure of their leaves managed to change through time,
01:03:06
Speaker
you can take that sort of approach. You want to know how they might respond to climate change or their previous distributions before they went extinct, for example. It's all recorded in these digital herbarium specimens that you can then examine. And when you find ones that are really interesting, you can then just go and you can either loan the specimen or actually go and have a look at them in more detail. And on top of that, again, to just continue with herbarium specimens for the kind of innovation with them is the techniques for genome sequencing are now so good that
01:03:34
Speaker
depending on the age of these herbarium specimens, the DNA becomes more fragmented. But especially even more recent ones, and even the ones that are more fragmented, we can still learn a lot from them. So actually doing ancient DNA preparations from specimens collected by people like Darwin, but also, you know, great naptists at this kind of time, means we can actually learn a huge amount about where they sat within the family tree of that group, and also how their genes have changed through time.
01:04:04
Speaker
In general, I think that's just a really nice example. From the fossil side, they're a bit more difficult. Fossils are inherently a bit more 3D, a bit more difficult to digitize. However, there's some really nice new technology which is allowing us to quickly and easily make really high resolution digital 3D models of fossils.
01:04:23
Speaker
And I think, again, that just opens the door to, I can sit here in Edinburgh and, you know, rotate and zoom in on a fossil specimen I'm really interested in, which is in, say, Montpellier in France, where they have some fossils I'm really interested in. So I think that that itself does open up the door for just asking new questions. So I think that's from the kind of collection side. And then finally also, yes, there's a lot of big
01:04:49
Speaker
Yeah, big innovations going into and money going into trying to digitise and catalogue fossil collections because it's a huge, huge job. It's a kind of terrifying job if you talk to people who work in collections, if you know big collections, the museum here will have millions of specimens and actually just trying to work out how to digitise and catalogue them all is a huge job. But I think it's a really important thing and it'll open the door for the future. Yeah.
01:05:14
Speaker
But yeah, and then you ask about the kind of 3D ones. So in general, we're really interested, especially in these fossils that, once upon a time, things like the rhiny chert where we had this great level of preservation. Great level of preservation typically comes with a trade-off that they're often in tune within nodules.
01:05:30
Speaker
mentioned about the kind of per-mineralization earlier, where you're encased in a matrix of a mineral. That means you can see cellular structure, but it's incredibly hard to picture what the actual plant or organism would have looked like in 3D, unless it's really tiny.
01:05:47
Speaker
And so new 3D digital reconstruction techniques are allowing us to take images of these blocks and then turn them back into these actual 3D renderings of what they would look like. So classic approach would be things like micro CT imaging, which is similar to the kind of CAT scan that you could go and get in hospital that would use these on rocks and then basically, yeah,
01:06:14
Speaker
If it works well and you get to good contrast, you can extract the fossil out of the matrix without having to touch anything at all, like destructive imaging. And then for some of the things that we're doing where they don't work as well for scanning, we can take lots and lots of serial thin preparations and digitally stick them back together. So you have to slice the fossil into lots and lots of pieces and then you kind of, yeah. Yeah, so that's what we've mainly been using. As I said, the gold standard is always going to be non-invasive imaging.
01:06:44
Speaker
However, sadly, what you really need for that to work is density differences between the fossil and the matrix it's in. And sadly, lots of times, lots of the things that we scan, especially this plot divider, just when you render it up, just comes out as a great blob. So then he said, making lots and lots of thin perforations, digitally sticking them back together. Yeah. Although one wonders as well if there will be some advances in that kind of
01:07:14
Speaker
microscopy or scanning techniques, which means that suddenly you can see the differences. Almost like the way that I'm sure that the original collectors couldn't have imagined the way that we're able to zoom in and reconstruct things in 3D as we are now.
01:07:31
Speaker
Definitely. I'm sure there will be, and I think that's why it's so important to, as much as possible, minimise full destructive imaging. And if you do have to do some sort of destructive imaging, there's, ideally, say you have a block and you're able to cut it in two and preserve one half of it as a specimen in a museum, even if one half of it gets destroyed, just so that people are still able to have some physical specimen from that block in the future for further examination.
01:07:58
Speaker
It's kind of ideal, but yeah, that's why these non-invasive techniques have just been so, so great. And are we still collecting, you know, as a culture, are we still collecting a lot of fossils or is it something that's
01:08:13
Speaker
you know, we've inherited these great collections, but we're not really replenishing them as it were. Yeah, I think there's definitely lots of people who still do a lot of field work. I spend most of my time working with museum collections because I think there's always a tendency. Lots of the people who like doing this kind of research also enjoy going and finding the new stuff themselves. And so I think in many cases, there's more specimens in museums that, you know, hold the answers to lots of the questions we're asking at the moment and then necessarily having to go out in the field and collect them.
01:08:43
Speaker
There's other cases where new sites are found where they're just giving just remarkable new insights. And so I think field work is always going to be intrinsically important. And I think what's so nice about that now is now that we have a better understanding of how to catalogue and how things might be used in the future.
01:09:01
Speaker
It's really important to plan any fieldwork and any new collections with this idea in mind that you might want to preserve the key bits of it and label it in a way and collect information that you might not think is necessarily quite as important today about the method you use to collect it and things that someone in the future might be doing in analysis.
01:09:20
Speaker
but they might really need that. Yeah, yeah, that's fascinating. And you actually, before becoming a kind of botanist or paleobotanist, you were a geologist, so I guess you've kind of really bridged these worlds. And it always strikes me as interesting that geology is this field which has on the one hand people who are interested in kind of oil and gas and how to get those, and then the other people who are interested in fossils, which seem so desperate or so different, although there's clearly a link. Yeah, how did you find that?
01:09:49
Speaker
transition and what prompted you to make it? Yes, I really got interested in geology just because I was really drawn to trying to understand the earth over geological timescales and I studied geology at the University of Bristol which is a fantastic geology department and just that you're saying it's a really really interesting and disparate course really and it covers everything from beginning to understand a bit more about
01:10:17
Speaker
how the climate has changed through time, how the continents have moved, how a volcano functions also about trying to understand life.
01:10:24
Speaker
through the time and then on top of that there's also the whole range of geosciences which is encompassed within that as well which is not just about fossil fuel reserve but really thinking about renewable energy and energy sources.
Paleobiology Techniques and Phloem Evolution
01:10:36
Speaker
So I really enjoyed being exposed to all these really disparate types of things but got really inspired by the what we call paleobiology in Bristol. So Bristol University is really famous for
01:10:50
Speaker
the study of paleobiology. So I think often when people think of paleontology you might be thinking of you know just maybe just kind of investigating some bones of a dinosaur maybe. And paleobiology again is similar to what we're trying to do is to really interpret and use more techniques from biology and thinking often from biology about actually interpreting
01:11:14
Speaker
these organisms and ecosystems in their actual life, what they would have been like in terms of life and their evolution. So had some really inspirational lecturers, especially Professor Phil Donahue and Mike Benton, who introduced these, yeah, the ways of asking these questions about, in particular, the origins of animals or the diversification of things like dinosaurs. And for me, what really struck me at that point in time was that these really exciting questions were
01:11:43
Speaker
especially they were being asked in Phil's lab at the time for the origin of vertebrates, the origin of jaws and teeth. These same questions were out there for plants and yet there was less people investigating them. So I decided after having this background of
01:11:58
Speaker
of geology that for me what would be really useful is to jump over to a plant sciences field and really nest myself in an environment where everyone's working on plants even if they're mainly doing it or almost exclusively doing it on living species to really learn a lot more about the methods to study living plants and then we could marry those together with the fossils.
01:12:17
Speaker
Yeah, interesting. So yeah, you sort of first like went quite far away from it by looking at living plants and then kind of now you're back in the middle, I guess. Exactly. It seems a good way of doing it. You've got a steep learning curve that way, I mentioned. No, I really enjoyed it. I think, you know, via osmosis, you just begin to pick up what's around you. And I did really value just being surrounded by, you know, the talks, the departmental seminars were on all sorts of topics linked with plants, you know,
01:12:45
Speaker
way outside my comfort zone, but you gradually began to pick up things about methods of how we interrogate and ask these questions in a range of living species. And then you also began to realise about what were some of the key features that people were interested in. So an example of that were memory stems you mentioned earlier, populations of stem cells.
01:13:03
Speaker
seem to be, you know, if you're interested in developmental biology and understanding, you know, plant growth and development, this is so important. And yet they've really been, haven't really seen the attention of fossils. They're obviously, they're not very likely to preserve, but they do occasionally. I think that's kind of what motivated my interest in trying to find these root meristems in the fossil record. Yeah. Yeah. It is incredible that you, that you can see such tiny structures. And as you say, at the cellular level,
01:13:33
Speaker
Yeah. So it's a lovely day here in Edinburgh. So I feel very guilty about keeping you indoors all this time, when you could be out looking at what to some may seem very boring plants. But I think we now realize the fascination of
01:13:54
Speaker
yeah looking at club bosses and and so forth. So I don't want to say too much of your time but yeah I'd kind of love to know you've talked a little bit about what's next in terms of turning to the molecular side and looking at yeah how we why
01:14:11
Speaker
what more we can understand about the mechanisms for this phyllotaxis through results that you've discovered recently, like why these things don't come over the Fibonacci sequence. Are there other things you're working on? Yeah, what else is that? What other coals are in the fire?
01:14:28
Speaker
Definitely. So the big one, which is our common focus. So the Phatataxi turned out as being an interesting project because it kind of came out of nowhere. It was a project that was ideally placed in lockdown because it was all digital. We're doing the digital reconstructions.
01:14:44
Speaker
But more generally, the real focus of my lab at the moment is the evolution of the phloem. So the phloem is the sugar-conducting tissue in plants, in the group of plants, the vascular plants again. And the phloem is just absolutely vital for plant crunching. It moves around food and a whole range of other signaling molecules.
01:15:03
Speaker
all around the plant body and yet as a tissue we don't know very much about its evolution at all. We don't know when it evolved, we don't know how it's changed through time and therefore we can't really predict how it might change in the future. And so for me this is a tissue which holds a lot of promise and again from this kind of interdisciplinary approach where we can combine together the fossils, the living species and you know to try and investigate the genes as well. So this is what
01:15:31
Speaker
The main body of my lab are working at the moment. We're trying to understand, we're trying to pin down when did the phloem evolve? Has it changed through time? You know, if we take a group of plants like the ferns that have this long evolutionary history, does the phloem look the same in all ferns or has it varied? And how, if we notice changes, do those changes correlate with any big functional changes?
01:15:53
Speaker
And so this is what we're really going for at the moment. And yeah, really exciting. We're about coming towards three years onto this kind of project. So we're just beginning to get the first really bits of exciting new data. So watch this space. Oh, indeed. And is it another place where we might hope to find some things which give us clues about the future directory of evolutionary development? Do we think the flow changes with atmospheric composition, for instance?
01:16:23
Speaker
Yeah, exactly. So this is actually a question which is one of the reasons, again, I really wanted to work on this topic because we don't actually have a really great understanding of this. Intuitively, you think if you're fixing more carbons, more photosynthesis, producing more sugars, maybe you're growing faster, then that likely means you're transporting a lot more sugar.
01:16:43
Speaker
But whether that definitely correlates with a change in flow and structure is still not properly known. And on top of that, there's kind of two ways you could change your flow and structure. These are tube-like cells. So one option is you just produce a load more of them, or you produce bigger ones, or you produce cells that look similar but have bigger connecting pores between them. And so these are kind of all different options which plants could use.
01:17:10
Speaker
and may be really important for changing the future. And again, I think hopefully setting out a more evolutionary framework for which groups have decided to modify which parts of the flow structure in general will hopefully be really, really informative for trying to understand a bit more about sugar transport for the future.
01:17:29
Speaker
seems that whatever you discover is going to be interesting because if we if we find that there's been very little change then that might again point to towards some of the importance of the kind of morphological thinking so just thinking about chemical gradients and to throw in another term reaction diffusion things that actually Turing was very interested in that
01:17:52
Speaker
just mean that there's quite simple ways of structuring things which where evolution is almost to one side and it's just this is you know physically this is this is easy to make and maybe that's you know if we'd find that phlegm hasn't changed well maybe that that would be a kind of likely candidate for that and again point the importance of those kind of ways of thinking and if it has changed a lot well you know it could
01:18:17
Speaker
very well give insights into how it's going to develop in future and more clues as to, you know, what kind of evolutionary pressures were driving things. Yeah, we're really, really excited to see what kind of results we get out and also to look at, you know, to investigate the genetic toolkit to see whether genes that we know are, you know, important in flowering plants, whether they are also really highly conserved or whether it's very, very disparate as well.
01:18:43
Speaker
But yeah, really, really interesting in these, you know, these long evolutionary questions about how much form is changing and which, you know, why some parts are incredibly conserved, whereas other ones are incredibly diverse. And I think this is, yeah, light roots and like, unlike firetatsy. I think these are the kind of questions I'm drawn to with these different structures and plants. Yeah. Kind of final thought from me, and then I'd love to get some final ones for you. It just does amaze me how
01:19:13
Speaker
even if the exact kind of structures and of roots and branching have changed, it seems such a common form within nature, above and below ground and within our bodies as well in terms of space filling networks of veins and arteries and so forth. It seems like there's something, again,
01:19:40
Speaker
very special about that way of filling space, something very effective. There's a wonderful book called Scale by Geoffrey West which talks about these things and he was looking at more the metabolic systems with animals and trying to explain
01:20:03
Speaker
why metabolism follows a particular scaling laws and he traced it back to the ways that you distribute energy through organisms which is by these networks. But then he started to look at cities and things like that and he found lots more instances of these branching structures in terms of roads. So yeah, an endless source of fascination to me. But yeah, what
01:20:30
Speaker
Yeah, any closing thoughts, questions, comments, mic drop? No, definitely. I think just on the last point you're making there, I think plants are actually really, really nice systems for thinking about scaling because getting them able to transport their water nutrients through this vascular tissue that you can quite prominently see. And you can follow this from the trunk
01:20:53
Speaker
chunk of a tree to the tiny little vein endings at the end of leaves and things. So I do think plants are a really brilliant system for investigating these kind of questions. I think plants seem to have been real innovators in that space because they're governed overall, especially by capturing light and not wanting to waste too much water. And then on
01:21:13
Speaker
with that as kind of board constraint they've still been able to form a remarkable diversity of shapes and sizes and so I think it's really interesting. I think plants are a great model system for that. I look forward to following along with the next discoveries that you make. You seem to have produced some really wonderful insights so far. Sandy Harrington, thank you so much for joining me. This has been a
01:21:42
Speaker
huge voyage of discovery for me and a great way of time traveling as well. Well thank you so much for having me on the podcast.
01:22:13
Speaker
you