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07 Grace Fleming: The enigma of seeds
114 Plays7 months ago
Plant biologist Dr Grace Fleming dissects the secret life of seeds. In a conversation covering everything from seed vaults to space seed trials, she examines the mechanisms of seed dormancy and how seeds sense and interact with their environment.
Bio:
Dr Grace Fleming is an Assistant Professor in Plant Biology at Michigan State University in East Lansing. Her work examines the physiological underpinning of seed dormancy and responses to varying environmental conditions, with a high priority placed on identifying and validating genetic and physiological factors contributing to seed longevity in the soil seed bank. Her research on the underlying mechanisms of seed death, viability and germination has applications in diverse areas including crop cultivation, weed management, and gene bank storage.
This conversation is hosted and produced by Catherine Polcz with music by Carl Didur.
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Transcript
Introduction to 'Plant Kingdom'
00:00:08
Speaker
I'm Katherine Poults, and this is Plant Kingdom. I'm recording in beautiful Sydney on the lands of the Gadigal people of the Eora nation, and I pay respect to their elders past, present, and future.
Podcast Themes and Guests
00:00:21
Speaker
Plant Kingdom is a conversation series about plants, nature, and environment featuring scientists, artists, researchers, and writers. We release two conversations each month and hear from people who have an intimacy with plants and nature.
Dr. Grace Fleming on Seed Dormancy
00:00:35
Speaker
Today's conversation is with Dr. Grace Fleming.
00:00:39
Speaker
She takes us into the secret life of seeds and we talk everything from seed dormancy to seed vaults and examine how they do exactly what they do. I'll now introduce Grace. Dr. Grace Fleming is an assistant professor in plant biology at Michigan State University in East Lansing. She is interested in the physiological underpinning of seed dormancy, a totally perplexing and fascinating field. Here's our conversation.
The Nature and Complexity of Seeds
00:01:16
Speaker
Thank you so much for chatting with me today. I'm really excited to talk about
00:01:22
Speaker
seeds, and it's been really interesting to prepare for this conversation. I think for me and probably for a lot of people, you think you understand what a seed is and what it does, but you've never really thought about it. It's another example of something that we see every day and haven't really stopped to marvel at. Yeah, it's easy to take seeds for granted, so really excited to jump in. But I did want to start with just some really basic questions about seeds, and I guess the simplest one is
00:01:52
Speaker
What even is a seed? There's a lot. There's a lot of ways you can think about seeds. One is just, it's like a, a propaganda. We call them. It's a way to distribute the babies the next generation. They.
00:02:14
Speaker
can travel. They are food for the baby plants inside them, but also for all kinds of animals and insects and even sometimes other plants, fungi. For me as a scientist, I think about the most as future plants, but I have been pushing against that a little bit because I think they also have their own identity as a seed. Yeah, interesting. Well,
00:02:44
Speaker
Yeah, because they're not yet a plant. Right. They're ready. They're potential. They're potential. But at the same time, they are something. They're a seed.
Are Seeds Alive?
00:02:56
Speaker
Yeah. And are seeds alive? I hate this question. So.
00:03:08
Speaker
There are some seeds that are definitely alive because they start to germinate basically as soon as they're mature. There's no pause in the lifespan of the plant. The plant grows, it flowers, it makes a seed. The seed immediately germinates and the next generation is up and running without any time in between.
00:03:31
Speaker
Then there's other seeds where they do, they have this lifetime of being a seed before they germinate. And while it's a seed, it's really hard to tell because one of the big ways we define something as being alive is that it responds to its environment.
00:03:50
Speaker
It's able to perceive things and respond to inputs. And for the most part, seeds don't really seem to do that. They're hard. They don't change. That's kind of the whole point, is that they don't change until all of a sudden they're allowed to change. So that lack of change makes it a little hard to say, yes, they're alive.
00:04:13
Speaker
If you go to germinate them, then it's really easy. You're like, aha, yes. That seed was alive, but I don't have a seed anymore. I have a plant now. I guess, I mean, I wrote that question and asked it to you, but it really is just us putting our human values on plants again. I spoke with someone earlier who works on dinoflagellates and they, I don't know, germinate is not the right word, but
00:04:44
Speaker
came alive from their dormant cyst state after 200 years in the bottom of a lake bed and there's a lot of creatures that have different forms in their life cycle and some of that is waiting.
Seed Evolution and Survival Mechanisms
00:05:01
Speaker
Yeah. And so there's colleagues I'm working pretty closely with who study other things that, like the dinoflagellates, they have this pause. So like tardigrades are, the water bears are very charismatic and can dry out and just hang out in this dry state for a long time. And they revive and then for the most part, go back to what they were doing. But the seeds just, it's a transformative experience.
00:05:31
Speaker
Yeah, it's not just waking up again. It's something different. And what did the plants, there's earlier plants that don't have seeds that reproduce by spores that are kind of more ancient lineages, seeds evolved something like 365 million years ago-ish. What did, what's the evolution of seeds enable plants to do? Like plants really proliferated after seeds and flowers evolved.
00:05:59
Speaker
Yeah, that's a great research area all on its own, so I'm not going to do it full justice, but I can address it to some extent. What I love about it, the thing that draws my attention to seeds, is that there is, like we were just talking about, there's this pause between generations. So that pause, I think, is really valuable because
00:06:25
Speaker
it means the plants can hide from an adverse environment. If the environment has changed and it's not favorable for the plant anymore, the seed might be able to withstand it. And then when the conditions go back to being favorable for the plant, the seed can then become the plant. So
00:06:52
Speaker
It sounds like very drastic, but really what I'm describing is like winter time. Oh, yeah. That's actually, yeah, it's such a clear way to think about it.
00:07:04
Speaker
Yeah, so that's just one and it's such an important thing for plants because they are tied to a place. You could divide things like animals are stuck to their time. They can't like go into stasis and then come out and be in a different time.
00:07:22
Speaker
But they can move around and get from place to place. And plants have a limited capacity for movement on their own, but seeds are really where it's at in terms of running a new space or waiting out this bad time. Yeah, they can move through time more so than space.
00:07:45
Speaker
But then the seeds also let them move through space because they get eaten and carried around and just spread all over the place. And that part of seeds is also wildly successful.
00:07:59
Speaker
Definitely. And that's something we'll come back to in a second too.
Environmental Cues and Germination
00:08:06
Speaker
I know this is a big part of I think what you study and your research interests are, but how does the seed monitor its environment or is it actively or perceiving and receiving information when it's a seed?
00:08:24
Speaker
So this is, I just did a deep dive into this question like a couple days ago. I've been looking over a lot of literature about, or it happens to be related to this. So there are a lot of ways that the seed perceives its environment. And there are some ways that it can interact with its environment more directly. And there's just
00:08:48
Speaker
more sensors, more types of sensors than I had dreamed of. And it almost feels like an elaborate series of like a trap. Like, you know, if you put a hair across the door jam and then the hair is missing and so you can say, aha, someone opened the door. Kind of like that, like the seats have like that one and then they have another thing where like a piece of paper falls and then if you go further and like the fan has been turned out, like all of these different things have to happen in the right order to
00:09:18
Speaker
let germination happen sometimes. Yeah, for them to be like, it is spring. Right. Yes. No, they're very cautious a lot of time. I mean, there's others that are like, let's go. Yeah, that's their strategy. Yeah. So one that I found was just, it surprised me is that the seed coat is this dry layer that surrounds the seed. It's on the outside.
00:09:47
Speaker
And the seed coat is material that's made by the mother plant. So it's only like 50% genetically related to the seed. So that on its own is like, that's a pretty cool situation. And then the seed coat is most of the time completely dead. Like those cells have done whatever job they had and the mature seed has this dry
00:10:12
Speaker
seed coat surrounding it, that if you add water, those cells are not going to do anything. They're dead. But the outer layer of the seed is not dead and can sense pressure between the inside of the seed and where the seed coat is. So the degree of pressure that that outer layer feels as like
00:10:35
Speaker
the seed is taking up water and the seed coat maybe is or is not stretching depending on what kind of seed coat it is. Like that pressure is something that will kick off a germination response or not. Pressure is a big deal for plants. So like it kind of makes sense overall, but just thinking about how all these plant cells are able to tell the pressure that it's like, oh my gosh. And is it something that
00:11:04
Speaker
science really understands how the seeds are doing that, or is that really like we're trying to understand those pathways? I feel like it is following a path a lot of inquiries and science take, where we can explain this mechanical
00:11:33
Speaker
observation and we have the tools to measure it and to some extent like just detecting changes in pressure in this intro space between the zed and the zed code like that's a little bit of a technical challenge but
00:11:48
Speaker
We can do that. But then as far as how it's actually happening is, that's a very hard question to ask. So there's some molecular stories of, oh, this protein gets squashed, or this gene gets turned on somehow. But yeah, that level of explanation of the cellular mechanics is under development.
00:12:18
Speaker
Yeah, it's so interesting. And again, it's a totally different system to us, right?
Internal Synchronization of Seeds
00:12:27
Speaker
We have nerves and know how decisions are made in our bodies and plants. It's a whole different system. Yeah, the change that leads to germination
00:12:41
Speaker
This is, the whole seed gets, all of the individual cells in the seed get synced up in a way so that germination can be this synchronized process. And it's very rare in a plant's life that that, like the whole entire plant is in sync because it doesn't need to be. The roots are doing their root thing and the leaves are doing their leaf thing and it doesn't really matter.
00:13:09
Speaker
Yeah, it's kind of like centrally coordinated, somehow fascinating. There's another cool example of the seed and the environment interacting
00:13:22
Speaker
which I just love, which is these seeds. I think it's a common name is stork spill. That's a kind of geranium. And they make a very pointed capsule. And then the seed has long ons, which are just like almost very thin and narrow ribbons that extend off of the seed. So it'll have two ons and the ons
00:13:48
Speaker
have a coil to them, almost like curly hair. It's just again, it's like this mechanical property of this material.
00:13:59
Speaker
And in, or I'm going to get this backwards, but it doesn't matter, there will
Innovations Inspired by Seeds
00:14:06
Speaker
be in a wet or like a humid environment, if the air is damp because rain is coming, the ons will be coiled up tightly together. And then it dries out and then they uncoil. And this repeated coiling and uncoiling acts like a screw
00:14:22
Speaker
So this seed drills itself into the soil. It plants itself. And scientists have taken this design and improved on it to make what they call a seed drilling robot.
00:14:36
Speaker
But it's not electric. It doesn't have any power source. It's powered by the same idea of the water level changes how tightly coiled the awns are. And so you can put seeds of whatever type inside this seed drilling robot, and then it gets drilled into the soil all by itself. So cool. Amazing, right?
00:15:05
Speaker
hundreds and millions of examples of solutions like this. Exactly. Yeah, this is like one species of, you know, bajillion. I don't even know how many, we'll just say big numbers. And I guess we've covered this a little bit when you were talking about dispersal too, I guess. What are the kinds of conditions that
00:15:29
Speaker
cause a seed to germinate? Is it really specific to how that plant lives and
00:15:37
Speaker
Yeah, so different species, they will have their own things that they want to have happen. But in general, it's something that lets the seed know that the seedling is going to emerge into an environment that it can handle. So for example, a lot of plants that
00:16:03
Speaker
are annuals so they make seeds and then they die and then those seeds germinate the next year and make seeds and die like that's that's all they got is their one year of being a plant. The seeds are shed at some point in the summer maybe later in fall and if they germinated right then
00:16:21
Speaker
that plant might not be able to handle the winter. So those plants often require a chilling period or there's different names for this cold treatment of the seeds, but essentially the seed needs to know it's gone through one winter
00:16:37
Speaker
and then it starts getting warmer and then that's the signal that it's safe, the annual is able to like go for it. Or if it's something that grows in a really fire-prone area or it's something that is maybe part of the first wave of plants in a successional series where
00:17:01
Speaker
start out with like a bunch of annuals and then build up to having some bushes and maybe some trees and then you get a forest. Then there might be like a forest fire or lightning storm and a whole bunch of trees get cleared just from the middle of the forest and all those annuals that started out they still have seeds around and they're getting all of a sudden more light
00:17:24
Speaker
than they ever had before because these tall trees that made the shady forest floor are just gone. And so they're like, aha, it's my time.
00:17:35
Speaker
Yeah, yeah. Go, go, go. Yeah. And the ways, again, just like the ways that seeds can sense what's in the environment, the ways that seeds detect if the seedling is going to be all right, they're so sophisticated. They have, it's hard to generalize like what it might be, but it's usually some combination of temperature and light and water and then maybe a couple extra things. Yeah.
00:18:04
Speaker
Some of the fire-adapted species in Australia, for some of them, it's the fire and the heat. For some, it's even just one of the chemicals in the smoke after two. It's just
00:18:19
Speaker
Yeah. And then two, like you can have the chemicals from the smoke and that's good, but then you also need to have a rain because otherwise like everything's still too dry. And there are some species where if the smoke and then the water are not, if they don't happen close enough in time,
00:18:42
Speaker
then the seed will just be like, nah, wait, I'll try again later. Yeah. Yeah. And they get one shot, don't they? And another big question for you.
Grace Fleming's Career Journey
00:18:55
Speaker
How did, how did seeds come into your life? How did you come to study seeds? Well, it was really a lot of luck.
00:19:08
Speaker
And I wouldn't change it for anything. I love seeds very, very much, but I was studying cell wall biology, like molecular structure of cell walls from the perspective of engineering them to be easier to break down and turn into biofuels. So that was what I worked on for my PhD, which is pretty far away from seeds.
00:19:38
Speaker
But then when I graduated, it happened that the National Laboratory for Germplasm Resource Preservation, NLGRP, which is on the campus of Colorado State University, they were hiring for a post-acposition. And so it just, like, it worked out. And once I started working with CSF, like, I am never looking back. This is the best.
00:20:09
Speaker
Yeah, there'll be lots to keep you busy with your whole career. Yeah. And what is the kind of big picture of your research interests on seeds? I've had a chance to
00:20:26
Speaker
say some of these ideas already, but I'm really interested in what seeds do. What are seeds as themselves? Not a future plant. What is the seed? And so I think a lot about how time affects seeds, partly because I did this research at the NLGRP, which I think we're going to talk about it a little bit.
00:20:57
Speaker
just they store seeds for a long time and see what happens. And I find that very interesting that we can sort of, because they have this pause, we can probe the effects of time. It becomes an experimental variable, which is not ordinary. And then now that I'm
00:21:22
Speaker
I've started my own lab. I'm interested in not just how seeds handle being stored for a long time, like in a lab, but what happens when they're in more natural conditions like just out in nature. They do just fine, a lot of them all on their own. And so how does that work? Because those conditions are very,
00:21:45
Speaker
very different from being stored in a super cold freezer and never being touched or moved. They're just very still. Right now, the way I'm getting into it is thinking about seeds taking up water, but they can also become dry again. They can take up water for a certain period of time,
00:22:12
Speaker
For some, they can even like just start to germinate. So maybe their seed coat gets a little crack and the tiny little root maybe starts to poke out. And even then, depending on the species, they can be dried back down to like five, 10% moisture and they're not dead.
00:22:34
Speaker
A year later, six months later, five years later, they can be rehydrated and turn into a plant. And if you're in the soil, there's a lot of water around from time to time. And sometimes there's not a lot of water around. So just experiencing changes in the water in their environment.
00:22:58
Speaker
that I think they must have some very good strategies around that, but they're not very well explored yet. Or I haven't found the answers if they are out there already. Are there particular species or kind of model organisms that you work with? I guess in some projects, it's quite diverse and
00:23:22
Speaker
Yeah, my favorite seed, and I came to love it during my postdoc, is soybean. And it was just very, very nice.
00:23:37
Speaker
It's quite large as far as seeds go. It has this nice seed coat that's easy to remove. They don't usually have dormancy, which is where you try to germinate them and they say, nope, you didn't give me like the special blankets. I'm not going to germinate.
00:23:55
Speaker
But we also work with Arabidopsis, which is just the model plant. It has infinitesimally small seeds, but we know a lot about its genetics, so it can be very useful.
00:24:10
Speaker
I think Arabidopsis is so interesting in how model organisms come to be. Do you know how, why Arabidopsis is so well studied or it's just, it started, people started working on it and then that was the basis for future work. How, why Arabidopsis? There was a long time.
00:24:31
Speaker
when pea, like peasum sativum, that was a big favorite. You might remember, you know, Gregor Mendel, he did all these experiments with peas. That really set a good foundation for a bunch of work in peas as a model plant system. But then, and this is like more like a legend than
00:24:53
Speaker
true accounting of what happened. It's fun to tell a good story rather than stick to the dry facts. So basically, a scientist or maybe a small cohort of scientists decided that pee was insufficient as a model species and basically just decided Arabidopsis was it.
00:25:14
Speaker
It was their, like, lab's favorite pet plant. Like, I might have said, oh no, it should be soybean. They're like, uh, I think Arabidopsis is good. And there are a bunch of things about Arabidopsis that are convenient. It can take just a month to go from seed to seed.
00:25:33
Speaker
So you plant a seed and a month later you're collecting mature seeds off of plants. Like that is pretty darn fast for plant experiments. It's the fruit fly of plants. Yeah. Exactly. And it's small growing. So you can put a lot of them in a small space. It's pretty tolerant of crummy environmental conditions. It doesn't need a lot of
00:26:00
Speaker
fancy stuff to be happy, and its genome is pretty small. So it was one of the first genomes that was sequenced, and that was published in 2000. And part of that is just because there was less material that had to be sequenced. Yeah, so that's the basis. And can you just describe what it looks like?
00:26:27
Speaker
So it is in, it's a brassicaceae. So this is the family that has broccoli and cauliflower and brassica. Mustard family in the common name. Yeah. Mustards. Yep. So it's got
00:26:53
Speaker
what's called a rosette farm. So it makes a whorl of leaves that all lie flat against the ground. And they're green and like moderately pokey around the edges like a dandelion or a
00:27:13
Speaker
prickly lettuce. And then when it's ready to start flowering, it makes an inflorescence, which is the tall stalk that sticks straight up from the rosette. And the rosette will get to be about like four inches diameter. And then the inflorescence will come up and be maybe like six inches tall. That can vary a little bit.
00:27:34
Speaker
And it will make tiny, teeny, teeny, tiny white flowers that continue to open up until it decides like it's done. And then the seed pods are so leaks. So they're very long and narrow and they get dry and brown, kind of like a pea pod, except much tinier. And then they're full of these teeny, tiny brown seeds. They're quite oily.
00:28:04
Speaker
They're bigger than a poppy seed, smaller than a sesame seed.
Beale's Seed Longevity Experiment
00:28:10
Speaker
And a significant project that you've been working on is known as the Beal Experiments. Can you tell me about this and how long this experiment's been going on for?
00:28:27
Speaker
So we're working with all of those seeds, too. The bottles that he buried had 20 different species, at least, in each of them.
00:28:38
Speaker
For each species, he put 50 seeds. So one bottle had a thousand seeds, and he made 20 bottles. And these are glass, like pint bottles, like a flask almost. Skinny, long neck, very small opening.
00:28:59
Speaker
and the seeds were mixed with sand and then stuffed in the bottles and then buried on campus here in East Lansing with the end of the bottle, like the neck part of the bottle, open. So the sand went all the way up to the neck and then there was no covering put over it. And they were buried upside down, so the neck's pointing down.
00:29:26
Speaker
just here on campus in 1879. Wow. So 145 years ago. And they were buried by who is Beale? He was a plant biologist. He liked seeds a lot. He did a lot of work with seeds. But he also just thought plants were cool. We have a garden that he designed, which showcases
00:29:53
Speaker
plants from different classes, so I think it's arranged sort of by evolutionary group. But he also like planted an experimental grove of trees on campus and he communicated with Darwin about corn breeding and he was involved in the development of the
00:30:15
Speaker
United States Department of Agriculture and it was a heady time for being a plant scientist because he got to advocate for the plants that we were using for agriculture
00:30:30
Speaker
being considered as worthy of scientific study just as much as anybody else's plants. And that had a big impact. Without that advocacy and seeing that we could be scientific about planting and fertilizing and row spacing and all this stuff, then agronomy wouldn't exist probably. It was a big deal to get it all taken seriously. Yeah.
00:30:56
Speaker
And when he buried the bottles, was it a seed longevity experiment from the beginning? What was he wanting to know? Yeah, it was. We don't really know how long seeds can last when they're in the soil. So let's try it out. He was an old man.
00:31:25
Speaker
when he started this experiment. And at the time, he planned for a bottle to be unearthed every five years. So with 20 bottles, that would be a 100 year experiment. So even when he started it, he knew that this was going to have to outlive him. Yeah, wow. And in 2021,
00:31:52
Speaker
Was it bottle 16 was dug up in the middle of the night? Yes. So there are four bottles left. Four bottles left. And what did you discover? Were any of the seeds viable? It was so cool.
00:32:18
Speaker
So I got to take the bottle after we dug it up and search around in the sand to try and see if I could pull out any seeds before we tried to germinate them. And just getting to like mess with this sand and know the last person who was handling it was
00:32:40
Speaker
this guy, Beal, like I know all these papers, I see his name everywhere. That was just, I was surprised by how powerful that felt. It's a museum a bit like it's a, yeah. Connects you to that time. Yeah. When we took the bottle, there should have been like 1000 seeds in there. There, they were 141 years old when we dug them up. And
00:33:08
Speaker
20 of them germinated and grew into normal plants that made flowers and made seeds and seemed unaware that any time had passed. Incredible. It must have been very exciting to see them start growing.
00:33:33
Speaker
Yeah, it took, I want to say seven days before the first one showed up truly as the whole time had passed. It's like, oh, water? Light? Let's get this going. Seven days later. That part was also surreal that they were just so vigorous.
00:33:52
Speaker
Wow. And was it just one species? What grew? It was basically one species. So it's called verbascum blotaria. And the common name is mothmalane. And the reason I said it was kind of one species is there's that what Beale wrote down
00:34:17
Speaker
that he put in the bottle was seeds of a different plant. It was the same genus for Bascom, but he said it was the species Thepsis, which is common mullein, and these plants don't look like anything alike. The flowers kind of look alike. The seeds look very similar, but the leaves and the way the flowers grow on the inflorescence, very, very different.
00:34:43
Speaker
So it's like, well, there's some kind of mistake. I don't know who made it or how, but we can all, all scientists can relate to that experience. And then, so of the 20 plants that germinated, there was one
00:34:58
Speaker
that just looked a little funny. And as it continued to grow and mature, it was clearly funny looking. And it had features of verbascum thapsis as well as verbascum bladderia. And so we thought it could be a hybrid. That's certainly possible. So we did genotyping using some DNA and confirmed that, yeah, it had
00:35:29
Speaker
Blateria DNA and Thapsis DNA in the same plant, so it was a hybrid between those two parents. Which is just, yeah, how did that happen? All of the species that Beale had in his bottles were weedy species at the time. Those species are all still around today.
00:35:52
Speaker
pretty much exactly as they were in veal's time. And they're still kind of weedy. And I'm not quite sure what to make of it, but I do think there's something there. Like the weediness is an important thing too. Yeah, respect to the weedy, what we can learn from the weedy species, not just see them as pests or, yeah. They've got tricks. We can figure them out.
00:36:20
Speaker
could be really useful. Yeah. They're good at what they do. That's why they're weedy, right? Yeah. Exactly. Yeah. They're the best plants. Hmm. Yeah, hybrids are so interesting. It's just another example too. And we have these kind of clear, you know,
00:36:37
Speaker
definitions of species concepts and ways that we would like to categorize things, but there's a lot of different hybrids in nature, and they do a lot of interesting things. And I don't know Vrvascum Blutter, I know Vrvascum Thapsus, and just to describe what this plant looks like, is it kind of
00:36:56
Speaker
similar in form? Yeah, yeah. So for Bascom Blatteria has very dark green. Again, like dandelion style leaves. It also grows as a rosette like Arabidopsis. But its rosette will get to be more like 12 inches across or maybe even a little bigger. Awesome.
00:37:21
Speaker
They're big plants. Yeah. Yeah. They're, they're big. And then it's different from Thapsus because Thapsus has hairy leaves and Doria has these very shiny leaves. So that's like very obvious, but both of them are biennials, which means that the plant will germinate or the seed will germinate and grow for a season. And then the whole plant goes through a winter.
00:37:46
Speaker
And without that winter period, the plant won't flower. So it doesn't flower until it's second year. And then after it's done flowering and making seeds, then the plant is done. And the seeds are made in these pretty small capsules, but each capsule holds like hundreds of these very tiny seeds. And the seeds require light in order to germinate.
00:38:14
Speaker
And so when you have like there's this giant rosette covering all of this earth and then you have this tall inflorescence with these capsules that kind of open when they're all dry and the seeds can sort of rattle around and get thrown out of there. They might all land next to each other and then one would germinate and grow and make this rosette that covers all of its like sister seeds from that same parent plant.
00:38:39
Speaker
And until that rosette goes away, those seeds aren't going to be able to germinate because of this requirement for light. So I think that has something to do with like how they're able to last so long is just that the plant itself kind of shades out its own seeds.
00:38:56
Speaker
So if things might last at least a little while, then it wouldn't necessarily be very successful. A lot of times if something can last a little while by some like accident, that means they've actually latched onto lasting a very long while.
00:39:12
Speaker
but like we're still like at the very beginning of working those details out. But it makes these beautiful flowers. They're like really good cottage flowers because it's this tall spike. It kind of has a hollyhock almost look to it and they can be bright yellow or white or deep
00:39:31
Speaker
purple in the center of the flower where the pollen is. The stamen have fur sticking out of the side. And for Bliteria, at least, it's like hot pink, like magenta pink. It's very striking. So they're very cute. Yeah, amazing. And Hardy, yeah, it's interesting that it's so long lived. And then the next bottle, when's the next bottle being excavated?
00:39:59
Speaker
The plan is for that to be done in 2040. Yeah, wow. And in nature, seeds are stored in situ, right? Not in glass bottles or in freezers.
Dynamic Seed Bank Ecosystems
00:40:15
Speaker
What is the soil seed bank? How many seeds are in the soil? How long do they hang out there? Oh my gosh, it can be
00:40:27
Speaker
It can be humongous, and it varies also depending on how deep you go.
00:40:34
Speaker
So it's very dynamic. Seeds are shed and just fall down, and seeds are blown in, and they're pooped out by birds, and they fall off of dogs' fur, and they float down the river. They just wind their way to someplace in the soil, and then there's rain and snow and freezing, so the soil moves around. And then there's insects, like ants are tremendous movers around of seeds.
00:41:04
Speaker
So it's not very static. Things get around a lot. So it's tempting, for example, to think the deeper it is in the soil, the older it must be. And the soil, that's probably true. But the seed can just get stuck down there by all kinds of agents. But this is a fact that I just wrote down the other day. There's a forest in Germany.
00:41:31
Speaker
A temperate broadleaf forest. It has the record for soiled seed bank density. They counted over 500,000 seeds per square meter. Per square meter. What? 500,000 seeds. Incredible.
00:41:57
Speaker
And the seeds also represent kind of multiple generations too, don't they? Yes. Yes. There's some like they'll be
00:42:10
Speaker
deposited and then germinate the next spring. And then there's others that, yeah, they'll stick around. They'll work their way deeper in the soil. Eventually something might bring them up closer to the surface. That's something I think about a lot with these furbascum seeds that were 141 years old. There might be a plant growing in my yard that came from an equally ancient seed.
00:42:35
Speaker
I just don't know how you would tell from looking at it. I don't think you can, but yeah, just because it grew this year doesn't mean that the seed fell last summer, like no way. So interesting.
Genetic Diversity in Germplasm Storage
00:42:50
Speaker
And okay, now a different kind of seed bank, one that you mentioned already, the U.S. national plant germplasm system. What's the acronym?
00:43:04
Speaker
Oh, the, I think you're right that overall, like that's the big umbrella. And where I was specifically was the national laboratory for genetic resource preservation and LDRP. Okay. And they preserve germplasm of all different kinds of life forms with
00:43:29
Speaker
had a genetic material relevant to agriculture? Is that right? What did they do there?
00:43:37
Speaker
Yeah, they store, so there's a whole wing of the building that's about animal germplasm. So that's one thing that gets stored. There's some like bacterial and fungal collection that's happening now. And then there's also plants. So there's, yeah, there's a lot of space devoted to crops and just different lines of crops, like different varieties you would get at the store or order from a catalog.
00:44:07
Speaker
But then because it's about genetic resources, anything that's like slightly related to crop genetic diversity is also stored. So there's like crop wild relatives are a very big deal, which are things like they've taken collecting trips to Kyrgyzstan, which is where Apple
00:44:30
Speaker
originated, apple trees. And they could get, I don't know if they actually brought samples back from there, but I know they like did some research on the genetics of those apples, or they've gone to Jordan and surrounding areas to find barley that's growing wild. And these are the relatives of the cultivated barley that we grow in the fields.
00:44:55
Speaker
And then aside from that, there's a lot of native species or wild species that get preserved too. Yeah, it's so interesting that not the trend, but the presence of seed banks in their history, like they were established as seed banks, places where you could go and get
00:45:18
Speaker
seeds to grow and store store seeds that had kind of economic purposes and it's kind of moving more into conservation or I guess expanding their their reach and the wild relatives as you were saying they're important for potential disease resistance and everything as well. What's the word just kind of preserving seeds against different socio-political relationships and intentions to write a lot of those
00:45:48
Speaker
agricultural species are from former Soviet Union areas and having a record or collection in America is kind of important to longevity. And as a, I don't know, as a, a bank is just the right word, isn't it?
00:46:09
Speaker
Yeah, and there's now gene banks all over the world and they cooperate with each other and so they will have backup collections from other institutes and
00:46:27
Speaker
It's a really big concern to have like, what's enough? When have you sampled enough and how long will it last and what happens if the freezers go down or a hurricane comes or, you know, there's so many disasters. So trying to fend them off as best we can by backing things up all over the place is a big part of it.
Philosophy and Scientific Inquiry
00:46:54
Speaker
Yeah. Yeah. Huge.
00:46:57
Speaker
Huge, huge. So you have an undergraduate degree also in philosophy, and I think it's a minor in history and philosophy of science and math, which is quite unique for a lot of scientists. Do you think having that background has given you a bit of a different understanding of even the study of science or the role of science or what scientific knowledge is?
00:47:26
Speaker
I mean, it seems like it. The way that my undergraduate degree went was that we spent time reading works by the original authors and discussing it. And so reading Newton, reading Aristotle, and just
00:47:54
Speaker
having a conversation about it, it helps make these ideas seem a little more approachable. They don't need to be interpreted by someone else necessarily for you to be able to understand it. But also just seeing how one idea leads to another. And it's really obvious that no one is just sitting there coming up with a great idea out of nowhere. It just doesn't happen.
00:48:22
Speaker
We spent a lot of time with Ptolemy, who made a whole astronomical system to explain the motion of the planets and the stars if the Earth was at the center of the universe.
00:48:36
Speaker
and it worked. It's false, but he made the math work. And then that led to Galileo's discovery or convincing statements about how, no, the sun was at the center of, well, something, solar system, universe, whatever. So it's just nice to feel
00:49:03
Speaker
like part of a big chain of people working to get some clarity about like, what is going on out there? I don't really know, but we got some ideas. Yeah, how knowledge is built upon and evolves too, right? And understanding some of these paradigms of science and of plants. I don't know if this is something that you studied. It's something that I remember
00:49:32
Speaker
It was really interesting to me because I think it reflects maybe not how scientists think about plants, but how society kind of treats plants still in Aristotle's hierarchy of souls. Is that something that you studied? I don't remember. I know we've got a bod of Aristotle. Maybe not.
00:50:00
Speaker
Yeah, I mean, it's just the the hierarchy that we we see that you know, there's, there's rocks and they kind of have this no soul. And then there's plants that have a nutritive
00:50:17
Speaker
So like they do some kind of work and then there's animals above plants. And then guess who's at the top? There's humans at the top, but just this, it's kind of this hierarchy of feeling and knowing and intellectualizing in a way. And plants were just there at the bottom. Whereas it's, you know, we know they do things differently, not lesser than, yes. Yeah.
00:50:44
Speaker
I mean, one thing I still think about from Aristotle is his idea of Antelicaia, which we had a translation that everyone in the school used, or it was translated as being at work, day-ing itself. So everything has, even the rocks, they have this property.
00:51:03
Speaker
Like this is how you maintain your existence from one moment to the next is that this property of being at work, staying itself. And so I do come back to that a lot in terms of like, what is that like for a seed? What does that consist of? What work are they doing? Like, yeah. And, and you,
00:51:26
Speaker
right on your bio. And of course, there's a lot of different potential applications of the seed longevity research. What, I guess, what are some of the different applications of this or how might this knowledge be used in the future in ways that we might not be anticipating right now?
00:51:47
Speaker
Yeah, I have a friend who's also a seed biologist, and she's just applied for a NASA program to live in a biodome in, I think, Arizona for a year. And one of her motivations is that she wants to get beans to Mars. We need to figure out a way to get these seeds
00:52:17
Speaker
to be productive for people to have a future outside of Earth. And there's been work already of sending seeds to the International Space Station and having them on the outside of the space station and then sending them back to Earth after one and a half, two years and seeing
00:52:35
Speaker
They survived. They grew. If they were just like out in space, less protection than any of the things on the inside. It's just so cool. But there's also the ability to become dry.
00:52:54
Speaker
and become wet and become dry again and wet again and still maintain themselves. I think if we can unravel a little bit more of the details of how that works, it will have tremendous applications for things like RNA-based vaccines.
00:53:13
Speaker
For example, because RNA is one of the things that is stored inside of seeds and is used by seeds when they're germinating. And so they're able to protect it without needing to keep it cold or have it in a solution of who knows what chemicals. They figured something out about that, but also
00:53:35
Speaker
other things, like they also have proteins and enzymes and fats that are all being protected. So just that has great potentials. Yeah, on the space seeds, there was in Australia, they sent seeds of the Walamai pine to space, which is, it has this really fascinating story. It's this, I think the family is RKCA. It's a really ancient
00:54:05
Speaker
plant that was just known in fossil records. And then in the 1990s, some mountaineers found a few living species in this hidden valley, like it's just one specific surviving population of this Gondwana plant that's like
00:54:23
Speaker
I don't know, I'm going to say 250 million years old, something, but they sent its seeds to space and they germinated. It's a survivor. Yeah. Fascinating. Just thinking about time in that valley. And yeah, there's a lot of research and pride around the Wala Mai here.
00:54:41
Speaker
Wow. Yeah.
Endless Fascination with Seeds
00:54:45
Speaker
So that's another thing. And I'm not sure like exactly how this would be applied, but we think a lot about DNA, like some of a genome is storing information. And so this ability to maintain that information for hundreds, thousands of years, basically uncorrupted.
00:55:08
Speaker
I think is also a very high value. Mm-hmm. Yep. Fascinating. And, oh, do you think we'll ever understand all of the marbles of seeds and what they're doing? Or do you think they're always going to keep some of their secrets? Oh, I don't think we'll ever figure them out
00:55:40
Speaker
they're just, plants are so different. They're so different. They defy our human pattern making powers. They're just unpredictable. And then we figure something out. It's like, Oh, that makes total sense. But then that doesn't make solving the next problem any easier that there's always like a twist to it. So I think they will
00:56:05
Speaker
tease us and beguile us and fascinate us pretty much forever, as long as we're both around. Seeds will be part of us and we'll be part of seeds. That was my conversation with Dr. Grace Fleming. Thank you for listening and huge thank you to Grace for sharing her work.
00:56:35
Speaker
Plant Kingdom is hosted and produced by me, Katherine Poults, and our music is by Carl Dider. Listen to us wherever you get your podcasts and consider subscribing, writing, and reviewing our show. For more, check out our website at plantkingdom.earth.
00:57:17
Speaker
you