Listener Questions #47 - Plant Questions (featuring Dr. Manuel Lerdau)

30:13So plants and copper are even more special, as you might imagine, because they're plants and so they're special. that copper is also used in plants in this really neat pathway. I'm going to jump into jargon for a moment again because it's the name. It's called the ascorbate pathway. And if you're into human nutrition, you know that ascorbate is vitamin C. And so plants have this very neat ascorbate pathway for dealing with very chemically reactive compounds that they make when they get stressed. So this ascorbate pathway is what keeps plants from self-poisoning. And it requires copper also. Huh.

31:02And so you need, plants need copper. Some of it goes into ascorbate and some of it goes into what we call electron transport, that part of respiration and photosynthesis. And the reason that plants have to sort of have this special problem, it all comes back to the fact that plants are stuck and can't move around. And for almost all plants, how do they get their food? They capture sunlight, and they use the energy that they capture from the sun to turn carbon dioxide into sugar. Now, the problem is, if you're a plant, you can't control how much sunlight you capture always. And sometimes there's more sunlight, and thus you're trapping more energy than you can use to turn carbon dioxide into sugar.

31:57Okay. And in that case, and we're getting really close to physics here, in that case, you have enough energy in there that you end up with singlet oxygen. Not O2, but O, which actually becomes O minus. And that is really poisonous. And you need a special detoxification pathway to take care of that odd oxygen. and that's why plants need that copper in that ascorbate pathway is to take care of all the oxygen. Now, we get this, you know, if you go into your health food yoga store, you'll read about antioxidants and buy foods that are antioxidant. Well, that's the same thing. We make low levels of oxygen, but it's not really such a problem for us.

32:51Plants are producing this all the time when the sun is bright. And they need a specialized chemical pathway for it. So they have things that are toxic to themselves too. So that sounded like a lot of fascinating chemistry. I didn't hear any physics in there. Well, you know, oxygen, O versus O2. Oh, I see. You don't get that without physics. Right, yeah. I guess physics is just perspective. So it's pizza night and I'm making my pizza with like 50 cloves of garlic on it. I always wonder when I do that, like, is there a limit to how much garlic you can put in your food? Can you poison yourself with garlic?

33:29Or am I free to just keep going to infinite garlic pizza? I'm an empiricist. I would say, let's do the experiment. I don't necessarily want to be part of the experiment, but I'll read about it. You'll be hard to replace as a co-host, Daniel. So the chemicals that make garlic taste good are the very same chemicals for most people. There are a few people who are unable to eat garlic. They react very badly to it. And there's sulfur-based compounds in the garlic. That's what gives it that strong flavor. And some people react very badly to that. Now, all of those compounds at high enough levels will cause problems.

34:16Remember I said that there are, and you used the phrase dose dependent earlier. All plants have chemicals in them that if you eat enough of them, you will not be able to digest it. And it will cause at the very minimum indigestion. My guess is that if you're able to eat garlic at all, you probably have some kind of dose dependency and at some point it would get too much and you would probably get sick to your stomach from it. The easiest example for people to know about is the fact that the chemicals in leaves that give them their toughness and structure, things called tannins and lignin. And all of these chemicals, what they do, tannins are the famous ones because tannins are what are in tea.

35:09And tannins are not exactly toxic to most organisms at reasonable levels. but they do inhibit the digestion of protein. So they make you a much less efficient eater. So imagine you're a bug eating a leaf. And as you eat the leaf, you want the protein in that leaf because your protein concentration is 10 to 50 times greater than the leaf. So you need to eat a lot of leaf to get your protein every day. You don't get it from milk or anything. So you're eating all that. That means you're eating all that tannin. That tannin actively interferes with your protein digestion. And so it's a trade-off. And of course, from the plant's perspective, the reason it doesn't just fill itself with toxins is that if it did that, well, then it wouldn't have chemicals for photosynthesis and for reproduction.

36:11So you always have to balance how much you defend yourself. Now, bugs are pretty smart, too. And what a lot of insects have figured out how to do is to have an early stage in digestion where they chemically modify the tannin before it interferes with protein digestion. So they've sort of worked around it. Humans don't have that workaround. So we could have our protein digestion very much inhibited by tannins. Okay, let's send that answer on over to Tan and see what they have to say. Hey, Team K, that was excellent. I learned a ton. The bit about alkaloid genes just sitting dormant in potatoes and tomatoes and is ready to switch back on.

37:02That kind of blew my mind. So I will never look at French fry the same way again. Hey, keep up the show. Make it last. I hope you guys never go away. Syndicate this thing if you can. Thanks again. Pan from Oklahoma City. Bye.

37:25Our town is small taters by most standards, right? But to the people who grew up here, it's everything. What happens when a quiet Tennessee town becomes the front line in a battle over the future of America? developers with right-wing ties have purchased hundreds of acres of land in the area the first thing you see when it pops up is pioneers in appalachia but they weren't just planting houses we need cities on a shining hill that exemplify and embody the christian way of life stop right there is that normal a podcast about what happens when a small town becomes the site of a social experiment.

38:01God need men to rule. Great. And decides to fight back. Do not use my hard work to sell your bull. They're not just opposing what's being planned for here. Our hometown is not a test tube. They feel like they're standing in opposition to an entire administration. Guess you didn't move in on a bunch of dumb hillbillies now, did you? Listen to Our Town on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Hey Portlandia fans. Carrie Brownstein and Fred Armisen here. You know us, or rather you know them. Tony and Candace, Nina and Lance, Spike, and yes, the chicken. We've played a lot of iconic characters over the years, but today we're showing up as ourselves to tell you about Podlandia, AO Rewatch, our brand new podcast.

38:47Each week we'll revisit an episode of Portlandia from the very beginning. Breaking down the sketches, exploring the backstories of our most iconic characters, revisiting the Portland locations you know and love, and opening up about our creative process. How did any of this get made? Why do we think that was a good idea? We're ready to talk about it. And we'll also be joined by the people who helped bring it all to life. Guest stars, collaborators, and friends, including director Jonathan Kreisel, the mayor himself, Kyle McLaughlin, legendary musician Amy Mann, and many more. Kyle is going for it here.

39:20You fully improvised, not just words, but a song, a melody. Well, I thought he was going to write, I thought you were all going to write a song. I remember you thinking that. Listen to Podlandia Ayo Rewatch on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Hey, this is Hayes Davenport. And Sean Clements. We host the podcast Hollywood Handbook. Every episode we're trying to help our guests improve their careers by mainly focusing on how they can help us improve our careers. The show is famously super accessible, so you can easily jump into any of our 650 episodes and understand what's going on.

39:55We recommend some of our recent episodes with Ben Stiller. The definition of what is a movie has kind of changed anyway, too, right? What do you think it is now? It's images and words being spoken, captured by some sort of technology. Danny McBride. He loves Boba. Oh, that's fantastic. And you make it on, you make your own. That's great. I call him Tarot Reed. it's a good name they're all named after cast members of american pie yeah i call i don't i never looked up if she was in this but i call him lychee sobieski yeah i don't think she was an american pie but i haven't looked it up haven't looked it up yeah she was prominent around the same time yeah then mary steenburgen why are you guys talking to me like i'm worried why are you so down to me that you think i don't understand your little play play game i just really i I'm trying to set you up for success here.

40:48Listen to Hollywood Handbook on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts. On Solita, we share the messy stories of traveling alone as a woman. Your Duolingo is not going to come back to you when a man is inside of you. Oh, no. I'm Julie Pinheiro, and I travel by myself because it's a rare space where I can say yes without asking anyone else first. I'm on a mission to reclaim the word solita, trading the pity for possibility. Every time I tried to be alone, I kept meeting people and they were like, you smiled at us. Not a lot of people smile around here. I can wait four hours for the next bus or this random dude is offering me a ride on his motorcycle.

41:34It's when you're alone that you're most receptive to the world as it is and not the lies you're sold about it. So whether you're a solo travel veteran or you're too nervous to book your first trip, I hope you listen to Solita on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.

42:04and we're back and the next question is jane from red car england and so daniel do you want to go ahead and get in your you love jane's accent i love jane's accent she's wonderful to listen to it's melodic and harmonious and it also just seems like she's having fun thinking about science. Nice to hear from you again, Jane. All right, so let's go ahead and hear Jane's question. Hi, Daniel, but mainly Kelly. It's Jane from Redcar, England again. Now, I know that I'm greedy, but I've got another question. What causes seeds to germinate? I know that some plants need fire to germinate, another needs several weeks below zero, Celsius, sorry, and moisture and light also affect germination, but that's not what I mean.

42:51If you sow several seeds in the same conditions, not all of them will germinate. So what is the spark that sets it off? I presume that it's some sort of chemical reaction rather than divine intervention, and once cell division starts, it is complex but understandable. But how does it start? Is it some random quantum process in which case Daniel should be answering after all. I'm still loving the show. You and Daniel, as well as being so intelligent and great science communicators, are just so much fun to listen to. Even when the jokes are painful and the poetry is more McGonagall than Keats, I always find myself smiling as I learn something new so I can't wait to hear what your answer will be.

43:44Thank you. Always lovely to hear from Jane. And so, Manuel, let's start from the beginning. What does germinating mean for those of us who weren't in intro biology for like 20 years or something? Well, I used to teach at SUNY Stony Brook, which is on Long Island, right outside of New York City. And we had a lot of students who were not native English speakers. And when I would get to germination in intro bio, one of the first points I'd have to make, I learned this only by not saying it one year, is it has nothing to do with becoming German. It's completely independent of that. Okay. So germination is a really interesting thing.

44:27And germination occurs when the plant in the seed form decides that instead of being in the form of a seed, it's going to be in the form of what we think of as a plant. Something with a stem, something with leaves, and something with roots, as sort of the stereotypical example. And that transformation, so it's genetically exactly the same, that transformation from seed to differentiate itself with leaves and stems and roots is germination. Okay, so like, you know, with humans, when it's time to go from being like, I don't know, a fetus to a baby, there's like a nine-month window. And when that nine-month window passes, you come out of the body.

45:19And there's, so it's like a very fixed time thing. But with seeds, is it like you wait three weeks until you go from being a seed to a plant? Or is there different cues for that? So I guess I'm kind of going to push back on your idea that you go from being a fetus to a human being. Okay. In a sense, when you're a mammal, as soon as fertilization occurs, you are developing. And you are initially just dividing, and then you're dividing and differentiating, and then all of a sudden, at some point, you're born. Okay. And it's not like you're only linked to some internal clock, right? but you're marinated in a bath of signals from the mom, right?

46:02And you're marinated in the signals. But if you're a bird or a reptile, you start as an egg. But as soon as you fertilized, you are developing. Now, in many animals that are born from eggs, the rate that you develop is temperature dependent. Okay. But you're always developing. Seeds are really, really different. A seed is a plant. It's not a developing organism along the way to a final adult form. It's an adult in itself. A seed is not a baby plant. A seed is a plant. A seed is an adult? That's mind-blowing. A seed can be thought of as an adult. Wow. Right? How so? A seed, there's fertilization occurs.

46:49And what happens after fertilization is that it becomes a seed. So in a plant democracy, seeds could vote? Well, the male seeds, yes. We don't let females go. Oh, whoa. Whoa. Well, remember we're in Virginia, right? Oh, why? You're raining down the bombs over here. I am retrospectively upset about the getting away from your mom comments, because now I'm seeing anti-female sentiment throughout all of this. No, no, no. Not at all. But it's an important distinction both in ecology and in evolutionary terms because that seed is something that in some species can survive for years, decades, centuries, even sometimes millennia.

47:35Amazing. And it is not that it is a plant frozen in development. It is itself what it is. Now, it's unique and different in that it's not drawing resources from the environment. It's not metabolically active. And so it challenges our idea of what it means to be, quote, alive. Oh, it's a little bit metabolically active, not very. The question, I'll rephrase your question, Kelly. The question is, what causes a seed to decide to go from being one form, the seed form, to being that differentiated, quote, plant form, the leafy form? And that's where things get interesting. Because for some plants, that decision is a chemical one, right?

48:28There are some seeds that need to, remember we talked about the seed going through the bird digestive tract or mammals, some mammals as well. That seed needs to pass through the physical and chemical scarification of its surface so that it can germinate. Other seeds need a certain period of low temperature before they can germinate. Still, other seeds need a combination of low temperature and water before they can germinate. Essentially, what it all can be explained by is that seeds are somehow able to use cues from their environment. It might be the intestinal tract of the bird or the spring rain in the desert as a cue to say, okay, this is a good time to go from being seed form to being leaf form.

49:28So that is what germination is. A little different than animal development. And so why would you need the cold spell? What does the cold spell tell you? Well, think if you're – we've got – we're in July now, and in Virginia and in California, you've got grasses now who are beginning to set seeds. And those seeds are going to see, at some point, rainfall. And if they say, oh, it's nice and rainy, let's germinate and grow. If they do that in October in Virginia, they're going to be seedlings when it starts to freeze. Bad idea. They don't want to do that. So they say, okay, I'm going to need some kind of a low temperature signal for long period, months, before I turn on my water sensitivity.

50:25And of course, this is one of the great things scientists are trying to figure out now who work on sea germination is what is that low temperature sensor that they're using that says, okay, two weeks of low temperature were not enough to make bee water sensitive, but four months are. And what genetically is happening in that? But to bring us a little bit back closer to Jane's original question, I think a common experience is you buy a bunch of seeds, you put them in the ground, you treat them all the same. They're in basically the same place. Some germinate, some don't. Some grow fast, some don't.

51:02Is that genetic variation among the seeds? Is that some sort of historical difference in the seeds before they came to you? Or is there some quantum mechanical randomness where they're sensitive to cosmic ray muons? So if you're buying your seeds, in Virginia we buy our seeds from Southern States Cooperative, you buy seeds who have received all the chemical and temperature treatment that that species of plant might need to be able to germinate when you put it in the ground and water it. So you put it in the ground, you water it, it is primed and ready to go. That's why you buy the seeds, is that you don't want to have to worry about letting them sit in your freezer or in your refrigerator over a winter.

51:48You buy them, you plant them, they grow. So this is something I didn't understand at all. You're saying seeds have a very complex set of germination requirements and highly variable. And when you buy seeds, all that work has been done for you except for the last step. Right. Put it in the ground and water it. Wow. And so this is another thing that we did when we domesticated plants. A lot of the seeds you buy are of domesticated plants where we have reduced the number of experiences the seed needs to have before it germinates. Most domesticated plants, we've selected them to be very fast germinators.

52:25Wow, domesticating plants seems like a lot of work. Well, you know, we've been at it for a long time. We started roughly 12 ,000 years ago. Exactly. All right, so you were saying that purchased seeds are primed to go. All right. Now, some of them don't. And that largely occurs for a couple of reasons. One, those seeds were improperly fertilized to begin with. And the seed developed, but it wasn't really viable. And there's nothing you could have done to make it work. sometimes those seeds were fine but maybe because they were so primed to go some of them sat for too long and they actually they were a little bit too active in the seed form before i corrected myself when i said they're not entirely inactive the seeds but they're largely inactive but if they're you know they could be a little too much in the seed and then they're not able to go and And some of it is you think you're doing it all right, but you don't always do it all right.

53:30But one of the things that happens is that when people who sell seeds learn that certain ones are not germinating well from their customers, they often start doing things differently to try to improve that germination rate. And that's why it is so high. Now, you can see this same sort of thing in wild plants. You can collect acorns and do what you need to do to the acorn so that it will germinate. And different species of oaks have different requirements. They won't all germinate. Usually, that's because they didn't all develop along the way properly. And is that genetic? Is that environmental?

54:13It's really hard to say. I would say it's internal, but it could be genetic. It could be environment. But it sounds like if you have seeds with the same genetics and you give them exactly the same experience, then you should get the same germination. Yes. There is no real randomness. No, this is one of the few cases where the physics, the muons are not that important. Although it underlies everything, of course. Absolutely everything. So do you have any stories for like the most complicated set of conditions that a plant has needed before it will germinate? Do you have like a favorite example of a plant being high maintenance?

54:54And is it sequoia trees? You know, maybe it's because I have and am still in the midst of raising up three high-maintenance offspring. But I think the really interesting stories involve the low-maintenance ones. And I think that these cases, there's a lovely study still going on. I think it's about 120 years old right now. It started about 120 years ago at Michigan State University, where they took seeds and put them in pots and buried them. Many, many, many, many, all identical. And they've been digging them up, I think it's every 10 years maybe, and germinating from these pots and seeing how germination rates change with time.

55:45And they're still getting incredible germination rates. And what's amazing in these studies is that they now have plants growing today who were adapted to the environment in East Lansing, Michigan, 120 years ago. And so they can actually study evolution by comparing these seeds from 120 years ago with seeds that come from individuals today. They can study how, what adaptations have occurred. And there have been similar kinds of works on people who find seeds. There was a guy who was actually not working on plants. He was working on ancient condors. You know, condors used to occur pretty far into the western United States.

56:38They weren't just on the coast. So he was studying condors, fossil condors, and ancient condors in pack rat middens in the Rocky Mountains. And he discovered seeds while he was looking for condor bones. And so they germinated some of these seeds. And these are seeds from thousands of years ago. So you can actually study adaptation in real time across centuries and millennia because of the ability of seeds to not germinate when the conditions aren't right. And the seeds from the condor poop did germinate still? Well, they weren't in the pond or coop. They were in the pack rat. You know, pack rats have these middens, these little tiny caves where they bring stuff and they store stuff.

57:29And they had bones in there and they had seeds in there. And so you can take the seeds and germinate them and see what the plants from that time were like. And this is not long enough for new species. That's cool. But it is long enough to see adaptation that changes in the environment. That's awesome. All right. Super fascinating. Should we send this off to Jean? We should send this off to Jane. All right, Jane, what do you think? Wow. Please thank Manuel for answering my question, which I'm stunned to hear is at the cutting edge of science. There were so many cool facts in this answer, like a seed is a whole plant.

58:07I believe Manuel called it an adult in itself. And they're just primed and ready to go, just waiting for the right resources to kick things off. but I am relieved that we're not reliant on muons. I didn't appreciate that commercial seed merchants prepared seeds so carefully but that begs the question. If some seeds, as Manuel suggested, need to pass through the gut of a bird or an animal before they germinate how on earth is this achieved commercially? Thank you once more for satisfying my thirst for more science knowledge. Hi, Kelly. Thanks for that interesting question from your richard. On the whole, this need for physical passage through an animal gut has been bred out of domestic planks.

59:00So when you buy seeds for flowers or vegetables for your garden, they largely don't need that kind of physical abrasion that they get by passing through the bird or the mammal intestinal tract. And that is one reason that many wild plant seeds have lower germination rates than domestic ones. The wild plant seeds are missing animal scarification that they may still require. One example where people on the east coast of the United States or Europe can see this is with a plant called wineberry. Wineberry is a European kind of raspberry that is very common as a wild plant, but has never been domesticated.

59:43Wineberry rates of germination are much lower than the germination rates of domestic raspberries. There are some seed sellers who use physical abrasion to increase germination or ache. You see this on the packet with the fancy word scarification. That usually means they just rolled the seeds around with some rocks to break up the seed coat a little bit. But of course, if any animals are used for scarification, it's likely goats. Because as you well know, people who raise goats are lovely, willing to try anything, and sometimes a little wacky.

1:00:55We'll be right back. a shining hill that exemplify and embody the Christian way of life. Stop right there. Is that normal? A podcast about what happens when a small town becomes the site of a social experiment. God need men to rule. Great. And decides to fight back. Do not use my hard work to sell your bull. They're not just opposing what's being planned for here. Our hometown is not a test tube. They feel like they're standing in opposition to an entire administration. Guess you didn't move in on a bunch of dumb hillbillies now, did you? Listen to Our Town on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.

1:02:07How did any of this get made? Why do we think that was a good idea? We're ready to talk about it. And we'll also be joined by the people who helped bring it all to life. Guest stars, collaborators, and friends, including director Jonathan Kreisel, the mayor himself, Kyle McLaughlin, legendary musician Amy Mann, and many more. Kyle is going for it here. You fully improvised, not just words, but a song. I thought he was going to write. I thought you were all going to write a song. I remember you thinking that. Listen to Podlandia. Ayo, rewatch on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.

1:02:44Hey, this is Hayes Davenport. And Sean Clements. We host the podcast Hollywood Handbook. Every episode, we're trying to help our guests improve their careers by mainly focusing on and how they can help us improve our careers. The show is famously super accessible, so you can easily jump into any of our 650 episodes and understand what's going on. We recommend some of our recent episodes with Ben Stiller. The definition of what is a movie has kind of changed anyway, too, right? What do you think it is now? It's images and words being spoken, captured by some sort of technology. Danny McBride. He loves Boba.

1:03:17Oh, that's fantastic. And you make it on, you make your own. That's great. I call him Tarot Reed. It's a good name. They're all named after cast members of American Pie. Yeah. I never looked up if she was in this, but I call him Leachie Sobieski. I don't think she was in American Pie, but I still like that. Haven't looked it up. She was prominent around the same time. Then Mary Steenburgen. Why are you guys talking to me? I'm worried. Why are you talking so down to me that you think I don't understand your little play game? I'm just really trying to set you up for success here. Listen to Hollywood Handbook on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.

1:04:00On Solita, we share the messy stories of traveling alone as a woman. Your Duolingo is not going to come back to you when a man is inside of you. Oh, no. I'm Julie Pinheiro, and I travel by myself because it's a rare space where I can say yes without asking anyone else first. I'm on a mission to reclaim the word solita, trading the pity for possibility. Every time I tried to be alone, I kept meeting people and they were like, you smiled at us. Not a lot of people smile around here. I can wait four hours for the next bus or this random dude is offering me a ride on his motorcycle. It's when you're alone that you're most receptive to the world as it is and not the lies you're sold about it.

1:04:47So whether you're a solo travel veteran or you're too nervous to book your first trip, I hope you listen to Solita on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.

1:05:11This last question comes to us from my favorite web cartoonist. Turns out I do know a good web cartoonist, and I'll change my tune and be nice here for a second. So, Zach, go ahead and ask your question about micropropagation. Hello, this is Zach Wienersmith. I'm a 90-year-old retiree from Japan, and I was just reading a book on horticulture, and I came across this idea of micropropagation, where somehow you use cells from plants to grow a bunch more plants. And I'm wondering, as are my friends here in Germany, exactly how that works. Thanks. Huge fan of the podcast. Good day, sir and madam. Zach is not just a web cartoonist.

1:06:00He's quite a gardener. I've been to the farm. I know he's like always involved in planting or growing something. Doesn't he have like a bunch of trees where he's like grafting this onto that? He hasn't started the grafting yet, but that he has planted a bunch of trees and he plans on doing grafting. And he he planted 60 pawpaw plots this year in the hope that he'll get to do some pawpaw grafting and and stuff in the coming years. And so are you queen of the animals and he's king of the plants? Is that how things divide over there? That's right. And I thought that made me superior. But Manuel is pointing out that the biomass is in Zach's favor.

1:06:35But anyway, yes, he's quite the gardener. He would say he doesn't know what he's doing, I think, but he's learning as he goes. Would he? No, I'm pretty darn sure he would. You would say that he would say that. All right, well, I'm sure he'll weigh in on his comment at the end. So, all right. What is micropropagation? So Manuel and I agreed that I was going to try to explain this first and that then he would jump in. Nice. So let's see how this goes. OK, so, you know, folks who have houseplants know that sometimes you can cut off a piece of the houseplant and like stick it in soil or stick it in water and you get a whole new plant.

1:07:08And so that is a way to get more plants quickly. But that's not fast enough if you want to be selling like thousands and thousands and thousands of a plant to people who, you know, there's a plant that's in great demand and you need to have a lot of them quickly. And so micropropagation involves essentially taking certain parts of the plant, sterilizing it so that you're getting rid of all of the bacteria, all of the fungus, et cetera. And then you put it in a little environment with hormones and other cues that the plant uses. And one of the things that you can do is create in these like little containers with hormones is callus, where you get a lot of undifferentiated plant cells so that they haven't become leaves, they haven't become roots.

1:07:51They're ready to become something eventually, but at the moment, they don't really know what their future holds. And so you get lots and lots of these cells, and then you can break them up gently and put them into different containers with different sets of hormones, and each one of those will become a new plant. And so you can essentially have this stage where you're growing up a bunch of cells in an environment. You separate those cells out. You give them different hormonal cues. And now you can get thousands, maybe even millions of these plants much more quickly. What have I gotten wrong so far, Manuel?

1:08:26No, I think you nailed it. I think I was very smart to ask you to do this first. Kelly, you're an excellent guest on Manuel's podcast here. Oh, good. Okay. He points up. I mean, let's go back to Daniel's potato there, right? It points up the fact that these cells throughout the plant are genetically identical. And it highlights one of the really interesting differences between plants and animals. It's a quantitative difference, not a qualitative one, which is that plant cells have a lot of flexibility compared to animal cells. And even though when a leaf develops, those cells that are formed by, you know, the cells are growing, they divide, the leaf gets bigger and bigger and bigger, and those cells all become leaf cells, they're not fixed to doing that the way a lot of animal cells are.

1:09:29If you can pull those cells out of the leaf environment, and that's what micropropagation is, they become equivalent functionally to stem cells in animals. That is, they can then become anything they want. And you can grow them up in the right balance of hormones and sugar. Remember, they need a food source. You can grow them up into a new plant. And that's micropropagation. And the reason it works so well with plants is that this, what's called de-differentiation, which is almost impossible with animal cells. Once you have a liver cell, it's almost impossible to have it become anything but another two more liver cells.

1:10:19On the other hand, a plant cell from a leaf, from a stem, can become that plant. Now, coming back to, oh, I forget who it was who asked, about germination. Jane. Jane, what you don't seem to be able to do in micropropagation is take that callus and have it develop directly into a seed. That doesn't happen. Huh. And it's not clear why that is so impossible. But of course, you could imagine that if you were trying to grow something where the seed is the crop, it would be lovely if you could do that, right? Skip that whole step of the apple tree, just go apple to apple to apple. And that doesn't work.

1:11:08We don't, we can't do that. We seem to be only able to propagate from a callus the leaf form of the plant. And nobody knows why that is. Interesting. I bet if you could figure that out, you'd make millions, maybe billions. Right, I would not be on your I would not be sitting at the University of Virginia Or on this podcast You would be the plant king No, I would still be on the podcast I'd definitely be on the podcast, but I wouldn't be a Yeah, wouldn't be a professor anymore I wouldn't be in the lab on a Friday On Friday before July 4th You know, if I made a billion dollars I would still be a physical professor Well It's easy to say that It was pretty easy to say that, you're right But I think it is, like, you know This is what I enjoy doing every day So can you, when you're going to make that callus, can you take cells from any part of the plant or are there some cell types that work better?

1:12:02Well, there are some cell types where it's easier. Okay. And a lot of that has to do with what kind of cell wall is around the cell. Another important way that plants are really different from animals is that plants and cells, in addition to having that membrane that we all have, also have a wall, a fairly rigid wall around them. So micropropagation, often you want to work with cell types that have the thinnest, most pliable, most easy to degrade cell walls. Because that's a whole side of micropropagation that's tricky and important. it turns out that cell walls are a challenge for the plant as well right because if you're going to divide and split you have to break open your cell wall and then reform it around the new cells and so plants have a whole really cool genetic system to essentially chemically degrade their cell wall just enough so it can split but they don't degrade the whole thing because then they'd have to rebuild the whole wall.

1:13:14And they'd spend all their time doing that. So in micropropagation, it tends not to get done on cells that have really heavy, thick cell walls, like the parts of wood that are really strong. Okay. Those tend not to be used for it. Right. That makes sense. And then is it safe to assume that when you finish doing micropropagation, you end up with plants that are genetically identical to the plants that you took the cells from? Yes, they are literally clones of them. Of course, if you do it for long enough, there can be some kind of small scale mutation that occurs along the way, but essentially they're genetically identical.

1:13:53I mean, the real challenge for micropropagation and why not everyone does it and why most people just cut off a leaf and stick it in is that one of the very first things you said was really important comes back to the microbes. that you have to do this in a super sterile environment because everything you do when you are doing the micropropagation to help the plants grow will help the microbes grow also. And what you'll end up doing is propagating an enormous microbial colony instead of a plant if you don't do it entirely sterile. And microbes and plants have this incredibly tight relationship with one another where you really don't, I mean, your wife is correct again, you don't have plants in nature ever without microbial infections.

1:14:53That's right. Ever. They're everywhere. That is the challenge in micropropagation. Not so much the propagation techniques themselves, but getting the environment clean enough so that you can do it without micropropagating microbes simultaneously. And is this part, so I remember at the end of micropropagation, there's a stage where you have to harden the plants back up again because they've been in this like perfect, sterile, delicate environment. Is part of that process like reintroducing them to the like organisms that they kind of need? Or is it just trying to toughen them up because they've been coddled?

1:15:31It's interesting. I think probably one of the things that you're indirectly doing is toughening them up for the microbes. Okay. But usually that hardening is more focused on the physical environment and the chemical environment that they're in rather than the microbial. You just, you stop being so, so anally retentive about sterility and you start letting them struggle a little bit more. And wherever there is carbon, there are microbes. And so the microbes get there. Yay, microbes. So some of the benefits of micropropagation are that you can quickly get a whole bunch of clones of some plant that you really want.

1:16:17And if you specifically are trying to make a plant that you know tends to have a disease, doing it in this sterile environment means that like when you send this plant, for example, to another country, you can be pretty darn sure you're not going to be sending that disease to another country where it can then go and infect other plants. And so sterility is a feature, even if it makes things complicated. Does that sound fair, Manuel? Yeah. I mean, I'm not sure how much that sterile environment is important for, say, international shipping or interstate transport. I think it's mostly important for getting plants who are not only genetically uniform, but have grown up in a really similar environment.

1:17:02If you have some who have been infected and some who have not been infected, they're going to be different plants. I've only been involved in one major study where we used micropropagation. And that was with we wanted the exact same genotype of a kind of tomato that we were working on. And we needed thousands of them to grow. And so when you're growing 7 ,500 tomatoes, you don't garden anymore for a few years. But we were able to do that. That was the main goal was to get these identical plants so that we would know that any differences we saw were due to the perturbations we were exerting on the plants, not to differences that they came with.

1:17:46I was listening to the In Defense of Plants podcast, and he was interviewing someone who does orchid conservation. and I hear that this is also like a helpful technique and some conservation programs for plants as well where you want to grow up a lot of them sort of as fast as you can and maintain a bunch of genotypes. And so have you heard about this being used in conservation for plants as well? So it's pretty famous for orchids. Okay. And the reason for that is that one, people love orchids. Two, linked to one, a lot of orchids are quite rare. And three, because orchids have such intricate, complicated pollination systems, usually requiring a specific species of bee to pollinate that orchid, it's really hard to get orchids, many species, to get them to make seeds.

1:18:40Because your orchid from South America that you're growing in Albemarle County, Virginia, may not have the right bee. And so your seed production will be low. So you can use micropropagation in order to get many others of your orchid. Now, you're only getting that genotype of that species of orchid, but it's better than nothing. So, yeah, in orchids, it's been hugely important. Anything that's really difficult to get pollinated, micropropagation would be good for. All right. Let's send this answer to Zach and see if we have sated his appetite for knowledge about micropropagation. See if he's still awake after.

1:19:20I'll hail the king of plants. Oh, no, I think the queen of the animals is the one that should be hailed. Hi, this is Zach Wienersmith. I am a 95-year-old retiree here in Geneva, and I just wanted to say I appreciated the thorough response from Manuel and Kelly on The Kelly Show. Thanks very much for answering the question, and au revoir. Okay, and that's our episode. Thanks, everybody. If you have a question for us, you can send it to questions at danielandkelly.org and some of the questions make it on the show and the ones that really stump us, we bring our friends on to answer for us. So thanks for joining us today, Manuel.

1:20:05All right, take care.

1:20:13Thanks, everybody, for listening. Please go and do us a favor and rate the show on whatever podcast app you're using. It really helps people find us. Daniel and Kelly's Extraordinary Universe is edited by the amazing Matt Kesselman. He really is a wizard. You can also find us online on Blue Sky, Instagram, and X, D &K Universe. Come engage with us. You can email us at questions at danielandkelly.org. We really do want to hear from you. And you can find our website, www.danielandkelly.org, where you'll also find an invitation to join our Discord where everybody comes and talks about the amazing universe.

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